DESC:A GRID TIED INVERTER SYSTEM AND A METHOD OF OPERATION THEREOF

CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims priority from Indian Provisional Patent Application No. 202421049561 filed on 28/06/2024, the entirety of which is incorporated herein by a reference.
TECHNICAL FIELD
Generally, the present disclosure relates to inverter systems. Particularly, the present disclosure relates to a grid tied inverter system and a method of operation thereof.
BACKGROUND
In power conversion systems, inverters play a critical role in converting Direct Current (DC) to Alternating Current (AC) for use in various applications such as electric vehicles, renewable energy systems, and industrial drives. The performance and efficiency of the inverters depend on the switching devices (such as IGBTs or MOSFETs). Conventionally, gate signal drivers are employed to interface between the control logic and power switches to match the power output of the AC grid network with a DC power source.
Traditionally, interfacing a DC power source with an AC power network employs Proportional-Integral (PI)-based digital control to control grid-tied inverters and minimize steady-state error. Further, PI controller or similar feedback mechanisms are used to adjust the duty cycles of the inverter switches in order to maintain output voltage or current within the desired range. The generated gate signals are directly derived from a reference current signal, using linear gain or lookup-based approaches. Furthermore, traditional control schemes rely on the switching mechanism to adjust the inverter control without a dynamic adjustment of the signals. Additionally, a number of tuning parameters are employed to interface the DC power source with an AC power network.
However, there are certain problems associated with the existing or above-mentioned mechanism for interfacing a Direct Current (DC) power source with an Alternating Current (AC) power network. For instance, the traditional controllers lack error-based tuning to regulate the control mechanism and therefore cause non-uniform control action towards transient and steady state conditions. Further, due to substantial reliance on the switching, extensive switching for the fundamental cycle results in stress on the switch and increased switching losses, which leads to reduced efficiency of the inverter. Additionally, many controllers are implemented in the dq frame of reference. However, the design and computational complexity of implementing the controller in the dq frame is very high due to separate controller parameter tuning and an increased number of variables and computations.
Therefore, there exists a need for a mechanism for interfacing a Direct Current (DC) power source with an Alternating Current (AC) power network that is efficient, accurate, and overcomes one or more problems as mentioned above.
SUMMARY
An object of the present disclosure is to provide a power conversion system for interfacing a Direct Current (DC) power source with an Alternating Current (AC) power network.
Another object of the present disclosure is to provide a method of interfacing a Direct Current (DC) power source with an Alternating Current (AC) power network.
Yet another object of the present disclosure is to provide an improved power conversion system capable of dynamically and accurately controlling inverter switching operations based on real-time current error regulation.
In accordance with an aspect of the present disclosure, there is provided a power conversion system for interfacing a Direct Current (DC) power source with an Alternating Current (AC) power network, the system comprises:
- an inverter electrically coupled to the DC power source and the AC power network;
- a sensing unit communicably coupled to the AC power network; and
- a control unit communicably coupled to the inverter and the sensing unit,
wherein the control unit is configured to control the inverter based on at least one input received from the sensing unit and the AC power network.
The power conversion system for interfacing a Direct Current (DC) power source with an Alternating Current (AC) power network, as described in the present disclosure, is advantageous in terms of efficient inverter control, precise synchronization, and seamless power transfer. Specifically, the generation of current error signals and the application of a sliding mode control framework with convergence rules enable robust dynamic tracking, reduce external disturbances, non-linearities, or grid fluctuations. Further, the presence of a resonant block enhances harmonic rejection and stability, thereby reducing total harmonic distortion (THD) and improving power quality. Therefore, the invention is particularly suited for renewable energy interfaces requiring high precision, reliability, and dynamic control capability.
In accordance with another aspect of the present disclosure, there is provided a method of interfacing a Direct Current (DC) power source with an Alternating Current (AC) power network, the method comprises:
- determining at least one phase angle of the output voltage signal via a phase detection unit;
- comparing at least one reference current signal with a magnitude of output current signal of the AC power network via the current regulation unit;
- computing at least one current error signal based on the comparison via the current regulation unit;
- generating at least one sliding surface based on the computed at least one current error signal via the current regulation unit; and
- generating at least one gate signal to control the switching operation of an inverter, via at least one gate driver.
Additional aspects, advantages, features, and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments constructed in conjunction with the appended claims that follow.
It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
Figures 1 and 2 illustrate a system for interfacing a Direct Current (DC) power source with an Alternating Current (AC) power network, in accordance with different embodiments of the present disclosure.
Figure 3 illustrates a flow chart of a method of interfacing a Direct Current (DC) power source with an Alternating Current (AC) power network, in accordance with another embodiment of the present disclosure.
In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.
DETAILED DESCRIPTION
The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.
As used herein, the terms “power conversion system”, “conversion system” refer to an electrical arrangement designed to convert power from one form to another such as, but not limited to, from direct current (DC) to alternating current (AC), or vice versa by means of managing voltage, current, frequency, and waveform parameters according to the application requirements. The system is key in a wide range of applications, including renewable energy systems (such as, but not limited to, solar PV and wind turbines), electric vehicles, grid-tied inverters, motor drives, and uninterruptible power supplies (UPS). The power conversion system consists of one or more converters (such as, but not limited to, inverters, rectifiers, or DC-DC converters), control circuitry, filtering components, and sometimes energy storage elements, altogether coordinated to ensure efficient and reliable energy transfer between sources and loads. The are various types of power conversion systems based on the input-output combinations: AC–DC (rectifiers), which convert AC power into DC; DC–AC (inverters), which convert DC power into grid-compatible AC; DC–DC converters, used for voltage level adjustment within DC systems; and AC–AC converters, which modify frequency or voltage levels in AC circuits. The procedure of power conversion generally involves power semiconductor switches (such as IGBTs, MOSFETs) that are controlled by digital or analog control units. The control units use techniques such as pulse-width modulation (PWM), phase-locked loops (PLLs), and feedback loops (voltage or current control) to regulate output characteristics based on real-time measurements and desired operating points.
As used herein, the terms “Direct Current (DC) power source”, “DC power source”, “DC power source”, and “DC source” are used interchangeably and refer to any energy source that supplies electrical power in the form of unidirectional (non-alternating) voltage and current. The DC power sources deliver constant or controlled-variable voltage and are used in solar photovoltaic (PV) modules, batteries, fuel cells, rectified AC sources, and supercapacitors. In power conversion systems, the DC power sources serve as the input to inverters or DC-DC converters, which regulate the energy for use in alternating current (AC) systems (such as the grid), DC loads, or for storage. The defining characteristic of a DC source is the lack of zero-crossing voltage or frequency variation, ensuring stable and predictable power conversion. The types of DC power sources include Natural sources, such as, but not limited to, solar PV panels, which produce variable DC depending on sunlight; electrochemical sources such as batteries and fuel cells, which provide stored or chemically generated DC; and electronic rectification sources, which converts AC to DC using rectifiers. The approach of integrating a DC source into a power conversion system involves electrical interfacing (such as, but not limited to, DC link capacitors), voltage regulation circuits, and feedback control mechanisms. The integration approach further employs sensors to monitor DC voltage and current, with control algorithms adjusting converter switching to ensure appropriate voltage levels, protect the system from overcurrent, and manage power flow dynamically between the source and load.
As used herein, the terms “Alternating Current (AC) power network”, “AC power network”, “AC grid” and “grid” are used interchangeably and refer to an arrangement that distributes and transmits electrical power in the form of alternating voltage and current, usually at standardized frequencies such as 50 Hz or 60 Hz. Specifically, the AC network also represents a local utility grid, a microgrid, or an internal facility distribution system. In power conversion applications, the AC power network serves either as the receiving end (in the case of DC-to-AC conversion for grid injection) or as the supply source (in AC-to-DC rectification arrangements). The AC network is characterized by sinusoidal waveforms, phase relationships, and parameters such as voltage levels, frequency, and impedance, which are matched or synchronized by the power conversion system to ensure stable and efficient operation. The types of AC power networks include Single-phase arrangements, commonly used in residential and light commercial setups, and Three-phase arrangements, prevalent in industrial, commercial, and grid-scale infrastructures due to the greater power-handling capacity and efficiency. The procedure of interfacing with the AC power network in a power conversion system involves the use of synchronized inverters, phase-locked loops (PLLs) for frequency and phase tracking, and feedback control arrangements to regulate power flow, ensure sinusoidal current injection, and comply with grid codes. The inverter generates AC waveforms that are synchronized in frequency, phase, and amplitude with the AC network, and additional filtering and protection circuits are employed to manage harmonics, fault conditions, and voltage transients.
As used herein, the terms “inverter”, “power inverter”, and “converter” are used interchangeably and refer to an electrical device that converts Direct Current (DC) into Alternating Current (AC). The inverter is a core component in devices such as solar photovoltaic setups, battery storage systems, and electric vehicles, in arrangements requiring DC energy from sources such as batteries or solar panels that need to be converted into AC for consumption or distribution. The inverter typically consists of semiconductor switching elements (such as, but not limited to, IGBTs or MOSFETs), a control unit for generating switching signals, and filtering components to structure the output waveform. The inverters ensure that the generated AC matches required characteristics such as voltage level, frequency, and phase synchronization with the utility grid or load. The types of inverters include single-phase and three-phase inverters, depending on the AC output requirement; Voltage-Source Inverters (VSI) and Current-Source Inverters (CSI), classified based on the input and control approach; and Grid-tied (synchronized) and standalone inverters. The procedure of operation involves pulse-width modulation (PWM), or other switching strategies controlled by a digital control unit, which generates the gate pulses for the semiconductor switches. The control algorithm further includes phase-locked loop (PLL) synchronization, current and voltage regulation loops, and fault protection mechanisms. Furthermore, filters are generally added at the output to smooth the waveform and limit harmonic distortion, ensuring the AC output meets quality and safety standards.
As used herein, the terms “sensing unit” and “sensor unit” are used interchangeably and refer to the component or set of devices used for measuring key electrical parameters such as voltage, current, frequency, or phase angle at various points within the system. The sensing unit provides real-time feedback essential for control, monitoring, protection, and optimization of the power conversion process. The sensing unit is interfaced with the control unit or digital signal processor, the sensing unit ensures that the system responds dynamically to changes in load, grid conditions, or source characteristics. Further, the sensing unit plays a vital role in maintaining system stability, enforcing safety limits, and ensuring compliance with performance standards. The types of sensing units include voltage sensors (such as, but not limited to resistive dividers or isolation amplifiers), current sensors (such as, but not limited to Hall-effect sensors, current transformers, or shunt resistors), and combined measurement modules that detect multiple parameters such as power, power factor, or frequency. The technique of sensing involves signal acquisition through transducers, followed by signal conditioning (filtering, amplification, isolation), and finally conversion to a digital format via ADCs (Analog-to-Digital Converters). The conditioned signals are further processed by the control unit to execute real-time decisions such as adjusting PWM duty cycles, enabling protection mechanisms, or synchronizing with an AC network. The proper placement and calibration of the sensing units are critical to ensure measurement accuracy and system reliability.
As used herein, the terms “control unit”, “control module”, “controller”, and “processor” are used interchangeably and refer to a central processing and decision-making component for regulating the operation of power electronic converters such as, but not limited to, inverters, rectifiers, and DC-DC converters. The primary role of the control unit is to manage the real-time behavior of the system to meet desired performance objectives such as voltage regulation, current control, power factor correction, synchronization with AC networks, and protection against faults. Further, the control unit comprises a microcontroller, digital signal processor (DSP), or FPGA, programmed with control algorithms that interpret feedback signals and generate corresponding gating signals for the power switches. The control unit acts as the “brain” of the system, interpreting sensed data and implementing control strategies to optimize energy conversion, ensure safety, and maintain power quality. The types of control units vary based on complexity and function. Various types of controllers include open-loop controllers, which operate without feedback and are used in simple or non-critical systems; closed-loop controllers, which use real-time feedback (voltage, current) to regulate outputs; and advanced digital controllers incorporating Phase-Locked Loops (PLLs), Maximum Power Point Tracking (MPPT), or vector control for dynamic grid or motor applications. The approach of controlling follows a sensing-decision-actuation loop. Specifically, the measured electrical signals are first acquired by the sensing unit and digitized. Further, the control algorithm, such as but not limited to PI, PID, or model predictive control, is applied and compares the inputs with set reference values and calculates the required control actions. Furthermore, the control actions are translated into gating pulses using modulation techniques such as PWM (Pulse Width Modulation), which are fed to the power semiconductor switches, thus adjusting the energy conversion process in real time.
As used herein, the terms “gate signal driver”, “gate driver,” and “gate signal” are used interchangeably and refer to an intermediate circuit or module that interfaces between the control unit and the power semiconductor switches (such as IGBTs or MOSFETs) within inverters, converters, or rectifiers. The primary function of the gate signal driver is to amplify, condition, and safely deliver gate pulses from the control unit to the switches, ensuring proper turn-on and turn-off operation. Further, as the power switches operate at high voltages and fast switching frequencies, the gate driver provides sufficient voltage and current to overcome the gate capacitance and minimize switching losses. Additionally, gate drivers include features such as electrical isolation (via optocouplers or transformers), dead-time control, under-voltage lockout, and fault feedback to protect both the control and power stages. Furthermore, the types of gate signal drivers include non-isolated drivers, used in low-power or low-voltage applications; isolated drivers, which use galvanic isolation techniques for high-voltage systems; and smart gate drivers, which incorporate diagnostics, protection logic, and configurable parameters for advanced control. The operation of the gate signal driver involves receiving PWM or logic-level signals from the control unit, conditioning the signals (adjusting voltage level and slew rate), and supplying the signals to the gate terminals of the switches. The proper timing and synchronization across phases are essential to prevent shoot-through or cross-conduction. The gate signal driver thereby ensures robust, reliable, and efficient operation of the power conversion system under varying load and grid conditions.
As used herein, the terms “current regulation unit” and “regulation unit” are used interchangeably and refer to a functional component or algorithmic block designed to control and maintain the output or input current of the converter within desired limits. The current regulation unit ensures stable current flow in accordance with system demands, reference values, or grid requirements while protecting components from overcurrent conditions. The regulation unit is critical in applications such as grid-tied inverters, motor drives, and battery charging systems, as precise current shaping directly affects system efficiency, power quality, and safety. The current regulation unit typically operates in a closed-loop manner, comparing real-time sensed current values with reference currents and adjusting switching signals or voltage commands accordingly to minimize the error. The types of current regulation units include analog current regulators, which use hardware-based op-amp circuits for fast response in simpler systems; digital current regulators, implemented in microcontrollers or DSPs, enabling programmable control with greater flexibility; and predictive or adaptive current controllers, which dynamically adjust control parameters based on operating conditions for enhanced performance. The technique of current regulation involves measuring the actual current (using sensors such as hall-effect or shunt resistors), calculating the error with respect to a reference current, processing the error through a control algorithm (such as PI, PID, or resonant controller), and generating appropriate modulation signals. The signals ultimately influence the gate driver outputs and switching patterns of the inverter or converter, thereby adjusting the voltage or duty cycle to regulate the current effectively and ensure compliance with performance or safety requirements.
As used herein, the terms “phase detection unit” and “PDU” are used interchangeably and refer to a subsystem or algorithm that determines the instantaneous phase angle of an incoming AC signal, usually from an external power source or grid. The accurate phase detection is essential for synchronizing power conversion devices such as grid-tied inverters with the AC network to ensure proper current injection, power flow control, and system stability. The PDU is fundamental in implementing synchronization strategies such as Phase-Locked Loop (PLL), allowing the converter to match the phase, frequency, and voltage of the grid, thereby avoiding issues such as circulating currents, phase mismatch, or unintentional islanding. The types of phase detection units include: zero-crossing detectors, which provide basic phase detection by monitoring zero-voltage crossings of sinusoidal waveforms; synchronous Reference Frame PLLs (SRF-PLLs), which transform three-phase signals into a rotating reference frame to extract the phase angle; enhanced PLLs, such as decoupled or adaptive PLLs, used for distorted or unbalanced grids. The technique of phase detection involves sampling AC voltage waveforms using sensors, filtering the signals to reduce noise, and running the signals through the PLL or another phase estimation algorithm. The phase detection unit outputs a continuous estimate of the grid or AC signal’s phase angle, which is used to generate synchronized control references (unit vectors or sinusoidal reference currents) to ensure that the inverter or converter operates in-phase with the grid for safe and efficient energy transfer.
As used herein, the terms “resonant block”, “resonant circuit”, and “resonant module” refer to a specialized signal processing or control component designed to amplify or selectively respond to signals at a particular frequency, typically the fundamental frequency of the AC power network (50?Hz or 60?Hz). The resonant block is used in current or voltage control loops to enhance tracking performance and reject disturbances outside the fundamental frequency range. The resonant blocks are fundamental in harmonic compensation, grid synchronization, and precise control of sinusoidal currents. The resonant block is implemented using analog circuitry or digitally via software algorithms in a control processor, and is effective in improving the dynamic response and steady-state accuracy of a controller. The types of resonant blocks include proportional-Resonant (PR) controllers, which offer high gain at the fundamental frequency and zero steady-state error for sinusoidal references; multi-resonant controllers, which incorporate multiple resonant terms to handle harmonics (3rd, 5th, 7th); and notch or bandpass filter-based resonant units, which suppress or amplify narrow frequency bands. The procedure of operation involves feeding an error signal, such as the difference between a reference and an actual current, into the resonant block. Subsequently, the block processes the signal to isolate and enhance components at the desired frequency, producing an output that is scaled by a gain factor and used in the generation of control signals. The generation of the control signals enables the system to respond strongly to deviations at the nominal frequency with rejecting noise and harmonics outside the targeted band.
As used herein, the terms “voltage sensor” and “voltage detector” are used interchangeably and refer to an electronic device used to detect, measure, and monitor the voltage level of an electrical signal or system. The voltage sensor converts the voltage value into a readable signal (analog or digital) for control, monitoring, or protection purposes. The voltage sensors are critical in applications such as power supplies, inverters, converters, and energy management systems, as accurate voltage feedback is essential for proper operation and efficiency. The two main types of voltage sensors are: analog and digital. The analog voltage sensors output a continuous signal that is proportional to the voltage level, and digital sensors convert the measured voltage into a digital signal suitable for microcontroller-based systems. Based on the sensing approach, the voltage sensors are also classified into non-contact (capacitive or optical) and contact-type (resistive or voltage divider). The most common approach for sensing voltage in power systems involves using a voltage divider circuit, as resistors reduce the voltage to a level suitable for measurement. The signal is further fed into an analog-to-digital converter (ADC) for processing by a control system. Further, the advanced sensors also use isolation techniques, such as transformers or opto-isolators, to protect sensitive components and ensure safe operation in high-voltage environments.
As used herein, the terms “current sensor” and “current detector” are used interchangeably and refer to a device used to detect and measure the flow of electric current through a conductor, converting the current into a signal (analog or digital) that is read and processed by the control unit. The accurate current sensing is essential for monitoring load conditions, protecting circuits from overcurrent, and enabling precise control in devices such as inverters, converters, motor drives, and power supplies. The types of current sensors include shunt-based, Hall-effect, Rogowski coils, and current transformers. The shunt resistors are low-cost sensors that measure the voltage drop across a known resistance to calculate current. The Hall-effect sensors detect the magnetic field generated by current flow and are commonly used for isolated current sensing. The Rogowski coils are used for measuring high-frequency or AC currents without contact, and current transformers (CTs) are typically employed for high-current AC measurement in industrial applications.
As used herein, the terms “phase angle” and “phase” are used interchangeably and refer to the angular difference, measured in degrees or radians, between the voltage waveform and the current waveform in an AC electrical circuit. The phase angle is a key parameter that indicates the nature of the load (resistive, inductive, or capacitive) and is directly related to the power factor, which affects the efficiency of power delivery. The phase angle of zero degrees indicates a purely resistive load (voltage and current in phase), a non-zero angle implies reactive components, leading to reduced power transfer efficiency. The monitoring and controlling the phase angle is crucial in systems such as inverters, converters, and grid-tied renewable energy sources to ensure synchronized and stable operation. The two main types of phase angle are leading and lagging. The leading phase angle occurs when the current waveform leads the voltage, typically seen in capacitive loads. Conversely, a lagging phase angle occurs when the current lags behind the voltage, common in inductive loads. The method of measuring phase angle involves comparing the zero-crossings or time delay between voltage and current waveforms using digital signal processors (DSPs) or microcontrollers. Instruments such as phase angle meters, oscilloscopes, or software-based algorithms in power electronics controllers are used for measurement purposes. An accurate phase angle measurement enables effective control strategies such as power factor correction, load balancing, and synchronization in power conversion systems.
As used herein, the terms “current unit vector” and “unit vector” are used interchangeably and refer to a normalized vector representation of the current waveform used in vector control and synchronous reference frame theory. The current unit vector represents the direction of the current in a rotating coordinate system (d-q frame) and is crucial for accurately controlling AC machines (such as motors) and managing active and reactive power in grid-tied inverters. Further, by converting the three-phase current into an equivalent unit vector form, control systems are able to effectively regulate the magnitude and phase of current with respect to the voltage, enabling precise torque control, efficient power transfer, and synchronization with the grid. The types of current unit vectors are usually categorized based on the alignment with the rotating reference frame: d-axis unit vector (aligned with the active power component) and q-axis unit vector (aligned with the reactive power component). The approach to derive the current unit vector involves measuring the three-phase currents (I(a), I(b), I(c)), transforming the current into two-phase orthogonal components using Clarke and Park transformations, and later normalizing the resulting vector. The normalized form (unit vector) is used in control algorithms such as field-oriented control (FOC) or direct power control (DPC) to manage power flow and improve dynamic response. The unit vector is essential for achieving decoupled control of torque and flux in motors and ensuring phase synchronization in inverter-based power systems.
As used herein, the terms “reference current signal” and “reference signal” are used interchangeably and refer to a target or desired current waveform generated by a control algorithm to guide the actual current flowing through the power conversion system. The reference current signal represents the ideal operating condition for current in terms of magnitude, phase, and waveform shape, based on the conversion goals such as power factor correction, load compensation, or harmonic elimination. The reference current signal is critical in closed-loop control systems, as the reference current signal is compared with the actual current to produce an error signal that drives corrective actions in converters, inverters, or active filters. The different types of reference current signals are based on the control objective: sinusoidal reference signals for linear loads, non-sinusoidal signals for compensating nonlinear or harmonic-rich loads, and instantaneous power theory-based signals for dynamic power compensation. The procedure to generate a reference current signal usually involves measuring system parameters (such as voltage, load current, or power), applying transformation techniques ( Clarke, Park, or d-q transformations), and using mathematical models such as instantaneous reactive power theory or synchronous reference frame theory. The techniques help to extract or synthesize the ideal current waveform needed to achieve efficient and stable power conversion.
As used herein, the terms “ideal AC network input power” and “ideal AC power” are used interchangeably and refer to the theoretical or expected power drawn from an AC source under perfect conditions, typically assuming purely sinusoidal voltage and current waveforms that are perfectly in phase. The ideal power is equivalent to the maximum real (active) power that is transferred to the load without losses due to harmonics, reactive components, or inefficiencies in the system. The ideal AC power serves as a benchmark for evaluating the performance and efficiency of converters, inverters, and other power electronic systems by comparing actual input power against this ideal standard. The types of ideal AC network input power are primarily associated with single-phase and three-phase systems, depending on the configuration. In both cases, the ideal input power is calculated as the product of the root mean square (RMS) values of voltage and current, multiplied by the cosine of the phase angle.
As used herein, the terms “current error signal” and “error signal ” are used interchangeably and refer to the difference between the reference current signal (the desired or target current) and the actual current flowing through the power conversion system. The error signal is a key part of closed-loop control systems used in inverters, converters, and motor drives. The current error signal indicates the system deviation from the intended operation and is used by controllers such as proportional-integral (PI), proportional-resonant (PR), or hysteresis controllers to generate appropriate switching signals or modulation indices to correct the error. Further, by minimizing the current error, the system maintains stability, efficiency, and precise power control. The different types of current error signals depending on the control strategy are instantaneous current error (used in time-domain control like hysteresis control), average or RMS current error (used in steady-state optimization), and frequency-domain error signals (used in harmonic control or predictive methods). The technique to obtain the current error signal involves real-time measurement of the output or load current using sensors, generating a reference current through control algorithms based on system objectives, and then subtracting the actual current from the reference. The error is continuously fed into a controller that adjusts the power converter's operation, such as modifying pulse-width modulation (PWM) or switching patterns to drive the error towards zero and ensure the system behaves as intended.
As used herein, the terms “sliding surface” and “surface” are used interchangeably and refer to a mathematical construct used in Sliding Mode Control (SMC) to guide the system's states toward a desired trajectory with minimal model uncertainties. The sliding surface defines a hyperplane in the state-space with the dynamic behavior of the controlled system exhibiting desired properties, such as robustness and fast convergence. Specifically, as the system state reaches the sliding surface, the system "slides" along the surface toward equilibrium. The sliding surface is designed in various forms depending on control objectives, such as linear sliding surfaces are defined using linear combinations of state variables for first-order or second-order systems; nonlinear sliding surfaces are applied in complex systems to enhance performance in terms of tracking and stability. The technique of employing a sliding surface in a power conversion system involves selecting a control objective, such as voltage regulation or current tracking. The next step involves defining a sliding surface representing the state vector of the system. The control law is constructed to force the system states toward this surface and maintain sliding motion once on it. This usually involves a discontinuous control input, such as a sign or saturation function, which compensates for system uncertainties and external disturbances. The design must ensure reachability (ensuring system trajectories reach the surface in finite time) and stability (ensuring motion along the surface leads to the desired state), often verified using Lyapunov-based analysis.
As used herein, the terms “convergence rule” and “convergence” are used interchangeably and refer to a set of criteria that ensure the system's output or internal state variables move toward and reach a desired target or equilibrium point. The concept of convergence is critical in power conversion systems using adaptive, sliding mode, or model predictive control with precise tracking and system stability. The convergence rules are used to ensure that errors in voltage, current, or other control objectives diminish over time. The types of convergence rules include exponential convergence, in which the error decreases at a rate proportional to the magnitude; finite-time convergence, in which the system reaches the desired state within a predetermined time; and asymptotic convergence, in which the state approaches the target value gradually. Specifically, to apply a convergence rule in a power conversion system, an error function is computed that represents the deviation of the system from the desired behavior. Based on the desired convergence type, a suitable control law is derived, often using tools such as Lyapunov functions, a reaching law to ensure stability and convergence. For instance, in sliding mode control, the convergence rule involves designing a sliding surface and a discontinuous control input that forces the error trajectory to intersect and remain on the surface. In model predictive or adaptive control, convergence is ensured by continuously updating control actions based on predictions and parameter estimates. The above-mentioned approach ensures robustness, stability, and compliance with physical system constraints such as switching frequency, voltage limits, and thermal behavior.
As used herein, the terms “command signal” and “trigger signal ” are used interchangeably and refer to an input control signal that specifies the desired operating condition or output of the system. The command signal serves as the target or setpoint for the control loop, guiding the converter or inverter to achieve specific objectives such as output voltage regulation, current control, torque control in motor drives, or power flow in grid-tied systems. The command signals are generated based on user input, system requirements, or higher-level control strategies and are used to direct the behavior of power electronic devices through modulation techniques such as PWM (Pulse Width Modulation). The types of command signals include voltage command signals, current command signals, torque or speed commands (in motor control systems), and power reference signals (in grid-connected or renewable energy systems). The means of generating a command signal depends on the application; for instance, a voltage command is set by a voltage reference in a DC-DC converter, and a current command comes from a power-balancing algorithm in an inverter. The signals are processed through control algorithms, which compare them to measured feedback values, generate error signals, and adjust switching patterns to minimize deviation from the desired output. The accurate generation and tracking of command signals are critical for efficient, stable, and responsive performance in modern power conversion systems.
As used herein, the terms “gate signal” and “gate pulse” are used interchangeably and refer to a control signal used to trigger the switching elements of power electronic devices such as transistors, thyristors, or IGBTs (Insulated Gate Bipolar Transistors). The gate signals are critical in determining the on/off switching behavior of the devices, thus regulating the flow of electrical power within the system. The gate signals are generated by the control circuitry and are usually synchronized with modulation techniques, such as Pulse Width Modulation (PWM) or other control schemes, to achieve the desired output characteristics, such as voltage, current, or frequency regulation. The proper generation and timing of gate signals are essential for the efficient operation of converters, inverters, and motor drives. The types of gate signals are classified based on the switching method PWM gate signals (for controlling the duration of the switch’s on-state to regulate power), on/off gate signals (used in simpler switching devices like relays or some types of rectifiers), and pulsed or alternating gate signals (for devices that require more complex control such as H-bridge inverters). The procedure of generating gate signals involves the use of control algorithms and modulation techniques, as a digital signal processor (DSP) or microcontroller determines the timing and duty cycle of the gate signal based on system parameters (input voltage, load current, or output requirements). The gate signals are fed to gate drivers, which provide the necessary voltage and current to switch the power devices effectively. Further, the gate signal integrity is crucial for minimizing switching losses, reducing electromagnetic interference (EMI), and ensuring reliable system performance.
In accordance with an aspect of the present disclosure, there is provided a power conversion system for interfacing a Direct Current (DC) power source with an Alternating Current (AC) power network, the system comprises:
- an inverter electrically coupled to the DC power source and the AC power network;
- a sensing unit communicably coupled to the AC power network; and
- a control unit communicably coupled to the inverter and the sensing unit,
wherein the control unit is configured to control the inverter based on at least one input received from the sensing unit and the AC power network.
Referring to figure 1, in accordance with an embodiment, there is described a power conversion system 100 for interfacing a Direct Current (DC) power source 102 with an Alternating Current (AC) power network 104. The system 100 comprises an inverter 106 electrically coupled to the DC power source 102 and the AC power network 104; a sensing unit 108 communicably coupled to the AC power network 104; and a control unit 110 communicably coupled to the inverter 106 and the sensing unit 108. Further, control unit 110 is configured to control the inverter 106 based on at least one input received from the sensing unit 108 and the AC power network 104.
The present power conversion system 100 is designed to efficiently interface a Direct Current (DC) power source 102 with an Alternating Current (AC) power network 104. The system 100 comprises the inverter 106 that is electrically coupled to both the DC power source 102 and the AC network 105. The inverter's 106 primary function is to convert the DC voltage from the DC source 102 into a regulated AC output, which is supplied to the AC power network 104. The inverter 106 operates based on the voltage, current, and phase requirements of the AC grid 104, thereby ensuring that the DC-to-AC conversion is synchronized with the AC grid's parameters. The sensing unit 108, communicably coupled with the AC power network 104, continuously monitors and measures the real-time electrical characteristics of the AC network 104. The measuring includes monitoring the output voltage, current, frequency, and phase angle of the AC power network 104, providing essential feedback to ensure that the inverter's 106 output aligns with the network's requirements. The control unit 110 is responsible for processing the data received from the sensing unit 108 and controlling the inverter's 106 operation through the gate signal driver 118. The control unit 110 comprises a combination of current regulation, phase detection, and feedback mechanisms to ensure optimal synchronization between the inverter's output and the AC grid 104. Based on the input from the sensing unit 108, the control unit 110 generates the required gate signals that are fed to the inverter 106. The gate signals are generated dynamically in real-time to ensure that the inverter output is maintained in phase with the grid voltage and follows the desired current profile. The real-time feedback from the sensing unit 108 allows the control unit 110 to adapt the inverter's 106 operation to fluctuations in the AC grid’s voltage and current, ensuring that the inverter’s output remains stable and efficient. The use of gate signal drivers 118 ensures that the inverter’s switching elements operate at optimal times, minimizing switching losses and improving overall system efficiency. The system's 100 ability to automatically adjust to the changing conditions of the grid ensures that the AC power injected into the network is clean, stable, and in compliance with grid standards, reducing harmonics and improving the power quality.
Referring to figure 2, in accordance with an embodiment, there is described a power conversion system 100 for interfacing a Direct Current (DC) power source 102 with an Alternating Current (AC) power network 104. The system 100 comprises an inverter 106 electrically coupled to the DC power source 102 and the AC power network 104; a sensing unit 108 communicably coupled to the AC power network 104; and a control unit 110 communicably coupled to the inverter 106 and the sensing unit 108. Further, control unit 110 is configured to control the inverter 106 based on at least one input received from the sensing unit 108 and the AC power network 104. The control unit 110 comprises a phase detection unit 112 to communicably couple the control unit 110 to the sensing unit 108; a current regulation unit 114 communicably coupled with the phase detection unit 112; a resonant block 116 communicably coupled with the current regulation unit 114; and at least one gate driver 118 communicably coupled with the resonant block 116 and the inverter 106. Specifically, the control unit 110 comprises the current regulation unit 114, a phase detection unit 112, a resonant block 116, and at least one gate driver 118. The phase detection unit 112, which is communicably coupled with both the sensing unit 108 and the current regulation unit 114, monitors the magnitude of the output voltage signal from the AC power network 104 and determines the phase angle of the voltage. Advantageously, the phase angle provides information about the timing and synchronization between the inverter’s output current and the AC grid voltage. The phase angle or phase mentioned above comprises a single-phase voltage signal or a three-phase voltage signal. Further, the accurate detection of the phase angle allows for the proper adjustment of the inverter's output current, ensuring that the output current is in phase with the AC grid, which is essential for high-efficiency power conversion. Furthermore, the current regulation unit 114 regulates the current flowing from the inverter into the AC power network 104, ensuring that the current remains consistent with the desired current waveform that matches the grid’s requirements. Furthermore, the current regulation unit 114 involves computing the reference current based on grid parameters, such as voltage and phase, and continuously adjusting the inverter's output to minimize discrepancies. Furthermore, the resonant block 116 within the control unit 110 performs a critical function in managing the dynamics of the system by processing the signals from the current regulation unit. The resonant block 116 receives the processed control signals and performs signal conditioning to optimize the quality of the output. The conditioning of the output involves the attenuation of unwanted low-frequency components from the control signals using resonant filtering techniques. Additionally, by passing the error signals through a narrow band filter, the resonant block 116 ensures that only the high-frequency components of the signal are passed, improving the accuracy of the feedback mechanism. The narrow band filter ensures that the most relevant error components are addressed, with noise and low-frequency components that do not impact the inverter's operation being attenuated. The attenuation reduces the possibility of interference and ensures that the inverter responds more efficiently to the grid’s demands. The integration of the current regulation unit 114, phase detection unit 112, and resonant block 116 into the control unit 110 significantly enhances the power conversion system's 100 precision and responsiveness. The current regulation unit 114 ensures that the inverter’s output current is regulated in real-time based on grid conditions, and the phase detection unit ensures that the inverter’s output is phase-locked with the grid voltage, providing superior synchronization. Furthermore, the resonant block 116 further refines the system’s performance by ensuring that only the necessary high-frequency error signals are used for control, eliminating unnecessary noise and minimizing the effects of low-frequency distortions. Therefore, the combination of advanced control and filtering ensures that the inverter operates at optimal efficiency, producing a high-quality, grid-synchronized output. Subsequently, by continuously monitoring and adjusting the phase and current waveforms, the system minimizes energy losses due to phase mismatches or current fluctuations, contributing to better grid stability and compliance with grid standards. The resonant block’s 116 filtering capability also reduces the potential for harmonic distortions (higher harmonics) and other unwanted artifacts in the output, leading to cleaner power being fed into the grid. Additionally, the ability to filter out low-frequency noise and focus on the relevant high-frequency components allows for more responsive and efficient control of the inverter’s switching, resulting in reduced switching losses.
In an embodiment, the sensing unit 108 comprises at least one voltage sensor 120 configured to sense a magnitude of output voltage signal and at least one current sensor 122 configured to sense a magnitude of output current signal of the AC power network 104. The voltage sensor 120 measures the output voltage signal from the AC power network 104, providing real-time data on the voltage amplitude and waveform characteristics. The voltage measurement ensures that the inverter’s 106 output is synchronized with the AC grid voltage. Further, the current sensor 122 measures the output current signal flowing from the inverter 106 into the AC network 104. By detecting both the magnitude and the waveform of the current, the sensor ensures that the inverter’s current matches the grid's requirements, maintaining proper current synchronization therefore minimizing power losses and ensuring efficient energy transfer. Consequently, both sensors work together to provide a comprehensive real-time view of the AC grid’s operating conditions, feeding the data to the control unit 110 for further processing and response. The sensing unit 108 is designed to sense and measure the magnitude of output voltage and current signals of the AC power network 104. The voltage and current measurements from the sensors allow the control unit 110 to accurately assess the grid’s status and determine the necessary adjustments to the inverter’s operation. The magnitude of the output voltage signal indicates the voltage level and any fluctuations in the grid's voltage profile. Similarly, the output current signal represents the actual current supplied by the inverter 106 to the AC grid 104, which varies depending on the grid’s load and voltage conditions. Furthermore, by continuously measuring the above-mentioned parameters, the sensing unit 108 allows the system to react in real-time, adjusting the inverter’s operation to optimize power quality and ensure that the AC output meets the requirements of the AC power network 104. The measurements are also used for phase angle detection and current regulation, forming the basis for determining the inverter’s control signals. The continuous measurement of both voltage and current enables the system to dynamically adjust the operation in response to grid fluctuations, ensuring stable and efficient energy conversion. By accurately sensing the output voltage and current, the system 100 computes real-time phase and current errors, allowing the control unit 110 to adjust the inverter’s output accordingly. Consequently, the controlled output of the inverter 106 leads to a more efficient and stable power conversion, with minimal energy losses due to mismatches between the inverter and the grid. Additionally, the measurements are essential for maintaining compliance with grid standards, reducing disturbances, and ensuring that the inverter operates within the acceptable range for both voltage and current. Advantageously, the above-mentioned sensors ensure grid synchronization by continuously comparing the inverter’s output with the actual voltage and current levels in the AC network 104, which minimizes harmonic distortion and phase mismatches. Therefore, the overall power quality is improved and reduces losses associated with reactive power. Further, the system's 100 ability to detect variations in both voltage and current allows for real-time corrections in the inverter’s output, thereby maximizing energy efficiency and ensuring that the power supplied to the grid is of the highest quality. The dynamic control also allows the system to be adaptable to different grid conditions, such as voltage fluctuations or varying load conditions, ensuring that the system remains reliable, robust, and efficient in a wide range of operational scenarios.
In an embodiment, the phase detection unit 112 is configured to receive the magnitude of the output voltage signal and determine at least one phase angle of the output voltage signal. The phase detection unit 112 receives the magnitude of the output voltage signal from the sensing unit 108, which measures the real-time voltage waveform of the AC grid 104. Based on the received voltage signal, the phase detection unit 112 computes the phase angle of the output voltage signal. The phase angle represents the temporal shift between the voltage waveform from the AC grid and the current waveform supplied by the inverter. Further, by continuously determining the phase angle, the phase detection unit 112 enables the system 100 to monitor the inverter’s current output alignment with the grid voltage, thereby enhancing the synchronization between the current and the grid voltage. The procedure of phase angle detection involves analyzing the time relationship between the AC grid’s voltage waveform and the inverter’s output. The phase detection unit 112 uses the magnitude of the voltage signal, which serves as the input reference, and performs a phase shift analysis to determine the amount the inverter’s output voltage is leading or lagging the grid’s voltage. The calculation is achieved by comparing the instantaneous voltage values over time, obtaining the phase difference, and converting the data into a phase angle. The phase angle is used as a key input for the current regulation unit 112, which adjusts the inverter's current output to ensure that the current matches the phase and frequency of the AC grid 104. The phase detection unit 112 also includes signal processing techniques to filter noise and enhance the accuracy of phase determination, ensuring that the inverter’s operation remains precise under fluctuating grid conditions. Furthermore, by determining the phase angle of the output voltage signal, the system 100 adjusts the inverter’s output current to match the grid’s voltage waveform precisely. The above-mentioned matching provides synchronization that minimizes power factor issues, reduces harmonic distortions, and ensures an efficient power conversion process. The advantages of incorporating the phase detection unit 112 into the power conversion system include improved power quality by ensuring that the inverter’s current output is perfectly in phase with the AC grid voltage, thereby minimizing reactive power and ensuring that the system delivers real power to the grid. The synchronization helps in reducing energy losses and improving the overall efficiency of the system. Further, the precise phase angle detection enhances the inverter’s response to grid fluctuations by allowing the system to adjust in real-time to changes in the grid’s voltage and frequency. As a result, the inverter 106 maintains a stable output, independent of voltage variations in the grid. Finally, phase angle detection helps in regulatory compliance, as many electrical grids have strict requirements for phase synchronization between connected generators (in this case, inverters) and the grid.
In an embodiment, the current regulation unit 114 is configured to receive the at least one phase angle of the output voltage signal and compute at least one current unit vector based on the received phase angle. The current regulation unit 114 receives the phase angle of the output voltage signal from the phase detection unit 112 and computes the current unit vector based on the received phase angle. The unit vector represents the direction and magnitude of the current waveform in relation to the grid’s voltage, providing a reference for adjusting the inverter’s output current. Further, the phase angle is a measure of the temporal displacement between the AC grid's voltage and current waveforms, and is crucial for determining the optimal alignment of the inverter’s output current. Furthermore, by calculating the current unit vector, the current regulation unit 114 ensures that the inverter’s output current aligns in the correct phase and magnitude to maintain synchronization with the grid, thereby optimizing power conversion and energy transfer. The technique employed by the current regulation unit 114 involves using the phase angle to calculate a vector representation of the ideal current. Specifically, the magnitude of the output current is proportional to the power requirements, and the phase of the current is determined by the phase angle of the AC grid voltage. The computation involves the phase angle to compute the sine or cosine components of the current waveform, effectively aligning the inverter's output current in both magnitude and phase with the AC grid. The alignment allows the system 100 to compensate for the discrepancies between the inverter’s output and the grid’s voltage waveform, ensuring that the power delivered to the grid is efficient and stable. Furthermore, the current unit vector provides an ideal reference, which is used in controlling the inverter’s operation. Consequently, by calculating the current unit vector, the system ensures that the inverter’s 106 output current is properly aligned with the voltage waveform of the grid, thus enhancing the overall power quality. The synchronization minimizes the phase difference between the current and voltage waveforms, which reduces the amount of reactive power and enhances the real power delivery to the grid. The enhancement leads to improved energy efficiency and more effective utilization of the available power, ensuring that the inverter operates at its maximum performance without introducing distortions or inefficiencies. The advantages of the above-mentioned approach include better grid stability and improved power factor, as the inverter’s 106 output current is phase-locked with the grid’s voltage. Further, the harmonic distortion is also reduced as the inverter’s current waveform is corrected to match the grid’s voltage waveform. Therefore, the system minimizes energy losses and optimizes the voltage and current synchronization. Furthermore, the dynamic adjustment of the inverter’s current output based on the computed unit vector allows the system to adapt to varying grid conditions such as voltage fluctuations or phase imbalances, ensuring that the inverter always delivers stable and high-quality power.
In an embodiment, the current regulation unit 114 is configured to compute at least one reference current signal based on the computed unit vector and an ideal AC network input power. Specifically, based on the unit vector determined by the phase detection unit 112, the current regulation unit 114 calculates the reference current signal by factoring in the ideal AC network input power. The ideal AC network input power is the desired power profile of the AC grid 104, consisting of sinusoidal voltage and current waveforms with a specific magnitude and phase relationship. Further, the unit vector provides the required phase information to ensure that the current generated by the inverter 106 is in proper phase alignment with the AC grid 104. Furthermore, by using the phase information along with the desired input power specifications, the current regulation unit 114 computes the reference current signal, ensuring that the inverter’s current output will be optimal in both magnitude and phase. The calculation of the reference current signal involves two primary components: the magnitude and phase angle of the current. First, the magnitude of the reference current is determined by comparing the power required by the AC grid 104, typically calculated from the desired active power (real power) and voltage levels, against the ideal network conditions. Further, by multiplying the magnitude of the reference current by the sine or cosine components of the unit vector, the current regulation unit 114 constructs the reference current signal. The reference current signal serves as the target output for the inverter’s current, ensuring that the current signal follows the ideal waveform required for efficient power transfer to the grid 104. The computation of the reference current signal provides the generation of a precise control signal for the inverter 106, ensuring that the inverter 106 produces the desired current waveform that is perfectly in phase and magnitude with the AC grid. Furthermore, the reference current signal directly reflects the system’s power needs, providing the inverter 106 with an accurate target to match the grid’s voltage waveform, thus enhancing the system's ability to transfer energy efficiently. Furthermore, the precise computation minimizes reactive power and harmonic distortion, leading to a reduction in grid disturbances and improving the overall power factor of the system. The advantages of the above-mentioned approach include the ability to dynamically adjust the inverter’s 106 current output to match the grid’s ideal power conditions, ensuring optimal energy conversion and contributing to enhanced grid stability. Furthermore, by continuously adjusting the reference current based on real-time grid parameters, the system 100 adapts to fluctuations in grid voltage or load, ensuring reliable power delivery. Additionally, the approach ensures compliance with grid standards for power quality, as the reference current signal is specifically designed to match the phase and magnitude of the grid’s requirements. Consequently, a significant reduction in energy losses is achieved with improved voltage and current synchronization, and better integration of renewable energy sources.
In an embodiment, the current regulation unit 114 is configured to compare the at least one reference current signal with the magnitude of output current signal of the AC power network 104 and compute at least one current error signal based on the comparison. The output current signal of the AC power network 104 represents the actual current flowing in the grid, and the reference current signal represents the desired current waveform that the inverter 106 needs to output in order to synchronize with the grid. The representation of the signal, as mentioned above, is the root mean square value of the current signal. The comparison of the two signals allows the system to determine any deviation or discrepancy between the actual and the desired current, thereby computing a current error signal. The means of computing the current error signal involves subtracting the actual output current (from the AC power network 104) from the reference current signal. The result is the current error signal, which quantifies the difference between the inverter’s 106 current output and the ideal current needed for synchronization with the grid 104. The current error signal serves as an input for further processing within the current regulation unit 114. The current regulation unit 114 applies the error signal to adjust the inverter’s output, reducing the deviation from the reference current and bringing the system closer to achieving optimal synchronization. Further, by continuously comparing the reference current signal with the output current, the current regulation unit performs dynamic adjustments to maintain proper phase and magnitude alignment, ensuring efficient energy transfer. By computing and processing the current error signal, the system 100 ensures that the inverter 106 responds in real-time to discrepancies between the ideal current and the actual grid conditions. Therefore, power quality, grid stability, and energy efficiency are improved. The ability to adjust the inverter’s 106 current output based on the computed error signal ensures that the system delivers accurate power to the grid, reducing reactive power and minimizing harmonic distortion. Additionally, the feedback mechanism helps the system maintain phase synchronization, which is critical for maintaining the power factor and reducing the grid instability or power quality issues. Therefore, the above-mentioned comparison enables seamless integration of the DC power source 102 by ensuring that the inverter’s 106 output is always aligned with the grid’s requirements under dynamic conditions.
In an embodiment, the current regulation unit 114 is configured to generate at least one sliding surface based on the computed at least one current error signal and apply a convergence rule on the generated at least one sliding surface to control the at least one current error signal. The current regulation unit 114 is configured to perform current control in a power conversion system 100 by employing a sliding mode control strategy. Specifically, the current regulation unit 114 generates at least one sliding surface based on a computed current error signal, which represents the difference between a reference current signal and an actual measured current signal associated with an electrical load or power stage. The generation of the sliding surface involves constructing a mathematical expression, typically involving a design constant selected to influence the convergence speed and system dynamics. The sliding surface defines the locus in the state space of the controlled system exhibiting a robust performance. Further, as the system 100 trajectory reaches the sliding surface, the current regulation unit 114 ensures that the system operates along the trajectory to maintain stability and desired current regulation under varying load conditions and input disturbances. The current regulation unit 114 further applies a convergence rule, such as, but not limited to, reaching law to the generated sliding surface to control the current error. The convergence rule is designed to ensure finite-time, exponential, or asymptotic convergence of the system state toward the sliding surface. Specifically, the convergence rule ensures that the current error is forced to zero within a finite period. In some instances, to mitigate chattering effects commonly associated with discontinuous control inputs, a boundary layer approach or continuous approximation (using a saturation function) is utilized. Furthermore, Lyapunov stability analysis is optionally employed to ensure that the convergence rule leads to a globally stable system with bounded inputs and outputs. The above-mentioned stable system 100 ensures precise and robust current tracking performance also in the presence of model inaccuracies, component tolerances, and external disturbances such as fluctuating input voltages or load changes. The employment of a sliding surface in combination with a convergence rule enables high-speed dynamic response, reduced steady-state error, and improved disturbance rejection. Therefore, the reduced steady-state error contributes to enhanced efficiency, thermal management, and system reliability in power conversion systems. Moreover, the flexibility in designing convergence rules and sliding surfaces allows adaptation to various converter topologies, including buck, boost, and inverter configurations, and provides a modular and scalable control solution. The reduction in computational complexity and real-time control feasibility further supports integration into embedded digital signal processors (DSPs) or microcontrollers.
In an exemplary embodiment, the power conversion system 100 is implemented to interface a photovoltaic-based Direct Current (DC) power source 102, delivering a nominal DC voltage of 380 V, with a 230 V, 50 Hz Alternating Current (AC) power network 104. The inverter 106 comprises a three-phase full-bridge topology using insulated gate bipolar transistors (IGBTs) with a switching frequency of 20 kHz. The sensing unit 108 comprises the voltage sensor 120 configured to measure the output line voltage of the AC power network 104 with a range of 0–300 Volts RMS, and a current sensor 122 configured to measure load current up to 20 Ampere RMS. The control unit 110 includes the phase detection unit 112 employing a digital phase-locked loop (PLL) to detect the phase angle ? of the output voltage signal with an accuracy of ±1°. The current regulation unit 114 computes the current unit vector based on the detected phase angle and derives a reference current signal (using ratio of target active power flow and output line voltage RMS) representing an ideal sinusoidal waveform corresponding to a target active power flow of 3.5 kW. The reference signal is compared with the measured current to obtain a current error signal. A sliding surface is generated using the error signal and its derivate in the time domain, and a convergence rule is applied with a reaching law coefficient of 500 to enforce error reduction (via a signum function). The resonator block 116 processes the error signal using a second-order narrow band filter with a center frequency of 50 Hz and a quality factor (Q) of 20, effectively attenuating low-frequency disturbances. The filtered signal is converted into a command signal, which is received by the gate driver 118, implemented using isolated gate drive ICs such as the IR2110, to generate gate signals that control the switching of the inverter 106 in accordance with the desired output waveform. Therefore, the system ensures minimal total harmonic distortion (<3%) and rapid dynamic response under load transients, validating the suitability for grid-interactive renewable energy applications.
In an embodiment, the resonator block 116 is configured to receive at least one current error signal and attenuate low frequencies of the at least one current error signal. Specifically, the resonator block 116 comprises the narrow band filter with a predefined gain acting as a factor of attenuation of the filter. Further, the narrow band filter is designed to target and eliminate low-frequency noise and disturbances that hinder the precise control of the inverter. The low-frequency component includes slow variations in current due to grid fluctuations or other non-ideal grid behaviors, is filtered out, allowing only the high-frequency components of the error signal. The above-mentioned approach improves the signal's quality, ensuring that the control signals sent to the inverter 106 are based on relevant and immediate discrepancies between the reference current and the output current. The narrow band filter within the resonator block 116 works by allowing a specific range of frequencies to pass through and attenuating frequencies outside of this range. The filtering ensures that only the desired error signals that directly influence the operation of the inverter’s control unit are utilized. By removing low-frequency noise or slow variations in the error signal, the system 100 ensures that the inverter 106 responds only to the high-frequency components that reflect immediate changes in the grid's current requirements. Therefore, the inverter’s 106 current adjustment is enhanced, ensuring a perfect synchronization with the AC grid 104 under rapidly changing conditions. The filtered error signal reduces the risk of slow response times or over-correction caused by low-frequency disturbances, thus preventing redundant energy losses or grid instability. The advantages of the filtering include improved dynamic performance, allowing the inverter to respond accurately to high-frequency changes in the current. Further, by attenuating low-frequency components, the system reduces the harmonic distortion or oscillations that result from low-frequency noise.
In an embodiment, the resonator block 116 is configured to generate at least one command signal based on the band-passed current error signal. The resonator block 116 utilizes the filtered signal to generate the command signal, which serves as the input for the inverter's gate signal driver 118. The command signal carries the data, including parameters such as pulse width modulation (PWM) adjustments or other control schemes, depending on the inverter’s 106 control architecture. The resonator block 116 typically employs a control algorithm, such as a PID controller (Proportional-Integral-Derivative) or other feedback-based mechanisms, to convert the current error signal into an actionable command. The resonator block 116 processes the filtered error signal and determines the appropriate adjustments to be made to the inverter's switching pattern. For instance, in case the error signal indicates that the inverter 106 is producing overlimit or underlimit current, the resonator block 116 adjusts the pulse width modulation (PWM) of the inverter’s 106 gates, ensuring that the inverter’s output is corrected to match the ideal current reference. The dynamic process of generating the command signal based on real-time feedback enables continuous fine-tuning of the inverter’s 106 performance. Further, by processing the filtered error signal, the resonator block 116 ensures that only the relevant, high-frequency components of the error are used to adjust the inverter’s output. The blocking allows for accurate and timely correction of any discrepancies between the desired reference current and the actual output, improving the synchronization of the inverter 106 with the AC grid 104. The generation of the command signal in response to real-time error corrections ensures that the inverter’s 106 output remains dynamically aligned with the grid’s requirements. The advantages of generating the command signal based on the filtered current error include that the inverter 106 is responsive to the grid’s 104 changing conditions, maintaining optimal performance under load or voltage fluctuating conditions.
In an embodiment, the at least one gate signal driver 118 is configured to receive the at least one command signal and generate at least one gate signal to control the switching operation of the inverter 106. The gate signal driver 118 interprets the command signal and generates the corresponding gate signals that directly control the opening and closing of the inverter’s switches. The gate signals regulate the on-off switching times of the semiconductor devices (such as, but not limited to, IGBTs or MOSFETs) in the inverter 106, thereby controlling the amplitude, frequency, and phase of the AC output waveform generated by the inverter 106. The gate signal driver 118 is designed to ensure precise timing of the gate signals in accordance with the desired output of the inverter 106. Further, depending on the magnitude and characteristics of the command signal, the driver 118 adjusts the duty cycle of the switching devices, determining the switch-on time of the inverter during each cycle. The adjustment ensures that the inverter 106 delivers the correct amount of current to the grid 104, maintaining optimal efficiency and minimizing losses. The gate signals directly control the timing and synchronization of the inverter’s switching devices to convert the DC input power into an AC output that matches the voltage, frequency, and phase requirements of the grid. Furthermore, by accurately adjusting the gate signals based on the PWM control, the system 100 ensures that the inverter's output current is correctly modulated to match the reference current, ensuring synchronization with the AC grid 104. The ability to control the inverter’s 106 switching behavior through the gate signal driver 118 allows for dynamic regulation of the inverter’s output, leading to stable and high-quality power delivery. The real-time adjustments of the gate signals based on the current error signal and the reference current ensure that the inverter 106 responds promptly to variations in the grid 104, such as changes in load or voltage, optimizing overall performance. The advantages of the above-mentioned approach include the precise control over the inverter's 106 switching minimizes the generation of harmonics and distortion in the output current, ensuring that the power delivered to the grid meets power quality standards. Further, the dynamic PWM control enables the inverter 106 to respond quickly to changes in grid 104 conditions, thus improving the system's 100 ability to maintain synchronization with the grid 104, even under fluctuating operating conditions.
In accordance with a second aspect, there is described a method of interfacing a Direct Current (DC) power source with an Alternating Current (AC) power network, the method comprises:
- determining at least one phase angle of the output voltage signal via a phase detection unit;
- comparing at least one reference current signal with a magnitude of output current signal of the AC power network via the current regulation unit;
- computing at least one current error signal based on the comparison via the current regulation unit;
- generating at least one sliding surface based on the computed at least one current error signal via the current regulation unit; and
- generating at least one gate signal to control switching operation of an inverter, via at least one gate driver.
Figure 3 describes a method 200 of interfacing a Direct Current (DC) power source 102 with an Alternating Current (AC) power network 104. The method 200 starts at a step 202. At the step 202, the method 200 comprises determining at least one phase angle of the output voltage signal via a phase detection unit 112. At a step 204, the method 200 comprises comparing at least one reference current signal with a magnitude of output current signal of the AC power network via the current regulation unit 114. At a step 206, the method 200 comprises computing at least one current error signal based on the comparison via the current regulation unit 114. At a step 208, the method 200 comprises generating at least one sliding surface based on the computed at least one current error signal via the current regulation unit 114. At a step 210, the method 200 comprises generating at least one gate signal to control switching operation of an inverter 106, via at least one gate driver 118.
In an embodiment, the method 200 comprises receiving the at least one phase angle of the output voltage signal and computing at least one current unit vector based on the received phase angle, via the current regulation unit 114.
In an embodiment, the method 200 comprises applying a convergence rule on the generated at least one sliding surface to control the at least one current error signal, via the current regulation unit 114.
In an embodiment, the method 200 comprises attenuating low frequencies of the at least one current error signal, via the resonator block 116.
In an embodiment, the method 200 comprises sensing a magnitude of output voltage signal via at least one voltage sensor 120. Further, the method 200 comprises sensing a magnitude of output current signal via at least one current sensor 120. Furthermore, the method 200 comprises receiving the magnitude of output voltage signal via the phase detection unit 112. Furthermore, the method 200 comprises computing at least one current unit vector based on the received phase angle via the phase detection unit 112. Furthermore, the method 200 comprises computing at least one reference current signal based on the computed unit vector and an ideal AC network input power via the current regulation unit 114. Furthermore, the method 200 comprises applying a convergence rule on the at least one generated sliding surface to control the at least one current error signal, via the current regulation unit 114. Furthermore, the method 200 comprises attenuating low frequencies of the at least one current error signal.
In an embodiment, the method 200 comprises determining at least one phase angle of the output voltage signal via a phase detection unit 112. Furthermore, the method 200 comprises comparing at least one reference current signal with a magnitude of the output current signal of the AC power network via the current regulation unit 114. Furthermore, the method 200 comprises computing at least one current error signal based on the comparison via the current regulation unit 114. Furthermore, the method 200 comprises generating at least one sliding surface based on the at least one computed current error signal via the current regulation unit 114. Furthermore, the method 200 comprises generating at least one gate signal to control switching operation of an inverter 106, via at least one gate driver 118.
Based on the above-mentioned embodiments, the present disclosure provides significant advantages of efficient inverter control, precise synchronization, and seamless power transfer. Consequently, the system results in enhanced harmonic rejection and stability, thereby reducing total harmonic distortion (THD) and improving power quality. Therefore, the invention is particularly suited for renewable energy interfaces requiring high precision, reliability, and dynamic control capability.
It would be appreciated that all the explanations and embodiments of the system 100 also apply mutatis-mutandis to the method 200.
In the description of the present invention, it is also to be noted that, unless otherwise explicitly specified or limited, the terms “disposed,” “mounted,” and “connected” are to be construed broadly, and may for example be fixedly connected, detachably connected, or integrally connected, either mechanically or electrically. They may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Modifications to embodiments and combinations of different embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as “including”, “comprising”, “incorporating”, “have”, and “is” used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural where appropriate.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the present disclosure, the drawings, and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.
,CLAIMS:WE CLAIM:
1. A power conversion system (100) for interfacing a Direct Current (DC) power source (102) with an Alternating Current (AC) power network (104), the system (100) comprises:
- an inverter (106) electrically coupled to the DC power source (102) and the AC power network (104);
- a sensing unit (108) communicably coupled to the AC power network (104); and
- a control unit (110) communicably coupled to the inverter (106) and the sensing unit (108),
wherein the control unit (110) is configured to control the inverter (106) based on at least one input received from the sensing unit (108) and the AC power network (104).

2. The system (100) as claimed in claim 1, wherein the control unit (110) comprises a phase detection unit (112) to communicably couple the control unit (110) to the sensing unit (108); a current regulation unit (114) communicably coupled with the phase detection unit (112); a resonant block (116) communicably coupled with the current regulation unit (114); and at least one gate driver (118) communicably coupled with the resonant block (116) and the inverter (106).

3. The system (100) as claimed in claim 1, wherein the sensing unit (108) comprises at least one voltage sensor (120) configured to sense a magnitude of output voltage signal of the AC power network (104) and at least one current sensor (122) configured to sense a magnitude of output current signal of the AC power network (104).

4. The system (100) as claimed in claim 1, wherein the phase detection unit (112) is configured to receive the magnitude of output voltage signal and determine at least one phase angle of the output voltage signal.

5. The system (100) as claimed in claim 1, wherein the current regulation unit (114) is configured to receive the at least one phase angle of the output voltage signal and compute at least one current unit vector based on the received phase angle.

6. The system (100) as claimed in claim 1, wherein the current regulation unit (114) is configured to compute at least one reference current signal based on the computed unit vector and an ideal AC network input power.

7. The system (100) as claimed in claim 1, wherein the current regulation unit (114) is configured to compare the at least one reference current signal with the magnitude of output current signal of the AC power network (104) and compute at least one current error signal based on the comparison.

8. The system (100) as claimed in claim 1, wherein the current regulation unit (114) is configured to generate at least one sliding surface based on the computed at least one current error signal and apply a convergence rule on the generated at least one sliding surface to control the at least one current error signal.

9. The system (100) as claimed in claim 1, wherein the resonator block (116) is configured to receive at least one current error signal and attenuate low frequencies of the at least one current error signal.

10. The system (100) as claimed in claim 1, wherein the resonator block (116) is configured to generate at least one command signal based on the band-passed current error signal.

11. The system (100) as claimed in claim 1, wherein the at least one gate signal driver (118) is configured to receive the at least one command signal and generate at least one gate signal to control pulse width modulation of the inverter (106).

12. A method (200) of interfacing a Direct Current (DC) power source (102) with an Alternating Current (AC) power network (104), the method (200) comprises:
- determining at least one phase angle of the output voltage signal via a phase detection unit (112);
- comparing at least one reference current signal with a magnitude of output current signal of the AC power network via the current regulation unit (114);
- computing at least one current error signal based on the comparison via the current regulation unit (114);
- generating at least one sliding surface based on the computed at least one current error signal via the current regulation unit (114); and
- generating at least one gate signal to control switching operation of an inverter (106), via at least one gate driver (118).

13. The method (200) as claimed in claim 12, the method (200) comprises receiving the at least one phase angle of the output voltage signal and computing at least one current unit vector based on the received phase angle, via the current regulation unit (114).

14. The method (200) as claimed in claim 12, the method (200) comprises applying a convergence rule on the at least one generated sliding surface to control the at least one current error signal, via the current regulation unit (114).

15. The method (200) as claimed in claim 12, the method (200) comprises attenuating low frequencies of the at least one current error signal.