DESC:METHOD AND SYSTEM FOR INSULATION MEASUREMENT
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims priority from Indian Provisional Patent Application No. 202421026807 filed on 31/03/2024, the entirety of which is incorporated herein by a reference.
TECHNICAL FIELD
The present disclosure generally relates to a power conversion system. Particularly, the present disclosure relates to a system for monitoring insulation failure on an AC side of a power conversion system using a DC side insulation monitoring device. Furthermore, the present disclosure relates to a method of monitoring insulation failure on an AC side of a power conversion system using a DC side insulation monitoring device.
BACKGROUND
The electric vehicle (EV) market is rapidly expanding, driven by advancements in battery technology and increasing environmental concerns. The auto-manufacturers re investing heavily in EV infrastructure, including fast-charging networks and improved energy efficiency. Additionally, the solid-state batteries and high-efficiency powertrains are emerging as key innovations for future EVs.
Recently, the motor drive system in electric vehicles has evolved with advancements in power electronics, control algorithms, and efficiency optimization. The modern electric and hybrid vehicles utilize high-efficiency inverters and advanced motor designs like PMSM and induction motors. Also, the emerging trends include SiC and GaN-based inverters for reduced losses and higher power density. However, with increasing usage of motor drive in vehicles, the insulation problems in the motor drive arises. The insulation problems in the motor drive occur due to factors such as electrical stress, thermal degradation, mechanical vibrations, and environmental conditions like moisture or contaminants. Over time, high-voltage stress may cause insulation breakdown, leading to leakage currents and reduced system efficiency. Also, excessive heat from prolonged operation accelerates material aging, weakening insulation properties. Furthermore, the mechanical shocks and continuous vibrations may create microcracks in insulating layers, increasing the risk of failure. Additionally, dust, humidity, and chemical exposure can degrade insulation surfaces, leading to unintended short circuits or safety hazards.
Traditionally, the isolation in the motor drives of electric vehicles traditionally monitored using resistance-based measurement techniques, voltage monitoring methods, and insulation resistance testers. These methods primarily relied on measuring the insulation resistance between the high-voltage (HV) system and the vehicle chassis to detect any potential faults or degradation in isolation. One of the common techniques is resistance measurement method, where a high-value resistor is connected between the HV bus and the chassis ground. By applying a known voltage and measuring the leakage current, the insulation resistance is calculated. If the resistance dropped below a predefined threshold, an isolation fault is detected. However, the method has significant drawbacks. Firstly, this method required additional passive components that added to the system complexity and cost. Secondly, the method may not detect dynamic isolation failures, such as insulation breakdown occurring due to transient voltage spikes or mechanical stress over time. Moreover, during operation, insulation degradation is often gradual and not easily captured by periodic resistance measurements, leading to potential undetected faults. Another conventional approach involved voltage-based monitoring, where the voltage difference between the HV system and the chassis ground is continuously observed. Any unexpected fluctuations in the voltage difference may indicate a loss of isolation. While the method is relatively straightforward, but the method suffered from low sensitivity to minor faults, making the method ineffective in detecting early-stage insulation degradation. Additionally, the method prone to false positives due to external noise, temperature variations, or minor fluctuations in the high-voltage system, leading to unnecessary warnings or system shutdowns. Moreover, a more manual method is often used which is the insulation resistance test using a megohmmeter, where a high DC voltage (e.g., 500V to 1000V) is applied to the motor drive circuit while the vehicle is off, and the resulting leakage current is measured to determine insulation integrity. This method is highly effective in detecting severe insulation breakdowns but not impractical for real-time monitoring, as the method required the vehicle to be taken offline for testing. Moreover, the method may be only detecting the insulation failures that had already occurred and is not effective in predicting insulation degradation over time.
Therefore, there is a need to provide an improved technique for isolation detection in a motor drive of an electric vehicle to overcome one or more problems associated as set forth above.
SUMMARY
An object of the present disclosure is to provide a system for monitoring insulation failure on an AC side of a power conversion system using a DC side insulation monitoring device.
Another object of the present disclosure is to provide a method of monitoring insulation failure on an AC side of a power conversion system using a DC side insulation monitoring device.
In accordance with first aspect of the present disclosure, there is provided a system for monitoring insulation failure on an AC side of a power conversion system using a DC side insulation monitoring device. The system comprising a DC power source having positive and negative terminals, a three-phase inverter comprising a plurality of switching elements, an AC load having multiple terminals connected to the three-phase inverter, an insulation monitoring device connected to the DC side of the power conversion system and a controller. The controller configured to implement a predetermined switching sequence of the plurality of switching elements to selectively connect at least one terminal of the AC load to the DC side and detect insulation failure on the AC side using the DC side insulation monitoring device.
The present disclosure provides the system for monitoring insulation failure on an AC side of the power conversion system using the DC side insulation monitoring device. The system as disclosed by present disclosure is advantageous in terms of detection of the insulation failure on the AC side of the power conversion system using the existing DC side insulation monitoring device. Beneficially, the system eliminates the need for additional AC-side monitoring hardware, thereby reduces the complexity, cost, and space requirements. Beneficially, the system ensures the accurate insulation failure detection without interfering with normal operation. Additionally, the system significantly enhances the safety and reliability by preventing unexpected faults during active operation. Furthermore, the system also facilitates systematic and sequential insulation resistance measurement for each terminal which provides a comprehensive analysis of the AC side insulation status. Furthermore, the system beneficially allows the early fault detection, thereby prevents potential failures and improves the system longevity.
In accordance with second aspect of the present disclosure, there is provided a method of monitoring insulation failure on an AC side of a power conversion system using a DC side insulation monitoring device. The method comprises providing a power conversion system comprising a DC power source having positive and negative terminals, a three-phase inverter comprising a plurality of switching elements and an AC load having multiple terminals connected to the three-phase inverter, implementing a predetermined switching sequence of the plurality of switching elements to selectively connect at least one terminal of the AC load to the DC side and detecting insulation failure on the AC side using a DC side insulation monitoring device.
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:
FIG. 1 illustrates a block diagram of a system for monitoring insulation failure on an AC side of a power conversion system using a DC side insulation monitoring device, in accordance with an aspect of the present disclosure.
FIG. 2 illustrates a flow chart of a method for monitoring insulation failure on an AC side of a power conversion system using a DC side insulation monitoring device, in accordance with another aspect of the present disclosure.
FIG. 3 illustrates an electrical circuit diagram of a power conversion system, in accordance with an 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 recognise that other embodiments for carrying out or practising the present disclosure are also possible.
The description set forth below in connection with the appended drawings is intended as a description of certain embodiments of a system for monitoring insulation failure on an AC side of a power conversion system using a DC side insulation monitoring device and is not intended to represent the only forms that may be developed or utilised. The description sets forth the various structures and/or functions in connection with the illustrated embodiments; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimised to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.
The terms “comprise”, “comprises”, “comprising”, “include(s)”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, system that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or system. In other words, one or more elements in a system or apparatus preceded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.
In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings, and which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
The present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well known functions or constructions are not described in detail since they would obscure the description with unnecessary detail.
As used herein, the terms “electric vehicle”, “EV”, and “EVs” are used interchangeably and refer to any vehicle having stored electrical energy, including the vehicle capable of being charged from an external electrical power source. This may include vehicles having batteries which are exclusively charged from an external power source, as well as hybrid-vehicles which may include batteries capable of being at least partially recharged via an external power source. Additionally, it is to be understood that the ‘electric vehicle’ as used herein includes electric two-wheeler, electric three-wheeler, electric four-wheeler, electric pickup trucks, electric trucks and so forth.
As used herein, the term “insulation failure” refers to the degradation, breakdown, or loss of electrical insulation properties in the system, leads to unintended current leakage, short circuits, or reduced dielectric strength. The insulation failure occurs when the insulating material between conductive elements no longer effectively prevents electrical conduction, which may result from factors such as aging, mechanical stress, contamination, moisture ingress, thermal degradation, or electrical overstress.
As used herein, the terms “power conversion system” refers to a system configured to convert electrical power from one form to another, typically involving the transformation of voltage, current, or frequency characteristics to facilitate efficient power utilization, distribution, or control. The power conversion system may include one or more power sources, power electronic components such as inverters, converters, rectifiers, transformers, and associated control circuitry to regulate power flow between an input source and an output load. The system may operate in AC-DC, DC-AC, AC-AC, or DC-DC conversion modes depending on the application.
As used herein, the term “insulation monitoring device” refers to an electronic system configured to continuously or periodically measure the insulation resistance between an electrical system’s live conductors and ground. The insulation monitoring system is designed to detect insulation degradation or faults that may lead to leakage currents, electrical hazards, or system failures. The insulation monitoring device typically operates by injecting a low-level test signal into the system and analyzing the response to determine the insulation status.
As used herein, the term “DC power source” refers to a power supply device or system configured to generate and provide a direct current (DC) voltage and current for powering electrical or electronic components. The DC power source may include, but is not limited to, a battery, a fuel cell, a rectified AC power supply, a photovoltaic system, or any other energy storage or generation unit capable of delivering DC power to a connected electrical circuit or system.
As used herein, the term “positive terminal” refers to a conductive connection point in an electrical circuit or power source that maintains a higher electric potential relative to a corresponding negative terminal. The positive terminal serves as the point from which current conventionally flows out in a closed-loop circuit and is typically associated with the supply of electrical energy to connected components. The positive terminal may be part of a battery, power supply, or electrical system and can be physically identified based on polarity markings, structural configuration, or functional association with circuit elements.
As used herein, the term “negative terminal” refers to an electrical connection point of the power source, circuit, or component that serves as the lower potential side in an electrical system. The negative terminal is typically associated with the return path for electric current in a closed-loop circuit and is referenced as the terminal having a lower voltage relative to the corresponding positive terminal.
As used herein, the term “three-phase inverter” refers to an electrical device configured to convert a direct current (DC) input into a three-phase alternating current (AC) output. The three-phase inverter typically comprises a plurality of switching elements arranged in three half-bridge circuits, each corresponding to one phase of the AC output.
As used herein, the term “plurality of switching element” and “switching element” are used interchangeably and refer to two or more electrically controllable components, such as transistors, MOSFETs, IGBTs, or relays, that regulate the flow of electrical current within a circuit. The switching elements are typically used to control the operation of the power conversion system by selectively connecting or disconnecting different circuit components, such as an AC load or DC power source.
As used herein, the term “AC load” refers to an electrical component, device, or system that operates using alternating current (AC) and is electrically connected to receive power from an AC source or power conversion system. The AC load may include, but is not limited to, motors, resistive loads, inductive loads, capacitive loads, or any combination thereof, and may have one or more terminals configured to interface with an AC power supply or inverter output.
As used herein, the term “DC side” refers to the portion of the system associated with direct current (DC) power, including the DC power source, DC bus, and any components electrically connected to the DC power source before conversion to alternating current (AC). The DC side typically comprises elements such as DC power supply terminals, energy storage devices (e.g., batteries or capacitors), and DC input connections to the inverter or power conversion unit. The DC side serves as the primary source of electrical energy that undergoes conversion to AC for powering loads, such as motors or grid-connected systems.
As used herein, the term “controller” refers to an electronic processing unit or circuitry configured to execute predefined instructions for managing the operation of a system. The controller may include, but is not limited to, a microcontroller, a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or any combination thereof. The controller is operatively coupled to various system components, such as switching elements, sensors, and monitoring devices, to facilitate automated control, data processing, and decision-making. The controller may further include associated memory units, such as volatile or non-volatile storage, to store instructions, thresholds, or operational parameters. Additionally, the controller may interface with external communication networks or diagnostic systems for real-time monitoring, data logging, or remote-control applications.
As used herein, the term “switching sequence” refers to a predefined or dynamically determined order and timing of activation and deactivation of switching elements within a circuit, such as transistors, MOSFETs, or IGBTs, to achieve a specific electrical operation. The switching sequence governs the transition between different circuit states, ensuring controlled power flow, modulation, fault detection, or system functionality.
As used herein, the term “at least one terminal” and “terminal” are used interchangeably and refer to one or more terminals of the AC load that may be selectively connected to the DC side for insulation monitoring.
As used herein, the term “half-bridge circuits” refers to an electrical switching configuration that comprises two switching elements arranged in series between two voltage rails, typically a positive and a negative terminal of a DC power source. The junction between the two switching elements serves as an output node that may be selectively connected to either voltage rail based on the switching states. The half-bridge circuit configuration enables bidirectional control of current flow and is commonly used in power conversion systems, motor drives, and inverters to generate AC waveforms from a DC power source.
As used herein, the term “AC output terminal” refers to a conductive interface or connection point in the power conversion system, specifically in the inverter or power electronics circuit, through which alternating current (AC) is delivered to the external load. The AC output terminal serves as the electrical junction between the inverter’s switching elements and the connected AC load, such as a motor or other electrical equipment, enables the transfer of power while maintaining the designed phase relationships and voltage characteristics.
As used herein, the term “three-phase motor” refers to an electric motor that operates using a three-phase alternating current (AC) power supply. The three-phase motor consists of a stator with three windings, each spaced 120 electrical degrees apart, and a rotor that rotates within the stator's magnetic field. When a balanced three-phase voltage is applied, a rotating magnetic field is generated in the stator, inducing current in the rotor and producing torque to drive mechanical loads.
As used herein, the term “impedance” refers to the total opposition offered by an electrical circuit or component to the flow of alternating current (AC), comprising both resistance and reactance. Impedance is typically expressed in ohms (O) and varies with the frequency of the applied signal.
As used herein, the term "non-operation periods" refers to the time intervals when the power conversion system is not actively performing its primary function of converting and delivering power to the AC load. The non-operation periods may include Idle States, Standby Mode, Shutdown or Power-Off Conditions, Transition Periods, Fault or Protection States.
As used herein, the term “insulation status” refers to a condition that indicates the integrity and effectiveness of electrical insulation within a system. The insulation status is determined by evaluating parameters such as insulation resistance, leakage current, or potential faults in insulation materials. The insulation status may be classified into different states, such as normal, degraded, or failed, based on measured values compared against predetermined thresholds.
As used herein, the term “insulation resistance value” refers to the electrical resistance measured between a conductive component and ground or between conductive elements separated by an insulating material. The insulation resistance value quantifies the effectiveness of the insulation in preventing unintended current leakage. Typically expressed in ohms (O) or megaohms (MO), the insulation resistance value is determined by applying a test voltage and measuring the resulting leakage current.
As used herein, the term “predetermined threshold” refers to a predefined value or range used as a reference to evaluate a specific condition, parameter, or performance criterion.
Figure 1, in accordance with an embodiment describes a system 100 for monitoring insulation failure on an AC side of a power conversion system using a DC side insulation monitoring device. The system 100 comprising a DC power source 102 having positive and negative terminals, a three-phase inverter 104 comprising a plurality of switching elements 106, an AC load 108 having multiple terminals connected to the three-phase inverter 104, an insulation monitoring device 110 connected to the DC side of the power conversion system and a controller 112. The controller 112 configured to implement a predetermined switching sequence of the plurality of switching elements 106 to selectively connect at least one terminal of the AC load 108 to the DC side and detect insulation failure on the AC side using the DC side insulation monitoring device 110.
The present disclosure discloses the system 100 for monitoring insulation failure on an AC side of the power conversion system using the DC side insulation monitoring device. The system 100 as disclosed by present disclosure is advantageous in terms of providing the significant advancement in insulation failure detection for power conversion systems by enabling AC side monitoring using the DC side insulation monitoring device 110. Beneficially, the insulation monitoring device 110 eliminates the need for the separate insulation monitoring system on the AC side, thereby reduces the hardware complexity and cost. Beneficially, by utilizing a predetermined switching sequence, the system 100 selectively connects each terminal of the AC load 108 to the DC side which significantly allows the insulation monitoring device 110 to assess insulation integrity at each phase. Beneficially, the system 100 enhances the diagnostic accuracy by ensuring that the insulation faults on the plurality of AC terminals may be detected and localized efficiently. Additionally, the execution of the switching sequence during non-operation periods ensures the insulation monitoring may not interfere with normal system operation, thereby maintaining the efficiency and reliability of the system 100. Furthermore, the controller 112 as disclosed by present disclosure provides the controller-driven automation of the isolation detection process which minimizes the human intervention, thereby reduces the maintenance efforts and downtime of the system 100. Furthermore, the use of the three-phase inverter 104 with half-bridge circuits provides flexibility in switching operations to ensure the precise control over the insulation monitoring process. Furthermore, by comparing detected insulation resistance values against a predetermined threshold, the system 100 significantly enables the proactive fault detection, thereby prevents the potential failures and ensures the safety in high-voltage applications. Overall, the system 100 provides a cost-effective, efficient, and accurate approach to insulation failure monitoring.
In an embodiment, the three-phase inverter 104 forms three half-bridge circuits connected in parallel between the positive and negative terminals of the DC power source 102. Furthermore, each half-bridge circuit comprises a first switching element connected between the positive terminal of the DC power source 102 and a corresponding AC output terminal and a second switching element connected between the negative terminal of the DC power source 102 and the corresponding AC output terminal. The three-phase inverter 104 may be designed to facilitate the controlled switching operations that selectively connect the plurality of terminals of the AC load 108 to the DC side for insulation monitoring. Each half-bridge circuit comprises the first switching element positioned between the positive terminal of the DC power source and the corresponding AC output terminal, and the second switching element connected between the negative terminal of the DC power source and the corresponding AC output terminal. The switching element configuration enables the precise control over the conduction states of the terminals of the AC load 108 which allows the system 100 to execute the predetermined switching sequence for insulation failure detection. Additionally, the parallel arrangement of the half-bridge circuits ensures effective power conversion while maintaining the capability to integrate insulation monitoring functionality without requiring additional AC-side monitoring hardware.
In an embodiment, the AC load 108 is a three-phase motor having impedance represented as Za, Zb, and Zc. The impedance values correspond to the electrical resistance and reactance characteristics of each phase winding of the motor. The insulation monitoring device 110 assesses the insulation integrity by analyzing variations in the leakage current when the specific phase terminal may be selectively connected to the DC side using the predetermined switching sequence implemented by the controller 112. A deviation in the impedance values from the expected range may indicate insulation degradation which allows for early detection of potential faults.
In an embodiment, the controller 112 is configured to periodically execute the predetermined switching sequence during non-operation periods of the power conversion system. During the non-operation periods, the controller 112 initiates the switching sequence to selectively connect the at least one terminal of the AC load 108 to the DC side which enables the insulation monitoring device 110 to assess insulation integrity. Beneficially, the periodic execution allows continuous monitoring of insulation health without interfering with the normal operation of the power conversion system. Furthermore, by performing insulation diagnostics when the system 100 is idle which ensures the proactive fault detection, thereby reduces the risk of insulation failure during operation. Additionally, the use of controller 112 for automating the process of switching sequence minimizes the need for manual inspection and enhances the reliability of the system 100 by identifying potential insulation degradation before the system 100 leads to operational failures.
In an embodiment, the controller 112 is configured to deactivate all of the plurality of switching elements 106, activate a first switching element to connect a first terminal of the AC load 108 to the DC side, detect insulation failure at the first terminal using the insulation monitoring device 110, deactivate the first switching element, sequentially repeat the activation and detection steps for each remaining terminal of the AC load 108 and determine an overall AC side insulation status based on detection results from all terminals of the AC load 108. The controller 112 deactivates all the plurality of switching elements 106, ensures that no unwanted conduction paths exist within the three-phase inverter 104. Subsequently, the controller 112 activates the first switching element to establish the electrical connection between the first terminal of the AC load 108 and the DC side of the power conversion system. Once the connection may be established, the insulation monitoring device 110 performs the assessment to detect any insulation failure at the first terminal of the AC load 108. Along with the detection at the first terminal, the controller 112 deactivates the first switching element to disconnect the first terminal from the DC side. The controller 112 then sequentially repeats the activation and detection process for each remaining terminal of the AC load 108 ensures that the insulation failures across all terminals may individually assessed. Upon completing the detection process for all AC load terminals, the controller 112 aggregates the detection results to determine the overall AC side insulation status. Beneficially, the systematic approach for detection of the insulation status allows precise localization of insulation failures, thereby enhances the reliability and safety of the power conversion system while eliminating the need for the dedicated AC side insulation monitoring device 110.
In an embodiment, the system 100 for monitoring insulation failure on the AC side of the power conversion system using the DC side insulation monitoring device. The system 100 comprising the DC power source 102 having positive and negative terminals, the three-phase inverter 104 comprising the plurality of switching elements 106, the AC load 108 having multiple terminals connected to the three-phase inverter 104, the insulation monitoring device 110 connected to the DC side of the power conversion system and the controller 112. The controller 112 configured to implement the predetermined switching sequence of the plurality of switching elements 106 to selectively connect the at least one terminal of the AC load 108 to the DC side and detect insulation failure on the AC side using the DC side insulation monitoring device 110. Furthermore, the three-phase inverter 104 forms three half-bridge circuits connected in parallel between the positive and negative terminals of the DC power source 102. Furthermore, each half-bridge circuit comprises the first switching element connected between the positive terminal of the DC power source 102 and the corresponding AC output terminal and the second switching element connected between the negative terminal of the DC power source 102 and the corresponding AC output terminal. Furthermore, the AC load 108 is the three-phase motor having impedance represented as Za, Zb, and Zc. Furthermore, the controller 112 is configured to periodically execute the predetermined switching sequence during non-operation periods of the power conversion system. Furthermore, the controller 112 is configured to deactivate all of the plurality of switching elements 106, activate the first switching element to connect the first terminal of the AC load 108 to the DC side, detect insulation failure at the first terminal using the insulation monitoring device 110, deactivate the first switching element, sequentially repeat the activation and detection steps for each remaining terminal of the AC load 108 and determine the overall AC side insulation status based on detection results from all terminals of the AC load 108.
Figure 2, describes a method 200 of monitoring insulation failure on an AC side of a power conversion system using a DC side insulation monitoring device. The method 200 starts at step 202 and completes at step 206. At step 202, the method 200 comprises providing a power conversion system comprising a DC power source 102 having positive and negative terminals, a three-phase inverter 104 comprising a plurality of switching elements 106 and an AC load 108 having multiple terminals connected to the three-phase inverter 104. At step 204, the method 200 implementing a predetermined switching sequence of the plurality of switching elements 106 to selectively connect at least one terminal of the AC load to the DC side. At step 206, the method 200 comprises detecting insulation failure on the AC side using a DC side insulation monitoring device 110.
In an embodiment, the method 200 comprises deactivating all switching elements before implementing the predetermined switching sequence.
In an embodiment, implementing the predetermined switching sequence comprises activating a first switching element to connect a first terminal of the AC load 108 to the DC side, detecting insulation failure at the first terminal using the insulation monitoring device 110, deactivating the first switching element and sequentially repeating the activation and detection steps for each remaining terminal of the AC load 108.
In an embodiment, the method 200 comprises determining an overall AC side insulation status based on detection results from all terminals of the AC load 108.
In an embodiment, the method 200 comprises periodically executing the predetermined switching sequence during non-operation periods of the power conversion system.
In an embodiment, the method 200 comprises detecting an insulation resistance value for each terminal of the AC load 108 and comparing the detected insulation resistance values against a predetermined threshold to determine insulation failure.
It would be appreciated that all the explanations and embodiments of the portable device 100 also applies 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 combination 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”, “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 system (100) for monitoring insulation failure on an AC side of a power conversion system, the system (100) comprising:
- a DC power source (102) having positive and negative terminals;
- a three-phase inverter (104) comprising a plurality of switching elements (106);
- an AC load (108) having multiple terminals connected to the three-phase inverter (104);
- an insulation monitoring device (110) connected to the DC side of the power conversion system; and
- a controller (112) configured to:
- implement a predetermined switching sequence of the plurality of switching elements (106) to selectively connect at least one terminal of the AC load (108) to the DC side; and
- detect insulation failure on the AC side using the DC side insulation monitoring device (110).
2. The system (100) as claimed in claim 1, wherein the three-phase inverter (104) forms three half-bridge circuits connected in parallel between the positive and negative terminals of the DC power source (102).
3. The system (100) as claimed in claim 2, wherein each half-bridge circuit comprises:
- a first switching element connected between the positive terminal of the DC power source (102) and a corresponding AC output terminal; and
- a second switching element connected between the negative terminal of the DC power source (102) and the corresponding AC output terminal.
4. The system (100) as claimed in claim 1, wherein the AC load (108) is a three-phase motor having impedance represented as Za, Zub, and Zc.
5. The system (100) as claimed in claim 1, wherein the controller (112) is configured to periodically execute the predetermined switching sequence during non-operation periods of the power conversion system.
6. The system (100) as claimed in claim 1, wherein the controller (112) is configured to:
- deactivate all of the plurality of switching elements (106);
- activate a first switching element to connect a first terminal of the AC load (108) to the DC side;
- detect insulation failure at the first terminal using the insulation monitoring device (110);
- deactivate the first switching element;
- sequentially repeat the activation and detection steps for each remaining terminal of the AC load (108); and
- determine an overall AC side insulation status based on detection results from all terminals of the AC load (108).
7. A method (200) of monitoring insulation failure on an AC side of a power conversion system, wherein the method (200) comprises:
- providing a power conversion system comprising:
- a DC power source (102) having positive and negative terminals;
- a three-phase inverter (104) comprising a plurality of switching elements (106); and
- an AC load (108) having multiple terminals connected to the three-phase inverter (104);
- implementing a predetermined switching sequence of the plurality of switching elements (106) to selectively connect at least one terminal of the AC load (108) to the DC side; and
- detecting insulation failure on the AC side using a DC side insulation monitoring device (110).
8. The method (200) as claimed in claim 7, wherein the method (200) comprises deactivating all switching elements before implementing the predetermined switching sequence.
9. The method (200) as claimed in claim 7, wherein implementing the predetermined switching sequence comprises:
- activating a first switching element to connect a first terminal of the AC load (108) to the DC side;
- detecting insulation failure at the first terminal using the insulation monitoring device (110);
- deactivating the first switching element; and
- sequentially repeating the activation and detection steps for each remaining terminal of the AC load (108).
10. The method (200) as claimed in claim 7, wherein the method (200) comprises determining an overall AC side insulation status based on detection results from all terminals of the AC load (108).
11. The method (200) as claimed in claim 7, wherein the method (200) comprises periodically executing the predetermined switching sequence during non-operation periods of the power conversion system.
12. The method (200) as claimed in claim 7, wherein the method (200) comprises:
- detecting an insulation resistance value for each terminal of the AC load (108); and
- comparing the detected insulation resistance values against a predetermined threshold to determine insulation failure.