DESC:METHOD FOR MONITORING INSULATION STATE OF ELECTRIC DRIVE
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims priority from Indian Provisional Patent Application No. 202421022016 filed on 21/03/2024, the entirety of which is incorporated herein by a reference.
TECHNICAL FIELD
The present disclosure generally relates to a drive train unit. Particularly, the present disclosure relates to a method for monitoring insulation state of an inverter of a drive train unit.
BACKGROUND
The electric vehicle (EV) market is rapidly expanding, driven by advancements in battery technology, government incentives, 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 be 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 method for monitoring insulation state of an inverter of a drive train unit
In accordance with an aspect of the present disclosure, there is provided a method for monitoring insulation state of an inverter of a drive train unit. The method comprises collecting current signals from a plurality of phase lines of a motor, decomposing intercepted switch high-frequency oscillation current fragment into three sub-modes, calculating change in amount of insulation of a multi-phase capacitor based on the decomposed sub-modes and obtaining amplitude variation of a three-phase high-frequency common mode current at a resonance point.
The present disclosure provides a method of isolation detection for a motor drive of an electric vehicle. The method as disclosed by present disclosure is advantageous in terms of enhanced high-frequency signal analysis techniques. Beneficially, the method enables precise detection of insulation degradation. Furthermore, the method significantly enhances the accuracy in identifying insulation faults. Additionally, the method ensures continuous monitoring and early fault detection, thereby preventing potential failures. Beneficially, the method offers determination of resonance points and amplitude variations which allows for a more comprehensive assessment of insulation integrity. Furthermore, the method improves reliability, while generating alert signals enhances operational safety. Additionally, the method ensures long-term health monitoring.
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 flow chart of a method for monitoring insulation state of an inverter of a drive train unit, in accordance with another aspect 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 method for monitoring insulation state of an inverter of a drive train unit 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 state” refers to the condition or integrity of the electrical insulation within a system, particularly in components such as inverters, motors, or power electronics. The insulation state represents the ability of the insulation to prevent unintended current leakage, short circuits, or breakdowns under operating conditions. The insulation state can be quantitatively assessed using parameters such as insulation resistance, leakage current, dielectric strength, or capacitance variations. Changes in the insulation state may indicate degradation due to thermal stress, electrical stress, aging, contamination, or mechanical wear.
As used herein, the terms “inverter” refers to an electrical device or system configured to convert direct current (DC) into alternating current (AC) at a desired voltage, frequency, and waveform, typically used in applications such as motor control, renewable energy systems, and power conversion. The inverter may include power electronic components, such as insulated gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs), along with control circuitry to regulate power output, switching frequency, and operational efficiency. The inverter may further incorporate protection mechanisms for insulation monitoring, fault detection, and thermal management to ensure reliable operation in various environmental and load conditions.
As used herein, the term “drive train unit” refers to a system comprising one or more components that transmit mechanical power from a power source, such as an internal combustion engine or an electric motor, to a driven load, such as vehicle wheels or an industrial machine. The drive train unit typically includes an inverter, motor, transmission, differential, and associated control systems that facilitate the conversion and transfer of energy for propulsion or operation.
As used herein, the term “current signals” refers to electrical signals representing the flow of electric current in a circuit or conductor, characterized by parameters such as magnitude, frequency, phase, and waveform, which can be measured, processed, and analyzed to determine electrical characteristics or system conditions.
As used herein, the term “plurality of phase lines” refers to two or more electrical conductors that may carry the phase currents to or from a multi-phase motor, wherein each phase line corresponds to a distinct phase of the motor and facilitates power transmission between the inverter and the motor.
As used herein, the term “multi-phase capacitor” refers to a capacitor electrically coupled to multiple phase lines of a multi-phase electrical system, configured to store and distribute electrical energy among the phases. The multi-phase capacitor may function to manage voltage fluctuations, filter high-frequency noise, or provide insulation monitoring by interacting with phase currents. It can be implemented using discrete capacitor elements connected in a specific configuration, such as a star or delta arrangement, to facilitate balanced operation across the phases of an inverter or motor drive system.
As used herein, the term “resonance point” refers to a specific frequency at which the impedance characteristics of an electrical system, such as an inverter or motor drive circuit, result in a significant amplification of certain electrical signals, particularly common mode currents. The resonance point occurs due to the interaction of inductive and capacitive elements within the system, leading to a peak response in the frequency spectrum. The resonance point is utilized for analyzing insulation state variations and detecting potential insulation faults by assessing amplitude variations at this frequency.
As used herein, the term “plurality of current sensors” and “current sensors” are used interchangeably and refer to a device or system configured to detect, measure, and monitor an electric current flowing through a conductor, circuit, or electrical component. The current sensor generates the output signal corresponding to the magnitude and direction of the current, which can be further processed for control, monitoring, or protection purposes. The sensor may operate based on various principles, including but not limited to electromagnetic induction, Hall effect, resistive shunt measurement, fluxgate technology, or Rogowski coil-based sensing.
As used herein, the term “differential mode” refers to the condition where electrical signals or currents flow in opposite directions through a pair of conductors, typically in a balanced manner. In a multi-phase system, differential mode currents represent the normal operating currents that drive the motor, where the sum of the phase currents is ideally zero. The differential mode analysis is commonly used to study signal integrity, noise characteristics, and fault detection in electrical circuits. For insulation monitoring, differential mode currents provide insights into variations in phase-to-phase insulation by isolating components from common mode and zero-sequence disturbances.
As used herein, the term “common mode” refers to a condition in an electrical system where signals or currents in multiple conductors exhibit substantially the same amplitude and phase relative to a common reference, typically ground. In power electronics and motor drive systems, common mode currents or voltages refer to unwanted signals that propagate through parasitic capacitances and can lead to electromagnetic interference (EMI), insulation degradation, or malfunction of sensitive components.
As used herein, the term “zero-sequence mode” refers to a specific current or voltage component in a multi-phase electrical system, where all phase conductors carry identical magnitude and phase signals. In a three-phase system, zero-sequence components arise when the sum of the three-phase currents or voltages is nonzero, typically due to an imbalance or grounding faults.
As used herein, the term “at least one of wavelet transform” refers to a signal processing technique that decomposes a signal into components of different frequency bands using wavelet functions. The wavelet transform enables analysis of transient, non-stationary, and high-frequency components of signals, facilitating time-frequency localization for detecting insulation faults in an inverter system.
As used herein, the term “Fourier transform” refers to computational method that converts a time-domain signal into its constituent frequency components, enabling analysis of signal characteristics in the frequency domain. The Fourier Transform is applied to process high-frequency current signals, extract harmonic content, and identify patterns indicative of insulation degradation in electrical systems.
As used herein, the term “eigenvalue decomposition” refers to a mathematical technique used to decompose a matrix into its constituent eigenvalues and eigenvectors. In the signal processing, eigenvalue decomposition is employed to analyze system characteristics by transforming a given matrix into a diagonal form, where the eigenvalues represent fundamental properties of the system, such as signal energy distribution or dominant modes of variation.
As used herein, the term “alert signal” refers to an electrical, visual, audible, or communication-based signal generated in response to a detected condition, such as an isolation fault, to notify a control system, operator, or external monitoring unit for initiating corrective action or further diagnosis.
As used herein, the term “memory” refers to any device, component, or system capable of storing data, instructions, or reference values for retrieval and processing. The volatile memory (e.g., RAM) or non-volatile memory (e.g., ROM, flash memory, EEPROM, hard drives) and may be integrated within a processing unit or exist as an external storage medium. In the context of an invention, memory is often used to store reference values, historical data, algorithms, or parameters necessary for executing specific functions, such as comparing insulation values in an electrical system or retaining baseline operational data for fault detection and system optimization.
As used herein, the term “predetermined threshold” refers to a predefined value, range, or condition set as a reference for evaluating a parameter or triggering a specific action. The predetermined threshold can be established based on empirical data, experimental results, industry standards, or system requirements and is used to determine when a certain response, such as generating an alert or adjusting system parameters, is necessary.
As used herein, the term “frequency sweep” refers to a process in which the frequency of an applied signal is varied systematically over a defined range to analyze the system’s response at different frequencies. The frequency sweep may be used to identify resonance points, characterize impedance variations, or detect anomalies in electrical systems.
As used herein, the term “insulation fault” refers to a condition in an electrical system where the insulating material between conductive components deteriorates or fails, leading to unintended current leakage, reduced dielectric strength, or short-circuit conditions. Such faults may result from environmental factors, thermal stress, electrical overstress, mechanical damage, or aging of the insulation material, potentially affecting system performance, safety, and reliability.
As used herein, the term “baseline insulation state” refers to an initial reference value or a set of reference parameters that characterize the insulation condition of an inverter within a drive train unit under normal or optimal operating conditions. The baseline insulation state is established during an initialization phase by measuring and storing insulation-related parameters, such as leakage currents, insulation resistance, or high-frequency common mode current characteristics, in a memory.
As used herein, the term “initialization phase” refers to the initial operational stage of a system, device, or method during which baseline parameters, reference values, or default settings are established before normal operation begins. This phase ensures that the system is properly configured, calibrated, or adapted to its operating environment.
Figure 1 describes a method 100 for monitoring insulation state of an inverter of a drive train unit. The method 100 starts at step 102 and completes at step 108. At step 102, the method 100 comprises collecting current signals from a plurality of phase lines of a motor. At step 104, the method 100 comprises decomposing intercepted switch high-frequency oscillation current fragment into three sub-modes. At step 106, the method 100 comprises calculating change in amount of insulation of a multi-phase capacitor based on the decomposed sub-modes. At step 108, the method 100 obtaining amplitude variation of a three-phase high-frequency common mode current at a resonance point.
The present disclosure provides a method 100 for monitoring insulation state of an inverter of a drive train unit. The method 100 as disclosed by present disclosure is advantageous in terms of enhanced reliability, accuracy, and efficiency of insulation fault detection. Beneficially, by collecting the current signals from the multiple phase lines using the current sensors, the method 100 ensures the real-time monitoring of insulation degradation without requiring additional intrusive components. Beneficially, the decomposition of high-frequency oscillation current fragments into differential, common-mode, and zero-sequence sub-modes allows for precise analysis of the insulation behavior, thereby improving the fault localization. Beneficially, the use of advanced signal processing techniques such as wavelet transform, Fourier transform, or eigenvalue decomposition enhances the ability to distinguish the insulation faults from the normal variations, thereby ensures higher sensitivity and accuracy. Beneficially, comparing the present insulation values with reference values enables early detection of insulation deterioration, preventing failures before the insulation values become critical. Furthermore, the generation of an alert signal when insulation degradation surpasses a threshold significantly improves the system safety and enables predictive maintenance. Furthermore, measuring amplitude variations at a resonance point and determining the resonance frequency through a frequency sweep provides a robust mechanism to quantify insulation degradation dynamically. Additionally, the capability to locate insulation faults based on the relative amplitudes of sub-modes enhances diagnostic precision, which further reduces the downtime and maintenance costs. Additionally, the method 100 also compensates for temperature variations, ensuring stable insulation assessment under different operating conditions.
In an embodiment, collecting the current signals comprises measuring currents using a plurality of current sensors connected to the plurality of phase lines. The current sensors may be strategically positioned to capture the real-time current variations in each phase line, enable high-resolution monitoring of the insulation conditions. The current sensors may include Hall-effect sensors, Rogowski coils, or shunt resistors, depending on the required sensitivity and bandwidth. The measured current signals serve as the input for further signal processing, where high-frequency oscillation fragments are extracted and analyzed. By directly interfacing with the motor phase lines, the current sensors ensure accurate data acquisition without interfering with the normal operation of the drive train unit.
In an embodiment, decomposing the intercepted switch high-frequency oscillation current fragment comprises applying a signal processing technique to separate the high-frequency current into differential mode, common mode, and zero-sequence mode components. Furthermore, the signal processing technique comprises at least one of: wavelet transform, Fourier transform, or eigenvalue decomposition. The signal processing technique may include wavelet transform, Fourier transform, or eigenvalue decomposition, each offers the unique advantages in isolating frequency-domain and time-domain characteristics of the insulation-related current oscillations. The differential mode component represents the current flowing between the phase lines, providing insight into phase-to-phase insulation conditions. The common mode component indicates leakage currents related to ground insulation health, while the zero-sequence mode component helps in identifying asymmetrical insulation degradation. Beneficially, by decomposing the high-frequency oscillation current fragment into these distinct sub-modes, the method 100 enhances the accuracy of the insulation fault detection which allows the targeted analysis of specific degradation patterns.
In an embodiment, calculating the change in amount of insulation comprises comparing present insulation values with reference insulation values stored in a memory. Furthermore, the method 100 comprises generating an alert signal when the calculated change in amount of insulation exceeds a predetermined threshold. During an initialization phase, the system establishes the baseline insulation state by capturing insulation parameters under normal operating conditions. The reference insulation values are stored in the memory, which may be part of the inverter control unit, a dedicated monitoring module, or an external data storage system. If the computed deviation exceeds a predefined threshold, the system identifies the potential insulation degradation and may trigger the alert signal, notifying the operator or initiating corrective actions such as adjusting operating parameters or scheduling maintenance. To enhance accuracy, the comparison process compensates for environmental factors, such as temperature variations, that could influence insulation measurements. Beneficially, the approach ensures the precise, real-time tracking of the insulation degradation, enables the predictive maintenance and enhancing the reliability and safety of the drive train unit.
In an embodiment, obtaining the amplitude variation comprises measuring the amplitude of the three-phase high-frequency common mode current at a specific frequency corresponding to the resonance point. The method 100 measures the amplitude of the three-phase high-frequency common mode current at the resonance point. The resonance frequency may be determined based on the system parameters, such as the stray capacitance of the motor windings and the impedance of the inverter circuit. The amplitude variation at the resonance point serves as the key indicator of insulation degradation, as changes in insulation integrity affect the capacitive coupling and alter the resonance characteristics. Beneficially, by continuously monitoring the amplitude at the resonance frequency, the method 100 provides the highly sensitive approach to detecting insulation deterioration.
In an embodiment, the method 100 comprises determining the resonance point by performing a frequency sweep of the three-phase high-frequency common mode current. The process involves the injecting the controlled high-frequency excitation signal into the drive system and systematically varying the frequency over a predefined range. During the frequency sweep, the amplitude of the high-frequency common mode current is continuously measured at multiple frequency points using current sensors placed on the phase lines. The resonance point may be identified as the frequency at which the amplitude of the common mode current exhibits the peak response, indicating the natural resonance characteristic of the system insulation network. Beneficially, the approach provides the precise method 100 for characterizing insulation degradation, as changes in insulation properties cause shifts in the resonance frequency and amplitude response.
In an embodiment, the method 100 comprises determining a location of insulation fault based on relative amplitudes of the three sub-modes. To determine the fault location, the method 100 measures and compares the relative amplitudes of the decomposed sub-modes at specific monitoring points. If the insulation fault occurs closer to the particular phase line, the differential mode component may exhibit a more significant amplitude shift compared to the common mode or zero-sequence mode. Conversely, if the insulation degradation may be distributed across multiple phases or occurs in the DC-link, the common mode component may show a pronounced increase in amplitude.
In an embodiment, the method 100 comprises compensating for temperature variations in the inverter when calculating the change in amount of insulation. The temperature variations may be significantly affecting the insulation properties of the electrical components, leads to erroneous readings if not accounted for. To address the issue, the system incorporates temperature sensors positioned within the inverter and the drive train unit to continuously monitor temperature fluctuations. The collected temperature data may be processed and used to adjust the insulation measurement parameters accordingly. Beneficially, by integrating the temperature compensation in the insulation monitoring process, the method 100 enhances the accuracy, reliability, and robustness of the insulation assessment in varying operational environments of the drive train unit.
In an embodiment, the method 100 comprises establishing a baseline insulation state during an initialization phase and monitoring deviation from the baseline insulation state during normal operation of the drive train unit. Once the baseline insulation state may be established, the system transitions to normal operation, where the system continuously monitors the insulation condition by comparing the real-time insulation measurements with the stored baseline values. The changes in the insulation state may be detected by analyzing deviations in the decomposed high-frequency modes. If the deviation exceeds the predetermined threshold, the alert signal is generated to indicate potential insulation degradation or failure. Additionally, the system may compensate for temperature variations and other environmental factors to ensure accurate insulation assessment. By dynamically tracking the insulation condition, the method 100 enhances the reliability, safety, and longevity of the drive train unit, enabling predictive maintenance and minimizing unexpected failures.
In an embodiment, the method 100 comprises adjusting operating parameters of the drive train unit based on the monitored insulation state. The method 100 starts by collecting current signals from the plurality of phase lines of the motor using current sensors. The signals may be processed to extract high-frequency oscillation current fragments, which may be then decomposed into three sub-modes differential mode, common mode, and zero-sequence mode. The change in insulation amount of a multi-phase capacitor may be then calculated based on the decomposed sub-modes, and the amplitude variation of the three-phase high-frequency common mode current at a resonance point is obtained. Based on the calculated change in insulation state, the method 100 determines whether the insulation degradation has reached the critical level. If the change in insulation state exceeds a predefined threshold, the method 100 dynamically adjusts operating parameters of the drive train unit to mitigate potential risks. The adjustments may include modifying switching frequencies of the inverter, reducing motor drive voltage, adjusting pulse width modulation (PWM) control strategies, or limiting current flow to reduce electrical stress on insulation materials. In cases where insulation degradation may be progressing gradually, the system may also implement derating strategies to extend the operational life of the inverter and motor. Additionally, the method 100 may incorporate an adaptive control loop that continuously monitors insulation trends over time and predicts potential failures using historical insulation data. The adaptive control loop enables predictive maintenance by notifying operators of potential insulation issues before the failure occurs. The system may further refine control parameters in real-time which ensures optimal performance of the drive train unit while maintaining electrical safety.
In an embodiment, the method 100 for monitoring insulation state of the inverter of the drive train unit. The method 100 starts at step 102 and completes at step 108. At step 102, the method 100 comprises collecting current signals from the plurality of phase lines of the motor. At step 104, the method 100 comprises decomposing intercepted switch high-frequency oscillation current fragment into three sub-modes. At step 106, the method 100 comprises calculating change in amount of insulation of the multi-phase capacitor based on the decomposed sub-modes. At step 108, the method 100 obtaining amplitude variation of the three-phase high-frequency common mode current at the resonance point. Furthermore, collecting the current signals comprises measuring currents using the plurality of current sensors connected to the plurality of phase lines. Furthermore, decomposing the intercepted switch high-frequency oscillation current fragment comprises applying the signal processing technique to separate the high-frequency current into differential mode, common mode, and zero-sequence mode components. Furthermore, the signal processing technique comprises the at least one of wavelet transform, Fourier transform, or eigenvalue decomposition. Furthermore, calculating the change in amount of insulation comprises comparing present insulation values with reference insulation values stored in the memory. Furthermore, the method 100 comprises generating the alert signal when the calculated change in amount of insulation exceeds the predetermined threshold. Furthermore, obtaining the amplitude variation comprises measuring the amplitude of the three-phase high-frequency common mode current at the specific frequency corresponding to the resonance point. Furthermore, the method 100 comprises determining the resonance point by performing the frequency sweep of the three-phase high-frequency common mode current. Furthermore, the method 100 comprises determining the location of insulation fault based on relative amplitudes of the three sub-modes. Furthermore, the method 100 comprises compensating for temperature variations in the inverter when calculating the change in amount of insulation. Furthermore, the method 100 comprises establishing the baseline insulation state during an initialization phase and monitoring deviation from the baseline insulation state during normal operation of the drive train unit. Furthermore, the method 100 comprises adjusting operating parameters of the drive train unit based on the monitored insulation state.
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 method (100) for monitoring insulation state of an inverter of a drive train unit, wherein the method (100) comprises:
- collecting current signals from a plurality of phase lines of a motor;
- decomposing intercepted switch high-frequency oscillation current fragment into three sub-modes;
- calculating change in amount of insulation of a multi-phase capacitor based on the decomposed sub-modes; and
- obtaining amplitude variation of a three-phase high-frequency common mode current at a resonance point.
2. The method (100) as claimed in claim 1, wherein collecting the current signals comprises measuring currents using a plurality of current sensors connected to the plurality of phase lines.
3. The method (100) as claimed in claim 1, wherein decomposing the intercepted switch high-frequency oscillation current fragment comprises applying a signal processing technique to separate the high-frequency current into differential mode, common mode, and zero-sequence mode components.
4. The method (100) as claimed in claim 3, wherein the signal processing technique comprises at least one of wavelet transform, Fourier transform, or eigenvalue decomposition.
5. The method (100) as claimed in claim 1, wherein calculating the change in amount of insulation comprises comparing present insulation values with reference insulation values stored in a memory.
6. The method (100) as claimed in claim 1, wherein the method (100) comprises generating an alert signal when the calculated change in amount of insulation exceeds a predetermined threshold.
7. The method (100) as claimed in claim 1, wherein obtaining the amplitude variation comprises measuring the amplitude of the three-phase high-frequency common mode current at a specific frequency corresponding to the resonance point.
8. The method (100) as claimed in claim 7, wherein the method (100) comprises determining the resonance point by performing a frequency sweep of the three-phase high-frequency common mode current.
9. The method (100) as claimed in claim 1, wherein the method (100) comprises determining a location of insulation fault based on relative amplitudes of the three sub-modes.
10. The method (100) as claimed in claim 1, wherein the method (100) comprises compensating for temperature variations in the inverter when calculating the change in amount of insulation.
11. The method (100) as claimed in claim 1, wherein the method (100) comprises:
- establishing a baseline insulation state during an initialization phase; and
- monitoring deviation from the baseline insulation state during normal operation of the drive train unit.
12. The method (100) as claimed in claim 1, wherein the method (100) comprises adjusting operating parameters of the drive train unit based on the monitored insulation state.