Motor driving system and IGBT (Insulated Gate Bipolar Translator) state monitoring method and monitoring system thereof

Abstract

The invention provides a motor driving system and an IGBT state monitoring method and monitoring system thereof, and the IGBT state monitoring method of the motor driving system is based on bus current measurement, and comprises the steps: obtaining the operation data of the motor driving system, including the bus current and each bridge arm driving signal; at each sampling moment, decomposing the measured bus current to each conducted IGBT by combining a bridge arm driving signal, and reconstructing the collector current Ic of each bridge arm; extracting the turn-off delay of each IGBT by using the reconstructed collector current Ic of each bridge arm; establishing a relationship between turn-off delay and temperature, and extracting junction temperature information by using the turn-off delay; and the IGBT with abnormal junction temperature is positioned, and the state of the IGBT is monitored in real time. According to the invention, through the single current sensor and analysis of the sequential relationship between the bus current waveform characteristics and the driving signals, effective reconstruction of the collector current Ic of the IGBT device in each bridge arm of the three-phase inverter is realized, and then detection and timely protection of abnormal turn-off of the switching device are realized.

Description

Technical Field

[0001] This invention belongs to the field of power electronic device health monitoring technology, specifically, it relates to a motor drive system and a method and system for monitoring the IGBT status of the motor drive system based on bus current measurement. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) are widely used in industrial automation and new energy vehicles due to their high efficiency and high power density. The three-phase inverter, the core component of its drive system, consists of multiple insulated-gate bipolar transistor (IGBT) devices. However, IGBT devices are susceptible to changes in their state during long-term operation due to factors such as high temperature, voltage stress, and current surges. These changes can manifest as slower switching speeds, increased on-resistance, or even complete device failure, ultimately affecting the reliability and stability of the entire motor system.

[0003] In existing technologies, there are many types of condition monitoring technologies for insulated gate bipolar transistors (IGBTs), including electrical parameter monitoring, thermal monitoring, vibration monitoring, and optical monitoring. Condition monitoring based on electrical parameters is currently the most mainstream research direction, primarily determining the health status of the device by monitoring changes in specific parameters during switching.

[0004] On-state voltage drop (V CE(on) This can accurately reflect the health status of the IGBT. Device aging (such as bond wire degradation) will lead to an increase in its impedance, which in turn will cause V to... CE(on) It increases under the same current. However, this monitoring method in the prior art is highly invasive, directly measuring V. CE(on) A voltage sensor and complex isolation sampling circuitry need to be connected in parallel across the collector and emitter of each IGBT module, which significantly increases hardware cost, size, and wiring complexity in bridge arms composed of multiple IGBTs. Furthermore, for highly integrated power modules, their internal pins are typically not directly exposed, making it impossible to directly obtain the V signal of a single IGBT from the outside. CE(on) Secondly, V CE(on) It is very sensitive to junction temperature, and precise temperature compensation is required when making state judgments, otherwise misjudgments are easy to occur.

[0005] The switching transients of IGBTs can reflect IGBT performance degradation. For example, gate oxide aging alters the threshold voltage Vth and Miller capacitance, thus affecting the maximum voltage / current change rate (dv / dt, di / dt). Switching processes occur on the nanosecond to microsecond scale, and accurately capturing the dynamic characteristics of multiple IGBT modules requires costly measurement equipment with multiple high-precision probes and extremely high sampling rates and bandwidths. However, compared to the on-state voltage drop (Vth), the switching transients can significantly impact performance. CE(on) Similar to other monitoring methods, it also faces the difficulty of accessing internal measurement points within integrated modules.

[0006] Parameters of the gate circuit, such as the gate threshold voltage V. th and Miller plateau voltage V GP These parameters are also related to the health status of the device. However, the changes in these parameters are very small in the early stages of aging, resulting in a low signal-to-noise ratio. This places extremely high demands on the accuracy and anti-interference capabilities of the measurement circuit, and they are also affected by the cross-effects of junction temperature.

[0007] Indirect monitoring methods based on system-level external variables avoid direct measurement of the devices themselves, instead analyzing system-level electrical signals. These methods are less invasive, but location and sensitivity remain their main challenges. When an IGBT in an inverter experiences an open circuit or severe degradation, it disrupts the symmetry of the three-phase output current. This anomaly is reflected in the DC bus current or phase current as specific harmonics. However, while most system variable-based methods can detect system faults, they struggle to pinpoint the exact IGBT, hindering subsequent maintenance. Furthermore, these methods respond strongly to "hard faults" like open circuits and short circuits, but for early, gradual performance degradation, the characteristics generated by these faults on system-level variables are very weak and easily masked by normal operating disturbances such as motor load fluctuations and speed changes, leading to missed or false alarms. Secondly, some solutions attempt to reconstruct the three-phase current using a single DC bus current sensor. However, in certain switching vector states of the inverter (such as during zero vector periods or sector boundaries), the phase current cannot be independently observed, resulting in a blind zone in the reconfiguration and limiting the applicability of this method across all operating conditions.

[0008] Therefore, developing a non-invasive, online IGBT aging detection method is of great significance. Currently, no descriptions or reports of similar technologies have been found, and no similar domestic or international materials have been collected. Summary of the Invention

[0009] To address the aforementioned shortcomings in the prior art, this invention provides a motor drive system and its IGBT status monitoring method and system.

[0010] According to a first aspect of the present invention, a method for monitoring the condition of an IGBT in a motor drive system based on bus current measurement is provided, comprising: Acquire runtime data of the motor drive system, including bus current and drive signals of each bridge arm; At each sampling moment, the measured bus current is decomposed onto each conducting IGBT in conjunction with the bridge arm drive signal, and the collector current I of each bridge arm is determined. c Refactor; Using the reconstructed collector current I of each bridge arm c Extract the turn-off delay of each IGBT; Establish the relationship between the turn-off delay and temperature, and extract junction temperature information using the turn-off delay; Locate IGBTs with abnormal junction temperatures and monitor their status in real time.

[0011] Preferably, acquiring the runtime data of the motor drive system includes: A single current sensor is installed on the DC bus to collect the bus current I in real time. dc The sampling frequency of the single current sensor is such that it can capture waveform details within the PWM cycle. The PWM drive signals output by the DSP for each bridge arm are recorded to determine the switching state; wherein, the PWM drive signals include the turn-on and turn-off timing of each bridge arm.

[0012] Preferably, at each sampling time, the measured bus current is decomposed onto each conducting IGBT in conjunction with the bridge arm drive signal, and the collector current I of each bridge arm is determined. c Refactoring includes: Combining the switching timing of the IGBT drive signals of each bridge arm and the bus current fluctuation ΔI dc The polarity is used to determine the direction of the output phase current, and the IGBT device causing the fluctuation is located by the bus current fluctuation and the direction of the phase current. The bus current is then decomposed into each conducting IGBT. The collector current at each moment in the timing diagram is reconstructed. With only one bridge arm conducting, the bus current ΔI during state transition is analyzed. dc The polarity of the bus current is determined, and the value is assigned to the collector current of the IGBT in that branch after considering the polarity (positive or negative), thus obtaining the collector current I of the corresponding bridge arm. c Under steady-state conditions where multiple bridge arms are simultaneously conducting, the bus current is the algebraic sum of the currents in the conducting branches. By combining Kirchhoff's current law and phase current constraints, the collector current I of the bridge arm can be obtained. c .

[0013] Preferably, the method of utilizing the reconstructed collector current I of each bridge armc Extract the turn-off delay of each IGBT, including: Based on the reconstructed collector current I of each bridge arm c The turn-off process of each IGBT is monitored in real time. With driving voltage U GE The trailing edge of the pulse falls to a set ratio a (i.e., aV) of its amplitude. GE The time from which the collector current drops to a set proportion b of its amplitude (i.e., bI) is reached. CM The time of shutdown is used as the reference point for calculating the shutdown delay; Based on the reference point calculated by the turn-off delay, the negative transition moment of the bus current under the action of the drive signal is captured, which corresponds to the bridge arm collector current I. c At the moment of descent, extract the turn-off delay of each IGBT.

[0014] Preferably, establishing the relationship between the turn-off delay and temperature, and extracting junction temperature information using the turn-off delay, includes: During the offline calibration phase, for the specific health IGBT device model to be monitored, the temperature T set in the constant temperature chamber is used as the junction temperature T. j Under these conditions, the turn-off delay t of the IGBT is measured with a fixed interval ΔT as the step size. d(off) The measurement data was organized and a t was established. d(off) -T j Mathematical model; Real-time acquisition of collector current I of each bridge arm within N PWM cycles c and the drive signals of each bridge arm to obtain the device's turn-off delay time, for the t d(off) -T j The mathematical model is dynamically updated to extract junction temperature information in real time.

[0015] Preferably, the location of the IGBT with abnormal junction temperature includes real-time monitoring of the IGBT status, comprising: Within the PWM cycle that meets the monitoring standards, the turn-off delay time t is extracted through analysis. d(off) Estimate the junction temperature T of the IGBT device j And calculate the junction temperature T. j The degree of deviation from the reference value is used to identify IGBT devices with abnormal conditions and to monitor the IGBT status in real time.

[0016] According to a second aspect of the present invention, a motor drive system IGBT condition monitoring system based on bus current measurement is provided, comprising: The data acquisition module is used to acquire runtime data of the motor drive system, including bus current and drive signals of each bridge arm; The bridge arm collector current reconstruction module is used to decompose the measured bus current into each conducting IGBT at each sampling time, in conjunction with the bridge arm drive signal, and reconstruct the collector current I of each bridge arm. c Refactor; The junction temperature information extraction module utilizes the reconstructed collector current I of each bridge arm. c Extract the turn-off delay of each IGBT; establish the relationship between the turn-off delay and temperature, and use the turn-off delay to extract junction temperature information; The status monitoring module is used to locate IGBTs with abnormal junction temperatures and monitor the IGBT status in real time.

[0017] According to a third aspect of the present invention, a motor drive system is provided, which uses the method described in any one of the above-mentioned invention to realize IGBT status monitoring.

[0018] By adopting the above technical solution, the present invention has at least one of the following beneficial effects compared with the prior art: The motor drive system and IGBT status monitoring method and system provided by this invention reconstruct the collector current of each IGBT device in a three-phase inverter using a single current sensor, and estimate the junction temperature based on the turn-off delay time to evaluate the device status. No additional circuit is needed to measure the IGBT current. The current behavior of each IGBT when it is turned off can be obtained in each PWM cycle using only the existing bus current sensing and drive signal, thereby realizing the detection and timely protection of abnormal turn-off of switching devices.

[0019] The motor drive system and IGBT status monitoring method and system provided by the present invention achieve health monitoring of multiple IGBT devices by using only one current sensor to sample the bus current and combining it with synchronous analysis of the drive signal. This significantly reduces system cost and complexity and is more economical and efficient than traditional methods that require configuring a sensor for each device.

[0020] The motor drive system and IGBT status monitoring method and system provided by the present invention utilize the timing correlation between bus current analysis and PWM drive signal to reconstruct the collector current of each bridge arm IGBT. By continuously monitoring multiple PWM cycles, the turn-off parameters of the non-reconstruction blind zone can be selected, thereby achieving accurate monitoring of individual devices.

[0021] The motor drive system and IGBT status monitoring method and system provided by the present invention analyze the reconstructed collector current waveform, extract the IGBT turn-off delay characteristics based on the turn-off delay to estimate the IGBT junction temperature, and use its aging-related characteristics as a reliable indicator to judge the health status of the device, thereby improving the accuracy of fault early warning.

[0022] The motor drive system and IGBT status monitoring method and system provided by this invention are particularly suitable for IGBT devices in three-phase inverters. They can identify and locate faulty devices in real time during system operation, improving the reliability and maintenance efficiency of power electronic systems. They are especially suitable for scenarios with high reliability requirements, such as electric vehicles and renewable energy systems. Attached Figure Description

[0023] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the topology of a motor drive system in a preferred embodiment of the present invention. In the diagram, GA+ represents the upper arm drive signal of phase A, GA- represents the lower arm drive signal of phase A, GB+ represents the upper arm drive signal of phase B, GB- represents the lower arm drive signal of phase B, GC+ represents the upper arm drive signal of phase C, and GC- represents the upper arm drive signal of phase C. V1 ~ V6 These are the IGBT devices for each bridge arm. VD1 ~ VD6 These are the diodes connected in anti-parallel to each IGBT. U d DC power supply I dc This represents the bus current.

[0024] Figure 2 This is a flowchart illustrating the IGBT status monitoring method for a motor drive system based on bus current in a preferred embodiment of the present invention.

[0025] Figure 3 This is a flowchart of the IGBT status monitoring system for a motor drive system based on bus current, according to a preferred embodiment of the present invention.

[0026] Figure 4 This is a timing diagram of bus current and drive signals in a specific application example of the present invention, taking the first sector as an example. In the diagram, GA+ is the drive signal of the upper bridge arm of phase A, and the drive signal of the lower bridge arm is the opposite (or a dead time is introduced); GB+ is the drive signal of the upper bridge arm of phase B, and the drive signal of the lower bridge arm is the opposite (or a dead time is introduced); GC+ is the drive signal of the upper bridge arm of phase C, and the drive signal of the lower bridge arm is the opposite (or a dead time is introduced).

[0027] Figure 5 In a specific application example of the present invention, I dc Decomposed into the collector current I of each bridge arm c The corresponding bridge arm anti-parallel diode current I VD And the timing diagram corresponding to the shutdown delay extraction.

[0028] Figure 6 The diagram shows the driving voltage and collector current waveforms of the IGBT device during turn-off in a specific application example of this invention, along with the turn-off delay time t. off 0.9V GE up to 0.9I c A timeline of events.

[0029] Figure 7 Figures (a) to (g) are schematic diagrams of the driving signal, bus current and monitored collector current in a specific application example of the present invention.

[0030] Figure 8 Figures (a) to (c) are schematic diagrams of the collector currents of V1, V4, and V6 directly measured in the simulation software in a specific application example of the present invention.

[0031] Figure 9 Figures (a) to (d) are schematic diagrams of the turn-off delay of each device obtained directly from the bus current in a specific application example of the present invention.

[0032] Figure 10 Figures (a) to (f) show a comparison between the simulated and measured collector current and the reconstructed collector current in a specific application example of the present invention.

[0033] Figure 11 Figures (a) to (g) show the bus current and reconstructed collector current waveforms in a specific application example of the present invention, under normal conditions and in scenarios where devices V1, V4, and V6 are aging (abnormal state), respectively, verifying the fault diagnosis and location capabilities of the proposed method. Detailed Implementation

[0034] The embodiments of the present invention are described in detail below: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

[0035] In existing technologies, IGBT aging detection typically relies on additional sensors (such as temperature sensors and voltage probes) or offline testing, which suffers from high cost, poor real-time performance, and increased system complexity. For highly integrated power modules, their internal pins are usually not directly exposed, making it impossible to directly obtain the electrical parameters of a single IGBT from the outside. Some methods indirectly determine aging by monitoring the on-state voltage drop or switching losses, but this is difficult to accurately locate the faulty bridge arm and is susceptible to fluctuations in motor load. Furthermore, traditional methods do not fully utilize the timing correlation between the inverter drive signal and the bus current, resulting in insufficient detection sensitivity.

[0036] To address the aforementioned problems, the present invention provides a motor drive system and a method and system for monitoring the IGBT status of the motor drive system based on bus current measurement. This belongs to a technology for reconstructing the collector current of each IGBT device in each bridge arm using a single current sensor and for evaluating the device status by extracting junction temperature information based on the device turn-off delay time. Given the limited number of externally accessible pins in highly integrated IGBT modules and the high cost of high-precision sensors, this invention utilizes easily obtainable drive signals from each bridge arm and bus current signals acquired through a single high-precision current probe to detect the IGBT status. By analyzing the waveform characteristics of the bus current and combining it with the PWM drive signal, the collector current IC of each IGBT device in the three-phase inverter is reconstructed. c This method extracts the turn-off delay time of each device, thereby enabling IGBT device status identification and location. It is particularly suitable for online status identification and location of IGBT devices in highly integrated three-phase inverter modules.

[0037] like Figure 1 As shown, one embodiment of the present invention provides a motor drive system, which may include: a three-phase inverter, a bus current sensor, a drive signal voltage sensor, a PWM controller, and a motor load; wherein: The three-phase inverter is composed of multiple IGBTs, which form the upper and lower bridge arms of the three phases A, B, and C respectively. Each IGBT is connected to the corresponding PWM controller through an independent drive circuit to receive the drive signal from the PWM controller. The bus current sensor, installed on the DC bus side, is used to measure the DC bus current I in real time. dc This sensor is a high-precision single-current sensor that can capture rapid current changes within a PWM cycle.

[0038] Drive signal voltage sensors are installed on the gate signal lines of each IGBT to measure the drive voltage signal of each IGBT in real time.

[0039] By controlling the on / off timing of multiple IGBTs through a PWM controller, the DC power is inverted into three-phase AC power with specific amplitude and frequency, realizing the DC to three-phase AC conversion to power the motor load.

[0040] The motor drive system provided in this embodiment can be monitored using the IGBT status monitoring method for motor drive systems based on bus current measurement provided in the following embodiments of the present invention.

[0041] Based on the above topology, one embodiment of the present invention provides a method for monitoring the IGBT status of a motor drive system based on bus current measurement.

[0042] Specifically, such as Figure 2 As shown, the IGBT status monitoring method for a motor drive system based on bus current measurement provided in this embodiment may include: S1, acquire the running data of the motor drive system, including bus current and drive signals of each bridge arm; S2, at each sampling moment, the measured bus current is decomposed into each conducting IGBT in conjunction with the bridge arm drive signal, and the collector current I of each bridge arm is calculated. c Refactor; S3, utilizing the reconstructed collector currents I of each bridge arm c Extract the turn-off delay of each IGBT; S4, establish the relationship between turn-off delay and temperature, and extract junction temperature information using the turn-off delay; S5 locates IGBTs with abnormal junction temperatures and monitors their status in real time.

[0043] In some preferred embodiments, the above-mentioned S1, acquiring the runtime data of the motor drive system, may further include: S11, a single current sensor is installed on the DC bus to collect the bus current I in real time. dc Among them, the sampling frequency of the single current sensor is sufficient to capture waveform details within the PWM cycle; S12, record the PWM drive signal output by the DSP for each bridge arm to determine the switching state; wherein, the PWM drive signal includes the turn-on and turn-off timing of each bridge arm.

[0044] In some preferred embodiments, in S2 above, at each sampling time, the measured bus current is decomposed onto each conducting IGBT in conjunction with the bridge arm drive signal, and the collector current I of each bridge arm is... c Restructuring can further include: S21, combining the switching timing of the IGBT drive signals of each bridge arm and the bus current fluctuation ΔI dc The polarity is used to determine the direction of the output phase current, and the IGBT device causing the fluctuation is located by the bus current fluctuation and the direction of the phase current, and the bus current is decomposed to each conducting IGBT. S22, reconstruct the collector current at each moment in the timing diagram. With only one bridge arm conducting, analyze the bus current ΔI during state transitions. dc The polarity of the bus current is determined, and the value is assigned to the collector current of the IGBT in that branch after considering the polarity (positive or negative), thus obtaining the collector current I of the corresponding bridge arm. c Under steady-state conditions where multiple bridge arms are simultaneously conducting, the bus current is the algebraic sum of the currents in the conducting branches. By combining Kirchhoff's current law and phase current constraints, the collector current I of the bridge arm can be obtained. c .

[0045] In some preferred embodiments, the above-mentioned S22, which reconstructs the collector current at each moment in the timing diagram, may further include: S221, In a three-phase two-level inverter, let the conduction state function of each phase transistor be... for: in This indicates that the upper transistor of phase p is conducting. This indicates that the lower transistor of phase p is conducting; the three-phase currents are respectively ,satisfy: S222, DC bus current Defined as the algebraic sum of the currents in each phase transistor, then: S223, at a certain moment The sudden change in bus current when a switching transition occurs (such as a change in the conduction state of the upper or lower phase transistor). Represented as: In the formula, When its value is +1, it indicates that the upper tube changes from off to on. At time 1, it indicates that the upper tube has changed from being on to being off; This refers to the p-phase current. S224, in the common case of single-phase operation, let the phase be q, the above equation simplifies to: This formula is used as a general expression for the change of bus current, which can simultaneously reflect the combined influence of the direction of the change of the switching function and the algebraic direction of the phase current on the bus current. S225, when When the upper tube changes from off to on, the polarity of the bus current change is the same as that of the phase current, i.e.: If i q >0, then >0, bus current increases; If i q <0, then <0, bus current decreases; when When the upper tube changes from conducting to turning off, the polarity of the bus current change is opposite to that of the phase current, i.e.: If i q >0, then <0, bus current decreases; If iq <0, then >0, bus current increases; S226, to determine the actual collector current (i.e., the conduction and current-carrying state of the device) of each bridge arm, is defined as follows: In the formula, This represents the collector current of each of the upper transistors (1, 3, 5). This represents the collector current of each of the lower transistors (2, 4, 6).

[0046] The above reconstruction logic shows that: When the upper transistor is turned on and the direction of the phase current is consistent with the defined direction of the current, i.e. p When the current is greater than 0, the upper tube bears the conduction current. When the current transistor is turned on and the phase current is in the opposite direction to the current of the upper transistor, i.e. p When <0, the lower tube bears the conduction current; In other cases, the device current is zero, and the current is carried by the freewheeling diode; By detecting the abrupt amplitude and polarity of the bus current waveform and combining it with the rising / falling edge information of the drive signal, the collector current waveform of each IGBT can be accurately reconstructed without directly measuring the current of each IGBT. This method is applicable to any sector and any carrier period, and is a universal basis for establishing the mapping relationship between bus current and device current. Note that, due to the inductive characteristics of the three-phase motor load, the phase current of any bridge arm remains continuous during the dead time of the switching device, and the current will automatically freewheel through the anti-parallel diode of the non-conducting device in the corresponding bridge arm. Therefore, during the bus current reconfiguration process, regardless of whether there is a dead time, the instantaneous change of the bus current is determined only by the arm voltage state (i.e., the conduction relationship of the upper and lower switches) and is not affected by the dead time. The dead zone only affects the assignment of device current (IGBT or diode), and this assignment does not affect the switching events located by the fluctuation of drive signal and bus current in Table 1. Therefore, it does not affect the decomposition of bus current and the reconstruction of collector current.

[0047] In some preferred embodiments, in S3 above, the reconstructed collector current I of each bridge arm c Extracting the turn-off delay of each IGBT can further include: S31, based on the reconstructed collector current I of each bridge arm c The turn-off process of each IGBT is monitored in real time. S32, with driving voltage U GE The trailing edge of the pulse falls to a set ratio a (aV) of its amplitude. GEThe time from which the collector current drops to a set proportion b of its amplitude is reached. CM The time of shutdown is used as the reference point for calculating the shutdown delay; S33, based on the reference point calculated by the turn-off delay, captures the moment when the bus current undergoes a negative transition under the action of the drive signal, which corresponds to the bridge arm collector current I. c At the moment of descent, extract the turn-off delay of each IGBT.

[0048] In some preferred embodiments, S4 above, which establishes the relationship between turn-off delay and temperature and extracts junction temperature information using the turn-off delay, may further include: S41, During the offline calibration phase, for the health IGBT device model to be monitored, the temperature T set in the constant temperature chamber is used as the junction temperature T. j Under these conditions, the turn-off delay t of the IGBT is measured with a fixed interval ΔT as the step size. d(off) The measurement data was organized and a t was established. d(off) -T j Mathematical model; Real-time acquisition of collector current I of each bridge arm within N PWM cycles c And the drive signals of each bridge arm to obtain the device's turn-off delay time, for t d(off) -T j The mathematical model is dynamically updated to extract junction temperature information in real time.

[0049] In some preferred embodiments, the above-mentioned S5, which locates the IGBT with abnormal junction temperature and monitors the IGBT status in real time, may further include: S51, within the PWM cycle that meets the monitoring standard, the turn-off delay time t is extracted through analysis. d(off) Estimate the junction temperature T of the IGBT device j And calculate the junction temperature T. j The degree of deviation from the reference value is used to identify IGBT devices with abnormal conditions and to monitor the IGBT status in real time.

[0050] In some preferred embodiments, the above-mentioned S5 may further include: S52, when an abnormal change in the junction temperature of the IGBT device is detected, takes corresponding pre-set protection measures or adjusts the pre-set control strategy to handle the abnormal IGBT device.

[0051] Based on the same inventive concept, one embodiment of the present invention also provides an IGBT condition monitoring system for a motor drive system based on bus current measurement.

[0052] Specifically, such as Figure 3As shown, the IGBT condition monitoring system for a motor drive system based on bus current measurement provided in this embodiment may include: The data acquisition module is used to acquire runtime data of the motor drive system, including bus current and drive signals of each bridge arm; The bridge arm collector current reconstruction module is used to decompose the measured bus current into each conducting IGBT at each sampling time, in conjunction with the bridge arm drive signal, and reconstruct the collector current I of each bridge arm. c Refactor; The junction temperature information extraction module utilizes the reconstructed collector current I of each bridge arm. c Extract the turn-off delay of each IGBT; establish the relationship between turn-off delay and temperature, and use the turn-off delay to extract junction temperature information; The status monitoring module is used to locate IGBTs with abnormal junction temperatures and monitor the IGBT status in real time.

[0053] The specific implementation methods of each functional module constituting the monitoring system provided in the above embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0054] The monitoring system provided in this embodiment includes the following modules: I. Data Acquisition Module, in such Figure 1 The system shown collects data during operation, including: Bus current measurement unit: A single current sensor is installed on the DC bus to acquire the bus current Idc in real time. The sampling frequency should be sufficient to capture waveform details within the PWM cycle, such as... Figure 4 As shown; Each IGBT drive signal acquisition unit for each bridge arm: records the PWM drive signals output by the DSP for each bridge arm of the inverter, used to determine the switching state. The signals include the on and off timing of each bridge arm, such as... Figure 4 As shown; II. Bridge Arm Collector Current Reconstruction Module: This module is used for bus current decomposition and collector current reconstruction. At each sampling time, it combines the bridge arm drive signal to decompose the measured bus current onto each conducting IGBT, thus obtaining the collector current IC of each bridge arm. c Its waveform is as follows Figure 5 As shown. Now, considering the motor rotor being in the first sector, with the A-phase output current polarity being positive and the B and C-phase output current polarities being negative (e.g.) Figure 4 Taking the bus current monitoring situation as an example, let's describe it further: Bus current decomposition unit: By combining the switching timing of each bridge arm drive signal and the polarity of the bus current fluctuation ΔIdc, the direction of the output phase current can be determined. Based on this, the switching device causing the fluctuation can be located by analyzing the bus current fluctuation and the phase current direction. The device switching location relationship during bus current fluctuation is summarized in Table 1: Table 1 Switch Status Positioning During Bus Current Fluctuations Collector current reconstruction unit: Collector current reconstruction at various moments in the timing diagram, such as... Figure 4 and Figure 5 As shown, it specifically includes: Taking the motor rotor in the first sector as an example, the reconfiguration involves the IGBT collector current. The direction of the A-phase output phase current is positive (i a >0), the direction of the output phase current of phases B and C is negative (i b i c <0), i a i b i c The absolute value of the current is ,but: During the zero-vector action time T0-T1, when the bus current is 0, the collector current I of each IGBT arm is... c =0; At time T1, the switch action is that the upper transistor V1 of phase A is turned on, and the rising edge of the upper bridge arm drive signal of phase A is activated. ,at this time >0, ; Due to the bus current rising to I α ΔI dc If the polarity is positive, then ΔI dc =I α ; During the time period T1-T2, the collector current I of the upper transistor V1 is reconstructed. c1 =I α ; At time T2, the switching action is that the lower transistor V4 of phase B is turned off, and the lower bridge arm drive signal of phase B falls. Then, the increment of the upper transistor's state function is: ,at this time <0, ; Bus current drops to I α -I β , i.e. ΔI dc If the polarity is negative, then ΔI dc =I β ; During the T2-T3 time period, the collector current I of the lower transistor V4 is reconstructed. c4=0; At time T3, the switching action is that the lower C-phase transistor V6 is turned off, and the lower C-phase bridge arm drive signal falls. Then, the increment of the upper transistor's state function is: ,at this time <0, ; Bus current drops to I α -I β -I γ , i.e. ΔI dc If the polarity is negative, then ΔI dc =I γ ; During the T3-T4 time period, the collector current I of the lower transistor V6 is reconstructed. c6 =0; At time T4, the switching action is that the lower C-phase transistor V6 is turned on, and the rising edge of the lower C-phase bridge arm drive signal is reached. Therefore, the increment of the upper transistor's state function is: ,at this time <0, ; Bus current rises to I α -I β , i.e. ΔI dc If the polarity is positive, then ΔI dc =I γ ; During the T4-T5 time period, the collector current I of the lower transistor V6 is reconstructed. c6 = -i c =I γ ; At time T5, the switching action is that the lower transistor V4 of phase B is turned on, and the rising edge of the lower bridge arm drive signal of phase B is reached. Therefore, the increment of the upper transistor's state function is: ,at this time <0, ; Bus current rises to I α , i.e. ΔI dc If the polarity is positive, then ΔI dc =I β ; During the T5-T6 time period, the collector current I of the lower transistor V4 is reconstructed. c4 =-i b =I β ; At time T6, the switch action is that the upper transistor V1 of phase A is turned off, and the upper bridge arm drive signal of phase A falls on the falling edge. ,at this time >0, ; The bus current drops to 0, i.e., ΔI dc If the polarity is negative, then ΔI dc =Iα ; During the T6-T7 time period, the collector current I of the upper transistor V1 is reconstructed. c1 =0.

[0055] When only one bridge arm is conducting, by analyzing I dc ΔI during state transition dc The polarity of I dc The collector current of the IGBT in this branch is assigned a value after considering the polarity (positive or negative). During the steady-state period when multiple bridge arms are simultaneously conducting, the bus current is the algebraic sum of the currents in the conducting branches, which needs to be solved by combining Kirchhoff's current law and phase current constraints. III. Junction Temperature Information Extraction Module, including: The specific steps for shutting down the delay extraction unit are as follows: The reconstructed collector current I c It can monitor the IGBT turn-off process in real time.

[0056] Because other electrical parameters reflecting the state of a device are difficult to measure on an integrated module, such as on-state voltage drop (V... CE(on) ) and the related characteristic evaluation methods (VI characteristics, etc.); while based on the short-circuit current i sc Estimate junction temperature T j The problem is that online monitoring is not possible and there is a degradation effect that leads to equipment failure.

[0057] Therefore, this unit selects the turn-off delay time based on the collector current reconstruction method to evaluate the device state, such as... Figure 6 As shown, the shutdown delay time (t) d（off） The term refers to the interval from the end of the gate voltage that keeps the IGBT on to the start of the collector current decreasing. Typically, it is expressed as the drive voltage U. GE The trailing edge of the pulse drops to 90% of its amplitude (0.9V). GE The time from when the collector current drops to 90% of its amplitude (0.9I) is reached. CM The time of shutdown is used as a reference point for calculating the shutdown delay.

[0058] Capture the negative transition moment of the bus current under the action of the drive signal (corresponding to I). c The start of the descent time is crucial for extracting the turn-off delay. Simultaneously, within the first sector, the polarity of the output phase current of phase A is positive, while the polarity of the output phase currents of phases B and C is negative. As shown in Table 1, the turn-off parameters of the upper bridge arm V1 of phase A and the lower bridge arms V4 and V6 of phases B and C can be obtained at this time. The junction temperature information unit extracts junction temperature information using a turn-off delay. The specific method is as follows: During the offline calibration phase, the turn-off delay characteristics of the IGBT devices to be monitored were measured under different temperature conditions. Specifically, the temperature T set in the constant temperature chamber (i.e., the junction temperature T) was used. j Under these conditions, the turn-off delay t of the IGBT device is measured with a fixed interval ΔT as the step size. d(off) The measurement data was organized and a t was established. d(off) -T j Mathematical model; Dynamic update: Real-time acquisition of the collector current I of each bridge arm within N PWM cycles of the system (multi-vector, multi-cycle). c Each bridge arm drive signal is used to obtain the device turn-off delay time and to extract junction temperature information in real time; IV. Status monitoring module, including: The location unit for devices in abnormal states is implemented as follows: Within the PWM cycle that meets monitoring standards (such as avoiding sampling errors that may occur in the low modulation region), the turn-off delay time t is extracted through analysis. d(off) Estimate the device junction temperature T j And calculate the degree of deviation from the reference value to identify IGBT devices with abnormal status; The unit for handling abnormal device states: The specific procedures are as follows: When an abnormal change in IGBT junction temperature is detected, corresponding protective measures or control strategies are taken to ensure the stable operation of the system and the reliability of the IGBT, thereby achieving online and real-time monitoring of the IGBT status.

[0059] It should be noted that the steps in the method provided by the present invention can be implemented using the corresponding components in the system. Those skilled in the art can refer to the technical solution of the system to implement the steps of the method, and can also refer to the technical solution of the method to implement the composition of the system. That is, the embodiments in the system and the embodiments in the method can be understood as preferred examples of each other, which will not be elaborated here.

[0060] The monitoring method and system provided in the above embodiments of the present invention do not require additional circuitry to measure IGBT current. They can acquire the current behavior of each IGBT when it is turned off in each PWM cycle using only existing bus current sensing and drive signals, thereby realizing the detection and timely protection of abnormal turn-off of switching devices.

[0061] The feasibility of the technical solution provided by the above embodiments of the present invention will be further verified and explained below with reference to a specific application example.

[0062] In this specific application example, a simulation environment for a three-phase inverter driving a PMSM was built to simulate the operating scenario of a typical motor drive system. This was combined with the case where the motor rotor is in the first sector, the polarity of the A-phase output current is positive, and the polarity of the B and C-phase output currents is negative (e.g., Figure 4 Taking the bus current monitoring situation shown as an example, the monitoring method provided by the above embodiments of the present invention is verified.

[0063] In a scenario where a three-phase inverter using SVPWM modulation drives a permanent magnet synchronous motor, the fluctuation characteristics of the bus current and its timing relationship with space vector switching are analyzed in detail. Based on the correspondence in Table 1, the switching parameters of three IGBTs can be extracted within each vector cycle. Simultaneously, the switching parameters of the diodes anti-parallel to the other three IGBTs can be obtained (the simulation waveforms are taken as an example in the first sector, such as...). Figure 7 As shown in (a) to (g), the waveform period monitored in this simulation can be used to extract the turn-off delays of V1, V4, and V6 by combining the reconstructed collector current waveform with the drive signal, thereby evaluating the state of the IGBT device. By continuously monitoring multiple PWM cycles, a complete evaluation of the state of all six switching devices can be achieved.

[0064] In such Figure 8 In the simulation waveform results shown in (a) to (c), the turn-off delay of each device directly measured in the simulation software is: V1 turn-off delay t d(off) =57ns, V4 shutdown delay t d(off) 79ns, V6 shutdown delay t d(off) At 75ns, under the simulated operating conditions, the difference in turn-off delay between the various devices meets the experimental accuracy requirements.

[0065] like Figure 9 As shown in (a) to (d), when the device turn-off delay t is obtained directly from the bus current and is not decomposed and reconstructed, the device turn-off delay is... d(off) The turn-off delay t for V1 are respectively d(off) =57ns, V4 shutdown delay t d(off) =80ns, V6 shutdown delay t d(off) =76ns, and Figure 7 The comparison of data directly measured in the simulation shows that it is feasible to extract the turn-off delay parameters of the switching devices by utilizing the bus current fluctuation characteristics.

[0066] In such Figure 10 The simulation waveforms shown in (a) to (f) demonstrate that the reconstructed collector current waveform exhibits good consistency with the actual waveform. The turn-off delay t of V1 obtained from the current reconstruction... d(off) =59ns, V4 shutdown delay t d(off) =82ns, V6 shutdown delay td(off) =77ns, and Figure 8 Compared with the results directly measured by simulation in (a) to (c), the reconstruction error at critical switching moments is smaller, which meets the accuracy requirements of state monitoring and verifies the effectiveness and practicality of the current reconstruction algorithm.

[0067] It should be noted that due to the presence of parasitic inductance and capacitance within the inverter, spike oscillations may occur in the actual collector current caused by the operation of other bridge arm switches. These spikes are difficult to quantitatively model in both the bus current and collector current, thus leading to a certain difference between the reconstructed waveform and the actual waveform. However, this difference has a limited impact on the extraction of the turn-off delay time and does not affect the overall monitoring and judgment of the IGBT status.

[0068] To verify the fault location capability of this method, simulations were performed during the aforementioned monitoring period, simulating aging (abnormal state) conditions for devices V1, V4, and V6. The results are as follows: Figure 11 As shown in (a) to (g): When V1 ages, the abnormal state of V1 can be located by observing the rise / falling edges of the drive signal from T0 to T1 and the fluctuations in the bus current. At this time, the device is turned off after a delay of t. d(off) =70ns; Similarly, when V4 ages, the abnormal state of V4 can be located by observing the rise / falling edges of the drive signals from T2 to T5 and the fluctuations in the bus current. At this time, the device turn-off delay t d(off) =96ns; When V6 ages, the abnormal state of V6 can be located by observing the rise / falling edges of the drive signals T3-T4 and the fluctuations in the bus current. At this time, the device turn-off delay t d(off) =91ns.

[0069] Simulation results show that the monitoring method provided in the above embodiments of the present invention can effectively monitor the health status of IGBTs under various operating conditions: By synchronously analyzing the bus current and PWM signal, the operating characteristics and parameters of each IGBT arm were successfully extracted. Under different device states, the detection sensitivity of this method is sufficient to distinguish the differences in electrical parameters under different states. By analyzing the current characteristics and turn-off delay of each arm, IGBTs with simulated abnormal states can be successfully identified. The method is stable under different loads, noise levels and degrees of abnormal states, indicating its ability to adapt to complex working conditions.

[0070] The motor drive system and its IGBT status monitoring method and system provided in the above embodiments of the present invention have a simplified hardware architecture and significantly reduced costs. Only a high-precision current sensor needs to be added to the DC bus, which significantly simplifies the system hardware structure and reduces sensor costs and installation and debugging work. Online real-time turn-off delay monitoring is highly sensitive. The IGBT junction temperature is estimated as an aging indicator using the IGBT turn-off delay time and dynamic switching characteristics, enabling online and continuous capture of device performance degradation. Its sensitivity is superior to monitoring methods that rely on average voltage / current amplitude. Fault location accuracy is high. Utilizing multi-vector, multi-cycle turn-off feature cross-validation, combined with independent statistical analysis of upper and lower IGBTs, it can accurately distinguish and locate the upper or lower IGBT of a specific bridge arm, improving the accuracy of locating device aging or failure. It is easy to integrate and expand. This method is entirely based on conventional PWM control and DC bus current measurement, requiring no additional modification to the inverter control strategy. It can be seamlessly integrated into existing driver platforms and extended to other multi-bridge arm or multi-level topologies.

[0071] The motor drive system and its IGBT state monitoring method and system provided in the above embodiments of the present invention, by analyzing the timing relationship between the bus current waveform characteristics and the drive signal, realize the monitoring of the collector current I of the IGBT devices in each arm of the three-phase inverter. c Effective reconstruction. Studies have shown that among various temperature-sensitive electrical parameters (TSEP), the turn-off delay time (t) is the most effective. d（off） It possesses optimal temperature sensitivity and linearity. Therefore, this paper further selects a monitoring device with high reconstruction quality and estimates the junction temperature T of the IGBT through its turn-off delay time. j This enables online monitoring and positioning of IGBT status without the need for additional sensors.

[0072] The motor drive system and its IGBT state monitoring method and system provided in the above embodiments of the present invention propose an IGBT health monitoring technology based on a single current sensor and bus current analysis. This technology reconstructs the collector current of each IGBT arm synchronously with the PWM drive signal and evaluates the device state using the turn-off delay. Other technical solutions can also achieve similar online monitoring and fault location goals. These solutions include observer-based diagnostics, current behavior analysis, fuzzy logic and neural networks, on-state voltage drop monitoring, machine learning prediction, and non-contact switching oscillation analysis. These alternative solutions differ from the present invention in their implementation. For example, the observer method relies on mathematical models to estimate the current, fuzzy logic and neural networks rely on data-driven pattern recognition, and non-contact methods indirectly infer the turn-off delay through output current oscillations. In contrast, the present invention achieves lower cost and higher real-time performance through a single sensor and turn-off delay analysis, while maintaining the accuracy of fault location.

[0073] Any matters not covered in the above embodiments of the present invention are well-known in the art.

[0074] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for IGBT condition monitoring of a motor drive system based on bus current measurement, characterized by, Comprise: Obtaining runtime data of motor drive system, including bus current and each bridge arm drive signal; At each sampling time, the measured bus current is decomposed onto the conducting IGBTs in combination with the bridge arm drive signals, and the bridge arm collector currents I c are reconstructed; The reconstructed bridge arm collector currents I c , extract the turn-off delay of each IGBT; Establishing the relationship between the turn-off delay and temperature, using the turn-off delay to extract the junction temperature information; Locating the junction temperature abnormal IGBT, real-time monitoring the IGBT state.

2. The method of claim 1, wherein, The obtaining runtime data of motor drive system, comprising: A single current sensor is installed on the DC bus to collect the bus current I in real time dc ; wherein the sampling frequency of the single current sensor meets the requirement of capturing waveform details within a PWM period. Recording the PWM drive signal output by DSP for each bridge arm, used to determine the switching state; wherein, the PWM drive signal includes the on and off timing of each bridge arm.

3. The method of claim 1, wherein, The measured bus current is decomposed onto each conducting IGBT in combination with the bridge arm drive signal at each sampling time, and each bridge arm collector current I c reconstructing, comprising: The polarity of the bus current fluctuation ΔI dc The polarity of the bus current fluctuation ΔI The polarity of the bus current fluctuation ΔI The collector current of each time in the timing diagram is reconstructed. In the state of only one bridge arm conducting, the polarity of bus current ΔI dc at the state switching is analyzed, the bus current is combined with the positive and negative polarity, and then the collector current of the branch IGBT is assigned to obtain the collector current I c of the corresponding bridge arm; in the steady state of multiple bridge arms conducting simultaneously, the bus current is the algebraic sum of the conducting branch currents, the Kirchhoff's current law and the phase current constraint are combined to solve, and the collector current I c of the bridge arm is obtained.

4. The method of claim 3, wherein, The collector current at each time in the timing diagram is reconstructed, further comprising: In a three-phase two-level inverter, let the on-state function of the upper transistor of each phase be f = 1 - 2 cos(2π / 3) wherein represents upper tube conduction of phase p, represents lower tube conduction of phase p; the three-phase phase currents are , satisfying: Direct current bus current defined as the algebraic sum of the phase currents, then: At a certain time The amount of change in the bus current when a switching jump occurs Is expressed as: wherein , which takes the value +1 when the upper transistor changes from off to on, and the value 1 when the upper transistor changes from on to off; is the p-phase current; In the common situation where a single phase is acting, let this phase be q, and let the sudden change of bus current be simplified to the expression: Taking the formula as a general expression of bus current change, used to reflect the common influence of switching function change direction and algebraic direction of the phase current on bus current; When the upper tube goes from off to on, at which time the bus current change polarity is the same as the phase current polarity, i.e.: If i q > 0, then > 0, bus current rises; If i q <0, then <0, bus current drops; When the upper tube changes from on to off, at which time the bus current changes polarity opposite to the phase current polarity, i.e.: If i q > 0, then < 0, bus current drops; If i q <0, then > 0, bus current rises; Determining the actual collector current of each bridge arm device, defined as follows: In the formulae, denotes the collector current of each upper transistor, denotes the collector current of each lower transistor.

5. The method of claim 1, wherein, The reconstructed bridge arm collector current I c The method for extracting the turn-off delay of each IGBT comprises: According to the reconstructed bridge arm collector current I c The turn-off process of each IGBT is monitored in real time; at the time when the trailing edge of the pulse of the drive voltage U GE falls to a set proportion a of its amplitude to the time when the collector current falls to a set proportion b of its amplitude as the reference point for the calculation of the turn-off delay time; According to the reference point of the turn-off delay time calculation, the negative jump moment of the bus current under the action of the driving signal is captured, that is, the collector current I of the corresponding bridge arm c The turn-off delay time of each IGBT is extracted at the start of the falling moment.

6. The method of claim 1, wherein, The establishing the relationship between the turn-off delay and temperature, using the turn-off delay to extract the junction temperature information, comprising: In the offline calibration stage, for the health IGBT device model to be monitored, at the temperature T set by the thermostat as the junction temperature T j , the turn-off delay t d(off) of the IGBT is measured at a fixed interval ΔT as a step, the measurement data is sorted and the t d(off) -T j mathematical model is established; Real-time acquisition of each bridge arm collector current I in N PWM cycles c and each bridge arm drive signal to obtain the turn-off delay time of the device, and the t d(off) -T j The mathematical model is dynamically updated, and the junction temperature information is extracted in real time.

7. The method of claim 1, wherein, The locating the junction temperature abnormal IGBT, real-time monitoring the IGBT state, comprising: In the PWM cycle meeting the monitoring standard, the turn-off delay time t d(off) The IGBT device junction temperature T is estimated j The deviation of the junction temperature T j from the reference value is calculated, and the IGBT device in abnormal state is determined, and the IGBT state is monitored in real time.

8. The method of claim 1, wherein, Further comprising: When detecting abnormal change of IGBT device junction temperature, taking the corresponding preset protection measures or adjusting the preset control strategy to process the state abnormal IGBT device.

9. A motor drive system IGBT condition monitoring system based on bus current measurement, characterized by, Comprise: Data acquisition module, the module is used for obtaining runtime data of motor drive system, including bus current and each bridge arm drive signal; a bridge arm collector current reconstruction module, which is configured to, at each sampling moment, decompose the measured bus current into each conducting IGBT in combination with the bridge arm drive signal, to obtain each bridge arm collector current I c for reconstruction; A junction temperature information extraction module extracts the turn-off delay of each IGBT by using the reconstructed bridge arm collector current I c , establishes the relationship between the turn-off delay and temperature, and extracts the junction temperature information by using the turn-off delay. State monitoring module, the module is used for locating the junction temperature abnormal IGBT, real-time monitoring the IGBT state.

10. An electric motor drive system characterized by comprising: The method of any one of claims 1-8 is used to realize the IGBT state monitoring.

11. The motor drive system of claim 10, wherein, The system comprises: three-phase inverter, bus current sensor, drive signal voltage sensor and PWM controller; wherein: The three-phase inverter is composed of multiple IGBTs, forming upper and lower bridge arms of A, B and C three-phase respectively; wherein, each IGBT is connected with the corresponding PWM controller through an independent drive circuit, used to receive the drive signal of the PWM controller; The bus current sensor is installed on the DC bus side and is used for measuring the DC bus current I in real time dc ; wherein the sensor adopts a single current sensor for capturing the current change in the PWM period; The drive signal voltage sensor is installed on the gate signal line of each IGBT, used to measure the drive voltage signal of each IGBT in real time; The PWM controller controls the on-off timing of multiple IGBTs, realizing the conversion from direct current to three-phase alternating current, and providing power for motor load.

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