CN111092563A - Power conversion device and method for diagnosing power conversion device - Google Patents
Power conversion device and method for diagnosing power conversion device Download PDFInfo
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- CN111092563A CN111092563A CN201910985749.9A CN201910985749A CN111092563A CN 111092563 A CN111092563 A CN 111092563A CN 201910985749 A CN201910985749 A CN 201910985749A CN 111092563 A CN111092563 A CN 111092563A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/40—Testing power supplies
- G01R31/42—AC power supplies
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Abstract
The invention provides a power converter and a method for diagnosing the power converter, which monitors the operation state of the power converter on line and optimizes the timing of updating the equipment individually. The disclosed device is provided with: a gate drive circuit for driving a switching element constituting a power conversion device in accordance with a PWM command signal for driving the switching element; a current calculation unit and a voltage calculation unit that calculate a collector current or a drain current and a collector voltage or a drain voltage at a timing when the switching element is turned off; a state monitoring unit that estimates an operating state of the power conversion device based on the PWM command signal, a feedback signal generated in accordance with a switching operation of the switching element, an estimated current of the collector current or the drain current, and an estimated voltage of the collector voltage or the drain voltage; and an abnormality diagnosis unit that determines an abnormality of the power conversion device based on the operation state of the power conversion device estimated by the state monitoring unit.
Description
Technical Field
The present invention relates to a power conversion device having an abnormality diagnosis function and a method for diagnosing a power conversion device, and is particularly suitable for diagnosing an abnormality of a power conversion device having a large capacitance.
Background
In order to control a power conversion device used for a motor of a railway or a large-sized industrial facility, or a power conversion device used for frequency conversion of a large capacitance such as a power system, high-voltage and large-current power control is performed using a power semiconductor element having a large capacitance.
In such an apparatus, if a failure occurs in operation, there is a possibility that: causing damage to the system, unplanned system shutdown, and large economic losses. In order to prevent such a situation, it is necessary to detect deterioration and abnormality of the power converter, stop the function to prevent damage, notify the related person of necessity of updating the device, and perform control for extending the life of the power converter.
As a cause of failure of the power conversion device, overheating of the semiconductor switching element is known. The semiconductor switching element is destroyed when it is operated in a state where the junction temperature (Tj) is higher than the rated value. Therefore, a heat dissipation design is implemented for the power conversion device.
Here, since a semiconductor element is formed by laminating a material having a thermal expansion coefficient different from that of a semiconductor chip for mounting, it is inevitable to deteriorate solder and a bonding wire with time due to accumulation of thermal stress caused by self-heating of the semiconductor chip during operation.
Therefore, the thermal impedance of the semiconductor switching element may rise with time, and the semiconductor switching element may overheat.
On the other hand, since the power converter is premised on no maintenance, the semiconductor switching elements themselves are rarely inspected in a normal maintenance work, and the devices themselves are updated at a timing (timing) when a certain period of time has elapsed from the start of use.
However, the deterioration of the power conversion device is accelerated depending on the use environment thereof, and the life of the power conversion device is different from one another. Therefore, it is preferable to monitor the state of each power conversion device on line and optimize the timing of device update individually to reduce maintenance cost.
Among them, as a technique for monitoring the state of the power conversion device by a simple method, a technique for measuring the junction temperature during system operation is known.
Although there is a method of incorporating a temperature sensor inside a semiconductor switching element, integration of the sensor is costly, and there are many problems in terms of response speed and reliability of the temperature sensor.
In addition, a technique of estimating the junction temperature using the temperature dependence of the electrical characteristics of the semiconductor switching element is known. For example, patent document 1 discloses the following method: in the Gate-emitter voltage characteristic at the switch off phase of an IGBT (Insulated Gate Bipolar Transistor) element, the junction temperature of the IGBT element is determined by detecting the delay time from the start phase to the end phase of a Miller platform (Miller platform), and when a continuous increase in the average junction temperature is recorded, the degradation of the element is detected.
Documents of the prior art
Patent document 1: japanese patent laid-open publication No. 2013-142704
Disclosure of Invention
In the method described in patent document 1, the junction temperature of the IGBT element is estimated from the delay time of the switch off from the start to the end of the miller plateau, but the following is not mentioned: the switch off delay time varies not only according to the junction temperature of the IGBT element but also according to the collector current and collector voltage immediately before the switch off.
The inventors found that the switch-off delay time is affected not only by the junction temperature of the IGBT element but also sensitively by the collector current and the collector voltage immediately before the switch-off.
Therefore, for example, in a system in which a voltage applied to a semiconductor switching element provided in a power conversion device and a current flowing through the semiconductor switching element change constantly as in the case of controlling a motor by the power conversion device, it is necessary to detect not only a switch off delay time but also a collector current and a collector voltage at the time of switch off with high accuracy, and calculate a junction temperature from a relationship between these currents, voltages, and the switch off delay time.
As described above, since the semiconductor switching element deteriorates solder and bonding wires over time due to accumulation of thermal stress, it is extremely important to monitor temperature vibration which is a source of thermal stress. Therefore, it is necessary to continuously monitor the junction temperature and to monitor the accumulation of temperature vibration under various current and voltage conditions applied to the semiconductor switching element during operation.
However, since the current and voltage change rapidly during the TURN-OFF (TURN OFF) operation of the semiconductor switching element, it is extremely difficult to detect the collector current in synchronization with the timing of the switching operation.
Therefore, an object of the present invention is to provide a power converter having a semiconductor switching element, which can detect its own abnormality and degree of wear with high accuracy by a simple configuration, and a diagnostic method therefor.
In order to solve the above problem, a power conversion device according to the present invention includes: a gate drive circuit for driving a switching element constituting a power conversion device in accordance with a PWM command signal for driving the switching element; a current calculation unit and a voltage calculation unit that calculate a collector current or a drain current and a collector voltage or a drain voltage at a timing when the switching element is turned off; a state monitoring unit that estimates an operating state of the power conversion device based on the PWM command signal, a feedback signal generated in accordance with a switching operation of the switching element, an estimated current of the collector current or the drain current, and an estimated voltage of the collector voltage or the drain voltage; and an abnormality diagnosis unit that determines an abnormality of the power conversion device based on the operation state of the power conversion device estimated by the state monitoring unit.
According to the present invention, it is possible to provide a power conversion device capable of detecting an abnormality or a degree of wear of the power conversion device itself with high accuracy by a simple configuration, and a diagnostic method therefor.
Problems, structures, and effects other than those described above will become apparent from the following description of the embodiments.
Drawings
Fig. 1 is a block diagram showing an example of the configuration of a power conversion device according to embodiment 1.
Fig. 2 is a block diagram showing an example of a configuration in which a current calculation unit, a voltage calculation unit, a state monitoring unit, and an abnormality diagnosis unit are integrated into a control unit in the power conversion device according to embodiment 1.
Fig. 3 is a diagram showing an example of a specific configuration of the inverter according to embodiment 1.
Fig. 4 is a diagram showing an example of a specific circuit configuration of the control unit for calculating the switch off delay time.
Fig. 5 is a diagram showing a time relationship among the PWM command signal, the gate voltage, the feedback signal, and 3.
Fig. 6 is a diagram showing a switching waveform when the semiconductor switching element is switched on.
Fig. 7 is a diagram showing a switching waveform and a feedback signal waveform when the semiconductor switching element is switched off.
Fig. 8 is a diagram showing the relationship among the PWM command signal, the carrier signal, the motor phase current, the motor current value detected for use in motor control, and the estimated collector current at the time of off.
Fig. 9 is a graph showing the relationship between the switching off delay time and the junction temperature of the semiconductor switching element, the relationship between the switching off delay time and the collector current, and the relationship between the switching off delay time and the dc power supply voltage.
Fig. 10 is a diagram showing points at which the motor phase current changes with time and the joining temperature becomes maximum and minimum.
Fig. 11 is a diagram showing an example of temperature amplitude frequency data obtained by transforming time-series data of the junction temperature into a histogram.
Fig. 12 is a diagram showing the relationship between the change in the motor phase current, the switch off delay time, and the calculated estimated joining temperature in the normal operation and the ground fault occurrence according to example 2.
Fig. 13 is a diagram showing a part of the configuration of the control unit according to embodiment 3 together with a gate driver circuit.
Fig. 14 is a diagram showing an example of the relationship between the numbers of pulses of the PWM command signal and the feedback signal.
(symbol description)
1: a control unit; 2(2a to 2 f): a semiconductor switching element; 3(3a to 3 f): a gate drive circuit; 4: a current calculation unit; 5: a voltage calculation unit; 6: a state monitoring unit; 7: an abnormality diagnosis unit; 8: an inverter; 9: a motor; 10: a torque command calculation unit; 11: a current command calculation unit; 12: a current command/3-phase voltage command conversion unit; 13: a PWM conversion unit; 14: a current feedback conversion unit; 15: a PWM command signal width calculation unit; 16: a feedback signal width calculating section; 17: a direct current power supply; 18: a smoothing capacitor; 19(19a, 19 b): an insulating member; 20: a gate driving section; 21. 22: a comparator; 23. 24: a time measuring part; 25: a time comparison unit; 26: a pulse number measuring section.
Detailed Description
Hereinafter, examples 1 to 3 according to the present invention will be described with reference to the drawings as a mode for carrying out the present invention. In the drawings, the same components are denoted by the same reference numerals, and the detailed description of the overlapping portions will be omitted.
[ example 1 ]
Fig. 1 is a block diagram showing an example of the configuration of a power conversion device according to embodiment 1.
The control unit 1 outputs a PWM command signal and inputs a feedback signal (FB).
The gate drive circuit 3 drives the semiconductor switching element 2 in accordance with the PWM command signal received from the control unit 1, and transmits a feedback signal (FB) to the control unit 1 and the state monitoring unit 6 in accordance with the driving result.
The state monitoring unit 6 monitors the operating state of the power conversion apparatus including the semiconductor switching element 2, based on the estimated collector current at the off-time of the semiconductor switching element 2 calculated by the current calculating unit 4, the estimated collector voltage at the off-time of the semiconductor switching element 2 calculated by the voltage calculating unit 5, the previous PWM command signal, and the previous feedback signal (FB).
The abnormality diagnosis unit 7 determines an abnormal state in the power conversion device, such as an abnormality or deterioration of the switching element 2, based on the monitoring result obtained by monitoring the power conversion device by the state monitoring unit 6.
Fig. 2 is a block diagram showing an example of a configuration in which the current calculation unit 4, the voltage calculation unit 5, the state monitoring unit 6, and the abnormality diagnosis unit 7 are integrated in the control unit 1 in the power conversion device according to embodiment 1.
The control unit 1 includes an inverter 8 that converts dc power to ac power, a 3-phase ac motor 9 that is driven by 3-phase ac current (U-phase current ium, V-phase current ivm, and W-phase current iwm) generated by the inverter 8, and a PWM command signal for control to be transmitted to the inverter 8.
The control unit 1 includes a microcomputer having a CPU, a memory, and the like, and includes, as constituent elements, a current calculation unit 4, a voltage calculation unit 5, a state monitoring unit 6, an abnormality diagnosis unit 7, a torque command calculation unit 10, a current command calculation unit 11, a current command/3-phase voltage conversion unit 12, a PWM conversion unit 13, a current feedback conversion unit 14, a PWM command signal width calculation unit 15, and a feedback signal width calculation unit 16.
The current feedback converter 14 converts the motor drive current of each phase detected by the U-phase current sensor, the V-phase current sensor, and the W-phase current sensor (all not shown) into a d-axis current id and a q-axis current iq by coordinate conversion using the rotation angle θ of the motor 9, and inputs the converted currents to the current command/3-phase voltage converter 12.
The current command calculation unit 11 calculates a d-axis current command value id from the torque command value input from the torque command calculation unit 10 in accordance with a table or the like prepared in advance*And a q-axis current command value iq*And is input to the current command/3-phase voltage conversion unit 12.
The current command/3-phase voltage converting unit 12 outputs a current command value id according to the d-axis*Q-axis current command value iq*And a d-axis and q-axis voltage command value is generated from the d-axis current id and the q-axis current iq inputted from the current feedback conversion unit 14, and then the voltage command value is converted into a 3-phase ac voltage command value Vu using the rotation angle θ of the motor 9*、Vv*And Vw*And input to the PWM conversion unit 13.
The inverter 8 outputs a drive current to each phase of the motor 9 based on the PWM command signal input from the PWM conversion unit 13, and drives the motor 9.
Fig. 3 is a diagram showing an example of a specific configuration of the inverter 8 including the switching element 2.
The inverter 8 is connected between the positive electrode side and the negative electrode side of the dc power supply 17 and the smoothing capacitor 18, and converts and outputs an input current between a dc power and an ac power. Therefore, the inverter 8 includes a plurality of semiconductor switching elements (2a to 2f), and the output lines thereof are connected to the 3-phase (U-phase, V-phase, and W-phase) windings of the motor 9, thereby controlling the connection between the motor 9 and the dc power supply 17 by controlling the ON/OFF of the semiconductor switching elements (2a to 2 f).
The gate drive circuits 3a to 3f drive the respective semiconductor switching elements (2a to 2f) in accordance with the PWM command signal transmitted from the control unit 1, and transmit a feedback signal (FB) to the control unit 1 in accordance with the driving result.
The semiconductor switching elements (2a to 2f) are not limited to the illustrated IGBTs, and various switching elements such as transistors and MOS-FETs can be used. In the case of using a MOS-FET, the emitter is instead referred to as the source and the collector is instead referred to as the drain.
Fig. 4 is a diagram showing an example of a specific circuit configuration of the control unit 1 for calculating the switch off delay time from the PWM command signal and the feedback signal (FB).
The gate drive circuit 3 and the control unit 1 are insulated from each other by insulating elements 19a and 19b (specifically, a photo coupling type element, a magnetic coupling type element, an electrostatic coupling type element, or the like).
The gate drive circuit 3 includes insulating elements 19a and 19b, a gate drive section 20 that drives the semiconductor switching element 2, a comparator 21 that compares the gate voltage with a switch-on reference voltage to determine that the switch is on, and a comparator 22 that compares the gate voltage with a switch-off reference voltage to determine that the switch is off. The feedback signal (FB) is transmitted from the gate drive circuit 3 to the control unit 1 in accordance with the operations of the comparators 21 and 22.
In the control unit 1, the feedback signal (FB) received from the gate drive circuit 3 is input to the built-in time measurement unit 23, and the pulse width based on the feedback signal (FB) is measured. The PWM command signal output from the PWM conversion unit 13 is input not only to the gate drive circuit 3 but also to a time measurement unit 24 built in the control unit 1, and the pulse width of the PWM command signal is measured. Here, the time measuring unit 23 and the time measuring unit 24 have a time resolution of, for example, 10 nanoseconds or less. The pulse widths of the feedback signal (FB) and the PWM command signal measured by the time measuring unit 23 and the time measuring unit 24 are input to the time comparing unit 25, and the switch off delay time can be calculated by comparing both values.
In the control unit 1, the pulse widths of the feedback signal (FB) and the PWM command signal are measured by the time measuring units 23 and 24, respectively, but instead of these, another time measuring unit (not shown) that measures the time from the switch off of the PWM command signal to the switch off of the feedback signal (FB) may be provided, and the switch off delay time may be calculated from the measured time.
Fig. 5 is a diagram showing a time relationship among the PWM command signal, the gate voltage, and the feedback signal (FB), 3.
As shown in fig. 5, the PWM command signal for switching on output from the PWM conversion unit 13 is input to the gate terminal of the semiconductor switching element 2 after a circuit delay caused by the gate drive circuit 3 including the insulating element 19 b. If a switch-on signal is input to the semiconductor switching element 2, the gate voltage rises with a time constant corresponding to the gate resistance and the capacitance of the element. If the gate voltage reaches the switch-on reference voltage after the element delay based on the time constant, the comparator 21 operates to output a feedback signal (FB) that the switch is on. The feedback signal (FB) is input to the time measurement portion 23 after passing through a circuit delay caused by the gate drive circuit 3 including the insulating element 19 a.
Similarly, if the PWM conversion unit 13 outputs the PWM command signal for switching off, the switching off signal is input to the gate terminal of the semiconductor switching element 2 after a circuit delay caused by the gate drive circuit 3 including the insulating element 19 b. If a switch off signal is input to the semiconductor switching element 2, the gate voltage drops with a time constant corresponding to the gate resistance and the capacitance of the element. If the gate voltage reaches the switch-off reference voltage after the element delay based on the time constant, the comparator 22 operates to output a feedback signal (FB) of the switch-off. The feedback signal (FB) is input to the time measurement portion 23 after passing through a circuit delay caused by the gate drive circuit 3 including the insulating element 19 a.
The time measuring unit 23 measures the pulse width of the feedback signal (FB) based on the inputs of the feedback signal (FB) with the switch on and the feedback signal (FB) with the switch off.
Here, the inventors analyzed the correlation of the PWM command signal, the switching waveform of the semiconductor switching element 2, and the feedback signal waveform. As a result, the element delay is substantially constant regardless of the junction temperature, the collector current, and the dc power supply voltage when the switch is turned on. On the other hand, it was found that the element delay varies depending on the junction temperature, the collector current, and the dc power supply voltage in the switch-off.
Fig. 6 is a diagram showing switching waveforms in a case where the PWM command signal is output as the reference time when the switch is turned on under the condition that the circuit delay times are made constant among (a) to (c).
Fig. 6 (a) shows waveforms in the case where the bonding temperature (for example, the case of 40 ℃ and 100 ℃) is varied variously, fig. 6 (b) shows waveforms in the case where the collector current (for example, the case of 600A, 900A and 1200A) is varied variously, and fig. 6 (c) shows waveforms in the case where the dc power supply voltage (for example, the case of 1100V, 1300V and 1500V) is varied variously. The switch-on reference voltage for determining the on state of the switch is set to 5V as an example.
As shown in (a) to (c) of fig. 6, the timing at which the gate voltage reaches the switch-on reference voltage is substantially constant regardless of the junction temperature, the collector current, and the dc power supply voltage. Therefore, it is found that the element delay at the time of turning on the switch has very small dependence on the junction temperature, the collector current, and the dc power supply voltage.
Fig. 7 is a diagram showing switching waveforms ((a), (c), and (e)) and feedback signal waveforms ((b), (d), and (f)) when a PWM command signal is output at the time of switching off as a reference time under the condition that the circuit delay times are constantly matched among the waveforms (a) to (f).
Fig. 7 (a) and (b) show waveforms in the case where the bonding temperature (for example, in the case of 40 ℃ and 100 ℃) is varied variously, fig. 7 (c) and (d) show waveforms in the case where the collector current (for example, in the case of 600A, 900A and 1200A) is varied variously, and fig. 7 (e) and (f) show waveforms in the case where the dc power supply voltage (for example, in the case of 1100V, 1300V and 1500V) is varied variously. Further, the switch-off reference voltage for determining the switch-off is set to-5V as an example.
It is understood that the delay time until the gate voltage reaches the switch off reference voltage becomes longer when the junction temperature increases in fig. 7 (a), when the collector current decreases in fig. 7 (c), and when the dc power supply voltage increases in fig. 7 (e). It is known that these phenomena can be explained mainly by the dependence of the feedback capacitance of the element on each parameter.
As shown in fig. 7 (b), (d), and (f), the timing of outputting the feedback signal (FB) for turning off the switch changes according to the delay time until the gate voltage reaches the switch-off reference voltage.
Therefore, it is known that the element delay at the time of turning off the switch varies depending on the junction temperature, the collector current, and the dc power supply voltage.
From the above results, if the pulse widths of the PWM command signal and the feedback signal (FB) are compared, it is found that the change in the element delay when the switch is turned off can be measured.
Regarding the circuit delay, it was confirmed that the circuit delay varied according to the ambient temperature of the gate driver circuit 3, and the variation of the circuit delay when the switch was turned on was equal to the variation of the circuit delay when the switch was turned off. As a result, if the pulse widths of the PWM command signal and the feedback signal (FB) are compared, it is found that the influence of the temperature change of the circuit delay caused by the gate drive circuit can be canceled with each other. In the case of a circuit configuration in which the temperature dependency of the circuit delay is different between when the switch is turned on and when the switch is turned off, a thermometer or the like may be provided for the gate driver circuit to correct the change in the circuit delay.
From the above-described results of the study, in order to estimate the junction temperature of the semiconductor switching element 2, it is necessary to detect the dc power supply voltage and the collector current at the time of off, and calculate the junction temperature from the relationship between the delay time of the element and the detected current and voltage.
In example 1, the detection of the dc power supply voltage is calculated by measuring the voltages of the positive electrode side and the negative electrode side of the smoothing capacitor 18. On the other hand, in the detection of the collector current, the collector current rapidly changes at the time of the off operation, and therefore it is extremely difficult to sample the current in accordance with the off timing. Further, as shown in fig. 2, the current of each phase of the motor is sampled for use in motor control, but generally, the current is sampled at each midpoint between on and off of the PWM command signal in synchronization with the carrier signal, and therefore, a scheme of detecting the current at the timing of off is not used in motor control.
Here, the inventors analyzed the relationship between the PWM command signal, the motor phase current value sampled in synchronization with the carrier signal for use in motor control, and the collector current at the time of off-state. As a result, it was found that the collector current at the time of off-state can be estimated from the voltage of each phase of the motor obtained by combining the PWM command signals of each phase, the rate of change of the motor phase currents (ium, ivm, and iwm) calculated based on the dc power supply voltage, the motor induced voltage Em, and the motor constant (inductance L), the motor phase current value sampled by carrier synchronization, and the phase difference due to the pulse width of the PWM command signal and the operation delay of the semiconductor switching element 2. In embodiment 1, the operation delay of the semiconductor switching element 2 is 10 microseconds or less and is set to be constant in advance, but when the rate of change of the motor phase current is small, the current accuracy can be sufficiently improved even if the influence of the operation delay is ignored.
Fig. 8 is a diagram showing the relationship among the PWM command signal, the carrier signal, the motor phase current (Im), the motor current value (current sample) detected for use in motor control, and the estimated collector current at the time of off.
In embodiment 1, using the above-described relationship, internal parameters for control such as the PWM command signal width and the carrier period and the motor phase current are input to the current calculation unit 4, and the collector current at the time of off-state is calculated. According to embodiment 1, the collector current at the time of off can be estimated with high accuracy using the current value detected for use in motor control, which has been conventionally used.
In fig. 9, regarding the switch off delay, the relationship with the junction temperature (Tj) of the semiconductor switching element 2 is shown in (a), the relationship with the collector current (Ice) is shown in (b), and the relationship with the dc power supply voltage (Vce) is shown in (c).
The switch off delay time calculated by the time comparison unit 25, the estimated collector current at the time of off calculated by the current calculation unit 4, and the dc power supply voltage at the time of off calculated by the voltage calculation unit 5 are input to the state monitoring unit 6, and the junction temperature of the semiconductor switching element 2 is estimated for each switching operation based on the relationship between these delay times and the current and voltage. Fig. 9 (d) exemplarily shows the same.
As described above, one of the points of the embodiment 1 is to monitor the degree of wear of the plurality of semiconductor switching elements 2 in the power conversion device, prevent a failure of the system in advance, and notify the appropriate timing of device update.
Fig. 10 is a diagram showing the point at which the motor phase current changes with time and the joining temperature becomes maximum and minimum.
The state monitoring unit 6 includes, for example, as shown in fig. 10, a means for monitoring the junction temperature at the time of switching operation at the maximum value (Tmax) and the minimum value (Tmin) in one cycle of each motor phase current (Im), and stores the temperature difference and the number of times thereof in a memory or the like as a frequency distribution of thermal cycles. As a method of converting the thermal cycle into a frequency, for example, a rain flow (Rainflow) algorithm is known.
Fig. 11 is a diagram showing an example of time-series data of the junction temperature and the frequency of the temperature amplitude converted into a histogram. The temperature amplitude Δ T of the horizontal axis is set on a 5 ° scale, for example. The vertical axis shows the logarithm of the cycle number N (logN). As the thermal cycle rating, a power cycle test provided at the time of shipment of the semiconductor switching element 2 was used. In fig. 11, Ni is the allowable maximum cycle number of the temperature amplitude Ti, and Ni (black portion shown in fig. 11) is the cycle number of the temperature amplitude Ti obtained by the state monitoring unit 6. In addition, the degree of wear Di for each temperature amplitude Ti is given by Ni/Ni, and the degree of wear as a whole is given by Σ Di.
Σ Di calculated by the state monitoring unit 6 is transmitted to the abnormality diagnosis unit 7. When the input Σ Di exceeds a predetermined value, the abnormality diagnosis unit 7 determines wear deterioration of the element and notifies the relevant person of the determination result. In this case, the abnormality diagnosis unit 7 may include a GUI (Graphical User Interface) for prompting a device update. Further, the abnormality determination result can be transmitted to the vehicle information integration system, and if the abnormality determination result is included in the central monitoring system, it is possible to realize monitoring of a plurality of vehicles, and it is possible to contribute to optimization of the maintenance plan.
As described above, according to embodiment 1, by storing time-series data of the change in the junction temperature of the semiconductor switching element and comparing the data with the reference value, it is possible to detect the degree of wear of the semiconductor switching element and the power conversion device associated therewith with high accuracy, prevent failures such as malfunctions with high accuracy, and optimize equipment renewal and maintenance.
[ example 2 ]
Fig. 12 is a graph showing changes in the motor phase current (Im) during normal operation and during a ground fault in the graph (a), and showing the relationship between the switch off delay time and the calculated estimated joining temperature (Tj) in the graph (b).
As shown in fig. 12 (a), since the rate of change of the motor phase current (Im) when the ground fault occurs is larger than that in the normal operation, the collector current actually flowing through the semiconductor switching element 2 is larger than the estimated value of the collector current calculated by the current calculation unit 4.
As a result, as shown in fig. 12 (b), since the switch off delay time becomes shorter than that in the normal operation when the ground fault occurs, the junction temperature (Tj) of the semiconductor switching element 2 estimated by the state monitoring unit 6 is estimated to be lower than that in the normal operation based on the estimated values of the switch off delay time, the collector current, and the collector voltage. Since the current dependency of the switching-off delay time is large, the state monitoring unit 6 outputs an abnormal result of a rapid decrease in the junction temperature (Tj) of the semiconductor switching element 2.
As described above, it is possible to determine an abnormality in the collector current value due to a ground fault or the like from the estimated values of the switch off delay time, the collector current, and the collector voltage.
According to embodiment 2, in the time-series data of the joining temperature (Tj) input from the state monitoring unit 6 to the abnormality monitoring unit 7, when an abnormal value in which the joining temperature change is larger than a predetermined value is output, it is possible to determine that the current value is abnormal.
In general, a reference current value is set in advance for detecting a ground fault or a short circuit, and detection is performed when an overcurrent state exceeding the reference current value is reached, so that there is a problem that detection timing is delayed. In the ground fault detection of embodiment 2, the presence or absence of an abnormality can be determined for each switching even in an operation in a low current region where an overcurrent state is not reached, and therefore there is an advantage that the system can be protected earlier.
Therefore, the abnormality detection method according to embodiment 2 can prevent or reduce damage to the system.
[ example 3 ]
Fig. 13 is a diagram showing a part of the configuration of the control unit 1 according to embodiment 3 together with the gate driver circuit 3.
In the foregoing embodiment 1, the pulse widths of the feedback signal (FB) and the PWM command signal are measured by the time measuring sections 23 and 24, respectively, and the switch off delay time is calculated by the time comparing section 25. In embodiment 3, in addition to the configuration of embodiment 1, a pulse number measuring unit 26 is provided, and the respective pulse numbers of the feedback signal (FB) and the PWM command signal are counted based on the output results of the time measuring units 23 and 24.
Fig. 14 is a diagram showing the relationship between the numbers of pulses of the PWM signal and the feedback signal (FB) counted by the pulse number measuring unit 26 according to example 3.
It is known that the gate drive circuit 3 may malfunction under the influence of the surrounding environment and the operation of the power conversion device itself. If the gate drive circuit 3 is accidentally operated due to a malfunction, a short circuit may occur in the power conversion device, and the system may be damaged.
Therefore, generally, outputs of the PWM command signal and the feedback signal are compared to monitor whether the gate drive circuit is operating normally, and when a period of time during which the outputs of the PWM command signal and the feedback signal do not coincide with each other is larger than a predetermined value, it is determined that the gate drive circuit is malfunctioning.
However, as shown in fig. 5, during normal operation, there is an operation delay due to a circuit delay or an element delay between the PWM command signal and the feedback signal, and therefore, it is necessary to increase the threshold value of the output mismatch period for abnormality determination. In this way, if the threshold value of the output non-matching period is increased, a short-period malfunction cannot be detected, and therefore, there is a possibility that the system is deteriorated or damaged.
According to embodiment 3, since the malfunction of the gate drive circuit 3 is detected based on the comparison of the pulse numbers of the PWM command signal and the feedback signal (FB), there is an advantage that the malfunction in a short period can be detected. Further, as shown in fig. 14, since the pulse width of the feedback signal (FB) can also be measured by the time measuring unit 23, the malfunction period can also be detected.
Therefore, according to the abnormality detection method of embodiment 3, damage to the system can be prevented or reduced.
Claims (18)
1. A power conversion device having a switching element, wherein,
the power conversion device is provided with:
a gate drive circuit that drives the switching element in accordance with a PWM command signal for driving the switching element;
a current calculation unit and a voltage calculation unit that calculate a collector current or a drain current and a collector voltage or a drain voltage at a timing when the switching element is turned off, respectively;
a state monitoring unit configured to estimate an operating state of the power conversion device based on the PWM command signal, a feedback signal generated in accordance with a switching operation of the switching element, an estimated current of the collector current or the drain current, and an estimated voltage of the collector voltage or the drain voltage; and
and an abnormality diagnosis unit that determines an abnormality of the power conversion device based on the operation state of the power conversion device estimated by the state monitoring unit.
2. The power conversion apparatus according to claim 1,
the feedback signal is generated by comparing a voltage between the gate and the emitter or the source during a switching operation of the switching element with a switching-on reference voltage and a switching-off reference voltage, respectively.
3. The power conversion apparatus according to claim 1 or 2,
the power conversion device is provided with:
a 1 st time measuring unit for measuring an on period or an off period of the PWM command signal; and
a 2 nd time measuring unit for measuring an ON period or an OFF period of the feedback signal,
the switching-off delay time of the switching element is calculated based on the on-period or off-period of the PWM command signal measured by the 1 st time measuring unit and the on-period or off-period of the feedback signal measured by the 2 nd time measuring unit.
4. The power conversion apparatus according to claim 1 or 2,
the power conversion device includes a time measurement unit that measures a time from when the switch of the PWM command signal is turned off to when the switch of the feedback signal is turned off,
the switching-off delay time of the switching element is calculated based on the measurement value of the time measurement unit.
5. The power conversion apparatus according to claim 1 or 2,
the voltage calculation unit calculates an estimated voltage of the collector voltage or the drain voltage based on a measured voltage of a capacitor provided between a positive electrode and a negative electrode on a direct current power supply side of the power conversion device.
6. The power conversion apparatus according to claim 1 or 2,
the current calculation unit calculates an estimated current of the collector current or the drain current at a timing when the switching element is turned off, based on a measured current of each phase current output from the power conversion device, the PWM command signal, and an estimated voltage of the collector voltage or the drain voltage.
7. The power conversion apparatus according to claim 3 or 4 as dependent on claim 1,
the state monitoring unit calculates a junction temperature of the switching element based on the switch off delay time, the estimated current of the collector current or the drain current, and the estimated voltage of the collector voltage or the drain voltage.
8. The power conversion apparatus according to claim 7,
the state monitoring unit calculates a temperature amplitude of a change in the joining temperature and a number of times the joining temperature changes by the temperature amplitude from the calculated time-series data of the joining temperature, and calculates a degree of wear of the switching element from the temperature amplitude and the number of times.
9. The power conversion apparatus according to claim 3 or 4 as dependent on claim 1,
the abnormality diagnosis unit determines an abnormality of a current value of the collector current or the drain current based on the switch off delay time, the estimated voltage of the collector voltage or the drain voltage, and the estimated current of the collector current or the drain current.
10. The power conversion apparatus according to claim 1 or 2,
the power conversion device includes a pulse number measurement unit that measures the number of pulses of the PWM command signal and the number of pulses of the feedback signal,
and detecting a malfunction of the gate drive circuit based on a result of comparison of the measured numbers of pulses.
11. A method for diagnosing a power conversion device includes:
a step 1 of estimating a collector current or a drain current and a collector voltage or a drain voltage at a timing when a switching element constituting a power conversion device is turned off;
a 2 nd step of estimating an operation state of the power conversion device based on a PWM command signal for driving the switching element, a feedback signal generated in accordance with a switching operation of the switching element, an estimated current of the collector current or the drain current, and an estimated voltage of the collector voltage or the drain voltage; and
and step 3, judging the abnormality of the power conversion device according to the estimated operation state of the power conversion device.
12. The diagnostic method of a power conversion apparatus according to claim 11,
the feedback signal is generated by comparing a voltage between the gate and the emitter or the source during a switching operation of the switching element with a switching-on reference voltage and a switching-off reference voltage, respectively.
13. The diagnostic method for a power conversion apparatus according to claim 11 or 12, further comprising:
a 4 th step of measuring an on period or an off period of the PWM command signal and an on period or an off period of the feedback signal; and
and a 5 th step of calculating a switching off delay time of the switching element based on the measured on period or off period of the PWM command signal and the measured on period or off period of the feedback signal.
14. The diagnostic method for a power conversion apparatus according to claim 11 or 12, further comprising:
a 4 th step of measuring a time from the turning-off of the switch of the PWM command signal to the turning-off of the switch of the feedback signal; and
and a 5 th step of calculating a switching off delay time of the switching element based on the measured time.
15. The diagnostic method of a power conversion apparatus according to claim 13 or 14 when dependent on claim 11, further comprising:
and 6, calculating the joint temperature of the switch element according to the switch off delay time, the estimated current of the collector current or the drain current and the estimated voltage of the collector voltage or the drain voltage.
16. The diagnostic method for a power conversion apparatus according to claim 15, further comprising:
and a 7 th step of calculating a temperature amplitude of the change of the joining temperature and the number of times the joining temperature changes by the temperature amplitude from the calculated time-series data of the joining temperature, and calculating a degree of wear of the switching element from the temperature amplitude and the number of times.
17. The diagnostic method of a power conversion apparatus according to claim 13 or 14 when dependent on claim 11, further comprising:
and 8, judging the current value of the collector current or the drain current is abnormal according to the switch off delay time, the estimated voltage of the collector voltage or the drain voltage and the estimated current of the collector current or the drain current.
18. The diagnostic method for a power conversion apparatus according to claim 11 or 12, further comprising:
a 9 th step of measuring the number of pulses of the PWM command signal and the number of pulses of the feedback signal, respectively; and
and a 10 th step of detecting a malfunction of a gate drive circuit of the switching element based on a result of comparison of the measured numbers of pulses.
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| JP2018-196372 | 2018-10-18 | ||
| JP2018196372A JP7085453B2 (en) | 2018-10-18 | 2018-10-18 | Diagnostic method for power converters and power converters |
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| CN111352003A (en) * | 2020-05-25 | 2020-06-30 | 北京中航科电测控技术股份有限公司 | Analysis system for electrical equipment faults |
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| JP7085453B2 (en) | 2022-06-16 |
| CN111092563B (en) | 2023-10-10 |
| JP2020065386A (en) | 2020-04-23 |
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