Current type aging test system and switching device aging test method

Abstract

The present invention relates to the technical field, and discloses a current-type aging test system and a switch device aging test method. The current-type aging test system is composed of six switch devices to form a three-phase inverter circuit, and an aging current source is connected to the three-phase inverter circuit. The aging current source is used to provide the aging current of the three-phase inverter circuit, and the aging current source can be changed accordingly according to the change of the AC current amplitude under the actual load condition of the three-phase inverter circuit. Compared with the traditional voltage-type aging test system, the current-type aging test system provided by the present invention only requires a test device and an aging current source, and does not require accompanying test components and rotating components such as motors, and the structure of the aging system is greatly simplified. At the same time, since there is no need to carry an accompanying test module or auxiliary, it is possible to avoid affecting the experimental process and the final test results due to the aging of the accompanying test module or the load, and can improve the reliability of the aging test operation and the accuracy of the aging of the switch device.

Description

Technical Field

[0001] The invention relates to the technical field of switch device aging test, and in particular to a current type aging test system and a switch device aging test method. Background Art

[0002] As an important mode of public transportation in large and medium-sized cities, rail transit systems are increasingly widely adopted for their large passenger capacity and freedom from traffic congestion. Among the main components of urban rail transit systems, rail transit trains play a vital role as a means of transportation, and the train traction converter provides traction or electric braking force for train operation by controlling the traction motor. Its operating reliability and service life directly affect the entire train. According to statistics, the failure rate of switching devices accounts for more than 30% of the failure rate of converter electrical components, and there is a great demand for online evaluation and prediction of the service life of large switching devices. At present, the industry usually uses a voltage-type aging system to monitor the aging status and predict the failure rate and life of IGBT devices in high-power traction converters. However, the voltage-type aging system needs to build a complete system based on the actual topology on the ground during the test, and conduct aging experiments according to the actual operating conditions of the train. Therefore, the system topology of the voltage-type aging system is complex and costly. Summary of the invention

[0003] Based on this, it is necessary to provide a current-type aging test system and a switching device aging test method to address the problems of complex system topology and high cost of traditional voltage-type aging systems.

[0004] A current type aging test system, comprising an aging current source and a three-phase inverter circuit, wherein the three-phase inverter circuit comprises a first switching device, a second switching device, a third switching device, a fourth switching device, a fifth switching device and a sixth switching device; the emitter of the first switching device is connected to the collector of the second switching device, and the connection point between the first switching device and the second switching device is used as a first connection terminal; the emitter of the third switching device is connected to the collector of the fourth switching device, and the connection point between the third switching device and the fourth switching device is used as a second connection terminal; the emitter of the fifth switching device is connected to the collector of the sixth ... The collectors of the switching devices are connected, and the connection point of the fifth switching device and the sixth switching device serves as the third connection terminal; the first connection terminal, the second connection terminal and the third connection terminal are short-circuited to each other; the positive output terminal of the aging current source is respectively connected to the collector of the first switching device, the collector of the third switching device and the collector of the fifth switching device, and the negative output terminal of the aging current source is respectively connected to the emitter of the second switching device, the emitter of the fourth switching device and the emitter of the sixth switching device; the aging current source is used to provide an aging current to the three-phase inverter circuit.

[0005] The above-mentioned current-type aging test system is composed of six switching devices to form a three-phase inverter circuit, and the aging current source is connected to the above-mentioned three-phase inverter circuit. The aging current of the three-phase inverter circuit composed of the switching devices is provided by the aging current source, and can be changed accordingly according to the change of the AC current amplitude under the actual load condition of the three-phase inverter circuit. Compared with the traditional voltage-type aging test system, the current-type aging test system provided by the present invention only requires the test device and the aging current source, and does not require accompanying test components and rotating components such as motors. The structure of the aging system is greatly simplified, the space occupied by the system is reduced, and the cost of the entire system is greatly reduced. At the same time, since there is no need to carry an accompanying test module or auxiliary, it is possible to avoid affecting the experimental process and the final test results due to the aging of the accompanying test module or the load, which can improve the reliability of the aging test operation and the accuracy of the aging of the switching device.

[0006] In one embodiment, the first switch device, the second switch device, the third switch device, the fourth switch device, the fifth switch device and the sixth switch device are all IGBT switch tubes.

[0007] A method for testing aging of switching devices, comprising initializing modulation parameters of a current-type aging test system, and calculating the total loss of switching devices in the current-type aging test system; judging whether the error between the total loss and a preset total loss is within a preset error range; if the error between the total loss and the preset total loss is within the preset error range, defining the current modulation parameters as an optimal solution and outputting the optimal solution; otherwise, iteratively updating the modulation parameters and calculating the losses again until the error between the new total loss and the preset total loss is within the preset error range, defining the new modulation parameters as an optimal solution and outputting the optimal solution; the current-type aging test system performs an aging test on a three-phase inverter circuit composed of switching devices according to the optimal solution, so that each switching device switches its switching state according to a preset modulation strategy.

[0008] In one of the embodiments, the preset modulation strategy is a five-segment space vector modulation strategy.

[0009] In one of the embodiments, the modulation parameters include a switching frequency and a duty cycle of the switching device and an aging current output by the aging current source.

[0010] In one of the embodiments, the preset total loss is obtained according to an aging test result of a voltage-type aging test system.

[0011] In one embodiment, the calculating of the total loss of the switching devices in the current-type aging test system includes respectively calculating the conduction loss and the switching loss of each switching device.

[0012] In one of the embodiments, calculating the conduction loss of each switching device includes performing curve fitting on the static curve of the switching device to obtain a linear expression of the collector-emitter voltage and the collector current of the switching device; and calculating the conduction loss within a switching cycle and the conduction loss within a modulation wave cycle according to the linear expression of the collector-emitter voltage and the collector current.

[0013] In one embodiment, calculating the switching loss of each switching device includes performing segmented curve fitting according to the switching transient characteristics of the switching device, integrating the loss of each segment, and calculating the loss energy of a single switch of the switching device; and calculating the switching loss within a modulation wave cycle based on the loss energy of a single switch of the switching device.

[0014] In one of the embodiments, a genetic algorithm is used to iterate the modulation parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A circuit topology diagram of a current-type aging test system according to one embodiment of the present invention;

[0016] Figure 2A flow chart of a method for testing an aging process of a switching device according to one embodiment of the present invention;

[0017] Figure 3 A current vector space distribution diagram of one embodiment of the present invention;

[0018] Figure 4 A flow chart of a method for calculating the conduction loss of each switching device according to one embodiment of the present invention;

[0019] Figure 5 The static characteristic curve of an IGBT according to one embodiment of the present invention;

[0020] Figure 6 A flow chart of a method for calculating switching losses of each switching device according to one embodiment of the present invention;

[0021] Figure 7 This is a flow chart of a loss equivalence algorithm based on a genetic algorithm according to one embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to understand the disclosure of the present invention more thoroughly and comprehensively.

[0023] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may also be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right", "upper", "lower", "front", "rear", "circumferential" and similar expressions used herein are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0025] At present, there are many problems in the industry for the aging status monitoring, failure rate and life prediction of IGBT devices in high-power traction converters. There are three main problems: First, the voltage-type aging system needs to build the actual operating environment of the high-power traction converter, but it is unrealistic to build a complete system based on the actual topology on the ground and conduct aging experiments according to the actual operating conditions of the train. Secondly, the duty cycle, modulation depth and aging current of the modulation strategy are generally fixed or change slightly during the aging experiment, while these parameters are changing all the time and the change range is large in actual situations. Therefore, in the current aging experiment of power devices, the aging test results achieved for a single switching device (IGBT module is the most common) are difficult to apply to the service life evaluation or service life prediction of IGBT modules under actual load conditions. Finally, when aging experiments are used to simulate actual working conditions, there are high requirements for the voltage and power of the power supply. When aging a 1500V inverter, considering the ability to compensate for the total loss of the system, the 1500V DC power supply voltage needs to provide hundreds of amperes of current, which results in a large power. In addition, this type of power supply is very expensive. The current type aging test system provided by the present invention well solves the problems of complex system structure and high cost under actual topology.

[0026] Figure 1 The circuit topology diagram of the current type aging test system of one embodiment of the present invention, in one embodiment, the current type aging test system includes an aging current source 100 and a three-phase inverter circuit 200. Since the load of the train traction converter is usually 4 motors, at least 8 motors and 2 inverter modules are required in the traditional voltage type aging towing system, including the test (DUT) and the accompanying test part. The structure of the current type aging test system provided by the present invention is much simpler, only the test component is required, and the accompanying test component and the motor are removed, which greatly reduces the space occupied and the cost of the system. The three-phase inverter circuit 200 includes a first switch device 210, a second switch device 220, a third switch device 230, a fourth switch device 240, a fifth switch device 250 and a sixth switch device 260.

[0027] The emitter of the first switching device 210 is connected to the collector of the second switching device 220, and the connection point of the first switching device 210 and the second switching device 220 serves as the first connection terminal. The emitter of the third switching device 230 is connected to the collector of the fourth switching device 240, and the connection point of the third switching device 230 and the fourth switching device 240 serves as the second connection terminal. The emitter of the fifth switching device 250 is connected to the collector of the sixth switching device 260, and the connection point of the fifth switching device 250 and the sixth switching device 260 serves as the third connection terminal. The first connection terminal, the second connection terminal and the third connection terminal are short-circuited to each other. The positive output terminal of the aging current source 100 is connected to the collector of the first switching device 210, the collector of the third switching device 230 and the collector of the fifth switching device 250, respectively. The negative output terminal of the aging current source 100 is connected to the emitter of the second switching device 220 , the emitter of the fourth switching device 240 , and the emitter of the sixth switching device 260 , respectively. The aging current source 100 is used to provide an aging current to the three-phase inverter circuit.

[0028] In the current-type aging test system of the present application, a circuit topology combining an aging current source 100 and a three-phase inverter circuit composed of six switching devices is adopted. The aging current of the switching device is provided by the aging current source 100, and corresponding changes can be made according to the change of the AC current amplitude of the power module of the three-phase inverter circuit under actual load conditions. On the one hand, the support capacitor is removed from the three-phase inverter circuit composed of six switching devices of the present invention. This is because when the capacitor is charged with a constant current, the voltage rises linearly. Removing the support capacitor can prevent overvoltage. It should be noted that the aging object of the current-type aging test system provided by the present invention is mainly the switching device, which has nothing to do with the capacitor, so this treatment will not affect the aging effect; on the other hand, the output side is short-circuited in order to simulate and replace the high-voltage and high-current control method by using a low-voltage and high-current control method.

[0029] Compared with the traditional voltage-type aging drag system, this system only needs the device under test, without accompanying test components and rotating components such as motors. The system structure is greatly simplified, the space occupied by the system is reduced, and the cost of the entire system is greatly reduced. The current-type aging test system ensures that during the uninterrupted and continuous aging of the device under test, the experimental process and the final test results can be avoided due to the aging of the accompanying test module or load, and the reliability of the system operation and the accuracy of the aging of the switch device can be improved.

[0030] In one embodiment, the first switch device, the second switch device, the third switch device, the fourth switch device, the fifth switch device and the sixth switch device are all IGBT switch tubes. The three-phase inverter circuit in the current type aging test system provided by the present invention is composed of six IGBT switch tubes, and the aging object is mainly the IGBT switch tube, and the aging current source 100 is used to provide the aging current of the IGBT switch tube.

[0031] The present invention also provides a switching device aging test method. Figure 2 1 is a method flow chart of a switching device aging test method according to one embodiment of the present invention. In one embodiment, the switching device aging test method includes the following steps S100 to S500.

[0032] S100: Initializing modulation parameters of a current-type aging test system, and calculating total losses of switching devices in the current-type aging test system.

[0033] S200: Determine whether the error between the total loss and the preset total loss is within a preset error range.

[0034] S300: If the error between the total loss and the preset total loss is within a preset error range, the current modulation parameter is defined as an optimal solution and outputted.

[0035] S400: Otherwise, the modulation parameters are iteratively updated and the loss is calculated again until the error between the new total loss and the preset total loss is within a preset error range, and the new modulation parameters are taken as the optimal solution and output.

[0036] S500: The current-type aging test system performs an aging test on a three-phase inverter circuit composed of switch devices according to an optimal solution, so that each switch device switches its switch state according to a preset modulation strategy.

[0037] Since the generation of loss is the main cause of aging of switching devices, the switching device aging test method provided by the present invention is used to perform equivalent loss on switching devices during aging experiments on switching devices using a current-type aging test system. In order to enable the current-type aging method to achieve the same aging effect as the voltage-type aging method and actual working conditions, the loss equivalence algorithm of the switching device aging test method needs to consider the equivalence of switching device losses on three scales: within a switching cycle, within a modulation wave cycle, and within a train working cycle (traction, inertia, and braking). The working cycle is composed of several modulation wave cycles, and the modulation wave cycle is composed of several switching cycles. Therefore, the above three scales can achieve loss equivalence on any scale.

[0038] In actual operation, the DC bus voltage of the voltage-source inverter VSI is much higher than the DC bus voltage of the current-source inverter CSI, resulting in different voltage variation ranges during the device switching process. In addition, the number of switch devices turned on when the two aging circuits are working normally is also different. VSI has a total of 3 IGBTs turned on at any time, while CSI has a total of 2 IGBTs turned on at any time. Due to the above two problems, there is a large difference in the loss of the switch devices in the two aging methods, so the loss equivalence cannot be achieved within a switching cycle. Through the actual construction of the inverter module for simulation analysis, it can be seen that on the one hand, the average value and change trend of the junction temperature of the switch device depend on the operating conditions of the train; on the other hand, the slight fluctuation of the junction temperature is mainly affected by the heating of the switch device during the modulation wave period, and is less affected by the heating during the switching period. Therefore, it is only necessary to ensure that the loss of the switch device can be equivalent under the two aging strategies within the modulation wave period.

[0039] First, the modulation parameters of the current-type aging test system are initialized to be the same as the modulation parameters in the voltage-type aging method, and the total loss of the switching devices in the current-type aging test system under the initialized modulation parameters is calculated. Then, it is determined whether the loss of the switching devices in the current system is the same as the loss under the voltage-type aging method or whether the loss can be equivalent within a certain error range. If it meets the requirements, each parameter is determined to be the optimal solution, and the value of each parameter at this time is output. Otherwise, an iterative operation is performed to update each parameter, and the loss calculation is performed on the updated modulation parameters again to determine whether the updated total loss meets the judgment conditions of the optimal solution. The above process is repeated until the conditions are met and the optimal solution is output. Finally, the modulation parameters in the current-type aging test system are adjusted to the optimal solution, and an aging test is performed on the three-phase inverter circuit composed of the switching devices. In the aging test, each switching device switches its switch state according to the preset modulation strategy to equivalently simulate the load condition of the test component DUT in the actual application scenario, so as to ensure that the aging test results are as close to the actual application scenario as possible.

[0040] In one embodiment, the preset modulation strategy is a five-segment space vector modulation strategy. Figure 1In a three-phase inverter circuit composed of six switching devices, the first switching device, the third switching device and the fifth switching device constitute the upper bridge arm group of the three-phase inverter circuit, and the second switching device, the fourth switching device and the sixth switching device constitute the lower bridge arm group of the three-phase inverter circuit. In addition, the first switching device and the second switching device, the third switching device and the fourth switching device, the fifth switching device and the sixth switching device are respectively the upper and lower switching tubes of the same bridge arm. Since the DC side of the three-phase current-type inverter circuit is not allowed to be open at any time, during normal operation, at any time, only one switching device in the upper bridge arm group and the lower bridge arm group of the circuit is in a working state. The above-mentioned three-phase inverter circuit has two working states, namely, the direct-connection state and the non-direct-connection state. The direct-connection state refers to the upper and lower switching tubes of the same bridge arm being turned on at the same time, and the non-direct-connection state refers to the upper and lower bridge arms of different bridge arms each having a switching tube turned on. Each bridge arm in the three-phase inverter circuit has three working states S j (j = a, b, c) is shown in the following formula:

[0041]

[0042] Since the three-phase inverter circuit has three bridge arms, the switch states of the three bridge arms are arranged and combined, and it can be known that the three-phase inverter circuit has a total of 9 working states. In each working state, 2 switch devices are turned on and 4 switch devices are turned off. Among the 9 working states, there are 6 non-zero state combinations and 3 zero state combinations. The specific switch states are shown in Table 1.

[0043] Table 1 Three-phase inverter circuit switch status table

[0044]

[0045]

[0046] In this embodiment, a five-segment space vector modulation strategy is adopted as the working state simulation strategy of the three-phase inverter circuit. The specific current vector space distribution diagram is as follows: Figure 3 As shown, I7, I8, and I9 are all current zero vectors, located at the origin. According to the distribution of the 9 working states of the three-phase inverter circuit in the current vector space, the current vector space can be divided into 6 sectors. The state switching of each switching device in each sector within a switching cycle is shown in Table 2. When the aging test is performed on the three-phase inverter circuit, each switching device in the three-phase inverter circuit switches the working state of each switching device according to the five-segment space vector modulation strategy to simulate the working conditions in the actual application scenario.

[0047] Table 2 Switching status of each sector

[0048] Sector Switch Sector I #8→#6→#2→6#→#8 Sector II #7→#2→#3→#2→#7 Sector III #9→#3→#1→#3→#9 Sector IV #8→#1→#5→#1→#8 Sector V #7→#5→#4→#5→#7 Sector VI #9→#4→#6→#4→#9

[0049] In one of the embodiments, the modulation parameters include the switching frequency, duty cycle and aging current output by the aging current source of the switching device. The switching frequency, duty cycle (i.e., modulation depth) of the switching device and the aging current of the aging current source are the constraints of the loss equivalent algorithm in the aging test method of the switching device, and the optimal solution of each parameter is found through iterative calculation. When performing the aging test, the switching frequency, duty cycle (i.e., modulation depth) of the switching device and the aging current of the aging current source are adjusted to the values ​​of the optimal solution, which can ensure that the current-type aging test system can be as close to the actual application scenario as possible. The aging characteristics of the device under test DUT are simulated by controlling and changing the working state of the device under test DUT, and the AC side fundamental current characteristics of the device under test DUT are simulated by adopting different modulation strategies and changing the amplitude of the aging current.

[0050] In one of the embodiments, the preset total loss is obtained according to the aging test results of the voltage-type aging test system. In this embodiment, the loss equivalence algorithm in the switching device aging test method takes the minimum value of the difference between the total loss of the switching device under the current-type and voltage-type aging methods as the objective function, and judges whether the total loss of each switching device in the current-type aging test system is the same as the total loss under the voltage-type aging method or whether the loss equivalence can be achieved within a certain error range. If the judgment condition is met, the modulation parameters at this time are judged to be the optimal solution, and the values ​​of the modulation parameters at this time are output.

[0051] In one embodiment, the calculation of the total loss of the switching device in the current current-type aging test system includes calculating the conduction loss and switching loss of each switching device respectively. Generally, the loss of the switching device includes the conduction loss and switching loss. Therefore, when calculating the total loss of the switching device in the current-type aging test system, it is necessary to calculate the conduction loss and switching loss of each switching device respectively.

[0052] Figure 4 This is a flow chart of a method for calculating the conduction loss of each switching device according to one embodiment of the present invention. In one embodiment, calculating the conduction loss of each switching device includes the following steps S110 to S120.

[0053] S110: performing curve fitting on a static curve of the switching device to obtain a linear expression of the collector-emitter voltage and the collector current of the switching device.

[0054] S120: Calculate the conduction loss in one switching cycle and the conduction loss in one modulation wave cycle respectively according to the linear expression of the collector-emitter voltage and the collector current.

[0055] Figure 5This is an IGBT static characteristic curve of one embodiment of the present invention. When calculating the conduction loss of each switch device, it is necessary to perform curve fitting on the static curve of the IGBT switch tube. Figure 5 After fitting the IGBT static characteristic curve shown in the figure, the linear expression of the collector-emitter voltage and collector current of the IGBT can be derived, which is:

[0056] U CE(sat) =R T I C +U CEO ;

[0057] Among them, U CE(sat) is the collector-emitter voltage, R T is the forward resistance of the switching device, I C is the collector current, U CEO is the trip voltage of the switching device.

[0058] According to the linear expression of the collector-emitter voltage and the collector current, the conduction loss in one switching cycle and the conduction loss in one modulation wave cycle can be calculated respectively. The conduction loss in the switching cycle is calculated according to the expression of the conduction loss in the switching cycle, and the conduction loss in one switching cycle is:

[0059] P Tcon =U CE *I C =(R T I C +U CEO )*I C =f(I C ,T uj );

[0060] Among them, P Tcon is the conduction loss in one switching cycle, U CE is the collector-emitter voltage, I C is the collector current, R T is the forward resistance of the switching device, U CEO is the switching device's trip voltage, f(I C ,T uj ) is the power function, T uj is the junction temperature of the switching device.

[0061] The conduction loss in a modulation wave cycle is calculated according to the following expression of conduction loss in a modulation wave cycle. The conduction loss in a modulation wave cycle is:

[0062] Among them, P Tcond is the conduction loss in one modulation wave cycle, T0 is the power frequency cycle, T onis the conduction time of the switching device in one power frequency cycle, u CE (t) is the collector-emitter voltage function, i(t) is the aging current function, m is the modulation depth, is the PWM modulation function, ω is the frequency, t is the time, The initial phase.

[0063] Figure 6 This is a flow chart of a method for calculating the switching loss of each switching device according to one embodiment of the present invention. In one embodiment, calculating the switching loss of each switching device includes the following steps S130 to S140.

[0064] S130: Perform segmented curve fitting according to the switching transient characteristics of the switching device, integrate the loss of each segment, and calculate the loss energy of one switching of the switching device.

[0065] S140: Calculate the switching loss within one modulation wave cycle according to the loss energy of one switching of the switching device.

[0066] According to the transient characteristics of the IGBT switch tube, segmented curve fitting is performed, and the loss of each segment of the curve is integrated to calculate the loss energy of a switch state change. The loss energy of a switch is:

[0067]

[0068] Among them, E on E is the loss energy of the switch device during conduction. off is the energy loss when the switch is turned off, t on is the on-time of the switching device, t off is the turn-off time of the switching device, u CE (t) is the collector-emitter voltage function, i(t) is the aging current function, and t is time. In this embodiment, the on-time and off-time of the switch device are defined as follows: the time from the gate voltage rising to 10% of the driving voltage to the collector current rising to 90% of the test current is the on-time, and the time from the gate voltage falling to 90% of the driving voltage to the collector current rising to 10% of the test current is the off-time.

[0069] After calculating and obtaining the loss energy of a switching device once, the switching loss within a modulation wave cycle can be calculated according to the loss energy of a switching device once. The switching loss within a modulation wave cycle is:

[0070]

[0071] Among them, P SWis the switching loss within one modulation wave cycle, f is the switching frequency of the power switch device, T0 is the power frequency cycle, T SW is the switching time of the power switch device in one power frequency cycle, E on is the loss energy of the power switch device when it is turned on, E off is the energy loss when the power switch is turned off, t is the time, and α is the electrical angle.

[0072] In one of the embodiments, a genetic algorithm is used to iterate the modulation parameters. Figure 7 This is a flowchart of a loss equivalence algorithm based on a genetic algorithm according to one embodiment of the present invention. In the loss equivalence algorithm of the switch device aging test method provided by the present invention, the minimum value of the total loss difference of the switch device under the two aging modes of current type and voltage type is used as the objective function. At the same time, the switching frequency, duty cycle (modulation depth), and aging current are used as constraints. The genetic algorithm is used to iterate the modulation parameters to seek the optimal solution. The specific loss equivalence and the process of finding the optimal value of each parameter are detailed in Figure 7 .

[0073] First, the population is initialized. In this embodiment, the population is the modulation parameters such as switching frequency, duty cycle (modulation depth), and aging current. Make the values ​​of each parameter in the initialized population the same as the values ​​of each parameter in the voltage-type aging method. After completing the initialization, the fitness is calculated. In this embodiment, the fitness is the total loss of the current switching device. According to the changes in the junction temperature of the switching device, these parameter values ​​are updated in real time, the total loss of the current switching device is calculated, and it is judged whether the current total loss is the same as the total loss under the voltage-type aging method or within a certain error range. The total loss can be judged by judging whether the heating of the switch tube is the same as the heating under the voltage-type aging method or within a certain error range. If so, the values ​​of the modulation parameters such as the current switching frequency, duty cycle, and aging current are determined to be the optimal solution and output. Otherwise, the genetic operations such as selection, crossover, and mutation of the genetic algorithm are used to iteratively generate a new population. In this embodiment, the new population refers to the update of the switching frequency, duty cycle, and aging current. The above process is repeated until the optimal solution judgment condition is met and the optimal solution is output.

[0074] The switching device aging test method provided by the present invention is used to perform loss equivalent calculation, and the minimum value of the total loss difference of the switching device under the two aging modes of current type and voltage type is used as the objective function. At the same time, the switching frequency, duty cycle (modulation depth), and aging current are used as constraints, and the modulation parameters are iterated by genetic algorithm to seek the optimal solution. The modulation parameters in the current type aging test system are adjusted to the value of the optimal solution to perform aging test on the switching device IGBT. By simulating the aging characteristics of the IGBT, and by adopting different modulation strategies and changing the aging current amplitude, the AC side fundamental current characteristics of the three-phase inverter are simulated. The current type aging test system can perform aging test on the three-phase inverter composed of IGBT independently of the existing devices of the train traction system, and is universal for the power devices of the current mainstream manufacturers. The current type aging test system provided by the present invention focuses on the aging of the switching device, and will not affect the aging test results due to the aging of other components. It can equivalently simulate the load conditions of the three-phase inverter in the actual application scenario, thereby ensuring that the aging test results are as close to the actual application scenario as possible. The system structure is simple, which not only greatly reduces the complexity and cost of the system, but also simplifies the aging experiment process and ensures good system operation reliability.

[0075] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0076] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A switching device aging test method, It is characterized in that The switching device aging test method is applied to a current type aging test system, and the current type aging test system comprises: An aging current source and a three-phase inverter circuit, the three-phase inverter circuit comprising a first switch device, a second switch device, a third switch device, a fourth switch device, a fifth switch device and a sixth switch device; the emitter of the first switch device is connected to the collector of the second switch device, and the connection point of the first switch device and the second switch device is used as a first connection terminal; the emitter of the third switch device is connected to the collector of the fourth switch device, and the connection point of the third switch device and the fourth switch device is used as a second connection terminal; the emitter of the fifth switch device is connected to the collector of the sixth switch device, and the connection point of the fifth switch device and the sixth switch device is used as a third connection terminal; the first connection terminal, the second connection terminal and the third connection terminal are short-circuited to each other; the positive output terminal of the aging current source is respectively connected to the collector of the first switch device, the collector of the third switch device and the collector of the fifth switch device, and the negative output terminal of the aging current source is respectively connected to the emitter of the second switch device, the emitter of the fourth switch device and the emitter of the sixth switch device; the aging current source is used to provide an aging current to the three-phase inverter circuit; The switching device aging test method comprises: Initializing modulation parameters of the current-type aging test system and calculating the total loss of the switching devices in the current-type aging test system; Determine whether the error between the total loss and a preset total loss is within a preset error range, wherein the preset total loss is obtained according to an aging test result of a voltage-type aging test system; If the error between the total loss and the preset total loss is within a preset error range, the current modulation parameter is defined as an optimal solution and output; Otherwise, the modulation parameters are iteratively updated and the loss is calculated again until the error between the new total loss and the preset total loss is within a preset error range, and the new modulation parameters are taken as the optimal solution and output; The current-type aging test system performs an aging test on a three-phase inverter circuit composed of switch devices according to the optimal solution, so that each switch device switches its switch state according to a preset modulation strategy; The switching device aging test method further comprises: Modulation parameters are iterated using genetic algorithm; The iterating of the modulation parameters using the genetic algorithm comprises: Initializing a population, wherein the population is a modulation parameter, and the modulation parameter is a switching frequency, a duty cycle, and an aging current; Make the values ​​of each modulation parameter in the initialization population the same as the values ​​of each parameter in the voltage-type aging method; After the initialization is completed, the fitness is calculated, and the fitness is the total loss of the current switching device; updating the value of the modulation parameter in real time according to the change of the junction temperature of the switching device, calculating the total loss of the current switching device, and judging whether the current total loss is the same as the total loss under the voltage-type aging method, or is within a certain error range; If so, the current modulation parameter value is determined to be the optimal solution and output.

2. The switching device aging test method according to claim 1, It is characterized in that The preset modulation strategy is a five-segment space vector modulation strategy.

3. The switching device aging test method according to claim 1, It is characterized in that The calculation of the total loss of the switching device in the current current type aging test system includes: Calculate the conduction loss and switching loss of each switching device respectively.

4. The switching device aging test method according to claim 3, It is characterized in that Calculation of conduction loss of each switching device includes: Perform curve fitting on the static curve of the switching device to obtain the linear expression of the collector-emitter voltage and collector current of the switching device; The conduction loss in one switching cycle and one modulation wave cycle are calculated respectively according to the linear expressions of the collector-emitter voltage and the collector current.

5. The switching device aging test method according to claim 4, It is characterized in that Calculation of the switching losses of each switching device includes: According to the switching transient characteristics of the switching device, segmented curve fitting is performed, the loss of each segment is integrated, and the loss energy of the switching device once is calculated; The switching loss within one modulation wave cycle is calculated based on the loss energy of the switching device once.

6. The switching device aging test method according to claim 1, It is characterized in that The three-phase inverter circuit has 9 working states in total. In each working state, 2 switch devices are turned on and 4 switch devices are turned off.

7. The switching device aging test method according to claim 6, It is characterized in that Among the 9 working states, there are 6 non-zero state combinations and 3 zero state combinations.

8. The switching device aging test method according to claim 1, It is characterized in that The parameter value is updated in real time according to the change of the junction temperature of the switching device, the total loss of the current switching device is calculated, and whether the current total loss is the same as the total loss under the voltage-type aging method or is within a certain error range, including: If not, the selection, crossover and mutation genetic operations of the genetic algorithm are used to iteratively generate a new population, wherein the new population refers to updating the switching frequency, duty cycle and aging current.

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