A double pulse test circuit and method for silicon carbide combination device

Abstract

The present invention discloses a double pulse test circuit and method for a silicon carbide combination device, and belongs to the fields of power electronics technology and electrical engineering technology. Aiming at the problem that most DC power supplies in reality have a constant current output mode, but their output voltage cannot follow the load changes and cannot be used as an ideal current source for traditional current source type double pulse experiments, a test circuit and method for double pulse testing of a voltage reverse blocking silicon carbide combination device for a current source type inverter are proposed. A double pulse test circuit and method for a silicon carbide combination device proposed by the present invention adopts an equivalent method of a voltage type power supply and a large inductor in series, and accurately controls the voltage and load current of the voltage reverse blocking silicon carbide combination device by pre-charging the inductor and capacitor. An inductor freewheeling path is designed to realize the automatic release of energy on the inductor after the experiment. This method can effectively reflect the switching characteristics of the voltage reverse blocking combination device.

Description

Technical Field

[0001] The invention relates to the field of power electronics technology and electrical engineering technology, and in particular to a double pulse test circuit and method for a silicon carbide combination device. Background Art

[0002] Since the widely used silicon-based semiconductor devices represented by IGBT and MOSFET do not provide the reverse voltage blocking capability required by the current source inverter topology, the traditional voltage source inverter (VSI) has always been more popular than the current source inverter (CSI). However, the CSI topology has advantages such as strong short-circuit resistance and sinusoidal output voltage and current waveforms on the AC side due to the large inductance on the DC side and the filter capacitor on the AC side. Therefore, the long-neglected CSI topology has once again attracted the attention of domestic and foreign scholars.

[0003] However, the current research on CSI is still mainly focused on the modulation strategy, power circuit topology optimization and other inverter system-level research. There is little research on the switching characteristics of the voltage reverse blocking devices used in CSI, and there is a lack of optimization methods for the switching trajectory of the voltage reverse blocking devices. In addition, the research on the topology of the traditional current source type double pulse test circuit is still mainly in the simulation stage, that is, the DC side is tested with an ideal constant current source; therefore, a double pulse test circuit and method for silicon carbide combination devices is proposed. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention proposes a double pulse test circuit and method for a silicon carbide combination device. Based on the traditional current source type double pulse test circuit that requires an ideal constant current source, the present invention optimizes and proposes a voltage reverse blocking type silicon carbide combination device double pulse test circuit for a current source type inverter, improves the triggering method of the switching timing of the device under test in the traditional current source type double pulse test, and realizes the optimization of the switching waveform without affecting the switching characteristics of the device under test, thereby avoiding reverse breakdown of the diode in the voltage reverse blocking type silicon carbide composite device.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A double pulse test circuit for a silicon carbide combination device includes a DC power supply V dc1 With large capacitor C dc Parallel connection, used to provide a stable voltage to the device under test, full-controlled switch tube S dc Connected to large capacitor C dc With inductance L dc Between, control the DC power supply V dc1 Whether to give inductance L dc Power supply; diode D f Cathode and switch tube S dcThe source is connected, the anode is connected to the DC power supply V dc1 The negative pole is connected to the inductor L dc Freewheeling current provides a path; SiC MOSFET S 1 With SiC Schottky diode D 1 Connected in series, forming the first switch tube with reverse voltage blocking function, SiC MOSFET S 3 With SiC Schottky diode D 3 The third switch tube is composed of the first and third combined switch tubes as the device under test; the capacitor C is connected between the first and third switch tubes, which is equivalent to the filter capacitor on the AC side of the current source inverter; the manual switch S c With DC power supply V dc2 In series, connected to both ends of capacitor C, used to pre-charge capacitor C; manual switch S d With resistor R d Connected to both ends of capacitor C to discharge capacitor C.

[0007] Furthermore, the DC power supply V dc1 The voltage value is always greater than the DC power supply V dc2 Voltage value.

[0008] Furthermore, an RC buffer circuit is connected in parallel at both ends of the diode of the third switch tube.

[0009] Furthermore, a test method for a double pulse test circuit of a silicon carbide combination device includes the following steps:

[0010] The first and third switch tubes of the device under test are connected to both ends of the capacitor C, respectively providing a flow path for the inductor current. The conduction of the first switch tube is equivalent to the zero vector effect in the three-phase current source inverter, and the conduction of the third switch tube is equivalent to the active vector effect in the three-phase current source inverter.

[0011] Close the manual switch S c , pre-charge the capacitor C; after the voltage of the capacitor C rises to the test value required by the test condition of the device under test, disconnect the manual switch S c ;

[0012] First turn on the DC side switch tube S dc and the first switch tube, by controlling the on-time, the inductor L dc The current is increased to the test value of the test condition required by the device under test;

[0013] In the first switch MOSFET S 1 The third switch is turned on in advance before the shutdown signal arrives, so that the first and third switches are turned on alternately, which is equivalent to the switching characteristics of the overlapping conduction in the three-phase current source inverter. The overlapping time is determined by the MOSFET S in the first switch.1 The turn-off speed is determined to ensure that MOSFET S 1 Before MOSFET S is completely turned off 3 It is fully turned on, the inductor L dc After the current is switched from the first switch tube to the third switch tube, it enters the first pulse stage of the double pulse test. The action time of this stage should be as short as possible to ensure that the inductance L dc The current and the voltage on capacitor C hardly change much;

[0014] Keep the trigger signal of the third switch tube at a high level, turn on the first switch tube, and the inductor L dc The current switches again, and the double pulse test circuit works in the zero vector state. The action time of this stage also needs to be as short as possible. After the first switch tube is turned off, the second pulse stage of the double pulse test begins. The test is over, and the switching characteristics of the device under test can be determined by measuring the switching trajectory of the device under test.

[0015] After the test, turn off the DC side switch tube S dc , so that the DC power supply V dc1 Stop charging the inductor, turn on the third switch tube, turn off the first switch tube, and the current will flow from the inductor L dc , the third switch tube, capacitor C, freewheeling diode D f This circuit flows through the inductor L dc All the energy on the capacitor is used to charge the capacitor C;

[0016] Finally, turn off the third switch tube and manually close switch S d , releasing the energy on capacitor C.

[0017] Furthermore, the inductor L dc The inductance value meets the following conditions: dc After charging, when the first switch tube switches to the third switch tube, the inductor L dc The current does not change.

[0018] Furthermore, the capacitance of the capacitor C satisfies the following conditions: during the switching period, the capacitor C can be equivalent to a voltage source, so that the operating conditions of the on and off processes of the device under test are the same, that is, the voltage across the device under test and the current flowing through the device remain unchanged when it is turned on and off;

[0019] After the double pulse test, the inductor L dc The energy will be used to charge capacitor C, which is connected to inductor L dc After the energy is released, the voltage on capacitor C remains below the rated voltage.

[0020] Furthermore, a storage medium stores a computer-executable program, which is used to implement a double-pulse test method for a silicon carbide combination device when executed by a processor.

[0021] Further, an electronic device includes: at least one memory for storing a program;

[0022] At least one processor is used to load the program to execute the double pulse testing method for silicon carbide combination devices.

[0023] Furthermore, a test device for double pulse testing of a silicon carbide combination device includes the double pulse testing circuit of the silicon carbide combination device.

[0024] Beneficial effects of the present invention:

[0025] A double pulse test circuit and method for a silicon carbide combination device disclosed in the present invention does not require additional construction of a constant current source, so that a new double pulse test experiment of a current source can simply and reliably test the switching trajectory of a voltage reverse blocking device.

[0026] The present invention discloses a double pulse test circuit and method for a silicon carbide combination device, which realizes the safe release of energy of passive devices in the circuit and can complete the test by controlling the switching device to be turned on for a short time as in a voltage source type double pulse test, thus filling the gap in the double pulse test experimental method for a two-level power converter.

[0027] The present invention discloses a method of precharging large inductors and large capacitors to achieve flexible control of the working conditions of the voltage reverse blocking device, solving the problem that the opening and closing of the traditional current source type double pulse test device is difficult to test under the same experiment and the same working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the accompanying drawings.

[0029] Figure 1 A double pulse test circuit for a silicon carbide combination device of the present application;

[0030] Figure 2 The switching timing waveform of the double pulse test circuit of the silicon carbide combination device of the present application;

[0031] Figure 3 This is a schematic diagram of an experimental waveform when the first switch tube is turned on without an RC buffer circuit in the present application;

[0032] Figure 4 This is a schematic diagram of an experimental waveform when the first switch tube is turned on with an RC buffer circuit of the present application;

[0033] Figure 5This is an experimental waveform diagram when the first switch tube of the present application is turned on;

[0034] Figure 6 This is an experimental waveform diagram when the first switch tube of the present application is turned off;

[0035] Figure 7 A test circuit diagram of the non-ideal inductor energy release method of the present application;

[0036] Figure 8 This is an experimental waveform diagram of the non-ideal inductor energy release method of the present application when the first switch tube is turned off. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0039] The double pulse test circuit for the voltage reverse blocking synthesis device of the current source inverter disclosed in the present application is as follows: Figure 1 As shown, the double pulse test circuit mainly includes: a DC power supply V dc1 With large capacitor C dc Parallel connection, used to provide a stable voltage to the device under test, full-controlled switch tube S dc Connected to capacitor C dc With inductance L dc Between, control the DC power supply V dc1 Whether to give inductance L dc Power supply; diode D f Cathode and switch tube S dc The source is connected, the anode is connected to the DC power supply V dc1 The negative pole is connected to the inductor L dc Freewheeling current provides a path; SiC MOSFET S 1 With SiC Schottky diode D 1 Connected in series, forming the first switch tube with reverse voltage blocking function, SiC MOSFET S3 With SiC Schottky diode D 3 The third switch tube is composed of the first and third combined switch tubes as the device under test; the capacitor C is connected between the first and third switch tubes, which is equivalent to the filter capacitor on the AC side of the current source inverter; the manual switch S c With DC power supply V dc2 In series, connected to both ends of capacitor C, used to pre-charge capacitor C; manual switch S d With resistor R d Connected to both ends of capacitor C to discharge capacitor C.

[0040] The switch triggering timing and related theoretical waveforms of the double pulse test circuit of the voltage reverse blocking silicon carbide combination device proposed by the present invention are as follows: Figure 2 As shown, compared with the traditional current source type double pulse test circuit, the method proposed in the present invention adds a capacitor pre-charging process and a passive device discharge process after the experiment, making the test experiment safer and more reliable. The first and third switch tubes of the device under test are connected to both ends of the capacitor C before the experiment. The entire test experiment process can be divided into the following 6 stages:

[0041] (1)T 0 Stage: In this stage, all MOSFETs are in the off state, and the switch S is manually closed. c , pre-charge the capacitor C, so that the capacitor voltage rises to the voltage value required by the test condition of the device under test, so that the voltage across the device under test can be flexibly and accurately controlled. After the pre-charging is completed, manually cut off the switch S c , then the capacitor can be approximately equivalent to a voltage source. It should be noted that the capacitance of the capacitor should be as large as possible, and the voltage on the capacitor must be always less than the DC side voltage V dc1 , so that the inductor current will not drop during the experiment, ensuring that the turn-on and turn-off processes of the device under test are carried out under the same working conditions.

[0042] (2)T 1 Stage: This process is the inductance L dc The main function of the pre-charging process is to increase the inductor current to the current value required by the device under test. 0 At the same time, MOSFET S is turned on dc and S 1 ,,The voltage reverse blocking type silicon carbide combination device double pulse test system for current source inverter acts on the zero vector stage. When the inductor pre-charging process is about to end, the MOSFET S is turned on in advance. 3 , simulating the characteristics of switch overlap in CSI. The overlap time is determined by the MOSFET S in the first switch tube. 1 The turn-off speed is determined to ensure that MOSFET S 1Before MOSFET S is completely turned off 3 It is fully conductive.

[0043] (3)T 2 Stage: At t 1 Turn off MOSFET S at all times 1 , the voltage reverse blocking type silicon carbide combination device double pulse test system switches from the first switch tube to the third switch tube, that is, switches from the zero vector to the active vector. This stage belongs to the first pulse test stage of the double pulse test. It should be noted that the action time of this stage should be as short as possible, on the one hand to ensure that the inductor current remains almost unchanged, and on the other hand to prevent the capacitor from being overcharged, so that the capacitance remains almost unchanged.

[0044] (4)T 3 Stage: MOSFET S 1 In t 2 At this moment, the current is switched from the branch where the third switch tube is located to the branch where the first switch tube is located. This process mainly simulates the switching process of CSI switching from active vector to zero vector. 1 The action time of this stage also needs to be as short as possible to ensure that the inductor current remains almost unchanged and the turn-on and turn-off of the device under test are measured under the same working conditions as much as possible.

[0045] (5)T 4 Phase: This phase belongs to the second pulse test phase of the double pulse test, and its characteristics are similar to T 2 Different from the traditional current source double pulse test system, this stage is 4 The moment will no longer conduct S 1 .

[0046] (6)T 5 Stage:t 4 Turn off MOSFET S at all times dc , so that the DC side power supply V dc1 No longer give inductor L dc Power is supplied. At this time, the double pulse test has ended and the energy in the passive components needs to be released. 3 When the inductor current is turned on, the inductor current will flow from the inductor L dc , S 3 , D 3 , capacitor C and freewheeling diode D f The loop is freewheeling, and all the energy in the inductor is used to charge the capacitor C, so the current shows a linear downward trend. After the current drops to zero, manually close the switch S d , all the energy on capacitor C is released.

[0047] Figure 3Figure 2 is the switching waveform of the double pulse test system of the voltage reverse blocking SiC combination device when the active vector switches back to the zero vector under the condition of the device load current of 40A. 3 The presence of junction capacitance at both ends of the diode D 3 There will be a reverse recovery process when turning off and on, and the stray inductance coupling with the loop will cause overshoot and oscillation of the voltage and current waveforms. Figure 3 Middle diode D 3 The voltage waveform at both ends and the current waveform of the first switch tube both oscillate for a long time. In order to reduce the influence of the diode reverse recovery process on the switching characteristics of the device under test in the experiment and avoid the reverse breakdown of the diode, the present invention adopts a diode D 3 The two ends of the RC snubber circuit are connected in parallel, and the resistor and capacitor are connected in series and then connected to the diode D 3 On the one hand, it can reduce the influence of directional recovery on the switching characteristics, and on the other hand, it can make the diode D 3 The reverse voltage spike is controlled within a safe range. The resistance value of the RC buffer circuit is 100Ω and the capacitance value is 1nF. The switching waveform after parallel connection of RC is as follows: Figure 4 As shown, in addition, it can be seen from the experimental waveform that the parallel RC does not affect the rising rate of the voltage and current of the device under test.

[0048] Different from the voltage source type double pulse test system, the roles of the active switching device and the slave device in the voltage reverse blocking type silicon carbide combination device double pulse test system cannot be interchanged, so the voltage and current waveforms of the slave device measured in the voltage reverse blocking type silicon carbide combination device double pulse test system must be electrically isolated. The current waveform flowing through the first switch tube of the present invention is obtained by measuring the coaxial shunt resistor, and the current waveform flowing through the third switch tube is obtained by a current probe with a bandwidth of 100MHz and a peak current of 50A. Figure 5 and Figure 6 The load current is 40A and the gate resistance is 20Ω. gs3 The oscillation is mainly due to the di / dt in the common source inductance L s The influence of induced voltage on the Figure 4 Medium V gs1 The reason why high-frequency oscillation occurs after the commutation is that the voltage reverse blocking type silicon carbide combination device double pulse test system switches to S 3 and D 3 After the third switch tube is formed, the differential probe is interfered. If a passive probe is used, this problem will not exist. However, in order to ensure the gate-source voltage V gs In order to ensure the consistency of the measurement, the gate-source voltage in the present invention must be measured using a differential probe.

[0049] The present invention also compares the influence of different inductor freewheeling modes on the switching characteristics of the voltage reverse blocking device. Figure 7 A double pulse test circuit similar to the inductor freewheeling mode in the voltage source type double pulse test system is designed. However, from its experimental waveform, i.e. Figure 8 It can be seen that this freewheeling mode will have a significant impact on the switching characteristics of the device under test and cannot guarantee the switching process. Figure 2 The double pulse test circuit shown works best.

[0050] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A double pulse test circuit for a silicon carbide combination device, characterized in that: Including DC power supply V dc1 With large capacitor C dc Parallel connection, used to provide a stable voltage to the device under test, full-controlled switch tube S dc Connected to large capacitor C dc With inductance L dc Between, control the DC power supply V dc1 Whether to give inductance L dc Power supply; diode D f Cathode and switch tube S dc The source is connected, the anode is connected to the DC power supply V dc1 The negative pole is connected to the inductor L dc The freewheeling path is provided; SiC MOSFET S1 is connected in series with SiC Schottky diode D1 to form a first switch tube with reverse voltage blocking function, SiC MOSFET S3 and SiC Schottky diode D3 form a third switch tube, the first switch tube and the third switch tube are connected in parallel, and the first and third switch tubes are the devices under test; capacitor C is connected between the first and third switch tubes, which is equivalent to the filter capacitor on the AC side of the current source inverter; manual switch S c With DC power supply V dc2 In series, connected to both ends of capacitor C, used to pre-charge capacitor C; manual switch S d With resistor R d Connected in series, across capacitor C, to discharge capacitor C.

2. The double pulse test circuit of silicon carbide combination device according to claim 1, characterized in that: DC power supply V dc1 The voltage value is always greater than the DC power supply V dc2 Voltage value.

3. The double pulse test circuit of silicon carbide combination device according to claim 1, characterized in that: An RC buffer circuit is connected in parallel at both ends of the diode of the third switch tube.

4. A double pulse test method for a silicon carbide assembly device, applied to a double pulse test circuit for a silicon carbide assembly device as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: The first and third switch tubes of the device under test are connected to both ends of the capacitor C, respectively providing a flow path for the inductor current. The conduction of the first switch tube is equivalent to the zero vector effect in the three-phase current source inverter, and the conduction of the third switch tube is equivalent to the active vector effect in the three-phase current source inverter. Close the manual switch S c , pre-charge the capacitor C; after the voltage of the capacitor C rises to the test value required by the test condition of the device under test, disconnect the manual switch S c ; First turn on the DC side switch tube S dc and the first switch tube, by controlling the on-time, the inductor L dc The current is increased to the test value of the test condition required by the device under test; The third switch tube is turned on in advance before the turn-off signal of MOSFET S1 in the first switch tube arrives, so that the first and third switch tubes are overlapped and turned on, which is equivalent to the switch switching characteristics of overlapping conduction in the three-phase current source inverter. The overlapping time is determined by the turn-off speed of MOSFET S1 in the first switch tube, and it is ensured that MOSFET S3 is fully turned on before MOSFET S1 is completely turned off. The inductor L dc After the current is switched from the first switch tube to the third switch tube, the first pulse stage of the double pulse test is entered; Keep the trigger signal of the third switch tube at a high level, turn on the first switch tube, and the inductor L dc The current is switched again, and the double pulse test circuit works in the zero vector state. After the first switch tube is turned off, the second pulse phase of the double pulse test is entered. The test is completed, and the switching characteristics of the device under test are determined by measuring the switching trajectory of the device under test. After the test, turn off the DC side switch tube S dc , so that the DC power supply V dc1 Stop charging the inductor, turn on the third switch tube, turn off the first switch tube, and the current will flow from the inductor L dc , the third switch tube, capacitor C, freewheeling diode D f This circuit flows through the inductor L dc All the energy on the capacitor is used to charge the capacitor C; Finally, turn off the third switch tube and manually close switch S d , releasing the energy on capacitor C.

5. The double pulse testing method for silicon carbide assembly device according to claim 4, characterized in that: Inductance L dc The sense value meets the following conditions: In the inductor L dc After charging, when the first switch tube switches to the third switch tube, the inductor L dc The current does not change.

6. The double pulse testing method for silicon carbide assembly device according to claim 4, characterized in that: The capacitance of capacitor C meets the following conditions: During the switching period, the capacitor C is equivalent to a voltage source, so that the operating conditions of the device under test during the on and off processes are the same, that is, the voltage across the device under test and the current flowing through the device remain unchanged during the on and off processes; After the double pulse test, the inductor L dc The energy will be used to charge capacitor C, which is connected to inductor L dc After the energy is released, the voltage on capacitor C remains below the rated voltage.

7. A storage medium, characterized in that: A computer executable program is stored therein, and when the computer executable program is executed by a processor, it is used to implement the double pulse testing method for a silicon carbide combination device as claimed in claim 4.

8. An electronic device, characterized in that: include: at least one memory for storing a program; At least one processor is used to load the program to execute the double pulse testing method for a silicon carbide composite device as claimed in claim 4.

9. A test device for double pulse testing of silicon carbide combination devices, characterized in that: It comprises a double pulse test circuit for a silicon carbide combination device as described in any one of claims 1 to 3.

Images