Double-pulse and short-circuit test method and device for NPC I-type three-level circuit

Abstract

The invention belongs to the field of inverter circuits, and discloses a double-pulse and short-circuit test method for an NPC I-type three-level circuit, which is used for performing double-pulse and short-circuit test on a first IGBT tube Q1 in a test circuit of the NPC I-type three-level circuit. Comprising the following steps: a first selection device is arranged between a connection point of a second IGBT tube Q2 and a third IGBT tube Q3 and a connection point of a first diode D1 and a second diode D2 in a test circuit of the NPC I type three-level circuit, and is used for selecting to carry out double pulse test, short circuit test or disconnection on the first IGBT tube Q1; when the first selection device is set to be a double-pulse test, a double-pulse signal is sent to the gate pole of the first IGBT tube Q1, a high-level signal is sent to the gate pole of the second IGBT tube Q2, and a low-level signal is sent to the gate pole of the third IGBT tube Q3 and the gate pole of the fourth IGBT tube Q4 at the same time. The method is used for avoiding too long time consumption in the test process, so that the test process can be quickly switched.

Description

Technical Field

[0001] The present application belongs to the field of inverter circuits, and specifically relates to a double pulse and short circuit test method for an NPC I type three-level circuit and a double pulse and short circuit test device for an NPC I type three-level circuit. Background Art

[0002] The NPC I type three-level circuit is a topology widely used in power converters, such as Figure 1 As shown. It has the advantages of high efficiency, low loss and the ability to achieve higher voltage and current. The structural feature of the NPC I type three-level circuit is that three levels (positive level, zero level and negative level) of output are achieved by adding clamping diodes. In the NPC I type three-level circuit, when the upper bridge arm is turned on and the lower bridge arm is disconnected, the upper output voltage is a positive voltage; when the lower bridge arm is turned on and the upper bridge arm is disconnected, the upper output voltage is a negative voltage; when both the upper and lower bridge arms are disconnected, the upper output voltage is zero. The change in direction of the current through the midpoint capacitor is controlled by the control switch. Now, in order to ensure the safe use of the NPC I type three-level circuit, a NPC I type three-level circuit test circuit is designed, as shown in Figure 2 However, since it is necessary to test the IGBT tube in both double pulse and short circuit conditions, the test equipment needs to be replaced frequently, resulting in low test efficiency and increased test costs. Summary of the invention

[0003] In order to solve the technical problems of low test efficiency and increased test cost when performing double pulse and short circuit tests on IGBT tubes, the present application provides a double pulse and short circuit test method for an NPC I type three-level circuit and a double pulse and short circuit test device for an NPC I type three-level circuit.

[0004] In a first aspect, a double pulse and short circuit test method for an NPC I type three-level circuit is provided, which is used to perform a double pulse and short circuit test on a first IGBT tube Q1 in a test circuit of the NPC I type three-level circuit, and comprises the following steps:

[0005] A first selection device S1 is provided between the connection point of the second IGBT tube Q2 and the third IGBT tube Q3 and the connection point of the first diode D1 and the second diode D2 in the test circuit of the NPC I type three-level circuit, for selecting to perform a double pulse test, a short circuit test or disconnection on the first IGBT tube Q1;

[0006] When the first selection device S1 is set to double pulse test, a double pulse signal is sent to the gate of the first IGBT tube Q1, a high level signal is sent to the gate of the second IGBT tube Q2, and a low level signal is sent to the gate of the third IGBT tube Q3 and the gate of the fourth IGBT tube Q4;

[0007] When the first selection device S1 is set to a short-circuit test, a single pulse signal is sent to the gate of the first IGBT tube Q1, a high level signal is sent to the gate of the second IGBT tube Q2, and a low level signal is sent to the gate of the third IGBT tube Q3 and the gate of the fourth IGBT tube Q4.

[0008] In a second aspect, a double pulse and short circuit test method for an NPC I type three-level circuit is provided, which is used to perform a double pulse and short circuit test on a second IGBT tube Q2 in a test circuit of the NPC I type three-level circuit, comprising the following steps:

[0009] A second selection device S2 is provided in parallel at both ends of the third IGBT tube Q3 and the fourth IGBT tube Q4 connected in sequence in the test circuit of the NPC I type three-level circuit, for selecting the second IGBT tube Q2 to be subjected to a double pulse test, a short circuit test or disconnection;

[0010] When the second selection device S2 is set to double pulse test, a double pulse signal is sent to the gate of the second IGBT tube Q2, a high level signal is sent to the gate of the third IGBT tube Q3, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the fourth IGBT tube Q4;

[0011] When the second selection device S2 is set to a short-circuit test, a single pulse signal is sent to the gate of the second IGBT tube Q2, a high level signal is sent to the gate of the third IGBT tube Q3, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the fourth IGBT tube Q4.

[0012] In a third aspect, a double pulse and short circuit test method for an NPC I type three-level circuit is provided, which is used to perform a double pulse and short circuit test on a third IGBT tube Q3 in a test circuit of the NPC I type three-level circuit, and comprises the following steps:

[0013] A third selection device S3 is provided in parallel at both ends of the first IGBT tube Q1 and the second IGBT tube Q2 connected in sequence in the test circuit of the NPC I type three-level circuit, for selecting to perform a double pulse test, a short circuit test or disconnect the third IGBT tube Q3;

[0014] When the third selection device S3 is set to double pulse test, a double pulse signal is sent to the gate of the third IGBT tube Q3, a high level signal is sent to the gate of the second IGBT tube Q2, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the fourth IGBT tube Q4;

[0015] When the third selection device S3 is set to a short-circuit test, a single pulse signal is sent to the gate of the third IGBT tube Q3, a high level signal is sent to the gate of the second IGBT tube Q2, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the fourth IGBT tube Q4.

[0016] In a fourth aspect, a double pulse and short circuit test method for an NPC I type three-level circuit is provided, which is used to perform a double pulse and short circuit test on a fourth IGBT tube Q4 in a test circuit of the NPC I type three-level circuit, and comprises the following steps:

[0017] A first selection device S1 is provided between the connection point of the second IGBT tube Q2 and the third IGBT tube Q3 and the connection point of the first diode D1 and the second diode D2 in the NPC I type three-level circuit, for selecting to perform a double pulse test, a short circuit test or disconnect the fourth IGBT tube Q4;

[0018] When the first selection device S1 is set to double pulse test, a double pulse signal is sent to the gate of the fourth IGBT tube Q4, a high level signal is sent to the gate of the third IGBT tube Q3, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the second IGBT tube Q2;

[0019] When the first selection device S1 is set to a short-circuit test, a single pulse signal is sent to the gate of the fourth IGBT tube Q4, a high level signal is sent to the gate of the third IGBT tube Q3, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the second IGBT tube Q2.

[0020] Preferably, the first selection device S1 comprises: a first converter SW1, a first inductor L1 and a first copper sheet U1; the first converter SW1 is used to connect the first inductor L1 between the connection point of the second IGBT tube Q2 and the third IGBT tube Q3 and the connection point of the first diode D1 and the second diode D2 during a double pulse test; or to connect the first copper sheet U1 between the connection point of the second IGBT tube Q2 and the third IGBT tube Q3 and the connection point of the first diode D1 and the second diode D2 during a short circuit test;

[0021] The second selection device S2 includes: a second converter SW2, a second inductor L2 and a second copper sheet U2; the second converter SW2 is used to connect the second inductor L2 in parallel to the two ends of the third IGBT tube Q3 and the fourth IGBT tube Q4 connected in sequence during a double pulse test; or to connect the second copper sheet U2 in parallel to the two ends of the third IGBT tube Q3 and the fourth IGBT tube Q4 connected in sequence during a short circuit test;

[0022] The third selection device S3 includes: a third converter SW3, a third inductor L3 and a third copper sheet U3; the third converter SW3 is used to connect the third inductor L3 in parallel to the two ends of the first IGBT tube Q1 and the second IGBT tube Q2 connected in sequence during a double pulse test; or to connect the third copper sheet U3 in parallel to the two ends of the first IGBT tube Q1 and the second IGBT tube Q2 connected in sequence during a short circuit test.

[0023] Preferably, it also includes:

[0024] The overcurrent resistor Rs is set between the connection point of the first diode D1 and the second diode D2 and the connection point of the first capacitor C1 and the second capacitor C2 in the test circuit of the NPC I type three-level circuit;

[0025] The current value flowing through the over-current resistor Rs is obtained to determine whether to disconnect the first selection device S1, the second selection device S2 or the third selection device S3 when the current value exceeds a preset threshold.

[0026] Preferably, it also includes:

[0027] The current value flowing through the overcurrent resistor Rs is obtained to determine whether the double pulse signal and / or high level signal sent to the gate of the first IGBT tube Q1, the second IGBT tube Q2, the third IGBT tube Q3 and / or the fourth IGBT tube Q4 will be changed to a low level signal when the current value exceeds a preset threshold.

[0028] In a fifth aspect, a double pulse and short circuit test device for an NPC I type three-level circuit is provided, which is used to perform a double pulse and short circuit test on a first IGBT tube Q1 or a fourth IGBT tube Q4 in a test circuit of the NPC I type three-level circuit, and includes: a first selection device S1: arranged between a connection point of a second IGBT tube Q2 and a third IGBT tube Q3 in the test circuit of the NPC I type three-level circuit and a connection point of a first diode D1 and a second diode D2; and used to select the first IGBT tube Q1 or the fourth IGBT tube Q4 to perform a double pulse test, a short circuit test, or disconnect the connection;

[0029] Overcurrent resistor Rs: arranged between the connection point of the first diode D1 and the second diode D2 and the connection point of the first capacitor C1 and the second capacitor C2 in the test circuit of the NPC I type three-level circuit; used to obtain the current flowing through the first IGBT tube Q1 and the second IGBT tube Q2, and the first inductor L1 or the first copper sheet U1 during the test; or used to obtain the current flowing through the third IGBT tube Q3 and the fourth IGBT tube Q4, and the first inductor L1 or the first copper sheet U1 during the test.

[0030] In a sixth aspect, a double pulse and short circuit test device for an NPC I type three-level circuit is provided, which is used to perform a double pulse and short circuit test on a second IGBT tube Q1 in a test circuit of the NPC I type three-level circuit, comprising:

[0031] The second selection device S2 is arranged in parallel at both ends of the third IGBT tube Q3 and the fourth IGBT tube Q4 which are connected in sequence; it is used to select the second IGBT tube Q2 to be subjected to a double pulse test, a short circuit test or disconnection;

[0032] Overcurrent resistor Rs: set between the connection point of the first diode D1 and the second diode D2 and the connection point of the first capacitor C1 and the second capacitor C2 in the test circuit of the NPC I type three-level circuit; used to obtain the current flowing through the first diode D1, the second IGBT tube Q2, and the third inductor L3 during the test.

[0033] In a seventh aspect, a double pulse and short circuit test device for an NPC I type three-level circuit is provided, which is used to perform a double pulse and short circuit test on a third IGBT tube Q3 in a test circuit of the NPC I type three-level circuit, comprising:

[0034] A third selection device S3 is arranged in parallel at both ends of the first IGBT tube Q1 and the second IGBT tube Q2 which are connected in sequence; and is used to select a double pulse test, a short circuit test or a disconnection of the third IGBT tube Q2;

[0035] Overcurrent resistor Rs: set between the connection point of the first diode D1 and the second diode D2 and the connection point of the first capacitor C1 and the second capacitor C2 in the test circuit of the NPC I type three-level circuit; used to obtain the current flowing through the second diode D2, the third IGBT tube Q3, and the second inductor L2 during the test.

[0036] In summary, the present application includes at least one of the following beneficial technical effects:

[0037] 1. By using the first selection device S1, the second selection device S2 or the third selection device S3, it is possible to quickly switch between the double pulse test and the short circuit test of the IGBT tube, thereby avoiding the technical problems of excessively high test cost and low test efficiency; 2. By increasing the overcurrent resistance Rs, when the double pulse test or the short circuit test of the IGBT tube is performed, if the current is too large, the test can be quickly terminated to avoid the IGBT tube being burned. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the NPC I type three-level circuit diagram;

[0039] Figure 2 This is the NPC I type three-level circuit test circuit diagram;

[0040] Figure 3 This is the gate signal waveform of each IGBT tube during the double pulse test of the NPC I type three-level circuit;

[0041] Figure 4 This is the gate signal waveform of each IGBT tube during the short-circuit test of the NPC I type three-level circuit;

[0042] Figure 5 is a diagram of a first embodiment of a test circuit for an NPC I type three-level circuit;

[0043] Figure 6 is a diagram of a second embodiment of a test circuit for an NPC I type three-level circuit;

[0044] Figure 7 is a diagram of a third embodiment of a test circuit for an NPC I type three-level circuit;

[0045] Figure 8 is a diagram of a fourth embodiment of a test circuit for an NPC I type three-level circuit;

[0046] Fig. 9 is a diagram of a fifth embodiment of a test circuit for an NPC I type three-level circuit;

[0047] Fig.10 is a sixth embodiment diagram of a test circuit for an NPC I type three-level circuit;

[0048] Fig.11 This is a current flow diagram when the test circuit of the NPC I type three-level circuit tests the first IGBT tube Q1 with double pulses;

[0049] Fig.12 This is a current flow diagram when the test circuit of the NPC I type three-level circuit tests the short circuit of the first IGBT tube Q1;

[0050] Fig.13 This is the current flow diagram when the test circuit of the NPC I type three-level circuit tests the fourth IGBT tube Q4 with double pulses;

[0051] Fig.14 This is a current flow diagram when the test circuit of the NPC I type three-level circuit is testing the short circuit of the fourth IGBT tube Q4;

[0052] Fig.15 This is the current flow diagram when the test circuit of the NPC I type three-level circuit tests the second IGBT tube Q2 with double pulses;

[0053] Fig.16 This is a current flow diagram when the test circuit of the NPC I type three-level circuit is testing the short circuit of the second IGBT tube Q2;

[0054] Fig.17 This is the current flow diagram when the test circuit of the NPC I type three-level circuit tests the third IGBT tube Q3 with double pulses;

[0055] Fig.18 This is the current flow diagram when the test circuit of the NPC I type three-level circuit tests the third IGBT tube Q3 for short circuit;

[0056] Fig.19 is a seventh embodiment diagram of a test circuit for an NPC I type three-level circuit;

[0057] Fig. 20 is a diagram of an eighth embodiment of a test circuit for an NPC I type three-level circuit;

[0058] Fig.21 is a ninth embodiment diagram of a test circuit for an NPC I type three-level circuit;

[0059] Fig. 22 FIG. 1 is a diagram of a tenth embodiment of a test circuit for an NPC I type three-level circuit. DETAILED DESCRIPTION

[0060] Terminology explanation:

[0061] NPC I type three-level circuit: NPC I type (Neutral Point Clamped), that is, neutral point clamped circuit. It is also called neutral-point-clamped inverter.

[0062] The present application provides a double pulse and short circuit test method for an NPC I type three-level circuit and a double pulse and short circuit test device for an NPC I type three-level circuit.

[0063] First, as Figure 3 , Figure 4 , Figure 5 As shown, a double pulse and short circuit test method for an NPC I type three-level circuit is provided, which is used to perform a double pulse and short circuit test on a first IGBT tube Q1 in a test circuit of the NPC I type three-level circuit, and includes the following steps:

[0064] A first selection device S1 is provided between a connection point of a second IGBT tube Q2 and a third IGBT tube Q3 and a connection point of a first diode D1 and a second diode D2 in a test circuit of an NPC I type three-level circuit, for selecting to perform a double pulse test, a short circuit test or disconnection on the first IGBT tube Q1; the first selection device S1 can be implemented in a variety of ways, for example, by an active device or a switch circuit; both active devices and switch circuits can be controlled by a control circuit, so that the first selection device S1 is in an on, short circuit or disconnected state, thereby achieving a state of performing a pulse test, a short circuit test or a disconnection on the first IGBT tube Q1.

[0065] When the first selection device S1 is set to double pulse test, a double pulse signal is sent to the gate of the first IGBT tube Q1, a high level signal is sent to the gate of the second IGBT tube Q2, and a low level signal is sent to the gate of the third IGBT tube Q3 and the gate of the fourth IGBT tube Q4. When the double pulse test is in progress, the first selection device S1 is in the on state, and the gate of the second IGBT tube Q2 receives a high level signal, indicating that the second IGBT tube Q2 is in the on state, and current can flow through. At this time, the gates of the third IGBT tube Q3 and the fourth IGBT tube Q4 are in the on state. If the gate of the fourth IGBT tube Q4 receives a low-level signal, it means that the third IGBT tube Q3 and the fourth IGBT tube Q4 are in the off state and current cannot flow through; at the same time, a double pulse signal is sent to the first IGBT tube Q1, that is, a double pulse test is performed on the first IGBT tube Q1; under the double pulse test state, the ability of the first IGBT tube Q1 to withstand large currents will be tested; the level, duration, and interval between the double pulses are all determined by the specific parameters of the first IGBT tube Q1, which belongs to the existing technology and will not be elaborated here.

[0066] When the first selection device S1 is set to a short-circuit test, a single pulse signal is sent to the gate of the first IGBT tube Q1, a high level signal is sent to the gate of the second IGBT tube Q2, and a low level signal is sent to the gate of the third IGBT tube Q3 and the gate of the fourth IGBT tube Q4. When in the short-circuit test, the first selection device S1 is in a short-circuit state, and the gate of the second IGBT tube Q2 receives a high-level signal, which means that the second IGBT tube Q2 is in the on state and current can flow through. At this time, the gate of the third IGBT tube Q3 and the gate of the fourth IGBT tube Q4 receive a low-level signal, which means that the third IGBT tube Q3 and the fourth IGBT tube Q4 are in the off state and current cannot flow through. At the same time, a single pulse waveform is sent to the first IGBT tube Q1, that is, a short-circuit test is performed on the first IGBT tube Q1. In the short-circuit test state, the first IGBT tube Q1 will be tested for its ability to withstand large currents in the short-circuit state. The level and duration of the single pulse are determined by the specific parameters of the first IGBT tube Q1, which belongs to the prior art and will not be repeated here.

[0067] Obviously, in this embodiment, a first selection device S1 that is easy to control is added, so that the test circuit of the entire NPC I type three-level circuit is easy to control, and there is no need to replace components and equipment every time the double pulse test or short-circuit test is switched, thereby reducing the time cost and equipment cost of the test, which is conducive to the industrialization of the test work and improves the efficiency of the test work.

[0068] Second, as Figure 3 , Figure 4 , Figure 6 As shown, a double pulse and short circuit test method for an NPC I type three-level circuit is provided, which is used to perform a double pulse and short circuit test on a second IGBT tube Q2 in a test circuit of the NPC I type three-level circuit, and includes the following steps:

[0069] A second selection device S2 is arranged in parallel at both ends of the third IGBT tube Q3 and the fourth IGBT tube Q4 connected sequentially in the test circuit of the NPC I type three-level circuit, for selecting the second IGBT tube Q2 to be subjected to a double pulse test, a short circuit test or a disconnection; the second selection device S2 can be implemented in a variety of ways, for example, by an active device or a switch circuit; both active devices and switch circuits can be controlled by a control circuit, so that the second selection device S2 is in an on, short circuit or disconnected state, so as to achieve a state of pulse testing, short circuit testing or disconnection of the second IGBT tube Q2.

[0070] When the second selection device S2 is set to double pulse test, a double pulse signal is sent to the gate of the second IGBT tube Q2, a high level signal is sent to the gate of the third IGBT tube Q3, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the fourth IGBT tube Q4. When the second selection device S2 is in the double pulse test, the second selection device S2 is in the on state, and the gate of the third IGBT tube Q3 receives a high level signal, which means that the third IGBT tube Q3 is in the on state, and current can flow through. At this time, the gates of the first IGBT tube Q1 and Q4 are If the gate of the fourth IGBT tube Q4 receives a low-level signal, it means that the first IGBT tube Q1 and the fourth IGBT tube Q4 are in the off state and current cannot flow through; at the same time, a double pulse signal is sent to the second IGBT tube Q2, that is, a double pulse test is performed on the second IGBT tube Q2; under the double pulse test state, the ability of the second IGBT tube Q2 to withstand large currents will be tested; the level, duration, and interval between the double pulses are all determined by the specific parameters of the second IGBT tube Q2, which belongs to the existing technology and will not be elaborated here.

[0071] When the second selection device S2 is set to a short-circuit test, a single pulse signal is sent to the gate of the second IGBT tube Q2, a high level signal is sent to the gate of the third IGBT tube Q3, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the fourth IGBT tube Q4. When in the short-circuit test, the second selection device S2 is in a short-circuit state, and the gate of the third IGBT tube Q3 receives a high-level signal, which means that the third IGBT tube Q3 is in the on state and current can flow through. At this time, the gate of the first IGBT tube Q1 and the gate of the fourth IGBT tube Q4 receive a low-level signal, which means that the first IGBT tube Q1 and the fourth IGBT tube Q4 are in the off state and current cannot flow through. At the same time, a single pulse waveform is sent to the second IGBT tube Q2, that is, a short-circuit test is performed on the second IGBT tube Q2. In the short-circuit test state, the second IGBT tube Q2 will be tested for its ability to withstand large currents in the short-circuit state. The level and duration of the single pulse are determined by the specific parameters of the second IGBT tube Q2, which belongs to the prior art and will not be repeated here.

[0072] Obviously, in this embodiment, a second selection device S2 that is easy to control is added, so that the test circuit of the entire NPC I type three-level circuit is easy to control, and there is no need to replace components and equipment every time the double pulse test or short-circuit test is switched, thereby reducing the time cost and equipment cost of the test, which is conducive to the industrialization of the test work and improves the efficiency of the test work.

[0073] Thirdly, Figure 3 , Figure 4 , Figure 7As shown, a double pulse and short circuit test method for an NPC I type three-level circuit is provided, which is used to perform a double pulse and short circuit test on a third IGBT tube Q3 in a test circuit of the NPC I type three-level circuit, and includes the following steps:

[0074] A third selection device S3 is arranged in parallel at both ends of the first IGBT tube Q1 and the second IGBT tube Q2 which are connected in sequence in the test circuit of the NPC I type three-level circuit, and is used to select the third IGBT tube Q3 to be subjected to a double pulse test, a short circuit test or disconnection; the third selection device S3 can be implemented in a variety of ways, for example, by an active device or a switch circuit; whether it is an active device or a switch circuit, it can be controlled by a control circuit, so that the second selection device S2 is in a conducting, short circuit or disconnected state, so as to achieve a state of pulse testing, short circuit testing or disconnection of the third IGBT tube Q3.

[0075] When the third selection device S3 is set to double pulse test, a double pulse signal is sent to the gate of the third IGBT tube Q3, a high level signal is sent to the gate of the second IGBT tube Q2, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the fourth IGBT tube Q4. When the third selection device S3 is in the on state, the gate of the second IGBT tube Q2 receives a high level signal, indicating that the second IGBT tube Q2 is in the on state, and current can flow through. At this time, the gates of the first IGBT tube Q1 and the fourth IGBT tube Q4 are in the on state. If the gate of the fourth IGBT tube Q4 receives a low-level signal, it means that the first IGBT tube Q1 and the fourth IGBT tube Q4 are in the off state and current cannot flow through; at the same time, a double pulse signal is sent to the third IGBT tube Q3, that is, a double pulse test is performed on the third IGBT tube Q3; under the double pulse test state, the ability of the third IGBT tube Q3 to withstand large current will be tested; the level, duration, and double pulse interval of the double pulse are all determined by the specific parameters of the third IGBT tube Q3, which belongs to the existing technology and will not be repeated here.

[0076] When the third selection device S3 is set to a short-circuit test, a single pulse signal is sent to the gate of the third IGBT tube Q3, a high level signal is sent to the gate of the second IGBT tube Q2, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the fourth IGBT tube Q4. When in the short-circuit test, the third selection device S3 is in a short-circuit state, and the gate of the second IGBT tube Q2 receives a high-level signal, indicating that the second IGBT tube Q2 is in the on state and current can flow through. At this time, the gate of the first IGBT tube Q1 and the gate of the fourth IGBT tube Q4 receive a low-level signal, indicating that the first IGBT tube Q1 and the fourth IGBT tube Q4 are in the off state and current cannot flow through. At the same time, a single pulse waveform is sent to the third IGBT tube Q3, that is, a short-circuit test is performed on the second IGBT tube Q2. In the short-circuit test state, the third IGBT tube Q3 will be tested for its ability to withstand large currents in the short-circuit state. The level and duration of the single pulse are determined by the specific parameters of the third IGBT tube Q3, which belongs to the prior art and will not be repeated here.

[0077] Obviously, in this embodiment, a third selection device S3 that is easy to control is added, so that the test circuit of the entire NPC I type three-level circuit is easy to control, and there is no need to replace components and equipment every time the double pulse test or short-circuit test is switched, thereby reducing the time cost and equipment cost of the test, which is conducive to the industrialization of the test work and improves the efficiency of the test work.

[0078] Fourthly, Figure 3 , Figure 4 , Figure 5 As shown, a double pulse and short circuit test method for an NPC I type three-level circuit is provided, which is used to perform a double pulse and short circuit test on a fourth IGBT tube Q4 in a test circuit of the NPC I type three-level circuit, and includes the following steps:

[0079] A first selection device S1 is provided between the connection point of the second IGBT tube Q2 and the third IGBT tube Q3 and the connection point of the first diode D1 and the second diode D2 in the NPC I type three-level circuit, for selecting to perform a double pulse test, a short circuit test or disconnection on the fourth IGBT tube Q4; the first selection device S1 can be implemented in a variety of ways, for example, by an active device or a switch circuit; whether it is an active device or a switch circuit, it can be controlled by a control circuit so that the first selection device S1 is in an on, short circuit or disconnected state, so as to achieve a state of performing a pulse test, a short circuit test or a disconnection on the fourth IGBT tube Q4.

[0080] When the first selection device S1 is set to double pulse test, a double pulse signal is sent to the gate of the fourth IGBT tube Q4, a high level signal is sent to the gate of the third IGBT tube Q3, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the second IGBT tube Q2. When the double pulse test is in progress, the first selection device S1 is in the on state, and the gate of the third IGBT tube Q3 receives a high level signal, indicating that the third IGBT tube Q3 is in the on state, and current can flow through. At this time, the gates of the first IGBT tube Q1 and Q2 are in the on state. If the gate of the second IGBT tube Q2 receives a low-level signal, it means that the first IGBT tube Q1 and the second IGBT tube Q2 are in the off state and current cannot flow through; at the same time, a double pulse signal is sent to the fourth IGBT tube Q4, that is, a double pulse test is performed on the fourth IGBT tube Q4; under the double pulse test state, the ability of the fourth IGBT tube Q4 to withstand large currents will be tested; the level, duration, and interval between the double pulses are all determined by the specific parameters of the fourth IGBT tube Q4, which belongs to the existing technology and will not be elaborated here.

[0081] When the first selection device S1 is set to a short-circuit test, a single pulse signal is sent to the gate of the fourth IGBT tube Q4, a high level signal is sent to the gate of the third IGBT tube Q3, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the second IGBT tube Q2. When in the short-circuit test, the first selection device S1 is in a short-circuit state, and the gate of the third IGBT tube Q3 receives a high-level signal, which means that the third IGBT tube Q3 is in the on state and current can flow through. At this time, the gate of the first IGBT tube Q1 and the gate of the second IGBT tube Q2 receive a low-level signal, which means that the first IGBT tube Q1 and the second IGBT tube Q2 are in the off state and current cannot flow through. At the same time, a single pulse waveform is sent to the fourth IGBT tube Q4, that is, a short-circuit test is performed on the fourth IGBT tube Q4. In the short-circuit test state, the fourth IGBT tube Q4 will be tested for its ability to withstand large currents in the short-circuit state. The level and duration of the single pulse are determined by the specific parameters of the fourth IGBT tube Q4, which belongs to the prior art and will not be repeated here.

[0082] Obviously, in this embodiment, a first selection device S1 that is easy to control is added, so that the test circuit of the entire NPC I type three-level circuit is easy to control, and there is no need to replace components and equipment every time the double pulse test or short-circuit test is switched, thereby reducing the time cost and equipment cost of the test, which is conducive to the industrialization of the test work and improves the efficiency of the test work.

[0083] Preferably, Figure 8As shown, the first selection device S1 includes: a first converter SW1, a first inductor L1 and a first copper sheet U1; the first converter SW1 is used to connect the first inductor L1 between the connection point of the second IGBT tube Q2 and the third IGBT tube Q3 and the connection point of the first diode D1 and the second diode D2 during the double pulse test; or to connect the first copper sheet U1 between the connection point of the second IGBT tube Q2 and the third IGBT tube Q3 and the connection point of the first diode D1 and the second diode D2 during the short circuit test; in the present application, the first selection device S1 can be used to perform double pulse test and short circuit test on the first IGBT tube Q1 or the fourth IGBT tube Q4 respectively.

[0084] When the double pulse test is performed on the first IGBT tube Q1, the first converter SW1 in the first selection device S1 selects to connect the first inductor L1; and sends a double pulse waveform signal to the first IGBT tube Q1, sends a high level signal to the second IGBT tube Q2, and sends a low level signal to the third IGBT tube Q3 and the fourth IGBT tube Q4. Under the above conditions, the current flow direction obtained is as follows: Fig.11 As shown, when the first IGBT tube Q1 receives the first high level in the double pulse, the current starts from the positive pole, passes through the first IGBT tube Q1, the second IGBT tube Q2, the first inductor L1, and finally flows to the N pole; when the first IGBT tube Q1 receives the low level in the double pulse, the current is discharged from the first inductor L1, passes through the first diode D1, the second IGBT tube Q2 in sequence, and then returns to the first inductor L1, forming a loop to consume the remaining energy; then, when the first IGBT tube Q1 receives the second high level signal in the double pulse, the action of the first high level signal is repeated, and then the double pulse test of the first IGBT tube Q1 is completed, and the test data is fed back to the oscilloscope or terminal display through the circuit board. When the first IGBT tube Q1 is short-circuited, the first converter SW1 in the first selection device S1 selects to connect the first copper sheet U1; and sends a single pulse waveform signal to the first IGBT tube Q1, a high level signal to the second IGBT tube Q2, and a low level signal to the third IGBT tube Q3 and the fourth IGBT tube Q4. Under the above conditions, the current flow direction is obtained, such as Fig.12 As shown, when the first IGBT tube Q1 receives a high level signal, the current starts from the positive electrode, passes through the first IGBT tube Q1, the second IGBT tube Q2, and the first copper sheet U1. Then the short circuit test of the first IGBT tube Q1 is completed, and the test data is fed back to the oscilloscope or terminal display through the circuit board.

[0085] When the fourth IGBT tube Q4 is subjected to a double pulse test, the first converter SW1 in the first selection device S1 selects to connect the first inductor L1; and sends a double pulse waveform signal to the fourth IGBT tube Q4, sends a high level signal to the third IGBT tube Q3, and sends a low level signal to the first IGBT tube Q1 and the second IGBT tube Q2. Under the above conditions, the current flow direction obtained is as follows: Fig.13 As shown, when the fourth IGBT tube Q4 receives the first high level in the double pulse, the current starts from the N pole, passes through the first inductor L1, the third IGBT tube Q3, the fourth IGBT tube Q4, and finally flows to the negative pole; when the fourth IGBT tube Q4 receives the low level in the double pulse, the current is discharged from the first inductor L1, passes through the third inductor Q3 and the second diode D2 in sequence, and then returns to the first inductor L1 to form a loop, and the remaining energy is consumed; then, when the fourth IGBT tube Q4 receives the second high level signal in the double pulse, the action of the first high level signal is repeated, and then the double pulse test of the fourth IGBT tube Q4 is completed, and the test data is fed back to the oscilloscope or terminal display through the circuit board.

[0086] When the fourth IGBT tube Q4 is short-circuited, the first converter SW1 in the first selection device S1 selects to connect the first copper sheet U1; and sends a single pulse waveform signal to the fourth IGBT tube Q1, a high level signal to the third IGBT tube Q3, and a low level signal to the first IGBT tube Q1 and the second IGBT tube Q2. Under the above conditions, the current flow direction is obtained, such as Fig.14 As shown, when the fourth IGBT tube Q4 receives a high level signal, the current starts from the N pole, passes through the first copper sheet U1, the third IGBT tube Q3, the fourth IGBT tube Q4, and finally flows to the N pole. After that, the short circuit test of the fourth IGBT tube Q4 is completed, and the test data is fed back to the oscilloscope or terminal display through the circuit board.

[0087] like Fig. 9 As shown, the second selection device S2 includes: a second converter SW2, a second inductor L2 and a second copper sheet U2; the second converter SW2 is used to connect the second inductor L2 in parallel to the two ends of the third IGBT tube Q3 and the fourth IGBT tube Q4 connected in sequence during the double pulse test; or to connect the second copper sheet U2 in parallel to the two ends of the third IGBT tube Q3 and the fourth IGBT tube Q4 connected in sequence during the short circuit test; in the present application, the second selection device S2 can be used to perform double pulse test and short circuit test on the second IGBT tube Q2 respectively.

[0088] When the second IGBT tube Q2 is subjected to a double pulse test, the second converter SW2 in the second selection device S2 selects to connect the second inductor L2; and sends a double pulse waveform signal to the second IGBT tube Q2, sends a high level signal to the third IGBT tube Q3, and sends a low level signal to the first IGBT tube Q1 and the fourth IGBT tube Q4. Under the above conditions, the current flow direction obtained is as follows: Fig.15 As shown, when the second IGBT tube Q2 receives the first high level in the double pulse, the current starts from the N pole, passes through the first diode D1, the second IGBT tube Q2, the second inductor L2, and finally flows to the negative pole; when the second IGBT tube Q2 receives a low level signal, the current is discharged from the second inductor L2, passes through the fourth IGBT tube Q4 and the third IGBT tube Q3 in sequence, and then returns to the second inductor L2 to form a loop, and the remaining energy is consumed; then, when the second IGBT tube Q2 receives the second high level signal in the double pulse, the action of the first high level signal is repeated, and then the double pulse test of the second IGBT tube Q2 is completed, and the test data is fed back to the oscilloscope or terminal display through the circuit board.

[0089] When the second IGBT tube Q2 is short-circuited, the second converter SW2 in the second selection device S2 selects to connect the second copper sheet U2; and sends a single pulse waveform signal to the second IGBT tube Q2, a high level signal to the third IGBT tube Q3, and a low level signal to the first IGBT tube Q1 and the fourth IGBT tube Q4. Under the above conditions, the current flow direction is obtained, such as Fig.15 As shown, when the second IGBT tube Q2 receives a high level signal, the current starts from the N pole, passes through the first diode D1, the second IGBT tube Q2, the second copper sheet U2, and finally flows to the cathode. After that, the short circuit test of the second IGBT tube Q2 is completed, and the test data is fed back to the oscilloscope or terminal display through the circuit board.

[0090] like Fig.10 As shown, the third selection device S3 includes: a third converter SW3, a third inductor L3 and a third copper sheet U3; the third converter SW3 is used to connect the third inductor L3 in parallel to the two ends of the first IGBT tube Q1 and the second IGBT tube Q2 connected in sequence during the double pulse test; or to connect the third copper sheet U3 in parallel to the two ends of the first IGBT tube Q1 and the second IGBT tube Q2 connected in sequence during the short circuit test. In the present application, the third selection device S3 can be used to perform double pulse test and short circuit test on the third IGBT tube Q3 respectively.

[0091] When the double pulse test is performed on the third IGBT tube Q3, the third converter SW3 in the third selection device S3 selects to connect the third inductor L3; and sends a double pulse waveform signal to the third IGBT tube Q3, sends a high level signal to the second IGBT tube Q2, and sends a low level signal to the first IGBT tube Q1 and the fourth IGBT tube Q4. Under the above conditions, the current flow direction obtained is as follows: Fig.17 As shown, when the third IGBT tube Q3 receives a high-level signal, the current starts from the positive electrode, passes through the third inductor L3, the third IGBT tube Q3, the second diode D2, and finally flows to the N pole; when the third IGBT tube Q3 receives a low-level signal, the current is discharged from the third inductor L3, passes through the second IGBT tube Q2, the first IGBT tube Q1 in sequence, and then returns to the third inductor L3 to form a loop, and the remaining energy is consumed; then, when the third IGBT tube Q3 receives the second high-level signal in the double pulse, the action of the first high-level signal is repeated, and then the double pulse test of the third IGBT tube Q3 is completed, and the test data is fed back to the oscilloscope or terminal display through the circuit board.

[0092] When the third IGBT tube Q3 is short-circuited, the third converter SW3 in the third selection device S3 selects to connect the third copper sheet U3; and sends a single pulse waveform signal to the third IGBT tube Q3, a high level signal to the second IGBT tube Q2, and a low level signal to the first IGBT tube Q1 and the fourth IGBT tube Q4. Under the above conditions, the current flow direction is obtained, such as Fig.18 As shown, when the third IGBT tube Q3 receives a high level signal, the current starts from the positive electrode, passes through the third copper sheet U3, the third IGBT tube Q3, the second diode D2, and finally flows to the N pole. After that, the short circuit test of the third IGBT tube Q3 is completed, and the test data is fed back to the oscilloscope or terminal display through the circuit board.

[0093] Preferably, Fig.19 As shown, it also includes:

[0094] The overcurrent resistor Rs is set between the connection point of the first diode D1 and the second diode D2 and the connection point of the first capacitor C1 and the second capacitor C2 in the test circuit of the NPC I type three-level circuit;

[0095] The current value flowing through the over-current resistor Rs is obtained to determine whether to disconnect the first selection device S1, the second selection device S2 or the third selection device S3 when the current value exceeds a preset threshold.

[0096] Preferably, it also includes:

[0097] The current value flowing through the overcurrent resistor Rs is obtained to determine whether the double pulse signal and / or high level signal sent to the gate of the first IGBT tube Q1, the second IGBT tube Q2, the third IGBT tube Q3 and / or the fourth IGBT tube Q4 will be changed to a low level signal when the current value exceeds a preset threshold.

[0098] Fifthly, Fig. 20 As shown, a double pulse and short circuit test device for an NPC I type three-level circuit is provided, which is used to perform a double pulse and short circuit test on a first IGBT tube Q1 or a fourth IGBT tube Q4 in a test circuit of the NPC I type three-level circuit, and includes:

[0099] The first selection device S1 is arranged between the connection point of the second IGBT tube Q2 and the third IGBT tube Q3 and the connection point of the first diode D1 and the second diode D2 in the test circuit of the NPC I type three-level circuit; it is used to select the first IGBT tube Q1 or the fourth IGBT tube Q4 to perform a double pulse test, a short circuit test or disconnection;

[0100] Overcurrent resistor Rs: arranged between the connection point of the first diode D1 and the second diode D2 and the connection point of the first capacitor C1 and the second capacitor C2 in the test circuit of the NPC I type three-level circuit; used to obtain the current flowing through the first IGBT tube Q1 and the second IGBT tube Q2, and the first inductor L1 or the first copper sheet U1 during the test; or used to obtain the current flowing through the third IGBT tube Q3 and the fourth IGBT tube Q4, and the first inductor L1 or the first copper sheet U1 during the test.

[0101] Sixth, such as Fig.21 As shown, a double pulse and short circuit test device for an NPC I type three-level circuit is provided, which is used to perform a double pulse and short circuit test on a second IGBT tube Q1 in a test circuit of the NPC I type three-level circuit, comprising:

[0102] The second selection device S2 is arranged in parallel at both ends of the third IGBT tube Q3 and the fourth IGBT tube Q4 which are connected in sequence; it is used to select the second IGBT tube Q2 to be subjected to a double pulse test, a short circuit test or disconnection;

[0103] Overcurrent resistor Rs: set between the connection point of the first diode D1 and the second diode D2 and the connection point of the first capacitor C1 and the second capacitor C2 in the test circuit of the NPC I type three-level circuit; used to obtain the current flowing through the first diode D1, the second IGBT tube Q2, and the third inductor L3 during the test.

[0104] Seventh, such as Fig. 22As shown, a double pulse and short circuit test device for an NPC I type three-level circuit is provided, which is used to perform a double pulse and short circuit test on a third IGBT tube Q3 in a test circuit of the NPC I type three-level circuit, comprising:

[0105] A third selection device S3 is arranged in parallel at both ends of the first IGBT tube Q1 and the second IGBT tube Q2 which are connected in sequence; and is used to select a double pulse test, a short circuit test or a disconnection of the third IGBT tube Q2;

[0106] Overcurrent resistor Rs: set between the connection point of the first diode D1 and the second diode D2 and the connection point of the first capacitor C1 and the second capacitor C2 in the test circuit of the NPC I type three-level circuit; used to obtain the current flowing through the second diode D2, the third IGBT tube Q3, and the second inductor L2 during the test.

[0107] In summary, the present application includes at least one of the following beneficial technical effects:

[0108] 1. By using the first selection device S1, the second selection device S2 or the third selection device S3, it is possible to quickly switch between the double pulse test and the short circuit test of the IGBT tube, thereby avoiding the technical problems of excessively high test cost and low test efficiency; 2. By increasing the overcurrent resistance Rs, when the double pulse test or the short circuit test of the IGBT tube is performed, if the current is too large, the test can be quickly terminated to avoid the IGBT tube being burned.

[0109] The prior art performs double pulse testing and short circuit testing separately, which means that two devices with different working logics need to be used, increasing the equipment cost; and when the tester needs to test the short circuit after testing the double pulse, the original circuit needs to be modified, and the test can be continued only after the modification, which increases the time cost of the tester; the present invention only needs to use one device and does not need to modify the circuit, saving equipment cost and time cost.

[0110] The above are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Any feature disclosed in this specification (including the abstract and drawings), unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

Claims

1. A double pulse and short circuit test method for an NPC I type three-level circuit, used to perform a double pulse and short circuit test on a first IGBT tube Q1 in a test circuit of an NPC I type three-level circuit, characterized in that: The steps include: A first selection device S1 is provided between the connection point of the second IGBT tube Q2 and the third IGBT tube Q3 and the connection point of the first diode D1 and the second diode D2 in the test circuit of the NPCI type three-level circuit, for selecting to perform a double pulse test, a short circuit test or disconnection on the first IGBT tube Q1; When the first selection device S1 is set to double pulse test, a double pulse signal is sent to the gate of the first IGBT tube Q1, a high level signal is sent to the gate of the second IGBT tube Q2, and a low level signal is sent to the gate of the third IGBT tube Q3 and the gate of the fourth IGBT tube Q4; When the first selection device S1 is set to a short-circuit test, a single pulse signal is sent to the gate of the first IGBT tube Q1, a high level signal is sent to the gate of the second IGBT tube Q2, and a low level signal is sent to the gate of the third IGBT tube Q3 and the gate of the fourth IGBT tube Q4.

2. A double pulse and short circuit test method for an NPC I type three-level circuit, used to perform a double pulse and short circuit test on a second IGBT tube Q2 in a test circuit of the NPC I type three-level circuit, characterized in that: The steps include: A second selection device S2 is provided in parallel at both ends of the third IGBT tube Q3 and the fourth IGBT tube Q4 connected in sequence in the test circuit of the NPCI type three-level circuit, for selecting the second IGBT tube Q2 to be subjected to a double pulse test, a short circuit test or disconnection; When the second selection device S2 is set to double pulse test, a double pulse signal is sent to the gate of the second IGBT tube Q2, a high level signal is sent to the gate of the third IGBT tube Q3, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the fourth IGBT tube Q4; When the second selection device S2 is set to a short-circuit test, a single pulse signal is sent to the gate of the second IGBT tube Q2, a high level signal is sent to the gate of the third IGBT tube Q3, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the fourth IGBT tube Q4.

3. A double pulse and short circuit test method for an NPC I type three-level circuit, used to perform a double pulse and short circuit test on a third IGBT tube Q3 in a test circuit of the NPC I type three-level circuit, characterized in that: The steps include: A third selection device S3 is provided in parallel at both ends of the first IGBT tube Q1 and the second IGBT tube Q2 connected in sequence in the test circuit of the NPCI type three-level circuit, for selecting to perform a double pulse test, a short circuit test or disconnect the third IGBT tube Q3; When the third selection device S3 is set to double pulse test, a double pulse signal is sent to the gate of the third IGBT tube Q3, a high level signal is sent to the gate of the second IGBT tube Q2, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the fourth IGBT tube Q4; When the third selection device S3 is set to a short-circuit test, a single pulse signal is sent to the gate of the third IGBT tube Q3, a high level signal is sent to the gate of the second IGBT tube Q2, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the fourth IGBT tube Q4.

4. A double pulse and short circuit test method for an NPC I type three-level circuit, used to perform a double pulse and short circuit test on a fourth IGBT tube Q4 in a test circuit of the NPC I type three-level circuit, characterized in that: The steps include: A first selection device S1 is provided between the connection point of the second IGBT tube Q2 and the third IGBT tube Q3 and the connection point of the first diode D1 and the second diode D2 in the NPCI type three-level circuit, for selecting to perform a double pulse test, a short circuit test or disconnect the fourth IGBT tube Q4; When the first selection device S1 is set to double pulse test, a double pulse signal is sent to the gate of the fourth IGBT tube Q4, a high level signal is sent to the gate of the third IGBT tube Q3, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the second IGBT tube Q2; When the first selection device S1 is set to a short-circuit test, a single pulse signal is sent to the gate of the fourth IGBT tube Q4, a high level signal is sent to the gate of the third IGBT tube Q3, and a low level signal is sent to the gate of the first IGBT tube Q1 and the gate of the second IGBT tube Q2.

5. A double pulse and short circuit test method for an NPC I type three-level circuit according to any one of claims 1 to 4, characterized in that: The first selection device S1 includes: a first converter SW1, a first inductor L1 and a first copper sheet U1; the first converter SW1 is used to connect the first inductor L1 between the connection point of the second IGBT tube Q2 and the third IGBT tube Q3 and the connection point of the first diode D1 and the second diode D2 during a double pulse test; or to connect the first copper sheet U1 between the connection point of the second IGBT tube Q2 and the third IGBT tube Q3 and the connection point of the first diode D1 and the second diode D2 during a short circuit test; The second selection device S2 includes: a second converter SW2, a second inductor L2 and a second copper sheet U2; the second converter SW2 is used to connect the second inductor L2 in parallel to the two ends of the third IGBT tube Q3 and the fourth IGBT tube Q4 connected in sequence during a double pulse test; or to connect the second copper sheet U2 in parallel to the two ends of the third IGBT tube Q3 and the fourth IGBT tube Q4 connected in sequence during a short circuit test; The third selection device S3 includes: a third converter SW3, a third inductor L3 and a third copper sheet U3; the third converter SW3 is used to connect the third inductor L3 in parallel to the two ends of the first IGBT tube Q1 and the second IGBT tube Q2 connected in sequence during a double pulse test; or to connect the third copper sheet U3 in parallel to the two ends of the first IGBT tube Q1 and the second IGBT tube Q2 connected in sequence during a short circuit test.

6. A double pulse and short circuit test method for an NPC I type three-level circuit according to any one of claims 1 to 4, characterized in that: Also includes: The overcurrent resistor Rs is set between the connection point of the first diode D1 and the second diode D2 and the connection point of the first capacitor C1 and the second capacitor C2 in the test circuit of the NPC I type three-level circuit; The current value flowing through the over-current resistor Rs is obtained to determine whether to disconnect the first selection device S1, the second selection device S2 or the third selection device S3 when the current value exceeds a preset threshold.

7. A double pulse and short circuit test method for an NPC I type three-level circuit according to claim 7, characterized in that: Also includes: The current value flowing through the overcurrent resistor Rs is obtained to determine whether the double pulse signal and / or high level signal sent to the gate of the first IGBT tube Q1, the second IGBT tube Q2, the third IGBT tube Q3 and / or the fourth IGBT tube Q4 will be changed to a low level signal when the current value exceeds a preset threshold.

8. A double pulse and short circuit test device for an NPC I type three-level circuit, used for performing double pulse and short circuit tests on a first IGBT tube Q1 or a fourth IGBT tube Q4 in a test circuit of an NPC I type three-level circuit, characterized in that: include: The first selection device S1 is arranged between the connection point of the second IGBT tube Q2 and the third IGBT tube Q3 and the connection point of the first diode D1 and the second diode D2 in the test circuit of the NPCI type three-level circuit; it is used to select the first IGBT tube Q1 or the fourth IGBT tube Q4 to perform a double pulse test, a short circuit test or disconnection; Overcurrent resistor Rs: arranged between the connection point of the first diode D1 and the second diode D2 and the connection point of the first capacitor C1 and the second capacitor C2 in the test circuit of the NPC I type three-level circuit; used to obtain the current flowing through the first IGBT tube Q1 and the second IGBT tube Q2, and the first inductor L1 or the first copper sheet U1 during the test; or used to obtain the current flowing through the third IGBT tube Q3 and the fourth IGBT tube Q4, and the first inductor L1 or the first copper sheet U1 during the test.

9. A double pulse and short circuit test device for an NPC I type three-level circuit, used for performing double pulse and short circuit tests on a second IGBT tube Q1 in a test circuit of an NPC I type three-level circuit, characterized in that: include: The second selection device S2 is arranged in parallel at both ends of the third IGBT tube Q3 and the fourth IGBT tube Q4 which are connected in sequence; Used to select to perform double pulse test, short circuit test or disconnection on the second IGBT tube Q2; Overcurrent resistor Rs: set between the connection point of the first diode D1 and the second diode D2 and the connection point of the first capacitor C1 and the second capacitor C2 in the test circuit of the NPC I type three-level circuit; used to obtain the current flowing through the first diode D1, the second IGBT tube Q2, and the third inductor L3 during the test.

10. A double pulse and short circuit test device for an NPCI type three-level circuit, used for performing double pulse and short circuit tests on a third IGBT tube Q3 in a test circuit of an NPCI type three-level circuit, characterized in that: include: A third selection device S3 is arranged in parallel at both ends of the first IGBT tube Q1 and the second IGBT tube Q2 which are connected in sequence; and is used to select a double pulse test, a short circuit test or a disconnection of the third IGBT tube Q2; Overcurrent resistor Rs: set between the connection point of the first diode D1 and the second diode D2 and the connection point of the first capacitor C1 and the second capacitor C2 in the test circuit of the NPC I type three-level circuit; used to obtain the current flowing through the second diode D2, the third IGBT tube Q3, and the second inductor L2 during the test.

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