A test circuit and a test method for switching device commutation process

Abstract

The test circuit and the test method provided by the application, the circuit comprises: a normal through-flow circuit connected in parallel with a switching device, a voltage equalization circuit connected in parallel with the switching device, a first end of a commutation circuit connected with a first end of the switching device, a first end of a charging circuit connected with a second end of the commutation circuit, a second end of the charging circuit connected with a second end of the switching device, the charging circuit is controlled to provide different polarity voltages, based on electrical parameters of the switching device, the voltage equalization circuit, the commutation circuit and the charging circuit, the operation state of the switching device and the commutation circuit is controlled, the current is commutated between the switching device, the voltage equalization circuit and the commutation circuit, various commutation tests are performed on the switching device, various working conditions of the commutation process of the switching device are simulated, and thus the commutation process of the switching device is tested only by using a simple circuit.

Description

Technical Field

[0001] This invention relates to the field of DC power transmission technology, specifically to a test circuit and test method for the commutation process of switching devices. Background Technology

[0002] As a core component of flexible DC power grids, the operational reliability of converter valves is a key factor affecting the safe operation of DC power grids. Among these, the reliability of the switching devices within the converter valve during the commutation process is a decisive factor in its safe operation. As a novel type of controllable current source converter, it has broad application prospects in the DC transmission field due to its advantages such as low cost, simple topology, and active / reactive power decoupling. However, the relevant test circuits for converter valves composed of switching devices during the commutation process are still under research. During the commutation process, the controllable current source converter composed of switching devices will withstand AC voltage on the AC side; therefore, it is necessary to test the switching devices under forward and reverse voltage conditions during commutation to verify their reliability in the converter valve operation. In the engineering research and development and application of controllable converter valves composed of switching devices, it is inevitable to test the switching devices under various operating conditions during the commutation process to ensure that the switching devices can withstand various conditions and meet key performance requirements. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that the commutation process of the reverse resistance IGCT is not tested under various operating conditions, thereby providing a test circuit and test method for the commutation process of switching devices.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] In a first aspect, embodiments of the present invention provide a test circuit for the commutation process of a switching device, comprising: a normal current-carrying circuit, a voltage equalization circuit, a charging circuit, and a commutation circuit, wherein the normal current-carrying circuit is connected in parallel with the switching device; the voltage equalization circuit is connected in parallel with the switching device; the commutation circuit has a first terminal connected to a first terminal of the switching device; the charging circuit has a first terminal connected to a second terminal of the commutation circuit and a second terminal connected to a second terminal of the switching device; the charging circuit is controlled to provide voltages of different polarities, and the operating states of the switching device and the commutation circuit are controlled based on the electrical parameters of the switching device, the voltage equalization circuit, the commutation circuit, and the charging circuit, so that the current commutates between the switching device, the voltage equalization circuit, and the commutation circuit, thereby performing various commutation tests on the switching device.

[0006] In one embodiment, the commutation test includes: reverse polarity voltage turn-off commutation test, reverse polarity voltage turn-on commutation test, positive polarity voltage turn-off commutation test, and positive polarity voltage turn-on commutation test.

[0007] In one embodiment, the normal current-carrying circuit includes: a current source and a first diode, wherein the first terminal of the current source is connected to the first terminal of the switching device; the cathode of the first diode is connected to the second terminal of the current source, and the anode of the first diode is connected to the second terminal of the switching device.

[0008] In one embodiment, the voltage equalization circuit includes: a voltage equalization resistor, a voltage equalization capacitor, and a second diode, wherein the first terminal of the voltage equalization resistor is connected to the first terminal of the switching device; the first terminal of the voltage equalization capacitor is connected to the second terminal of the voltage equalization resistor, and the second terminal of the capacitor is connected to the second terminal of the switching device; and the second diode is connected in parallel with the voltage equalization resistor.

[0009] In one embodiment, the commutation circuit includes a current-limiting inductor and a first switch, wherein the first switch has a first terminal connected to a first terminal of a switching device via the current-limiting inductor, and a second terminal connected to a first terminal of a charging circuit.

[0010] In one embodiment, the charging circuit includes: a charging capacitor, a constant current charger, and a plurality of second switches, wherein the first end of the charging capacitor is connected to the second end of the switching device, and the second end of the charging capacitor is connected to the second end of the commutation circuit; the positive terminal of the constant current charger is connected to the first and second ends of the charging capacitor respectively through two second switches, and the negative terminal is connected to the first and second ends of the charging capacitor respectively through two second switches.

[0011] Secondly, embodiments of the present invention provide a test method for the commutation process of a switching device. Based on the test circuit of the first aspect, the test method includes: controlling the initial state of the switching device to be on and the initial state of the commutation circuit to be off; controlling the charging circuit to provide voltages of different polarities; and controlling the operating state of the switching device and the commutation circuit based on the electrical parameters of the switching device, the voltage equalization circuit, the commutation circuit, and the charging circuit, so that the current commutates between the switching device, the voltage equalization circuit, and the commutation circuit, so as to perform various commutation tests on the switching device.

[0012] In one embodiment, the process of controlling the charging circuit to provide voltages of different polarities includes: controlling the second switch between the positive terminal of the constant current charger and the first terminal of the charging capacitor to close, and the second switch between the negative terminal of the constant current charger and the second terminal of the charging capacitor to close, wherein the constant current charger continuously charges the charging capacitor with positive voltage for a preset time, and the charging circuit provides a voltage of reverse polarity; and controlling the second switch between the positive terminal of the constant current charger and the second terminal of the charging capacitor to close, and the second switch between the negative terminal of the constant current charger and the first terminal of the charging capacitor to close, wherein the constant current charger continuously charges the charging capacitor with reverse voltage for a preset time, and the charging circuit provides a voltage of positive polarity.

[0013] In one embodiment, the process of performing a reverse polarity voltage turn-off commutation test on the switching device includes: controlling the charging circuit to provide a reverse polarity voltage; controlling the switching device to turn off and the first switch to turn on; detecting whether the current output by the current source is commutated from the switching device to the voltage equalization circuit and the commutation circuit; if the current output by the current source is commutated from the switching device to the voltage equalization circuit and the commutation circuit, then the commutation of the switching device is determined to be successful.

[0014] In one embodiment, the process of performing a reverse polarity voltage turn-on commutation test on the switching device includes: after performing a reverse polarity voltage turn-off commutation test on the switching device, detecting whether the voltage polarity of the charging capacitor is reversed; when the voltage polarity of the charging capacitor is reversed, detecting whether the voltage of the voltage equalization circuit is the same as the voltage of the charging capacitor; when the two are the same, closing the switching device; detecting whether the current is discharged to zero from the commutation circuit, the switching device commutation, and the voltage equalization circuit to the switching device; if the current is discharged to zero from the commutation circuit, the switching device commutation, and the voltage equalization circuit to the switching device, then the commutation of the switching device is determined to be successful.

[0015] In one embodiment, the process of performing a positive voltage turn-off commutation test on the switching device includes: controlling the charging circuit to provide a positive voltage; controlling the switching device to turn off and the first switch to turn on; detecting whether the current output by the current source is first commutated from the switching device to the voltage equalization circuit and then to the commutation circuit; if the current output by the current source is first commutated from the switching device to the voltage equalization circuit and then to the commutation circuit, then the commutation of the switching device is determined to be successful.

[0016] In one embodiment, the process of performing a positive polarity voltage turn-on commutation test on the switching device includes: after performing a reverse polarity voltage turn-off commutation test on the switching device, detecting whether the voltage of the equalizing circuit is the same as the voltage of the charging capacitor; when they are the same, closing the switching device; detecting whether the current is discharged to zero from the commutation circuit, the switching device commutation, and the equalizing circuit to the switching device; if the current is discharged to zero from the commutation circuit, the switching device commutation, and the equalizing circuit to the switching device, then the commutation of the switching device is determined to be successful.

[0017] The technical solution of this invention has the following advantages:

[0018] 1. The test circuit and test method provided by this invention include a normal current-carrying circuit connected in parallel with a switching device, a voltage equalization circuit connected in parallel with a switching device, a first terminal of a commutation circuit connected to a first terminal of a switching device, a first terminal of a charging circuit connected to a second terminal of a commutation circuit, and a second terminal of a charging circuit connected to a second terminal of a switching device. The charging circuit is controlled to provide voltages of different polarities. Based on the electrical parameters of the switching device, the voltage equalization circuit, the commutation circuit, and the charging circuit, the operating states of the switching device and the commutation circuit are controlled, causing current to commutate between the switching device, the voltage equalization circuit, and the commutation circuit. This allows for various commutation tests on the switching device to simulate various operating conditions of the commutation process, thereby achieving the test of the commutation process of the switching device using only a simple circuit.

[0019] 2. The test circuit and test method provided by the present invention control the charging circuit to provide voltages of different polarities and control the state of the switching device and the commutation circuit, so as to realize the reverse polarity voltage turn-off commutation test, reverse polarity voltage turn-on commutation test, positive polarity voltage turn-off commutation test, and positive polarity voltage turn-on commutation test of the switching device, thereby realizing the commutation process test of the switching device under all operating conditions. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 A schematic diagram of a specific example of a test circuit provided in an embodiment of the present invention;

[0022] Figure 2 A composition diagram of another specific example of the test circuit provided in an embodiment of the present invention;

[0023] Figure 3 A flowchart illustrating a specific example of the testing method provided in an embodiment of the present invention;

[0024] Figure 4 A flowchart illustrating a specific example of a reverse polarity voltage turn-off commutation test for an embodiment of the present invention;

[0025] Figure 5 A flowchart illustrating a specific example of a reverse polarity voltage turn-on commutation test for an embodiment of the present invention;

[0026] Figure 6 A flowchart illustrating a specific example of a positive polarity voltage turn-off commutation test for an embodiment of the present invention;

[0027] Figure 7 This is a flowchart illustrating a specific example of a positive voltage turn-on commutation test for an embodiment of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] Example 1

[0033] This invention provides a test circuit for the commutation process of a switching device, applicable to situations where the commutation process of a switching device is tested under various operating conditions, such as... Figure 1 As shown, it includes: a normal current-carrying circuit 1, a voltage equalization circuit 2, a charging circuit 3, and a commutation circuit 4.

[0034] like Figure 1As shown in the embodiment of the present invention, the normal current-carrying circuit is connected in parallel with the switching device, the voltage equalization circuit is connected in parallel with the switching device, the first end of the commutation circuit is connected to the first end of the switching device, the first end of the charging circuit is connected to the second end of the commutation circuit, and the second end of the charging circuit is connected to the second end of the switching device.

[0035] The switching device to be tested in this embodiment of the invention can be an inverse resistor IGCT, IGBT, etc.

[0036] In this embodiment of the invention, the charging circuit provides voltages of different polarities. Based on the electrical parameters of the switching devices, voltage equalization circuit, commutation circuit, and charging circuit, the operating states of the switching devices and commutation circuit are controlled to commutate the current between the switching devices, voltage equalization circuit, and commutation circuit, so as to perform various commutation tests on the switching devices. The commutation tests include: reverse polarity voltage turn-off commutation test, reverse polarity voltage turn-on commutation test, positive polarity voltage turn-off commutation test, and positive polarity voltage turn-on commutation test.

[0037] Specifically, in this embodiment of the invention, the initial state of the control switching device is on and the initial state of the commutation circuit is off. Therefore, the test current provided by the forward current-carrying circuit only flows through the switching device. When the control charging circuit provides a reverse polarity voltage, that is, the voltage at the first terminal of the charging circuit is lower than the voltage at its second terminal, the control switching device is turned off and the commutation circuit is turned on, and a reverse polarity voltage turn-off commutation test is performed on the switching device. Since the switching device is subjected to reverse voltage at this time, if the test current provided by the forward current-carrying circuit is commutated to the voltage equalization circuit and the commutation circuit, the commutation is successful.

[0038] Specifically, after the reverse polarity voltage turn-off commutation test, it is detected whether the voltage of the charging circuit is reversed in polarity. If it is reversed, it is determined whether the voltage of the charging circuit is equal to the voltage of the equalizing circuit. When they are equal, the switching device is controlled to conduct and a reverse polarity voltage turn-on commutation test is performed on the switching device. At this time, the switching device is subjected to positive voltage. If the current of the commutation circuit flows to the switching device and the equalizing circuit discharges to zero, the test current provided by the forward current circuit only flows through the switching device, then the commutation is successful.

[0039] Specifically, when the charging circuit provides a positive voltage, i.e., the voltage at the first terminal of the charging circuit is higher than the voltage at the second terminal, the switching device is turned off and the commutation circuit is turned on. A positive voltage turn-off commutation test is performed on the switching device. Since the switching device is under positive voltage at this time, if the test current provided by the forward current-carrying circuit first commutates to the voltage equalization circuit, and only after the voltage of the voltage equalization circuit is higher than the voltage of the charging circuit does the test current provided by the forward current-carrying circuit commutate to the commutation circuit, then the commutation is successful.

[0040] Specifically, after the positive voltage turn-off commutation test, it is checked whether the voltage of the charging circuit and the voltage of the equalizing circuit are equal. When they are equal, the switching device is controlled to turn on, and the positive voltage turn-on commutation test is performed on the switching device. At this time, the switching device is subjected to positive voltage. If the current of the commutation circuit is commutated to the switching device and the voltage equalizing circuit is discharged to zero, the test current provided by the forward current circuit only flows through the switching device, then the commutation is successful.

[0041] In one specific embodiment, such as Figure 2 As shown, the normal current-carrying circuit includes: a current source 11 and a first diode D1, wherein the first terminal of the current source is connected to the first terminal of the switching device; the cathode of the first diode is connected to the second terminal of the current source, and the anode of the first diode is connected to the second terminal of the switching device.

[0042] Specifically, the current source in this embodiment of the invention can be a programmable current source to provide the current required by the switching device under test. For example, the current source can be composed of a semi-controlled thyristor. The semi-controlled thyristor is controlled by a program. The input terminal of the current source can be connected to an AC source. After the AC power is rectified by the semi-controlled thyristor, DC power is obtained. The DC current is used to test the commutation process of the switching device.

[0043] In one specific embodiment, such as Figure 2 As shown, the voltage equalization circuit includes: a voltage equalization resistor R, a voltage equalization capacitor C1, and a second diode D2. The first end of the voltage equalization resistor is connected to the first end of the switching device; the first end of the voltage equalization capacitor is connected to the second end of the voltage equalization resistor, and the second end of the capacitor is connected to the second end of the switching device; the second diode is connected in parallel with the voltage equalization resistor.

[0044] Specifically, the voltage equalization circuit in this embodiment of the invention is actually an RCD snubber circuit. Optionally, the voltage equalization circuit can be other types of buffer circuits, such as an RC snubber circuit, which is not limited here.

[0045] In one specific embodiment, such as Figure 2 As shown, the commutation circuit includes: a current-limiting inductor L and a first switch T1, wherein the first switch has its first terminal connected to the first terminal of the switching device through the current-limiting inductor, and its second terminal connected to the first terminal of the charging circuit.

[0046] Specifically, in this embodiment of the invention, when current commutates between the commutation circuit and the switching device, the current-limiting inductor can limit the rate of change of the transfer current, thereby preventing inrush current from damaging the first switch. Furthermore, the first switch can be a controllable switch, such as an IGBT, but this is only an example and not a limitation.

[0047] In one specific embodiment, such as Figure 2As shown, the charging circuit includes: a charging capacitor C2, a constant current charger 31, and multiple second switches T2. The first end of the charging capacitor is connected to the second end of the switching device, and the second end is connected to the second end of the commutation circuit. The positive terminal of the constant current charger is connected to the first and second ends of the charging capacitor through two second switches, and the negative terminal is connected to the first and second ends of the charging capacitor through two second switches.

[0048] In this embodiment of the invention, when the second switch between the positive terminal of the constant current charger and the first terminal of the charging capacitor is closed, and the second switch between the negative terminal of the constant current charger and the second terminal of the charging capacitor is closed, the constant current charger continuously charges the charging capacitor with positive voltage for a preset time, and the charging circuit provides a reverse polarity voltage; when the second switch between the positive terminal of the constant current charger and the second terminal of the charging capacitor is closed, and the second switch between the negative terminal of the constant current charger and the first terminal of the charging capacitor is closed, the constant current charger continuously charges the charging capacitor with reverse voltage for a preset time, and the charging circuit provides a positive polarity voltage.

[0049] Example 2

[0050] This invention provides a method for testing the commutation process of a switching device, such as... Figure 3 As shown, based on the test circuit of Embodiment 1, the test method includes:

[0051] Step S11: Set the initial state of the control switching device to ON and the initial state of the commutation circuit to OFF.

[0052] Specifically, in this embodiment of the invention, the initial state of the control switching device is on and the initial state of the commutation circuit is off, so the test current provided by the forward current-carrying circuit only flows through the switching device.

[0053] Step S12: Control the charging circuit to provide voltages of different polarities. Based on the electrical parameters of the switching devices, voltage equalization circuit, commutation circuit and charging circuit, control the operating state of the switching devices and commutation circuit to make the current commutate between the switching devices, voltage equalization circuit and commutation circuit, so as to perform various commutation tests on the switching devices.

[0054] Specifically, in this embodiment of the invention, the initial state of the control switching device is on and the initial state of the commutation circuit is off. Therefore, the test current provided by the forward current-carrying circuit only flows through the switching device. When the control charging circuit provides a reverse polarity voltage, that is, the voltage at the first terminal of the charging circuit is lower than the voltage at its second terminal, the control switching device is turned off and the commutation circuit is turned on, and a reverse polarity voltage turn-off commutation test is performed on the switching device. Since the switching device is subjected to reverse voltage at this time, if the test current provided by the forward current-carrying circuit is commutated to the voltage equalization circuit and the commutation circuit, the commutation is successful.

[0055] Specifically, after the reverse polarity voltage turn-off commutation test, it is detected whether the voltage of the charging circuit is reversed in polarity. If it is reversed, it is determined whether the voltage of the charging circuit is equal to the voltage of the equalizing circuit. When they are equal, the switching device is controlled to conduct and a reverse polarity voltage turn-on commutation test is performed on the switching device. At this time, the switching device is subjected to positive voltage. If the current of the commutation circuit flows to the switching device and the equalizing circuit discharges to zero, the test current provided by the forward current circuit only flows through the switching device, then the commutation is successful.

[0056] Specifically, when the charging circuit provides a positive voltage, i.e., the voltage at the first terminal of the charging circuit is higher than the voltage at the second terminal, the switching device is turned off and the commutation circuit is turned on. A positive voltage turn-off commutation test is performed on the switching device. Since the switching device is under positive voltage at this time, if the test current provided by the forward current-carrying circuit first commutates to the voltage equalization circuit, and only after the voltage of the voltage equalization circuit is higher than the voltage of the charging circuit does the test current provided by the forward current-carrying circuit commutate to the commutation circuit, then the commutation is successful.

[0057] Specifically, after the positive voltage turn-off commutation test, it is checked whether the voltage of the charging circuit and the voltage of the equalizing circuit are equal. When they are equal, the switching device is controlled to turn on, and the positive voltage turn-on commutation test is performed on the switching device. At this time, the switching device is subjected to positive voltage. If the current of the commutation circuit is commutated to the switching device and the voltage equalizing circuit is discharged to zero, the test current provided by the forward current circuit only flows through the switching device, then the commutation is successful.

[0058] In one specific embodiment, the process of controlling the charging circuit to provide a reverse polarity voltage includes: controlling the second switch between the positive terminal of the constant current charger and the first terminal of the charging capacitor to close, controlling the second switch between the negative terminal of the constant current charger and the second terminal of the charging capacitor to close, the constant current charger continuously charging the charging capacitor with positive voltage for a preset time, and the charging circuit providing a reverse polarity voltage, that is, the voltage at the first terminal of the charging circuit is higher than its second terminal voltage, and the voltage at the first terminal of the charging capacitor is higher than its second terminal voltage.

[0059] The process of controlling the charging circuit to provide a positive voltage includes: closing the second switch between the positive terminal of the constant current charger and the second terminal of the charging capacitor, closing the second switch between the negative terminal of the constant current charger and the first terminal of the charging capacitor, the constant current charger continuously charging the charging capacitor under reverse voltage for a preset time, and the charging circuit providing a positive voltage, that is, the voltage at the second terminal of the charging circuit is higher than its first terminal voltage, and the voltage at the second terminal of the charging capacitor is higher than its first terminal voltage.

[0060] In one specific embodiment, such as Figure 4 As shown, the process of performing a reverse polarity voltage turn-off commutation test on a switching device includes:

[0061] Step S21: Control the charging circuit to provide a reverse polarity voltage.

[0062] Step S22: Control the switching device to turn off and the first switch to turn on.

[0063] Step S23: Detect whether the current output by the current source is commutated from the switching device to the voltage equalization circuit and the commutation circuit.

[0064] Step S24: If the current output from the current source is commutated from the switching device to the voltage equalization circuit and the commutation circuit, then the commutation of the switching device is determined to be successful.

[0065] Specifically, when the initial state of the switching device is on and the initial state of the first switching device is off, the current output by the current source flows only through the switching device. When the control charging circuit provides a reverse polarity voltage, that is, the voltage at the first terminal of the charging circuit is lower than the voltage at its second terminal, the control switching device is turned off and the first switch is turned on. Since the charging capacitor provides reverse voltage to the switching device, if the switching device commutates successfully, the current output by the current source first charges the voltage equalization capacitor and the charging capacitor, and the current commutates to the voltage equalization circuit and the commutation circuit.

[0066] In one specific embodiment, such as Figure 5 As shown, the process of performing a reverse polarity voltage turn-on commutation test on a switching device includes:

[0067] Step S31: After performing a reverse polarity voltage turn-off commutation test on the switching device, check whether the voltage polarity of the charging capacitor is reversed.

[0068] Step S32: After the voltage polarity of the charging capacitor is reversed, check whether the voltage of the equalizing circuit is the same as the voltage of the charging capacitor. When they are the same, close the switching device.

[0069] Step S33: Detect whether the current is discharged to zero by the commutation circuit, the switching device commutation, and the voltage equalization circuit to the switching device.

[0070] Step S34: If the current is discharged to zero from the commutation circuit, the switching device, and the voltage equalization circuit to the switching device, then the commutation of the switching device is determined to be successful.

[0071] In this embodiment of the invention, after performing a reverse polarity voltage turn-off commutation test on the switching device, a reverse polarity voltage turn-on commutation test is performed on the switching device. Specifically, when the initial state of the switching device is on and the initial state of the first switching device is off, the current output by the current source flows only through the switching device. When the charging circuit provides a reverse polarity voltage, that is, the voltage at the first terminal of the charging circuit is lower than the voltage at its second terminal, the switching device is turned off and the first switch is turned on. Since the charging capacitor provides reverse voltage to the switching device, if the switching device commutates successfully, the current output by the current source first charges the equalizing capacitor and the charging capacitor, and the current commutates to the equalizing circuit and the commutation circuit. The charging capacitor is continuously charged until the voltage of the charging capacitor reverses. When the voltage of the charging capacitor is equal to the voltage of the equalizing capacitor, the switching device is turned on. If the switching device commutates successfully, the current commutates from the commutation circuit to the switching device, and the equalizing capacitor discharges to zero. The current output by the current source flows only through the switching device.

[0072] In one specific embodiment, such as Figure 6 As shown, the process of performing a positive voltage turn-off commutation test on a switching device includes:

[0073] Step 41: Control the charging circuit to provide a positive voltage.

[0074] Step 42: Control the switching device to turn off and the first switch to turn on.

[0075] Step 43: Detect whether the current output from the current source is first commutated from the switching device to the voltage equalization circuit, and then commutated to the commutation circuit.

[0076] Step 44: If the current output from the current source is first commutated from the switching device to the voltage equalization circuit, and then commutated to the commutation circuit, then the commutation of the switching device is determined to be successful.

[0077] Specifically, when the initial state of the switching device is on and the initial state of the first switching device is off, the current output by the current source flows only through the switching device. The control charging circuit provides a positive voltage, that is, the voltage at the first terminal of the charging circuit is higher than the voltage at the second terminal, so the control switching device is turned off and the first switch is turned on. Since the charging capacitor provides a positive voltage to the switching device, if the switching device commutates successfully, the current output by the current source first charges the equalizing capacitor. When the voltage of the equalizing capacitor is higher than the voltage of the charging capacitor, the current output by the current source charges the charging capacitor.

[0078] In one specific embodiment, such as Figure 7 As shown, the process of performing a positive voltage turn-on commutation test on a switching device includes:

[0079] Step S51: After performing a reverse polarity voltage turn-off commutation test on the switching device, check whether the voltage of the equalizing circuit is the same as the voltage of the charging capacitor. When they are the same, close the switching device.

[0080] Step S52: Detect whether the current is discharged to zero from the commutation circuit, the switching device commutation, and the voltage equalization circuit to the switching device.

[0081] Step S53: If the current is discharged to zero from the commutation circuit, the switching device, and the voltage equalization circuit to the switching device, then the commutation of the switching device is determined to be successful.

[0082] In this embodiment of the invention, after performing a positive voltage turn-off commutation test on the switching device, a positive voltage turn-on commutation test is performed on the switching device. Specifically, when the initial state of the switching device is on and the initial state of the first switching device is off, the current output by the current source flows only through the switching device. The charging circuit provides a positive voltage, that is, the voltage at the first terminal of the charging circuit is higher than the voltage at its second terminal, controlling the switching device to turn off and the first switch to turn on. Since the charging capacitor provides a positive voltage to the switching device, if the switching device commutates successfully, the current output by the current source first charges the equalizing capacitor. When the voltage of the equalizing capacitor is higher than the voltage of the charging capacitor, the current output by the current source charges the charging capacitor. When the voltage of the charging capacitor is equal to the voltage of the equalizing capacitor, the switching device is controlled to turn on. If the switching device commutates successfully, the current commutates from the commutation circuit to the switching device, and the equalizing capacitor discharges to zero. The current output by the current source flows only through the switching device.

[0083] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A test circuit for commutation of a switching device, characterized in that The test circuit comprises: a normal conduction circuit, a voltage equalization circuit, a charging circuit and a commutation circuit, wherein, the normal conduction circuit is connected in parallel with the switching device; the voltage equalization circuit is connected in parallel with the switching device; the commutation circuit has a first end connected with a first end of the switching device; the charging circuit has a first end connected with a second end of the commutation circuit and a second end connected with a second end of the switching device; the charging circuit is controlled to provide different polarity voltages, the switching device, the voltage equalization circuit, the commutation circuit and the charging circuit are controlled based on electrical parameters of the switching device, the voltage equalization circuit, the commutation circuit and the charging circuit, the running states of the switching device and the commutation circuit are controlled, and current is commutated among the switching device, the voltage equalization circuit and the commutation circuit to perform multiple commutation tests on the switching device; the commutation tests comprise: reverse polarity voltage off commutation test, reverse polarity voltage on commutation test, positive polarity voltage off commutation test and positive polarity voltage on commutation test; the normal conduction circuit comprises: a current source and a first diode, wherein the current source has a first end connected with a first end of the switching device, and the first diode has a cathode connected with a second end of the current source and an anode connected with a second end of the switching device; the voltage equalization circuit comprises: a voltage equalization resistor, a voltage equalization capacitor and a second diode, wherein the voltage equalization resistor has a first end connected with a first end of the switching device, the voltage equalization capacitor has a first end connected with a second end of the voltage equalization resistor and a second end connected with a second end of the switching device, and the second diode is connected in parallel with the voltage equalization resistor; the commutation circuit comprises: a current-limiting inductor and a first switch, wherein the first switch has a first end connected with a first end of the switching device through the current-limiting inductor and a second end connected with a first end of the charging circuit.

2. The test circuit for commutation of a switching device according to claim 1, characterized in that, the charging circuit comprises: a charging capacitor, a constant-current charger and a plurality of second switches, wherein, the charging capacitor has a first end connected with a second end of the switching device and a second end connected with a second end of the commutation circuit; the constant-current charger has a positive electrode connected with the first end and the second end of the charging capacitor through two second switches respectively and a negative electrode connected with the first end and the second end of the charging capacitor through two second switches respectively.

3. A method of testing the commutation of a switching device, characterized in that The test method based on any one of claims 1-2 comprises: controlling the initial state of the switching device to be on and the initial state of the commutation circuit to be off; controlling the charging circuit to provide different polarity voltages, controlling the switching device and the commutation circuit based on electrical parameters of the switching device, the voltage equalization circuit, the commutation circuit and the charging circuit, and making current commutate among the switching device, the voltage equalization circuit and the commutation circuit to perform multiple commutation tests on the switching device; the commutation tests comprise: reverse polarity voltage off commutation test, reverse polarity voltage on commutation test, positive polarity voltage off commutation test and positive polarity voltage on commutation test.

4. The method of claim 3, wherein the test signal is a pulse signal. The process of controlling the charging circuit to provide different polarity voltages comprises: The second switch between the positive pole of the constant current charger and the first end of the charging capacitor is closed, the second switch between the negative pole of the constant current charger and the second end of the charging capacitor is closed, the constant current charger continuously charges the charging capacitor with positive voltage for a preset time, and the charging circuit provides negative voltage. The second switch between the positive pole of the constant current charger and the first end of the charging capacitor is closed, the second switch between the negative pole of the constant current charger and the second end of the charging capacitor is closed, the constant current charger continuously charges the charging capacitor with positive voltage for a preset time, and the charging circuit provides negative voltage.

5. The method of claim 4, wherein the test signal is a pulse signal. The process of conducting reverse polarity voltage off commutation test on the switching device includes: The charging circuit provides negative voltage; The switching device is turned off, and the first switch is turned on; It is detected whether the current output by the current source is commutated from the switching device to the voltage equalizing circuit and the commutation circuit; If the current output by the current source is commutated from the switching device to the voltage equalizing circuit and the commutation circuit, it is determined that the switching device is successfully commutated.

6. The method of claim 5, wherein the test signal is a pulse signal. The process of conducting reverse polarity voltage off commutation test on the switching device includes: After the reverse polarity voltage off commutation test on the switching device, it is detected whether the voltage polarity of the charging capacitor is reversed; When the voltage polarity of the charging capacitor is reversed, it is detected whether the voltage of the voltage equalizing circuit is the same as the voltage of the charging capacitor, and when they are the same, the switching device is closed; It is detected whether the current is discharged to zero from the commutation circuit, the switching device and the voltage equalizing circuit to the switching device; If the current is discharged to zero from the commutation circuit, the switching device and the voltage equalizing circuit to the switching device, it is determined that the switching device is successfully commutated.

7. The method of claim 4, wherein the method further comprises: The process of conducting reverse polarity voltage off commutation test on the switching device includes: The charging circuit provides negative voltage; The switching device is turned off, and the first switch is turned on; It is detected whether the current output by the current source is commutated from the switching device to the voltage equalizing circuit and the commutation circuit; If the current output by the current source is commutated from the switching device to the voltage equalizing circuit and the commutation circuit, it is determined that the switching device is successfully commutated.

8. The method of claim 7, wherein the method further comprises: The process of conducting reverse polarity voltage off commutation test on the switching device includes: After the reverse polarity voltage off commutation test on the switching device, it is detected whether the voltage polarity of the charging capacitor is reversed; When the voltage polarity of the charging capacitor is reversed, it is detected whether the voltage of the voltage equalizing circuit is the same as the voltage of the charging capacitor, and when they are the same, the switching device is closed; It is detected whether the current is discharged to zero from the commutation circuit, the switching device and the voltage equalizing circuit to the switching device; If the current is discharged to zero from the commutation circuit, the switching device and the voltage equalizing circuit to the switching device, it is determined that the switching device is successfully commutated.

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