Dynamic characteristic test circuit and method of t-type three-level converter unit

Abstract

The application provides a kind of T type three-level commutation unit dynamic characteristic test circuit and method, comprising: charge-discharge control unit, provide charging current or discharge path for first, second capacitor;The series connection of first capacitor and second capacitor;T type three-level commutation unit, current flow direction and output level are adjusted through switch timing;Inductance, first end connects the voltage output end of T type three-level commutation unit, second end connects the connecting node of first, second container.The test circuit of the application is simple in structure, high in efficiency, comprehensive in function, and convenient for automatic testing;Different working conditions can be tested without switching inductance position in the same circuit, and it is easy to operate;And avoid changing the consistency of the circuit due to inductance position switching, the test accuracy is high;When inductance enters the freewheeling, the voltage across the inductance is 0V, restores the actual application working condition, further improves the test accuracy;Adopt overcurrent protection, avoid damaging device or circuit when current is too large.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit testing, and in particular to a dynamic characteristic testing circuit and method for a T-type three-level commutator unit. Background Technology

[0002] Power devices are widely used in various application fields. Therefore, designers need to design the dynamic characteristics of power devices according to the characteristics of different application fields to better meet different needs. Application engineers need to design different peripheral circuits based on the dynamic characteristics of power devices to ensure they operate at their optimal state. For commutation units composed of power devices in bridge applications, the dynamic characteristics of the devices can be tested using a dual-pulse circuit. However, the operating conditions of commutation units composed of power devices in T-type three-level converters are quite different from those in bridge applications, and traditional dual-pulse circuits cannot be directly used for testing. Therefore, new circuits need to be designed to test the dynamic characteristics of T-type three-level commutation units.

[0003] Existing technologies have designed different test circuits for different operating states of the T-type three-level circuit. During the test, the test circuit must be switched by changing the position of the inductor, which makes the test process relatively complex. When the inductor is connected between the DC bus and the switching device, the voltage across the inductor is not 0V when the inductor enters freewheeling mode, which is different from the actual operation. At the same time, the inductor is not an ideal device and has parasitic capacitance. The inductor in different positions will change the consistency of the circuit and reduce the accuracy of the test.

[0004] Therefore, simplifying the testing process, ensuring that the test results are consistent with the actual working conditions, and improving the accuracy of the test have become some of the problems that need to be solved by those skilled in the art. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a dynamic characteristic testing circuit and method for a T-type three-level converter unit, which solves the problems of complex dynamic characteristic testing process, inconsistent testing with actual application working state, and poor accuracy in the prior art.

[0006] To achieve the above and other related objectives, the present invention provides a dynamic characteristic testing circuit for a T-type three-level commutator unit, wherein the dynamic characteristic testing circuit for the T-type three-level commutator unit includes at least:

[0007] Charge / discharge control unit, first capacitor, second capacitor, T-type three-level commutator unit and inductor;

[0008] The charging and discharging control unit provides charging current or a discharging path for the first capacitor and the second capacitor.

[0009] The upper plate of the first capacitor is connected to the positive output terminal of the charge-discharge control unit, the lower plate of the first capacitor is connected to the upper plate of the second capacitor, and the lower plate of the second capacitor is connected to the negative output terminal of the charge-discharge control unit.

[0010] The T-type three-level converter unit adjusts the current flow direction and output level through switching timing, and includes a first power device, a second power device, a third power device, a fourth power device, a first diode, a second diode, a third diode, and a fourth diode. The first terminal of the first power device is connected to the positive output terminal of the charge / discharge control unit, and its second terminal is connected to the first terminal of the second power device and serves as the output terminal of the T-type three-level converter unit. The second terminal of the second power device is connected to the negative output terminal of the charge / discharge control unit. The second terminal of the third power device is connected to the connection node between the first capacitor and the second capacitor, and its first terminal is connected to the first terminal of the fourth power device. The second terminal of the fourth power device is connected to the output terminal of the T-type three-level converter unit. Each diode is connected in parallel across the two ends of its corresponding power device, wherein the cathode of the diode is connected to the first terminal of the corresponding power device, and the anode is connected to the second terminal of the corresponding power device.

[0011] The first end of the inductor is connected to the voltage output terminal of the T-type three-level converter unit, and the second end is connected to the connection node between the first capacitor and the second capacitor.

[0012] Optionally, the charging and discharging control unit includes a DC power supply, a first switch, and a second switch; a first end of the first switch is connected to the positive terminal of the DC power supply, and a second end is connected to the upper plate of the first capacitor; a first end of the second switch is connected to the second end of the first switch, and a second end is connected to the negative terminal of the DC power supply.

[0013] Alternatively, the charge / discharge control unit further includes a resistor connected between the second terminal of the second switch and the negative terminal of the DC power supply.

[0014] Optionally, the dynamic characteristic test circuit of the T-type three-level converter unit further includes a first overcurrent protection unit and a second overcurrent protection unit. The first overcurrent protection unit is connected between the positive output terminal of the charge and discharge control unit and the upper plate of the first capacitor, and the second overcurrent protection unit is connected between the lower plate of the first capacitor and the upper plate of the second capacitor.

[0015] Alternatively, each diode can be a body diode or an independent device.

[0016] To achieve the above and other related objectives, the present invention provides a method for testing the dynamic characteristics of a T-type three-level converter unit, implemented using the aforementioned dynamic characteristic testing circuit for the T-type three-level converter unit. The method for testing the dynamic characteristics of the T-type three-level converter unit includes at least the following:

[0017] Tests were conducted under positive voltage and positive current conditions to evaluate the dynamic characteristics of the first power device and the third diode connected in parallel across the third power device.

[0018] The test was conducted under positive voltage and negative current conditions to evaluate the dynamic characteristics of the third power device and the first diode connected in parallel across the first power device.

[0019] Optionally, the method for evaluating the dynamic characteristics of the first power device and the third diode includes:

[0020] 11) Turn on the first power device, turn off the second power device and the third power device, and the current flows from the upper plate of the first capacitor through the first power device and the inductor back to the lower plate of the first capacitor;

[0021] 12) Turn off the first power device and the second power device, turn on the fourth power device, turn on the third diode to enable freewheeling, and the current flows from the second end of the inductor through the third diode and the fourth power device back to the first end of the inductor;

[0022] 13) Turn on the first power device, turn off the second power device and the third power device, the third diode undergoes reverse recovery, and the current flows from the upper plate of the first capacitor through the first power device and the inductor back to the lower plate of the first capacitor.

[0023] Alternatively, the fourth power device in step 11) may be turned on or off; the third power device in step 12) may be turned on or off; and the fourth power device in step 13) may be turned on or off.

[0024] Optionally, the method for evaluating the dynamic characteristics of the third power device and the first diode includes:

[0025] 21) Turn on the second power device, turn off the first power device, the third power device and the fourth power device, and the current flows from the upper plate of the second capacitor through the inductor and the second power device back to the lower plate of the second capacitor;

[0026] 22) Turn off the second power device and the third power device, turn on the first diode to freewheel, and the current flows from the first end of the inductor through the first diode and the first capacitor back to the second end of the inductor;

[0027] 23) Turn off the first power device and the second power device, turn on the third power device, the first diode undergoes reverse recovery, and the current flows from the first end of the inductor through the fourth diode connected in parallel across the fourth power device and the third power device back to the second end of the inductor.

[0028] Alternatively, in step 22), the first power device is turned on or off, and the fourth power device is turned on or off; in step 23), the fourth power device is turned on or off.

[0029] As described above, the dynamic characteristic testing circuit and method for the T-type three-level commutator unit of the present invention have the following beneficial effects:

[0030] 1. The dynamic characteristic test circuit and method of the T-type three-level converter unit of the present invention can realize the test of the dynamic characteristics of the T-type three-level converter unit. The test circuit has a simple structure, high efficiency, and comprehensive functions, and is easy to realize automated testing.

[0031] 2. The dynamic characteristic test circuit and method of the T-type three-level commutator unit of the present invention can achieve different working conditions test in the same circuit without switching the inductor position, which is convenient to operate; and avoids changes in circuit consistency due to the switching of inductor position, resulting in high test accuracy.

[0032] 3. In the dynamic characteristic test circuit and method of the T-type three-level converter unit of the present invention, when the inductor enters freewheeling, the voltage across the inductor is 0V, which restores the actual application conditions and further improves the test accuracy.

[0033] 4. The dynamic characteristic test circuit and method of the T-type three-level converter unit of the present invention adopts overcurrent protection to avoid damage to the device or circuit when the current is too large. Attached Figure Description

[0034] Figure 1 The diagram shows the structure of the dynamic characteristic test circuit of the T-type three-level converter unit of the present invention.

[0035] Figure 2 The diagram shows the control timing of the present invention under positive voltage and positive current conditions.

[0036] Figure 3 The diagram shows the current flow under positive voltage and positive current conditions according to the present invention.

[0037] Figure 4 The diagram shows the simulation results of the present invention under positive voltage and positive current conditions.

[0038] Figure 5The diagram shows the control timing of the present invention under positive voltage and negative current conditions.

[0039] Figure 6 The diagram shows the current flow under positive voltage and negative current conditions according to the present invention.

[0040] Figure 7 The diagram shows the simulation results of the present invention under positive voltage and negative current conditions.

[0041] Component designation explanation

[0042] 1. Dynamic characteristic test circuit of T-type three-level commutator unit

[0043] 11. Charge / Discharge Control Unit

[0044] 12 T-type three-level converter units

[0045] 13 First Overcurrent Protection Unit

[0046] 14 Second Overcurrent Protection Unit Detailed Implementation

[0047] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0048] Please see Figures 1 to 7 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0049] like Figure 1 As shown, this embodiment provides a dynamic characteristic test circuit 1 for a T-type three-level converter unit. The dynamic characteristic test circuit 1 for the T-type three-level converter unit includes:

[0050] The charging and discharging control unit 11, the first capacitor C1, the second capacitor C2, the T-type three-level commutator unit 12, and the inductor L1.

[0051] like Figure 1 As shown, the charging and discharging control unit 11 provides charging current or discharging path for the first capacitor C1 and the second capacitor C2.

[0052] Specifically, in this embodiment, the charge / discharge control unit 11 includes a DC power supply VDD, a first switch SW1, and a second switch SW2. The first terminal of the first switch SW1 is connected to the positive terminal of the DC power supply VDD, and the second terminal (serving as the positive output terminal of the charge / discharge control unit 11) is connected to the upper plate of the first capacitor C1. The first terminal of the second switch SW2 is connected to the second terminal of the first switch SW1, and the second terminal is connected to the negative terminal of the DC power supply VDD (serving as the negative output terminal of the charge / discharge control unit 11). When the first switch SW1 is on and the second switch SW2 is off, the DC power supply VDD charges the first capacitor C1 and the second capacitor C2 through the first switch SW1. When the first switch SW1 is off and the second switch SW2 is on, the first capacitor C1 and the second capacitor C2 discharge through the second switch SW2.

[0053] In another implementation of the present invention, the charge and discharge control unit 11 further includes a resistor R1, which is connected between the second terminal of the second switch SW2 and the negative terminal of the DC power supply VDD, and is used to control the discharge current of the first capacitor C1 and the second capacitor C2, so that the voltage of the first capacitor C1 and the second capacitor C2 can be safely discharged after the experiment ends.

[0054] like Figure 1 As shown, the upper plate of the first capacitor C1 is connected to the positive terminal of the output of the charge / discharge control unit 11, the lower plate of the first capacitor C1 is connected to the upper plate of the second capacitor C2, and the lower plate of the second capacitor C2 is connected to the negative terminal of the output of the charge / discharge control unit 11.

[0055] In another implementation of the present invention, the dynamic characteristic test circuit 1 of the T-type three-level converter unit further includes a first overcurrent protection unit 13 and a second overcurrent protection unit 14 to prevent damage to devices and circuits during overcurrent. The first overcurrent protection unit 13 is connected between the positive output terminal of the charge / discharge control unit 11 and the upper plate of the first capacitor C1. The first overcurrent protection unit 13 detects the charging / discharging current of the first capacitor C1, and disconnects the connection between the upper plate of the first capacitor C1 and the positive output terminal of the charge / discharge control unit 11 when the current exceeds a corresponding preset value, thereby achieving overcurrent protection. The second overcurrent protection unit 14 is connected between the lower plate of the first capacitor C1 and the upper plate of the second capacitor C2. The second overcurrent protection unit 14 detects the charging / discharging current of the second capacitor C2, and disconnects the connection between the upper plate of the second capacitor C2 and the lower plate of the first capacitor C1 when the current exceeds a corresponding preset value, thereby achieving overcurrent protection. The first overcurrent protection unit 13 and the second overcurrent protection unit 14 can be implemented by detecting a sampling resistor or directly measuring the current, which will not be elaborated here.

[0056] like Figure 1 As shown, the T-type three-level converter unit 12 adjusts the current flow direction and output level by adjusting the switching timing.

[0057] Specifically, the T-type three-level converter unit 12 includes a first power device S1, a second power device S2, a third power device S3, a fourth power device S4, a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The first terminal of the first power device S1 is connected to the positive output terminal of the charge / discharge control unit 11, and its second terminal is connected to the first terminal of the second power device S2 and serves as the output terminal of the T-type three-level converter unit 12. Its control terminal receives a first control signal CTL1. The second terminal of the second power device S2 is connected to the negative output terminal of the charge / discharge control unit 11, and its control terminal receives a second control signal CTL2. The second terminal of the third power device S3 is connected to the connection node between the first capacitor C1 and the second capacitor C2, and its first terminal is connected to the first terminal of the fourth power device S4. Its control terminal receives a third control signal CTL3. The second terminal of the fourth power device S4 is connected to the output terminal of the T-type three-level converter unit 12, and its control terminal receives a fourth control signal CTL4. Each diode is connected in parallel across the two ends of its corresponding power device. In this example, the cathode of the first diode D1 is connected to the first end of the first power device S1, and the anode is connected to the second end of the first power device S1; the cathode of the second diode D2 is connected to the first end of the second power device S2, and the anode is connected to the second end of the second power device S2; the cathode of the third diode D3 is connected to the first end of the third power device S3, and the anode is connected to the second end of the third power device S3; the cathode of the fourth diode D2 is connected to the first end of the fourth power device S4, and the anode is connected to the second end of the fourth power device S4.

[0058] It should be noted that in this embodiment, the first power device S1, the second power device S2, the third power device S3, and the fourth power device S4 are implemented using NMOS transistors. In this case, the first terminal of each power device is the drain, the second terminal is the source, and the gate serves as the control terminal to receive the control signal (high level for conduction). In actual use, the corresponding power device type can be set as needed, including but not limited to MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) and IGBT (Insulated Gate Bipolar Transistor). Any power device with controllable switching function is applicable to this invention, and will not be described in detail here.

[0059] It should be noted that the first diode D1, the second diode D2, the third diode D3, and the fourth diode D4 are the body diodes of the corresponding power devices, or they are independent devices connected in parallel across the corresponding power devices.

[0060] like Figure 1 As shown, the first end of the inductor L1 is connected to the voltage output terminal of the T-type three-level converter unit 12, and the second end is connected to the connection node of the first capacitor C1 and the second capacitor C2.

[0061] Specifically, the inductor L1 is a load inductor that provides the current required by the load. In this invention, the connection method of the inductor L1 can reproduce the working condition of the T-type three-level commutator unit 12 in actual applications, and at the same time, there is no need to switch the inductor position during the test, which effectively improves the accuracy and convenience of the test.

[0062] like Figure 1 As shown, the T-type three-level converter unit 12 is mainly used in the inverter circuit. The three-level designation means that the output voltage can have three values: 0.5U, 0, and -0.5U, where U is the voltage value of the DC power supply VDD. For voltage-type inverters, when a non-resistive load is applied, there is a phase difference between the output voltage and current, resulting in four operating conditions: positive voltage and positive current, positive voltage and negative current, negative voltage and positive current, and negative voltage and negative current.

[0063] The positive and negative currents are controlled by adjusting the current polarity of the inductor L1. When the first power device S1 is on and the second power device S2 and the third power device S3 are off, the voltage across the first capacitor C1 is applied to the inductor L1, and the current flows through C1-S1-L1-C1, gradually increasing under the capacitor's influence. This current is defined as positive. When the second power device S2 is on and the other switches are off, the voltage across the second capacitor C2 is applied to the inductor L1 in the reverse direction, and the current flows through C2-L1-S2-C2, gradually increasing under the capacitor's influence. This current is defined as negative. Therefore, by controlling S1 to S4, either the positive or negative current can be achieved without switching the inductor's position. When the third power device S3 is on, the voltage across the inductor L1 is positive; when the third power device S3 and the fourth power device S4 are on, the voltage across the inductor L1 is 0V, which is the same as the actual operating condition of the T-type three-level converter unit.

[0064] In this invention, positive voltage output is achieved by controlling the first power device S1, and negative voltage output is achieved by controlling the second power device S2. The positive and negative voltage operating conditions are mirror-symmetrical. Therefore, the dynamic characteristics of the power device can be determined by testing only the two operating conditions: positive voltage and positive current, and positive voltage and negative current. The dynamic characteristic testing method for the T-type three-level commutator of this invention includes:

[0065] Tests were conducted under positive voltage and positive current conditions to evaluate the dynamic characteristics of the first power device S1 and the third diode D3 connected in parallel across the third power device S3.

[0066] Specifically, it includes the following steps, such as Figures 2-4 As shown:

[0067] 11) Turn on the first power device S1, turn off the second power device S2 and the third power device S3, and the fourth power device S4 can be turned on or off. The current flows from the upper plate of the first capacitor C1 through the first power device S1 and the inductor L1 back to the lower plate of the first capacitor C1. Figure 2 As shown, in this example, the control signal is 1001 (corresponding sequentially to the first control signal CTL1, the second control signal CTL2, the third control signal CTL3, and the fourth control signal CTL4), that is, the first power device S1 and the fourth power device S4 are turned on, and the second power device S2 and the third power device S3 are turned off; at this time, the current in the inductor L1 gradually increases under the action of the voltage across the first capacitor C1, and energy is stored in the inductor L1, with the current flow as shown... Figure 3 As shown in 1001, the output voltage Vo is a positive voltage (maximum value is 0.5U).

[0068] 12) Turn off the first power device S1 and the second power device S2, and turn on the fourth power device S4. The third power device S3 can be turned on or off. The current flows through the third diode D3 to enable freewheeling, and the current returns from the second terminal of the inductor L1 through the third diode D3 and the fourth power device S4 to the first terminal of the inductor L1. Figure 2 As shown, in this example, the control signal is 0011, meaning the first power device S1 and the second power device S2 are off, while the third power device S3 and the fourth power device S4 are on. During the process of the first power device S1 being off, due to the non-sudden change in inductor current, the third diode D3 starts freewheeling, and the current flow is as follows: Figure 3 As shown in 0011, the output voltage Vo switches from a positive voltage to 0V. During the freewheeling process, the third power device S3 is turned on (turning on the third power device S3 is not mandatory) to achieve synchronous rectification.

[0069] 13) Turn on the first power device S1, turn off the second power device S2 and the third power device S3, and the fourth power device S4 can be turned on or off. Current flows from the upper plate of the first capacitor C1 through the first power device S1 and the inductor L1 back to the lower plate of the first capacitor C1. For example... Figure 2As shown, in this example, the control signal is 1001, meaning the first power device S1 and the fourth power device S4 are turned on, while the second power device S2 and the third power device S3 are turned off. Since the third diode D3 carried current in the previous stage, it will undergo reverse recovery when the first power device S1 is turned on. The current flow is as follows... Figure 3 As shown in 1001, the output voltage Vo switches from 0V to a positive voltage.

[0070] like Figure 4 The figure shows the simulation results of the dynamic characteristics under positive voltage and positive current conditions. The solid line represents the drain-source voltage curve of the first power device S1, and the dashed line represents the current curve flowing through the first power device S1. The peak of the current curve represents the reverse recovery current of the third diode D3. Therefore, by performing two switching operations on the first power device S1, the dynamic characteristics of both the first power device S1 and the third diode D3 can be evaluated.

[0071] The test was conducted under positive voltage and negative current conditions to evaluate the dynamic characteristics of the third power device S3 and the first diode D1 connected in parallel across the first power device S1.

[0072] Specifically, it includes the following steps, such as Figures 5-7 As shown:

[0073] 21) The second power device S2 is turned on, and the first power device S1, the third power device S3, and the fourth power device S4 are turned off. Current flows from the upper plate of the second capacitor C2 through the inductor L1 and the second power device S2 back to the lower plate of the second capacitor C2. Figure 5 As shown, in this example, the control signal is 0100. At this time, the inductor L1 is charged by the voltage across the capacitor C2, and the current in the inductor L1 gradually increases, with the current flow as shown. Figure 6 As shown in 0100, the output voltage Vo is a positive voltage (maximum value is 0.5U).

[0074] 22) Turn off the second power device S2 and the third power device S3. The first power device S1 can be turned on or off, and the fourth power device S4 can be turned on or off. The first diode D1 is turned on for freewheeling, and the current flows from the first end of the inductor L1 through the first diode D1 and the first capacitor C1 back to the second end of the inductor L1. Figure 5As shown, in this example, the control signal is 1001, meaning the second power device S2 and the third power device S3 are turned off, while the first power device S1 and the fourth power device S4 are turned on. At this time, the inductor L1 charges the first capacitor C1. During the process of the second power device S2 being turned off, based on the characteristic that the inductor current does not change abruptly, the inductor current freewheels through the first diode D1, and the current flow is as follows. Figure 6 As shown in 1001, the output voltage Vo switches from a positive voltage to 0V. During this process, the first power device S1 is turned on (turning on the first power device S1 is not mandatory) to enter synchronous rectification.

[0075] 23) Turn off the first power device S1 and the second power device S2, and turn on the third power device S3. The fourth power device S4 can be turned on or off. The first diode D1 undergoes reverse recovery, and the current flows from the first end of the inductor L1 through the fourth diode D4 connected in parallel across the fourth power device S4 and the third power device S3 back to the second end of the inductor L1. Figure 5 As shown, in this example, the control signal is 0011, meaning the first power device S1 and the second power device S2 are off, while the third power device S3 and the fourth power device S4 are on. At this time, due to the freewheeling current of the first diode D1, when the third power device S3 is turned on, the first diode D1 will undergo reverse recovery, and the current flow is as follows: Figure 6 As shown in 0011, the output voltage Vo switches from positive voltage to 0V.

[0076] like Figure 7 The figure shows the simulation results of the dynamic characteristics under positive voltage and negative current conditions. The solid line represents the drain-source voltage curve of the third power device S3, and the dashed line represents the current curve flowing through the third power device S3. The peak of the current curve represents the reverse recovery current of the first diode D1. Therefore, the dynamic characteristics of the third power device S3 and the first diode D1 can be evaluated through the aforementioned switching operation.

[0077] In summary, this invention provides a dynamic characteristic testing circuit and method for a T-type three-level commutator unit, comprising: a charge / discharge control unit, a first capacitor, a second capacitor, a T-type three-level commutator unit, and an inductor; the charge / discharge control unit provides charging current or a discharge path for the first capacitor and the second capacitor; the upper plate of the first capacitor is connected to the positive output terminal of the charge / discharge control unit, the lower plate of the first capacitor is connected to the upper plate of the second capacitor, and the lower plate of the second capacitor is connected to the negative output terminal of the charge / discharge control unit; the T-type three-level commutator unit adjusts the current flow direction and output level by adjusting the switching timing, and includes a first power device, a second power device, a third power device, a fourth power device, a first diode, a second diode, a third diode, and a fourth diode; the first power device... The first end of the device is connected to the positive output terminal of the charge / discharge control unit, and the second end is connected to the first end of the second power device and serves as the output terminal of the T-type three-level converter unit; the second end of the second power device is connected to the negative output terminal of the charge / discharge control unit; the second end of the third power device is connected to the connection node of the first capacitor and the second capacitor, and the first end is connected to the first end of the fourth power device; the second end of the fourth power device is connected to the output terminal of the T-type three-level converter unit; each diode is connected in parallel across the two ends of the corresponding power device, wherein the cathode of the diode is connected to the first end of the corresponding power device, and the anode is connected to the second end of the corresponding power device; the first end of the inductor is connected to the voltage output terminal of the T-type three-level converter unit, and the second end is connected to the connection node of the first capacitor and the second capacitor. The T-type three-level commutator unit dynamic characteristic testing circuit and method of this invention features a simple test circuit structure, high efficiency, and comprehensive functions, facilitating automated testing. It allows for testing under different operating conditions within the same circuit without switching inductor positions, simplifying operation. Furthermore, it avoids changes in circuit consistency due to inductor position switching, ensuring high test accuracy. When the inductor enters freewheeling mode, the voltage across the inductor is 0V, replicating actual application conditions and further improving test accuracy. Overcurrent protection is employed to prevent damage to components or circuits when current is excessive. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0078] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A dynamic characteristic testing circuit for a T-type three-level commutator unit, characterized in that, The dynamic characteristic test circuit of the T-type three-level commutator unit includes at least: Charge / discharge control unit, first capacitor, second capacitor, T-type three-level commutator unit and inductor; The charging and discharging control unit provides charging current or a discharging path for the first capacitor and the second capacitor. The upper plate of the first capacitor is connected to the positive output terminal of the charge-discharge control unit, the lower plate of the first capacitor is connected to the upper plate of the second capacitor, and the lower plate of the second capacitor is connected to the negative output terminal of the charge-discharge control unit. The T-type three-level converter unit adjusts the current flow direction and output level through switching timing, and includes a first power device, a second power device, a third power device, a fourth power device, a first diode, a second diode, a third diode, and a fourth diode. The first terminal of the first power device is connected to the positive output terminal of the charge / discharge control unit, and its second terminal is connected to the first terminal of the second power device and serves as the output terminal of the T-type three-level converter unit. The second terminal of the second power device is connected to the negative output terminal of the charge / discharge control unit. The second terminal of the third power device is connected to the connection node between the first capacitor and the second capacitor, and its first terminal is connected to the first terminal of the fourth power device. The second terminal of the fourth power device is connected to the output terminal of the T-type three-level converter unit. Each diode is connected in parallel across the two ends of its corresponding power device, wherein the cathode of the diode is connected to the first terminal of the corresponding power device, and the anode is connected to the second terminal of the corresponding power device. The first end of the inductor is connected to the voltage output terminal of the T-type three-level converter unit, and the second end is connected to the connection node of the first capacitor and the second capacitor; the connection position of the inductor is not changed during the test.

2. The dynamic characteristic test circuit of the T-type three-level commutator unit according to claim 1, characterized in that: The charging and discharging control unit includes a DC power supply, a first switch, and a second switch; the first end of the first switch is connected to the positive terminal of the DC power supply, and the second end is connected to the upper plate of the first capacitor; the first end of the second switch is connected to the second end of the first switch, and the second end is connected to the negative terminal of the DC power supply.

3. The dynamic characteristic test circuit of the T-type three-level commutator unit according to claim 2, characterized in that: The charging and discharging control unit also includes a resistor connected between the second terminal of the second switch and the negative terminal of the DC power supply.

4. The dynamic characteristic test circuit of the T-type three-level commutator unit according to claim 1, characterized in that: The dynamic characteristic test circuit of the T-type three-level converter unit further includes a first overcurrent protection unit and a second overcurrent protection unit. The first overcurrent protection unit is connected between the positive output terminal of the charge and discharge control unit and the upper plate of the first capacitor, and the second overcurrent protection unit is connected between the lower plate of the first capacitor and the upper plate of the second capacitor.

5. The dynamic characteristic test circuit of the T-type three-level commutator unit according to any one of claims 1-4, characterized in that: Each diode can be a body diode or an independent device.

6. A method for testing the dynamic characteristics of a T-type three-level converter unit, implemented using the dynamic characteristic testing circuit of the T-type three-level converter unit as described in any one of claims 1-5, characterized in that, The dynamic characteristic testing method for the T-type three-level converter unit includes at least the following: Tests were conducted under positive voltage and positive current conditions to evaluate the dynamic characteristics of the first power device and the third diode connected in parallel across the third power device. The test was conducted under positive voltage and negative current conditions to evaluate the dynamic characteristics of the third power device and the first diode connected in parallel across the first power device.

7. The dynamic characteristic testing method for the T-type three-level converter unit according to claim 6, characterized in that: The method for evaluating the dynamic characteristics of the first power device and the third diode includes: 11) Turn on the first power device, turn off the second power device and the third power device, and the current flows from the upper plate of the first capacitor through the first power device and the inductor back to the lower plate of the first capacitor; 12) Turn off the first power device and the second power device, turn on the fourth power device, turn on the third diode to enable freewheeling, and the current flows from the second end of the inductor through the third diode and the fourth power device back to the first end of the inductor; 13) Turn on the first power device, turn off the second power device and the third power device, the third diode undergoes reverse recovery, and the current flows from the upper plate of the first capacitor through the first power device and the inductor back to the lower plate of the first capacitor.

8. The dynamic characteristic testing method for the T-type three-level converter unit according to claim 7, characterized in that: The fourth power device in step 11) is turned on or off; the third power device in step 12) is turned on or off; the fourth power device in step 13) is turned on or off.

9. The dynamic characteristic testing method for the T-type three-level converter unit according to claim 6, characterized in that: The method for evaluating the dynamic characteristics of the third power device and the first diode includes: 21) Turn on the second power device, turn off the first power device, the third power device and the fourth power device, and the current flows from the upper plate of the second capacitor through the inductor and the second power device back to the lower plate of the second capacitor; 22) When the second power device and the third power device are turned off, the first diode is turned on to freewheel, and the current flows from the first end of the inductor through the first diode and the first capacitor back to the second end of the inductor; 23) Turn off the first power device and the second power device, turn on the third power device, the first diode undergoes reverse recovery, and the current flows from the first end of the inductor through the fourth diode connected in parallel across the fourth power device and the third power device back to the second end of the inductor.

10. The dynamic characteristic testing method for the T-type three-level converter unit according to claim 9, characterized in that: In step 22), the first power device is turned on or off, and the fourth power device is turned on or off; in step 23), the fourth power device is turned on or off.

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