Modular multi-level converter submodule parallel thyristor testing device and method

Abstract

The embodiment of the present invention relates to a modular multi-level converter submodule parallel thyristor test device and method, the device includes a power supply unit, an energy storage unit, a full-bridge conversion unit, a sampling unit, a current limiting unit and a control unit; the full-bridge conversion unit is connected to the power supply unit through the energy storage unit, converts the voltage output by the power supply unit, and outputs the converted voltage from the voltage output port; the sampling unit input end is connected to the voltage output port, and the output end is connected to the positive port and negative port of the submodule through the current limiting unit; the thyristor is connected in parallel between the positive port and the negative port of the submodule; the control unit is connected to the submodule to control the submodule. The technical solution of the embodiment of the present invention can solve the existing technical problems without measuring the thyristor current; and there is no need to disassemble the submodule housing or electrical wiring, and the integrity of the submodule is not destroyed during the test.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of power electronics technology, and in particular to a modular multi-level converter sub-module parallel thyristor testing device and method. Background Art

[0002] Modular multilevel converter technology has become the mainstream topology for flexible DC engineering construction. The commonly used half-bridge submodule topology structures in flexible DC engineering are as follows: Figure 1 As shown, it usually includes an upper switch tube and a lower switch tube connected in a half-bridge structure. For special working conditions such as DC faults in the system, the lower switch tube of the submodule will be connected in parallel with a thyristor. When it is detected that the bridge arm current of the MMC exceeds the set value, the valve control sends a submodule thyristor opening instruction, and the current of the anti-parallel diode of the lower switch tube is shared by the thyristor to protect the safety of the submodule.

[0003] The existing sub-module parallel thyristor turn-on test method of thyristor generally adopts the current loop to directly measure the current of the thyristor, which has limitations in the specific implementation of the project. First, the method of using the current loop to measure the turn-on of the thyristor requires the configuration of an oscilloscope or an analytical device, and the overall equipment is large and inconvenient to carry; secondly, the sub-module adopts a metal shell for electromagnetic shielding, and the sub-module shell needs to be removed before the current loop can be put on the thyristor shell, and the test destroys the integrity of the sub-module; finally, the sub-module IGBT and thyristor adopt the crimping technology, and the device diameter increases with the increase of the current capacity, the degree of compactness is improved, and the spatial distance between the thyristor and the adjacent electrical parts is greatly reduced. The solution of directly putting the current loop on the thyristor can no longer be implemented. Therefore, a new sub-module parallel thyristor test method is urgently needed to realize the turn-on test of the sub-module parallel thyristor under the premise of ensuring the integrity of the sub-module. Summary of the invention

[0004] Based on the above situation of the prior art, the purpose of the embodiments of the present invention is to provide a modular multi-level converter sub-module parallel thyristor testing device and method, which can realize the turn-on test of the sub-module parallel thyristors while ensuring the integrity of the sub-module.

[0005] To achieve the above object, according to one aspect of the present invention, a modular multi-level converter submodule parallel thyristor test device is provided, comprising: a power supply unit, an energy storage unit, a full-bridge conversion unit, a sampling unit, a current limiting unit and a control unit;

[0006] The full-bridge conversion unit is connected to the power supply unit via the energy storage unit, converts the voltage output by the power supply unit, and outputs the converted voltage from the voltage output port;

[0007] The sampling unit input end is connected to the voltage output port, and the output end is connected to the positive port and the negative port of the submodule through the current limiting unit;

[0008] A thyristor is connected in parallel between the positive port and the negative port of the submodule;

[0009] The control unit is connected to the submodules to control the submodules.

[0010] Further, the sampling unit includes a first diode D1, a second capacitor C2, a discharge loop and a voltage sampling circuit;

[0011] The anode of the first diode D1 is connected to one end of the voltage output port, the cathode of the first diode D1 is connected to one end of the second capacitor C2, and the other end of the second capacitor C2 is connected to the other end of the voltage output port and the positive port of the submodule;

[0012] The second capacitor C2 is connected in parallel with the discharge circuit;

[0013] The voltage sampling circuit collects the forward voltage of the second capacitor C2, where the forward voltage refers to the end of the second capacitor C2 connected to the cathode of the first diode D1.

[0014] Furthermore, the power supply unit includes a DC voltage source E, a current limiting resistor R1 and a relay K1. The positive electrode of the DC voltage source E is connected in series with the current limiting resistor R1 and then connected to one end of the relay K1.

[0015] Furthermore, the energy storage unit includes an energy storage capacitor C1 and a current limiting inductor L connected in series.

[0016] Further, the current limiting unit includes a second diode D2 and a third resistor R3;

[0017] The second diode D2 and the third resistor R3 are connected in parallel between the anode of the first diode D1 and the negative port of the submodule.

[0018] Further, the full-bridge conversion unit includes a first IGBT, a second IGBT, a third IGBT and a fourth IGBT;

[0019] When the first IGBT and the fourth IGBT are turned on, the positive electrode of the energy storage capacitor C1 is connected to the positive port of the submodule through the current limiting inductor L;

[0020] When the second IGBT and the third IGBT are turned on, the positive electrode of the energy storage capacitor C1 is connected to the sub-negative module port through the current limiting unit via the current limiting inductor L.

[0021] According to another aspect of the present invention, there is provided a test method for the modular multilevel converter submodule parallel thyristor test device as described in the first aspect of the present invention, comprising the steps of:

[0022] Detecting the forward voltage of the second capacitor C2 when no thyristor turn-on instruction is issued;

[0023] Detecting the forward voltage of the second capacitor C2 when the thyristor turn-on instruction is issued;

[0024] Determine whether the thyristor is turned on.

[0025] Further, the detecting of the capacitor voltage when no thyristor turn-on instruction is issued includes:

[0026] Close relay K1 to charge energy storage capacitor C1, and disconnect relay K1 after charging is completed;

[0027] Send a submodule lower tube conduction instruction to make the voltage between the positive port and the negative port of the submodule zero;

[0028] The second IGBT and the third IGBT opening instructions are issued, and the maximum voltage Uc1 of the capacitor collected by the voltage sampling circuit when the energy storage capacitor C1 is discharged through the lower tube anti-parallel diode is recorded.

[0029] Further, the detecting of the capacitor voltage under the thyristor turn-on instruction includes:

[0030] When the second and third IGBT turn-on instructions are issued, the thyristor turn-on instruction is issued, and the maximum voltage Uc2 of the capacitor collected by the voltage sampling circuit when the energy storage capacitor C1 is discharged through the lower tube anti-parallel diode and the thyristor is recorded.

[0031] Further, the determining whether the thyristor is turned on includes:

[0032] If Uc1-Uc2≥ΔU, the thyristor is turned on;

[0033] Otherwise, the thyristor is not turned on;

[0034] Among them, ΔU is the preset threshold.

[0035] In summary, the embodiment of the present invention provides a modular multi-level converter submodule parallel thyristor test device and method, the device includes a power supply unit, an energy storage unit, a full-bridge conversion unit, a sampling unit, a current limiting unit and a control unit; the full-bridge conversion unit is connected to the power supply unit through the energy storage unit, converts the voltage output by the power supply unit, and outputs the converted voltage from the voltage output port; the sampling unit input end is connected to the voltage output port, and the output end is connected to the positive port and the negative port of the submodule through the current limiting unit; the thyristor is connected in parallel between the positive port and the negative port of the submodule; the control unit connects the submodule to control the submodule. The technical solution of the embodiment of the present invention has few submodule wiring, simple control, no need to set a current sensor, no need to measure the thyristor current, and can solve the existing technical problems; and there is no need to disassemble the submodule housing or electrical wiring, the integrity of the submodule is not destroyed during the test, and the safety of equipment and personnel is ensured. Under the premise of ensuring the integrity of the submodule, the submodule parallel thyristor opening test can be realized, which solves the technical problem that the submodule parallel thyristor opening cannot be accurately tested without a current sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the topological structure of a half-bridge submodule commonly used in flexible DC engineering;

[0037] Figure 2 1 is a schematic diagram of the circuit structure of a modular multi-level converter sub-module parallel thyristor testing device provided by an embodiment of the present invention;

[0038] Figure 3 is a flow chart of a method for testing parallel thyristors of modular multilevel converter submodules provided by an embodiment of the present invention;

[0039] Figure 4 It is a schematic diagram of the maximum voltage of the sampling unit capacitor when the thyristor is turned on and off, obtained by using the test device and method provided by the embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0041] The technical solution of the embodiment of the present invention is described in detail below with reference to the accompanying drawings. The embodiment of the present invention provides a modular multi-level converter sub-module parallel thyristor test device, Figure 2 The circuit structure diagram of the device is shown in FIG. Figure 2As shown, the test device includes: a power supply unit 1, an energy storage unit 2, a full-bridge conversion unit 3, a sampling unit 4, a current limiting unit 5 and a control unit 6.

[0042] The power supply unit 1 comprises a DC voltage source E, a current limiting resistor R1 and a relay K1. The positive electrode of the DC voltage source E is connected in series with the current limiting resistor R1 and then connected to one end of the relay K1.

[0043] The energy storage unit 2 includes an energy storage capacitor C1 and a current limiting inductor L connected in series, one end of the current limiting inductor L is connected to the other end of the relay K1, the other end of the current limiting inductor L is connected to one end of the energy storage capacitor C1, and the other end of the energy storage capacitor C1 is connected to the negative electrode of the DC voltage source E.

[0044] The full-bridge conversion unit 3 includes a first IGBT T1, a second IGBT T2, a third IGBT T3 and a fourth IGBT T4. The first IGBT T1 and the second IGBT T2 constitute a first bridge arm of the full-bridge conversion unit 3, and the third IGBT T3 and the fourth IGBT T4 constitute a second bridge arm of the full-bridge conversion unit 3. After the first bridge arm and the second bridge arm are connected in parallel, one end is connected to one end of the current limiting inductor L, and the other end is connected to the other end of the energy storage capacitor C1. The full-bridge conversion unit 3 is connected to the power supply unit 1 through the energy storage unit 2, converts the voltage output by the power supply unit 1, and outputs the converted voltage from the voltage output port. The connection point of the first IGBT T1 and the second IGBT T2 and the connection point of the third IGBT T3 and the fourth IGBT T4 constitute the voltage output port of the full-bridge conversion unit 3. When the first IGBT and the fourth IGBT are turned on, the positive electrode of the energy storage capacitor C1 is connected to the positive port of the sub-module through the current limiting inductor L; when the second IGBT and the third IGBT are turned on, the positive electrode of the energy storage capacitor C1 is connected to the negative sub-module port through the current limiting inductor L through the current limiting unit.

[0045] The input end of the sampling unit 4 is connected to the voltage output port, and the output end is connected to the positive port and negative port of the submodule through the current limiting unit 5. The sampling unit 4 includes a first diode D1, a second capacitor C2, a discharge circuit and a voltage sampling circuit. After the second capacitor C2 is connected in parallel with the discharge circuit, it is connected to the voltage output port. The anode of the first diode D1 is connected to one end of the voltage output port, the cathode of the first diode D1 is connected to one end of the second capacitor C2, and the other end of the second capacitor C2 is connected to the other end of the voltage output port and the positive port of the submodule; the voltage sampling circuit collects the forward voltage of the second capacitor C2, and the forward refers to the end of the second capacitor C2 connected to the cathode of the first diode D1. Among them, the discharge circuit includes a discharge resistor R2 and a discharge relay K2 connected in series, and the voltage sampling circuit can be a voltage transformer, a voltmeter, or other measuring elements or circuits that can sample capacitor voltage.

[0046] The current limiting unit 5 includes a second diode D2 and a third resistor R3; the second diode D2 and the third resistor R3 are connected in parallel between the anode of the first diode D1 and the negative port of the submodule.

[0047] The control unit 6 is connected to the submodule to control the submodule. The control unit 6 includes a storage unit, a control board and a communication interface unit. The storage unit is used to store the sampled capacitor voltage. The control board is used for submodule control and data processing. The communication interface unit is used for submodule communication and host computer communication. The communication interface unit is connected to the submodule control board through a pair of optical fibers. The sending end of the communication interface unit is connected to the receiving end of the control board, and the receiving end of the communication interface unit is connected to the sending end of the control board.

[0048] The thyristor is connected in parallel between the positive port and the negative port of the modular multi-level converter submodule. The circuit structure is as shown above. Figure 1 As shown, the submodules are controlled by control signals from the control unit 6 to perform the test.

[0049] An embodiment of the present invention further provides a test method applied to the modular multi-level converter sub-module parallel thyristor test device as described in the above embodiment of the present invention, Figure 3 The flowchart of the test method is shown in FIG. 1 , and the method comprises the following steps:

[0050] Step S1: Connect the test circuit. A pair of communication optical fibers is connected between the test device and the submodule control board, and a pair of electrical wires is connected between the test device and the submodule port.

[0051] Step S2: The submodule control board is powered on. The control unit 6 controls the DC voltage source E to output the voltage U1, and turns on the first IGBT T1 and the fourth IGBT T4, closes the relay K1, and charges the submodule capacitor through the submodule port, so that the submodule capacitor voltage is much greater than the power-on voltage of the submodule internal energy board, and the submodule control board is powered on. The control unit 6 reads the software version number uploaded by the submodule, the submodule capacitor voltage and status information, etc. through the communication optical fiber, and determines whether the communication with the submodule is successful.

[0052] Step S3: Detect the capacitor voltage when no thyristor opening instruction is issued. The control unit 6 controls the DC voltage source E to output voltage U2, and U2 < U1; the control unit 6 closes the relay K1 to charge the energy storage capacitor C1, and disconnects the relay K1 after charging is completed; the control unit 6 issues a switch tube conduction instruction under the submodule to make the submodule port voltage zero; the control unit 6 issues a second IGBT T2 and a third IGBT T3 opening instruction of the full-bridge conversion unit 3, and the energy storage capacitor C1, the current limiting inductor L, the second diode D2, and the anti-parallel diode of the switch tube under the submodule form a discharge loop. The storage unit records the uploaded second capacitor C2 voltage for a continuous Δt time, and calculates the maximum voltage Uc1. The control unit 6 closes the discharge relay K2 to discharge the second capacitor C2.

[0053] Step S4: Detect the capacitor voltage under the thyristor opening instruction. The control unit 6 controls the DC voltage source E to output the voltage U2, and U2 < U1; the control unit 6 closes the relay K1 to charge the energy storage capacitor, and disconnects the relay K1 after the charging is completed; the control unit 6 issues the switch tube conduction instruction under the submodule to make the submodule port voltage zero; the control unit 6 issues the thyristor opening instruction, and at the same time issues the second IGBT T2 and the third IGBT T3 opening instructions of the full-bridge conversion unit 3, and the energy storage capacitor C1, the current limiting inductor L, the second diode D2, the anti-parallel diode of the switch tube under the submodule and the thyristor form a discharge circuit. The storage unit records the uploaded second capacitor C2 voltage for a continuous Δt time, and calculates the maximum voltage Uc2. The control unit 6 closes the discharge relay K2 to discharge the second capacitor C2.

[0054] Step S5: Determine whether the thyristor is turned on. The control unit 6 compares the maximum voltages recorded twice and outputs the test result to the background. If Uc1-Uc2≥ΔU, the thyristor is turned on. Otherwise, the thyristor is not turned on.

[0055] ΔU can take a value of 0.3V.

[0056] Figure 4 The maximum voltage of the sampling unit capacitor when the thyristor is not turned on and turned on is shown in the figure using the test device and method provided by the embodiment of the present invention. When the thyristor is not turned on, the capacitor voltage is 5.4 V, and when the thyristor is turned on, the capacitor voltage is 4.5 V. According to the judgment method of step S5, the thyristor tested in this test can be turned on reliably.

[0057] In summary, the embodiment of the present invention relates to a modular multi-level converter submodule parallel thyristor test device and method, the device includes a power supply unit, an energy storage unit, a full-bridge conversion unit, a sampling unit, a current limiting unit and a control unit; the full-bridge conversion unit is connected to the power supply unit through the energy storage unit, converts the voltage output by the power supply unit, and outputs the converted voltage from the voltage output port; the sampling unit input end is connected to the voltage output port, and the output end is connected to the positive port and the negative port of the submodule through the current limiting unit; the thyristor is connected in parallel between the positive port and the negative port of the submodule; the control unit is connected to the submodule to control the submodule. The technical solution of the embodiment of the present invention has few submodule wiring, simple control, no need to set a current sensor, no need to measure the thyristor current, and can solve the existing technical problems; and there is no need to disassemble the submodule housing or electrical wiring, the integrity of the submodule is not destroyed during the test, and the safety of equipment and personnel is ensured. Under the premise of ensuring the integrity of the submodule, the submodule parallel thyristor opening test can be realized, which solves the technical problem that the submodule parallel thyristor opening cannot be accurately tested without a current sensor.

[0058] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A test method for a parallel thyristor test device for a modular multi-level converter submodule, characterized in that: The modular multi-level converter submodule parallel thyristor test device comprises: a power supply unit, an energy storage unit, a full-bridge conversion unit, a sampling unit, a current limiting unit and a control unit; The full-bridge conversion unit is connected to the power supply unit via the energy storage unit, converts the voltage output by the power supply unit, and outputs the converted voltage from the voltage output port; The sampling unit input end is connected to the voltage output port, and the output end is connected to the positive port and the negative port of the submodule through the current limiting unit; the sampling unit includes a first diode (D1), a second capacitor (C2), a discharge loop and a voltage sampling circuit; A thyristor is connected in parallel between the positive port and the negative port of the submodule; The control unit is connected to the submodule to control the submodule; the method comprises the steps of: Detecting the forward voltage of the second capacitor (C2) when no thyristor turn-on instruction is issued; Detecting the forward voltage of the second capacitor (C2) when issuing the thyristor turn-on command; Determine whether the thyristor is turned on.

2. The testing method according to claim 1, characterized in that: The anode of the first diode (D1) is connected to one end of the voltage output port, the cathode of the first diode (D1) is connected to one end of the second capacitor (C2), and the other end of the second capacitor (C2) is connected to the other end of the voltage output port and the positive port of the submodule; The second capacitor (C2) is connected in parallel with the discharge circuit; The voltage sampling circuit collects the forward voltage of the second capacitor (C2), and the forward voltage refers to the end of the second capacitor (C2) connected to the cathode of the first diode (D1).

3. The testing method according to claim 2, characterized in that: The power supply unit comprises a DC voltage source (E), a current limiting resistor (R1) and a relay (K1); the positive electrode of the DC voltage source (E) is connected in series with the current limiting resistor (R1) and then connected to one end of the relay (K1).

4. The testing method according to claim 3, characterized in that: The energy storage unit comprises an energy storage capacitor (C1) and a current limiting inductor (L) connected in series.

5. The testing method according to claim 4, characterized in that: The current limiting unit includes a second diode (D2) and a third resistor (R3); The second diode (D2) and the third resistor (R3) are connected in parallel between the anode of the first diode (D1) and the negative terminal of the submodule.

6. The testing method according to claim 5, characterized in that: The full-bridge conversion unit includes a first IGBT, a second IGBT, a third IGBT and a fourth IGBT; When the first IGBT and the fourth IGBT are turned on, the positive electrode of the energy storage capacitor (C1) is connected to the positive port of the submodule through the current limiting inductor (L); When the second IGBT and the third IGBT are turned on, the positive electrode of the energy storage capacitor (C1) is connected to the sub-negative module port through the current limiting unit via the current limiting inductor (L).

7. The testing method according to claim 1, characterized in that: The detecting of the capacitor voltage when no thyristor turn-on instruction is issued comprises: Close the relay (K1) to charge the energy storage capacitor (C1), and disconnect the relay (K1) after charging is completed; Send a submodule lower tube conduction instruction to make the voltage between the positive port and the negative port of the submodule zero; The second IGBT and the third IGBT opening instructions are issued, and the maximum voltage Uc1 of the capacitor collected by the voltage sampling circuit when the energy storage capacitor (C1) is discharged through the lower tube anti-parallel diode is recorded.

8. The testing method according to claim 7, characterized in that: The detecting of the capacitor voltage under the thyristor turn-on instruction includes: When issuing the second IGBT and the third IGBT opening instructions, issuing the thyristor opening instructions, and recording the maximum voltage Uc2 of the capacitor collected by the voltage sampling circuit when the energy storage capacitor (C1) is discharged through the lower tube anti-parallel diode and the thyristor.

9. The testing method according to claim 8, characterized in that: The step of judging whether the thyristor is turned on comprises: If Uc1-Uc2≥ΔU, the thyristor is turned on; Otherwise, the thyristor is not turned on; Among them, ΔU is the preset threshold.

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