A MMC sub-module detection circuit

Abstract

The application relates to an MMC sub-module detection circuit which comprises an MMC sub-module loop and an auxiliary detection circuit; the auxiliary detection circuit comprises a relay, a resistor, an inductor and a direct-current voltage source V DC ; P1, P2 and P3 ports are arranged on the MMC sub-module loop, the P1 port is connected with a switch tube S1, the P3 port is connected with a switch tube S2, the P2 port is connected with the switch tube S1 and the switch tube S2, and the two ends of a capacitor are respectively connected with the switch tube S1 and the switch tube S2; the resistor and the inductor are connected in series, the other end of the inductor is connected with the P2 port, the other end of the resistor is respectively connected with the P1 port and the common contact of the relay, the contact 0 of the relay is connected with the negative pole of the direct-current voltage source V DC and the P3 port, and the contact 1 of the relay is connected with the positive pole of the direct-current voltage source V DC . The application can realize the rapid detection of the upper and lower switch tubes in the MMC sub-module and the switching detection through the control of the relay, and the overall circuit control is simple and safe.

Description

Technical Field

[0001] This invention relates to the field of electronic components technology, and in particular to a detection circuit for an MMC submodule. Background Technology

[0002] Modular multilevel converters (MMCs) are key equipment in flexible DC transmission systems. With their modularity, scalability, low harmonic distortion, low control difficulty, and high output voltage waveform quality, they are widely used in new energy power generation and DC distribution network systems.

[0003] The MMC bridge arms employ a submodule cascaded approach, with each bridge arm consisting of N submodules and a series reactor. Two bridge arms in the same phase form a phase unit. Commonly used submodule structures include half-bridge and full-bridge structures. A half-bridge structure is shown below. Figure 1 As shown, it mainly includes one capacitor, two press-fit insulated gate bipolar transistor (IGBT) modules, and peripheral components such as a heat sink, a mechanical switch, a clamping device, and two IGBT drivers. The MMC submodule is bulky, weighing over 400 kg, and its internal components are tightly coupled. Among the factors affecting the reliability of the MMC submodule, the reliability of the switching transistors plays a decisive role; therefore, studying module reliability primarily involves analyzing the reliability of the switching transistors.

[0004] Currently, there are three methods for reliability assessment of MMC submodules: online testing, in-situ testing, and offline testing. Online testing involves synchronous testing of the submodule during MMC module operation, but this method has low practical feasibility. In-situ testing is performed after the MMC module is disconnected from operation, without altering the original circuit structure; this method has limited measurable parameters and is difficult to measure the reliability of the MMC submodule. Offline testing completely disconnects the MMC module from the operating circuit, unaffected by the original circuit; this method has relatively more measurable parameters, but requires disassembly from the circuit system and can only be used as a periodic testing method. Considering practical engineering situations, offline testing is the most commonly used method.

[0005] Existing offline testing methods involve disassembling the entire MMC submodule, performing dual-pulse tests on the IGBT modules within each submodule independently to obtain sufficient parameters for measuring device aging, and then reassembling them. The dual-pulse circuit works by turning off the upper IGBT and driving the lower IGBT with a dual-pulse signal. The falling edge of the first pulse indicates the lower IGBT's turn-off characteristic, and the rising edge indicates its turn-on characteristic. While this method yields a large amount of parameter data, it requires complete disassembly of the MMC submodule, which significantly reduces module reliability during disassembly and reassembly. Furthermore, after long-term operation, dual-pulse testing is commonly used to measure the dynamic characteristics of aged switching transistors in the MMC. Traditional dual-pulse test circuits require disassembling the MMC submodule, which reduces module reliability. The entire testing process is also difficult to operate, incurring significant time and labor costs, making it impractical for routine maintenance.

[0006] Chinese Patent Application No. 202211418547.4 discloses "A Dynamic Characteristic Detection Circuit and Method for an MMC Submodule," which includes a DC power supply, an IGBT half-bridge module, and an inductor. The IGBT half-bridge module includes a first IGBT device and a second IGBT device. One end of the inductor is connected to the collector terminal of the first IGBT device, and the other end of the inductor is connected to the emitter terminal of a third IGBT device in the MMC submodule. The collector of the second IGBT device is connected to the emitter terminal of a fourth IGBT device in the MMC submodule. The MMC submodule includes the third IGBT device, the fourth IGBT device, and a capacitor. The half-bridge circuit formed by connecting the third and fourth IGBT devices in series is connected in parallel with the capacitor. However, the disadvantages of this technical solution are that it requires additional drive circuits for T1 and T2 in the test circuit, making the actual test circuit more complex. Moreover, this technical solution can only test the upper transistor Q1 of the MMC submodule. During discharge, it does not provide a discharge circuit for energy storage components such as capacitors and inductors, making it difficult to guarantee test safety after the test is completed.

[0007] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide an MMC submodule detection circuit that solves the deficiencies of existing detection circuits.

[0009] The objective of this invention is achieved through the following technical solution: an MMC submodule detection circuit, comprising an MMC submodule loop, an auxiliary detection circuit, a drive circuit, and a control circuit. The drive circuit is connected to the MMC submodule loop, and the control circuit is connected to the auxiliary detection circuit. The auxiliary detection circuit includes a relay, a resistor, an inductor, and a DC voltage source V. DC The MMC submodule circuit has three electrical power ports: P1, P2, and P3. Port P1 is connected to the collector of switch S1, port P3 is connected to the emitter of switch S2, and port P2 is connected to the emitter of switch S1 and the collector of switch S2. The two ends of the capacitor are connected to the collector of switch S1 and the emitter of switch S2, respectively.

[0010] The resistor and inductor are connected in series. One end of the inductor is connected to port P2, and the other end of the resistor is connected to port P1 and the common contact of the relay. The relay contact 0 is connected to the DC voltage source V. DC The negative terminal is connected to the P3 port, and contact 1 is connected to the DC voltage source V. DC The positive terminal is connected; the connection state of the relay is controlled by the control circuit to achieve the charging and discharging of the capacitor, so that the device under test is in different test stages.

[0011] The different test stages include a self-heating stage, a multi-pulse test stage, and a discharge stage in sequence. The self-heating stage is the stage in which the device under test heats up by repeatedly charging and discharging the capacitor. The multi-pulse test stage is the stage in which the device under test is driven by a multi-pulse signal.

[0012] During the self-heating stage, when the capacitor is charging, the relay common contact is connected to contact 1. At this time, switch S2 is turned on, switch S1 is turned off, and the DC voltage source V... DC The capacitor is charged, which causes the temperature of the switch S2 of the device under test to rise.

[0013] When the capacitor discharges, the relay's common contact connects with contact 0. At this time, switch S2 is turned on, switch S1 is turned off, the capacitor discharges itself, and the temperature of switch S2 of the device under test rises.

[0014] During the multi-pulse test phase, the relay common contact is connected to contact 0. At this time, switch S2 is turned on and switch S1 is turned off. The driving signal of switch S2 is one or more multi-pulse signals.

[0015] During the discharge phase, the relay common contact is connected to contact 0. At this time, switch S2 is turned on and switch S1 is turned off, and the capacitor and inductor discharge.

[0016] An MMC submodule detection circuit includes an MMC submodule loop, a first auxiliary detection circuit, a second auxiliary detection circuit, a drive circuit, and a control circuit. The drive circuit is connected to the MMC submodule loop, and the control circuit is connected to the first and second auxiliary detection circuits. Three electrical power ports, P1, P2, and P3, are provided on the MMC submodule loop. Port P1 is connected to the collector of switching transistor S1, port P3 is connected to the emitter of switching transistor S2, and port P2 is connected to both the emitter and collector of switching transistor S1. The two ends of a capacitor are connected to the collector of switching transistor S1 and the emitter of switching transistor S2, respectively.

[0017] The first auxiliary detection circuit is connected to three electrical power ports P1, P2 and P3, and the second auxiliary detection circuit is connected to two electrical power ports P1 and P3. The connection status of the first and second auxiliary detection circuits with the MMC submodule circuit is controlled and adjusted by the control circuit to realize rapid detection of different test stages of switching transistors S1 and S2 and switching of the two switching transistors.

[0018] The first auxiliary detection circuit includes a half-bridge structure composed of switching transistors S3 and S4, with a first DC voltage source V connected in parallel across the two ends of the half-bridge structure. DC The center point of the half-bridge structure is connected to contact 1 of relay K1, contact 0 of relay K1 is connected to port P1, and the common contact of relay K1 is connected to port P2 after being connected in series with a resistor and an inductor. Port P3 is connected to the emitter of switching transistor S4 and the first DC voltage source V. DC The negative terminal connection.

[0019] The second auxiliary detection circuit includes a relay K2 and a circuit breaker K3. One end of the circuit breaker K3 is connected to port P1, and the other end is connected to the common contact of the relay K2. Contact 1 of the relay K2 is connected to the second DC voltage source V. DC The positive terminal of relay K2 is connected to a resistor; the P3 port is connected to the resistor and the second DC voltage source V. DC The negative terminal connection.

[0020] When testing the switching transistor S1, the common contact of relay K1 is connected to contact 1, and the second auxiliary detection circuit is disconnected from the MMC submodule circuit.

[0021] The self-heating stage is achieved by repeatedly charging and discharging the capacitor. When the capacitor is charging, switch S3 is turned on, while switches S1, S2, and S4 are turned off. Before the capacitor is discharged, the inductor is discharged. When the inductor is discharging, switch S2 is turned on, while switches S1, S3, and S4 are turned off. When the capacitor is discharging, switch S1 is turned on, while switches S2, S3, and S4 are turned off.

[0022] During the multi-pulse test phase, switch S1 is turned on, while switches S2, S3, and S4 are turned off. The driving signal for switch S1 is one or more multi-pulse signals.

[0023] During the discharge phase, switch S1 is turned on, while switches S2, S3, and S4 are turned off.

[0024] When testing switch S2, the first auxiliary detection circuit and the MMC submodule circuit are in port state, and the circuit breaker K3 is in closed state;

[0025] The self-heating stage is achieved by repeatedly charging and discharging the capacitor. When the capacitor is charging, the common contact of relay K2 is connected to contact 1, and when the capacitor is discharging, the common contact of relay K2 is connected to contact 0.

[0026] During the multi-pulse test phase, the common contact of relay K2 is connected to contact 0, and the drive signal for switching transistor S2 is one or more multi-pulse signals;

[0027] During the discharge phase, the common contact of relay K2 is connected to contact 0.

[0028] The present invention has the following advantages: an MMC submodule detection circuit, which can realize the rapid detection and switching detection of the upper and lower switching transistors in the MMC submodule by controlling the relay, and the overall circuit control is simple and highly safe. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of an existing half-bridge MMC submodule;

[0030] Figure 2 This is a schematic diagram of the circuit structure of Embodiment 1 of the present invention;

[0031] Figure 3 This is a timing diagram showing the drive voltage of the switching transistor and the state of the relay.

[0032] Figure 4 A circuit diagram illustrating the capacitor charging process;

[0033] Figure 5 This is a circuit diagram illustrating the capacitor discharge process.

[0034] Figure 6 This is a schematic diagram of the circuit structure of Embodiment 2 of the present invention;

[0035] Figure 7 A schematic diagram of the drive voltage of each switching transistor when detecting switching transistor S1;

[0036] Figure 8 A circuit diagram for detecting the capacitor charging process when switching transistor S1 is used;

[0037] Figure 9 A circuit diagram for detecting the inductor discharge process when switching transistor S1 is used;

[0038] Figure 10 A circuit diagram for detecting the capacitor discharge process when switching transistor S1 is used;

[0039] Figure 11 A circuit diagram for detecting the capacitor charging process when switching transistor S2 is activated;

[0040] Figure 12 A circuit diagram for detecting the capacitor discharge process when switching transistor S2 is used. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of this application provided below with reference to the accompanying drawings is not intended to limit the scope of protection of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The present invention will be further described below with reference to the accompanying drawings.

[0042] Example 1

[0043] like Figure 2 As shown, this embodiment includes an existing IGBT drive circuit and control circuit, as well as an MMC submodule loop and an auxiliary detection circuit. The drive circuit is connected to the MMC submodule loop, and the control circuit is connected to the auxiliary detection circuit. The auxiliary detection circuit consists of a single-pole double-throw relay (relay K), a resistor R, an inductor L, and a DC voltage source V. DC The circuit consists of the following components: a resistor and an inductor are connected in series and then in parallel between power ports P1 and P2 of the submodule; the common terminal of relay K is connected to power port P1; contact 0 (the contact when K=0 is in switch contact) is connected to power port P3 via a wire; and contact 1 (the contact when K=1 is in switch contact) is connected to the DC voltage source V via a wire. DC Connected.

[0044] The test is divided into four stages: initial stage, self-heating stage, multi-pulse test stage, and discharge stage, such as... Figure 3As shown in the diagram. The initial stage (T1) refers to the complete discharge of the capacitors in the module, the mechanical pressure of the module fixture within the rated standard range, the ambient temperature set to room temperature, and all IGBT drive voltages at a low level, meaning the IGBTs are all in the off state. The self-heating stage (T2) refers to the device self-heating, achieved by repeatedly charging and discharging the capacitors. The multi-pulse test stage (T3) refers to the drive of the device under test being a multi-pulse signal. The discharge stage (T4) refers to the complete discharge of the capacitors and inductors after the multi-pulse test.

[0045] The charging process of the capacitor of the device under test is achieved by setting relay K to contact 1, turning on switch S2, and turning off switch S1. The circuit operation state is as follows: Figure 4 As shown. During the capacitor discharge process, relay K is set to contact 0, switching transistor S2 is turned on, and switching transistor S1 is turned off. The circuit operation state is as follows. Figure 5 As shown. The characteristic of the multi-pulse test phase is that the drive signal for switch S2 is a multi-pulse signal, while the states of the other switches are consistent with the capacitor discharge process.

[0046] The self-heating stage is achieved by repeatedly charging and discharging capacitor C. During the charging of capacitor C, contact 1 of relay K is connected to the DC voltage source V. DC When capacitor C discharges, contact 0 of relay K is connected to power port P3.

[0047] During the double-pulse test phase, contact 0 of relay K is connected to power port P3, switch S1 is turned off, and the drive signal for switch S2 is one or more double-pulse signals.

[0048] During the discharge phase, contact 0 of relay K is connected to power port 3P3.

[0049] Example 2

[0050] like Figure 6 As shown, this embodiment includes an existing IGBT drive circuit and control circuit, as well as an MMC submodule loop, a first auxiliary detection circuit and a second auxiliary detection circuit. The drive circuit is connected to the MMC submodule loop, and the control circuit is connected to the first auxiliary detection circuit and the second auxiliary detection circuit.

[0051] The first auxiliary detection circuit includes two switching transistors (S3 and S4), a single-pole double-throw relay (relay K1), a resistor R1, an inductor L, and a DC voltage source V. DC The second auxiliary detection circuit consists of a circuit breaker K3, a single-pole double-throw relay (relay K2), a resistor R2, and a DC voltage source V. DC It consists of, etc.

[0052] Switches S3 and S4 form a half-bridge structure, with a DC voltage source V connected in parallel across the half-bridge. DCThe center point of the half-bridge is connected to the power port P1. The resistor and inductor are connected in series and then in parallel between the power ports P1 and P2. The common contact of the relay K1 is connected to the resistor. Contact 0 (K1=0) is connected to the power port P1, and contact 1 (K=1) is connected to the center point of the half-bridge.

[0053] The switching of the tested object is achieved through two relays K1 and K2 and a circuit breaker K3. The corresponding truth table is shown in Table 1, where "x" represents any switching state.

[0054] Table 1. Switch Truth Table

[0055] 1 x 0 <![CDATA[Detection S1]]> 0 x 1 <![CDATA[Detection S2]]> 1 x 1 Not allowed 0 x 0 invalid

[0056] The testing of the device under test (DUT) switch S1 (Switch S2 is the same as S1) is divided into four stages: initial stage, self-heating stage, multi-pulse test stage, and discharge stage. Figure 7 As shown in the diagram. The initial stage (T1) refers to the complete discharge of the capacitors in the module, the mechanical pressure of the module fixture within the rated standard range, the ambient temperature set to room temperature, and all IGBT drive voltages at a low level, meaning the IGBTs are all in the off state. The self-heating stage (T2) refers to the device self-heating, achieved by repeatedly charging and discharging the capacitors. The multi-pulse test stage (T3) refers to the drive of the device under test being a multi-pulse signal. The discharge stage (T4) refers to the complete discharge of the capacitors and inductors after the multi-pulse test.

[0057] When testing switch S1, the common contact of relay K1 is connected to contact 1, and circuit breaker K3 is in the open state;

[0058] like Figure 8 As shown, the self-heating stage is achieved by repeatedly charging and discharging the capacitor. During capacitor charging, switch S3 is turned on, while switches S1, S2, and S4 are turned off. Figure 9 As shown, the inductor is discharged before the capacitor. During inductor discharge, switch S2 is turned on, while switches S1, S3, and S4 are turned off. Figure 10 As shown, when the capacitor discharges, switch S1 is turned on, while switches S2, S3 and S4 are turned off.

[0059] During the multi-pulse test phase, switch S1 is turned on, while switches S2, S3, and S4 are turned off. The driving signal for switch S1 is one or more multi-pulse signals.

[0060] During the discharge phase, switch S1 is turned on, while switches S2, S3, and S4 are turned off.

[0061] When testing switch S2, the common contact of relay K1 is connected to contact 0, and circuit breaker K3 is in the closed state;

[0062] like Figure 11 As shown, the self-heating stage is achieved by repeatedly charging and discharging the capacitor. During capacitor charging, the common contact of relay K2 is connected to contact 1, as shown below. Figure 12 As shown, when the capacitor discharges, the common contact of relay K2 is connected to contact 0;

[0063] During the multi-pulse test phase, the common contact of relay K2 is connected to contact 0, and the drive signal for switching transistor S2 is one or more multi-pulse signals;

[0064] During the discharge phase, the common contact of relay K2 is connected to contact 0.

[0065] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. An MMC submodule detection circuit, comprising an MMC submodule circuit, characterized in that: It also includes a first auxiliary detection circuit, a second auxiliary detection circuit, a drive circuit, and a control circuit. The drive circuit is connected to the MMC submodule loop, and the control circuit is connected to the first auxiliary detection circuit and the second auxiliary detection circuit. Three electrical power ports, P1, P2, and P3, are provided on the MMC submodule loop. Port P1 is connected to the collector of switch S1, port P3 is connected to the emitter of switch S2, port P2 is connected to the emitter of switch S1 and the collector of switch S2, and the two ends of the capacitor are connected to the collector of switch S1 and the emitter of switch S2, respectively. The first auxiliary detection circuit is connected to three electrical power ports P1, P2 and P3, and the second auxiliary detection circuit is connected to two electrical power ports P1 and P3. The connection status of the first and second auxiliary detection circuits with the MMC submodule circuit is controlled and adjusted by the control circuit to realize rapid detection of different test stages of switching transistors S1 and S2 and switching of the two switching transistors. The first auxiliary detection circuit includes a half-bridge structure composed of switching transistors S3 and S4, with a first DC voltage source V connected in parallel across the two ends of the half-bridge structure. DC The center point of the half-bridge structure is connected to contact 1 of relay K1, contact 0 of relay K1 is connected to port P1, and the common contact of relay K1 is connected to port P2 after being connected in series with a resistor and an inductor. Port P3 is connected to the emitter of switching transistor S4 and the first DC voltage source V. DC The negative terminal connection; The second auxiliary detection circuit includes a relay K2 and a circuit breaker K3. One end of the circuit breaker K3 is connected to port P1, and the other end is connected to the common contact of the relay K2. Contact 1 of the relay K2 is connected to the second DC voltage source V. DC The positive terminal of relay K2 is connected to a resistor; the P3 port is connected to the resistor and the second DC voltage source V. DC The negative terminal connection.

2. The MMC submodule detection circuit according to claim 1, comprising an MMC submodule circuit, characterized in that: When testing the switching transistor S1, the common contact of relay K1 is connected to contact 1, and the second auxiliary detection circuit is disconnected from the MMC submodule circuit. The self-heating stage is achieved by repeatedly charging and discharging the capacitor. When the capacitor is charging, switch S3 is turned on, while switches S1, S2, and S4 are turned off. Before the capacitor is discharged, the inductor is discharged. When the inductor is discharging, switch S2 is turned on, while switches S1, S3, and S4 are turned off. When the capacitor is discharging, switch S1 is turned on, while switches S2, S3, and S4 are turned off. During the multi-pulse test phase, switch S1 is turned on, while switches S2, S3, and S4 are turned off. The driving signal for switch S1 is one or more multi-pulse signals. During the discharge phase, switch S1 is turned on, while switches S2, S3, and S4 are turned off.

3. The MMC submodule detection circuit according to claim 1, comprising an MMC submodule circuit, characterized in that: When testing switch S2, the first auxiliary detection circuit and the MMC submodule circuit are in port state, and the circuit breaker K3 is in closed state; The self-heating stage is achieved by repeatedly charging and discharging the capacitor. When the capacitor is charging, the common contact of relay K2 is connected to contact 1, and when the capacitor is discharging, the common contact of relay K2 is connected to contact 0. During the multi-pulse test phase, the common contact of relay K2 is connected to contact 0, and the drive signal for switching transistor S2 is one or more multi-pulse signals; During the discharge phase, the common contact of relay K2 is connected to contact 0.

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