Star-delta topology conversion circuit and star-delta topology conversion system

Abstract

The invention relates to a star-delta topology conversion circuit and a star-delta topology conversion system, the star-delta topology conversion circuit realizes conversion of topological structures of a converter bridge arm in a high-voltage cascade energy storage converter by conducting a star connection isolation switch or a delta connection isolation switch, the operation is convenient, the conversion time between the two topological structures is reduced, and the conversion efficiency is improved. The operation efficiency of topological structure conversion is improved, meanwhile, state interlocking is arranged between the star connection disconnecting switch and the angle connection disconnecting switch, it is avoided that due to the fact that the star connection disconnecting switch and the angle connection disconnecting switch are conducted at the same time, operation errors occur in the topological structure conversion process, and the risk of misoperation is reduced. According to the star-angle topology conversion system, the star-connection isolation switch and the angle-connection isolation switch are arranged on the star-connection isolation switch cabinet and the angle-connection isolation switch cabinet respectively, the star-connection isolation switch cabinet and the angle-connection isolation switch cabinet are connected through the busbar, cable use is reduced, field arrangement is simple and tidy, and Y-conversion can be achieved by operating the switches on the electrical cabinet.

Description

Technical Field

[0001] This invention relates to the field of electrical technology testing, specifically to a star-delta topology conversion circuit and a star-delta topology conversion system. Background Technology

[0002] The construction of an electrical test laboratory for high-voltage cascaded energy storage converters involves using primary electrical equipment as test subjects. The topology is changed according to test requirements to verify different functions. The functional and performance verification tests for high-voltage cascaded energy storage PCS (Power Conversion System) are numerous. Depending on the energy storage capacity configured for different projects, different topologies, such as star or delta connections, need to be selected. These two topologies have different characteristics: star connection can only achieve three-phase regulation and cannot achieve phase-by-phase regulation, while delta connection can achieve phase-by-phase regulation and asymmetrical regulation. Delta topologies may generate zero-sequence current, affecting control stability. To examine the control performance of PCS with different topologies, the test device needs to have the ability to switch between star and delta topologies. The usual star-delta connection conversion involves manual cable replacement, which is labor-intensive and prone to connection errors, potentially leading to electrical accidents. Furthermore, the large number of cables on site results in messy wiring, affecting the overall layout of the test laboratory. Therefore, a wiring and layout method that allows for rapid Y-Δ conversion needs to be considered. Summary of the Invention

[0003] To address the problem that existing electrical testing methods involve manually replacing cable connections for star-to-delta topology conversion, which is labor-intensive, prone to errors, and potentially leads to electrical accidents, this invention proposes a star-to-delta topology conversion circuit. The circuit includes: a multi-phase star disconnect switch, a multi-phase delta disconnect switch, and a high-voltage cascaded energy storage converter. The high-voltage cascaded energy storage converter includes: multi-phase converter arms. Each phase of the converter arm is connected via a star disconnect switch to form a star topology, and each phase of the converter arm is sequentially connected end-to-end via a delta disconnect switch to form a delta topology. A state interlock is provided between the multi-phase star disconnect switch and the multi-phase delta disconnect switch to prevent simultaneous conduction of both switches. When the multi-phase star-connected disconnect switch is turned on, the converter bridge arms in the high-voltage cascaded energy storage converter are star-connected; when the multi-phase delta-connected disconnect switch is turned on, the converter bridge arms in the high-voltage cascaded energy storage converter are delta-connected.

[0004] Optionally, the circuit further includes: a plurality of series reactors; each phase of the converter bridge arm is connected to the AC power grid through one of the series reactors.

[0005] Optionally, the circuit further includes: multiple starting resistors and multi-phase bypass switches; each of the series reactors is connected to the AC power grid via one phase of the bypass switch, and each phase of the bypass switch is connected in parallel with one of the starting resistors.

[0006] Optionally, when the high-voltage cascaded energy storage converter is in a charging state and the voltage of the DC capacitor in the high-voltage cascaded energy storage converter is less than a preset voltage threshold, each of the bypass switches is disconnected, and the AC grid performs initial charging of the high-voltage cascaded energy storage converter through each of the starting resistors. When the voltage of the DC capacitor in the high-voltage cascaded energy storage converter is greater than or equal to the preset voltage threshold, each of the bypass switches is closed, bypassing each of the starting resistors, and the AC grid charges the high-voltage cascaded energy storage converter.

[0007] Optionally, the circuit further includes: a plurality of grounding disconnect switches; the first terminal of each grounding disconnect switch is connected to a bypass switch, a starting resistor and the AC power grid, and the second terminal of each grounding disconnect switch is grounded.

[0008] Optionally, each phase of the converter bridge arm includes: a plurality of power modules connected in series.

[0009] Optionally, the circuit includes: a first star-connected disconnect switch, a second star-connected disconnect switch, a third star-connected disconnect switch, a first delta-connected disconnect switch, a second delta-connected disconnect switch, and a third delta-connected disconnect switch; the high-voltage cascaded energy storage converter includes: an A-phase converter bridge arm, a B-phase converter bridge arm, and a C-phase converter bridge arm. The first terminal of the first star-connected disconnect switch is connected to the end of the A-phase converter bridge arm and the first terminal of the first delta-connected disconnect switch; the first terminal of the second star-connected disconnect switch is connected to the end of the B-phase converter bridge arm and the first terminal of the second delta-connected disconnect switch; the first terminal of the third star-connected disconnect switch is connected to the end of the C-phase converter bridge arm and the first terminal of the third delta-connected disconnect switch; the second terminals of the first star-connected disconnect switch, the second terminals of the second star-connected disconnect switch, and the second terminal of the second star-connected disconnect switch are short-circuited in three phases. The second end of the first angle-connected disconnect switch is connected to the first end of the A-phase converter bridge arm, the second end of the second star-connected disconnect switch is connected to the first end of the B-phase converter bridge arm, and the second end of the second star-connected disconnect switch is connected to the first end of the C-phase converter bridge arm.

[0010] Optionally, both star-connected and delta-connected disconnecting switches are three-phase disconnecting switches or three-phase circuit breakers.

[0011] The circuit includes: A-phase star-connected disconnect switch, B-phase star-connected disconnect switch, C-phase star-connected disconnect switch, A-phase angle-connected disconnect switch, B-phase angle-connected disconnect switch and C-phase angle-connected disconnect switch; the high-voltage cascaded energy storage converter includes: A-phase converter bridge arm, B-phase converter bridge arm and C-phase converter bridge arm. The first terminal of the A-phase star-connected disconnect switch is connected to the end of the A-phase converter bridge arm and the first terminal of the A-phase angle-connected disconnect switch. The first terminal of the B-phase star-connected disconnect switch is connected to the end of the B-phase converter bridge arm and the first terminal of the B-phase angle-connected disconnect switch. The first terminal of the C-phase star-connected disconnect switch is connected to the end of the C-phase converter bridge arm and the first terminal of the C-phase angle-connected disconnect switch. The second terminals of the A-phase star-connected disconnect switch, the B-phase star-connected disconnect switch, and the B-phase star-connected disconnect switch are short-circuited in three phases. The second terminal of the phase A delta disconnect switch is connected to the first terminal of the phase A converter bridge arm, the second terminal of the phase B star disconnect switch is connected to the first terminal of the phase B converter bridge arm, and the second terminal of the phase B star disconnect switch is connected to the first terminal of the phase C converter bridge arm.

[0012] The present invention also proposes a star-delta topology conversion system, the system comprising: a star-connected disconnecting switch cabinet, a delta-connected disconnecting switch cabinet, and a high-voltage cascaded energy storage converter, wherein the high-voltage cascaded energy storage converter comprises: a three-phase converter bridge arm; The star-connected disconnect switch cabinet is equipped with a three-phase star-connected disconnect switch, which is connected to the three phases of the star-connected disconnect switch cabinet respectively. The delta-connected disconnect switch cabinet is equipped with a three-phase delta-connected disconnect switch, which is connected to the three phases of the delta-connected disconnect switch cabinet respectively. The three phases of the star-connected disconnect switchgear and the three phases of the delta-connected disconnect switchgear are respectively connected to the three-phase converter bridge arm in the high-voltage cascaded energy storage converter to form a star-delta conversion circuit; The star-angle conversion circuit is the star-angle topology conversion circuit described above.

[0013] Optionally, the system further includes: a starting resistor cabinet, a bypass switch cabinet, and an outgoing line cabinet; The starting resistor cabinet is equipped with three starting resistors, the bypass switch cabinet is equipped with three bypass switches, and the outgoing line cabinet is equipped with a three-way connection for connecting the series reactor. The starting resistor cabinet, the bypass switch cabinet, the outgoing line cabinet, the delta-connected disconnect switch cabinet, and the star-connected disconnect switch cabinet are connected in sequence via rigid copper busbars. The starting resistor in the starting resistor cabinet, the bypass switch in the bypass switch cabinet, and the series reactor connected to the outgoing line cabinet are connected according to the star-delta topology conversion circuit.

[0014] Optionally, the lower end of the star-connected disconnect switchgear and the lower end of the corner-connected disconnect switchgear are connected by a jumper bus in a rigid copper busbar; Phase A of the corner disconnect switchgear is connected to phase C of the star disconnect switchgear, phase B of the corner disconnect switchgear is connected to phase A of the star disconnect switchgear, and phase C of the corner disconnect switchgear is connected to phase B of the star disconnect switchgear. When the converter bridge arm in the high-voltage cascaded energy storage converter is a star-connected topology, the star-connected disconnect switch in the star-connected disconnect switch cabinet is turned on. When the converter bridge arm in the high-voltage cascaded energy storage converter is a corner-connected topology, the corner-connected disconnect switch in the corner-connected disconnect switch cabinet is turned on.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a star-delta topology conversion circuit and a star-delta topology conversion system. The star-delta topology conversion circuit converts the topology of the converter bridge arm in a high-voltage cascaded energy storage converter by activating either a star-connected or delta-connected isolating switch. This facilitates operation, reduces the conversion time between the two topologies, and improves the operational efficiency of topology conversion. Furthermore, a state interlock is provided between the star-connected and delta-connected isolating switches to prevent simultaneous activation of both switches, thus avoiding operational errors during topology conversion and reducing the risk of misoperation.

[0016] The star-delta topology conversion system uses star-connected disconnect switches and delta-connected disconnect switches installed in the star-connected disconnect switch cabinet and the delta-connected disconnect switch cabinet respectively. The star-connected disconnect switch cabinet and the delta-connected disconnect switch cabinet are connected by busbars, which reduces the use of cables, makes the site layout simple and neat, and the Y-Δ conversion can be achieved by operating the switches on the electrical cabinet. Attached Figure Description

[0017] Figure 1 A schematic diagram of a star-delta topology conversion circuit provided by the present invention; Figure 2 A topology diagram of Y-Δ transformation of a high-voltage cascaded energy storage converter provided by the present invention; Figure 3 A diagram of an electrical cabinet provided by the present invention; Figure 4 This is a schematic diagram illustrating a connection method between a star junction box and a corner junction box provided by the present invention. Detailed Implementation

[0018] Example 1: Figure 1 This is a schematic diagram of a star-delta topology conversion circuit provided by the present invention, as shown below. Figure 1As shown, the star-delta topology conversion circuit may include: a multi-phase star disconnect switch, a multi-phase delta disconnect switch, and a high-voltage cascaded energy storage converter. The high-voltage cascaded energy storage converter includes: multi-phase converter arms, each phase of which is connected via a star disconnect switch to form a star topology, and each phase of which is connected sequentially via a delta disconnect switch to form a delta topology. A state interlock is provided between the multi-phase star disconnect switch and the multi-phase delta disconnect switch to prevent them from being simultaneously turned on. When the multi-phase star disconnect switch is on, the converter arms in the high-voltage cascaded energy storage converter are star-connected; when the multi-phase delta disconnect switch is on, the converter arms in the high-voltage cascaded energy storage converter are delta-connected.

[0019] Each phase of the converter bridge arm includes multiple power modules connected in series. These power modules are the main energy conversion devices, capable of operating in rectification mode to charge the energy storage medium on the DC side of the PCS, or in inverter mode to release energy from the storage medium. A star topology can be represented by the symbol "Y," and a delta topology by the symbol "△." State interlocking can employ mechanical interlocking, electrical interlocking, or PLC (Programmable Logic Controller) logic interlocking. The type and implementation method of the interlocking mechanism are selected according to the actual application scenario of this invention. The implementation methods of state interlocking are common techniques in this field, and will not be elaborated upon further in this invention.

[0020] It should be noted that the end of each phase converter bridge arm connected to the AC grid can be considered the starting end, and the other end the ending end. The ending end of each phase converter bridge arm is connected to one end of a one-phase star-connected disconnect switch and one end of a one-phase delta-connected disconnect switch, respectively. The other ends of the multi-phase star-connected disconnect switches are interconnected. The other end of each phase delta-connected disconnect switch is connected to the starting end of other phase converter bridge arms, thus connecting the multi-phase converter bridge arms sequentially end-to-end. A state interlock is implemented between the multi-phase star-connected disconnect switches and the multi-phase delta-connected disconnect switches. That is, when the multi-phase star-connected disconnect switch is on, the multi-phase delta-connected disconnect switch is in the off state, and when the multi-phase delta-connected disconnect switch is on, the multi-phase star-connected disconnect switch is in the off state. This prevents simultaneous on / off operation of the multi-phase star-connected disconnect switches and thus reduces the risk of operational errors during topology conversion. For example, the circuit includes: an A-phase star-connected disconnect switch, a B-phase star-connected disconnect switch, a C-phase star-connected disconnect switch, an A-phase angle-connected disconnect switch, a B-phase angle-connected disconnect switch, and a C-phase angle-connected disconnect switch; the high-voltage cascaded energy storage converter includes: an A-phase converter bridge arm, a B-phase converter bridge arm, and a C-phase converter bridge arm; the first terminal of the A-phase star-connected disconnect switch is connected to the end of the A-phase converter bridge arm and the first terminal of the A-phase angle-connected disconnect switch; the first terminal of the B-phase star-connected disconnect switch is connected to the end of the B-phase converter bridge arm and the first terminal of the B-phase angle-connected disconnect switch. The C-phase star-connected disconnector is connected to the end of the C-phase converter bridge arm and the first end of the C-phase delta-connected disconnector. The second ends of the A-phase star-connected disconnector, the B-phase star-connected disconnector, and the B-phase star-connected disconnector are short-circuited in three phases. The second end of the A-phase delta-connected disconnector is connected to the first end of the A-phase converter bridge arm, the second end of the B-phase star-connected disconnector is connected to the first end of the B-phase converter bridge arm, and the second end of the B-phase star-connected disconnector is connected to the first end of the C-phase converter bridge arm. Both the star-connected and delta-connected disconnectors are three-phase disconnectors or three-phase circuit breakers.

[0021] Optionally, the circuit further includes: a plurality of series reactors; each phase of the converter bridge arm is connected to the AC power grid through one of the series reactors.

[0022] It should be noted that the number of series reactors is the same as the number of phases in the converter bridge arms. Multiple series reactors are connected to the PCS converter and the grid side (i.e., the AC power grid) for energy exchange between the two sides.

[0023] Optionally, the circuit further includes: multiple starting resistors and multi-phase bypass switches; each of the series reactors is connected to the AC power grid via one phase of the bypass switch, and each phase of the bypass switch is connected in parallel with one of the starting resistors.

[0024] The bypass switch is used to start the energy storage device (i.e., the high-voltage cascaded energy storage converter). When the PCS is activated, the bypass switch is in the open state. After the DC-side capacitor voltage is established, the bypass switch closes. The starting resistor, connected in parallel with the bypass switch, is used to limit the current when the energy storage device is activated. When the initial charging of the device's DC capacitor is completed and the control unit in the PCS module (i.e., the sub-module in the high-voltage cascaded energy storage converter) can operate normally, the bypass switch closes, the bypass starting resistor is turned off, and the PCS continues the second stage of capacitor charging until the charging voltage reaches the set value.

[0025] It should be noted that when the high-voltage cascaded energy storage converter is in a charging state and the voltage of the DC capacitor in the high-voltage cascaded energy storage converter is less than a preset voltage threshold, each of the bypass switches is open, and the AC grid initially charges the high-voltage cascaded energy storage converter through each of the starting resistors; when the voltage of the DC capacitor in the high-voltage cascaded energy storage converter is greater than or equal to the preset voltage threshold, each of the bypass switches is closed, bypassing each of the starting resistors, and the AC grid charges the high-voltage cascaded energy storage converter.

[0026] Optionally, the circuit further includes: a plurality of grounding disconnect switches; the first terminal of each grounding disconnect switch is connected to a bypass switch, a starting resistor and the AC power grid, and the second terminal of each grounding disconnect switch is grounded.

[0027] It should be noted that the grounding disconnect switch is used to activate the grounding disconnect switch after the branch circuit is taken out of operation, in order to ensure operational safety when someone enters the work area to perform operations.

[0028] For example, Figure 2 A topology diagram of a high-voltage cascaded energy storage converter Y-Δ transformation provided by the present invention is shown below. Figure 2 As shown, a high-voltage cascaded energy storage converter Y-Δ conversion circuit (i.e., star-delta topology conversion circuit) includes circuits connecting circuits such as circuit breakers, starting resistors, bypass switches, star-connected disconnect switches, delta-connected disconnect switches, and converters to achieve Y-Δ conversion of the connected circuits. The high-voltage cascaded energy storage converter includes: A-phase converter bridge arm, B-phase converter bridge arm, and C-phase converter bridge arm; DS is a grounding disconnect switch; QF is a bypass switch; RA, RB, and RC are the starting resistors for the A-phase converter bridge arm, B-phase converter bridge arm, and C-phase converter bridge arm, respectively; L1 is a series reactor; AM1 and AM30 are power modules of the AC converter (PCS); and AD1 and AD8 are the energy storage media on the DC side of the PCS. QS1 (delta-connected disconnect switch) and QS2 (star-connected disconnect switch) are Y-Δ conversion disconnect switches. Both QS1 and QS2 use three-phase disconnect switches, but three-phase circuit breakers can also be used. This system allows for testing and verification of the equipment in both star and delta configurations. In a star configuration, QS1 is closed and QS2 is open. In a delta configuration, QS1 is open and QS2 is closed. One end of the surge arrester is connected to the series reactor L1 and the bypass switch QF, while the other end is grounded.

[0029] The topology of the Y-Δ transformation is that QS1 needs to be placed at the end of the wiring device, at the neutral point of the star connection three phases, with one end of the switch connected to one end of the other device in each phase, and the other end short-circuited in all three phases; the second key point is that QS2 is also at the end of the wiring device, with one end connected to one end of QS1, and the other end connected to the beginning of the adjacent device in another phase, thus achieving a delta connection.

[0030] Example 2: Based on the same inventive concept, this invention also provides a star-delta topology conversion system, the system comprising: a star-connected disconnecting switchgear, a delta-connected disconnecting switchgear, and a high-voltage cascaded energy storage converter, wherein the high-voltage cascaded energy storage converter comprises: a three-phase converter bridge arm; the star-connected disconnecting switchgear is provided with a three-phase star-connected disconnecting switch, the three-phase star-connected disconnecting switch being connected to the three phases of the star-connected disconnecting switchgear respectively; the three phases of the star-connected disconnecting switchgear, the three phases of the delta-connected disconnecting switchgear, and the three-phase converter bridge arm of the high-voltage cascaded energy storage converter are respectively connected to form a star-delta conversion circuit; wherein, the star-delta conversion circuit is the aforementioned star-delta topology conversion circuit.

[0031] It should be noted that both star-connected and delta-connected disconnecting switchgear include phases A, B, and C. The three-phase star-connected disconnecting switches are connected to phases A, B, and C of the star-connected disconnecting switchgear, respectively. Similarly, the three-phase delta-connected disconnecting switches are connected to phases A, B, and C of the delta-connected disconnecting switchgear, respectively. For example, a star-connected disconnecting switchgear may contain phases A, B, and C. The phase A star-connected disconnecting switch is connected to phase A of the star-connected disconnecting switchgear, the phase B star-connected disconnecting switch is connected to phase B of the star-connected disconnecting switchgear, and the phase C star-connected disconnecting switch is connected to phase C of the star-connected disconnecting switchgear. The connection method between the delta-connected disconnecting switchgear and the three-phase delta-connected disconnecting switches is the same as that between star-connected disconnecting switchgear and star-connected disconnecting switches. Therefore, this invention will not further describe the connection method between the delta-connected disconnecting switchgear and the three-phase delta-connected disconnecting switches. In general, the three phases of the star-connected and delta-connected disconnecting switchgear can be understood as a three-way interconnection.

[0032] A method for rapid conversion of a Y-Δ topology in a high-voltage cascaded energy storage converter (PCS) and its control cabinet configuration is characterized by the use of two three-phase switches. One switch is connected to the end of the branch, i.e., the neutral point side, and one end of the other switch is connected to one end of the neutral point side switch, while the A, B, and C phases of the other end are connected to the B, C, and A phases of the bypass switch. The two switches (i.e., a star-connected isolating switch and a delta-connected isolating switch) respectively realize the star-connection and delta-connection conversion of the circuit topology. The switches can be three-phase isolating switches, three-phase circuit breakers, or three-phase contactors.

[0033] Optionally, the system further includes: a starting resistor cabinet, a bypass switch cabinet, and an outgoing line cabinet; The starting resistor cabinet is equipped with three starting resistors, the bypass switch cabinet is equipped with three bypass switches, and the outgoing line cabinet is equipped with a three-way connection for connecting the series reactor. The starting resistor cabinet, the bypass switch cabinet, the outgoing line cabinet, the delta-connected disconnect switch cabinet, and the star-connected disconnect switch cabinet are connected in sequence via rigid copper busbars. The starting resistor in the starting resistor cabinet, the bypass switch in the bypass switch cabinet, and the series reactor connected to the outgoing line cabinet are connected according to the star-delta topology conversion circuit.

[0034] To improve switching efficiency, reduce misoperation, and improve the aesthetics of the laboratory layout, this invention proposes a connection method capable of rapid Y-Δ topology transformation and a customized electrical cabinet layout. All switches used for switching are housed within the cabinet, and all wiring is pre-connected. When performing knife switch operations, only remote electric operation or on-site manual operation is required, making operation convenient, efficient, and eliminating the risk of incorrect wiring. The site layout is also neat and rational.

[0035] The topology of the Y-Δ transformation is that the starting resistor, bypass switch, and Y-Δ transformation isolating switch are all placed inside the cabinet. The relevant equipment is placed in a standard-sized cabinet. By designing the installation position of these devices inside the cabinet and considering the arrangement order between the cabinets, the Y-Δ transformation can be easily switched. At the same time, the reduced equipment layout in the test site makes the site cleaner and tidier.

[0036] The invention actually uses multiple customized electrical cabinets for primary equipment connection, including 5 electrical cabinets: bypass switch cabinet, resistor cabinet, star-connected isolating switch cabinet, corner-connected isolating switch cabinet, and outgoing line cabinet.

[0037] For example, Figure 3 This invention provides a parallel configuration diagram of an electrical cabinet. The Y-Δ transformation topology uses five electrical cabinets arranged in parallel as follows: Figure 3 The arrangement shown, from left to right, comprises a starting resistor cabinet, a bypass switch cabinet, an outgoing line cabinet, a corner connection cabinet (i.e., a corner disconnect switch cabinet), and a star connection cabinet (i.e., a star disconnect switch cabinet). The electrical cabinets are connected to the external environment via cables laid in cable trenches to reduce the number of ground cables. The cabinets are connected using rigid copper busbars located at the top of the cabinets. The starting resistor R, bypass switch QF, star disconnect switch QS1, and corner disconnect switch QS2 are each housed in a standard switch cabinet, with an additional outgoing line cabinet connecting to the reactor. The switch cabinets for the starting resistor cabinet (AH1), bypass switch cabinet (AH2), outgoing line cabinet (AH3), corner connection cabinet (AH4), and star connection cabinet (AH5) are all model KYN61-40.5.

[0038] A method for rapid conversion of a high-voltage cascaded energy storage converter (PCS) Y-Δ topology and configuration of the control cabinet is characterized by the use of an electrical panel cabinet installation method, such as... Figure 3 As shown, the bypass switch and starting resistor can also be placed in one panel cabinet, and the outgoing line cabinet can be merged into other cabinets, according to... Figure 3 The electrical connection method shown is designed for inter-cabinet connections. A cable from the starting resistor or bypass switch is connected to the external circuit. The starting resistor and bypass switch are connected in parallel and then to the corner junction switch, with a cable leading out to the series reactor. Cables from the star junction cabinet are connected to the external energy storage PCS and battery compartment.

[0039] Optionally, the lower end of the star-connected disconnect switchgear and the lower end of the corner-connected disconnect switchgear are connected by a jumper busbar in a rigid copper busbar; phase A of the corner-connected disconnect switchgear is connected to phase C of the star-connected disconnect switchgear, phase B of the corner-connected disconnect switchgear is connected to phase A of the star-connected disconnect switchgear, and phase C of the corner-connected disconnect switchgear is connected to phase B of the star-connected disconnect switchgear; when the converter bridge arm in the high-voltage cascaded energy storage converter is a star-connected topology, the star-connected disconnect switch in the star-connected disconnect switchgear is turned on; when the converter bridge arm in the high-voltage cascaded energy storage converter is a corner-connected topology, the corner-connected disconnect switch in the corner-connected disconnect switchgear is turned on.

[0040] The lower port of a star-connected or corner-connected isolating switchgear usually refers to the load-side outgoing port of the star-connected or corner-connected isolating switchgear, which can be specifically the outgoing terminal block or busbar of each isolating switch. In some scenarios, the lower port of a star-connected or corner-connected isolating switchgear can also be understood as the wiring port near the ground.

[0041] It should be noted that the Y-Δ transformation topology enables convenient operation of the five-sided electrical cabinet, where the bottom of the corner junction cabinet is connected to the bottom of the star junction cabinet (i.e., the star junction isolating switch cabinet) via a jumper bar.

[0042] For example, when connecting jumpers, the connection is not made according to the following order: A phase of the corner jumper connects to A phase of the star jumper, B phase to B phase, and C phase to C phase. Instead, it is based on... Figure 4 In the connection configuration, phase A of the corner junction cabinet is connected to phase C of the star junction cabinet, phase B of the corner junction cabinet is connected to phase A of the star junction cabinet, and phase C of the corner junction cabinet is connected to phase B of the star junction cabinet. When a star topology is required, the isolating switch of the star junction cabinet is in the closed position, and the isolating switch of the corner junction cabinet is in the open position. When a corner topology is required, the isolating switch of the star junction cabinet is in the open position, and the isolating switch of the corner junction cabinet is in the closed position. The isolating switches between the corner junction cabinet and the star junction cabinet are designed with state interlocking, preventing the two switches from being closed simultaneously, thus avoiding accidental operation by test personnel.

[0043] A method for rapid conversion of a Y-Δ topology in a high-voltage cascaded energy storage converter (PCS) and configuration of its control cabinet is characterized by the connection method between the star-connected cabinet and the delta-connected cabinet, such as... Figure 4 As shown, the connection between the star junction box and the corner junction box adopts a cross-connection phase-by-phase connection. Phase A of the corner junction box is connected to phase C of the star junction box, phase B of the corner junction box is connected to phase A of the star junction box, and phase C of the corner junction box is connected to phase B of the star junction box. The star switch and the corner switch are interlocked in their states, and the two switches cannot be in the closed position at the same time.

[0044] This invention proposes a convenient connection method and electrical cabinet configuration and paralleling method for a high-voltage cascaded energy storage converter used as a test platform in a laboratory, enabling the converter to quickly perform Y-Δ transformation operations. The advantages of this invention are as follows: 1) A laboratory high-voltage cascaded energy storage converter was proposed as a test platform to realize the convenient operation and wiring method of mutual conversion between star connection and delta connection topologies. According to this wiring method, the time for test personnel to switch between the two topologies during the test can be reduced, and the risk of misoperation can be reduced.

[0045] 2) It is proposed to use an electrical cabinet to install some primary electrical equipment. Through reasonable design layout and cabinet connection, Y-Δ transformation can be operated on the electrical cabinet, which reduces the number of cable connections between primary equipment and allows Y-Δ transformation to be achieved by operating the switch on the cabinet.

[0046] In summary, the connection method for Y-Δ conversion of the converter and the parallel configuration of the electrical cabinet proposed in this invention, when used as a test platform for a high-voltage cascaded energy storage converter in a laboratory, can improve the efficiency of switching between star and delta connection test topologies on-site. Some primary equipment is installed in a cabinet and connected via busbars, reducing cable usage and resulting in a simple and neat on-site layout. Switching between star and delta connections requires only the operation of two isolating switches, and the switches employ an interlocking design, enhancing the safety of the test operation.

[0047] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A star-delta topology conversion circuit, characterized in that, The circuit includes: a multi-phase star-connected disconnect switch, a multi-phase delta-connected disconnect switch, and a high-voltage cascaded energy storage converter. The high-voltage cascaded energy storage converter includes: multi-phase converter bridge arms. Each phase of the converter bridge arm is connected through the star-connected disconnect switch to form a star topology. Each phase of the converter bridge arm is connected end-to-end through the delta-connected disconnect switch to form a delta topology. A state interlock is provided between the multi-phase star-connected disconnect switch and the multi-phase delta-connected disconnect switch to prevent the star-connected disconnect switch and the delta-connected disconnect switch from being turned on at the same time. When the multi-phase star-connected disconnect switch is turned on, the converter bridge arms in the high-voltage cascaded energy storage converter are star-connected; when the multi-phase delta-connected disconnect switch is turned on, the converter bridge arms in the high-voltage cascaded energy storage converter are delta-connected.

2. The circuit according to claim 1, characterized in that, The circuit also includes: multiple series reactors; each phase of the converter bridge arm is connected to the AC power grid through one of the series reactors.

3. The circuit according to claim 2, characterized in that, The circuit further includes: multiple starting resistors and multi-phase bypass switches; each of the series reactors is connected to the AC power grid via a phase bypass switch, and each phase bypass switch is connected in parallel with a starting resistor.

4. The circuit according to claim 3, characterized in that, When the high-voltage cascaded energy storage converter is in a charging state and the voltage of the DC capacitor in the high-voltage cascaded energy storage converter is less than a preset voltage threshold, each of the bypass switches is disconnected, and the AC grid performs initial charging of the high-voltage cascaded energy storage converter through each of the starting resistors. When the voltage of the DC capacitor in the high-voltage cascaded energy storage converter is greater than or equal to the preset voltage threshold, each of the bypass switches is closed, bypassing each of the starting resistors, and the AC grid charges the high-voltage cascaded energy storage converter.

5. The circuit according to claim 4, characterized in that, The circuit further includes: a plurality of grounding disconnect switches; the first end of each grounding disconnect switch is connected to a bypass switch, a starting resistor and the AC power grid, and the second end of each grounding disconnect switch is grounded.

6. The circuit according to claim 1, characterized in that, Each phase of the converter bridge arm includes: multiple power modules connected in series.

7. The circuit according to any one of claims 1-6, characterized in that, Both star-connected and delta-connected disconnecting switches use three-phase disconnecting switches or three-phase circuit breakers.

8. The circuit according to claim 7, characterized in that, The circuit includes: A-phase star-connected disconnect switch, B-phase star-connected disconnect switch, C-phase star-connected disconnect switch, A-phase angle-connected disconnect switch, B-phase angle-connected disconnect switch and C-phase angle-connected disconnect switch; the high-voltage cascaded energy storage converter includes: A-phase converter bridge arm, B-phase converter bridge arm and C-phase converter bridge arm. The first terminal of the A-phase star-connected disconnect switch is connected to the end of the A-phase converter bridge arm and the first terminal of the A-phase angle-connected disconnect switch. The first terminal of the B-phase star-connected disconnect switch is connected to the end of the B-phase converter bridge arm and the first terminal of the B-phase angle-connected disconnect switch. The first terminal of the C-phase star-connected disconnect switch is connected to the end of the C-phase converter bridge arm and the first terminal of the C-phase angle-connected disconnect switch. The second terminals of the A-phase star-connected disconnect switch, the B-phase star-connected disconnect switch, and the B-phase star-connected disconnect switch are short-circuited in three phases. The second terminal of the phase A delta disconnect switch is connected to the first terminal of the phase A converter bridge arm, the second terminal of the phase B star disconnect switch is connected to the first terminal of the phase B converter bridge arm, and the second terminal of the phase B star disconnect switch is connected to the first terminal of the phase C converter bridge arm.

9. A star-angle topology conversion system, characterized in that, The system includes: a star-connected disconnect switchgear, a delta-connected disconnect switchgear, and a high-voltage cascaded energy storage converter, wherein the high-voltage cascaded energy storage converter includes: a three-phase converter bridge arm; The star-connected disconnect switch cabinet is equipped with a three-phase star-connected disconnect switch, which is connected to the three phases of the star-connected disconnect switch cabinet respectively. The delta-connected disconnect switch cabinet is equipped with a three-phase delta-connected disconnect switch, which is connected to the three phases of the delta-connected disconnect switch cabinet respectively. The three phases of the star-connected disconnect switchgear and the three phases of the delta-connected disconnect switchgear are respectively connected to the three-phase converter bridge arm in the high-voltage cascaded energy storage converter to form a star-delta conversion circuit; The star-angle conversion circuit is the star-angle topology conversion circuit described in any one of claims 1-8.

10. The system according to claim 9, characterized in that, The system also includes: a starting resistor cabinet, a bypass switch cabinet, and an outgoing line cabinet; The starting resistor cabinet is equipped with three starting resistors, the bypass switch cabinet is equipped with three bypass switches, and the outgoing line cabinet is equipped with a three-way connection for connecting the series reactor. The starting resistor cabinet, the bypass switch cabinet, the outgoing line cabinet, the delta-connected disconnect switch cabinet, and the star-connected disconnect switch cabinet are connected in sequence via rigid copper busbars. The starting resistor in the starting resistor cabinet, the bypass switch in the bypass switch cabinet, and the series reactor connected to the outgoing line cabinet are connected according to the star-delta topology conversion circuit.

11. The system according to claim 9 or 10, characterized in that, The lower opening of the star-connected disconnect switchgear and the lower opening of the corner-connected disconnect switchgear are connected by a jumper bus in a rigid copper busbar. Phase A of the corner disconnect switchgear is connected to phase C of the star disconnect switchgear, phase B of the corner disconnect switchgear is connected to phase A of the star disconnect switchgear, and phase C of the corner disconnect switchgear is connected to phase B of the star disconnect switchgear. When the converter bridge arm in the high-voltage cascaded energy storage converter is a star-connected topology, the star-connected disconnect switch in the star-connected disconnect switch cabinet is turned on. When the converter bridge arm in the high-voltage cascaded energy storage converter is a corner-connected topology, the corner-connected disconnect switch in the corner-connected disconnect switch cabinet is turned on.

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