Hybrid flexible interconnection device for series compensation

Abstract

The invention discloses a hybrid flexible interconnection device for series compensation. The hybrid flexible interconnection device comprises a series converter, a variable frequency transformer, a first reactive harmonic compensation device, a second reactive harmonic compensation device, a switch S1a, a switch S1b, a switch S1c, a switch S2a, a switch S2b, a switch S2c, a switch Spa, a switch Spb, a switch Spc, a resistor Ra, a resistor Rb, a resistor Rc and a control protection system. The method has stronger line power flow regulation capability, is higher in power flow regulation speed, has certain reactive compensation capability, and can realize interconnection of alternating current distribution networks. Benefited from the power characteristic of the series converter, the rated power of the required series converter is far less than the rated transmission power between the distribution networks, so that the manufacturing cost of the series compensation hybrid flexible interconnection device is lower than that of a back-to-back converter based on the multi-level technology.

Description

Technical Field

[0001] This invention belongs to the field of AC distribution network interconnection equipment and technology, and specifically relates to a hybrid flexible interconnection device with series compensation. Background Technology

[0002] Under the backdrop of energy conservation requirements, the integration of numerous indirect and distributed power sources into the distribution network presents new challenges in terms of power supply reliability and power flow control. Variable frequency transformers (VFDs), as grid interconnection devices based on mechanical motion to regulate power flow, offer advantages over power electronics-based flexible interconnection devices in terms of high reliability, high efficiency, and simple control. Furthermore, they are suitable for synchronous grids, asynchronous grids, and grid interconnections at different voltage levels.

[0003] Existing power distribution network interconnection devices are mostly flexible interconnection devices based on power semiconductor devices or mechanical power flow regulation devices based on frequency converters. Both types of devices have their drawbacks: flexible interconnection devices based on power semiconductor devices have poor fault tolerance and high cost; mechanical power flow regulation devices based on frequency converters have slow dynamic response speed and poor dynamic performance. Therefore, researching power distribution network interconnection devices with fast dynamic response speed and strong fault tolerance is of great practical significance. Summary of the Invention

[0004] To address the above problems, this invention proposes a hybrid flexible interconnect device with series compensation, the specific technical solution of which is as follows:

[0005] A series-compensated hybrid flexible interconnection device includes: a series converter, a frequency converter, a first reactive harmonic compensation device, a second reactive harmonic compensation device, and a switch S. 1a Switch S 1b Switch S 1c Switch S 2a Switch S 2b Switch S 2c Switch S pa Switch S pb Switch S pc Resistance R a Resistance R b Resistance R c Control and protection systems;

[0006] The series converter is used to improve the dynamic response speed of the series-compensated hybrid flexible interconnect device, thereby compensating for the dynamic characteristics of the frequency converter.

[0007] The frequency converter transformer is used to regulate the active power between the first AC port and the second AC port;

[0008] The first reactive harmonic compensation device is used to compensate for the reactive power and harmonic current of the first AC port when the series-compensated hybrid flexible interconnect device is running.

[0009] The second reactive harmonic compensation device is used to compensate for the reactive power and harmonic current of the second AC port when the series-compensated hybrid flexible interconnect device is running.

[0010] Switch S 1a Switch S 1b Switch S 1c For connecting or disconnecting the series-compensated hybrid flexible interconnect device from the first AC power source;

[0011] Switch S 2a Switch S 2b Switch S 2c Used to connect or disconnect the series-compensated hybrid flexible interconnect device from the second AC power source.

[0012] Switch S pa Switch S pb Switch S pc Used to connect resistor R a Resistance R b Resistance R c Connect to the main power circuit or bypass it from the main power circuit;

[0013] resistor R a Resistance R b Resistance R c Used to suppress surge currents generated when the series-compensated hybrid flexible interconnect device is connected to the first AC power supply and the second AC power supply;

[0014] The control and protection system is used to execute control strategies, issue control commands to various parts, and receive feedback signals from various parts.

[0015] The present invention has the following beneficial effects:

[0016] The hybrid flexible interconnection device with series compensation proposed in this invention has stronger line power flow regulation capability and faster power flow regulation speed compared to frequency converters, while also possessing a certain reactive power compensation capability, enabling the interconnection of multiple AC distribution networks. Thanks to the power characteristics of the series converter, the required rated power of the series converter is much smaller than the rated transmission power between distribution networks, making the cost of the hybrid flexible interconnection device with series compensation lower than that of back-to-back converters based on multi-level technology. Attached Figure Description

[0017] Figure 1 This is a circuit topology diagram of a hybrid flexible interconnect device;

[0018] Figure 2 The preferred submodule x k Circuit diagram (x=a, b, c, k=1~N). Detailed Implementation

[0019] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0020] The present invention provides a series-compensated hybrid flexible interconnect device, such as... Figure 1 As shown, it includes: a series converter, a frequency converter, a first reactive power harmonic compensation device, a second reactive power harmonic compensation device, and a switch S. 1a Switch S 1b Switch S 1c Switch S 2a Switch S 2b Switch S 2c Switch S pa Switch S pb Switch S pc Resistance R a Resistance R b Resistance R c and control and protection system. A series converter is used to improve the dynamic response speed of the series-compensated hybrid flexible interconnection device, thereby compensating for the dynamic characteristics of the frequency converter transformer; the frequency converter transformer is used to regulate the active power between the first AC port and the second AC port; a first reactive harmonic compensation device is used to compensate for the reactive power and harmonic current of the first AC port when the series-compensated hybrid flexible interconnection device is running; a second reactive harmonic compensation device is used to compensate for the reactive power and harmonic current of the second AC port when the series-compensated hybrid flexible interconnection device is running; switch S 1a Switch S 1b Switch S 1c For connecting or disconnecting the series-compensated hybrid flexible interconnect device from the first AC power source; switch S 2a Switch S 2b Switch S 2c For connecting or disconnecting the series-compensated hybrid flexible interconnect device from the second AC power source; switch S pa Switch S pb Switch S pc Used to connect resistor R a Resistance R b Resistance R c Connect to the main power circuit or bypass it; resistor Ra Resistance R b Resistance R c The system is used to suppress surge currents generated when the hybrid flexible interconnect device with series compensation is connected to the first AC power supply and the second AC power supply; the control and protection system is used to execute control strategies, issue control commands to each part, and receive feedback signals from each part.

[0021] A series converter containing 3N sub-modules, namely sub-module a1, sub-module a2... sub-module a N Submodule b1, submodule b2... submodule b N Submodule c1, submodule c2... submodule c N Submodule a j T (j=1~N-1) aj,2 Terminal and submodule a (j+1) T a(j+1),1 End connection, submodule a N T aN,2 The T terminal of phase A of the first AC port of the frequency converter transformer v11 End connection, submodule b j T bj,2 End and submodule b (j+1) T b(j+1),1 End connection, submodule b N T bN,2 The T terminal of phase B of the first AC port of the frequency converter transformer v12 End connection, submodule c j T cj,2 Terminal and submodule c (j+1) T c(j+1),1 End connection, submodule c N T cN,2 The T terminal of the first AC port C phase of the frequency converter transformer v13 The ends are connected.

[0022] T at the second AC port A phase of the frequency converter transformer v21 Terminal and switch S 2a T S2a1 The T phase of the second reactive harmonic compensation device a vc2a The terminals are connected, and the T-phase of phase B at the second AC port of the frequency converter transformer is connected. v22 Terminal and switch S 2b T S2b1 The T phase of the second reactive harmonic compensation device B phase vc2b The terminals are connected, and the T-phase of the second AC port C of the frequency converter transformer is connected. v23 Terminal and switch S 2c T S2c1 The T phase of the second reactive harmonic compensation device C phase vc2cThe terminals are connected. The first AC port and the second AC port of the frequency converter can be respectively connected to the stator winding port and the rotor winding port of the frequency converter, or the first AC port and the second AC port of the frequency converter can also be respectively connected to the rotor winding port and the stator winding port of the frequency converter.

[0023] Preferred submodule x k (x=a, b, c, k=1~N) The circuit topology is as follows Figure 2 As shown, it includes: power semiconductor device S xk1 Power semiconductor devices S xk2 Power semiconductor devices S xk3 Power semiconductor devices S xk4 Bypass switch S xk5 DC capacitor C xk Power semiconductor devices S xk1 collector and power semiconductor device S xk3 collector and DC capacitor C xk The positive terminal is connected to the power semiconductor device S. xk1 Emitter and power semiconductor device S xk2 collector and bypass switch S xk5 After the second terminal is connected, it becomes a submodule x k T xk,2 Terminal, power semiconductor device S xk3 Emitter and power semiconductor device S xk4 collector and bypass switch S xk5 After the first terminal is connected, it becomes a submodule x k T xk,1 Terminal, power semiconductor device S xk2 Emitter and power semiconductor device S xk4 emitter and DC capacitor C xk The negative terminal is connected.

[0024] Switch S 1a T S1a1 The first AC port of the hybrid flexible interconnect device, which serves as a series compensation terminal, is connected to phase A of the first AC power supply. Switch S... 1a T S1a2 The T-terminal of the first reactive harmonic compensation device A phase vc1a Terminal, resistor R a T Ra1 Terminal and switch S pa T Spa1 Terminals connected, switch S 1b T S1b1 Phase B of the first AC port of the hybrid flexible interconnect device with series compensation is connected to phase B of the first AC power supply, and switch S 1b TS1b2 The T-phase of the first reactive harmonic compensation device B is connected to the terminal. vc1b Terminal, resistor R b T Rb1 Terminal and switch S pb T Spb1 Terminals connected, switch S 1c T S1c1 The C phase of the first AC port of the hybrid flexible interconnect device with series compensation is connected to the C phase of the first AC power supply, and the switch S 1c T S1c2 The T-phase of the first reactive harmonic compensation device C is connected to the terminal. vc1c Terminal, resistor R c T Rc1 Terminal and switch S pc T Spc1 The ends are connected.

[0025] Switch S pa T Spa2 Terminal and resistor R a T Ra2 T of end and submodule a1 a1,1 Terminals connected, switch S pb T Spb2 Terminal and resistor R b T Rb2 T of end and submodule b1 b1,1 Terminals connected, switch S pc T Spc2 Terminal and resistor R c T Rc2 T of end and submodule c1 c1,1 The ends are connected.

[0026] Switch S 2a T S2a2 The A phase of the second AC port of the hybrid flexible interconnect device, which serves as a series compensation terminal, is connected to the A phase of the second AC power supply. Switch S 2b T S2b2 The B phase of the second AC port of the hybrid flexible interconnect device, which serves as a series compensation terminal, is connected to the B phase of the second AC power supply. Switch S 2c T S2c2 The C phase of the second AC port of the hybrid flexible interconnect device, which serves as a series compensation, is connected to the C phase of the second AC power supply.

[0027] The control and protection system includes at least one processor and multiple communication interfaces, as well as a memory communicatively connected to the processor. The memory contains instructions executable by the processor to implement a control strategy for the series-compensated hybrid flexible interconnect device. A first communication interface of the control and protection system is connected to the communication interface of the series converter; a second communication interface is connected to the communication interface of the frequency converter; a third communication interface is connected to the communication interface of the first reactive power harmonic compensation device; a fourth communication interface is connected to the communication interface of the second reactive power harmonic compensation device; and a fifth communication interface is connected to the switch S. 1a Switch S 1b Switch S 1c The communication interface is connected to the control and protection system's sixth communication interface and the switch S. 2a Switch S 2b Switch S 2c The communication interface is connected to the control and protection system's seventh communication interface and the switch S. pa Switch S pb Switch S pc The communication interface is connected.

[0028] During steady-state operation of the series-compensated hybrid flexible interconnection device, the fundamental component of the output voltage of the series converter approaches zero, absorbing only a minimal amount of active power to maintain the DC capacitor voltage of each submodule. The power transmitted on the line is adjusted by the rotation angle of the frequency converter rotor. During transient power changes, the series converter outputs a control voltage to rapidly adjust the power transmitted on the line to the commanded value. Simultaneously, the frequency converter rotor begins to rotate to adjust the power transmitted on the line. After the frequency converter rotor outputs a rotation angle control value, the voltage output by the series converter gradually decreases to near zero, while the power transmitted on the line remains unchanged at the commanded power value. The control and protection system of the series-compensated hybrid flexible interconnection device monitors the reactive power of the first and second AC ports in real time and compensates for it using the first and second reactive harmonic compensation devices, respectively. It can also receive reactive power and harmonic compensation commands from the power dispatch control center to perform reactive power and harmonic compensation on the interconnected power grid.

Claims

1. A hybrid flexible interconnect device with series compensation, characterized in that, include: Series converter, frequency converter, first reactive harmonic compensation device, second reactive harmonic compensation device, switch S 1a Switch S 1b Switch S 1c Switch S 2a Switch S 2b Switch S 2c Switch S pa Switch S pb Switch S pc Resistance R a Resistance R b Resistance R c Control and protection systems; The series converter is used to improve the dynamic response speed of the series-compensated hybrid flexible interconnect device, thereby compensating for the dynamic characteristics of the frequency converter. The frequency converter transformer is used to regulate the active power between the first AC port and the second AC port; The first reactive harmonic compensation device is used to compensate for the reactive power and harmonic current of the first AC port when the series-compensated hybrid flexible interconnect device is running. The second reactive harmonic compensation device is used to compensate for the reactive power and harmonic current of the second AC port when the series-compensated hybrid flexible interconnect device is running. Switch S 1a Switch S 1b Switch S 1c For connecting or disconnecting the series-compensated hybrid flexible interconnect device from the first AC power source; Switch S 2a Switch S 2b Switch S 2c Used to connect or disconnect the series-compensated hybrid flexible interconnect device from the second AC power source. Switch S pa Switch S pb Switch S pc Used to connect resistor R a Resistance R b Resistance R c Connect to the main power circuit or bypass it from the main power circuit; resistor R a Resistance R b Resistance R c Used to suppress surge currents generated when the series-compensated hybrid flexible interconnect device is connected to the first AC power supply and the second AC power supply; The control and protection system is used to execute control strategies, issue control commands to various parts, and receive feedback signals from various parts.

2. The hybrid flexible interconnect device with series compensation according to claim 1, characterized in that, The serial converter contains 3N sub-modules, namely sub-module a1, sub-module a2... sub-module a N Submodule b1, submodule b2... submodule b N Submodule c1, submodule c2... submodule c N Submodule a j T aj,2 Terminal and submodule a (j+1) T a(j+1),1 End connection, submodule a N T aN,2 The T terminal of phase A of the first AC port of the frequency converter transformer v11 End connection, submodule b j T bj,2 End and submodule b (j+1) T b(j+1),1 End connection, submodule b N T bN,2 The T terminal of phase B of the first AC port of the frequency converter transformer v12 End connection, submodule c j T cj,2 Terminal and submodule c (j+1) T c(j+1),1 End connection, submodule c N T cN,2 The T terminal of the first AC port C phase of the frequency converter transformer v13 The ends are connected, where j = 1 to N-1.

3. The hybrid flexible interconnect device with series compensation according to claim 1, characterized in that, T at the second AC port A phase of the frequency converter transformer v21 Terminal and switch S 2a T S2a1 The T phase of the second reactive harmonic compensation device a vc2a The terminals are connected, and the T-phase of phase B at the second AC port of the frequency converter transformer is connected. v22 Terminal and switch S 2b T S2b1 The T phase of the second reactive harmonic compensation device B phase vc2b The terminals are connected, and the T-phase of the second AC port C of the frequency converter transformer is connected. v23 Terminal and switch S 2c T S2c1 The T phase of the second reactive harmonic compensation device C phase vc2c The terminals are connected; the first AC port and the second AC port of the frequency converter can be respectively connected to the stator winding port and the rotor winding port of the frequency converter, or the first AC port and the second AC port of the frequency converter can be respectively connected to the rotor winding port and the stator winding port of the frequency converter.

4. The hybrid flexible interconnect device with series compensation according to claim 1, characterized in that, Submodule x k The circuit topology, x=a, b, c, k=1~N, includes: power semiconductor devices S xk1 Power semiconductor devices S xk2 Power semiconductor devices S xk3 Power semiconductor devices S xk4 Bypass switch S xk5 DC capacitor C xk Power semiconductor devices S xk1 collector and power semiconductor device S xk3 collector and DC capacitor C xk The positive terminal is connected to the power semiconductor device S. xk1 Emitter and power semiconductor device S xk2 collector and bypass switch S xk5 After the second terminal is connected, it becomes a submodule x k T xk,2 Terminal, power semiconductor device S xk3 Emitter and power semiconductor device S xk4 collector and bypass switch S xk5 After the first terminal is connected, it becomes a submodule x k T xk,1 Terminal, power semiconductor device S xk2 Emitter and power semiconductor device S xk4 emitter and DC capacitor C xk The negative terminal is connected.

5. A hybrid flexible interconnect device with series compensation according to claim 1, characterized in that, Switch S 1a T S1a1 Phase A of the first AC port of the hybrid flexible interconnect device is connected to phase A of the first AC power supply, and switch S 1a T S1a2 The T-terminal of the first reactive harmonic compensation device A phase vc1a Terminal, resistor R a T Ra1 Terminal and switch S pa T Spa1 Terminals connected, switch S 1b T S1b1 Phase B of the first AC port of the hybrid flexible interconnect device is connected to phase B of the first AC power supply, and switch S 1b T S1b2 The T-phase of the first reactive harmonic compensation device B is connected to the terminal. vc1b Terminal, resistor R b T Rb1 Terminal and switch S pb T Spb1 Terminals connected, switch S 1c T S1c1 The C phase of the first AC port of the hybrid flexible interconnect device is connected to the C phase of the first AC power supply, and the switch S 1c T S1c2 The T-phase of the first reactive harmonic compensation device C is connected to the terminal. vc1c Terminal, resistor R c T Rc1 Terminal and switch S pc T Spc1 The ends are connected.

6. A hybrid flexible interconnect device with series compensation according to claim 1, characterized in that, Switch S pa T Spa2 Terminal and resistor R a T Ra2 T of end and submodule a1 a1,1 Terminals connected, switch S pb T Spb2 Terminal and resistor R b T Rb2 T of end and submodule b1 b1,1 Terminals connected, switch S pc T Spc2 Terminal and resistor R c T Rc2 T of end and submodule c1 c1,1 The ends are connected.

7. A hybrid flexible interconnect device with series compensation according to claim 1, characterized in that, Switch S 2a T S2a2 The A phase of the second AC port of the hybrid flexible interconnect device is connected to the A phase of the second AC power supply, and switch S... 2b T S2b2 Phase B of the second AC port of the hybrid flexible interconnect device is connected to phase B of the second AC power supply, and switch S... 2c T S2c2 The C phase of the terminal, which serves as the second AC port of the hybrid flexible interconnect device, is connected to the C phase of the second AC power supply.

8. A hybrid flexible interconnect device with series compensation according to claim 1, characterized in that, The control and protection system includes at least one processor, multiple communication interfaces, and a memory communicatively connected to the processor. The memory contains instructions executable by the processor to implement a control strategy for the series-compensated hybrid flexible interconnect device. The first communication interface of the control and protection system is connected to the communication interface of the series converter; the second communication interface is connected to the communication interface of the frequency converter; the third communication interface is connected to the communication interface of the first reactive power harmonic compensation device; the fourth communication interface is connected to the communication interface of the second reactive power harmonic compensation device; and the fifth communication interface is connected to the switch S. 1a Switch S 1b Switch S 1c The communication interface is connected to the control and protection system's sixth communication interface and the switch S. 2a Switch S 2b Switch S 2c The communication interface is connected to the control and protection system's seventh communication interface and the switch S. pa Switch S pb Switch S pc The communication interface is connected.

Images