A static synchronous series compensation system and method

Abstract

A static synchronous series compensation system and method, the scheme includes: a primary circuit installed on a high potential platform and a secondary circuit installed in a control protection room; the high potential platform is connected with a power transmission line at the same potential; the primary circuit is connected in series with the power transmission line to compensate the voltage of the power transmission line; the secondary circuit is connected with the primary circuit, and compensation instructions are issued to the primary circuit according to the voltage loss value of the power transmission line. The static synchronous series compensation system in the scheme does not need a series transformer or only needs a low insulation grade series transformer, greatly reduces the insulation design difficulty of the series transformer, reduces the device cost, reduces the equipment weight, reduces the equipment cost, and greatly reduces the occupied area. In the scheme, the high potential platform is connected with the power transmission line at the same potential, and the primary circuit is installed on the high potential platform, which reduces the energy loss of the primary circuit caused by corona discharge and the electromagnetic interference of the adjacent equipment.

Description

Technical Field

[0001] This invention relates to the field of flexible AC power transmission technology, specifically to a static synchronous series compensation system and method. Background Technology

[0002] Currently, power supply and load are distributed in opposite directions. Large-scale centralized wind power development is located in remote areas with relatively light loads, making large-scale wind energy aggregation and transmission an inevitable choice. This leads to prominent transient and dynamic stability issues at weak transmission ends of the power grid and along long-distance transmission corridors, seriously threatening the safe and stable operation of regional power grids. To promote the transmission and consumption of new energy sources, it is urgent to study effective measures to improve system transmission capacity and enhance system stability.

[0003] Furthermore, with the rapid development of large and medium-sized cities, electricity load has increased dramatically, and long-distance transmission capacity has continuously expanded, placing higher demands on the power supply capacity of transmission lines. The land acquisition, demolition, and related social impacts associated with the construction of new transmission lines all pose challenges to transmission line construction. Therefore, improving the transmission capacity of existing transmission channels is of significant practical importance. On the other hand, 220kV and above power grids mostly use double-circuit lines for power supply. Due to uneven regional load distribution, some areas experience line overload. When one line is taken out of service, the other line will be overloaded due to the reduced wire diameter, resulting in the overall regional power supply capacity not being fully utilized. This not only affects the grid's economies of scale but also leads to power outages and curtailments, negatively impacting national economic development. Therefore, an effective power flow control method is urgently needed to improve the safety and stability of power grid operation.

[0004] To address the above technical requirements, the Static Synchronous Series Compensator (SSSC) offers an advanced and economical solution. Employing voltage source converter technology based on turn-off devices, the SSSC can be equivalent to a synchronous voltage source connected in series with the line. By injecting a voltage source orthogonal to the line current and with controllable amplitude, it alters the equivalent impedance of the transmission line. The SSSC features strong power flow control, fast response, and compensation capability unaffected by line current magnitude. Additional control damping can suppress power oscillations or subsynchronous oscillations. Using the SSSC allows for flexible control of line power flow, significantly improving the line's power transmission limit. Its rapid power control response and additional damping control better adapt to the randomness and volatility of renewable energy output, making it an effective means to increase the transmission capacity of weak-sending ends and long-distance transmission corridors, and enhance system safety and stability. Furthermore, the SSSC offers advantages such as capacitive and inductive bidirectional compensation, simple structure, and small footprint, making it suitable for large and medium-sized urban power grids with high requirements for operational flexibility, reliability, and space constraints. Under normal grid operation, the SSSC performs equivalent capacitive compensation on the lines, increasing the transmission capacity of the lines according to system needs. In the event of an N-1 fault, inductive compensation is performed, and the SSSC adjusts the power flow of the lines to avoid overload. During grid transients, the SSSC generates additional damping torque through control to suppress oscillations and improve grid stability. However, existing technologies connect the static synchronous series compensator to the system through a series transformer with a high insulation voltage level, resulting in low device integration, large footprint, high insulation cost, and low economic efficiency. Summary of the Invention

[0005] To address the problems of low integration and large footprint of existing technologies that connect static synchronous series compensators to the system via high insulation voltage level series transformers, this invention provides a static synchronous series compensation system and method.

[0006] The technical solution provided by this invention is:

[0007] A static synchronous series compensation system, the system comprising a primary circuit installed on a high-potential platform and a secondary circuit installed in a control and protection room;

[0008] The high-potential platform is equipotentially connected to the transmission line;

[0009] The primary circuit is connected in series in the transmission line to perform voltage compensation for the transmission line;

[0010] The secondary circuit is connected to the primary circuit, and a compensation command is issued to the primary circuit based on the voltage loss value of the transmission line.

[0011] Preferably, the primary circuit includes: multiple converter modules;

[0012] All converter modules are connected in series and then connected to the transmission line.

[0013] Preferably, the primary circuit further includes: a filter inductor;

[0014] All converter modules are connected in series and then connected to the transmission line through a filter inductor.

[0015] Preferably, the primary circuit further includes: a filter inductor and a plurality of low-insulation transformers, the same number as the converter modules;

[0016] The multiple low-insulation transformers are connected in series and then connected to the transmission line through a filter inductor;

[0017] Each converter module is coupled to a low-insulation transformer.

[0018] Preferably, the primary circuit further includes: a low-insulation transformer;

[0019] The converter modules are connected in series and then connected in parallel to the secondary side of the low-insulation transformer.

[0020] The primary side of the low-insulation transformer is connected in series in the transmission line.

[0021] Preferably, the converter module includes:

[0022] Two IGBT bridge arms, supporting capacitors, and mechanical switches;

[0023] The IGBT bridge arm is connected in parallel with the supporting capacitor, and the midpoint of the two IGBT bridge arms forms the output terminal.

[0024] The mechanical switch is connected in parallel between the output terminals to control the bypass or engagement of the ICBT bridge arm.

[0025] Preferably, the converter module further includes: two thyristors;

[0026] The two thyristors are connected in reverse parallel and then connected to the output terminal of the converter module to quickly bypass the IGBT bridge arm when the IGBT bridge arm fails.

[0027] Preferably, the primary circuit further includes: an instruction receiving unit;

[0028] The instruction receiving unit is connected to the mechanical switch and is used to control the on / off state of the mechanical switch according to the compensation instruction of the secondary circuit.

[0029] Preferably, the high-potential platform includes low-grade insulators;

[0030] The primary circuit is mounted on a high-potential platform supported by low-grade insulators.

[0031] A static synchronous series compensation method includes:

[0032] When the voltage of the transmission line is lost, the secondary circuit installed in the control and protection room formulates a compensation instruction based on the voltage loss value and sends it to the primary circuit installed on the high-potential platform.

[0033] The primary circuit performs voltage compensation on the transmission line that is equipotentially connected to the high-potential platform according to the compensation command.

[0034] Preferably, the secondary circuit installed in the control and protection room formulates compensation instructions based on the voltage loss value, including:

[0035] The secondary circuit determines the number of converter modules that need to be put into operation in the primary circuit based on the voltage loss value of the transmission line, and formulates compensation instructions.

[0036] Preferably, the primary circuit performs voltage compensation on the transmission line equipotentially connected to the high-potential platform according to the compensation command, including:

[0037] According to the compensation command, the signal receiving unit in the primary circuit controls the mechanical switch of the converter module in the primary circuit to close, thereby bypassing the IGBT bridge arm in the current converter module.

[0038] The converter modules put into use provide voltage compensation for transmission lines.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] The technical solution provided by this invention includes: a primary circuit installed on a high-potential platform and a secondary circuit installed in a control and protection room; the high-potential platform is equipotentially connected to the transmission line; the primary circuit is connected in series with the transmission line to compensate for the voltage of the transmission line; the secondary circuit is connected to the primary circuit and issues compensation commands to the primary circuit based on the voltage loss value of the transmission line. The static synchronous series compensation system in this solution requires no series transformer or only a low-insulation-class series transformer, significantly reducing the difficulty of insulation design for series transformers, lowering device costs, reducing equipment weight, lowering equipment price, and significantly reducing the footprint. In this solution, the high-potential platform is equipotentially connected to the transmission line, and the primary circuit is installed on the high-potential platform, reducing energy loss caused by corona discharge to the primary circuit and electromagnetic interference to nearby equipment. Attached Figure Description

[0041] Figure 1 This is a structural diagram of a static synchronous series compensation system according to the present invention;

[0042] Figure 2This is a connection structure diagram of Scheme 1 in the embodiments of the present invention;

[0043] Figure 3 This is a connection structure diagram of Scheme 2 in the embodiments of the present invention;

[0044] Figure 4 This is a connection structure diagram of Scheme 3 in the embodiments of the present invention; Detailed Implementation

[0045] To better understand this invention, the following description, in conjunction with the accompanying drawings and examples, will further illustrate the invention.

[0046] Example 1:

[0047] This embodiment provides a static synchronous series compensation system, installed in a substation. The system structure diagram is shown below. Figure 1 As shown, the primary circuit components are installed on the high-potential platform; the secondary components are installed in the control and protection room; the system also includes a cooling water machine and a heat exchanger, with the cooling water machine installed in the water-cooling room and the heat exchanger installed outdoors.

[0048] The primary circuit component has several possible configurations:

[0049] Option 1: Static synchronous series compensator without connected transformer.

[0050] This solution can be adopted when the system short-circuit capacity is small and when there are strict requirements for equipment footprint or cost control.

[0051] like Figure 2 As shown, the primary circuit consists of a filter inductor and N series-connected converter modules, directly connected to the transmission line. The filter inductor and series-connected converter modules are supported on a high-potential platform by low-insulation-class insulators. Each series-connected converter module is composed of an H-bridge circuit, the main components of which are two IGBT-based bridge arms connected in parallel with the supporting capacitor. The midpoint of the two bridge arms is the converter module output terminal. Thyristors are connected in anti-parallel between the converter module output terminals. Mechanical switches or contactors can also be optionally connected in parallel between the converter module output terminals. The converter module also incorporates an energy harvesting circuit and a module measurement, control, and protection unit, enabling line energy harvesting and control and protection of the circuit modules.

[0052] The H-bridge, which is the power element part of the converter, enables voltage output; the supporting capacitor provides DC support voltage for the converter; the anti-parallel thyristors enable rapid turn-on and bypass of the converter, allowing the converter to shut down when it fails; the mechanical switch or contactor enables reliable bypass of the converter; and the energy extraction circuit provides energy to the high-potential converter control, protection, and monitoring unit.

[0053] Option 2: Distributed static synchronous series compensator.

[0054] This solution can be adopted when the system short-circuit current is large and the size or weight of the device is strictly controlled.

[0055] like Figure 3 As shown, the primary circuit consists of an optional filter inductor and N converter modules connected to a low-insulation-class distributed transformer. The optional filter inductor is directly connected in series with the primary side of the distributed transformer to the transmission line. Each series-connected converter module is composed of an H-bridge circuit, the main components of which are two IGBT-based bridge arms connected in parallel with a supporting capacitor. The midpoint of the two bridge arms is the converter module output terminal. Thyristors are connected in anti-parallel between the converter module output terminals. Optional parallel mechanical switches or contactors can also be connected between the converter module output terminals. The converter module output terminal is connected in parallel with the secondary side of the distributed transformer. The converter module also includes an energy harvesting circuit and a module measurement, control, and protection unit, enabling line energy harvesting and control and protection of the circuit modules.

[0056] Option 3: Connect the series transformer to the static synchronous series compensator.

[0057] This solution can be adopted when the system short-circuit current is large and the size or weight of the device is not strictly controlled.

[0058] like Figure 4 As shown, the primary circuit consists of a low-insulation-class series transformer and N series-connected converter modules. The primary side of the low-insulation-class series transformer is directly connected in series to the transmission line. Each series-connected converter module is composed of an H-bridge circuit, the main components of which are two IGBT-based bridge arms connected in parallel with the supporting capacitor. The midpoint of the two bridge arms is the output terminal of the converter module. Thyristors are connected in anti-parallel between the output terminals of the converter modules. Mechanical switches or contactors can also be optionally connected in parallel between the output terminals of the converter modules. After N converter modules are connected in series, their output terminals are connected in parallel with the secondary side of the low-insulation-class series transformer. The converter module also includes an energy harvesting circuit and a module measurement, control, and protection unit, which can realize line energy harvesting and control and protection of the circuit module.

[0059] The control, protection, and monitoring electronic circuits of the secondary and primary components of the static synchronous series compensator based on the high-potential platform structure communicate via optical fiber. If the converter valve is water-cooled, the water distribution pipeline of the converter valve is led down from the high-potential platform to the water turbine and heat exchanger through insulated water pipes. Insulation materials such as PVDF and PPR can be selected.

[0060] Example 2:

[0061] This embodiment provides a static synchronous series compensation system, including: a primary circuit installed on a high-potential platform and a secondary circuit installed in a control and protection room;

[0062] The high-potential platform is equipotentially connected to the transmission line;

[0063] The primary circuit is connected in series in the transmission line to perform voltage compensation for the transmission line;

[0064] The secondary circuit is connected to the primary circuit, and a compensation command is issued to the primary circuit based on the voltage loss value of the transmission line.

[0065] The primary circuit includes: multiple converter modules;

[0066] All converter modules are connected in series and then connected to the transmission line.

[0067] The primary circuit also includes: a filter inductor;

[0068] All converter modules are connected in series and then connected to the transmission line through a filter inductor.

[0069] The primary circuit also includes: a filter inductor and a plurality of low-insulation transformers, the same number as the converter module;

[0070] The multiple low-insulation transformers are connected in series and then connected to the transmission line through a filter inductor;

[0071] Each converter module is coupled to a low-insulation transformer.

[0072] The primary circuit also includes: a low-insulation transformer;

[0073] The converter modules are connected in series and then connected in parallel to the secondary side of the low-insulation transformer.

[0074] The primary side of the low-insulation transformer is connected in series in the transmission line.

[0075] The converter module includes:

[0076] Two IGBT bridge arms, supporting capacitors, and mechanical switches;

[0077] The IGBT bridge arm is connected in parallel with the supporting capacitor, and the midpoint of the two IGBT bridge arms forms the output terminal.

[0078] The mechanical switch is connected in parallel between the output terminals to control the bypass or engagement of the ICBT bridge arm.

[0079] The converter module also includes: two thyristors;

[0080] The two thyristors are connected in reverse parallel and then connected to the output terminal of the converter module to quickly bypass the IGBT bridge arm when the IGBT bridge arm fails.

[0081] The primary circuit further includes: an instruction receiving unit;

[0082] The instruction receiving unit is connected to the mechanical switch and is used to control the on / off state of the mechanical switch according to the compensation instruction of the secondary circuit.

[0083] The high-potential platform includes low-grade insulators;

[0084] The primary circuit is mounted on a high-potential platform supported by low-grade insulators.

[0085] Example 3:

[0086] This embodiment provides a static synchronous series compensation method, including:

[0087] When the voltage of the transmission line is lost, the secondary circuit installed in the control and protection room formulates a compensation instruction based on the voltage loss value and sends it to the primary circuit installed on the high-potential platform.

[0088] The primary circuit performs voltage compensation on the transmission line that is equipotentially connected to the high-potential platform according to the compensation command.

[0089] The secondary circuit installed in the control and protection room generates compensation instructions based on the voltage loss value, including:

[0090] The secondary circuit determines the number of converter modules that need to be put into operation in the primary circuit based on the voltage loss value of the transmission line, and formulates compensation instructions.

[0091] The primary circuit performs voltage compensation on the transmission line equipotentially connected to the high-potential platform according to the compensation command, including:

[0092] According to the compensation command, the signal receiving unit in the primary circuit controls the mechanical switch of the converter module in the primary circuit to close, thereby bypassing the IGBT bridge arm in the current converter module.

[0093] The converter modules put into use provide voltage compensation for transmission lines.

[0094] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0095] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0096] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0097] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0098] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0099] 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 method of static synchronous series compensation, characterized by, The application relates to a static synchronous series compensation method and a static synchronous series compensation system. When the voltage of a power transmission line is lost, a secondary circuit installed in a control protection room formulates a compensation instruction according to the voltage loss value and sends the compensation instruction to a primary circuit installed on a high potential platform; The primary circuit compensates the voltage of the power transmission line connected to the high potential platform according to the compensation instruction; The static synchronous series compensation system involved in the static synchronous series compensation method comprises a primary circuit installed on a high potential platform and a secondary circuit installed in a control protection room; The high potential platform is connected to the power transmission line in an equipotential manner; The primary circuit is connected in series to the power transmission line to compensate the voltage of the power transmission line; The secondary circuit is connected to the primary circuit and sends a compensation instruction to the primary circuit according to the voltage loss value of the power transmission line; The primary circuit comprises a plurality of converter modules; All the converter modules are connected in series and then connected to the power transmission line; or The primary circuit further comprises a filter inductor; All the converter modules are connected in series and then connected to the power transmission line through the filter inductor; or The primary circuit further comprises a filter inductor and a plurality of low insulation transformers with the same number as the converter modules; The plurality of low insulation transformers are connected in series and then connected to the power transmission line through the filter inductor; Each converter module is coupled to a low insulation transformer; The converter module comprises: two IGBT bridge arms, a support capacitor and a mechanical switch; The IGBT bridge arms are connected in parallel to the support capacitor, and the midpoints of the two IGBT bridge arms form output ends; The mechanical switch is connected in parallel between the output ends and is used for controlling the bypass or input of the IGBT bridge arms.

2. The method of claim 1, wherein, The primary circuit further comprises a low insulation transformer; The converter modules are connected in series and then connected in parallel to the secondary side of the low insulation transformer; The primary side of the low insulation transformer is connected in series to the power transmission line.

3. The method of claim 1, wherein, The converter module further comprises two thyristors; The two thyristors are connected in reverse parallel and then connected in parallel to the output ends of the converter module, and are used for quickly bypassing the IGBT bridge arms when the IGBT bridge arms are faulty.

4. The method of claim 1, wherein, The primary circuit further comprises an instruction receiving unit; The instruction receiving unit is connected to the mechanical switch and is used for controlling the on-off of the mechanical switch according to the compensation instruction of the secondary circuit.

5. The method of claim 1, wherein, The high potential platform comprises a low-grade insulator; The primary circuit is supported and installed on the high potential platform through the low-grade insulator.

6. The method of claim 1, wherein, The secondary circuit installed in the control protection room formulates a compensation instruction according to the voltage loss value, and the method comprises the following steps: The secondary circuit determines the number of converter modules to be input in the primary circuit according to the voltage loss value of the power transmission line, and formulates a compensation instruction.

7. The method of claim 1, wherein, The primary circuit compensates the voltage of the power transmission line connected to the high potential platform according to the compensation instruction, and the method comprises the following steps: The signal receiving unit of the primary circuit controls the mechanical switch of the converter module according to the compensation instruction, bypasses the IGBT bridge arms in the current converter module, and inputs the converter module into use. The converter module in use compensates the voltage of the power transmission line.

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