Test circuit and test method for distributed static synchronous series compensator

Abstract

The invention relates to a test circuit and a test method for a distributed static synchronous series compensator, and the test circuit enables the steady-state current of a test power supply, a rectification circuit, a controllable voltage source, a transformer and a current-limiting reactor simulation line to be continuous, accurate and adjustable through switching on or switching off a circuit breaker, a high-speed switch and a high-speed bypass switch, and the test power supply is low in capacity. The method has the advantages that different states of the distributed static synchronous series compensator can be tested, the sub-modules of the distributed static synchronous series compensator can be tested in batches at the same time, the test efficiency is high, the technical economy is prominent, a high-capacity test power supply is not needed, and the test cost is low. All sub-modules of the distributed static synchronous series compensator can be tested at the same time under the laboratory condition.

Description

Technical Field

[0001] This invention relates to the field of flexible AC power transmission technology, specifically to a test circuit and test method for a distributed static synchronous series compensator. Background Technology

[0002] The construction of a new power system with new energy as the main body and the gradual formation of a main grid structure with ultra-high voltage power grid as the core and 750kV and 500kV as the backbone. However, the distribution of new energy resources and demand is inverse. The new energy developed in a concentrated manner is mostly located in remote areas with light loads, while the energy consumption of load centers continues to grow. In addition, a large number of local thermal power units continue to decline, further strengthening the dependence on power supply from outside the region. It is necessary to collect and transmit new energy over long distances to achieve larger-scale new energy optimization. The collection and transmission of new energy over long distances has significantly improved the power exchange level between regional power grids and provincial power grids, but there are also the following major problems: (1) The power grid structure and operation mode are becoming more complex. Factors such as fluctuations in new energy output have led to extremely uneven power flow distribution within some provincial power grids, and power flow control problems are particularly prominent. (2) Under the “N-1” and “N-2” modes, the power flow redistribution of lines within the power grid is such that some lines are overloaded, overloaded, or even close to / exceed the stability limit, posing a great risk to the safe operation of the power grid. (3) The dynamic stability problems of weak power transmission ends and long-distance transmission corridors are prominent.

[0003] Improving power flow control and optimizing power flow distribution are also key to ensuring the safe and efficient operation of the power grid and solving the above problems. Among existing technologies, building new power plants and transmission lines requires a large amount of valuable land resources, resulting in high construction costs and long construction periods. Solving local power flow overload problems is costly and difficult to implement in urban power grids. Traditional power flow control methods such as generation regulation and load transfer are slow and ineffective, and cannot meet the actual needs of fast, flexible, and precise power flow control in some situations. Controllable series capacitor compensators (TCSCs) have an uncontrollable resonant region, and impedance control is discontinuous, generally operating only in the capacitive region. Unified power flow controllers (UPFCs) take into account both voltage and power flow regulation objectives, adopting a series and parallel dual converter structure, which has a complex electrical structure, a large number of converter modules, a large footprint, and high investment. Controllable phase shifters (PSTs) switch transformer windings during control, and the transformer inrush current caused by sudden voltage changes in the windings can cause certain impacts on the controllable phase shifters and the transmission system. Centralized static synchronous series compensators (SSSCs) in existing projects use series transformers for connection, which increases the footprint and cost of the equipment. The centralized control of each sub-module is not suitable for multi-objective coordination. The Direct Series Distributed Static Synchronous Series Compensator (DSSC) is a type of distributed power flow controller (DPFC) that features miniaturization, modularity, portability, easy expansion, and low cost. It can be installed in a distributed manner, with each submodule controlled independently, and represents the future development direction of power flow control technology. Summary of the Invention

[0004] To address the shortcomings of existing technologies in testing distributed static synchronous series compensators (PSCs), such as insufficient verification of module functions and low verification efficiency, this invention proposes a test circuit for a PSC. The test circuit includes: a test power supply, a rectifier circuit, a controllable voltage source, a transformer, a current-limiting reactor, a circuit breaker, a fast switch, a fast bypass switch, and a compensator under test, wherein the compensator under test is a distributed static synchronous series compensator. The test power supply is connected to the AC side of the rectifier circuit and the three-phase terminals of the transformer. The DC side of the rectifier circuit is connected to the DC side of the controllable voltage source. The AC side of the controllable voltage source is connected to the input terminal of the circuit breaker. The first output terminal of the circuit breaker is connected to the first terminal of the fast bypass switch, the first terminal of the current-limiting reactor, and the first output terminal of the fast switch; the second output terminal of the circuit breaker is connected to the second terminal of the fast bypass switch and the first terminal of the compensator to be tested. The two-phase terminals of the transformer are connected to the input terminal of the fast switch, and the second output terminal of the fast switch is connected to the second terminal of the current-limiting reactor and the second terminal of the compensator under test.

[0005] Optionally, the test circuit further includes: a test controller; The test controller is connected to the circuit breaker, the fast switch, the fast bypass switch, the controllable voltage source, and the compensator under test, respectively. The test controller is used to control the circuit breaker, the fast switch, the fast bypass switch, the controllable voltage source, and the compensator under test based on the received test signal to be tested, to obtain the output voltage of the compensator under test, to determine the operating state of the compensator under test based on the output voltage of the compensator under test, and to realize the test of the compensator under test.

[0006] Optionally, the compensator under test includes: multiple sub-modules connected in series, each sub-module including: a current sensor, a voltage source converter, a DC-side capacitor and a bypass switch; The DC side of the voltage source converter is connected in parallel with the DC side capacitor, the AC side of the voltage source converter is connected in parallel with the bypass switch, and the current sensor is provided on the AC side of the voltage source converter. The test controller is connected to the bypass switch, current sensor and voltage source converter in each submodule respectively; The test controller is specifically used to control the bypass switch to close based on the received start-up test signal. The current-limiting reactor and the bypass switch form a start-up circuit. The controller controls the rectifier circuit and the controllable voltage source to unlock, so that the controllable voltage source outputs an AC voltage of a preset amplitude. When the current in the start-up circuit collected by the current sensor reaches the start-up current, the controller controls all bypass switches to open and all voltage source converters to unlock. When the output voltage of the test compensator reaches a first preset voltage threshold, the controller determines that each sub-module in the test compensator is in the working state, thereby realizing the start-up test of the compensator under test.

[0007] Optionally, the test controller is specifically configured to, when the compensator under test is in the activated state, if a steady-state operation test signal is received, adjust the output voltage modulation ratio of the compensator under test to the maximum according to a preset steady-state operation strategy based on the AC current phase detected by the current sensor, thereby obtaining the voltage output capability of the compensator under test, and adjust the AC voltage amplitude output by the controllable voltage source according to a preset adjustment method, determine the current of each sub-module, determine the electrical parameters of each sub-module when the current of each sub-module is greater than or equal to the rated current of the sub-module, determine the overload parameters of each sub-module within a preset time when the current of each sub-module is greater than or equal to the overload current of the sub-module, and perform a steady-state operation test on the compensator under test based on the voltage output capability of the compensator under test, the electrical parameters of each sub-module, and the overload parameters of each sub-module within a preset time.

[0008] Optionally, the test controller is specifically used for: Based on the phase of the AC current detected by the current sensor, the output voltage modulation ratio of the compensator under test is controlled to achieve the same output voltage amplitude for each sub-module in the compensator under test. The output voltage of each sub-module is controlled to be at 90° with the AC current of each sub-module, and the output voltage phase of some sub-modules leads the AC current, while the output voltage phase of other sub-modules lags behind the AC current.

[0009] Optionally, the number n of sub-modules in the compensator under test is an even number, and all sub-modules are divided into two parts: sub-modules whose output voltage phase leads the AC current and sub-modules whose output voltage phase lags the AC current. The number of sub-modules n in the compensator under test is odd. (n+1) / 2 sub-modules are used as sub-modules whose output voltage phase leads the AC current, and (n-1) / 2 sub-modules are used as sub-modules whose output voltage phase lags the AC current.

[0010] Optionally, each submodule further includes: a bidirectional bypass thyristor valve, wherein the bidirectional bypass thyristor valve is connected in parallel with the AC side of the voltage source converter; The test controller is also connected to the bidirectional bypass thyristor valve in each submodule; The test controller is specifically used to, when the compensator under test is in the engaged state, based on the received exit test signal and according to a preset exit strategy, control the AC voltage amplitude output by the controllable voltage source, control all bidirectional bypass thyristor valves to open when the current in each sub-module is less than the exit current, control all voltage source converters to lock out, and control all bidirectional bypass thyristor valves to open and all bypass switches to open after all voltage source converters are locked out, so that each sub-module in the test compensator is in the exit state, thereby realizing the exit test of the compensator under test.

[0011] Optionally, the test controller is specifically configured to, when the compensator under test is in steady-state operation, if a simulated short-circuit test signal is received, control the fast bypass switch and the fast switch to close, control the controllable voltage source to lock out, and when the short-circuit current amplitude detected by the current sensor reaches a preset current amplitude, control the bidirectional bypass thyristor valve and the bypass switch to close, causing the compensator under test to exit, control the fast switch to open after a first delay to disconnect the short-circuit circuit, control the fast bypass switch to open after a second delay to unlock the controllable voltage source, and control the bypass switch to open after a third delay to unlock the compensator under test after the DC side voltage of all voltage source converters is established, thus restoring the compensator under test to its operating state.

[0012] Optionally, the test controller is further configured to, when the compensator under test is running in a steady state, determine the internal fault type of the compensator under test based on the received fault simulation signal, and control the circuit breaker, the fast switch, the fast bypass switch, the controllable voltage source and the compensator under test based on the internal fault type of the compensator under test, so as to realize the internal fault test of the compensator under test.

[0013] Optionally, the test controller is specifically used to control the drive pulse lockout of the faulty submodule in the compensator under test when the internal fault type is a submodule communication fault or a voltage source converter fault, control the closing of the bidirectional bypass thyristor valve and the bypass switch, and enable the faulty submodule to bypass and run, thereby realizing the internal fault test of the compensator under test.

[0014] Optionally, the test controller is specifically used to monitor the temperature of the compensator under test when the internal fault type is a cooling fan fault, and to derating the output voltage of the compensator under test when the temperature of the compensator under test is greater than or equal to a preset temperature threshold.

[0015] Optionally, the test controller is specifically used to control the drive pulse lockout of the faulty submodule in the compensator under test, control the bypass switch to close, and allow the faulty submodule to operate in bypass mode when the internal fault type is the bidirectional bypass thyristor valve; and to control the drive pulse lockout of the faulty submodule in the compensator under test, control the bidirectional bypass thyristor valve to close, and allow the faulty submodule to operate in bypass mode when the internal fault type is the bypass switch.

[0016] Based on the same inventive concept, the present invention also proposes an experimental method, the method comprising: Based on the received test signal, the circuit breaker, fast switch, fast bypass switch, controllable voltage source and compensator under test are controlled to obtain the output voltage of the compensator under test. Based on the output voltage of the compensator under test, the operating state of the compensator under test is determined, and the test of the compensator under test is realized.

[0017] Optionally, the test signal to be tested is a test start signal; The process of controlling the circuit breaker, fast switch, fast bypass switch, controllable voltage source, and compensator under test based on the received test signal to obtain the output voltage of the compensator under test includes: Based on the start-up test signal, the bypass switch is closed, the current-limiting reactor and the bypass switch form a start-up circuit, the rectifier circuit and the controllable voltage source are unlocked, so that the controllable voltage source outputs an AC voltage of a preset amplitude; When the current in the starting circuit reaches the starting current, all bypass switches are opened and the voltage source converter is unlocked to obtain the output voltage of the compensator under test.

[0018] Optionally, determining the operating state of the compensator under test based on its output voltage includes: When the output voltage of the test compensator reaches the first preset voltage threshold, each sub-module in the test compensator is determined to be in the activated state, thereby enabling the start-up test of the compensator to be tested.

[0019] Optionally, after determining that each submodule in the test compensator is in an engaged state, the method further includes: Upon receiving a steady-state operation test signal, based on the AC current phase detected by the current sensor, the output voltage modulation ratio of the compensator under test is adjusted to the maximum according to a preset steady-state operation strategy to obtain the voltage output capability of the compensator under test. According to the preset adjustment method, the amplitude of the AC voltage output by the controllable voltage source is adjusted to determine the current of each sub-module; When the current of each submodule is greater than or equal to the rated current of the submodule, determine the electrical parameters of each submodule; When the current of each submodule is greater than or equal to the overload current of the submodule, determine the overload parameters of each submodule within a preset time. Based on the voltage output capability of the compensator under test, the electrical parameters of each submodule, and the overload parameters of each submodule within a preset time, a steady-state operation test is conducted on the compensator under test.

[0020] Optionally, after determining that each submodule in the test compensator is in an engaged state, the method further includes: Upon receiving a simulated short-circuit test signal, the system controls the fast bypass switch and the fast switch to close, and controls the controllable voltage source to lock out. When the short-circuit current amplitude detected by the current sensor reaches the preset current amplitude, the system controls the bidirectional bypass thyristor valve and the bypass switch to close, causing the compensator under test to exit. After a first delay, the system controls the fast switch to open, disconnecting the short-circuit circuit. After a second delay, the system controls the fast bypass switch to open, and controls the controllable voltage source to unlock. After a third delay, the system controls the bypass switch to open, and controls all voltage source converters to unlock after the DC side voltage is established, allowing the compensator under test to resume operation.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a test circuit and test method for a distributed static synchronous series compensator. The test circuit, by turning on or off circuit breakers, fast switches, and fast bypass switches, enables the test power supply, rectifier circuit, controllable voltage source, transformer, and current-limiting reactor to continuously and precisely adjust the steady-state current of the simulated line. It has advantages such as low test power supply capacity, the ability to test different states of the distributed static synchronous series compensator, and the ability to simultaneously test sub-modules of the distributed static synchronous series compensator in batches. It has high testing efficiency, outstanding technical and economic benefits, and eliminates the need for a large-capacity test power supply, enabling simultaneous testing of all sub-modules of the distributed static synchronous series compensator under laboratory conditions.

[0022] The present invention provides a test method that controls a circuit breaker, a fast switch, a fast bypass switch, a controllable voltage source, and a compensator under test by receiving a test signal to be tested, thereby obtaining the output voltage of the compensator under test and determining the operating state of the compensator under test, thus realizing the testing of different states of a distributed static synchronous series compensator. Attached Figure Description

[0023] Figure 1 A schematic diagram of a test circuit for a distributed static synchronous series compensator provided by the present invention; Figure 2 A schematic diagram of a distributed static synchronous series compensator submodule provided by the present invention; Figure 3 This is a schematic diagram of a test circuit for a distributed static synchronous compensator module provided by the present invention. Detailed Implementation

[0024] Example 1: Figure 1 A schematic diagram of a test circuit for a distributed static synchronous series compensator provided by the present invention is shown below. Figure 1 As shown, the test circuit includes: a test power supply, a rectifier circuit, a controllable voltage source, a transformer, a current-limiting reactor, a circuit breaker Ka, a fast switch Kb, a fast bypass switch Kc, and a compensator under test, wherein the compensator under test is a distributed static synchronous series compensator; the test power supply is connected to the AC side of the rectifier circuit and the three-phase terminals of the transformer; the DC side of the rectifier circuit is connected to the DC side of the controllable voltage source; the AC side of the controllable voltage source is connected to the input terminal of the circuit breaker Ka; the first output terminal of the circuit breaker Ka is connected to the first terminal of the fast bypass switch Kc, the first terminal of the current-limiting reactor, and the first output terminal of the fast switch Kb; the second output terminal of the circuit breaker Ka is connected to the second terminal of the fast bypass switch Kc and the first terminal of the compensator under test; the two-phase terminals of the transformer are connected to the input terminal of the fast switch Kb; the second output terminal of the fast switch Kb is connected to the second terminal of the current-limiting reactor and the second terminal of the compensator under test.

[0025] The rectifier circuit can be a full-bridge rectifier circuit or a half-bridge rectifier circuit. The fast switch Kb can be a mechanical switch, such as a relay, or an electronic switching device. The fast bypass switch Kc can be a pair of reverse parallel thyristors. In some scenarios, the compensator under test can also be referred to as a test sample submodule, test sample module, or test sample module.

[0026] It should be noted that in some scenarios, the test circuit for distributed static synchronous series compensators (PSCs) is also referred to as the laboratory simulation test circuit for distributed static synchronous compensators modules, or the test circuit for distributed static synchronous compensators modules. Each module of the distributed static synchronous series compensator is directly connected in series with each phase of the transmission line, and its main module circuit is as follows: Figure 2 As shown, the main components include DC-side capacitor C, voltage-sourced converter (VSC), choke reactor L, bidirectional bypass thyristor valve SCR, bypass switch K, surge arrester MOV, current sensor CT, etc. Optional components such as AC port filter F can also be configured as needed. The DC-side capacitor (which can be a film capacitor, electrolytic capacitor, or supercapacitor) is connected in parallel on the DC side of the voltage source converter AC / DC (VSC) to provide stable voltage support for the VSC. A choke reactor L is connected in series on the AC side of the VSC to suppress the di / dt of the thyristor during conduction, limit the overcurrent level of internal components during line lightning strikes, and raise the port voltage under system short-circuit fault conditions to force trigger the bypass bidirectional bypass thyristor valve SCR for overvoltage protection of the module. It can also be used for filtering the output voltage of the VSC AC / DC. A bidirectional bypass thyristor valve SCR is connected in parallel at the module's AC port to achieve rapid bypass of a single module, temporarily bearing the system short-circuit current. A bypass switch K is connected in parallel at the module's AC port, working in conjunction with the bidirectional bypass thyristor valve SCR to achieve reliable bypass protection for a single module. A surge arrester MOV is connected in parallel at the module's AC port to achieve overvoltage protection of the module. A current sensor CT is connected in series at the port to measure the line current for related control, protection, and line power extraction. In addition, the module's AC port can be configured with filter F to achieve AC / DC (VSC) output voltage filtering for the voltage source converter.

[0027] Since each module of the distributed static synchronous series compensator draws energy from AC current, and its ports are connected in parallel with fast switches and anti-parallel thyristor valves, the timing of the activation and deactivation control is complex. Existing technologies have failed to complete the verification of all steady-state and transient functions of the distributed static synchronous series compensator under laboratory conditions, resulting in insufficient verification of module functions and low verification efficiency.

[0028] To address the aforementioned issues, this invention proposes a laboratory simulation test circuit and method for distributed static synchronous compensators (PSCs), which eliminates the need for a large-capacity test power supply and enables simultaneous verification of all functions of multiple modules of the distributed static synchronous series compensator under laboratory conditions.

[0029] For example, the experimental circuit of the distributed static synchronous compensator module is as follows: Figure 3As shown, the system comprises a test power supply S, a rectifier circuit AC / DC (D), a controllable voltage source DC / AC (CVS), a transformer T, a current-limiting reactor L0, a circuit breaker Ka, a fast switch Kb, a fast bypass switch Kc, test specimen modules (SM1~SMn), a test controller, and connecting conductors. The fast bypass switch Kc is composed of bidirectional fully or semi-controlled devices (such as IGBTs, IGCTs, IEGTs, thyristors, etc.). The test specimen modules (SM1~SMn) include current sensors (CT1~CTn), surge arresters (MOV1~MOVn), bypass switches (K1~Kn), bypass thyristor valves (SCR1~SCRn), filters (F1~Fn), choke reactors (L1~Ln), voltage source converter AC / DC (VSC1~VSCn), and DC-side capacitors (C1~Cn).

[0030] The connection method of the test circuit for the distributed static synchronous compensator module is as follows: a) The three-phase small-capacity test power supply S is connected to the AC side of the rectifier circuit AC / DC (D). The DC voltage is obtained through three-phase rectification and then connected to the DC side of the controllable voltage source DC / AC (CVS). The output AC voltage with controllable amplitude is connected in series with the circuit breaker Ka, the current limiting reactor L0, and the output terminal of the test sample module (SM1~SMn).

[0031] b) The three-phase small-capacity test power supply S is connected to the three-phase terminals of the Scott transformer T. The single-phase terminal of the Scott transformer T is connected in series with the circuit breaker Ka and then in parallel with the current-limiting reactor L0.

[0032] c) A fast bypass switch Kc is connected in parallel to the output terminal of circuit breaker Ka.

[0033] Optionally, the test circuit further includes: a test controller; the test controller is connected to the circuit breaker, the fast switch, the fast bypass switch, the controllable voltage source, and the compensator under test, respectively; the test controller is used to control the circuit breaker, the fast switch, the fast bypass switch, the controllable voltage source, and the compensator under test based on the received test signal to be tested, to obtain the output voltage of the compensator under test, and to determine the operating state of the compensator under test based on the output voltage of the compensator under test, thereby realizing the test of the compensator under test.

[0034] Optionally, the compensator under test includes: multiple sub-modules connected in series, each sub-module including: a current sensor, a voltage source converter, a DC-side capacitor, and a bypass switch; the DC side of the voltage source converter is connected in parallel with the DC-side capacitor, the AC side of the voltage source converter is connected in parallel with the bypass switch, and the current sensor is provided on the AC side of the voltage source converter; the test controller is connected to the bypass switch, the current sensor, and the voltage source converter in each sub-module respectively; the test controller is specifically used to control the bypass switch to close based on the received start-up test signal, the current-limiting reactor and the bypass switch to form a start-up circuit, control the rectifier circuit and the controllable voltage source to unlock, so that the controllable voltage source outputs an AC voltage of a preset amplitude, when the current in the start-up circuit collected by the current sensor reaches the start-up current, control all bypass switches to open, control all voltage source converters to unlock, and when the output voltage of the test compensator reaches a first preset voltage threshold, determine that each sub-module in the test compensator is in the activated state, thereby realizing the start-up test of the compensator under test.

[0035] For example, 1) Each test sample module (SM1~SMn) is not powered on and is in the initial state, and its internal bypass switch (K1~Kn) is in the closed state.

[0036] 2) Disconnect the fast switch Kb, disconnect the fast bypass switch Kc, close the circuit breaker Ka, unlock (receive the unlock signal, start) the rectifier circuit AC / DC (D) to establish DC voltage, unlock the controllable voltage source DC / AC (CVS), the controllable voltage source DC / AC (CVS) outputs a low amplitude AC voltage, and flows through the circuit formed by the current limiting reactor L0 and the bypass switch (K1~Kn) with a current lower than the module starting current Iqd. At this time, each test sample module (SM1~SMn) does not start.

[0037] 3) Gradually increase the AC voltage amplitude output by the controllable voltage source DC / AC (CVS). When the current flowing through each module reaches the starting current Iqd, each test sample module (SM1~SMn) starts according to the preset logic. That is, the current sensor (CT1~CTn) realizes the line current energy extraction, the bypass switch (K1~Kn) is opened, and the DC side voltage of the voltage source converter AC / DC (VSC1~VSCn) of each module is gradually established and then unlocked. Each test sample module (SM1~SMn) can output voltage according to the preset command to complete the module start-up. Each test sample module (SM1~SMn) is in the working state.

[0038] Optionally, the test controller is specifically configured to, when the compensator under test is in the activated state, if a steady-state operation test signal is received, adjust the output voltage modulation ratio of the compensator under test to the maximum according to a preset steady-state operation strategy based on the AC current phase detected by the current sensor, thereby obtaining the voltage output capability of the compensator under test, and adjust the AC voltage amplitude output by the controllable voltage source according to a preset adjustment method, determine the current of each sub-module, determine the electrical parameters of each sub-module when the current of each sub-module is greater than or equal to the rated current of the sub-module, determine the overload parameters of each sub-module within a preset time when the current of each sub-module is greater than or equal to the overload current of the sub-module, and perform a steady-state operation test on the compensator under test based on the voltage output capability of the compensator under test, the electrical parameters of each sub-module, and the overload parameters of each sub-module within a preset time.

[0039] It should be noted that the test controller is specifically used to: control the output voltage modulation ratio of the compensator under test based on the phase of the AC current detected by the current sensor, so as to achieve the same output voltage amplitude for each sub-module in the compensator under test, control the output voltage of each sub-module to be at 90° with the AC current of each sub-module, and the output voltage phase of some sub-modules leads the AC current, while the output voltage phase of other sub-modules lags behind the AC current.

[0040] Wherein, the number n of sub-modules in the compensator under test is even, and all sub-modules are divided into two parts: sub-modules whose output voltage phase leads the AC current and sub-modules whose output voltage phase lags the AC current; where the number n of sub-modules in the compensator under test is odd, (n+1) / 2 sub-modules are designated as sub-modules whose output voltage phase leads the AC current, and (n-1) / 2 sub-modules are designated as sub-modules whose output voltage phase lags the AC current.

[0041] For example, 1) each test sample module (SM1~SMn) is in the input state, the bypass switch (K1~Kn) is opened, the start-up is completed, and the voltage can be output according to the preset command.

[0042] 2) Each test sample module (SM1~SMn) detects the phase of the AC current through the current sensor CT and controls the output voltage modulation ratio of each test sample module so that the output voltage amplitude of each test sample module is the same and is at 90° with the AC current.

[0043] If the number of test modules n is even, let the output voltage of n / 2 modules lead the current phase, and the output voltage of the other n / 2 modules lag the current phase. For example, set the output voltage of the 1st to n / 2nd modules to lead the current phase, and the output voltage of the (n / 2+1)th to nth modules to lag the current phase.

[0044] If the number of test modules n is odd, let the output voltage of (n+1) / 2 modules lead the current phase, and the output voltage of (n-1) / 2 modules lag the current phase. For example, set the output voltage of the 1st to (n+1) / 2nd modules to lead the current phase, and the output voltage of the (n+3) / 2nd to nth modules to lag the current phase.

[0045] 3) Gradually increase the modulation ratio of each module to the maximum to verify the module's voltage output capability.

[0046] 4) Gradually increase the AC voltage amplitude output by the controllable voltage source DC / AC (CVS). When the current flowing through each module reaches the rated current Ied, continuously evaluate the rated power output capability, power quality, electromagnetic compatibility, temperature rise, noise and other technical indicators of each module.

[0047] 5) Continue to increase the AC voltage amplitude output by the controllable voltage source DC / AC (CVS). When the current flowing through each module reaches the overload current Igz, test the overload capacity of each module within a specified time.

[0048] Optionally, each submodule further includes: a bidirectional bypass thyristor valve, wherein the bidirectional bypass thyristor valve is connected in parallel with the AC side of the voltage source converter; the test controller is also connected to the bidirectional bypass thyristor valve in each submodule; the test controller is specifically used to control the AC voltage amplitude output by the controllable voltage source according to a preset exit strategy based on the received exit test signal when the compensator under test is in the engaged state; when the current in each submodule is less than the exit current, control all bidirectional bypass thyristor valves to be turned on and control all voltage source converters to be locked; after all voltage source converters are locked, control all bidirectional bypass thyristor valves to be turned off and all bypass switches to be turned on, so that each submodule in the test compensator is in the exit state, thereby realizing the exit test of the compensator under test.

[0049] For example, 1) each test sample module (SM1~SMn) is in the input state, the bypass switch (K1~Kn) is opened, the start-up is completed, and the voltage can be output according to the preset command.

[0050] 2) Gradually reduce the AC voltage amplitude output by the controllable voltage source DC / AC (CVS). When the current flowing through each module is lower than the exit current Itc, each test sample module (SM1~SMn) will activate the bidirectional bypass thyristor valve (SCR1~SCRn) according to the preset logic, the voltage source converter AC / DC (VSC1~VSCn) will be locked, the bypass switch (K1~Kn) will be closed, and the triggering of the bypass thyristor valve (SCR1~SCRn) will be stopped, thus realizing the module exit.

[0051] Optionally, the test controller is specifically configured to, when the compensator under test is in steady-state operation, if a simulated short-circuit test signal is received, control the fast bypass switch and the fast switch to close, control the controllable voltage source to lock out, and when the short-circuit current amplitude detected by the current sensor reaches a preset current amplitude, control the bidirectional bypass thyristor valve and the bypass switch to close, causing the compensator under test to exit, control the fast switch to open after a first delay to disconnect the short-circuit circuit, control the fast bypass switch to open after a second delay to unlock the controllable voltage source, and control the bypass switch to open after a third delay to unlock the compensator under test after the DC side voltage of all voltage source converters is established, thus restoring the compensator under test to its operating state.

[0052] For example, 1) each test sample module (SM1~SMn) is in the input state, the bypass switch (K1~Kn) is opened, the start-up is completed, and the voltage can be output according to the preset command.

[0053] 2) According to the steady-state operation test method, each module is in a steady-state operation state.

[0054] 3) Close the fast bypass switch Kc to lock the controllable voltage source DC / AC (CVS), and close the fast switch Kb to simulate a short-circuit current flowing through the circuit. At this time, after each test module SM detects the short-circuit current through the current sensor CT, when the amplitude of the short-circuit current reaches the preset amplitude, it will activate the bidirectional bypass thyristor valve SCR according to the preset procedure, lock the output of the voltage source converter AC / DC (VSC), close the parallel bypass switch K at the AC port of the module, and complete the exit of the test module SM.

[0055] 4) After a delay of t1, the fast switch Kb is disconnected, simulating the line protection action to disconnect the faulty line. t1 is the line protection action time.

[0056] 5) After a delay of t2, the fast bypass switch Kc is disconnected, the controllable voltage source DC / AC (CVS) is unlocked, and the line is simulated to be re-energized. t2 is the line reclosing time (consistent with the reclosing time of the AC transmission system). At this time, each test module (SM1~SMn) restarts according to the preset procedure after a delay of t3. That is, the current sensors (CT1~CTn) extract power from the line current, the bypass switches (K1~Kn) are opened, the DC side voltage of the voltage source converter AC / DC (VSC1~VSCn) of each module is gradually established and then unlocked, and each test module (SM1~SMn) returns to its operating state before being deactivated, completing the module restart. Each test module (SM1~SMn) is now in the activated state.

[0057] Optionally, the test controller is further configured to, when the compensator under test is running in a steady state, determine the internal fault type of the compensator under test based on the received fault simulation signal, and control the circuit breaker, the fast switch, the fast bypass switch, the controllable voltage source and the compensator under test based on the internal fault type of the compensator under test, so as to realize the internal fault test of the compensator under test.

[0058] For example, 1) each test sample module (SM1~SMn) is in the input state, the bypass switch (K1~Kn) is opened, the start-up is completed, and the voltage can be output according to the preset command.

[0059] 2) According to the steady-state operation test method, each module is in a steady-state operation state.

[0060] 3) Simulate fiber optic communication disconnection faults by disconnecting the fiber optic cable, simulate AC / DC faults of the voltage source converter of the test module SM by setting the software, such as IGBT faults, drive faults, cooling fan faults, etc., simulate bidirectional bypass thyristor valve SCR triggering faults by disconnecting the trigger power supply or setting the software, and simulate AC port parallel bypass switch K failure to operate by disconnecting the bypass switch output node, etc., to verify whether each test module SM can complete the corresponding protection according to the preset logic.

[0061] Optionally, the test controller is specifically used to control the drive pulse lockout of the faulty submodule in the compensator under test when the internal fault type is a submodule communication fault or a voltage source converter fault, control the closing of the bidirectional bypass thyristor valve and the bypass switch, and enable the faulty submodule to bypass and run, thereby realizing the internal fault test of the compensator under test.

[0062] For example, a fiber optic communication failure is simulated by disconnecting the fiber optic cable between the controller and the submodule. At this time, the test submodule SM detects the communication abnormality, blocks the submodule's own drive pulse, and triggers the bidirectional bypass thyristor SCR to close the bypass switch K, thereby realizing the bypass operation of the submodule. Optionally, the test controller is specifically used to monitor the temperature of the compensator under test when the internal fault type is a cooling fan fault, and to derating the output voltage of the compensator under test when the temperature of the compensator under test is greater than or equal to a preset temperature threshold.

[0063] For example, a cooling fan failure is simulated by setting a setting in software. At this time, the test sample submodule SM detects the failure state and monitors its own temperature. Once the temperature exceeds the limit, the output voltage is drated and an SOE event is reported.

[0064] Optionally, the test controller is specifically used to control the drive pulse lockout of the faulty submodule in the compensator under test, control the bypass switch to close, and allow the faulty submodule to operate in bypass mode when the internal fault type is the bidirectional bypass thyristor valve; and to control the drive pulse lockout of the faulty submodule in the compensator under test, control the bidirectional bypass thyristor valve to close, and allow the faulty submodule to operate in bypass mode when the internal fault type is the bypass switch.

[0065] For example, a voltage source converter AC / DC (VSC) fault, such as IGBT fault or drive fault, is simulated in the test module SM by setting a software position. At this time, the test submodule SM detects the fault state, blocks the submodule's own drive pulse, triggers the bidirectional bypass thyristor SCR, closes the bypass switch K, and realizes the bypass operation of the submodule.

[0066] By simulating the triggering fault of the bidirectional bypass thyristor valve SCR by disconnecting the trigger power supply or setting the software, the test submodule SM detects the fault in the bidirectional bypass thyristor valve SCR triggering circuit, blocks the submodule's own drive pulse, and closes the bypass switch K to realize the bypass operation of the submodule. By disconnecting the bypass switch output node and operating the parallel bypass switch K to close, a fault of the parallel bypass switch K failing to operate is simulated at the AC port. At this time, the test sample submodule SM detects that the parallel bypass switch K fails to operate, and then the test sample submodule SM sends a command to the controller to close the large bypass.

[0067] The present invention proposes a laboratory simulation test circuit and method for a distributed static synchronous compensator module, which realizes the functional verification of module startup, shutdown, steady-state operation test, transient system short-circuit test, and module internal fault test under laboratory conditions, and the verification test items are more complete and comprehensive.

[0068] The test circuit has the ability to simulate the steady-state current of the circuit continuously and precisely, and can construct test conditions for module start-up and shutdown according to different set value requirements.

[0069] The test circuit has the capability to test multiple modules simultaneously in batches, resulting in high testing efficiency.

[0070] During the test, the capacitive and inductive reactive power outputs of each module were basically canceled out internally, resulting in a small requirement for the test power supply capacity.

[0071] Example 2: Based on the same inventive concept, the present invention also proposes an experimental method, the method comprising: Based on the received test signal, the circuit breaker, fast switch, fast bypass switch, controllable voltage source and compensator under test are controlled to obtain the output voltage of the compensator under test. Based on the output voltage of the compensator under test, the operating state of the compensator under test is determined, and the test of the compensator under test is realized.

[0072] It should be noted that, in some scenarios, the test method can also be called the laboratory simulation test method for distributed static synchronous compensator modules.

[0073] Optionally, the test signal to be tested is a test start signal; The process of controlling the circuit breaker, fast switch, fast bypass switch, controllable voltage source, and compensator under test based on the received test signal to obtain the output voltage of the compensator under test includes: Based on the start-up test signal, the bypass switch is closed, the current-limiting reactor and the bypass switch form a start-up circuit, the rectifier circuit and the controllable voltage source are unlocked, so that the controllable voltage source outputs an AC voltage of a preset amplitude; When the current in the starting circuit reaches the starting current, all bypass switches are opened and the voltage source converter is unlocked to obtain the output voltage of the compensator under test.

[0074] Optionally, determining the operating state of the compensator under test based on its output voltage includes: When the output voltage of the test compensator reaches the first preset voltage threshold, each sub-module in the test compensator is determined to be in the activated state, thereby enabling the start-up test of the compensator to be tested.

[0075] Optionally, after determining that each submodule in the test compensator is in an engaged state, the method further includes: Upon receiving a steady-state operation test signal, based on the AC current phase detected by the current sensor, the output voltage modulation ratio of the compensator under test is adjusted to the maximum according to a preset steady-state operation strategy to obtain the voltage output capability of the compensator under test. According to the preset adjustment method, the amplitude of the AC voltage output by the controllable voltage source is adjusted to determine the current of each sub-module; When the current of each submodule is greater than or equal to the rated current of the submodule, determine the electrical parameters of each submodule; When the current of each submodule is greater than or equal to the overload current of the submodule, determine the overload parameters of each submodule within a preset time. Based on the voltage output capability of the compensator under test, the electrical parameters of each submodule, and the overload parameters of each submodule within a preset time, a steady-state operation test is conducted on the compensator under test.

[0076] Optionally, after determining that each submodule in the test compensator is in an engaged state, the method further includes: Upon receiving a simulated short-circuit test signal, the system controls the fast bypass switch and the fast switch to close, and controls the controllable voltage source to lock out. When the short-circuit current amplitude detected by the current sensor reaches the preset current amplitude, the system controls the bidirectional bypass thyristor valve and the bypass switch to close, causing the compensator under test to exit. After a first delay, the system controls the fast switch to open, disconnecting the short-circuit circuit. After a second delay, the system controls the fast bypass switch to open, and controls the controllable voltage source to unlock. After a third delay, the system controls the bypass switch to open, and controls all voltage source converters to unlock after the DC side voltage is established, allowing the compensator under test to resume operation.

[0077] This invention proposes a laboratory simulation test circuit and method for a distributed static synchronous compensator module, realizing functional verification of module startup, shutdown, steady-state operation tests, transient system short-circuit tests, and internal fault tests. The test circuit has advantages such as continuous and precisely adjustable simulated steady-state current, low power supply capacity, ability to test both steady-state and transient conditions, and simultaneous batch testing of modules. It boasts high testing efficiency and outstanding technical and economic benefits.

[0078] 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 test circuit for a distributed static synchronous series compensator, characterized by, The test circuit comprises a test power supply, a rectifier circuit, a controllable voltage source, a transformer, a current-limiting reactor, a circuit breaker, a fast switch, a fast bypass switch and a to-be-tested compensator, and the to-be-tested compensator is a distributed static synchronous series compensator; The test power supply is connected with an alternating current side of the rectifier circuit and three-phase terminals of the transformer, a direct current side of the rectifier circuit is connected with a direct current side of the controllable voltage source, and an alternating current side of the controllable voltage source is connected with an incoming line terminal of the circuit breaker; A first outgoing line terminal of the circuit breaker is connected with a first terminal of the fast bypass switch, a first terminal of the current-limiting reactor and a first outgoing line terminal of the fast switch, and a second outgoing line terminal of the circuit breaker is connected with a second terminal of the fast bypass switch and a first terminal of the to-be-tested compensator; Two-phase terminals of the transformer are connected with an incoming line terminal of the fast switch, and a second outgoing line terminal of the fast switch is connected with a second terminal of the current-limiting reactor and a second terminal of the to-be-tested compensator.

2. The circuit of claim 1, wherein, The test circuit further comprises a test controller; The test controller is connected with the circuit breaker, the fast switch, the fast bypass switch, the controllable voltage source and the to-be-tested compensator respectively; The test controller is configured to control the circuit breaker, the fast switch, the fast bypass switch, the controllable voltage source and the to-be-tested compensator based on a received to-be-tested test signal, obtain an output voltage of the to-be-tested compensator, determine an operation state of the to-be-tested compensator based on the output voltage of the to-be-tested compensator, and realize a test of the to-be-tested compensator.

3. The circuit of claim 2, wherein, The to-be-tested compensator comprises a plurality of sub-modules connected in series, and each sub-module comprises a current sensor, a voltage source converter, a direct current side capacitor and a bypass switch; A direct current side of the voltage source converter is connected with the direct current side capacitor in parallel, an alternating current side of the voltage source converter is connected with the bypass switch in parallel, and the alternating current side of the voltage source converter is provided with the current sensor; The test controller is connected with the bypass switch, the current sensor and the voltage source converter in each sub-module respectively; The test controller is specifically configured to control the bypass switch to be closed based on a received start test test signal, control the current-limiting reactor and the bypass switch to form a start loop, control the rectifier circuit and the controllable voltage source to be unlocked, so that the controllable voltage source outputs an alternating current voltage with a preset amplitude, control all bypass switches to be turned off when a current in the start loop collected by the current sensor reaches a start current, control all voltage source converters to be unlocked, and determine that each sub-module in the test compensator is in a put-in state when an output voltage of the test compensator reaches a first preset voltage threshold, so as to realize a start test of the to-be-tested compensator.

4. The circuit of claim 3, wherein, The test controller is specifically configured to, when the to-be-tested compensator is in the put-into state, if a steady-state operation test test signal is received, based on the AC current phase detected by the current sensor, according to a preset steady-state operation strategy, modulate the output voltage modulation ratio of the to-be-tested compensator to the maximum to obtain the voltage output capability of the to-be-tested compensator, and according to a preset adjustment mode, adjust the AC voltage amplitude output by the controllable voltage source to determine the current of each sub-module, when the current of each sub-module is greater than or equal to the rated current of the sub-module, determine the electrical parameter of each sub-module, when the current of each sub-module is greater than or equal to the overload current of the sub-module, determine the overload parameter of each sub-module within a preset time, and based on the voltage output capability of the to-be-tested compensator, the electrical parameter of each sub-module and the overload parameter of each sub-module within the preset time, perform the steady-state operation test test on the to-be-tested compensator.

5. The circuit of claim 4, wherein, The test controller is specifically configured to: Based on the AC current phase detected by the current sensor, control the output voltage modulation ratio of the to-be-tested compensator, so that the output voltage amplitude of each sub-module in the to-be-tested compensator is the same, the output voltage of each sub-module is 90° with the AC current, and the output voltage phase of part of the sub-modules leads the AC current, and the output voltage phase of another part of the sub-modules lags the AC current.

6. The circuit of claim 5, wherein, The number n of sub-modules in the to-be-tested compensator is even, and all the sub-modules are divided into two parts, the sub-modules whose output voltage phase leads the AC current and the sub-modules whose output voltage phase lags the AC current; The number n of sub-modules in the to-be-tested compensator is odd, (n+1) / 2 sub-modules are used as the sub-modules whose output voltage phase leads the AC current, and (n-1) / 2 sub-modules are used as the sub-modules whose output voltage phase lags the AC current.

7. The circuit of claim 3, wherein, Each sub-module further comprises a bidirectional bypass thyristor valve connected in parallel with the AC side of the voltage source converter; The test controller is further connected with the bidirectional bypass thyristor valve in each sub-module; The test controller is specifically configured to, when the to-be-tested compensator is in the put-into state, based on the received test exit test signal, according to a preset exit strategy, control the AC voltage amplitude output by the controllable voltage source, when the current in each sub-module is less than the exit current, control all the bidirectional bypass thyristor valves to be turned on, control all the voltage source converters to be blocked, after all the voltage source converters are blocked, control all the bidirectional bypass thyristor valves to be turned off, control all the bypass switches to be turned on, so that each sub-module in the test compensator is in the exit state, and the to-be-tested compensator is subjected to the exit test test.

8. The circuit of claim 6, wherein, The test controller is specifically configured to, when the to-be-tested compensator is in steady-state operation, if an analog short-circuit test signal is received, control the fast bypass switch and the fast switch to be closed, control the controllable voltage source to be locked, when a short-circuit current amplitude detected by the current sensor reaches a preset current amplitude, control the bidirectional bypass thyristor valve and the bypass switch to be closed, so that the to-be-tested compensator exits, after a first delay, control the fast switch to be opened, and the short-circuit line is cut off, after a second delay, control the fast bypass switch to be opened, control the controllable voltage source to be unlocked, after a third delay, control the bypass switch to be opened, and after a voltage on a direct-current side of all voltage source converters is established, the to-be-tested compensator is unlocked, and the to-be-tested compensator returns to a running state.

9. The circuit of claim 6, wherein, The test controller is further configured to, when the to-be-tested compensator is in steady-state operation, based on a received fault simulation signal, determine an internal fault type of the to-be-tested compensator, based on the internal fault type of the to-be-tested compensator, control the circuit breaker, the fast switch, the fast bypass switch, the controllable voltage source and the to-be-tested compensator, and implement internal fault test testing of the to-be-tested compensator.

10. The circuit of claim 9, wherein, The test controller is specifically configured to, when the internal fault type is a sub-module communication fault or a voltage source converter fault, control a drive pulse of a faulty sub-module in the to-be-tested compensator to be locked, and control the bidirectional bypass thyristor valve and the bypass switch to be closed, so that the faulty sub-module is bypassed to run, and internal fault test testing of the to-be-tested compensator is implemented.

11. The circuit of claim 9, wherein, The test controller is specifically configured to, when the internal fault type is a cooling fan fault, monitor a temperature of the to-be-tested compensator, and when the temperature of the to-be-tested compensator is greater than or equal to a preset temperature threshold, perform de-rating control on an output voltage of the to-be-tested compensator.

12. The circuit of claim 9, wherein, The test controller is specifically configured to, when the internal fault type is the bidirectional bypass thyristor valve, control a drive pulse of a faulty sub-module in the to-be-tested compensator to be locked, and control the bypass switch to be closed, so that the faulty sub-module is bypassed to run, and when the internal fault type is the bypass switch, control a drive pulse of a faulty sub-module in the to-be-tested compensator to be locked, and control the bidirectional bypass thyristor valve to be closed, so that the faulty sub-module is bypassed to run.

13. A test method characterized by, The method comprises: based on the received to-be-tested test signal, controlling the circuit breaker, the fast switch, the fast bypass switch, the controllable voltage source and the to-be-tested compensator to obtain an output voltage of the to-be-tested compensator; based on the output voltage of the to-be-tested compensator, determining a running state of the to-be-tested compensator, and implementing test of the to-be-tested compensator.

14. The method of claim 13, wherein, The to-be-tested test signal is a start test signal. The method comprises: based on the received to-be-tested test signal, controlling the circuit breaker, the fast switch, the fast bypass switch, the controllable voltage source and the to-be-tested compensator to obtain an output voltage of the to-be-tested compensator, Based on the starting test signal, the bypass switches are controlled to be closed, the current limiting reactor and the bypass switches form a starting circuit, the rectifier circuit and the controllable voltage source are unlocked, so that the controllable voltage source outputs an alternating voltage with a preset amplitude; When the current in the starting circuit reaches a starting current, all the bypass switches are controlled to be opened, the controllable voltage source converter is unlocked, and the output voltage of the to-be-tested compensator is obtained.

15. The method of claim 14, wherein, The running state of the to-be-tested compensator is determined based on the output voltage of the to-be-tested compensator, and the method comprises the following steps: When the output voltage of the test compensator reaches a first preset voltage threshold, it is determined that each sub-module in the test compensator is in an on-state, and the starting test of the to-be-tested compensator is implemented.

16. The method of claim 15, wherein, After determining that each sub-module in the test compensator is in the on-state, the method further comprises the following steps: When a steady-state running test signal is received, based on the phase of the alternating current detected by the current sensor, the output voltage modulation ratio of the to-be-tested compensator is adjusted to the maximum according to a preset steady-state running strategy, and the voltage output capability of the to-be-tested compensator is obtained. The amplitude of the alternating voltage output by the controllable voltage source is adjusted according to a preset adjustment mode, and the current of each sub-module is determined. When the current of each sub-module is greater than or equal to the rated current of the sub-module, the electrical parameters of each sub-module are determined. When the current of each sub-module is greater than or equal to the overload current of the sub-module, the overload parameters of each sub-module within a preset time are determined. Based on the voltage output capability of the to-be-tested compensator, the electrical parameters of each sub-module, and the overload parameters of each sub-module within a preset time, the steady-state running test of the to-be-tested compensator is implemented.

17. The method of claim 15, wherein, After determining that each sub-module in the test compensator is in the on-state, the method further comprises the following steps: When an analog short-circuit test signal is received, the fast bypass switch and the fast switch are controlled to be closed, the controllable voltage source is controlled to be locked, when the amplitude of the short-circuit current detected by the current sensor reaches a preset current amplitude, the bidirectional bypass thyristor valve and the bypass switch are controlled to be closed, so that the to-be-tested compensator is exited, after a first delay, the fast switch is controlled to be opened, the short-circuit line is cut off, after a second delay, the fast bypass switch is controlled to be opened, the controllable voltage source is controlled to be unlocked, after a third delay, the bypass switch is controlled to be opened, and after the DC side voltage of all the voltage source converters is established, the to-be-tested compensator is restored to the running state.

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