Static synchronous phase modifier system for power grid side and starting method and device thereof

Abstract

The invention provides a static synchronous phase modifier system for a power grid side, an alternating current side of the static synchronous phase modifier system comprises an alternating current switch, alternating current side switch disconnecting link equipment and a starting loop which are sequentially connected in series, and the starting loop comprises a starting resistor and a bypass switch which are connected in parallel. The direct current side for the static synchronous phase modifier system at the power grid side further comprises a converter valve for providing reactive power support; and the super-capacity valve provides inertia support and is arranged in parallel with the converter valve through a direct current side switch knife switch device. The invention further provides a starting method and device for the power grid side static synchronous phase modifier system. The system is used for a power grid side static synchronous phase modifier system, a converter valve and a super-capacitance valve are independently arranged in different halls through direct current side switch disconnecting link equipment, the problem of tight coupling of the converter valve and the super-capacitance valve is solved, the converter valve can operate independently of the super-capacitance valve, and the converter valve can continuously provide reactive power support for an alternating current system when the super-capacitance valve exits from operation. The system operation flexibility is improved, and the system availability is improved.

Description

Technical Field

[0001] The present application relates to the technical field of static var compensation, and particularly relates to a grid-side static synchronous compensator system, a starting method and a device thereof. Background Art

[0002] With the accelerated promotion of the construction of the national new energy system, the large-scale development and centralized transmission of new energy in China will enter a period of rapid development, and the "dual high" characteristics of a high proportion of new energy and a high proportion of power electronic equipment in the power system are becoming increasingly prominent. Weak power grids dominated by new energy generally have a relatively weak grid framework and a lag in the construction of conventional power sources. The externally controlled characteristics of power electronic devices such as new energy have a great impact on the stability of the power grid under a weak grid framework. The voltage stability problem, the power angle stability problem, and the dynamic frequency stability problem caused by the lack of inertia are intertwined. Conventional static var compensators can only provide voltage and reactive power support for the AC system and cannot solve the transient frequency stability problem caused by the lack of inertia.

[0003] A static synchronous compensator is a static var compensation device based on power electronic technology. A static synchronous compensator is similar to a conventional synchronous machine. By simulating the excitation control link of the synchronous machine, it controls the amplitude of the internal electromotive force output by the converter. During an AC system fault, it naturally responds to the AC system fault and outputs reactive current to support the recovery of the AC system fault. On the other hand, based on virtual synchronous control technology, it controls the phase angle output by the converter, naturally responds to the AC system fault, releases the energy stored in the supercapacitor, provides inertia support for the AC system, and enhances the transient stability of the AC system.

[0004] At present, the energy storage unit and the converter unit of the static synchronous compensator system are integrally designed. In the integrated design mode, there are problems of strong coupling between the energy storage unit and the converter. On the one hand, when the energy storage unit fails, the converter unit needs to be synchronously withdrawn from operation, and the converter cannot provide reactive power support for the AC system alone. On the other hand, there is a risk of battery fire in the energy storage unit, which poses a safety hazard to the operation of the converter. Summary of the Invention

[0005] The present application provides a grid-side static synchronous compensator system, a starting method and a device thereof to solve the problems that the converter needs to be synchronously withdrawn from operation after the failure of the existing energy storage unit and the influence of the energy storage unit catching fire on the converter.

[0006] To solve the above technical problems, the present application provides a grid-side static synchronous compensator system. The AC side thereof includes an AC switch, an AC side switch disconnector device, and a starting circuit connected in series in sequence. The starting circuit includes a starting resistor and a bypass switch connected in parallel, and the DC side for the grid-side static synchronous compensator system further includes: a converter valve for providing reactive power support; a supercapacitor valve for providing inertia support, which is connected in parallel with the converter valve through a DC side switch disconnector device.

[0007] Further, the commutation valve is of a double-star parallel structure, and each phase is composed of upper and lower bridge arms, and each bridge arm adopts a full-bridge sub-module series structure or a full-half-bridge sub-module hybrid series structure.

[0008] Further, the grid-side static synchronous compensator system further includes a smoothing reactor, and the smoothing reactor is connected between each phase bridge arm of the commutation valve and the starting circuit.

[0009] Further, the super-capacitor valve adopts a single-branch structure or a multi-branch parallel structure.

[0010] Further, each sub-module in the super-capacitor valve includes an energy storage unit, and the energy storage unit is connected in parallel with a support capacitor through a fuse and a circuit breaker. When a fault occurs in the AC system, the energy in the energy storage unit is released to provide inertia support for the AC system.

[0011] The present invention also provides a starting method for a grid-side static synchronous compensator system, including: closing the AC switch, closing the bypass switch after detecting that the valve-side current is less than a first preset value; increasing the DC-side voltage, performing unlocking of the commutation valve after detecting that the DC-side voltage reaches a second preset value; making the DC-side differential-mode voltage zero by controlling the commutation valve, closing the DC-side switch disconnector device to put the super-capacitor valve into operation; charging the super-capacitor valve by increasing the DC-side voltage at a preset rate. When the DC-side voltage reaches a third preset value and the super-capacitor valve operates normally, unlocking the super-capacitor valve; the super-capacitor valve enters a constant DC voltage control mode, and the DC-side voltage is controlled at a fourth preset value by controlling the charging and discharging of the sub-modules of the super-capacitor valve, and the unlocking of the static synchronous compensator is completed.

[0012] Further, before the commutation valve is charged, the starting resistor is connected in series in the main circuit, and the DC-side switch disconnector device is in an off state.

[0013] Further, the commutation valve is of a double-star parallel structure, and each phase is composed of upper and lower bridge arms, and each bridge arm adopts a full-bridge sub-module series structure or a full-half-bridge sub-module hybrid series structure. The DC-side differential-mode voltage is made zero by controlling the number of sub-modules in the commutation valve bridge arm.

[0014] The present invention also provides a starting device for a grid-side static synchronous compensator system, including:

[0015] A first detection module, which closes the AC switch and closes the bypass switch after detecting that the valve-side current is less than a first preset value;

[0016] A second detection module, which increases the DC-side voltage and performs unlocking of the commutation valve after detecting that the DC-side voltage reaches a second preset value;

[0017] The first control module makes the DC side differential mode voltage zero by controlling the converter valve, and closes the DC side switch disconnector device to put the supercapacitor valve into operation.

[0018] The second control module charges the supercapacitor valve by increasing the DC side voltage at a preset rate. When the DC side voltage reaches the third preset value and the supercapacitor valve operates normally, the supercapacitor valve is unlocked.

[0019] The third control module: when the supercapacitor valve enters the constant DC voltage control mode, the DC side voltage is controlled at the fourth preset value by controlling the charge and discharge of the sub-modules of the supercapacitor valve, and the static synchronous compensator is unlocked.

[0020] For the static synchronous compensator system on the grid side provided by the present invention, the converter valve and the supercapacitor valve are separately arranged in different halls through the DC side switch disconnector device, which solves the problem of strong coupling between the converter valve and the supercapacitor valve. The converter valve can operate independently of the supercapacitor valve. During the period when the supercapacitor valve is out of operation, the converter valve can continue to provide reactive power support for the AC system, improving the flexibility of system operation and the system availability; the physical isolation of the operating environments of the converter valve and the supercapacitor valve reduces the impact of the battery fire of the supercapacitor valve on the converter valve.

[0021] The starting method and device for the static synchronous compensator system on the grid side provided by the present invention improve the flexibility of the operation mode of the static synchronous compensator system, enabling both independent operation of the converter valve and combined operation of the converter valve and the supercapacitor valve; facilitating maintenance when the supercapacitor valve is separately taken out of operation, and improving the equipment availability; zero-voltage starting and charging of the supercapacitor valve reduce the impact on the power grid during the start-up of the whole system, reduce the impact energy tolerance requirements for primary equipment such as starting resistors, and increase the equipment safety factor; the starting device for the static synchronous compensator system on the grid side can realize frequent starting operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 It is a schematic structural diagram of the static synchronous compensator system on the grid side provided by the embodiment of the present invention;

[0024] Figure 2a It is a schematic diagram of the full-bridge electrical main circuit structure of the sub-module in the converter valve provided by the embodiment of the present invention;

[0025] Figure 2b Schematic diagram of the half-bridge electrical main circuit structure of the sub-module in the converter valve provided by the embodiment of the present invention;

[0026] Figure 3 Schematic diagram of the electrical main circuit structure of the sub-module in the supercapacitor valve provided by the embodiment of the present invention. Specific embodiments

[0027] Next, the technical solutions in the present application will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0028] In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present application.

[0029] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and can also be the communication inside two elements. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0030] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0031] Figure 1 Schematic diagram of the structure of the grid-side static synchronous compensator system provided by the embodiment of the present invention. Refer to Figure 1 , for the grid-side static synchronous compensator system, its AC side includes an AC switch 101, an AC side switch disconnector device 102, and a starting circuit 103 connected in series in sequence, wherein the starting circuit 103 includes a starting resistor 103a and a bypass switch 103b connected in parallel. The DC side of the grid-side static synchronous compensator system further includes: a converter valve 104 for providing reactive power support; a supercapacitor valve 105 for providing inertia support, which is connected in parallel with the converter valve 104 through a DC side switch disconnector device 106.

[0032] In an embodiment of the present invention, the converter valve is of a double-star parallel structure. Each phase is composed of two upper and lower bridge arms, and each bridge arm adopts a series structure of full-bridge sub-modules or a hybrid series structure of full-half-bridge sub-modules. By controlling the triggering of each bridge arm sub-module in the converter valve, the output voltage on the converter valve side is controlled, and further the power injected into the AC system is controlled. Figure 2a It is a schematic diagram of the full-bridge electrical main circuit structure of the sub-module in the converter valve provided by the embodiment of the present invention;

[0033] Figure 2b It is a schematic diagram of the half-bridge electrical main circuit structure of the sub-module in the converter valve provided by the embodiment of the present invention. Refer to Figure 2a , the full-bridge electrical main circuit of the sub-module in the converter valve includes the bridge arm composed of T1 and T2 and the bridge arm composed of T3 and T4, the energy-consuming resistors and support capacitors connected in parallel with the bridge arms respectively, a turning thyristor is connected between the two bridge arms, and the turning thyristor is connected in parallel with the bypass switch. Refer to Figure 2b , the half-bridge electrical main circuit of the sub-module in the converter valve includes the bridge arm composed of T1 and T2, the energy-consuming resistor and support capacitor connected in parallel with the bridge arm respectively, the turning thyristor connected in parallel with the semiconductor device T2, and the turning thyristor is connected in parallel with the bypass switch.

[0034] In an embodiment of the present invention, the grid-side static synchronous compensator system further includes a smoothing reactor 107. The smoothing reactor 107 is connected between each phase bridge arm of the converter valve and the starting circuit, and in each branch of the super-capacitor valve, to achieve the suppression of harmonic circuits and fault currents.

[0035] Figure 3 It is a schematic diagram of the electrical main circuit structure of the sub-module in the super-capacitor valve provided by the embodiment of the present invention. Refer to Figure 3 , the electrical main circuit of the sub-module in the super-capacitor valve includes semiconductor devices T1 and T2 connected in series, the support capacitor, super-capacitor module, and energy-consuming resistor connected in parallel with T1 and T2. A circuit breaker and a fuse FU are connected in series between the energy-consuming resistor and the support capacitor, and T2 is connected in parallel with the bypass switch K1. By controlling the switching or charging and discharging of the sub-module of the super-capacitor valve, the control of the DC-side voltage is achieved. Further, the super-capacitor valve adopts a single-branch structure or a multi-branch parallel structure, and the on-line switching-in / switching-out function of the super-capacitor valve is realized by controlling the DC-side switch-disconnector equipment.

[0036] Each sub-module in the super-capacitor valve includes an energy storage unit. The energy storage unit is connected in parallel with the support capacitor through a fuse and a circuit breaker. When a fault occurs in the AC system, the energy in the energy storage unit is released to provide inertia support for the AC system.

[0037] For the grid-side static synchronous compensator system provided by the present invention, the converter valve and the super-capacitor valve are separately arranged in different halls through the DC-side switch disconnector device, solving the problem of tight coupling between the converter valve and the super-capacitor valve. The converter valve can operate independently of the super-capacitor valve. During the period when the super-capacitor valve is out of operation, the converter valve can continue to provide reactive power support for the AC system, improving the flexibility of system operation and the system availability; the physical isolation of the operating environments of the converter valve and the super-capacitor valve reduces the impact of the super-capacitor battery fire on the converter valve.

[0038] The present invention also provides a starting method for a grid-side static synchronous compensator system, including: closing the AC switch, and after detecting that the valve-side current is less than a first preset value, closing the bypass switch; increasing the DC-side voltage, and after detecting that the DC-side voltage reaches a second preset value, performing unlocking of the converter valve; making the DC-side differential mode voltage zero by controlling the converter valve, and closing the DC-side switch disconnector device to put the super-capacitor valve into operation; charging the super-capacitor valve by increasing the DC-side voltage at a preset rate, and when the DC-side voltage reaches a third preset value and the super-capacitor valve operates normally, unlocking the super-capacitor valve; the super-capacitor valve enters the constant DC voltage control mode, and by controlling the charging and discharging of the sub-modules of the super-capacitor valve, controlling the DC-side voltage at a fourth preset value to complete the unlocking of the static synchronous compensator.

[0039] In the embodiment of the present invention, before the converter valve is charged, the starting resistor is connected in series in the main circuit, and the DC-side switch disconnector device is in the off state. The converter valve is of a double-star parallel structure, each phase is composed of upper and lower two bridge arms, and each bridge arm adopts a full-bridge sub-module series structure or a full-half-bridge sub-module hybrid series structure, and the DC-side differential mode voltage is made zero by controlling the number of sub-modules in the converter valve bridge arm.

[0040] Closing the AC switch, the converter valve enters the charging process. The whole charging process is divided into two stages. The first stage is the uncontrolled charging stage. After detecting that the valve-side current is less than the first preset value, closing the bypass switch to reduce the impact on the AC system at the moment of unlocking. In the embodiment of the present invention, the first preset value is 2 A. At this time, the uncontrolled rectification stage charging is close to the completion state, and the converter valve sub-module voltage is about 1000 V.

[0041] Entering the second stage (controlled charging stage) of the charging process, increasing the DC-side voltage, and after detecting that the DC-side voltage reaches the second preset value. In the embodiment of the present invention, the second preset value is the rated operating voltage of the power unit, which is 2100 V. The unlocking state signal is valid, and the unlocking instruction is executed to achieve the unlocking of the converter valve.

[0042] After the converter valve is unlocked, the DC side differential mode voltage is controlled to be zero by controlling the converter valve, and the DC side switch disconnector is closed to put the supercapacitor valve into operation. By adjusting the upper and lower arm port voltages to be in the same phase as the AC system voltage and opposite in amplitude, the DC side differential mode voltage can be controlled to be zero.

[0043] When it is detected that the supercapacitor valve is put into operation, the DC side voltage is increased at a preset rate to charge the supercapacitor valve. In the embodiment of the present invention, the supercapacitor valve is charged at 100V / S. When the DC side voltage reaches the third preset value and the supercapacitor valve operates normally, the supercapacitor valve is unlocked. In the embodiment of the present invention, the third preset value is 13KV.

[0044] After the supercapacitor valve is unlocked, the supercapacitor valve enters the constant DC voltage control mode, and the DC differential mode voltage continues to increase at a preset rate. The fixed number of supercapacitor valve sub-modules are rotated and switched to charge the supercapacitor valve sub-modules. By controlling the charge and discharge of the sub-modules of the supercapacitor valve, the DC side voltage is controlled at the fourth preset value. In the embodiment of the present invention, the fourth preset value is 30KV, 30 supercapacitor valve sub-modules are fixed and put into operation, and the rest of the modules are in the cut-off state. The voltage of each supercapacitor valve sub-module reaches 1000V, and thus the static synchronous compensator is unlocked.

[0045] The present invention also provides a starting device for a grid-side static synchronous compensator system, including:

[0046] A first detection module, after closing the AC switch and detecting that the valve-side current is less than the first preset value, closes the bypass switch;

[0047] A second detection module, increases the DC side voltage, and after detecting that the DC side voltage reaches the second preset value, performs the unlocking of the converter valve;

[0048] A first control module, controls the converter valve to make the DC side differential mode voltage zero, and closes the DC side switch disconnector to put the supercapacitor valve into operation;

[0049] A second control module, increases the DC side voltage at a preset rate to charge the supercapacitor valve, and unlocks the supercapacitor valve when the DC side voltage reaches the third preset value and the supercapacitor valve operates normally;

[0050] A third control module, the supercapacitor valve enters the constant DC voltage control mode, and by controlling the charge and discharge of the sub-modules of the supercapacitor valve, controls the DC side voltage at the fourth preset value to complete the unlocking of the static synchronous compensator.

[0051] The starting method and device for the grid-side static synchronous compensator system provided by the present invention improve the flexibility of the operation mode of the static synchronous compensator system, enabling both the converter valve to operate independently and the converter valve to operate in combination with the over-capacity valve; facilitating the maintenance when the over-capacity valve is withdrawn from operation alone, and improving the equipment availability; the over-capacity valve is charged with zero voltage starting, reducing the impact on the power grid during the starting of the whole system, reducing the impact energy tolerance requirements for primary equipment such as starting resistors, and increasing the equipment safety factor; the starting device for the grid-side static synchronous compensator system can realize frequent starting operations.

[0052] Obviously, the above embodiments are merely examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A grid-side static synchronous compensator system, the AC side of which includes an AC switch, an AC side switch-disconnector device, and a starting circuit connected in series in sequence, wherein the starting circuit includes a starting resistor and a bypass switch connected in parallel, and is characterized in that, The DC side of the grid-side static synchronous compensator system further includes: A converter valve for providing reactive power support; A supercapacitor valve for providing inertia support, which is arranged in parallel with the converter valve through a DC-side switch disconnector device.

2. The supercapacitor module charge and discharge test system according to claim 1, wherein The converter valve is of a double-star parallel structure, each phase consists of upper and lower two bridge arms, and each bridge arm adopts a full-bridge sub-module series structure or a full-half-bridge sub-module hybrid series structure.

3. The supercapacitor module charge and discharge test system according to claim 2, wherein, It also includes a smoothing reactor, and the smoothing reactor is connected between each phase bridge arm and the starting circuit.

4. The supercapacitor module charge and discharge test system according to claim 1, wherein, The supercapacitor valve adopts a single-branch structure or a multi-branch parallel structure.

5. The supercapacitor module charge and discharge test system according to claim 1, wherein, Each sub-module in the supercapacitor valve includes an energy storage unit, and the energy storage unit is connected in parallel with a support capacitor through a fuse and a circuit breaker. When a fault occurs in the AC system, inertia support is provided for the AC system by releasing the energy in the energy storage unit.

6. A starting method for a grid-side static synchronous compensator system as described in claim 1, characterized in that, Includes: Close the AC switch. After detecting that the valve-side current is less than the first preset value, close the bypass switch; Increase the DC-side voltage. After detecting that the DC-side voltage reaches the second preset value, perform unlocking of the converter valve; Make the DC-side differential-mode voltage zero by controlling the converter valve, and close the DC-side switch disconnector device to put the supercapacitor valve into operation; Charge the supercapacitor valve by increasing the DC-side voltage at a preset rate. When the DC-side voltage reaches the third preset value and the supercapacitor valve operates normally, unlock the supercapacitor valve; The supercapacitor valve enters the constant DC voltage control mode. By controlling the charging and discharging of the sub-modules of the supercapacitor valve, the DC-side voltage is controlled at the fourth preset value to complete the unlocking of the static synchronous compensator.

7. The starting method for a grid-side static synchronous compensator system according to claim 6, characterized in that, Before the converter valve is charged, the starting resistor is connected in series in the main circuit, and the DC-side switch disconnector device is in the off state.

8. The starting method for a grid-side static synchronous compensator system according to claim 6, characterized in that, The converter valve is of a double-star parallel structure, each phase consists of upper and lower two bridge arms, and each bridge arm adopts a full-bridge sub-module series structure or a full-half-bridge sub-module hybrid series structure. The DC-side differential-mode voltage is made zero by controlling the number of sub-modules in the converter valve bridge arm.

9. A starting device for a grid-side static synchronous compensator system as described in claim 1, characterized in that, Includes: A first detection module, which closes the AC switch. After detecting that the valve-side current is less than the first preset value, closes the bypass switch; A second detection module, which increases the DC-side voltage. After detecting that the DC-side voltage reaches the second preset value, performs unlocking of the converter valve; A first control module, which makes the DC-side differential-mode voltage zero by controlling the converter valve, and closes the DC-side switch disconnector device to put the supercapacitor valve into operation; A second control module, which charges the supercapacitor valve by increasing the DC-side voltage at a preset rate. When the DC-side voltage reaches the third preset value and the supercapacitor valve operates normally, unlocks the supercapacitor valve; A third control module, when the supercapacitor valve enters the constant DC voltage control mode, controls the charging and discharging of the sub-modules of the supercapacitor valve to control the DC-side voltage at the fourth preset value to complete the unlocking of the static synchronous compensator.

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