Two-phase starting loop of SVG (Static Var Generator) and control method thereof

Abstract

The invention belongs to the field of power electronics, and discloses a two-phase starting loop of an SVG and a control method thereof, which are characterized in that any two phases in three phases on the valve side of the SVG are connected with starting resistors, the other phase is not connected with the starting resistor, the starting resistors are all located between the corresponding phases on the inlet wire side and the valve side of the SVG, each starting resistor is connected with a bypass switch in parallel, and the bypass switch is connected with the SVG. And the access or short-circuit state of the resistor can be switched through opening and closing operation. When the bypass switch is switched off, the two-phase starting resistor is connected into a loop to form a three-phase asymmetric charging topology, and soft start in an uncontrolled charging stage is realized by using the resistor to limit current; then, when the bypass switch is switched on, the resistor is short-circuited, a loop is switched into a three-phase symmetrical conduction mode, controllable charging and subsequent stable operation are achieved, and a transition mechanism from asymmetry to symmetry is utilized, a three-phase H-bridge structure is adapted, and it is ensured that the charging process is smooth and efficient; according to the loop, the structure is simplified, the number of elements is reduced, and a bypass control function is integrated, so that the system cost and size are remarkably reduced, and the applicability and reliability are improved.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, specifically to the field of grid-type SVG, and particularly relates to a two-phase start-up circuit of SVG and its control method. Background Technology

[0002] In the field of power electronics technology, the starting circuit of a voltage source converter is a crucial component for ensuring the safe and stable startup of devices such as SVG (Static Var Generator). These starting circuits are generally classified into outdoor and indoor types based on their installation method. Outdoor starting circuits are mostly used in 35kV SVG AC side startup scenarios, while indoor starting circuits are commonly used for 10kV SVG AC side startup. Currently, standardized design has become the mainstream direction for the development of power electronics products. SVG equipment itself explicitly requires characteristics such as high power density, small footprint, and ease of maintenance. Therefore, developing a compact, easy-to-maintain AC starting circuit that meets standardized design requirements has become a significant technical challenge that urgently needs to be addressed in the industry.

[0003] In the prior art, those skilled in the art have studied an integrated high-voltage two-phase reactor starter cabinet. This device is mainly used as a switching circuit for two-phase reactor switchgear, but it has obvious limitations in applicability and functional defects: First, its structural design cannot match the usage requirements of a three-phase H-bridge starter circuit, and it lacks the core function of a bypass starter resistor; second, this device adopts an indoor cabinet structure, making it unsuitable for the starter scenarios of outdoor SVG equipment, and thus failing to meet the application requirements of outdoor SVG. Meanwhile, there is currently no ideal solution for outdoor SVG starter circuits, and they generally suffer from problems such as high cost and large size, which contradicts the development requirements of SVG equipment.

[0004] It is evident that the existing start-up circuit is ill-suited to the needs of outdoor SVG devices and suffers from prominent problems such as high cost, large size, and poor applicability. Summary of the Invention

[0005] This invention provides a two-phase starting circuit for SVG and its control method. The use of this two-phase starting circuit can meet the usage requirements of outdoor SVG equipment, which are difficult to adapt to by existing starting circuits, and have problems such as high cost, large size and poor applicability.

[0006] To achieve the above objectives, the present invention employs the following technical content: A two-phase starting circuit for an SVG includes: an SVG input side and an SVG valve side connected together; the SVG input side is connected to the AC side in a corresponding manner. Any two of the three phases on the SVG valve side are connected to a starting resistor, while the other phase is not connected to a starting resistor. The starting resistor is connected between the corresponding phase of the SVG input line side and the SVG valve side; The two starting resistors are respectively connected in parallel to corresponding bypass switches; The bypass switch can switch the starting resistor between connected and short-circuited states through opening and closing operations; When the bypass switch is in the open state, the corresponding starting resistor is connected to the circuit to form a three-phase asymmetrical charging circuit to achieve uncontrolled charging. When the bypass switch is in the closed state, the corresponding starting resistor is short-circuited to form a three-phase symmetrical conduction circuit, thereby achieving controllable charging.

[0007] Furthermore, each of the three-phase SVG input lines is connected to an isolating switch.

[0008] Furthermore, one end of the disconnect switch is connected to the SVG input side, and the other end is connected to the SVG valve side; A grounding wire is also led out from the other end of the disconnecting switch and the SVG valve side, and a grounding switch is installed on the grounding wire.

[0009] Furthermore, a reactor is connected to the input terminal of each phase on the SVG valve side; wherein, on the SVG valve side phase with a starting resistor, the reactor is connected between the starting resistor and the SVG valve side.

[0010] Furthermore, the two-phase start-up circuit adopts a star connection topology or a delta connection topology.

[0011] Furthermore, in the star topology, the outgoing terminals of the three phases on the SVG valve side are all connected to the same star neutral point.

[0012] Furthermore, in the aforementioned corner-connected topology, the outgoing terminal of phase A on the SVG valve side is connected to the incoming terminal of phase B on the SVG valve side, the outgoing terminal of phase B on the SVG valve side is connected to the incoming terminal of phase C on the SVG valve side, and the outgoing terminal of phase C on the SVG valve side is connected to the incoming terminal of phase A on the SVG valve side.

[0013] Furthermore, each phase output terminal of the SVG valve is connected to a Hall sensor.

[0014] Furthermore, the bypass switch is a circuit breaker or contactor used to switch the connection and short-circuit of the starting resistor.

[0015] A control method for a two-phase starting circuit of an SVG, based on the aforementioned two-phase starting circuit of the SVG, includes: After the SVG enters the charging state, the bypass switch is opened to connect the starting resistor, the IGBT on the SVG valve side is locked, and the grid voltage charges the capacitor through the anti-parallel diode of the IGBT, entering the uncontrolled charging process. When the real-time acquired value of DC voltage exceeds the set value of DC voltage, the bypass switch is closed to short-circuit the starting resistor, the IGBT on the SVG valve side is unlocked, and the grid voltage is used to charge the capacitor through the IGBT, thus entering the controllable charging process.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a two-phase starting circuit for an SVG (SVG), comprising connecting starting resistors to any two of the three phases on the valve side of the SVG, while leaving the third phase unconnected. The starting resistors are located between the corresponding phases on the SVG's input side and the valve side, and each starting resistor is connected in parallel with a bypass switch. The connection or short-circuit state of the resistors can be switched by opening and closing the circuit breaker. When both bypass switches are open, two phase starting resistors are connected to the circuit, forming a three-phase asymmetrical charging topology. The resistors limit the current to achieve soft start during the uncontrolled charging phase. Subsequently, when both bypass switches are closed, the resistors are short-circuited, and the circuit switches to a three-phase symmetrical conduction mode, achieving controlled charging and subsequent stable operation. This design cleverly utilizes the transition mechanism from asymmetrical to symmetrical, adapting to a three-phase H-bridge structure to ensure a smooth and efficient charging process. This circuit significantly reduces system cost and size by simplifying the structure, reducing the number of components, and integrating bypass control functions. It also improves applicability and reliability, especially meeting the starting requirements of outdoor SVG equipment. It effectively overcomes the shortcomings of existing technologies, such as incompatibility with three-phase circuits, lack of bypass capability, and limitations in outdoor applications, achieving an economical, compact, flexible, and efficient starting solution.

[0017] Preferably, in this invention, the installation of a disconnecting switch achieves electrical isolation on the incoming line side, improving equipment maintenance safety and operational flexibility, and enhancing adaptability to outdoor environments.

[0018] Preferably, in this invention, the combination of a grounding wire and a grounding switch ensures that residual charge is reliably released after the equipment is powered off, avoiding the risk of electric shock to operators and strengthening the safety protection mechanism. Preferably, in this invention, the optimized layout of the reactor on the valve side effectively suppresses current surges and harmonic interference during startup, thereby improving system stability and device lifespan.

[0019] Preferably, the present invention provides two topology options: star connection and delta connection, which enables the circuit to flexibly adapt to different power grid wiring methods and greatly expands the application scenario coverage.

[0020] Preferably, in this invention, the star-shaped neutral point structure can balance the voltage difference between phases, reduce the influence of zero-sequence components, simplify circuit design, and improve charging voltage equalization performance. Preferably, in this invention, automatic phase-to-phase current balancing is achieved through a corner-connected closed-loop connection, which optimizes power transmission efficiency and reduces the need for additional voltage equalization circuits. Preferably, in this invention, a Hall sensor is used to monitor the phase current status in real time, providing accurate feedback for charging control and improving the system's protection response speed and reliability.

[0021] This invention also provides a control method for a two-phase starting circuit of an SVG. Based on the aforementioned two-phase starting circuit of the SVG, in the initial stage of SVG charging, the bypass switch is opened to connect a resistor, and the valve-side IGBT is locked, allowing the grid voltage to uncontrolledly charge the DC capacitor through the IGBT's anti-parallel diode. When the real-time monitored DC voltage exceeds a set value, the bypass switch is closed to short-circuit the resistor, and the IGBT is unlocked, allowing the grid voltage to perform voltage equalization and controllable charging of the capacitor through the IGBT. This method achieves a smooth transition through phased control—in the uncontrolled charging stage, resistor current limiting and diode rectification are used to suppress inrush current and protect the capacitor; after the voltage reaches the threshold, the system switches to the controllable charging stage, where the IGBT actively regulates the current to ensure voltage equalization and stability during charging, thereby adapting to the three-phase H-bridge structure and optimizing energy transfer efficiency. This method simplifies the control process, reduces dependence on external components, effectively reduces system cost and size, improves outdoor environmental adaptability and reliability, and solves the problems of existing technologies being unable to match three-phase circuits, lacking bypass functionality, and being limited in outdoor applications, achieving an efficient, compact, economical, and reliable SVG starting process. Attached Figure Description

[0022] Figure 1 A schematic diagram of a star-connected topology of a two-phase start-up circuit for an SVG provided in an embodiment of the present invention; Figure 2 A schematic diagram of the corner connection topology of a two-phase start-up circuit for an SVG provided in an embodiment of the present invention; Figure 3 The three-phase startup three-phase current waveform diagram provided in the embodiment of the present invention; Figure 4 This is a waveform diagram of the three-phase current during star-connected two-phase startup provided in an embodiment of the present invention; Figure 5 This is a waveform diagram of the three-phase current during two-phase startup provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the two-phase start-up circuit structure of an outdoor SVG provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the two-phase start-up circuit structure of an indoor SVG provided in an embodiment of the present invention.

[0023] Figure label: 1. Pole post; 2. Transmission mechanism; 3. Housing; 4. Insulating pull rod; 5. Spring operating mechanism box; 6. Operation control box. Detailed Implementation

[0024] To make the technical problems solved by the present invention, the technical solutions, and the beneficial effects clearer, the following specific embodiments provide a further detailed description of the present invention. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0028] The technical terms used in this invention are explained below: SVG, short for Static Var Generator, is a reactive power compensation device consisting of voltage source converters connected in parallel to the system. Its output capacitive or inductive reactive current is continuously adjustable and independent of the system voltage within the operating system voltage range. When used in power distribution systems, it is also known as a distribution static synchronous compensator (D-STATCOM).

[0029] Grid-based SVG: As a core supporting technology for new power systems, it addresses grid stability issues caused by the high proportion of renewable energy integration. With the high penetration rate of renewable energy and power electronic equipment, power systems are showing a trend of inertia loss and weakening system strength, leading to increasingly serious stability problems. Grid-based SVG can provide instantaneous and rapid reactive power support during system faults, supporting system voltage. It outperforms conventional SVG in response speed and overload capacity, becoming a key device for building new power systems. Compared to traditional grid-following SVG, it achieves proactive and rapid voltage support in control, with a faster response speed, enabling reactive power support and short-term high-multiplier overload, achieving a strategic leap from "following" to "grid-building." It helps improve the independent controllability of technical equipment, promotes the development of the entire industry chain, plays a crucial role in addressing the challenges brought by large-scale renewable energy integration, and contributes to the green and low-carbon transformation of energy.

[0030] As mentioned in the background section, SVG has the characteristics of high power density, small footprint and easy maintenance. Therefore, how to design a small, easy-to-maintain and standardized AC start-up circuit is a problem that needs to be solved.

[0031] To address the aforementioned issues, this embodiment provides a dual-phase starting circuit for SVG. This circuit adopts a dual-phase starting circuit design, which can effectively solve the problems of high cost and large size of outdoor SVG starting circuits.

[0032] This embodiment provides a two-phase start-up circuit for an SVG, including: an SVG input side and an SVG valve side connected together; wherein each phase of the SVG input side is connected to each phase of the AC side. Any two of the three phases on the SVG valve side are connected to a starting resistor, while the other phase is not connected to a starting resistor. The starting resistor is connected between the corresponding phase of the SVG input line side and the SVG valve side; The two starting resistors are respectively connected in parallel to corresponding bypass switches; The bypass switch can switch the starting resistor between connected and short-circuited states through opening and closing operations; When the bypass switch is in the open state, the corresponding starting resistor is connected to the circuit to form a three-phase asymmetrical charging circuit to achieve uncontrolled charging. When the bypass switch is in the closed state, the corresponding starting resistor is short-circuited to form a three-phase symmetrical conduction circuit, thereby achieving controllable charging.

[0033] The dual-phase start-up circuit of the SVG provided in this embodiment will be further described below with reference to the accompanying drawings: like Figure 1 As shown, this embodiment provides a two-phase starting circuit for an SVG, such as... Figure 1 and Figure 2 As shown in this embodiment, a two-phase starting circuit for an SVG is disclosed. This circuit is a self-excited starting type. When the upstream main circuit breaker closes, the SVG device can automatically enter the charging state. This circuit, through a reasonable structural design, can achieve orderly switching between uncontrolled and controlled charging, while also considering cost control and operational stability. It is suitable for 35kV outdoor scenarios and 10kV indoor scenarios, and can be matched with... Figure 1 Star-connected topology and Figure 2 There are two connection forms for the corner joint topology.

[0034] In this embodiment, the two-phase starting circuit of the SVG mainly includes the connected SVG input side and SVG valve side. The SVG input side is connected to each phase (phase A, phase B, and phase C) of the AC side, forming the basic current path of the circuit. In the three-phase line of the SVG valve side, a special structure with two-phase starting resistors is adopted. In this embodiment, taking the absence of a starting resistor on phase B as an example, specifically, phases A and C on the SVG valve side are connected to starting resistors, while phase B is not connected to a starting resistor. The aforementioned starting resistors are all connected between the corresponding phases of the SVG input side and the SVG valve side. That is, the starting resistor of phase A is connected in series between phase A on the SVG input side and phase A on the SVG valve side, and the starting resistor of phase C is connected in series between phase C on the SVG input side and phase C on the SVG valve side. To switch the operating state of the starting resistors, each of the two starting resistors is connected in parallel with a corresponding bypass switch. This bypass switch can be a circuit breaker or a contactor; this embodiment uses a circuit breaker. The opening and closing operation of the circuit breaker allows the starting resistors to switch between connected and short-circuited states. When the bypass switch is open, the corresponding starting resistor is connected to the circuit, forming a three-phase asymmetrical charging circuit for uncontrolled charging. When the bypass switch is closed, the corresponding starting resistor is short-circuited, forming a three-phase symmetrical conducting circuit for controlled charging. It should be noted that phase A or phase C can also be without a starting resistor; the structure and principle are the same as in this embodiment and will not be repeated here.

[0035] In this embodiment, to ensure the safety of circuit operation and meet maintenance requirements, a disconnecting switch is connected to the incoming side of each of the three phases of the SVG. One end of the disconnecting switch is connected to the incoming side of the SVG, and the other end is connected to the SVG valve side. A grounding wire is also led out between the other end of the disconnecting switch and the SVG valve side. A grounding switch is installed on the grounding wire, and the grounding protection function of the circuit can be realized by opening and closing the grounding switch. At the same time, a reactor is connected to the incoming end of each phase of the SVG valve side. In the A and C phases of the SVG valve side, which have starting resistors, the reactor is connected between the starting resistor and the SVG valve side. That is, the A phase reactor is connected in series between the A phase starting resistor and the A phase of the SVG valve side, the C phase reactor is connected in series between the C phase starting resistor and the C phase of the SVG valve side, and the B phase reactor is directly connected in series between the B phase of the SVG incoming side and the B phase of the SVG valve side. For different application scenarios, this two-phase starting circuit can adopt either a star topology or a delta topology. In the star topology, the outgoing terminals of all three phases on the SVG valve side are connected to the same star neutral point. In the delta topology, the outgoing terminal of phase A on the SVG valve side is connected to the incoming terminal of phase B on the SVG valve side, the outgoing terminal of phase B on the SVG valve side is connected to the incoming terminal of phase C on the SVG valve side, and the outgoing terminal of phase C on the SVG valve side is connected to the incoming terminal of phase A on the SVG valve side. Both topologies eliminate the phase B starting resistor and phase B switch, maximizing the safety air distance and saving phase B circuit costs while ensuring mechanical and electrical topology symmetry. To monitor the circuit current, Hall sensors are connected to the outgoing terminals of each phase on the SVG valve side, which can collect data of each phase in real time, providing a basis for circuit control and protection.

[0036] For example, based on the above-mentioned two-phase starting circuit of the SVG, the corresponding control method is as follows: When the SVG needs to be started, the upstream main circuit breaker is first closed, and the SVG then enters the charging state. At this time, both bypass switches are controlled to be in the open state, so that the starting resistors of phase A and phase C are connected to the circuit. At the same time, the IGBT on the valve side of the SVG remains in the locked state, and the grid voltage charges the capacitor inside the SVG through the anti-parallel diode of the IGBT, entering the uncontrolled charging process. The uncontrolled charging process lasts for about 0.2 seconds. During this process, since phase B has no starting resistor, the starting current will exhibit three-phase asymmetry characteristics regardless of whether it is a star connection topology or a delta connection topology. At this time, the unbalanced current protection can be temporarily shielded by the control system to avoid protection malfunction, until the capacitor charging tends to saturate and the current gradually changes to 0A. During this period, Hall effect sensors monitor the current of each phase in real time, while the control system acquires the DC voltage of the SVG valve-side module in real time via optical fiber. When the real-time acquired DC voltage value exceeds the set DC voltage value, it indicates that the uncontrolled charging phase has been completed. The control system then issues a bypass switch closing command, controlling both bypass switches to close, short-circuiting the starting resistors of phases A and C. At this time, the IGBTs on the SVG valve side are unlocked, and the grid voltage charges the capacitors through the IGBTs, entering the controlled charging process. During the controlled charging process, the voltage of the IGBT-conducting module is raised by turning off the control module's IGBTs, alternating until the voltage of all modules reaches the set value. This process lasts approximately 0.3 seconds. After the module voltages stabilize, the control system delays for 10 seconds, causing the SVG to automatically switch to grid-connected operation. Subsequently, the SVG performs corresponding reactive power compensation operations according to the reactive power demand command of the grid, completing the entire startup process.

[0037] like Figure 3 As shown, all three phases have starting resistors. There is no controlled charging stage. The starting current is symmetrical across the three phases, gradually decreasing to 0A as the capacitor approaches saturation. The switch closes, entering the controlled charging stage. Figure 4 As shown, phase AC has a starting resistor, while phase B does not. There is no controlled charging circuit. The star-connected starting current is asymmetrical across the three phases, which can temporarily shield the unbalanced current protection. Once the current gradually decreases to 0 A, approaching capacitor saturation, the switch closes, entering the controlled charging circuit. For example... Figure 5 As shown, phase AC has a starting resistor, while phase B does not. There is no controlled charging circuit. The three-phase starting current is asymmetrical, which can temporarily shield the unbalanced current protection. Once the current gradually decreases to 0 A, approaching capacitor saturation, the switch closes, entering the controlled charging circuit. Therefore, this embodiment of the SVG dual-phase starting circuit achieves small size and low cost while maintaining operational performance.

[0038] like Figure 6As shown, for a 35kV outdoor application scenario, this two-phase starting circuit uses an outdoor three-phase disconnect switch and an outdoor two-phase circuit breaker as bypass switches. The outdoor three-phase reactor is arranged close to the SVG valve side, and the outdoor two-phase starting resistor is placed on the conductive bracket on top of the AC reactor. The specific wiring is as follows: the A-phase incoming line is connected to the upper port of the A-phase circuit breaker; the upper port of the A-phase circuit breaker is connected to the top copper busbar of the A-phase starting resistor via a copper busbar; the bottom copper busbar of the A-phase starting resistor is connected to the incoming copper busbar of the A-phase reactor; and the outgoing copper busbar of the A-phase reactor is connected to the A side of the SVG valve. The lower port of phase A circuit breaker is connected to the incoming copper busbar of phase A reactor via a copper busbar; the incoming line of phase C is connected to the upper port of phase C circuit breaker, and the upper port of phase C circuit breaker is connected to the top copper busbar of phase C starting resistor via a copper busbar; the bottom copper busbar of phase C starting resistor is connected to the incoming copper busbar of phase C reactor; the outgoing copper busbar of phase C reactor is connected to the C side of SVG valve; the lower port of phase C circuit breaker is connected to the incoming copper busbar of phase C reactor via a copper busbar; the incoming line of phase B is connected to the incoming copper busbar of phase B reactor, and the outgoing copper busbar of phase B reactor is connected to the B side of SVG valve; there is no phase B circuit breaker or starting resistor. During uncontrolled charging, the AC phase circuit breaker is open, and the AC phase starting resistor is connected in series with the circuit. Phase B forms an asymmetrical uncontrolled charging circuit within the phase through the neutral star contact of the SVG valve. Specifically, the AB phase circuit is: A phase - A phase starting resistor - A phase reactor - SVG valve A - star contact - SVG valve BB phase reactor - B phase, with a resistance of 1 pu. The AC phase circuit is: A phase - A phase starting resistor - A phase reactor - SVG valve A - star contact - SVG valve CC phase reactor - C phase starting resistor - C phase, with a resistance of 2 pu. The BC phase circuit is: B phase - B phase reactor - SVG valve B - star contact - SVG valve CC phase reactor - C phase starting resistor - C phase, with a resistance of 1 pu. During controlled charging, the AC phase circuit breaker is closed, and the AC phase starting circuit is short-circuited, forming a symmetrical structure for the three-phase starting circuits. The resistances of the AB, AC, and BC phase circuits are all 0 pu. The outdoor circuit structure includes components such as pole post 1, transmission mechanism 2, housing 3, insulating pull rod 4, spring operating mechanism box 5, and operation control box 6.

[0039] like Figure 7 As shown, for 10kV indoor applications, an indoor three-phase contactor is used as a bypass switch. Similarly, the B-phase starting resistor and B-phase switch are eliminated. The wiring logic is the same as that of the 35kV outdoor scenario. It is suitable for star and delta connection starting circuits. While ensuring operating performance, it effectively controls the size and footprint of the equipment and facilitates maintenance.

[0040] In summary, the two-phase starting circuit and control method for SVG provided by this invention have the following advantages compared with existing starting circuit methods: In star or delta connection circuits, two phases have starting resistors, while the other phase does not. There is no controlled charging stage. The starting current in a star connection is asymmetrical across the three phases, which can be temporarily shielded from unbalanced current protection. Once the current gradually decreases to 0 A, approaching capacitor saturation, the switch closes, entering the controlled charging stage. Eliminating one phase of the circuit saves costs, reduces equipment footprint, and increases SVG power density. This starting circuit is easy to maintain, and the control and protection system is simple and easy to implement. The system is low-cost, lightweight, and requires little space. This circuit can be applied to other chain topologies, saving costs and increasing market share.

[0041] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

Claims

1. A two-phase start-up circuit for an SVG, characterized by, The SVG comprises: a SVG incoming line side and a SVG valve side connected to each other; each phase of the SVG incoming line side is connected to a corresponding phase of the SVG valve side; any two phases of the SVG valve side are connected with a starting resistor, and the other phase is not connected with a starting resistor; the starting resistor is connected between the corresponding phase of the SVG incoming line side and the SVG valve side; each of the two starting resistors is connected in parallel with a corresponding bypass switch; the bypass switch can switch the starting resistor between the connected state and the short-circuited state through opening and closing operation; when the bypass switch is in the open state, the corresponding starting resistor is connected to the circuit to form a three-phase asymmetric charging circuit to realize uncontrolled charging; 2. A dual phase start circuit for an SVG according to claim 1, wherein, when the bypass switch is in the closed state, the corresponding starting resistor is short-circuited to form a three-phase symmetric conduction circuit to realize controlled charging.

3. A dual phase start circuit for an SVG according to claim 2, wherein, An isolating switch is connected to each phase of the SVG incoming line side. One end of the isolating switch is connected to the SVG incoming line side, and the other end is connected to the SVG valve side; 4. The dual phase start circuit for an SVG as claimed in claim 1 wherein, a grounding wire is further led between the other end of the isolating switch and the SVG valve side, and a grounding knife is arranged on the grounding wire.

5. A dual phase start circuit for an SVG according to claim 1, wherein, An electric reactor is connected to the incoming end of each phase of the SVG valve side; and in the SVG valve side phase with the starting resistor, the electric reactor is connected between the starting resistor and the SVG valve side.

6. A dual phase start circuit for an SVG according to claim 5, wherein, The two-phase starting circuit adopts a star-connected topology or an angle-connected topology.

7. A dual phase start circuit for an SVG according to claim 5 wherein, In the star-connected topology, the outgoing ends of the three phases of the SVG valve side are connected to the same star-shaped neutral point.

8. A dual phase start circuit for an SVG according to claim 1, wherein, In the angle-connected topology, the outgoing end of the SVG valve side A phase is connected to the incoming end of the SVG valve side B phase, the outgoing end of the SVG valve side B phase is connected to the incoming end of the SVG valve side C phase, and the outgoing end of the SVG valve side C phase is connected to the incoming end of the SVG valve side A phase.

9. The dual phase start circuit for an SVG as claimed in claim 1 wherein, A Hall sensor is connected to the outgoing end of each phase of the SVG valve side.

10. A control method of a two-phase starting circuit of an SVG, characterized by, The bypass switch adopts a circuit breaker or a contactor to switch the connection and short-circuit of the starting resistor. The two-phase starting circuit of the SVG according to any one of claims 1-9 comprises: after the SVG enters the charging state, the bypass switch is opened to connect the starting resistor, the IGBT of the SVG valve side is locked, the grid voltage charges the capacitor through the anti-parallel diode of the IGBT, and the uncontrolled charging process is entered; when the real-time acquisition value of the DC voltage exceeds the set value of the DC voltage, the bypass switch is closed to short-circuit the starting resistor, the IGBT of the SVG valve side is unlocked, the grid voltage charges the capacitor through the IGBT, and the controlled charging process is entered.

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