An active energy storage multi-winding transformer type adjustable reactor and a control method thereof

Abstract

This invention proposes an active energy storage type multi-winding transformer-type adjustable reactor and its control method, belonging to the technical field of power electronics and flexible AC transmission and distribution systems. It includes a multi-winding transformer, whose primary winding is electrically connected to the AC power grid; at least one set of thyristor hierarchical switching circuits, which are connected in series with the corresponding thyristor-switching windings on the secondary side of the multi-winding transformer; the AC side of a PWM inverter control circuit is electrically connected to one of the active control windings on the secondary side of the multi-winding transformer; an energy storage module is connected in parallel on the DC side of the PWM inverter control circuit to inject a compensation current containing reactive and active components into the active control winding, thereby achieving continuous fine-tuning of the equivalent reactance value and active power exchange with the AC power grid. This invention can be applied as a multifunctional power electronic device in fields such as smart grids, new energy transmission and distribution, and comprehensive power quality management.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology and flexible AC power transmission and distribution system technology, and more specifically, relates to an active energy storage type multi-winding transformer-type adjustable reactor and its control method. Background Technology

[0002] Adjustable reactors are key devices in power systems used for dynamic reactive power compensation, fault current limiting, arc suppression, and voltage stabilization. Traditional adjustable reactors, such as thyristor-controlled reactors (TCRs), magnetic valve reactors, and DC bias reactors, while capable of regulating reactive power, generally suffer from high harmonic content, slow response speed, limited adjustment range, or are limited to reactive power regulation only. In recent years, adjustable reactors based on the flux control principle have achieved continuous, smooth, and harmonic-free adjustment of the equivalent reactance value by injecting compensation current into the secondary side of the transformer through an active inverter, significantly improving performance.

[0003] However, existing flux-controlled adjustable reactors are still limited to reactive power regulation and cannot interact with the grid for active power. With the increasing penetration of renewable energy (such as wind and solar power) and the development of smart grids, the demand for composite power electronic equipment capable of simultaneously and flexibly regulating both active and reactive power is becoming increasingly urgent. For example, in renewable energy power plants, reactive power compensation is needed to maintain voltage stability, while energy storage systems are required to smooth power fluctuations and provide frequency support. Currently, reactive power compensation devices (such as SVG) and power storage converters (PCS) are typically deployed separately, resulting in complex systems, high costs, and large space requirements. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides an active energy storage type multi-winding transformer adjustable reactor and its control method, thereby solving the technical problems of separate deployment of reactive power compensation device and energy storage converter in the prior art, which leads to system complexity, high cost and large space occupation.

[0005] To achieve the above objectives, according to one aspect of the present invention, an active energy storage type multi-winding transformer adjustable reactor is provided, including a multi-winding transformer, a thyristor staged switching circuit, and a PWM inverter control circuit. The primary winding of the multi-winding transformer is electrically connected to the AC power grid. The thyristor graded switching circuit is provided in at least one set, and the thyristor graded switching circuit is connected in series with the corresponding thyristor switching winding in the secondary side of the multi-winding transformer, for graded coarse adjustment of the equivalent reactance value of the reactor. The AC side of the PWM inverter control circuit is electrically connected to one of the active control windings on the secondary side of the multi-winding transformer; the DC side of the PWM inverter control circuit is connected in parallel with an energy storage module, which is used to inject a compensation current containing reactive and active components into the active control winding to achieve continuous fine adjustment of the equivalent reactance value and active power exchange with the AC power grid.

[0006] Preferably, the energy storage module includes a battery pack, a supercapacitor pack, or a hybrid energy storage system.

[0007] Preferably, the secondary side of the multi-winding transformer includes N thyristor switching windings, where N≥1; each thyristor switching winding is connected in series with a thyristor switch to form a series branch, and the series branches are connected in series or in parallel with each other.

[0008] Preferably, the PWM inverter control circuit is an inverter bridge composed of IGBTs.

[0009] Preferably, the primary winding is connected in series or in parallel to the AC power grid.

[0010] Preferably, it also includes a central control unit, which generates a reactive current command based on the reactive power demand of the power grid and generates an active current command based on the active power interaction demand. The reactive current command and the active current command are combined into a comprehensive current command, and the PWM inverter control circuit is controlled to inject compensation current into the active control winding based on the comprehensive current command.

[0011] According to one aspect of the present invention, a control method for an active energy storage type multi-winding transformer-type adjustable reactor is provided, comprising the following steps: The central control unit controls the thyristor tiered switching circuit to coarsely adjust the tiered equivalent reactance value according to the target equivalent reactance value; The central control unit generates a reactive current command based on the detected electrical quantities of the power grid, and controls the PWM inverter control circuit to inject the corresponding reactive current into the active control winding, thereby achieving continuous fine adjustment of the equivalent reactance value. The central control unit generates an active current command based on the active power exchanged with the power grid, and superimposes it on the reactive current command to form a comprehensive current command; and controls the PWM inverter control circuit to inject a compensation current containing active and reactive components into the active control winding to realize bidirectional active power exchange with the power grid.

[0012] Preferably, it also includes an equivalent reactance continuous adjustment mode, in which the active current command is zero, and the PWM inverter control circuit only outputs reactive current to finely adjust the equivalent reactance value.

[0013] Preferably, it also includes an active-reactive power combined regulation mode, in which the central control unit simultaneously generates non-zero active current commands and non-zero reactive current commands, so that the reactor can simultaneously perform continuous adjustment of the equivalent reactance value and bidirectional active power exchange with the power grid.

[0014] Preferably, the active current command is generated as follows: based on the grid frequency deviation or power dispatch command, the required active power exchange value is calculated by a PI regulator, and then the active current command is obtained.

[0015] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: 1. The active energy storage type multi-winding transformer adjustable reactor proposed in this invention simultaneously sets up a thyristor switching winding and an active control winding on the multi-winding transformer. The thyristor switching winding and the active control winding are respectively connected to the thyristor hierarchical switching circuit and the PWM inverter control circuit. At the same time, an energy storage module is connected in parallel on the DC side of the PWM inverter control circuit, so that the reactor can realize the functions of an adjustable reactor and an energy storage converter at the same time, reducing the number of devices, reducing system cost, floor space and complexity.

[0016] 2. The active energy storage type multi-winding transformer adjustable reactor proposed in this invention achieves a wide range of stepped adjustment of the equivalent reactance value (coarse adjustment) by thyristor-stage switching of multiple sets of secondary side switching windings; then, by injecting a continuous and controllable reactive current into the active control winding through a PWM inverter control circuit, fine compensation of residual error is achieved (fine adjustment). This invention adopts a hybrid adjustment strategy of "staged coarse adjustment + continuous fine adjustment", which significantly widens the overall adjustment range of the equivalent reactance value and does not generate low-order harmonics in the entire adjustment process, eliminating the need for additional filters.

[0017] 3. The active energy storage type multi-winding transformer-type adjustable reactor proposed in this invention can complete the coarse adjustment response within several power frequency cycles through thyristor switching, while the current response time of the PWM inverter control circuit can reach the millisecond level to compensate for the residual error after coarse adjustment. The central control unit quickly generates reactive current commands by real-time detection of grid voltage, primary side current, and DC bus voltage, and controls the inverter output in a closed loop, achieving high-precision tracking of the equivalent reactance value. The reactor of this invention has fast response speed and high adjustment accuracy.

[0018] 4. The active energy storage type multi-winding transformer adjustable reactor proposed in this invention can flexibly set reactive current commands and active current commands through the central control unit, support multiple working modes, and flexibly adapt to different application scenarios. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the active energy storage type multi-winding transformer adjustable reactor of the present invention.

[0020] Figure 2 This is a schematic diagram of the central control unit in an embodiment of the active energy storage type multi-winding transformer adjustable reactor of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0022] This invention proposes an active energy storage type multi-winding transformer adjustable reactor, which includes a multi-winding transformer, multiple thyristor hierarchical switching circuits, a PWM inverter control circuit with a parallel large-capacity energy storage module, and a central control unit.

[0023] Specifically, the primary winding of the multi-winding transformer ( The multi-winding transformer is connected in series or parallel to the AC power grid; the secondary side of the multi-winding transformer includes N switching windings connected in series through thyristors. , ,..., ), where N≥1; includes an active fine-tuning control winding ( Its AC side port is connected to a controllable converter, and its DC side port at the back end of the IGBT is connected in parallel to the energy storage module; through control, the equivalent reactance value can be continuously adjusted and the active power exchange between the energy storage module and the AC grid can be realized.

[0024] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0025] Example 1 like Figure 1 As shown, the active energy storage type multi-winding transformer adjustable reactor of the present invention includes a multi-winding transformer T, four sets of thyristor hierarchical switching circuits, a PWM inverter control circuit for a parallel large-capacity energy storage module (such as a supercapacitor bank), and a central control unit.

[0026] The primary winding of the multi-winding transformer T It is connected to the power grid via a circuit breaker. The secondary side contains N (N=4 in the diagram) thyristor switching windings. , , , and one PWM control winding The secondary-side thyristor switching winding passes through the thyristor. Series connection, the secondary-side PWM control winding is connected to the inverter bridge (by IGBT module) ~ (Constructed by, etc.), the DC side of the inverter bridge unit is connected in parallel to the energy storage element. The central control unit collects the grid voltage. Primary side current , , Secondary current , , and DC bus voltage Wait for the signal.

[0027] like Figure 2 As shown, the core control strategies of the central control unit include: Reactance value calculation and instruction generation: Obtain the target reactance value based on the detection circuit. Based on the parameters of each switching winding of the transformer, determine the thyristor Which one is turned on allows for a wide range of coarse adjustments to the reactance value, while simultaneously confirming the reactance value of the thyristor switching winding. ,Depend on and The reactive current command of the IGBT control circuit is calculated by measuring the difference between the two values, as well as the primary harmonics and reactive current components. This enables precise adjustment of reactive power.

[0028] Active power command generation: based on output power reference value command With actual power P out The deviation is used to generate a total active current command through a PI regulator. This command can also be given directly by the power grid system. The active current command... With reactive current command The data is then synthesized to form the final current command. . = By using PWM control (such as triangular wave comparison), drive signals are generated for each IGBT, controlling the inverter bridge to output the desired current.

[0029] when When the voltage is >0, the converter is required to inject active power into the grid (discharge), and the secondary side current command generates a component in phase with the grid voltage; when When the voltage is less than 0, the converter is required to absorb active power from the grid (charge), and the secondary side current command will generate a component that is opposite to the grid voltage. Through the magnetic coupling of the transformer, this active power component is reflected on the primary side, realizing active power exchange with the grid.

[0030] The following is an example of the operation of the reactor in this embodiment of the invention: 1. Reactive power compensation: The power grid requires reactive power support, so it is necessary to set... For a specific value, =0. The device only regulates reactive power to maintain voltage stability.

[0031] 2. Active power interaction: When the grid frequency decreases, power support is required. Control loop output >0, the device injects active power into the grid while maintaining the current reactance value, thereby increasing the frequency.

[0032] 3. Hybrid mode: Reactive power compensation and active power smoothing are performed simultaneously. For example, in a photovoltaic power station, active power is injected and reactive power is compensated when generating electricity during the day, and active power is absorbed (charged) and reactive power is regulated at night.

[0033] Example 2 This invention also proposes a control method for an active energy storage type multi-winding transformer-type adjustable reactor, comprising the following steps: The central control unit controls the thyristor tiered switching circuit to coarsely adjust the tiered equivalent reactance value according to the target equivalent reactance value; The central control unit generates a reactive current command based on the detected electrical quantities of the power grid, and controls the PWM inverter control circuit to inject the corresponding reactive current into the active control winding, thereby achieving continuous fine adjustment of the equivalent reactance value. The central control unit generates an active current command based on the active power exchanged with the power grid, and superimposes it on the reactive current command to form a comprehensive current command; and controls the PWM inverter control circuit to inject a compensation current containing active and reactive components into the active control winding to realize bidirectional active power exchange with the power grid.

[0034] Further explanation includes an equivalent reactance continuous adjustment mode, in which the active current command is zero, and the PWM inverter control circuit only outputs reactive current to finely adjust the equivalent reactance value.

[0035] Furthermore, it also includes an active-reactive power combined regulation mode. In this mode, the central control unit simultaneously generates non-zero active current commands and non-zero reactive current commands, so that the reactor can simultaneously perform continuous adjustment of the equivalent reactance value and bidirectional active power exchange with the power grid.

[0036] To further explain, the active current command is generated as follows: based on the grid frequency deviation or power dispatch command, the required active power exchange value is calculated by a PI regulator, and then the active current command is obtained.

[0037] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An active energy storage type multi-winding transformer-type adjustable reactor, characterized in that, This includes a multi-winding transformer, a thyristor staged switching circuit, and a PWM inverter control circuit; The primary winding of the multi-winding transformer is electrically connected to the AC power grid. The thyristor graded switching circuit is provided in at least one set, and the thyristor graded switching circuit is connected in series with the corresponding thyristor switching winding in the secondary side of the multi-winding transformer, for graded coarse adjustment of the equivalent reactance value of the reactor. The AC side of the PWM inverter control circuit is electrically connected to one of the active control windings on the secondary side of the multi-winding transformer; the DC side of the PWM inverter control circuit is connected in parallel with an energy storage module, which is used to inject a compensation current containing reactive and active components into the active control winding to achieve continuous fine adjustment of the equivalent reactance value and active power exchange with the AC power grid.

2. The active energy storage type multi-winding transformer-type adjustable reactor according to claim 1, characterized in that, The energy storage module includes a battery pack, a supercapacitor pack, or a hybrid energy storage system.

3. The active energy storage type multi-winding transformer-type adjustable reactor according to claim 1, characterized in that, The secondary side of the multi-winding transformer includes N thyristor switching windings, where N≥1; each thyristor switching winding is connected in series with a thyristor switch to form a series branch, and the series branches are connected in series or in parallel with each other.

4. The active energy storage type multi-winding transformer-type adjustable reactor according to claim 1, characterized in that, The PWM inverter control circuit is an inverter bridge composed of IGBTs.

5. The active energy storage type multi-winding transformer-type adjustable reactor according to claim 1, characterized in that, The primary winding is connected in series or in parallel to the AC power grid.

6. An active energy storage type multi-winding transformer-type adjustable reactor according to any one of claims 1-5, characterized in that, It also includes a central control unit, which generates a reactive current command based on the reactive power demand of the power grid and an active current command based on the active power interaction demand. The central control unit combines the reactive current command and the active current command into a comprehensive current command, and controls the PWM inverter control circuit to inject compensation current into the active control winding based on the comprehensive current command.

7. A control method for an active energy storage type multi-winding transformer-type adjustable reactor based on claim 6, characterized in that, Includes the following steps: The central control unit controls the thyristor tiered switching circuit to coarsely adjust the tiered equivalent reactance value according to the target equivalent reactance value; The central control unit generates a reactive current command based on the detected electrical quantities of the power grid, and controls the PWM inverter control circuit to inject the corresponding reactive current into the active control winding, thereby achieving continuous fine adjustment of the equivalent reactance value. The central control unit generates an active current command based on the active power exchanged with the power grid, and superimposes it on the reactive current command to form a comprehensive current command; and controls the PWM inverter control circuit to inject a compensation current containing active and reactive components into the active control winding to realize bidirectional active power exchange with the power grid.

8. The control method according to claim 7, characterized in that, It also includes an equivalent reactance continuous adjustment mode, in which the active current command is zero, and the PWM inverter control circuit only outputs reactive current to finely adjust the equivalent reactance value.

9. The control method according to claim 7, characterized in that, It also includes an active-reactive power combined regulation mode, in which the central control unit simultaneously generates non-zero active current commands and non-zero reactive current commands, so that the reactor can simultaneously perform continuous adjustment of the equivalent reactance value and bidirectional active power exchange with the power grid.

10. The control method according to claim 9, characterized in that, The active current command is generated as follows: based on the grid frequency deviation or power dispatch command, the required active power exchange value is calculated by a PI regulator, and then the active current command is obtained.

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