Wind, light and fire storage combined device, variable slope energy storage current conversion device and voltage control circuit

Abstract

The utility model relates to a wind, light and fire storage combined device, a variable slope energy storage current conversion device and a voltage control circuit. The voltage control circuit comprises a variable slope energy storage current conversion circuit and a droop control compensation circuit. The variable slope energy storage commutation circuit is used for suppressing an impact current in a black-start voltage buildup process; and the droop control compensation circuit is used for converting direct current into alternating current with controllable output. Through the droop control compensation circuit and the variable slope energy storage commutation circuit, not only can the stability of the frequency be maintained in the whole process of black start and the adverse effect on the system caused by the frequency fluctuation be prevented, but also the overshoot phenomenon of the voltage can be effectively inhibited and the voltage is always kept in a reasonable range. Therefore, the reliability and the stability of the black start process are remarkably improved, and a powerful guarantee is provided for stable operation of the wind-solar storage micro-grid in practical application.

Description

Technical Field

[0001] The present application relates to the technical field of wind, solar, thermal and storage combination, and specifically to a wind, solar, thermal and storage combination device, a variable slope energy storage commutation device and a voltage control circuit. Background Art

[0002] A black start is a process in which a generator set with self-starting capabilities starts up other generator sets within the system that lack self-starting capabilities, thereby restoring power to the system after a power outage. A well-designed black start plan allows for orderly recovery operations after a power outage, minimizing losses.

[0003] As the penetration of renewable energy generation continues to increase, the power system grid structure becomes increasingly complex. Wind and solar microgrids are often equipped with correspondingly large-scale energy storage equipment. Large-scale energy storage technology not only provides various services for the power grid, such as peak load regulation, frequency regulation, and emergency response, but also serves as a self-starting component within the wind and solar microgrid. This allows the microgrid to self-start, activate the auxiliary equipment of the thermal power plant on the opposite side of the transmission line, restore thermal power units, and gradually expand the scope of power system restoration, ultimately achieving overall system recovery. However, when operating in parallel with renewable energy storage and thermal power generation, transient fluctuations in system frequency and voltage remain a major challenge that needs to be addressed. When the wind, solar, and storage microgrid restores power and the transmission line is fully charged, the auxiliary equipment of the thermal power plant on the opposite side is activated, allowing the wind, solar, and storage-thermal power generation to operate in parallel, expanding the scope of black start power restoration. Unlike traditional motors, energy storage commutation devices lack inertia, so transient frequency and voltage fluctuations are common during active and reactive power regulation. These fluctuations negatively impact overall system stability and, in severe cases, can lead to black start failures. Utility Model Content

[0004] To overcome the above-mentioned deficiencies of the prior art, the present application provides a wind-solar-thermal-storage combined device, a variable slope energy storage commutation device, and a voltage control circuit, specifically adopting the following technical solutions:

[0005] A voltage control circuit for a variable slope energy storage commutation device, the voltage control circuit comprising a variable slope energy storage commutation circuit, the variable slope energy storage commutation circuit being used to suppress inrush current during a black start voltage building process;

[0006] The variable slope energy storage commutation circuit includes an equivalent capacitor circuit, a first current conversion circuit, a boost circuit, a first filter circuit, a second current conversion circuit and a second filter circuit, wherein the boost circuit includes a low-voltage side and a high-voltage side, the equivalent capacitor circuit and the first current conversion circuit are located on the low-voltage side of the boost circuit, and the first filter circuit, the second current conversion circuit and the second filter circuit are located on the high-voltage side of the boost circuit; the equivalent capacitor circuit, the first current conversion circuit and the low-voltage side of the boost circuit are connected in series to form a first circuit loop, and the first filter circuit, the second current conversion circuit, the second filter circuit and the high-voltage side of the boost circuit form a second current loop.

[0007] Optionally: the voltage control circuit also includes a droop control compensation circuit, the droop control compensation circuit includes at least one group of unit compensation circuits, the unit compensation circuits are connected in parallel to the equivalent capacitance circuit, and the unit compensation circuits are used to convert direct current into output controllable alternating current.

[0008] Optionally: the equivalent capacitance device includes a first capacitor and a first resistor connected in parallel, and the droop control compensation circuit is connected in parallel to both ends of the first resistor.

[0009] Optional: The unit compensation circuit includes an energy storage power supply, a first inductor, a first MOS transistor, a second MOS transistor and a second capacitor, wherein the positive electrode of the energy storage power supply is connected in series with the first inductor and the emitter of the first MOS transistor in sequence, and the collector of the first MOS transistor is connected in parallel to one end of the first resistor in the equivalent capacitor circuit; the negative electrode of the energy storage power supply is connected in parallel to the other end of the first resistor in the equivalent capacitor circuit; one end of the second capacitor is connected in parallel to the collector of the first MOS transistor, and the other end is connected in parallel to the negative electrode of the energy storage power supply; the collector of the second MOS transistor is connected in parallel to the emitter of the first MOS transistor, and the emitter of the second MOS transistor is connected in parallel to the negative electrode of the energy storage power supply.

[0010] Optional: The first current conversion circuit adopts four groups of third MOS transistors, the four groups of third MOS transistors constitute a full-bridge inverter circuit, and the midpoints of the two bridge arms in the full-bridge inverter circuit are respectively provided with first connection points, and the first connection points of the two bridge arms are respectively connected to the low-voltage side of the boost circuit.

[0011] Optionally: the first filtering circuit uses a third capacitor and a second inductor arranged in series, and the first filtering circuit is used to suppress the impact current in the circuit.

[0012] Optional: The second current conversion circuit includes three columns of triode units arranged in parallel, each column of triode units includes two triode sub-units connected in series, and each triode sub-unit is provided with two anti-series fourth MOS triodes; wherein a second connection point is provided between the two triode sub-units in each column of triode units, and each second connection point is connected to a power transmission line.

[0013] Optional: The second filtering circuit includes three groups of fourth capacitors and three groups of third inductors, wherein each transmission line is connected in series with a third inductor, one end of each of the fourth capacitors is connected in parallel with a second connection point, and the other ends of the three groups of fourth capacitors are connected in parallel with each other.

[0014] In addition, the present application also discloses a variable slope energy storage commutation device, in which the voltage control circuit as described above is provided.

[0015] In addition, the present application also discloses a combined wind, solar, thermal and energy storage device, which includes an AC bus, and a photovoltaic power generation unit, a wind power generation unit, a thermal power generation unit and an energy storage unit connected in parallel to the AC bus, wherein the energy storage unit is provided with the variable slope energy storage commutation device as described above.

[0016] Beneficial effects

[0017] The technical solution of this application has the following beneficial effects:

[0018] (1) The variable slope energy storage commutation device of the present application adopts a parallel operation droop control compensation circuit, which can realize the smooth start of the auxiliary equipment of the opposite thermal power plant after the wind, solar and storage microgrid restores power supply and completes the empty charging of the transmission line, thereby realizing the parallel operation of the wind, solar and storage and thermal power systems, thereby expanding the power supply recovery range after the black start.

[0019] (2) The variable slope energy storage commutation device of the present application can ensure that the energy storage commutation unit performs active and reactive power regulation according to the droop coefficient when the energy storage system is operating in an isolated grid at the initial stage of black start, and needs to maintain the voltage and frequency within a certain range. The device can adjust the voltage frequency and voltage amplitude to output constant active and reactive power, avoiding the switching of different energy storage control modes during the black start process, simplifying the control system and improving reliability. In addition, based on the variable slope energy storage commutation device, the impact current during the black start voltage building process can be suppressed to ensure that the AC bus of the wind, solar and storage microgrid remains stable in the initial stage of black start.

[0020] (3) The voltage control circuit of this application, by introducing a droop control compensation circuit containing a nonlinear compensation module, can not only maintain frequency stability throughout the black start process and prevent adverse effects on the system caused by frequency fluctuations, but also effectively suppress voltage overshoot, ensuring that the voltage always remains within a reasonable range. This significantly improves the reliability and stability of the black start process, providing a strong guarantee for the stable operation of wind, solar and energy storage microgrids in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the variable slope energy storage commutation circuit in the embodiment of the present application.

[0022] Figure 2 Schematic diagram of the structure of the droop control compensation circuit in an embodiment of the present application.

[0023] Figure 3 This is a structural diagram of the wind, solar, thermal and storage combined device in the embodiment of this application. DETAILED DESCRIPTION

[0024] The present application will be further described below in conjunction with the accompanying drawings. The following examples are only used to more clearly illustrate the technical solutions of the present application and are not intended to limit the scope of protection of the present application. It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application.

[0025] Combine Figure 1 As shown, the embodiment of the present application specifically discloses a voltage control circuit of a variable slope energy storage commutation device, wherein the voltage control circuit includes a variable slope energy storage commutation circuit. The variable slope energy storage commutation circuit can maintain the stability of the AC bus of the wind-solar-storage microgrid during the initial stage of black start, that is, the energy storage zero-start boost and empty charging process. By introducing a variable slope transfer function module into the traditional reactive-voltage droop control, it can suppress the impact current in the black start voltage building process.

[0026] Specifically, the variable slope energy storage commutation circuit includes an equivalent capacitor circuit 1, a first current conversion circuit 2, a boost circuit 3, a first filter circuit 4, a second current conversion circuit 5 and a second filter circuit 6, wherein the boost circuit 3 includes a low-voltage side and a high-voltage side, the equivalent capacitor circuit 1 and the first current conversion circuit 2 are located on the low-voltage side of the boost circuit 3, and the first filter circuit 4, the second current conversion circuit 2 and the second filter circuit 6 are located on the high-voltage side of the boost circuit 3; the low-voltage side of the equivalent capacitor circuit 1, the first current conversion circuit 2 and the boost circuit 3 constitute a first circuit loop, and the first filter circuit 4, the second current conversion circuit 5, the second filter circuit 6 and the high-voltage side of the boost circuit 3 constitute a second current loop. It should be understood that in the embodiment of the present application, the equivalent capacitor circuit 1 is mainly used to organize the high-frequency signal of the first circuit loop; the first current conversion circuit 2 and the second current conversion circuit 5 selectively control the conduction state of the transistor through an external voltage, thereby realizing a change in the slope of the converter output voltage-current (VI) characteristic curve. The boost circuit 3 is used to realize the voltage amplification function. The first filter circuit 4 and the second filter circuit 6 can suppress the impact current in the second circuit loop to ensure the stability of the converter output.

[0027] In addition, since the energy storage converter has no inertia link when the wind-solar-storage microgrid restores power supply, there are often transient frequency and voltage fluctuations in the process of active and reactive power regulation, which have an adverse effect on the stability of the entire system. In severe cases, it will lead to black start failure. Therefore, in order to increase the robustness of the energy storage droop control system in the black start power supply recovery phase, this application adopts a frequency and voltage nonlinear compensation module as a nonlinear compensation circuit for active-frequency and reactive-voltage droop control. Specifically, Figure 2 As shown, the voltage control circuit described in the present application also includes a droop control compensation circuit, which includes at least one group of unit compensation circuits, and the unit compensation circuits are connected in parallel to the equivalent capacitor circuit 1. The unit compensation circuit is used to convert direct current into output controllable alternating current, and can detect fluctuations in grid frequency, and adjust the output of the droop controller through a nonlinear compensation algorithm to reduce the impact of frequency fluctuations on the system.

[0028] Specifically, the equivalent capacitor device 1 in this application includes a first capacitor C1 and a first resistor R connected in parallel. L , and the droop control compensation circuit is connected in parallel to the first resistor R L The droop control compensation circuit is applied to the first resistor R L On, through the first resistor R L The voltage applied to the droop control compensation circuit can be divided to ensure the stability of subsequent voltage fluctuations. In addition, by combining with the first capacitor C1, high-frequency signals in the circuit can be organized to filter or suppress signals in a specific frequency range.

[0029] In detail, the unit compensation circuit described in this application has two paths, one of which includes an energy storage power supply U in1 , a first inductor L1, a first MOS transistor Q1, a second MOS transistor Q2 and a second capacitor C1, wherein the energy storage power supply U in1 The positive electrode is connected in series with the first inductor L1 and the emitter of the first MOS transistor Q1, and the collector of the first MOS transistor Q1 is connected in parallel to the first resistor R in the equivalent capacitor circuit. L One end of the energy storage power supply U in1 The negative electrode is connected in parallel to the first resistor R in the equivalent capacitor circuit L The other end of the second capacitor C1 is connected in parallel to the collector of the first MOS transistor Q1, and the other end is connected in parallel to the energy storage power supply U in1 The collector of the second MOS transistor Q2 is connected in parallel to the emitter of the first MOS transistor Q1, and the emitter of the second MOS transistor Q2 is connected in parallel to the energy storage power supply U in1 of the negative electrode.

[0030] Similarly, the other circuit includes energy storage power supply U in2 , a first inductor L2, a first MOS transistor Q3, a second MOS transistor Q4 and a second capacitor C2, wherein the connection method of each component is consistent with the above-mentioned unit compensation circuit method. The energy storage power supply U in this application in1 and U in2 It primarily serves as an energy source, providing the required energy for the circuit system. The capacitors, inductors, and transistors in the circuit collectively form an inverter, converting the DC power in the energy storage device into AC power to meet the needs of the power grid. The unit compensation circuit, as a whole, comprises a droop controller and a frequency nonlinear compensation module. This module detects grid frequency fluctuations and adjusts the droop controller output using a nonlinear compensation algorithm to minimize the impact of frequency fluctuations on the system.

[0031] More specifically, the first current conversion circuit in this application employs four groups of third MOS transistors V1, V2, V3, and V4. These four groups of third MOS transistors V1, V2, V3, and V4 form a full-bridge inverter circuit, and the midpoints of the two bridge arms of the full-bridge inverter circuit are each provided with a first connection point, and the first connection points of the two bridge arms are respectively connected to the low-voltage side of the boost circuit. It should be noted that the bases of the four groups of third MOS transistors are each connected to an external voltage, and the conduction of the four groups of third MOS transistors can be controlled by the external voltage. The four groups of third MOS transistors can be used to change the slope of the voltage-current (V1) characteristic curve output by the first current conversion circuit.

[0032] Furthermore, the present application can realize voltage amplification through the boost circuit, and since some current fluctuations will be generated during the voltage amplification process, they can be suppressed by the first filter circuit. Specifically, the first filter circuit adopts a third capacitor C arranged in series. r and the second inductor L r , through the third capacitor C r and the second inductor L r Together they suppress the inrush current in the circuit.

[0033] More specifically, the second current conversion circuit in the present application includes three columns of triode units arranged in parallel, each column of triode units includes two triode sub-units connected in series, and each triode unit is provided with two fourth MOS triodes connected in anti-series, that is, the second current conversion circuit in the present application is provided with 12 groups of MOS triodes (V5-V 16 ); wherein a second connection point is provided between two triode sub-units in each column of triode units, and each second connection point is connected to a power transmission line. The second current conversion circuit can achieve the same function as the first current conversion circuit, namely, by controlling the conduction state of different triodes, the slope of the voltage-current (V1) characteristic curve of the circuit output can be changed.

[0034] Furthermore, the second filtering circuit includes three groups of fourth capacitors C a 、C b 、C c And three sets of third inductors L a 、L b 、L c In this application, the three transmission lines are A-phase transmission line, B-phase transmission line and C-phase transmission line, wherein the A-phase transmission line is connected in series with a third inductor L a , the fourth capacitor C a One end of the inductor is connected in parallel to the second connection point connected to the A-phase transmission line. Similarly, a third inductor L is connected in series on the B-phase transmission line. b , the fourth capacitor C b One end of the second connection point is connected in parallel to the B-phase transmission line. A third inductor L is connected in series on the C-phase transmission line. c , the fourth capacitor C c One end of the fourth capacitor C is connected in parallel to the second connection point connected to the C phase transmission line. a 、C b 、C c The other ends of the two filters are connected in parallel. The second filter circuit can further suppress the inrush current in the circuit to ensure stable output.

[0035] In addition, the present application also discloses a combined wind, solar, thermal and energy storage device, which includes an AC bus, and a photovoltaic power generation unit, a wind power generation unit, a thermal power generation unit and an energy storage unit connected in parallel to the AC bus, wherein the energy storage unit is provided with the variable slope energy storage commutation device as described above.

[0036] Combine Figure 3 As shown, the photovoltaic power generation unit includes a photovoltaic component, a first inverter device, a first boost transformer and a first grid-connected switch. The photovoltaic component is connected to the AC bus through the first inverter device, the first boost transformer and the first grid-connected switch K1.

[0037] The wind power generation unit includes a wind turbine, a back-to-back commutation device, a second step-up transformer, and a second grid-connected switch. The wind turbine is sequentially connected to the AC busbar via the back-to-back commutation device, the second step-up transformer, and the second grid-connected switch K2. The energy storage unit includes an energy storage device, a commutation device, and a third step-up transformer. The energy storage device is sequentially connected to the AC busbar via the commutation device and the third step-up transformer. The photovoltaic power generation unit, the wind power generation unit, and the energy storage unit together constitute a new energy AC microgrid. The power load is connected to the AC busbar via a step-down transformer. The thermal power generation unit includes a thermal power generation unit, a fourth step-up transformer, and a third grid-connected switch. The thermal power generation unit is sequentially connected to the AC busbar via the fourth step-up transformer and the third grid-connected switch K3. Furthermore, to enable the thermal power generation unit to start, auxiliary equipment such as a starting oil system and a water supply system are required. These auxiliary equipment are connected to the AC grid via the starting standby transformer and the fourth grid-connected switch K4.

[0038] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A voltage control circuit for a variable slope energy storage commutation device, characterized in that: The voltage control circuit includes a variable slope energy storage commutation circuit, which is used to suppress the inrush current during the black start voltage building process; The variable slope energy storage commutation circuit includes an equivalent capacitor circuit, a first current conversion circuit, a boost circuit, a first filter circuit, a second current conversion circuit and a second filter circuit, wherein the boost circuit includes a low-voltage side and a high-voltage side, the equivalent capacitor circuit and the first current conversion circuit are located on the low-voltage side of the boost circuit, and the first filter circuit, the second current conversion circuit and the second filter circuit are located on the high-voltage side of the boost circuit; the equivalent capacitor circuit, the first current conversion circuit and the low-voltage side of the boost circuit are connected in series to form a first circuit loop, and the first filter circuit, the second current conversion circuit, the second filter circuit and the high-voltage side of the boost circuit form a second current loop.

2. The voltage control circuit according to claim 1, wherein: The voltage control circuit also includes a droop control compensation circuit, which includes at least one group of unit compensation circuits, which are connected in parallel to the equivalent capacitor circuit, and the unit compensation circuits are used to convert direct current into alternating current with controllable output.

3. The voltage control circuit according to claim 2, wherein: The voltage control circuit further includes an equivalent capacitance device, which includes a first capacitor and a first resistor connected in parallel, and the droop control compensation circuit is connected in parallel to both ends of the first resistor.

4. The voltage control circuit according to claim 3, wherein: The unit compensation circuit includes an energy storage power supply, a first inductor, a first MOS transistor, a second MOS transistor and a second capacitor, wherein the positive electrode of the energy storage power supply is connected in series with the first inductor and the emitter of the first MOS transistor in sequence, the collector of the first MOS transistor is connected in parallel to one end of the first resistor in the equivalent capacitor circuit; the negative electrode of the energy storage power supply is connected in parallel to the other end of the first resistor in the equivalent capacitor circuit; one end of the second capacitor is connected in parallel to the collector of the first MOS transistor, and the other end is connected in parallel to the negative electrode of the energy storage power supply; the collector of the second MOS transistor is connected in parallel to the emitter of the first MOS transistor, and the emitter of the second MOS transistor is connected in parallel to the negative electrode of the energy storage power supply.

5. The voltage control circuit according to claim 1, wherein: The first current conversion circuit uses four groups of third MOS transistors, and the four groups of third MOS transistors form a full-bridge inverter circuit. The midpoints of the two bridge arms in the full-bridge inverter circuit are respectively provided with first connection points, and the first connection points of the two bridge arms are respectively connected to the low-voltage side of the boost circuit.

6. The voltage control circuit according to claim 1, wherein: The first filter circuit uses a third capacitor and a second inductor connected in series, and the first filter circuit is used to suppress the inrush current in the circuit.

7. The voltage control circuit according to claim 1, wherein: The second current conversion circuit includes three columns of triode units arranged in parallel, each column of triode units includes two triode sub-units connected in series, and each triode unit is provided with two fourth MOS triodes connected in anti-series; wherein a second connection point is provided between the two triode sub-units in each column of triode units, and each second connection point is connected to a power transmission line.

8. The voltage control circuit according to claim 7, wherein: The second filtering circuit includes three groups of fourth capacitors and three groups of third inductors, wherein each transmission line is connected in series with a third inductor, one end of each fourth capacitor is connected in parallel with a second connection point, and the other ends of the three groups of fourth capacitors are connected in parallel with each other.

9. A variable slope energy storage commutation device, characterized in that: The device is provided with a voltage control circuit as described in any one of claims 1-8.

10. A wind, solar, thermal and energy storage combined device, characterized in that: It comprises an AC bus, and a photovoltaic power generation unit, a wind power generation unit, a thermal power generation unit and an energy storage unit connected in parallel to the AC bus, wherein the energy storage unit is provided with the variable slope energy storage commutation device as claimed in claim 9.

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