A control system and control method for micro-grid energy storage

Abstract

The application discloses a control system and a control method for micro-grid energy storage, and relates to the technical field of micro-grid energy storage. The control system comprises a DC / AC conversion circuit, an LCL filter circuit, a current control circuit, a voltage feedforward circuit and a pulse width modulator. The DC / AC conversion circuit converts an external DC power supply into an AC power supply, and inputs the AC power supply into the LCL filter circuit. The LCL filter circuit filters the AC power supply. The current control circuit is used for current conversion of the filtered AC power supply. The voltage feedforward circuit is used for summing a capacitor voltage and an AC signal in the LCL filter circuit. The pulse width modulator is used for pulse width modulation of the summing result to obtain a modulation signal. The modulation signal is used for control of the DC / AC conversion circuit. The control system of the application can realize safe and stable power supply through real-time circulation.

Description

Technical Field

[0001] This invention relates to the field of microgrid energy storage technology, specifically to a control system and control method for microgrid energy storage. Background Technology

[0002] A microgrid is a miniature power distribution network that integrates power generation and consumption. In recent years, microgrid technology has matured and demonstrated its unique advantages. Microgrids utilize local power generation and consumption, which not only reduces losses during power transmission and distribution, thus improving energy efficiency, but also reduces user dependence on the power grid, enhancing the reliability and security of electricity use. Considering the geographical environment of railway traction substations and leveraging the abundant wind and solar resources along railway lines, applying the aforementioned wind-solar-storage complementary power supply system to the self-consumption system of railway traction substations and using it as the main power source will have significant technical advantages and generate substantial economic benefits. In railway traction substations, excess electricity from photovoltaic, wind, or lithium batteries is transmitted to the AC grid via the DC bus through switches and grid-connected DC / AC converter circuits, thereby maximizing the utilization rate of new energy sources.

[0003] While applying microgrids to railway traction substations offers advantages such as reducing power transmission and distribution losses and improving energy efficiency, the nonlinear and impulsive nature of the loads in these substations generates significant current harmonics. These harmonics flow into the step-down transformers of the local substation, causing voltage distortion in the substation's grid. Secondly, because the grid connection point of the grid-connected DC / AC converter is located at the end of the power supply system, factors such as line impedance and transformer leakage inductance make the connection port inductive, further affecting the grid voltage quality. Therefore, high power quality control of grid-connected DC / AC converters in non-ideal grids rich in background harmonics is one of the challenges in controlling wind-solar-storage complementary power supply systems.

[0004] To overcome the operational safety challenges of microgrid systems caused by the volatility and randomness of distributed energy sources such as wind and solar power, existing technologies often employ energy storage technologies based on lithium batteries, superconducting energy storage, and supercapacitors to compensate for the randomness and volatility of new energy generation in microgrid systems, thereby achieving safe and stable power supply from large-scale wind and solar power. However, these technologies are still imperfect. They may have problems such as incomplete suppression of grid-side nth voltage harmonics; inability to decouple; inability to suppress filter resonance peaks; or excessive computational load, poor robustness, and complex implementation. Therefore, it is evident that existing solutions all have limitations in addressing the energy storage problems of microgrids. Summary of the Invention

[0005] To address one or more of the problems mentioned in the background art, the present invention aims to provide a control system and control method for microgrid energy storage.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A control system for energy storage in a microgrid, the control system comprising: a DC / AC conversion circuit, an LCL filter circuit, a current control circuit, a voltage feedforward circuit, and a pulse width modulator;

[0008] The first input terminal of the DC / AC conversion circuit is connected to an external DC power supply, and the output terminal of the DC / AC conversion circuit is connected to the input terminal of the LCL filter circuit. The DC / AC conversion circuit is used to convert the external DC power supply into AC power supply and input the AC power supply to the LCL filter circuit.

[0009] The first output terminal of the LCL filter circuit is connected to the first input terminal and the second input terminal of the current control circuit, respectively. The LCL filter circuit is used to filter the AC power supply.

[0010] The second output terminal of the LCL filter circuit is connected to the first input terminal of the voltage feedforward circuit, the output terminal of the current control circuit is connected to the second input terminal of the voltage feedforward circuit, and the output terminal of the voltage feedforward circuit is connected to the input terminal of the pulse width modulator. The current control circuit is used to perform current transformation on the filtered AC power supply and output an AC signal. The voltage feedforward circuit is used to sum the capacitor voltage in the LCL filter circuit and the AC signal and output the summation result.

[0011] The output terminal of the pulse width modulator is connected to the second input terminal of the DC / AC conversion circuit. The pulse width modulator is used to perform pulse width modulation on the summation result to obtain a modulated signal, and the modulated signal is input to the DC / AC conversion circuit. The modulated signal is used to control the DC / AC conversion circuit.

[0012] Optionally, the current control circuit includes a fundamental current control circuit, a harmonic current control circuit, and a merging circuit; the input terminal of the fundamental current control circuit is the first input terminal of the current control circuit, the input terminal of the harmonic current control circuit is the second input terminal of the current control circuit, and both the input terminals of the fundamental current control circuit and the harmonic current control circuit are connected to the first output terminal of the LCL filter circuit; the output terminal of the merging circuit is the output terminal of the current control circuit, and the output terminal of the merging circuit is connected to the second input terminal of the voltage feedforward circuit.

[0013] The filtered AC power supply includes fundamental grid-side current and harmonic grid-side current; the fundamental current control circuit is used to perform current transformation on the fundamental grid-side current to obtain a fundamental AC signal; the harmonic current control circuit is used to perform current transformation on the harmonic grid-side current to obtain a harmonic AC signal; and the merging circuit is used to sum the fundamental AC signal and the harmonic AC signal to obtain the AC signal.

[0014] Optionally, the fundamental current control circuit includes a fundamental orthogonal component construction module, a fundamental rotating coordinate transformation module, a fundamental proportional-integral control module, a fundamental decoupling module, and a fundamental inverse rotating coordinate transformation module;

[0015] The input terminal of the fundamental orthogonal component construction module is the input terminal of the fundamental current control circuit. The input terminal of the fundamental orthogonal component construction module is connected to the first output terminal of the LCL filter circuit. The output terminal of the fundamental orthogonal component construction module is connected to the input terminal of the fundamental rotating coordinate transformation module. The fundamental orthogonal component construction module is used to perform orthogonal transformation on the fundamental grid-side current to obtain fundamental orthogonal component pairs.

[0016] The output of the fundamental wave rotating coordinate transformation module is connected to the input of the fundamental wave proportional-integral control module and the first input of the fundamental wave decoupling module, respectively. The fundamental wave rotating coordinate transformation module is used to perform rotating coordinate transformation on the fundamental wave orthogonal component pair to obtain the fundamental wave DC component pair.

[0017] The output terminal of the fundamental frequency proportional-integral control module is connected to the second input terminal of the fundamental frequency decoupling module. The fundamental frequency proportional-integral control module is used to perform proportional-integral calculation on the deviation between the fundamental frequency DC component pair and the preset fundamental frequency DC component pair to obtain the fundamental frequency deviation DC signal.

[0018] The output of the fundamental wave decoupling module is connected to the input of the fundamental wave inverse rotation coordinate transformation module. The fundamental wave decoupling module is used to perform decoupling calculation on the fundamental wave DC component pair to obtain the fundamental wave decoupling signal, and to sum the fundamental wave deviation DC signal and the fundamental wave decoupling signal to obtain the fundamental wave DC decoupling signal.

[0019] The output of the fundamental wave inverse rotation coordinate transformation module is connected to the input of the merging circuit. The fundamental wave inverse rotation coordinate transformation module is used to perform inverse rotation coordinate transformation on the fundamental wave DC decoupled signal to obtain the fundamental wave AC signal.

[0020] Optionally, the harmonic current control circuit includes a harmonic quadrature component construction module, a harmonic rotating coordinate transformation module, a harmonic proportional-integral control module, a harmonic decoupling module, and a harmonic inverse rotating coordinate transformation module.

[0021] The input terminal of the harmonic quadrature component construction module is the input terminal of the harmonic current control circuit. The input terminal of the harmonic quadrature component construction module is connected to the first output terminal of the LCL filter circuit. The output terminal of the harmonic quadrature component construction module is connected to the input terminal of the harmonic rotation coordinate transformation module. The harmonic quadrature component construction module is used to perform orthogonal transformation on the harmonic grid-side current to obtain harmonic quadrature component pairs.

[0022] The output terminal of the harmonic rotating coordinate transformation module is connected to the input terminal of the harmonic proportional-integral control module and the first input terminal of the harmonic decoupling module, respectively. The harmonic rotating coordinate transformation module is used to perform rotating coordinate transformation on the harmonic quadrature component pairs to obtain harmonic DC component pairs.

[0023] The output terminal of the harmonic proportional-integral control module is connected to the second input terminal of the harmonic decoupling module. The harmonic proportional-integral control module is used to perform proportional-integral calculation on the deviation between the harmonic DC component pair and the preset harmonic DC component pair to obtain the harmonic deviation DC signal.

[0024] The output of the harmonic decoupling module is connected to the input of the harmonic inverse rotation coordinate transformation module. The harmonic decoupling module is used to perform decoupling calculation on the harmonic DC component pairs to obtain the harmonic decoupling signal, and to sum the harmonic deviation DC signal and the harmonic decoupling signal to obtain the harmonic DC decoupling signal.

[0025] The output terminal of the harmonic inverse rotation coordinate transformation module is connected to the input terminal of the merging circuit. The harmonic inverse rotation coordinate transformation module is used to perform inverse rotation coordinate transformation on the harmonic DC decoupled signal to obtain the harmonic AC signal.

[0026] Optionally, the voltage feedforward circuit includes a summation module and a gain module;

[0027] The input terminal of the gain module is the first input terminal of the voltage feedforward circuit. The input terminal of the gain module is connected to the second output terminal of the LCL filter circuit. The output terminal of the gain module is connected to the first input terminal of the summation module. The gain module is used to increase the capacitor voltage.

[0028] The second input terminal of the summation module is the second input terminal of the voltage feedforward circuit, and the second input terminal of the summation module is connected to the output terminal of the merging circuit; the output terminal of the summation module is the output terminal of the voltage feedforward circuit, and the output terminal of the summation module is connected to the input terminal of the pulse width modulator; the summation module is used to sum the amplified capacitor voltage and the AC signal, and output the summation result to the pulse width modulator.

[0029] Optionally, the LCL filter circuit includes a capacitor, a first inductor, and a second inductor; one end of the first inductor is connected to the output terminal of the DC / AC conversion circuit, and the other end of the first inductor is connected to one end of the capacitor and one end of the second inductor, respectively; the other end of the capacitor is connected to the output terminal of the DC / AC conversion circuit, the other end of the second inductor, the input terminal of the fundamental current control circuit, and the input terminal of the harmonic current control circuit, respectively; one end of the capacitor and the other end of the capacitor are both connected to the input terminal of the gain module.

[0030] A control method for energy storage in a microgrid, the control method comprising:

[0031] DC / AC conversion circuits convert external DC power into AC power.

[0032] The LCL filter circuit filters the AC power supply;

[0033] The current control circuit performs current conversion on the filtered AC power supply and outputs an AC signal;

[0034] The voltage feedforward circuit sums the capacitor voltage in the LCL filter circuit and the AC signal, and outputs the summation result.

[0035] A pulse width modulator modulates the summation result to obtain a modulated signal, which controls the DC / AC conversion circuit.

[0036] Optionally, the current control circuit performs current transformation on the filtered AC power supply and outputs an AC signal, specifically including:

[0037] The filtered AC power supply includes the fundamental frequency grid side current and the harmonic frequency grid side current.

[0038] The fundamental current control circuit performs current transformation on the fundamental grid-side current to obtain a fundamental AC signal;

[0039] The harmonic current control circuit performs current transformation on the harmonic grid-side current to obtain a harmonic AC signal;

[0040] The merging circuit sums the fundamental AC signal and the harmonic AC signal to obtain the AC signal.

[0041] Optionally, the fundamental current control circuit performs current transformation on the fundamental grid-side current to obtain a fundamental AC signal, specifically including:

[0042] The fundamental orthogonal component construction module performs orthogonal transformation on the fundamental network-side current to obtain fundamental orthogonal component pairs.

[0043] The fundamental wave rotation coordinate transformation module performs rotation coordinate transformation on the fundamental wave orthogonal component pairs to obtain the fundamental wave DC component pairs;

[0044] The fundamental frequency proportional-integral control module performs proportional-integral calculation on the deviation between the fundamental frequency DC component pair and the preset fundamental frequency DC component pair to obtain the fundamental frequency deviation DC signal.

[0045] The fundamental wave decoupling module performs decoupling calculations on the fundamental wave DC component pairs to obtain the fundamental wave decoupling signal, and sums the fundamental wave deviation DC signal and the fundamental wave decoupling signal to obtain the fundamental wave DC decoupling signal;

[0046] The fundamental wave inverse rotation coordinate transformation module performs an inverse rotation coordinate transformation on the fundamental wave DC decoupled signal to obtain the fundamental wave AC signal.

[0047] Optionally, the harmonic current control circuit performs current transformation on the harmonic grid-side current to obtain a harmonic AC signal, specifically including:

[0048] The harmonic orthogonal component construction module performs orthogonal transformation on the harmonic grid-side current to obtain harmonic orthogonal component pairs.

[0049] The harmonic rotation coordinate transformation module performs rotation coordinate transformation on the harmonic quadrature component pairs to obtain harmonic DC component pairs;

[0050] The harmonic proportional-integral control module performs proportional-integral calculation on the deviation between the harmonic DC component pair and the preset harmonic DC component pair to obtain the harmonic deviation DC signal.

[0051] The harmonic decoupling module performs decoupling calculations on the harmonic DC component pairs to obtain the harmonic decoupling signal, and sums the harmonic deviation DC signal and the harmonic decoupling signal to obtain the harmonic DC decoupling signal.

[0052] The harmonic inverse rotation coordinate transformation module performs an inverse rotation coordinate transformation on the harmonic DC decoupled signal to obtain the harmonic AC signal.

[0053] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0054] The present invention provides a control system and control method for microgrid energy storage. The AC power supply is filtered by an LCL filter circuit, and the current control circuit performs current conversion on the filtered AC power supply to output an AC signal. Finally, a pulse width modulator obtains a modulated signal, which controls the DC / AC conversion circuit. The real-time cyclic control system realizes safe and stable power supply. Attached Figure Description

[0055] Figure 1This is a schematic diagram of the control system for microgrid energy storage provided in Embodiment 1 of the present invention;

[0056] Figure 2 This is a schematic diagram of the current control circuit provided in Embodiment 1 of the present invention;

[0057] Figure 3 This is a circuit connection diagram of the control system for microgrid energy storage provided in Embodiment 1 of the present invention;

[0058] Figure 4 This is a circuit connection diagram of the fundamental orthogonal component construction module provided in Embodiment 1 of the present invention;

[0059] Figure 5 This is a flowchart illustrating the control method for microgrid energy storage provided in Embodiment 2 of the present invention.

[0060] Symbol explanation: DC / AC conversion circuit-1, LCL filter circuit-2, current control circuit-3, fundamental current control circuit-31, harmonic current control circuit-32, merging circuit-33, voltage feedforward circuit-4, summing module-41, gain module-42, pulse width modulator-5. Detailed Implementation

[0061] The present invention will be further described below with reference to the accompanying drawings:

[0062] Example 1, as Figure 1 As shown, Embodiment 1 of the present invention provides a control system for microgrid energy storage, including a DC / AC conversion circuit 1, an LCL filter circuit 2, a current control circuit 3, a voltage feedforward circuit 4, and a pulse width modulator 5.

[0063] The first input terminal of the DC / AC converter circuit 1 is connected to an external DC power supply, and the output terminal of the DC / AC converter circuit 1 is connected to the input terminal of the LCL filter circuit 2. The DC / AC converter circuit 1 is used to convert the external DC power supply into AC power supply and input the AC power supply to the LCL filter circuit 2.

[0064] The first output terminal of the LCL filter circuit 2 is connected to the first input terminal and the second input terminal of the current control circuit 3, respectively. The LCL filter circuit 2 is used to filter the AC power supply.

[0065] The second output terminal of the LCL filter circuit 2 is connected to the first input terminal of the voltage feedforward circuit 4, the output terminal of the current control circuit 3 is connected to the second input terminal of the voltage feedforward circuit 4, and the output terminal of the voltage feedforward circuit 4 is connected to the input terminal of the pulse width modulator 5. The current control circuit 3 is used to perform current transformation on the filtered AC power supply and output an AC signal. The voltage feedforward circuit 4 is used to sum the capacitor voltage and the AC signal in the LCL filter circuit 2 and output the summation result.

[0066] The output of the pulse width modulator 5 is connected to the second input of the DC / AC converter circuit 1. The pulse width modulator 5 is used to perform pulse width modulation on the summation result to obtain a modulated signal, and input the modulated signal to the DC / AC converter circuit 1. The modulated signal is used to control the DC / AC converter circuit 1.

[0067] Furthermore, such as Figure 1 As shown, the current control circuit 3 includes a fundamental current control circuit 31, a harmonic current control circuit 32, and a merging circuit 33. The input terminal of the fundamental current control circuit 31 is the first input terminal of the current control circuit 3, and the input terminal of the harmonic current control circuit 32 is the second input terminal of the current control circuit 3. Both the input terminals of the fundamental current control circuit 31 and the harmonic current control circuit 32 are connected to the first output terminal of the LCL filter circuit 2. The output terminal of the merging circuit 33 is the output terminal of the current control circuit 3, and the output terminal of the merging circuit 33 is connected to the second input terminal of the voltage feedforward circuit 4.

[0068] The filtered AC power supply includes the fundamental frequency grid-side current and the harmonic frequency grid-side current; the fundamental frequency current control circuit 31 is used to perform current transformation on the fundamental frequency grid-side current to obtain the fundamental frequency AC signal, the harmonic frequency current control circuit 32 is used to perform current transformation on the harmonic frequency grid-side current to obtain the harmonic AC signal, and the merging circuit 33 is used to sum the fundamental frequency AC signal and the harmonic AC signal to obtain the AC signal.

[0069] Furthermore, such as Figure 2 As shown, the fundamental current control circuit 31 includes a fundamental orthogonal component construction module 311, a fundamental rotating coordinate transformation module 312, a fundamental proportional-integral control module 313, a fundamental decoupling module 314, and a fundamental inverse rotating coordinate transformation module 315.

[0070] The input terminal of the fundamental orthogonal component construction module 311 is the input terminal of the fundamental current control circuit 31. The input terminal of the fundamental orthogonal component construction module 311 is connected to the first output terminal of the LCL filter circuit 2. The output terminal of the fundamental orthogonal component construction module 311 is connected to the input terminal of the fundamental rotation coordinate transformation module 312. The fundamental orthogonal component construction module 311 is used to perform orthogonal transformation on the fundamental grid-side current to obtain fundamental orthogonal component pairs.

[0071] The output of the fundamental wave rotating coordinate transformation module 312 is connected to the input of the fundamental wave proportional-integral control module 313 and the first input of the fundamental wave decoupling module 314, respectively. The fundamental wave rotating coordinate transformation module 312 is used to perform rotating coordinate transformation on the fundamental wave orthogonal component pairs to obtain the fundamental wave DC component pairs.

[0072] The output of the fundamental frequency proportional-integral control module 313 is connected to the second input of the fundamental frequency decoupling module 314. The fundamental frequency proportional-integral control module 313 is used to perform proportional-integral calculation on the deviation between the fundamental frequency DC component pair and the preset fundamental frequency DC component pair to obtain the fundamental frequency deviation DC signal.

[0073] The output of the fundamental wave decoupling module 314 is connected to the input of the fundamental wave inverse rotation coordinate transformation module 315. The fundamental wave decoupling module 314 is used to perform decoupling calculation on the fundamental wave DC component pair to obtain the fundamental wave decoupling signal, and to sum the fundamental wave deviation DC signal and the fundamental wave decoupling signal to obtain the fundamental wave DC decoupling signal.

[0074] The output of the fundamental wave inverse rotation coordinate transformation module 315 is connected to the input of the merging circuit 33. The fundamental wave inverse rotation coordinate transformation module 315 is used to perform inverse rotation coordinate transformation on the fundamental wave DC decoupled signal to obtain the fundamental wave AC signal.

[0075] Furthermore, such as Figure 2 As shown, the harmonic current control circuit 32 includes a harmonic orthogonal component construction module 321, a harmonic rotating coordinate transformation module 322, a harmonic proportional-integral control module 323, a harmonic decoupling module 324, and a harmonic inverse rotating coordinate transformation module 325.

[0076] The input terminal of the harmonic quadrature component construction module 321 is the input terminal of the harmonic current control circuit 32. The input terminal of the harmonic quadrature component construction module 321 is connected to the first output terminal of the LCL filter circuit 2. The output terminal of the harmonic quadrature component construction module 321 is connected to the input terminal of the harmonic rotation coordinate transformation module 322. The harmonic quadrature component construction module 321 is used to perform orthogonal transformation on the harmonic grid side current to obtain harmonic quadrature component pairs.

[0077] The output of the harmonic rotating coordinate transformation module 322 is connected to the input of the harmonic proportional-integral control module 323 and the first input of the harmonic decoupling module 324, respectively. The harmonic rotating coordinate transformation module 322 is used to perform rotating coordinate transformation on the harmonic quadrature component pairs to obtain the harmonic DC component pairs.

[0078] The output of the harmonic proportional-integral control module 323 is connected to the second input of the harmonic decoupling module 324. The harmonic proportional-integral control module 323 is used to perform proportional-integral calculation on the deviation between the harmonic DC component pair and the preset harmonic DC component pair to obtain the harmonic deviation DC signal.

[0079] The output of the harmonic decoupling module 324 is connected to the input of the harmonic inverse rotation coordinate transformation module 325. The harmonic decoupling module 324 is used to perform decoupling calculations on the harmonic DC component pairs to obtain the harmonic decoupling signal, and to sum the harmonic deviation DC signal and the harmonic decoupling signal to obtain the harmonic DC decoupling signal.

[0080] The output terminal of the harmonic inverse rotation coordinate transformation module 325 is connected to the input terminal of the merging circuit 33. The harmonic inverse rotation coordinate transformation module 325 is used to perform inverse rotation coordinate transformation on the harmonic DC decoupled signal to obtain the harmonic AC signal.

[0081] Furthermore, such as Figure 1 and Figure 3 As shown, the voltage feedforward circuit 4 includes a summing module 41 and a gain module 42. The input terminal of the gain module 42 is the first input terminal of the voltage feedforward circuit 4, and its input terminal is connected to the second output terminal of the LCL filter circuit 2. The output terminal of the gain module 42 is connected to the first input terminal of the summing module 41. The gain module 42 is used to amplify the capacitor voltage. The second input terminal of the summing module 41 is the second input terminal of the voltage feedforward circuit 4, and its second input terminal is connected to the output terminal of the merging circuit 33. The output terminal of the summing module 41 is the output terminal of the voltage feedforward circuit 4, and its output terminal is connected to the input terminal of the pulse width modulator 5. The summing module 41 is used to sum the amplified capacitor voltage and the AC signal, and output the summation result to the pulse width modulator 5. The voltage feedforward circuit 4 suppresses the resonance peak of the LCL filter circuit 2. During the operation of the voltage feedforward circuit 4, the capacitor voltage uc in the LCL filter circuit 2 is processed by the feedforward coefficient link H1 (gain module 42) and then combined with the AC signal v output by the current control circuit 3. α The modulation signal v of the single-phase LCL type DC / AC converter circuit 1 is generated by the interaction of the two signals. This modulation signal v is then processed by a sinusoidal pulse width modulation (SPWM) stage to ultimately generate drive signals for the four IGBT devices, thereby controlling the DC / AC converter circuit 1.

[0082] Furthermore, such as Figure 3As shown, the LCL filter circuit 2 includes a capacitor C, a first inductor L1, and a second inductor L2. One end of the first inductor L1 is connected to the output terminal of the DC / AC converter circuit 1, and the other end of the first inductor L1 is connected to one end of the capacitor C and one end of the second inductor L2. The other end of the capacitor C is connected to the output terminal of the DC / AC converter circuit 1, the other end of the second inductor L2, the input terminal of the fundamental current control circuit 31, and the input terminal of the harmonic current control circuit 32. Both ends of the capacitor C and the other end of the capacitor C are connected to the input terminal of the gain module 42. The capacitor C is the filter capacitor, the first inductor L1 is the inverter-side inductor, and the second inductor L2 is the grid-side inductor. The current of the first inductor L1 is i1, the current of the second inductor L2 is i2, and the voltage across the filter capacitor is u. c .

[0083] Furthermore, such as Figure 3 As shown, DC / AC converter circuit 1 consists of DC-side filter capacitor C. dc A single-phase full-bridge inverter consisting of four insulated-gate bipolar transistors (IGBTs) has an output voltage of u. ab The IGBT is a composite, fully controllable, voltage-driven power semiconductor device composed of a bipolar junction transistor (BJT) and an insulated-gate field-effect transistor (MOSFET). It features high input impedance and low on-state voltage. The IGBT consists of three electrodes: a collector, an emitter, and a gate. Applying a forward gate voltage forms a channel, providing base current to the IGBT and turning it on. Conversely, applying a reverse gate voltage eliminates the channel, cutting off the base current and turning the IGBT off. The LCL filter circuit 2 filters the AC power output from the single-phase full-bridge inverter to remove harmonic components, thereby ensuring the quality of the AC power.

[0084] like Figure 3 As shown, the working process of the current control circuit 3 is as follows: The grid-side current i2 is first operated by the fundamental orthogonal component construction module 311 to obtain a pair of fundamental orthogonal components. The pair of fundamental orthogonal components includes the first fundamental orthogonal component i2. α1 The second fundamental orthogonal component i β1 The first fundamental orthogonal component i α1 The second fundamental orthogonal component i β1 After processing by the fundamental frequency rotation coordinate transformation module 312, a pair of fundamental frequency DC components is output, which includes the first fundamental frequency DC component i. d1 Second fundamental DC component i q1 During the rotation transformation, the rotation angle is ωt, and the fundamental angular frequency of the power grid output by the phase-locked loop (PLL) is ω. Next, the first fundamental DC component i... d1As the feedback signal of the grid-side fundamental DC d-axis component control loop and the external first command signal The difference between the first preset fundamental DC component and the preset fundamental DC component is calculated, and the result is sent to the first fundamental proportional-integral controller G1 to eliminate the tracking error in the current control circuit 3; similarly, the second fundamental DC component i is... q1 As the feedback signal of the grid-side fundamental DC d-axis component control loop and the external second command signal The difference between the second preset fundamental DC component in the preset fundamental DC component pair is calculated, and the result of the difference is sent to the second fundamental proportional-integral controller G2.

[0085] Specifically, to achieve decoupling control of the fundamental current dq component on the fundamental control loop network side, this invention introduces a decoupling element, namely a fundamental decoupling module 314, which is arranged between the fundamental rotating coordinate transformation module 312 and the fundamental inverse rotating coordinate transformation module 315. This module performs decoupling operations on the fundamental DC component output from the fundamental rotating coordinate transformation module 312 and sums the decoupling result with the fundamental deviation DC signal output from the fundamental proportional-integral control module 313. In one application scenario, the fundamental decoupling module 314 includes a first decoupler 255 and a second decoupler 256. Firstly, it decouples the first fundamental DC component i... d1 The signal is fed into the first decoupler 255 for processing. The transfer function of the first decoupler is ω(L1+L2). Then, the decoupled signal is summed with the output signal of the second fundamental proportional-integral controller G2 to form v. d1 Components; similarly, the second fundamental DC component i q1 The signal is fed into the second decoupler 256, whose transfer function is -ω(L1+L2). The decoupled signal is then summed with the output signal of the first fundamental proportional-integral controller G1 to form v. q1 Components. After the above processing, v is then... d1 Components and v q1 Component (v) d1 Components and v q1 The fundamental frequency AC signal (the component being the fundamental frequency DC decoupling signal) is fed into the fundamental frequency inverse rotation coordinate transformation module 315 to form a fundamental frequency AC signal. The fundamental frequency AC signal includes the first fundamental frequency AC quadrature component v. α1 The second fundamental wave AC orthogonal component v β1 The rotation angle of the fundamental wave inverse rotation coordinate transformation module 315 is ωt.

[0086] In some application scenarios, the signal output from the LCL filter circuit 2 still contains Nth harmonics. To achieve high power quality control of the grid-side current under conditions rich in background grid voltage harmonics, this invention introduces a harmonic current control circuit 32. The harmonic current control circuit 32 extracts harmonics from the output signal of the LCL filter circuit 2. For details on the working principle and decoupling process of the harmonic current control circuit 32, please refer to the aforementioned working principle and decoupling process of the fundamental current control circuit 31, which will not be repeated here. It should be noted that, in order to suppress grid-side current harmonics, the command value of the harmonic current control circuit 32 can be adjusted. and Set to 0. Further, the first fundamental AC quadrature component v generated by the aforementioned fundamental current control circuit 31 is... α1 The component v generated by the harmonic current control circuit 32 αn This process, combined with the output of an AC signal v, allows for the creation of a signal. α and with AC signal v α This serves as the final output signal of the current control circuit 3. Where N = 3, 5, 7…(2n-1), where n is a constant, and the value of N can be selected based on the harmonic content of each voltage on the grid side.

[0087] like Figure 4 As shown, the workflow of the fundamental orthogonal component construction module 311 specifically includes: sending the grid-side current i2 and the grid fundamental angular frequency ω into the first orthogonal component construction stage to form the first orthogonal component pair i 2α and i 2β In this process, the Generalized Second Integral (SOGI) algorithm is used to construct orthogonal components. Although the SOGI algorithm has low-pass filtering characteristics, it cannot completely filter out harmonic components in the AC power supply. Therefore, in the next step of constructing the first orthogonal component, component i is... 2α The fundamental angular frequency ω of the power grid is fed into the second orthogonal component construction stage to form the second orthogonal component pair i' 2α and qi' 2α At the same time, component i 2β The fundamental angular frequency ω of the power grid is fed into the third orthogonal component construction stage to form the third orthogonal component pair i' 2β and qi' 2β Next, the component i' 2α and qi' 2β Perform a difference operation and divide the result by 2 to obtain the first fundamental quadrature component i. α1 At the same time, the component qi' 2α and i' 2β Perform a summation operation and divide the result by 2 to obtain the second fundamental orthogonal component i. β1 .

[0088] Example 2: In view of the control system for microgrid energy storage provided in Example 1, Example 2 of the present invention provides a control method for microgrid energy storage.

[0089] like Figure 5 As shown, the control methods include:

[0090] Step 101: DC / AC conversion circuit 1 converts the external DC power supply into AC power supply.

[0091] Step 102: LCL filter circuit 2 filters the AC power supply.

[0092] Step 103: The current control circuit 3 performs current conversion on the filtered AC power supply and outputs an AC signal.

[0093] Step 104: The voltage feedforward circuit 4 sums the capacitor voltage and AC signal in the LCL filter circuit 2 and outputs the summation result.

[0094] Step 105: Pulse width modulator 5 performs pulse width modulation on the summation result to obtain a modulated signal, which controls the DC / AC conversion circuit 1.

[0095] Further, step 103 specifically includes:

[0096] Step 1031: The filtered AC power supply includes the fundamental frequency grid side current and the harmonic frequency grid side current; the fundamental frequency current control circuit 31 performs current transformation on the fundamental frequency grid side current to obtain the fundamental frequency AC signal.

[0097] Step 1032: The harmonic current control circuit 32 performs current transformation on the harmonic grid side current to obtain the harmonic AC signal.

[0098] Step 1033: The merging circuit 33 sums the fundamental AC signal and the harmonic AC signal to obtain the AC signal.

[0099] Further, step 1031 specifically includes:

[0100] Step 10311: The fundamental orthogonal component construction module 311 performs orthogonal transformation on the fundamental network-side current to obtain fundamental orthogonal component pairs.

[0101] Step 10312: The fundamental wave rotation coordinate transformation module 312 performs rotation coordinate transformation on the fundamental wave orthogonal component pair to obtain the fundamental wave DC component pair.

[0102] Step 10313: The fundamental frequency proportional-integral control module 313 performs proportional-integral calculation on the deviation between the fundamental frequency DC component pair and the preset fundamental frequency DC component pair to obtain the fundamental frequency deviation DC signal.

[0103] Step 10314: The fundamental wave decoupling module 314 performs decoupling calculations on the fundamental wave DC component pairs to obtain the fundamental wave decoupling signal, and sums the fundamental wave deviation DC signal and the fundamental wave decoupling signal to obtain the fundamental wave DC decoupling signal.

[0104] Step 10315: The fundamental wave inverse rotation coordinate transformation module 315 performs an inverse rotation coordinate transformation on the fundamental wave DC decoupled signal to obtain the fundamental wave AC signal.

[0105] Further, step 1032 specifically includes:

[0106] Step 10321: Harmonic orthogonal component construction module 321 performs orthogonal transformation on the harmonic grid-side current to obtain harmonic orthogonal component pairs.

[0107] Step 10322: The harmonic rotation coordinate transformation module 322 performs rotation coordinate transformation on the harmonic orthogonal component pairs to obtain the harmonic DC component pairs.

[0108] Step 10323: The harmonic proportional-integral control module 323 performs proportional-integral calculation on the deviation between the harmonic DC component pair and the preset harmonic DC component pair to obtain the harmonic deviation DC signal.

[0109] Step 10324: The harmonic decoupling module 324 performs decoupling calculations on the harmonic DC component pairs to obtain the harmonic decoupling signal, and sums the harmonic deviation DC signal and the harmonic decoupling signal to obtain the harmonic DC decoupling signal.

[0110] Step 10325: The harmonic inverse rotation coordinate transformation module 325 performs an inverse rotation coordinate transformation on the harmonic DC decoupled signal to obtain the harmonic AC signal.

[0111] The present invention provides a control system and control method for microgrid energy storage. Through cyclic control, it can completely suppress the Nth voltage harmonic on the grid side and completely suppress the resonant peak of the filter. It has low computational complexity, is easy to implement, and has good robustness.

[0112] Based on the above description, it is understood that the present invention has only described the composition structure and working principle of the energy management system for illustrative and concise purposes. However, depending on different application scenarios, the energy management system may additionally include other structures and units.

[0113] It should be understood that when the terms "first," "second," "third," and "fourth," etc., are used in the claims, specification, and drawings of this invention, they are only used to distinguish different objects and not to describe a specific order. The terms "comprising" and "including" used in the specification and claims of this invention indicate the presence of the described features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof.

[0114] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0115] This embodiment is merely an illustration of the concept and implementation of the present invention and is not intended to limit it. Under the concept of the present invention, technical solutions without substantial changes are still within the scope of protection.

Claims

1. A control system for energy storage in microgrids, characterized in that, The control system includes: a DC / AC conversion circuit, an LCL filter circuit, a current control circuit, a voltage feedforward circuit, and a pulse width modulator; The first input terminal of the DC / AC conversion circuit is connected to an external DC power supply, and the output terminal of the DC / AC conversion circuit is connected to the input terminal of the LCL filter circuit. The DC / AC conversion circuit is used to convert the external DC power supply into AC power supply and input the AC power supply to the LCL filter circuit. The first output terminal of the LCL filter circuit is connected to the first input terminal and the second input terminal of the current control circuit, respectively. The LCL filter circuit is used to filter the AC power supply. The second output terminal of the LCL filter circuit is connected to the first input terminal of the voltage feedforward circuit, the output terminal of the current control circuit is connected to the second input terminal of the voltage feedforward circuit, and the output terminal of the voltage feedforward circuit is connected to the input terminal of the pulse width modulator. The current control circuit is used to perform current transformation on the filtered AC power supply and output an AC signal. The voltage feedforward circuit is used to sum the capacitor voltage in the LCL filter circuit and the AC signal and output the summation result. The current control circuit includes a fundamental current control circuit, a harmonic current control circuit, and a merging circuit. The input terminal of the fundamental current control circuit is the first input terminal of the current control circuit, and the input terminal of the harmonic current control circuit is the second input terminal of the current control circuit. Both the input terminals of the fundamental current control circuit and the harmonic current control circuit are connected to the first output terminal of the LCL filter circuit. The output terminal of the merging circuit is the output terminal of the current control circuit, and the output terminal of the merging circuit is connected to the second input terminal of the voltage feedforward circuit. The filtered AC power supply includes fundamental grid-side current and harmonic grid-side current; the fundamental current control circuit is used to perform current transformation on the fundamental grid-side current to obtain a fundamental AC signal; the harmonic current control circuit is used to perform current transformation on the harmonic grid-side current to obtain a harmonic AC signal; and the merging circuit is used to sum the fundamental AC signal and the harmonic AC signal to obtain the AC signal. The output terminal of the pulse width modulator is connected to the second input terminal of the DC / AC conversion circuit. The pulse width modulator is used to perform pulse width modulation on the summation result to obtain a modulated signal, and the modulated signal is input to the DC / AC conversion circuit. The modulated signal is used to control the DC / AC conversion circuit.

2. The control system for microgrid energy storage according to claim 1, characterized in that, The fundamental current control circuit includes a fundamental orthogonal component construction module, a fundamental rotating coordinate transformation module, a fundamental proportional-integral control module, a fundamental decoupling module, and a fundamental inverse rotating coordinate transformation module. The input terminal of the fundamental orthogonal component construction module is the input terminal of the fundamental current control circuit. The input terminal of the fundamental orthogonal component construction module is connected to the first output terminal of the LCL filter circuit. The output terminal of the fundamental orthogonal component construction module is connected to the input terminal of the fundamental rotating coordinate transformation module. The fundamental orthogonal component construction module is used to perform orthogonal transformation on the fundamental grid-side current to obtain fundamental orthogonal component pairs. The output of the fundamental wave rotating coordinate transformation module is connected to the input of the fundamental wave proportional-integral control module and the first input of the fundamental wave decoupling module, respectively. The fundamental wave rotating coordinate transformation module is used to perform rotating coordinate transformation on the fundamental wave orthogonal component pair to obtain the fundamental wave DC component pair. The output terminal of the fundamental frequency proportional-integral control module is connected to the second input terminal of the fundamental frequency decoupling module. The fundamental frequency proportional-integral control module is used to perform proportional-integral calculation on the deviation between the fundamental frequency DC component pair and the preset fundamental frequency DC component pair to obtain the fundamental frequency deviation DC signal. The output of the fundamental wave decoupling module is connected to the input of the fundamental wave inverse rotation coordinate transformation module. The fundamental wave decoupling module is used to perform decoupling calculation on the fundamental wave DC component pair to obtain the fundamental wave decoupling signal, and to sum the fundamental wave deviation DC signal and the fundamental wave decoupling signal to obtain the fundamental wave DC decoupling signal. The output of the fundamental wave inverse rotation coordinate transformation module is connected to the input of the merging circuit. The fundamental wave inverse rotation coordinate transformation module is used to perform inverse rotation coordinate transformation on the fundamental wave DC decoupled signal to obtain the fundamental wave AC signal.

3. The control system for microgrid energy storage according to claim 1, characterized in that, The harmonic current control circuit includes a harmonic quadrature component construction module, a harmonic rotation coordinate transformation module, a harmonic proportional-integral control module, a harmonic decoupling module, and a harmonic inverse rotation coordinate transformation module. The input terminal of the harmonic quadrature component construction module is the input terminal of the harmonic current control circuit. The input terminal of the harmonic quadrature component construction module is connected to the first output terminal of the LCL filter circuit. The output terminal of the harmonic quadrature component construction module is connected to the input terminal of the harmonic rotation coordinate transformation module. The harmonic quadrature component construction module is used to perform orthogonal transformation on the harmonic grid-side current to obtain harmonic quadrature component pairs. The output terminal of the harmonic rotating coordinate transformation module is connected to the input terminal of the harmonic proportional-integral control module and the first input terminal of the harmonic decoupling module, respectively. The harmonic rotating coordinate transformation module is used to perform rotating coordinate transformation on the harmonic quadrature component pairs to obtain harmonic DC component pairs. The output terminal of the harmonic proportional-integral control module is connected to the second input terminal of the harmonic decoupling module. The harmonic proportional-integral control module is used to perform proportional-integral calculation on the deviation between the harmonic DC component pair and the preset harmonic DC component pair to obtain the harmonic deviation DC signal. The output of the harmonic decoupling module is connected to the input of the harmonic inverse rotation coordinate transformation module. The harmonic decoupling module is used to perform decoupling calculation on the harmonic DC component pairs to obtain the harmonic decoupling signal, and to sum the harmonic deviation DC signal and the harmonic decoupling signal to obtain the harmonic DC decoupling signal. The output terminal of the harmonic inverse rotation coordinate transformation module is connected to the input terminal of the merging circuit. The harmonic inverse rotation coordinate transformation module is used to perform inverse rotation coordinate transformation on the harmonic DC decoupled signal to obtain the harmonic AC signal.

4. The control system for microgrid energy storage according to claim 1, characterized in that, The voltage feedforward circuit includes a summation module and a gain module; The input terminal of the gain module is the first input terminal of the voltage feedforward circuit. The input terminal of the gain module is connected to the second output terminal of the LCL filter circuit. The output terminal of the gain module is connected to the first input terminal of the summation module. The gain module is used to increase the capacitor voltage. The second input terminal of the summing module is the second input terminal of the voltage feedforward circuit, and the second input terminal of the summing module is connected to the output terminal of the merging circuit; the output terminal of the summing module is the output terminal of the voltage feedforward circuit, and the output terminal of the summing module is connected to the input terminal of the pulse width modulator. The summation module is used to sum the gained capacitor voltage and the AC signal, and output the summation result to the pulse width modulator.

5. The control system for microgrid energy storage according to claim 4, characterized in that, The LCL filter circuit includes a capacitor, a first inductor, and a second inductor. One end of the first inductor is connected to the output terminal of the DC / AC conversion circuit, and the other end of the first inductor is connected to one end of the capacitor and one end of the second inductor. The other end of the capacitor is connected to the output terminal of the DC / AC conversion circuit, the other end of the second inductor, the input terminal of the fundamental current control circuit, and the input terminal of the harmonic current control circuit. One end of the capacitor and the other end of the capacitor are both connected to the input terminal of the gain module.

6. A control method for energy storage in microgrids, characterized in that, The control method includes: DC / AC conversion circuits convert external DC power into AC power. The LCL filter circuit filters the AC power supply; The current control circuit performs current transformation on the filtered AC power supply and outputs an AC signal. The filtered AC power supply includes the fundamental grid side current and the harmonic grid side current. The fundamental current control circuit performs current transformation on the fundamental grid-side current to obtain a fundamental AC signal; The harmonic current control circuit performs current transformation on the harmonic grid-side current to obtain a harmonic AC signal; The merging circuit sums the fundamental AC signal and the harmonic AC signal to obtain the AC signal; The voltage feedforward circuit sums the capacitor voltage in the LCL filter circuit and the AC signal, and outputs the summation result. A pulse width modulator modulates the summation result to obtain a modulated signal, which controls the DC / AC conversion circuit.

7. The control method for microgrid energy storage according to claim 6, characterized in that, The fundamental current control circuit performs current transformation on the fundamental grid-side current to obtain a fundamental AC signal, specifically including: The fundamental orthogonal component construction module performs orthogonal transformation on the fundamental network-side current to obtain fundamental orthogonal component pairs. The fundamental wave rotation coordinate transformation module performs rotation coordinate transformation on the fundamental wave orthogonal component pairs to obtain the fundamental wave DC component pairs; The fundamental frequency proportional-integral control module performs proportional-integral calculation on the deviation between the fundamental frequency DC component pair and the preset fundamental frequency DC component pair to obtain the fundamental frequency deviation DC signal. The fundamental wave decoupling module performs decoupling calculations on the fundamental wave DC component pairs to obtain the fundamental wave decoupling signal, and sums the fundamental wave deviation DC signal and the fundamental wave decoupling signal to obtain the fundamental wave DC decoupling signal; The fundamental wave inverse rotation coordinate transformation module performs an inverse rotation coordinate transformation on the fundamental wave DC decoupled signal to obtain the fundamental wave AC signal.

8. The control method for microgrid energy storage according to claim 6, characterized in that, The harmonic current control circuit performs current transformation on the harmonic grid-side current to obtain a harmonic AC signal, specifically including: The harmonic orthogonal component construction module performs orthogonal transformation on the harmonic grid-side current to obtain harmonic orthogonal component pairs. The harmonic rotation coordinate transformation module performs rotation coordinate transformation on the harmonic quadrature component pairs to obtain harmonic DC component pairs; The harmonic proportional-integral control module performs proportional-integral calculation on the deviation between the harmonic DC component pair and the preset harmonic DC component pair to obtain the harmonic deviation DC signal. The harmonic decoupling module performs decoupling calculations on the harmonic DC component pairs to obtain the harmonic decoupling signal, and sums the harmonic deviation DC signal and the harmonic decoupling signal to obtain the harmonic DC decoupling signal. The harmonic inverse rotation coordinate transformation module performs an inverse rotation coordinate transformation on the harmonic DC decoupled signal to obtain the harmonic AC signal.

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