A method, device and medium for constructing a light storage and charging alternating current-direct current hybrid microgrid

Abstract

The present application relates to a kind of light storage fills in and mixes direct current hybrid microgrid network control method, equipment and medium, the method is according to the SOC value of energy storage device and is classified management to energy storage converter.Priority high converter switches to VSG mode, detect whether microgrid voltage and frequency fluctuation exceeds adjustment dead zone.When frequency fluctuation exceeds, active power output is adjusted by VSG mode;When voltage fluctuation exceeds, adjust reactive power output. Energy storage device is switched to VSG mode gradually, when demand cannot be met, photovoltaic equipment and electric vehicle are sequentially put into support grid.Before photovoltaic equipment access, its voltage is consistent with the connected energy storage device, and is converted into VSG mode.If still need further support, then by adjusting charging pile control algorithm, electric vehicle is fed back.Electric vehicle also needs to synchronize voltage and phase before access, to support microgrid.This method significantly improves the voltage and frequency stability of microgrid system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of micro-grid control, in particular to a kind of light storage charge interconnection DC hybrid micro-grid network construction control method, equipment and medium. BACKGROUND

[0002] The light storage charge interconnection DC hybrid micro-grid is composed of photovoltaic units, energy storage units and charging piles, which can fully utilize photovoltaic clean energy and energy storage peak load shifting advantages to build a source-grid-load-storage integrated green low-carbon park coupled with park power load, reduce carbon emissions and improve economic efficiency. The intermittency and volatility of photovoltaic power generation can easily cause instability of micro-grid frequency and voltage. The current micro-grid system mainly uses grid-following (GFL) converters, which are connected to the grid. They cannot actively respond to changes in grid frequency and voltage, lack inertia and damping capacity, so they cannot support and regulate frequency and voltage. Grid-forming (GFM) converters can provide inertia support for micro-grids and have certain active support capacity. However, the existing invention does not comprehensively study the method of supporting micro-grid voltage and frequency. Therefore, how to propose a comprehensive method to establish and maintain bus voltage, and actively support micro-grid voltage and frequency when the light storage charge interconnection DC hybrid micro-grid system voltage and frequency fluctuate, has become a key problem to be solved.

[0003] For the network construction control method of new energy station, Chinese patent number CN118232365A discloses a control method and device for new energy station based on network construction technology. The invention proposes a control method for supporting grid frequency by energy storage, photovoltaic and wind turbine in new energy station during grid connection. According to the regulation coefficient, the energy storage devices in the station are classified. When the grid frequency fluctuation range exceeds the regulation dead zone, the energy storage devices support the grid voltage and frequency step by step, then calculate the gap capacity after energy storage support, and determine the photovoltaic and wind turbine to be put into. The invention mainly studies the new energy station micro-grid in grid-connected operation, and its topology does not consider the AC / DC hybrid micro-grid. When multiple energy storage units are operated in parallel, the State of Charge (SOC) balancing problem between energy storage units is not fully considered, and the amplitude and phase synchronization problem of VSG (Virtual synchronous generator) operating mode converter in parallel operation is not considered. SUMMARY

[0004] The present application provides a light storage charge interconnection DC hybrid micro-grid network construction control method, equipment and medium, which aims to solve the problem of how to dynamically adjust the number of energy storage devices, photovoltaic systems and electric vehicles to stabilize the voltage and frequency of micro-grid, improve the self-adjusting ability of the system and reduce the cost when the micro-grid is in grid-connected to island operation mode.

[0005] To achieve the above objectives, the present invention provides a first aspect of a photovoltaic, storage, charging, AC, and DC hybrid microgrid construction and control method, comprising the following steps:

[0006] The energy storage converters are graded from high to low according to the SOC value of the energy storage device. The working mode of the energy storage converter with the highest priority is switched from PQ mode to VSG mode.

[0007] Obtain the voltage and frequency of the microgrid, and determine whether the voltage and frequency fluctuation range of the microgrid exceeds the regulation dead zone;

[0008] When the frequency fluctuation of the microgrid exceeds the regulation dead zone, the active power compensation required is calculated through the active-frequency control of the VSG mode to adjust the active power output of the microgrid and energy storage equipment;

[0009] When the voltage fluctuation of the microgrid exceeds the regulation dead zone, the reactive power output of the microgrid and energy storage equipment is adjusted through the reactive-voltage control of the VSG mode;

[0010] Detect the SOC value of the energy storage device and adjust the operating mode of the energy storage device step by step from high to low SOC value, switching from PQ mode to VSG mode. Through the synchronization control module, the voltage amplitude and phase angle of the energy storage converter are synchronized with the energy storage converter that has been put into VSG mode. The energy storage device supports the voltage and frequency of the microgrid step by step.

[0011] If all energy storage devices are switched to VSG mode and still cannot respond to voltage and frequency fluctuations of the microgrid, the photovoltaic devices on the AC bus are put into operation in descending order of adjustable capacity;

[0012] Before the photovoltaic equipment is put into operation, the DC / AC converter of the photovoltaic equipment is synchronized with the voltage amplitude and phase angle of the energy storage device that has been put into operation through the synchronization control module;

[0013] Switch the operating mode of the photovoltaic equipment from PQ mode to VSG mode, and jointly support the voltage and frequency of the microgrid with the energy storage unit;

[0014] If the microgrid voltage and frequency fluctuations still cannot be fully responded to, the control algorithm of the charging pile is adjusted to feed the microgrid through electric vehicles to establish the microgrid voltage;

[0015] Before the electric vehicle is put into use, the voltage amplitude and phase of the electric vehicle charging pile are synchronized with the voltage amplitude and phase angle of the energy storage converter that has been put into use through the synchronization control module;

[0016] The electric vehicle battery and energy storage equipment are controlled by the synchronous control module to jointly support the microgrid voltage and frequency with the photovoltaic array.

[0017] Furthermore, the method for grading the energy storage converters from high to low according to the SOC values ​​of the energy storage devices includes:

[0018] Obtain the SOC value of each energy storage device;

[0019] Sort the SOC values ​​of the energy storage devices and set the priority of each energy storage device in responding to microgrid fluctuations according to the SOC value from large to small;

[0020] The power required for regulation is sent to each energy storage device in turn, and power is allocated according to priority and maximum charge and discharge power until the power allocation is completed.

[0021] Furthermore, the method of sequentially sending the required power to each energy storage device and allocating the power according to the priority and the maximum charge and discharge power until the power allocation is completed includes:

[0022] Initialize the power to be allocated in response to frequency and voltage fluctuations in the microgrid;

[0023] The PCS of the energy storage device with the highest priority is traversed from each energy storage device and is taken as the current PCS. If the maximum charge / discharge power value of the current PCS is less than the power to be allocated, the maximum charge / discharge power value of the current PCS is used as the charge / discharge power of the current PCS, and the charge / discharge power of the current PCS is subtracted from the power to be allocated to obtain the new power to be allocated. Otherwise, the power to be allocated is used as the charge / discharge power of the current PCS.

[0024] Determine whether each PCS has been traversed. If not, jump to the previous step. Otherwise, determine that the regulation capacity of the energy storage unit has reached saturation, end and exit.

[0025] Furthermore, the active power-frequency control in VSG mode is based on the rotor characteristics of the synchronous generator. The required active power compensation is calculated through the rotor motion equation. The specific calculation formula is as follows:

[0026]

[0027] Where P is the active power compensation required for the system to reach the target frequency, J is the inertia coefficient of the virtual synchronous generator, ω0 is the rated angular frequency, ω is the output angular frequency of the VSG, is the rate of change of angular frequency, and D is the damping coefficient of the virtual synchronous generator.

[0028] Furthermore, the calculation formula for the active power change of the inertia response in VSG mode is:

[0029]

[0030] Among them, P Inertiais the active power variation of the micro-grid in response to the inertia, T J is the equivalent inertia time constant, f N is the rated frequency of the micro-grid system, is the frequency variation rate of the micro-grid, P N is the rated active power of the grid-forming device.

[0031] The damping active power calculation formula in VSG mode is:

[0032] P Damping = D(ω-ω0)

[0033] wherein, P Damping is the damping active power provided by the virtual synchronous generator, D is the damping coefficient of the virtual synchronous generator, ω0 is the rated angular frequency, and ω is the output angular frequency of the VSG.

[0034] Further, the reactive power-voltage control calculation formula in VSG mode is:

[0035] ΔU = D q (Q ref -Q e )+(U ref -U)

[0036] wherein, ΔU is the voltage variation, D q is the reactive power droop coefficient, Q ref is the reactive power set value, Q e is the converter output reactive power, U ref is the voltage set value, and U is the converter output voltage amplitude.

[0037] Further, the control steps of the synchronization control module are:

[0038] The voltage amplitude and phase of the energy storage device, photovoltaic device or electric vehicle charging pile converter are controlled by the synchronization control module, so that they are equal to the voltage amplitude and phase of the VSG converter that has been put into operation, and the difference between the voltage instantaneous values of the converters operating in VSG mode is ensured to be zero when they are parallelly connected;

[0039] According to the difference between the voltage amplitude and phase, the phase adjustment step and the amplitude adjustment step are adjusted, and the synchronization process is carried out until the voltage amplitude and phase are completely synchronized.

[0040] Further, the control calculation formula of the synchronization control module is:

[0041]

[0042] wherein, Δu is the voltage instantaneous difference between the second converter and the first converter output side, U A_converter1 is the voltage of the first converter output side, and UA_converter2 is the output voltage of the second converter, U1 and U2 are the voltage amplitudes of the two converter outputs, ω1 and ω2 are the angular frequencies of the two converter outputs, and are the initial phase angles on the output sides of the two converters respectively;

[0043] The control formula of the synchronization process is:

[0044]

[0045] By adjusting the phase difference and amplitude difference, the voltage synchronization of the two converters can be gradually achieved.

[0046] To achieve the above objectives, the second aspect of the present invention provides an electronic device, including a processor and a memory, wherein the processor is configured to implement the steps of the photovoltaic storage charging AC / DC hybrid microgrid network control method when executing a computer program stored in the memory.

[0047] To achieve the above-mentioned objectives, the third aspect of the present invention provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the photovoltaic storage charging AC / DC hybrid microgrid network control method are executed.

[0048] Beneficial effects of the present invention:

[0049] Compared with the prior art, the present invention provides a photovoltaic storage and charging AC / DC hybrid microgrid control method, device and medium, which, based on the dynamic coordinated regulation mechanism of energy storage equipment, photovoltaic system and electric vehicles, effectively solves the problem of system instability caused by frequency and voltage fluctuations when the microgrid switches to island mode during grid connection. Specifically, the present invention classifies the energy storage equipment according to its SOC value priority, adjusts the working mode of the energy storage equipment step by step, switches from PQ mode to VSG mode, and supports the voltage and frequency of the microgrid; at the same time, when the energy storage equipment and photovoltaic system cannot fully meet the needs of the power grid, further introduces electric vehicles to feed power to the microgrid through charging piles, forming a multi-level and diversified power regulation mechanism, thereby enhancing the system's adaptability. In addition, the present invention ensures impact-free access when multiple devices are running in parallel through synchronous control technology, reduces dependence on the external power grid, improves the stability and autonomous regulation capability of the microgrid, reduces costs, and can effectively deal with problems such as unstable photovoltaic power generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments.

[0051] Figure 1This is a topology diagram of a photovoltaic storage and charging AC / DC hybrid microgrid system disclosed in an embodiment of the present invention.

[0052] Figure 2 This is a microgrid control flow chart disclosed in an embodiment of the present invention.

[0053] Figure 3 This is a schematic diagram of a microgrid control structure disclosed in an embodiment of the present invention.

[0054] Figure 4 This is a flow chart of energy storage device classification and power distribution disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0055] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0056] Figure 1 This is a PV-storage-charging AC / DC microgrid system topology with two buses: a DC bus and an AC bus. The DC and AC buses are connected via a DC / AC converter operating in PQ mode. The AC bus is connected to the grid via a transformer. This AC / DC hybrid microgrid can switch between grid-connected and islanded modes. When the microgrid is grid-connected, all converters operate in PQ mode, controlling the distribution of active and reactive power. When the microgrid is islanded, at least one converter switches to VSG mode, simulating the behavior of a synchronous generator to provide virtual inertia and damping, thereby maintaining voltage and frequency stability.

[0057] Virtual inertia and damping are important concepts in virtual synchronous generator (VSG) control technology, which are used to simulate the characteristics of traditional rotating generators to enhance the stability of microgrids during frequency and voltage fluctuations.

[0058] As you can understand, traditional synchronous generators provide inertia through their rotating rotors, helping to mitigate frequency fluctuations when the load changes. Virtual inertia simulates this characteristic through the converter, allowing power electronic devices (such as energy storage systems and photovoltaic inverters) to provide a certain inertial response when the system frequency changes, just like a synchronous generator. Specifically, virtual inertia enables microgrids to provide a certain amount of power support when the frequency drops, mimicking the frequency drop and helping the grid to restore stability.

[0059] Damping is the process of mitigating system oscillations by regulating power. Traditional synchronous generators use electromagnetic forces to generate damping, helping the grid quickly stabilize when frequency fluctuations occur. Virtual synchronous generators simulate this damping effect by adjusting their output power (active power), helping to reduce excessive system oscillations and restore the grid to a stable state. Damping typically occurs when the grid frequency deviates from the rated value, providing the necessary power correction to prevent excessive frequency excursions.

[0060] In power systems, traditional synchronous generators regulate reactive power through excitation electromotive force to cope with fluctuations in reactive load and maintain system voltage stability. In virtual synchronous generators, voltage regulation and excitation control together form a reactive-voltage control loop. By obtaining a reference voltage from the synchronous generator's voltage regulation unit, the synchronous generator's voltage droop control characteristic is implemented, ensuring reactive power balance and voltage stability in the power system, providing a stable and high-quality power supply.

[0061] In summary, virtual inertia helps the system cope with frequency fluctuations and provides short-term support, damping reduces frequency oscillations, and the excitation control system actively adjusts reactive power to maintain the stability of the converter terminal voltage, jointly ensuring the stable operation of the microgrid.

[0062] The energy storage module, photovoltaic array, and charging pile are connected to the AC bus via a DC / AC converter with two operating modes: PQ and VSG. Other AC loads with matching voltages are directly connected to the AC bus. The photovoltaic unit is connected to the DC bus via a unidirectional DC / DC converter, providing DC power input. The energy storage module and charging pile are connected to the DC bus via a bidirectional DC / DC converter, which controls the charge and discharge of the energy storage system and the electric vehicle batteries connected to the charging pile. Other DC loads with matching voltages are directly connected to the DC bus. This configuration enables the energy storage device to provide power support when power demand is insufficient. The charging pile can also provide charging services for electric vehicles or support the microgrid through reverse power feeding.

[0063] In addition, the DC subsystem is connected to a photovoltaic power generation unit and a charging pile unit, and the entire DC subsystem can operate independently; similarly, the AC subsystem can also operate independently. According to the distributed power capacity, power supply distance and load characteristics of the entire microgrid system, the AC bus voltage level is designed to be 400V, and the DC bus voltage level is designed to be 750V with reference to various engineering standards, engineering experiments and the voltage level of DC loads. The system power supply and demand balance should be ensured to achieve safe and stable operation of the system. The power balance can be reflected by the bus voltage. When the bus voltage tends to be stable or remains unchanged, the system power will reach balance. Its basic energy relationship is as follows:

[0064] P PV+P BAT +P CAR +P L =0

[0065] Among them, P PV is the discharge power of the photovoltaic unit, P BAT is the charge and discharge power of the energy storage unit. It is negative when the energy storage device is discharging and positive when it is charging. CAR is the charging and discharging power of the charging pile unit. It is negative when the electric vehicle battery is discharging and positive when charging. L Power consumption for other AC and DC loads.

[0066] According to an embodiment of the present invention, it should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the following method, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0067] like Figure 2-Figure 4 As shown, the present invention provides a method for controlling a photovoltaic storage and charging AC / DC hybrid microgrid, comprising the following steps:

[0068] Step S100: classify the energy storage converters from high to low according to the SOC values ​​of the energy storage devices, and switch the working mode of the energy storage converter with the highest priority from the PQ mode to the VSG mode;

[0069] Step S200: obtaining the voltage and frequency of the microgrid, and determining whether the voltage and frequency fluctuation range of the microgrid exceeds the regulation dead zone;

[0070] Step S300: When the frequency fluctuation of the microgrid exceeds the regulation dead zone, the required active power compensation is calculated through the active-frequency control of the VSG mode to adjust the active power output of the microgrid and the energy storage device;

[0071] Step S400: When the voltage fluctuation of the microgrid exceeds the regulation dead zone, the reactive power output of the microgrid and the energy storage device is adjusted through the reactive-voltage control of the VSG mode;

[0072] Step S500: Detect the SOC value of the energy storage device, adjust the operating mode of the energy storage device step by step from high to low SOC values, switch from PQ mode to VSG mode, synchronize the voltage amplitude and phase angle of the energy storage converter with the energy storage converter already operating in VSG mode through the synchronization control module, and the energy storage device supports the microgrid voltage and frequency step by step;

[0073] Step S600: If all energy storage devices are switched to VSG mode and still cannot respond to voltage and frequency fluctuations of the microgrid, the photovoltaic devices on the AC bus are put into operation in descending order of adjustable capacity;

[0074] Step S700: Before the photovoltaic equipment is put into operation, the DC / AC converter of the photovoltaic equipment is synchronized with the voltage amplitude and phase angle of the energy storage device that has been put into operation through the synchronization control module;

[0075] Step S800: Switch the working mode of the photovoltaic device from PQ mode to VSG mode, and jointly support the voltage and frequency of the microgrid with the energy storage unit;

[0076] Step S900: If the microgrid voltage and frequency fluctuations still cannot be fully responded to, the control algorithm of the charging pile is adjusted to feed the microgrid through the electric vehicle to establish the microgrid voltage;

[0077] Step S1000: Before the electric vehicle is put into operation, the voltage amplitude and phase of the electric vehicle charging pile are synchronized with the voltage amplitude and phase angle of the already-in-operation converter through the synchronization control module;

[0078] Step S1100: Control the electric vehicle battery and energy storage device and the photovoltaic array through the synchronous control module to jointly support the microgrid voltage and frequency.

[0079] In this embodiment, as described in steps S100 through S500 (the first processing module), the PCSs are ranked from high to low according to the SOC of the energy storage devices, and the highest-priority PCS switches from PQ to VSG operating mode. The microgrid voltage and frequency are obtained. When the voltage and frequency fluctuations of the microgrid exceed the regulation dead zone due to disturbances or load changes, the active power compensation and reactive power compensation required for the system to achieve the target frequency are determined based on the current microgrid voltage and frequency.

[0080] Active power-frequency control in VSG is based on the rotor characteristics of the synchronous generator. The relationship between active power and frequency is derived from the rotor motion equation. The active power that needs to be compensated is calculated as follows:

[0081]

[0082] Where P is the active power compensation required for the system to reach the target frequency, J is the inertia coefficient of the virtual synchronous generator, ω0 is the rated angular frequency, ω is the output angular frequency of the VSG, is the rate of change of angular frequency, and D is the damping coefficient of the virtual synchronous generator.

[0083] Grid-connected converters can provide virtual inertia and damping, providing voltage and frequency support for microgrids. Virtual synchronous generator (VSG) control technology is a converter control technology that enables power electronic devices such as flexible AC / DC transmission equipment, renewable energy generation, electric vehicles, and energy storage to simulate the rotational inertia and damping characteristics of rotating motors. In inertia response mode, the active power change is:

[0084]

[0085] Among them, P Inertia is the change in active power of the microgrid during inertia response, T J is the equivalent inertia time constant, f N is the rated frequency of the microgrid system, is the frequency change rate of the microgrid, P N It is the rated active power of the network-forming equipment.

[0086] The calculated active power change is distributed to each inverter to adjust the inertia response.

[0087] The damping active power comes from the oscillation between the terminal voltage of the grid-type unit and the internal voltage source voltage. It is the active power provided by the converter independently and can respond in less than 5 milliseconds. The damping active power is used to measure the damping effect that the energy storage system can provide. Its expression is:

[0088] P Damping =D(ω-ω0)

[0089] Among them, P Damping is the damping active power provided by the virtual synchronous generator, D is the damping coefficient of the virtual synchronous generator, ω0 is the rated angular frequency, and ω is the output angular frequency of the VSG.

[0090] Reactive power-voltage control simulates the regulation characteristics by simulating the excitation process of the synchronous machine. The relationship between the converter output reactive power and voltage is as follows:

[0091] ΔU=D q (Q ref -Q e )+(U ref -U)

[0092] Among them, ΔU is the voltage change, D q is the reactive power droop coefficient, Q ref is the reactive power setting value, Q e is the reactive power output of the converter, U ref is the voltage setting value, and U is the output voltage amplitude of the converter.

[0093] The voltage and frequency of the microgrid are supported step by step according to the SOC of the energy storage device, solving the balancing problem of multiple energy storage devices in parallel. The specific work flow is as follows:

[0094] The SOC of the energy storage device is detected. The operating mode of the energy storage converter connected to the energy storage device with the highest SOC is switched from PQ to VSG, establishing the AC bus voltage and supporting the microgrid voltage and frequency. At this time, the other converters are still operating in PQ mode. When the power of the energy storage device is insufficient to support the microgrid voltage and frequency, the operating mode of the energy storage converter connected to the energy storage device is switched from PQ to VSG step by step according to the SOC from high to low, so that the energy storage device can gradually support the microgrid voltage and frequency.

[0095] In this embodiment, as described in steps S600 to S800 above (the second processing module), if all energy storage devices in the microgrid are switched to VSG operation and still cannot fully respond to the frequency fluctuations of the microgrid, then the AC photovoltaic devices are put into operation step by step in order of adjustable capacity from high to low. Before the photovoltaic devices are put into operation, the converter voltage synchronization is completed by the second synchronization control module so that the voltage amplitude and phase angle of the DC / AC converter connected to the photovoltaic device are synchronized with the converter connected to the already put into operation energy storage device. The corresponding DC / AC converter operation mode is switched from PQ to VSG, and the AC bus voltage is jointly established with the energy storage unit to support the voltage and frequency of the microgrid.

[0096] It's understandable that by gradually introducing photovoltaic devices and achieving voltage and phase synchronization, the photovoltaic system can seamlessly work with the energy storage unit to provide additional voltage and frequency support. By switching the photovoltaic converter to VSG mode, simulating the inertia and damping characteristics of a virtual synchronous generator, the microgrid's dynamic regulation capabilities are enhanced, helping the system better cope with frequency fluctuations, reducing dependence on the external grid, and improving the microgrid's autonomous regulation and stability. This mechanism effectively enhances the microgrid's self-sustaining capabilities in island mode, ensuring smooth and reliable system operation.

[0097] In this embodiment, as described in steps S900 to S1100 above (the third processing module), when the photovoltaic array cannot generate electricity or the power generation is insufficient due to darkness or shadows, resulting in all energy storage devices and photovoltaics still unable to respond to microgrid voltage and frequency fluctuations after being put into operation, the control algorithm of the AC bus side charging pile is adjusted, and the electric vehicle is used to feed power to the microgrid through the charging pile to establish the bus voltage of the microgrid. The working mode of the corresponding DC / AC converter is switched from PQ to VSG, and the third synchronization control module is used to synchronize it with the voltage amplitude and phase angle of the converter that has been put into operation, so that the battery and energy storage device of the electric vehicle, together with the photovoltaic array, provide short-term frequency and voltage support for the independent microgrid.

[0098] Figure 4 A flow chart of energy storage device classification and power allocation is provided, such as Figure 4 As shown in Figure 1, the specific steps for grading energy storage devices according to SOC and allocating power to respond to microgrid frequency fluctuations are as follows:

[0099] 1) Obtain the SOC value of each energy storage device;

[0100] 2) Sort the SOC values ​​of the energy storage devices and set the priority of each energy storage device in responding to microgrid fluctuations according to the SOC value from large to small;

[0101] 3) The power required for voltage and frequency regulation is distributed to each energy storage device in sequence according to the priority of each energy storage device and the maximum charge and discharge power of each energy storage device until the power is fully allocated. The specific steps are as follows:

[0102] 3.1) Initialize the power required to respond to frequency and voltage fluctuations in the microgrid, i.e., the power to be allocated;

[0103] 3.2) The PCS of the energy storage device with the highest priority is traversed from each energy storage device and selected as the current PCS. If the maximum charge / discharge power value of the current PCS is less than the power to be allocated, the maximum charge / discharge power value of the current PCS is used as the charge / discharge power of the current PCS, and the charge / discharge power of the current PCS is subtracted from the power to be allocated to obtain the new power to be allocated. Otherwise, the power to be allocated is used as the charge / discharge power of the current PCS.

[0104] 3.3) Determine whether all PCSs have been traversed. If not, jump to step 3.2). Otherwise, determine that the regulation capacity of the energy storage unit has reached saturation, end and exit.

[0105] The above steps dynamically allocate and adjust power based on the SOC value priority of the energy storage device, ensuring that the energy storage system can effectively respond to frequency and voltage fluctuations in the microgrid. By allocating power starting with the energy storage device with the higher SOC value and prioritizing energy storage devices in better condition for regulation, the utilization efficiency of energy storage resources is optimized. This method can balance the load of each energy storage unit, preventing certain devices from over-discharging or over-charging, thereby extending the service life of the energy storage device. At the same time, it ensures that the microgrid can respond quickly to frequency or voltage fluctuations, maintaining the stability and reliability of the system. When the regulation capacity of the energy storage device reaches saturation, the system can promptly stop power distribution to prevent overload and ensure the safe operation of the system.

[0106] In this embodiment, the control process of the synchronization control module includes:

[0107] Inverters in VSG mode exhibit voltage source characteristics. Therefore, starting with the second inverter, before the new device is put into operation, it is necessary to complete synchronization and paralleling using the synchronization control module to ensure that the voltage of the inverter connected to this device is fully synchronized with the voltage of the inverter already in VSG mode, thereby achieving "zero" impact. Taking the synchronization control before the second VSG-characteristic inverter is added as an example, the specific implementation of the synchronization control module is as follows:

[0108] Taking phase A as an example, the output voltage U of the second converter to be incorporated into the microgrid for voltage support is A_converter2 and the output voltage U of the first converter that has been put into operation A_converter1 They are:

[0109]

[0110] Among them, U A_converter1 is the output voltage of the first converter, U A_converter2 is the output voltage of the second converter, U1 and U2 are the voltage amplitudes of the two converter outputs, ω1 and ω2 are the angular frequencies of the two converter outputs, and is the initial phase angle of the output sides of the two converters.

[0111] The instantaneous voltage difference between the two converter output sides is:

[0112]

[0113] Where Δu is the instantaneous difference between the output voltages of the second converter and the first converter. To achieve Δu = 0, the specific steps are:

[0114] By controlling the size of U2, it can be made equal to the voltage amplitude U of the first converter U1. m Equal, that is, U2=U1=U m Then the instantaneous voltage difference can be simplified as:

[0115]

[0116] From the above formula (4), we can see that by controlling That is, ω1=ω2 and That is, by controlling the angular frequency and phase of the output side voltages of the two converters to be equal, the instantaneous voltage difference Δu=0 can be achieved.

[0117] Therefore, by controlling the amplitude and phase of the output voltage of the second converter to be equal to those of the first converter, the second converter can be seamlessly integrated into the microgrid. After receiving the PQ to VSG command, the second converter adjusts the output voltage amplitude and phase in real time. The specific steps are:

[0118] 1) After the VSG algorithm, the voltage phase of the second converter output side is obtained and reference amplitude U * , and the voltage phase of the first converter output side and amplitude U out_converter1 , processed according to formula (5) to obtain ΔU, U ref_converter2 and in The initial values ​​of and dU are set to 0;

[0119]

[0120] in, is the phase adjustment step cumulative value, dU is the amplitude adjustment step cumulative value, U ref_converter2 is the reference voltage amplitude at the output side of the second converter, is the voltage phase difference between the two converters, ΔU is the voltage amplitude difference between the two converters, and U out_converter1 is the output voltage amplitude of the first converter.

[0121] 2) According to and ΔU, determine the values ​​of the symbolic variables var1 and var2 to clearly adjust the direction, and adjust the and dU for regulation;

[0122]

[0123] Among them, var1 and var2 are symbolic variables, with values ​​of 1, -1 or 0. is the phase adjustment step, and step_U is the voltage adjustment step.

[0124] 3) Loop judgment and the size of ΔU, if ΔU is less than the amplitude difference threshold and If the phase difference is less than the threshold, the synchronization process is considered to be completed.

[0125] Through the operation of the above-mentioned synchronization control module, it is possible to ensure that the voltage amplitude and phase of multiple converters in VSG mode are fully matched when they are connected to the microgrid, thereby achieving "zero" impact synchronous grid operation. This process synchronizes the voltage amplitude and phase of the second converter with the voltage of the converter that has been put into operation in real time, avoiding system fluctuations or shocks caused by voltage mismatch. This method not only improves the stability of the microgrid system, but also avoids instantaneous voltage fluctuations when the converter is connected to the grid, ensuring the safety and reliability of the microgrid, especially when energy storage equipment and distributed energy resources such as photovoltaics jointly regulate the system frequency and voltage.

[0126] In summary, the proposed method for constructing and controlling a hybrid PV-storage-charging AC / DC microgrid can dynamically adjust the number of energy storage devices, photovoltaic panels, and electric vehicles deployed based on frequency fluctuations during the microgrid's transition from grid-connected to off-grid operation. This allows for rapid establishment of an AC busbar to support the microgrid's voltage and frequency, ensuring operational stability. This reduces the traditional microgrid's reliance on external power grids, improves the system's ability to regulate itself, and reduces the scale of energy storage equipment within the microgrid, lowering its cost, by temporarily supporting the microgrid's voltage and frequency through electric vehicles.

[0127] According to another aspect of an embodiment of the present application, an electronic device is provided, including a processor and a memory, wherein the processor is configured to implement the steps of the method when executing a computer program stored in the memory.

[0128] In the above embodiments of the present invention, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0129] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only exemplary. For example, the division of the units can be a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0130] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0131] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk, etc. Various media that can store program codes.

[0132] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for controlling the construction of a photovoltaic, storage and charging AC / DC hybrid microgrid, characterized in that: The steps include: The energy storage converters are graded from high to low according to the SOC value of the energy storage device. The working mode of the energy storage converter with the highest priority is switched from PQ mode to VSG mode. Obtain the voltage and frequency of the microgrid and determine whether the voltage and frequency fluctuation range of the microgrid exceeds the regulation dead zone; When the frequency fluctuation of the microgrid exceeds the regulation dead zone, the active power compensation required is calculated through the active-frequency control of the VSG mode to adjust the active power output of the microgrid and energy storage equipment; When the voltage fluctuation of the microgrid exceeds the regulation dead zone, the reactive power output of the microgrid and energy storage equipment is adjusted through the reactive-voltage control of the VSG mode; Detect the SOC value of the energy storage device and adjust the operating mode of the energy storage device step by step from high to low SOC value, switching from PQ mode to VSG mode. Through the synchronization control module, the voltage amplitude and phase angle of the energy storage converter are synchronized with the energy storage converter that has been put into VSG mode. The energy storage device supports the voltage and frequency of the microgrid step by step. If all energy storage devices are switched to VSG mode and still cannot respond to voltage and frequency fluctuations of the microgrid, the photovoltaic devices on the AC bus are put into operation in descending order of adjustable capacity; Before the photovoltaic equipment is put into operation, the DC / AC converter of the photovoltaic equipment is synchronized with the voltage amplitude and phase angle of the energy storage device that has been put into operation through the synchronization control module; Switch the operating mode of the photovoltaic equipment from PQ mode to VSG mode, and jointly support the voltage and frequency of the microgrid with the energy storage unit; If the microgrid voltage and frequency fluctuations still cannot be fully responded to, the control algorithm of the charging pile is adjusted to feed the microgrid through electric vehicles to establish the microgrid voltage; Before the electric vehicle is put into use, the voltage amplitude and phase of the electric vehicle charging pile are synchronized with the voltage amplitude and phase angle of the energy storage converter that has been put into use through the synchronization control module; The electric vehicle battery and energy storage equipment are controlled by the synchronous control module to jointly support the microgrid voltage and frequency with the photovoltaic array.

2. The photovoltaic storage and charging AC / DC hybrid microgrid construction control method according to claim 1, characterized in that: The methods for grading energy storage converters from high to low according to the SOC value of the energy storage device include: Obtain the SOC value of each energy storage device; Sort the SOC values ​​of the energy storage devices and set the priority of each energy storage device in responding to microgrid fluctuations according to the SOC value from large to small; The power required for regulation is sent to each energy storage device in turn, and power is allocated according to priority and maximum charge and discharge power until the power allocation is completed.

3. The photovoltaic storage and charging AC / DC hybrid microgrid construction control method according to claim 2, characterized in that: The method for sequentially distributing the required power to each energy storage device and allocating power according to priority and maximum charge and discharge power until power allocation is complete includes: Initialize the power to be allocated in response to frequency and voltage fluctuations in the microgrid; The PCS of the energy storage device with the highest priority is traversed from each energy storage device and is taken as the current PCS. If the maximum charge / discharge power value of the current PCS is less than the power to be allocated, the maximum charge / discharge power value of the current PCS is used as the charge / discharge power of the current PCS, and the charge / discharge power of the current PCS is subtracted from the power to be allocated to obtain the new power to be allocated. Otherwise, the power to be allocated is used as the charge / discharge power of the current PCS. Determine whether each PCS has been traversed. If not, jump to the previous step. Otherwise, determine that the regulation capacity of the energy storage unit has reached saturation, end and exit.

4. The photovoltaic storage and charging AC / DC hybrid microgrid construction control method according to claim 1, characterized in that: Active power-frequency control in VSG mode is based on the rotor characteristics of the synchronous generator. The required active power compensation is calculated using the rotor motion equation. The specific calculation formula is as follows: Where P is the active power compensation required for the system to reach the target frequency, J is the inertia coefficient of the virtual synchronous generator, ω0 is the rated angular frequency, ω is the output angular frequency of the VSG, is the rate of change of angular frequency, and D is the damping coefficient of the virtual synchronous generator.

5. The photovoltaic storage and charging AC / DC hybrid microgrid construction control method according to claim 1, characterized in that: The calculation formula for the active power change of inertia response in VSG mode is: Among them, P Inertia is the change in active power of the microgrid during inertia response, T J is the equivalent inertia time constant, f N is the rated frequency of the microgrid system, is the frequency change rate of the microgrid, P N Rated active power of network-forming equipment; The calculation formula for damping active power in VSG mode is: P Damping =D(ω-ω0) Among them, P Damping is the damping active power provided by the virtual synchronous generator, D is the damping coefficient of the virtual synchronous generator, ω0 is the rated angular frequency, and ω is the output angular frequency of the VSG.

6. The photovoltaic storage and charging AC / DC hybrid microgrid construction control method according to claim 1, characterized in that: The reactive power-voltage control calculation formula in VSG mode is: ΔU=D q (Q ref -Q e )+(U ref -U) Among them, ΔU is the voltage change, D q is the reactive power droop coefficient, Q ref is the reactive power setting value, Q e is the reactive power output of the converter, U ref is the voltage setting value, and U is the output voltage amplitude of the converter.

7. The photovoltaic storage and charging AC / DC hybrid microgrid construction and control method according to claim 1, characterized in that: The control steps of the synchronization control module are: The voltage amplitude and phase of the energy storage device, photovoltaic device or electric vehicle charging pile converter are controlled by the synchronous control module to make them equal to the voltage amplitude and phase of the VSG converter that has been put into use, ensuring that the instantaneous voltage difference of the converters working in each VSG mode is zero when running in parallel; According to the difference between the voltage amplitude and phase, the phase adjustment step and the amplitude adjustment step are adjusted to perform the synchronization process until the voltage amplitude and phase are completely synchronized.

8. The photovoltaic storage and charging AC / DC hybrid microgrid construction control method according to claim 7, characterized in that: The control calculation formula of the synchronous control module is: Where, Δu is the instantaneous difference between the output voltages of the second converter and the first converter, U A_converter1 is the output voltage of the first converter, U A_converter2 is the output voltage of the second converter, U1 and U2 are the voltage amplitudes of the two converter outputs, ω1 and ω2 are the angular frequencies of the two converter outputs, and are the initial phase angles on the output sides of the two converters respectively; The control formula of the synchronization process is: By adjusting the phase difference and amplitude difference, the voltage synchronization of the two converters can be gradually achieved.

9. An electronic device, characterized in that: The device comprises a processor and a memory, wherein the processor is configured to implement the steps of the photovoltaic storage charging AC / DC hybrid microgrid construction control method according to any one of claims 1 to 8 when executing a computer program stored in the memory.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the photovoltaic storage charging AC / DC hybrid microgrid construction control method according to any one of claims 1 to 8 are executed.

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