Optical storage and charging AC / DC hybrid micro-grid construction control method and device, and medium

Abstract

The invention relates to an optical storage and charging alternating current and direct current hybrid micro-grid construction control method and device and a medium. According to the method, level-to-level management is carried out on an energy storage converter according to an SOC value of an energy storage device. And the converter with the high priority is switched to a VSG mode, and whether the voltage and frequency fluctuation of the micro-grid exceeds an adjustment dead zone or not is detected. When the frequency fluctuation is exceeded, active power output is adjusted through a VSG mode; when the voltage fluctuation is exceeded, the reactive power output is adjusted. And the energy storage equipment is switched to the VSG mode step by step, and when the requirements cannot be met, the photovoltaic equipment and the electric automobile support power grid are put into use in sequence. Before the photovoltaic equipment is connected, the voltage of the photovoltaic equipment is synchronized to be consistent with that of the connected energy storage equipment, and the VSG mode is converted. And if further support is still needed, the electric vehicle is used for feeding by adjusting a charging pile control algorithm. And the voltage and the phase need to be synchronized before the electric vehicle is connected so as to cooperatively support the micro-grid. According to the method, the voltage and frequency stability of the micro-grid system is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of microgrid control, and in particular to a photovoltaic storage and charging AC / DC hybrid microgrid control method, equipment and medium. Background Art

[0002] The photovoltaic storage charging AC / DC hybrid microgrid consists of photovoltaic units, energy storage units and charging piles. It can make full use of the advantages of photovoltaic clean energy and energy storage to build a green and low-carbon park that couples the power load of the park, reduce carbon emissions, and improve economic benefits. The intermittent and volatile nature of photovoltaic power generation can easily cause instability in the frequency and voltage of the microgrid. The current microgrid system mainly uses the grid-following (GFL) converter, which is connected to the grid and cannot actively respond to changes in the frequency and voltage of the grid. It lacks inertia and damping capacity, so it cannot support and adjust the frequency and voltage. The grid-forming (GFM) converter can provide inertia support for the microgrid and has a certain active support capability. However, the existing inventions are not comprehensive enough in the research on the voltage and frequency support methods of the microgrid. Therefore, how to propose a comprehensive method to establish and maintain the bus voltage, and when the voltage and frequency of the photovoltaic storage charging AC / DC hybrid microgrid system fluctuate, it can actively support the voltage and frequency of the microgrid, which has become a key problem that needs to be solved urgently.

[0003] Regarding the network control method of new energy stations, Chinese patent number CN118232365A discloses a control method and device for new energy stations based on network construction technology. The invention proposes a control method for energy storage, photovoltaics, and wind turbines in the station to support the grid frequency when the new energy station is connected to the grid. The energy storage equipment in the station is graded according to the adjustment coefficient. When the grid frequency fluctuation range exceeds the regulation dead zone, the energy storage equipment supports the grid voltage and frequency step by step, and then calculates the gap capacity after energy storage support to determine the photovoltaics and wind turbines that need to be invested. The invention mainly studies the microgrid of new energy stations connected to the grid. Its topology does not consider the AC / DC hybrid microgrid. When multiple energy storage units are operated in parallel, the state of charge (SOC) balance problem between energy storage units is not fully considered, and the amplitude and phase synchronization problem of VSG (Virtual synchronous generator) working mode converters when operating in parallel is not considered. Summary of the invention

[0004] The present invention provides a photovoltaic storage and charging AC / DC hybrid microgrid control method, equipment and medium, the purpose of which is to solve the problem of how to dynamically adjust the number of energy storage devices, photovoltaic systems and electric vehicles when the microgrid switches from grid-connected to islanded operation mode, so as to stabilize the voltage and frequency of the microgrid, improve the system's autonomous regulation capability and reduce costs.

[0005] To achieve the above object, the first aspect of the present invention provides a photovoltaic storage charging AC / DC hybrid microgrid construction 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, and 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 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 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, adjust the working mode of the energy storage device step by step from high to low SOC value, switch from PQ mode to VSG mode, and synchronize the voltage amplitude and phase angle of the energy storage converter with the energy storage converter that has been put into VSG mode through the synchronization control module. The energy storage device supports the voltage and frequency of the microgrid step by step;

[0011] If all energy storage devices are still unable to respond to voltage and frequency fluctuations of the microgrid after switching to VSG mode, 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 use, the DC / AC converter of the photovoltaic equipment is synchronized with the voltage amplitude and phase angle of the energy storage equipment that has been put into use through the synchronization control module;

[0013] Switch the working 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 device 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 the power is allocated according to the priority and the maximum charge and discharge power until the power allocation is completed.

[0021] Further, the method of sending the power required for adjustment to each energy storage device in sequence and distributing the power according to the priority and the maximum chargeable and dischargeable power until the power distribution is completed includes:

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

[0023] The PCS of the energy storage device with the highest priority is traversed from each energy storage device 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 the VSG mode is based on the rotor characteristics of the synchronous generator, and 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 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-building equipment.

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

[0032] P Damping =D(ω-ω0)

[0033] 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.

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

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

[0036] 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.

[0037] Furthermore, 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 inverter are controlled by the synchronous control module to make them equal to the voltage amplitude and phase of the VSG inverter that has been put into use, ensuring that the voltage instantaneous value difference of the inverters working in each VSG mode is zero when they are connected in parallel;

[0039] 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.

[0040] Furthermore, the control calculation formula of the synchronous control module is:

[0041]

[0042] Where, Δu is the instantaneous difference between the output voltage of the second converter and the first converter, U A_converter1 is the output voltage of the first converter, UA_converter2 is the voltage at the output side of the second converter, U1 and U2 are the voltage amplitudes at the output sides of the two converters, ω1 and ω2 are the angular frequencies at the output sides of the two converters, 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-mentioned purpose, the second aspect of the present invention provides an electronic device, including a processor and a memory, wherein the processor is used to implement the steps of the photovoltaic storage charging AC / DC hybrid microgrid network control method when executing the computer program stored in the memory.

[0047] To achieve the above-mentioned purpose, 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 charging AC / DC hybrid microgrid control method, device and medium, which, based on the dynamic coordinated adjustment mechanism of energy storage equipment, photovoltaic system and electric vehicle, effectively solves the problem of system instability caused by frequency and voltage fluctuations when the microgrid is connected to the grid and switched to island mode. Specifically, the present invention adjusts the working mode of the energy storage equipment step by step by grading according to the SOC value priority of the energy storage equipment, switching from PQ mode to VSG mode to support the voltage and frequency of the microgrid; at the same time, when the energy storage equipment and photovoltaic system cannot fully meet the grid demand, electric vehicles are further introduced to feed power to the microgrid through charging piles, forming a multi-level and diversified power regulation mechanism, which enhances the system's adaptive ability. 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 adjustment ability 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 1It 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 It is a microgrid control flow chart disclosed in an embodiment of the present invention.

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

[0054] Figure 4 It 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 scheme of the present invention, the technical scheme 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 described embodiments 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 creative work should fall within the scope of protection of the present invention.

[0056] Figure 1 This is a photovoltaic storage and charging AC / DC microgrid system topology. The topology has two buses: a DC bus and an AC bus. The DC bus and the AC bus are connected through a DC / AC converter, and the DC / AC converter works in PQ mode. The AC bus is connected to the grid through a transformer. The AC / DC hybrid microgrid can switch between grid-connected mode and island mode. When the microgrid is connected to the grid, all converters work in PQ mode to control the distribution of active and reactive power. When the microgrid is islanded, at least one converter switches to VSG mode to simulate the behavior of a synchronous generator to provide virtual inertia and damping, thereby supporting the voltage and frequency stability of the microgrid.

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

[0058] Understandably, traditional synchronous generators provide inertia through their rotating rotors, which helps 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 like synchronous generators when the system frequency changes. Specifically, virtual inertia enables microgrids to provide a certain amount of power support when the frequency drops, slowing the frequency drop and helping the grid to restore stability.

[0059] Damping refers to slowing down the oscillation of the system by adjusting the power. Traditional synchronous generators generate damping through electromagnetic force, which helps the power grid to quickly stabilize when frequency fluctuations occur. Virtual synchronous generators simulate this damping effect by adjusting the output power (i.e., active power), helping to reduce excessive oscillations in the system and restore the power grid to a stable state. Damping response usually occurs when the grid frequency deviates from the rated value, providing the necessary power correction to prevent excessive frequency deviations.

[0060] In the power system, the traditional synchronous generator adjusts the reactive power through the excitation electromotive force to cope with the fluctuation of reactive load, thereby maintaining the voltage stability of the system. In the virtual synchronous generator, voltage regulation and excitation control together constitute the reactive-voltage control loop. By obtaining the reference voltage from the voltage regulation unit of the synchronous generator, the voltage droop control characteristics of the synchronous generator are realized, ensuring the reactive power balance and voltage stability in the power system, and 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 through a DC / AC converter, which has two working modes: PQ and VSG. Other AC loads with voltage matching are directly connected to the AC bus. The photovoltaic unit is connected to the DC bus through a unidirectional DC / DC converter to provide DC power input. The energy storage module and charging pile are connected to the DC bus through a bidirectional DC / DC converter, which can realize the charge and discharge control of the battery of the electric vehicle connected to the energy storage system and the charging pile. Other DC loads with voltage matching are directly connected to the DC bus. This configuration enables the energy storage device to provide power support when the power demand is insufficient. At the same time, the charging pile can also provide charging services for electric vehicles or support microgrids through reverse feeding.

[0063] In addition, the DC subsystem is connected to photovoltaic power generation units and charging pile units, 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 in 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 DC load voltage levels. 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 a 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 P is the charging and discharging power of the energy storage unit. It takes negative value when the energy storage device is discharging and positive value 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 flowchart 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 photovoltaic storage charging AC / DC hybrid microgrid construction control method, comprising the following steps:

[0068] Step S100, classifying the energy storage converters from high to low according to the SOC values ​​of the energy storage devices, and switching 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, detecting the SOC value of the energy storage device, adjusting the working mode of the energy storage device step by step from high to low SOC values, switching from PQ mode to VSG mode, and synchronizing the voltage amplitude and phase angle of the energy storage converter with the energy storage converter that has been put into VSG mode through the synchronization control module, and the energy storage device supports the voltage and frequency of the microgrid step by step;

[0073] Step S600: If all energy storage devices are still unable to respond to voltage and frequency fluctuations of the microgrid after switching to the VSG mode, photovoltaic devices of the AC bus are put into operation in descending order of adjustable capacity;

[0074] Step S700: Before the photovoltaic device is put into operation, the DC / AC converter of the photovoltaic device 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 the PQ mode to the VSG mode, and jointly support the voltage and frequency of the microgrid with the energy storage unit;

[0076] Step S900: If the voltage and frequency fluctuations of the microgrid 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 voltage of the microgrid;

[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 converter that has been put into operation through the synchronization control module;

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

[0079] In this embodiment, as described in the above steps S100 to S500 (first processing module), the energy storage converter (PCS) is graded from high to low according to the SOC of the energy storage device, and the PCS working mode with the highest priority is converted from PQ to VSG. The voltage and frequency of the microgrid are obtained. When the fluctuation range of the voltage and frequency of the microgrid exceeds the regulation dead zone due to disturbance or load change, the active power compensation and reactive power compensation required for the system to reach the target frequency are determined based on the current voltage and frequency of the microgrid.

[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 through the rotor motion equation. The active power calculation formula that needs to be compensated is 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, and provide 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-building 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 self-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 reactive power and voltage output by the converter 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] According to the SOC of the energy storage device, the voltage and frequency of the microgrid are supported step by step to solve 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, and the working mode of the energy storage converter connected to the energy storage device with the largest SOC is switched from PQ to VSG to establish the AC bus voltage and support the voltage and frequency of the microgrid. At this time, other converters are still working in PQ mode. When the power of the energy storage device is insufficient to support the voltage and frequency of the microgrid, the working mode of the energy storage converter connected to the energy storage device is switched from PQ to VSG step by step according to the order of SOC from high to low, and the energy storage device supports the voltage and frequency of the microgrid step by step.

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

[0096] It is understandable that by gradually introducing photovoltaic equipment and achieving voltage and phase synchronization, the photovoltaic system can work seamlessly with the energy storage unit to provide additional voltage and frequency support. By switching the photovoltaic converter to VSG mode and simulating the inertia and damping characteristics of the virtual synchronous generator, the dynamic regulation capability of the microgrid is enhanced, helping the system to better cope with frequency fluctuations, reducing dependence on the external power grid, and improving the autonomous regulation and stability of the microgrid. This mechanism effectively improves the self-sustaining ability of the microgrid in island mode and ensures the smoothness and reliability of the system operation.

[0097] In this embodiment, as described in the above steps S900 to S1100 (the third processing module), when the photovoltaic array cannot generate electricity or the power generation is insufficient due to darkness or shadows, and all energy storage devices and photovoltaics cannot respond to the voltage and frequency fluctuations of the microgrid after being put into use, the control algorithm of the charging pile on the AC bus side 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, and the working mode of the corresponding DC / AC converter is switched from PQ to VSG, and the voltage amplitude and phase angle of the converter that has been put into use are synchronized through the third synchronization control module, 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 The flow chart of energy storage device classification and power allocation is as follows: Figure 4 As shown, for grading energy storage devices according to SOC and allocating power to respond to microgrid frequency fluctuations, the specific steps 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 order of SOC values ​​from large to small;

[0101] 3) The power required for voltage and frequency regulation is sent to each energy storage device in turn 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 allocated. The specific steps are as follows:

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

[0103] 3.2) From each energy storage device, traverse and take out the PCS of the energy storage device with the highest priority 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 each PCS has 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 ensure that the energy storage system can effectively respond to the frequency and voltage fluctuations of the microgrid by dynamically allocating and adjusting power according to the SOC value priority of the energy storage device. By allocating power starting from the energy storage device with a higher SOC and giving priority to the energy storage device in better condition for adjustment, the utilization efficiency of the energy storage resources is optimized. This method can balance the load of each energy storage unit and avoid excessive discharge or charging of certain devices, thereby extending the service life of the energy storage device. At the same time, it ensures that the microgrid can respond quickly when facing frequency or voltage fluctuations and maintain the stability and reliability of the system. When the regulation capacity of the energy storage device reaches saturation, the system can stop power distribution in time 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] The converter in VSG working mode presents voltage source characteristics, so starting from the second converter equipment, before the new equipment is put into use, it is necessary to complete the synchronization through the synchronization control module to make the converter connected to the equipment fully synchronized with the converter voltage that has been put into VSG working mode, thereby achieving "zero" impact. Taking the synchronization control before the second VSG characteristic converter is connected 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 connected to 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 voltage at the output side of the second converter, U1 and U2 are the voltage amplitudes at the output sides of the two converters, ω1 and ω2 are the angular frequencies at the output sides of the two converters, 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] Wherein, 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 is 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 voltages on the output sides of the two converters to be equal, the voltage instantaneous value difference Δu=0 can be achieved.

[0117] Therefore, by controlling the amplitude and phase of the voltage on the output side of the second converter to make them equal to the amplitude and phase of the voltage on the output side of the first converter, the second converter can be integrated into the microgrid without impact. After receiving the PQ to VSG instruction, the second converter adjusts the output side 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 , 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 sign variables var1 and var2 to clearly adjust the direction, and adjust according to formula (6) 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) Cycle 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 can be ensured 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 adjusts the voltage amplitude and phase of the second converter in real time to synchronize it with the voltage of the converter that has been put into use, 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 the collaborative operation effect when energy storage equipment and distributed energy such as photovoltaics jointly adjust the system frequency and voltage.

[0126] In summary, the grid control method of the photovoltaic storage and charging AC / DC hybrid microgrid proposed in the present invention can dynamically adjust the number of energy storage devices, photovoltaic panels and electric vehicles invested according to the frequency fluctuation of the microgrid when the microgrid system is connected to the grid and switched to off-grid operation, quickly establish an AC bus, support the voltage and frequency of the microgrid to ensure the stability of the microgrid operation. It reduces the dependence of traditional microgrids on external power grids, improves the system's ability to adjust itself, and reduces the scale of energy storage devices in the microgrid by temporarily supporting the voltage and frequency of the microgrid through electric vehicles feeding the microgrid, thereby reducing the cost of the microgrid.

[0127] According to another aspect of an embodiment of the present application, there is further provided an electronic device, 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 emphasis. 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 schematic. For example, the division of the units can be a logical function division. There may be other division methods in actual implementation. For example, 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, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of 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, in essence, 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, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server or a 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, disk or optical disk and other 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 principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A photovoltaic storage and charging AC / DC hybrid microgrid construction control method, 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, and 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 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 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, adjust the working mode of the energy storage device step by step from high to low SOC value, switch from PQ mode to VSG mode, and synchronize the voltage amplitude and phase angle of the energy storage converter with the energy storage converter that has been put into VSG mode through the synchronization control module. The energy storage device supports the voltage and frequency of the microgrid step by step; If all energy storage devices are still unable to respond to voltage and frequency fluctuations of the microgrid after switching to VSG mode, the photovoltaic devices on the AC bus are put into operation in descending order of adjustable capacity; Before the photovoltaic equipment is put into use, the DC / AC converter of the photovoltaic equipment is synchronized with the voltage amplitude and phase angle of the energy storage equipment that has been put into use through the synchronization control module; Switch the working 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 device are controlled by the synchronous control module to jointly support the microgrid voltage and frequency with the photovoltaic array.

2. The photovoltaic storage charging AC / DC hybrid microgrid construction control method according to claim 1, characterized in that: 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 the power is allocated according to the priority and the maximum charge and discharge power until the power allocation is completed.

3. The photovoltaic storage charging AC / DC hybrid microgrid construction control method according to claim 2, characterized in that: The method of sending the power required for regulation to each energy storage device in sequence and distributing the power according to the priority and the maximum chargeable and dischargeable power until the power distribution is completed includes: Initialize the power to be allocated in response to frequency and voltage fluctuations of the microgrid; The PCS of the energy storage device with the highest priority is traversed from each energy storage device 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 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 through 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 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 It is the rated active power of the network-building 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 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 charging AC / DC hybrid microgrid construction control method according to claim 1, characterized in that: The control steps of the synchronous control module are: The voltage amplitude and phase of the energy storage device, photovoltaic device or electric vehicle charging pile inverter are controlled by the synchronous control module to make them equal to the voltage amplitude and phase of the VSG inverter that has been put into use, ensuring that the voltage instantaneous value difference of the inverters working in each VSG mode is zero when they are connected 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 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 voltage of the second converter and the first converter, U A_converter1 is the output voltage of the first converter, U A_converter2 is the voltage at the output side of the second converter, U1 and U2 are the voltage amplitudes at the output sides of the two converters, ω1 and ω2 are the angular frequencies at the output sides of the two converters, 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: It comprises a processor and a memory, wherein the processor is used to implement the steps of the photovoltaic storage charging AC / DC hybrid microgrid construction control method as claimed in any one of claims 1 to 8 when executing the 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 the 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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