Control method, system, equipment and medium for light-storage direct-flexible micro-grid system

Abstract

The invention discloses an optical storage direct-flexible micro-grid system control method, system and device and a medium, and belongs to the technical field of power supply or power distribution circuit control, and the method comprises the steps: obtaining power system device data, and constructing a plurality of optical storage direct-flexible micro-grid systems; an inter-line direct current power flow controller is connected in series in a line module of each optical storage direct flexible micro-grid system, wherein the inter-line direct current power flow controller comprises a connection unit and an energy center; connecting units are connected in series between the lines to adjust the direct-current voltage drop of each line and control the power flow; and carrying out power distribution on each optical storage direct-flexible micro-grid system by utilizing an energy center. According to the invention, the optical storage direct-flexible micro-grid system is reasonably designed, and the power flow control accuracy of the optical storage direct-flexible micro-grid system is effectively improved by using the inter-line direct-current power flow controller; the multi-scene control requirement of high-proportion photovoltaic access of the direct-current micro-grid in the future, the characteristic of high response speed of the direct-current power grid and the generation of a micro-grid group represented by a light-storage direct-current flexible park are facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit control for power supply or distribution, and in particular to a control method, system, equipment and medium for a photovoltaic-storage-direct-flexible microgrid system. Background Art

[0002] Against the backdrop of a global energy transition, the extensive use of traditional fossil fuels has triggered a series of serious problems, including environmental pollution, resource depletion, and climate change caused by greenhouse gas emissions. my country has actively responded to the international community's call for sustainable development, and the proposed "dual carbon" goals have charted the course for energy restructuring. Among numerous new energy sources, solar energy, with its abundant reserves, clean energy, and environmentally friendly characteristics, has become a focal point for global energy research and development. While eastern my country lacks the idle land required for large-scale photovoltaic power station construction, its abundant building resources provide ample space for distributed photovoltaic power generation. The concept of solar-storage, direct-flexible buildings has emerged, creating new possibilities for achieving energy self-sufficiency and low-carbon development in the building sector.

[0003] However, PV-storage, direct-to-flexible building parks face many technical challenges in their actual planning and operation. Due to the different regional planning of each PV-storage, direct-to-flexible building, there are significant differences in their power supply and demand. This makes it difficult to achieve efficient power exchange between buildings in the park, resulting in energy waste and unstable supply. Although DC power flow controllers play an important role in regulating the power transmission path and power distribution of the DC grid and can ensure the stable operation of the grid, inter-line power flow controllers have unique advantages. For example, they achieve power flow regulation through energy exchange between transmission lines, avoiding additional external circuit consumption, bidirectional power flow regulation and reduced capacity requirements, low energy transfer loss, stable capacitor voltage and no need for external power supply maintenance, etc., showing broad market prospects. However, to date, there has been no relevant research on the application of DC power flow controllers to PV-storage, direct-to-flexible building parks. This technical gap has limited the further development of PV-storage, direct-to-flexible building parks and the improvement of energy utilization efficiency, and urgently needs in-depth research and exploration. Summary of the Invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the technical problem solved by the present invention is to solve the problem of flexible flow control between DC microgrids in the photovoltaic storage DC flexible microgrid group and the problem of large line loss and inaccurate control.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a control method for a photovoltaic-storage-direct-flexible microgrid system, which comprises the following steps:

[0007] Acquire power system equipment data and build multiple photovoltaic, storage, direct-current and flexible microgrid systems;

[0008] The photovoltaic storage direct current flexible microgrid system includes a photovoltaic module, an energy storage module, a load module, a line module and a DC grid module;

[0009] Connecting the line-to-line DC power flow controller in series to the line modules of each solar-storage-direct-flexible microgrid system, wherein the line-to-line DC power flow controller includes a connection unit and an energy hub;

[0010] The connection unit is connected in series between each line to adjust the DC voltage drop of each line and control the power flow;

[0011] The energy hub is used to distribute power to each photovoltaic, storage, direct-flexible microgrid system.

[0012] As a preferred solution of the control method of a photovoltaic-storage-direct-flexible microgrid system described in the present invention, wherein: obtaining power system equipment data and constructing multiple photovoltaic-storage-direct-flexible microgrid systems include:

[0013] Utilizing a first voltage source converter set to supply power to each photovoltaic-storage-direct-flexible microgrid system, wherein the first voltage source converter set operates in a constant power mode;

[0014] A second set of voltage source converters is used to provide voltage to the DC bus, wherein the second set of voltage source converters operates in a constant voltage mode.

[0015] As a preferred solution of the control method of a photovoltaic-storage-direct-flexible microgrid system described in the present invention, a line-to-line DC power flow controller is connected in series to the line modules of each photovoltaic-storage-direct-flexible microgrid system, and the line-to-line DC power flow controller includes a connection unit and an energy hub, including:

[0016] The energy center of the line-to-line DC power flow controller includes an inductive topology energy center or a capacitive topology energy center;

[0017] The connection unit or energy center is used to connect the capacitor in series to each photovoltaic storage direct-flexible microgrid system, and the amplitude of the equivalent direct current voltage source is controlled by controlling the positive and negative control of the connected capacitor voltage to perform energy flow and power regulation.

[0018] As a preferred solution of the control method of a photovoltaic storage direct-flexible microgrid system described in the present invention, the inductive topology energy center includes:

[0019] When the energy hub adopts an inductive topology, the connection units connected in series between the lines contain capacitors. The capacitors are connected in series to the PV-storage-direct-flexible microgrid system through different switching modes of the connection units. The inductive topology energy hub includes four working modes.

[0020] Mode 1: When the capacitor voltage is negative, the inductor in the inductive topology energy hub transfers energy to the solar-storage direct-flexible microgrid system;

[0021] Mode 2: When the capacitor voltage is positive, the PV-storage direct-flexible microgrid system transfers energy through the capacitor to the inductor in the inductive topology energy hub;

[0022] Mode 3: When the inductive topology energy center is bypassed, the power flow is affected by the capacitor voltage of the connection unit in the line module of the solar-storage direct-flexible microgrid system;

[0023] Mode 4: Bypass the energy center and connection unit at the same time, and the flow is uncontrollable.

[0024] As a preferred solution of the control method of a photovoltaic storage direct-flexible microgrid system described in the present invention, the capacitive topology energy center includes:

[0025] When the energy hub is a capacitive topology, a certain line is selected to connect to the energy hub through the switch state of the connection unit, and the positive and negative voltage of the capacitor are selected through the switch to perform energy exchange. The capacitive topology energy hub includes three working modes;

[0026] Mode 1: The capacitor is connected to the PV-storage-direct-flexible microgrid system with a positive voltage, and the corresponding PV-storage-direct-flexible microgrid system line power flow is reduced;

[0027] Mode 2: The capacitor is connected to the PV-storage-direct-flexible microgrid system with a negative voltage, and the corresponding PV-storage-direct-flexible microgrid system line power flow increases;

[0028] Mode 3: The capacitor of the bypass capacitor topology energy center has uncontrollable current.

[0029] As a preferred solution of the control method of a photovoltaic-storage direct-flexible microgrid system described in the present invention, the photovoltaic module includes:

[0030] The photovoltaic modules are connected to the DC bus through a boost converter;

[0031] The maximum power point tracking algorithm based on the fixed-step perturbation-observation control strategy enables the photovoltaic module to achieve maximum power output.

[0032] As a preferred solution of the control method of a photovoltaic-storage-direct-flexible microgrid system described in the present invention, the energy storage module includes:

[0033] The energy storage module is connected to the DC bus through a bidirectional buck-boost converter, and the DC bus voltage is controlled by a double closed-loop control strategy of voltage outer loop and current inner loop.

[0034] Another object of the present invention is to provide a photovoltaic-storage-direct-flexible microgrid system control system.

[0035] To solve the above technical problems, the present invention provides the following technical solutions: a photovoltaic, energy storage, direct current and flexible microgrid system control system, comprising: a microgrid design module for acquiring power system equipment data and constructing multiple photovoltaic, energy storage, direct current and flexible microgrid systems; the photovoltaic, energy storage, direct current and flexible microgrid system comprising a photovoltaic module, an energy storage module, a load module, a line module and a DC grid module;

[0036] The control module is used to connect the line-to-line DC power flow controller in series with the line modules of each photovoltaic, storage, direct and flexible microgrid system. The line-to-line DC power flow controller includes a connection unit and an energy center; the connection unit is connected in series between each line to adjust the DC voltage drop of each line and control the power flow; and the energy center is used to distribute power to each photovoltaic, storage, direct and flexible microgrid system.

[0037] The present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and is characterized in that when the processor executes the computer program, the steps of the control method of a photovoltaic-storage-direct-flexible microgrid system are implemented.

[0038] The present invention provides 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 method for controlling a photovoltaic-storage-direct-flexible microgrid system are implemented.

[0039] The beneficial effects of the present invention: The present invention rationally designs a photovoltaic, storage, direct and flexible microgrid system, and uses a line-to-line DC current controller to effectively improve the current control accuracy of the photovoltaic, storage, direct and flexible microgrid system, which is more conducive to adapting to the multi-scenario control requirements of future DC microgrids with a high proportion of photovoltaic access, the characteristics of the DC grid with a fast response speed, and the generation of microgrid groups represented by photovoltaic, storage, direct and flexible parks. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0041] Figure 1 This is a logic diagram of the overall process of the control method of the photovoltaic-storage-direct-flexible microgrid system according to an embodiment of the present invention.

[0042] Figure 2 Schematic diagram of a multi-voltage level photovoltaic-storage-direct-flexible microgrid system according to a control method for a photovoltaic-storage-direct-flexible microgrid system described in an embodiment of the present invention.

[0043] Figure 3This is a simplified topology diagram of flexible loads in a control method for a photovoltaic-storage-direct-flexible microgrid system according to an embodiment of the present invention.

[0044] Figure 4 This is a schematic diagram of the overall structure of a photovoltaic-storage-direct-flexible microgrid system group equipped with a line-to-line DC power flow controller according to a photovoltaic-storage-direct-flexible microgrid system control method according to an embodiment of the present invention;

[0045] Figure 5 This is a schematic diagram of the topological structure of the line-to-line DC power flow controller of the photovoltaic-storage-flexible microgrid system control method described in an embodiment of the present invention.

[0046] Figure 6 This is a simplified transfer function block diagram of a line-to-line inductance type DC power flow controller for a photovoltaic-storage-direct-flexible microgrid system control method according to an embodiment of the present invention.

[0047] Figure 7 Schematic diagram of a three-terminal ring network DC transmission system according to a control method for a photovoltaic-storage-direct-flexible microgrid system according to an embodiment of the present invention.

[0048] Figure 8 This is a schematic diagram of the topology of a single photovoltaic, storage, direct-flexible building microgrid according to the photovoltaic, storage, direct-flexible microgrid system control method described in an embodiment of the present invention.

[0049] Figure 9 This is a schematic diagram of the photovoltaic array output power of the photovoltaic storage direct-flexible microgrid system control method according to an embodiment of the present invention.

[0050] Figure 10 This is a schematic diagram of the energy storage power flow of the photovoltaic storage direct-flexible microgrid system control method described in an embodiment of the present invention.

[0051] Figure 11 This is a schematic diagram of the 750V DC bus side voltage situation of the photovoltaic storage direct-flexible microgrid system control method described in an embodiment of the present invention.

[0052] Figure 12 This is a schematic diagram of a three-terminal ring network DC transmission system including a line power flow controller in a control method for a photovoltaic-storage-direct-flexible microgrid system according to an embodiment of the present invention.

[0053] Figure 13 This is a circuit 1 in a control method for a photovoltaic-storage-direct-flexible microgrid system according to an embodiment of the present invention. 12 ,l 13 and l 23 Current flow diagram.

[0054] Figure 14 This is a schematic diagram of the capacitor voltage of the line power flow controller in the control method of the photovoltaic storage direct-flexible microgrid system described in one embodiment of the present invention.

[0055] Figure 15 This is a schematic diagram of the voltages at ports 1 and 2 of the DC converter in the control method of a photovoltaic-storage-direct-flexible microgrid system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0056] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in this field without creative work should fall within the scope of protection of the present invention.

[0057] Example 1, reference Figures 1 to 4 , which is the first embodiment of the present invention, provides a control method for a photovoltaic, storage, direct-flexible microgrid system, including: S100: acquiring power system equipment data and constructing multiple photovoltaic, storage, direct-flexible microgrid systems;

[0058] In an optional embodiment, the power system equipment data includes the specifications of the photovoltaic array, such as the model, quantity, rated power, open-circuit voltage, and short-circuit current of the photovoltaic modules; the characteristic data of the energy storage device, such as the type, capacity, charge and discharge efficiency, and state of charge range of the battery; the capacity and withstand voltage of the supercapacitor; the power requirements and characteristic parameters of the load, including the rated power and operating voltage of high-power DC loads, the power size and voltage requirements of other power loads, and the adjustment range and response characteristics of flexible loads; the performance parameters of the converter, such as the conversion efficiency, switching frequency, and voltage conversion ratio of the boost converter and buck-boost converter; the electrical parameters of the line, such as line resistance, inductance, capacitance, and line length, allowable current carrying capacity, etc.; and the access parameters of the external power grid. These data are crucial for accurately constructing the photovoltaic, storage, direct-current, and flexible microgrid system, realizing energy interaction and stable operation between modules, and provide a basic basis for subsequent system control and optimization.

[0059] Preferably, the photovoltaic storage direct current flexible microgrid system includes a photovoltaic module, an energy storage module, a load module, a line module and a DC grid module;

[0060] The photovoltaic storage direct current flexible microgrid system is a multi-port network consisting of multiple modules. It is necessary to realize the energy interaction between photovoltaic modules, energy storage modules, load modules, line modules and DC grid modules. The overall architecture of the designed microgrid is as follows: Figure 2 As shown, Figure 2It is a multi-voltage level photovoltaic storage direct flexible microgrid system, in which the photovoltaic array belongs to the photovoltaic module, centralized energy storage and distributed energy storage belong to the energy storage module, high-power DC load, low-power DC load, high-power AC load and low-power AC load belong to the load module, and the AC grid belongs to the DC grid module.

[0061] Preferably, the photovoltaic array of the photovoltaic module is connected to a 750V DC bus through a Boost converter; and the photovoltaic module is enabled to output maximum power through a maximum power point tracking algorithm of a fixed-step perturbation-observation control strategy.

[0062] Preferably, the energy storage module is connected to the DC bus via a bidirectional buck-boost converter, and a double closed-loop control strategy of voltage outer loop and current inner loop is adopted to control the DC bus voltage;

[0063] Specifically, the energy storage module connects batteries, supercapacitors and other structures with energy storage functions to the 750V DC bus through a bidirectional Buck / Boost converter, and adopts a dual closed-loop control strategy of voltage outer loop and current inner loop to control the DC bus voltage to maintain at around 750V; there is also distributed energy storage inside the photovoltaic storage direct-flexible microgrid system, which is connected to the secondary bus through a converter.

[0064] In an embodiment of the present invention, in the load module, high-power DC loads, above 1kW, such as electric vehicle charging piles (3kW-350kW), 5G base station DC power supplies (1kW-20kW), etc., are directly connected to the 750V bus through a power electronic converter, and other power loads, below 1kW, such as household appliances (10W-500W), etc., are connected to the secondary bus through a converter according to the required voltage.

[0065] There are also some flexible loads in the photovoltaic storage direct flexible microgrid system. This solution adopts the flexible load topology as follows Figure 3 As shown, R can be proportionally adjusted, S is a switch, U1 and U2 represent the potential at both ends of the flexible load, Figure 3 The topology diagram in the figure combines the characteristics of interruptible load, migratable load, and proportionally adjustable load.

[0066] In an embodiment of the present invention, in the DC grid module, when the photovoltaic, storage, direct and flexible microgrid system is in a grid-connected operation state, the DC bus will be connected to the external grid through an inverter to realize energy exchange; when the photovoltaic, storage, direct and flexible microgrid system is operating in an island state, the photovoltaic, storage, direct and flexible microgrid system does not exchange energy with the external grid.

[0067] Preferably, a first voltage source converter set is used to power each photovoltaic-storage-direct-flexible microgrid system, wherein the first voltage source converter set operates in a constant power mode; a second voltage source converter set is used to provide voltage for the DC bus, wherein the second voltage source converter set operates in a constant voltage mode;

[0068] like Figure 4 As shown, in Figure 4 In the microgrid group shown, the first voltage source converter set VSC1-VSCn operates in constant power mode to supply power to n photovoltaic and storage direct-current flexible microgrid systems; the second voltage source converter set VSC0 operates in constant voltage mode to provide a constant voltage for the DC bus.

[0069] S102: Connecting the line-to-line DC power flow controller in series to the line modules of each solar-storage-direct-flexible microgrid system, the line-to-line DC power flow controller including a connection unit and an energy hub;

[0070] The schematic diagram of applying the line-to-line DC power flow controller in the photovoltaic storage direct flexible microgrid system is shown in the following figure. Figure 4 As shown, Figure 4 It contains n+1 photovoltaic storage direct-flexible microgrid systems, each of which transmits a certain power, expressed as P0-P n Each PV-storage DC-flexible microgrid system is connected to DC bus 0 to DC bus n through a voltage source converter, and the voltage on each DC bus is V0-V n There is an equivalent resistance R1-R on the output lines of the photovoltaic storage direct flexible microgrid system 1 to n. n , the current flowing through the line is I1-I n There are also line connections between the PV-storage-direct-flexible microgrids. There are currents and equivalent resistances on the lines. For example, between PV-storage-direct-flexible microgrids 1 and 2, the line equivalent resistance is R 12 , the current flowing is I 12 . V c1 -V cn It represents the voltage of the line-to-line capacitors connected in series with the line-to-line DC power flow controller in each PV-storage DC-flexible microgrid system.

[0071] Preferably, the energy center of the line-to-line DC power flow controller includes an inductive topology energy center or a capacitive topology energy center;

[0072] Preferably, a connection unit or energy center is used to connect capacitors in series to each photovoltaic storage direct-flexible microgrid system, and the amplitude of the equivalent direct current voltage source is controlled by controlling the positive and negative control of the connected capacitor voltage to perform energy flow and power regulation.

[0073] It should be noted that the line-to-line DC power flow controller is equivalent to an adjustable DC voltage source on the output line of each photovoltaic, storage, direct and flexible microgrid system, and the DC voltage drop of each line is adjusted by adjusting the amplitude. The line-to-line DC power flow controller proposed in the present invention can connect multiple photovoltaic, storage, direct and flexible microgrid systems through multiple DC lines to achieve precise control of the power flow of multiple photovoltaic, storage, direct and flexible microgrid systems.

[0074] The line-to-line DC power flow controller of the present invention is as follows Figure 5 As shown, Figure 5 Middle I1-I n is the output line current of the PV-storage direct-flexible microgrid system 1 to n.

[0075] S102-1: Connect units in series between the output lines of each PV-storage-direct-flexible microgrid system to adjust the DC voltage drop of each line and control the power flow;

[0076] S102-2: Use the energy hub to distribute power to each PV-storage-direct-flexible microgrid system;

[0077] Preferably, when the energy hub is an inductive topology, the connection units connected in series between the lines contain capacitors, and the capacitors are connected in series to the solar-storage-direct-flexible microgrid system through different switching modes of the connection units. The inductive topology energy hub includes four working modes;

[0078] The four operating modes of the inductive topology energy center include:

[0079] Mode 1: When the capacitor voltage is negative, the inductor in the inductive topology energy hub transfers energy to the solar-storage direct-flexible microgrid system;

[0080] Mode 2: When the capacitor voltage is positive, the PV-storage direct-flexible microgrid system transfers energy through the capacitor to the inductor in the inductive topology energy hub;

[0081] Mode 3: When the inductive topology energy center is bypassed, the power flow is affected by the capacitor voltage of the connection unit in the line module of the solar-storage direct-flexible microgrid system;

[0082] Mode 4: Bypass the energy center and connection unit at the same time, and the flow is uncontrollable.

[0083] Preferably, when the energy hub is a capacitive topology, a certain line is selected to be connected to the energy hub through the switch state of the connection unit, and the positive and negative voltage of the capacitor are selected through the switch to perform energy exchange. The capacitive topology energy hub includes three working modes;

[0084] The three operating modes of the capacitive topology energy center include:

[0085] Mode 1: The capacitor is connected to the PV-storage-direct-flexible microgrid system with a positive voltage, and the corresponding PV-storage-direct-flexible microgrid system line power flow is reduced;

[0086] Mode 2: The capacitor is connected to the PV-storage-direct-flexible microgrid system with a negative voltage, and the corresponding PV-storage-direct-flexible microgrid system line power flow increases;

[0087] Mode 3: The capacitor of the bypass capacitor topology energy center has uncontrollable current.

[0088] In an embodiment of the present invention, the control of the line-to-line DC current controller is mainly the control of the connection units connected in series between the lines. If an inductive topology energy center is used, it is necessary to connect the capacitor in the connection unit to the inductance of the energy center according to the direction of the current and the control requirements to control the polarity of the capacitor.

[0089] In order to rigorously reveal the open-loop control mechanism from a mathematical perspective, the transient operation analysis of the capacitance of the connection unit and the inductance of the energy center is carried out to obtain the state differential equation of the DC power flow controller, and then the state space equation is obtained. According to the state space equation, we can get the following: Figure 6 The simplified control block diagram shown;

[0090] Figure 6 This is a simplified transfer function block diagram of the line-to-line DC power flow controller for the energy center of the inductive topology. The line-to-line DC power flow controller for the energy center of the inductive topology can be used in Figure 7 In the three-port solar-storage direct-flexible microgrid system ring network group shown;

[0091] Figure 6 In the figure, the bus voltages of the two PV-storage-direct-flexible microgrid systems 1 and 3 are U1 and U3 respectively. The control goal is to control the power flow, that is, to control Figure 7 Middle Line 13 The current i 13 , Figure 6 In the middle, the current I 13 for i 13 The effective value of i 13ref is the current reference value, line 13 The resistance and inductance are R 13 and L 13 , I L is the effective value of the inductor current in the DC power flow controller, D is the duty cycle of the switch in the DC power flow controller, C1 is the capacitor value in the DC power flow controller, u c1 is the voltage across the capacitor, k d is the feedforward control coefficient, PI DCPFC is the PI parameter of the line-to-line DC power flow controller, and s is the Laplace differential operator. The open-loop transfer function and the transfer function of the single-loop PI controller are obtained, and considering sufficient phase margin and large damping, the PI parameter designed by calculation is k DCPFCp=0.424, k DCPFCi =50.

[0092] Figure 7 In the figure, DC / DC represents DC-DC converter, V1, V2, V3 are voltage values, and current I 13 For line line 13 The current i 13 The effective value of the current I 23 For line line 23 The current i 23 The effective value of the current I 12 For line line 12 The current i 12 The effective value of line 13 The resistance and inductance are R 13 and L 13 , line line 23 The resistance and inductance are R 23 and L 23 , line line 12 The resistance and inductance are R 12 and L 12 .

[0093] It should be noted that the proposed line-to-line DC power flow controller topology is relatively versatile, allowing the topology of the connection unit and energy hub to be selected based on demand and cost. By employing a line-to-line DC power flow controller, the line DC power flow can be more precisely controlled, reducing line losses. Applying a line-to-line DC power flow controller in a PV-storage-direct-flexible microgrid system can optimize the power flow of the PV-storage-direct-flexible microgrid cluster, enhancing grid operational efficiency and stability.

[0094] Example 2, see Table 1 and Figures 8-11 , which is the second embodiment of the present invention, provides a control method for a photovoltaic-storage-direct-flexible microgrid system. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through experiments.

[0095] Press Figure 8 As shown, a single solar-storage direct-flexible building microgrid is built. Figure 2 The following is a general photovoltaic storage direct flexible microgrid system. In this example, Figure 8 This is a simplified microgrid structure overview of a general PV-storage direct-flexible building microgrid in island operation mode. In island operation mode, a general PV-storage direct-flexible building microgrid is not connected to the external power grid, and this embodiment does not consider the impact of distributed energy storage on the power grid.

[0096] The bus voltage of a typical PV-storage-direct-flexible building microgrid is divided into three voltage levels: 750V, 380V, and 48V. The PV cells are boosted by a Boost converter and connected to the 750V DC bus. The energy storage battery is connected to the 750V bus via a Buck / Boost converter. Other parameters of a typical PV-storage-direct-flexible building microgrid are shown in Table 1.

[0097] Table 1 Simulation parameters of PV-storage direct-flexible building microgrid

[0098]

[0099]

[0100] All loads are replaced by resistors with a resistance value of 100Ω. At 3 seconds, the flexible loads are set to participate in the regulation of the general PV-storage direct-flexible building microgrid after the bus voltage changes by 2%.

[0101] from Figure 9 It can be seen from the figure that the fixed-step perturbation-observation algorithm used in this embodiment has a certain tracking capability for the maximum power point, and the obtained output power is close to the theoretical maximum output power, but there is still a certain output ripple.

[0102] from Figure 10 and 11 It can be seen that before 3 seconds, the general PV-storage-DC-flexible building microgrid operates under light load, and the DC bus charges the energy storage. After 3 seconds, the general PV-storage-DC-flexible building microgrid operates under heavy load, and the energy storage supplies power to the DC bus through the inductor. At the same time, the flexible load detects the change in bus voltage and begins to adjust its own load to restore the bus voltage to the set value. The energy storage unit and the flexible load play an important role in maintaining the stability of the bus voltage.

[0103] Example 3, see Table 2 and Figure 12-15 This is the third embodiment of the present invention. This embodiment provides a control method for a photovoltaic, storage, direct current and flexible microgrid system, and applies a line-to-line DC power flow controller to the photovoltaic, storage, direct current and flexible microgrid system to illustrate the feasibility and beneficial effects of our solution.

[0104] Taking the three-terminal ring network DC transmission system as an example, the ability of the inductive line DC power flow controller to control the DC system power flow is verified. Figure 12 As shown in the figure, in the three-terminal ring network DC transmission system, the photovoltaic storage direct flexible microgrids 1, 2, and 3 pass through the line l 12 ,l 13 and l 23 Each line has corresponding resistance and inductance, R 12 ,R 13 ,R 23 ,L 12 ,L 13 ,L 23; The current flowing through each line is I 12 ,I 13 ,I 23 ; The bus voltages of the three photovoltaic-storage-direct-flexible microgrid ports are V1, V2, and V3 respectively. Photovoltaic-storage-direct-flexible microgrids 1 and 2 transmit P1 and P2 power to photovoltaic-storage-direct-flexible microgrid 3 respectively.

[0105] Each PV-storage DC-flexible microgrid is connected to the three-terminal ring network DC transmission system through a DC converter. The power of each microgrid is coordinated through the energy management system. Inductive inter-line DC power flow controllers are installed between transmission lines to increase the control freedom. The initial parameters of the three-terminal ring network DC transmission system are shown in Table 2.

[0106] Table 2 Parameters of the three-terminal ring network DC transmission system with inductive line-to-line DC power flow controller

[0107]

[0108]

[0109] The PV-storage direct-flexible microgrids 1 and 2 inject energy into the three-terminal ring network DC transmission system at a constant power, setting the injection power P1=P2=6000W. The DC converter 3 operates in a constant DC voltage mode, controlling V3=750V.

[0110] To verify that the line-to-line DC power flow controller can solve the line congestion problem, it is assumed that the maximum transmission current in each line is 8.5A. Before adding the line-to-line DC power flow controller, the theoretical analysis shows that the line l 23 At the same time, the capacitor voltage of the line-to-line DC power flow controller will be detected, and by comparing its voltage with the transmission system voltage, it can be determined whether it has the characteristics of small capacity.

[0111] Set line l 13 The reference current is 7.5A, and an inductive line-to-line DC power flow controller is added at 5s to optimize the power flow control.

[0112] from Figure 13 It can be seen from the figure that after adding the inductive line DC power flow controller, the line l 23 The current is reduced to below 8.5A, solving the problem of line congestion.

[0113] from Figure 14 It can be seen from the figure that the capacitor voltage level of the inductive line-to-line DC power flow controller is much lower than the voltage of the three-terminal ring network DC transmission system, and has the characteristic of small capacity.

[0114] from Figure 15It can be seen from the figure that before and after the addition of the inductive line-to-line DC power flow controller, the DC voltage at ports 1 and 2 of the PV-storage DC-flexible microgrid is basically stable, and the three-terminal ring network DC transmission system can operate stably.

[0115] Example 4 is the fourth embodiment of the present invention, which differs from the first three embodiments in that:

[0116] If the functions are implemented in the form of software functional units and sold or used as independent products, they 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 the 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 execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0117] The logic and / or steps represented in the flowcharts or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing the logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (e.g., a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device). For purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0118] More specific examples (a non-exhaustive list) of computer-readable media include the following: an electrical connection with one or more wires (electronic devices), a portable computer disk cartridge (magnetic devices), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disc read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering, or processing in another suitable manner as necessary, and then stored in a computer memory.

[0119] It should be understood that various parts of the present invention can be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0120] Example 5 is the fifth embodiment of the present invention. This embodiment provides a photovoltaic, energy storage, direct current, and flexible microgrid system control system, including a microgrid design module for acquiring power system equipment data and constructing multiple photovoltaic, energy storage, direct current, and flexible microgrid systems; the photovoltaic, energy storage, direct current, and flexible microgrid system includes a photovoltaic module, an energy storage module, a load module, a line module, and a DC grid module;

[0121] The control module is used to connect the line-to-line DC power flow controller in series with the line modules of each photovoltaic, storage, direct and flexible microgrid system. The line-to-line DC power flow controller includes a connection unit and an energy hub. The connection unit is connected in series between each line to adjust the DC voltage drop of each line and control the power flow. The energy hub is used to distribute power to each photovoltaic, storage, direct and flexible microgrid system.

[0122] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A control method for a photovoltaic-storage direct-flexible microgrid system, characterized by: This includes acquiring power system equipment data and building multiple PV-storage-direct-flexible microgrid systems; The photovoltaic storage direct current flexible microgrid system includes a photovoltaic module, an energy storage module, a load module, a line module and a DC grid module; Connecting the line-to-line DC power flow controller in series to the line modules of each solar-storage-direct-flexible microgrid system, wherein the line-to-line DC power flow controller includes a connection unit and an energy hub; The connection unit is connected in series between each line to adjust the DC voltage drop of each line and control the power flow; The energy hub is used to distribute power to each photovoltaic, storage, direct-flexible microgrid system.

2. The control method of a PV-storage direct-flexible microgrid system according to claim 1, characterized in that: The line-to-line DC power flow controller is connected in series to the line modules of each photovoltaic-storage-direct-flexible microgrid system. The line-to-line DC power flow controller includes a connection unit and an energy hub, including: The energy center of the line-to-line DC power flow controller includes an inductive topology energy center or a capacitive topology energy center; The connection unit or energy center is used to connect the capacitor in series to each photovoltaic storage direct-flexible microgrid system, and the amplitude of the equivalent direct current voltage source is controlled by controlling the positive and negative control of the connected capacitor voltage to perform energy flow and power regulation.

3. The control method of a PV-storage direct-flexible microgrid system according to claim 2, characterized in that: The line-to-line DC power flow controller is connected in series to the line modules of each photovoltaic-storage-direct-flexible microgrid system. The line-to-line DC power flow controller includes a connection unit and an energy hub, including: The energy center of the line-to-line DC power flow controller includes an inductive topology energy center or a capacitive topology energy center; The connection unit or energy center is used to connect the capacitor in series to each photovoltaic storage direct-flexible microgrid system, and the amplitude of the equivalent direct current voltage source is controlled by controlling the positive and negative control of the connected capacitor voltage to perform energy flow and power regulation.

4. The control method of a PV-storage direct-flexible microgrid system according to claim 3, characterized in that: Inductive topology energy center, including: When the energy hub adopts an inductive topology, the connection units connected in series between the lines contain capacitors. The capacitors are connected in series to the PV-storage-direct-flexible microgrid system through different switching modes of the connection units. The inductive topology energy hub includes four working modes. Mode 1: When the capacitor voltage is negative, the inductor in the inductive topology energy hub transfers energy to the solar-storage direct-flexible microgrid system; Mode 2: When the capacitor voltage is positive, the PV-storage direct-flexible microgrid system transfers energy through the capacitor to the inductor in the inductive topology energy hub; Mode 3: When the inductive topology energy center is bypassed, the power flow is affected by the capacitor voltage of the connection unit in the line module of the solar-storage direct-flexible microgrid system; Mode 4: Bypass the energy center and connection unit at the same time, and the flow is uncontrollable.

5. The control method of a PV-storage direct-flexible microgrid system according to claim 4, characterized in that: Capacitive topology energy center, including: When the energy hub is a capacitive topology, a certain line is selected to connect to the energy hub through the switch state of the connection unit, and the positive and negative voltage of the capacitor are selected through the switch to perform energy exchange. The capacitive topology energy hub includes three working modes; Mode 1: The capacitor is connected to the PV-storage-direct-flexible microgrid system with a positive voltage, and the corresponding PV-storage-direct-flexible microgrid system line power flow is reduced; Mode 2: The capacitor is connected to the PV-storage-direct-flexible microgrid system with a negative voltage, and the corresponding PV-storage-direct-flexible microgrid system line power flow increases; Mode 3: The capacitor of the bypass capacitor topology energy center has uncontrollable current.

6. The control method of a PV-storage direct-flexible microgrid system according to claim 4, characterized in that: Photovoltaic modules, including: The photovoltaic modules are connected to the DC bus through a boost converter; The maximum power point tracking algorithm based on the fixed-step perturbation-observation control strategy enables the photovoltaic module to achieve maximum power output.

7. The control method of a PV-storage direct-flexible microgrid system according to claim 4, characterized in that: Energy storage module, including: The energy storage module is connected to the DC bus through a bidirectional buck-boost converter, and the DC bus voltage is controlled by a double closed-loop control strategy of voltage outer loop and current inner loop.

8. A photovoltaic, storage, direct-flexible microgrid system control system, applying a photovoltaic, storage, direct-flexible microgrid system control method according to any one of claims 1 to 7, characterized in that: It includes: a microgrid design module for acquiring power system equipment data and constructing multiple photovoltaic, energy storage, direct current and flexible microgrid systems; the photovoltaic, energy storage, direct current and flexible microgrid systems include photovoltaic modules, energy storage modules, load modules, line modules and DC grid modules; The control module is used to connect the line-to-line DC power flow controller in series with the line modules of each photovoltaic, storage, direct and flexible microgrid system. The line-to-line DC power flow controller includes a connection unit and an energy center; the connection unit is connected in series between each line to adjust the DC voltage drop of each line and control the power flow; and the energy center is used to distribute power to each photovoltaic, storage, direct and flexible microgrid system.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of a control method of a photovoltaic-storage-direct-flexible microgrid system according to any one of claims 1 to 7 are implemented.

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 a control method of a photovoltaic-storage-direct-flexible microgrid system according to any one of claims 1 to 7 are implemented.

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