Unplanned Microgrid Grid-Connected and Islanded Mode Switching Method, Energy Management System and Storage Medium

Abstract

The present invention provides an unplanned microgrid grid-connected and islanded switching method, an energy management system and a storage medium. The method includes: monitoring the mains power supply in real time; when detecting a mains power outage, controlling each energy storage converter to stop operating and controlling the first contactor to disconnect; then controlling each energy storage converter to switch from the PQ mode to the VSG mode; and controlling each energy storage converter to start in parallel in the VSG mode. Through the above solution, the present application can timely perform grid-connected and islanded switching on all energy storage converters when detecting a mains power outage, thereby ensuring the stable operation of the microgrid system.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic grid connection, and particularly to an unplanned microgrid parallel-offgrid switching method, an energy management system and a storage medium. Background Technique

[0002] The PCS (Power Conversion System, energy storage converter) has two working modes, grid-connected mode and off-grid mode. When the power grid is normal, the PCS and the power grid jointly supply power to the load. When the power grid is abnormal, the PCS disconnects from the power grid and operates independently to supply power to the load alone. When operating in grid-connected mode, the PCS adopts grid-connected mode PQ control, equivalent to a current source, and outputs power under the condition of following the grid voltage and frequency. When operating in off-grid mode, the PCS adopts off-grid mode VF control, equivalent to a voltage source, and ensures the load power while providing voltage and frequency support for the load.

[0003] The PCS cannot randomly switch the working mode during operation. If the mains power is abnormal during grid-connected operation and the PCS fails to detect the fault in time and does not switch to off-grid working mode, it will report a fault and shut down. At this time, the load may lose power. If the PCS supplies power to the load alone during off-grid operation, it is required that the load must be disconnected from the power grid. Otherwise, when the mains power comes, if the output voltage of the PCS and the mains voltage are connected together with different phase amplitudes, the equipment will be damaged. Summary of the Invention

[0004] In view of this, the present invention provides an unplanned microgrid parallel-offgrid switching method, an energy management system and a storage medium, which can solve the problem of untimely parallel-offgrid switching of the microgrid system caused by unplanned power outages.

[0005] In a first aspect, an embodiment of the present invention provides an unplanned microgrid parallel-offgrid switching method, which is applied to a microgrid system. The microgrid system includes a first contactor, at least one photovoltaic energy storage device and at least one energy storage converter; and the photovoltaic energy storage device and the energy storage converter correspond to each other one by one;

[0006] The first contactor is connected between the mains power and the first busbar. The first busbar is connected to the photovoltaic energy storage busbar. The photovoltaic energy storage busbar is respectively connected to each energy storage converter. Each energy storage converter is respectively connected to the corresponding photovoltaic energy storage device. The first busbar is also used to connect the load;

[0007] The method includes:

[0008] Monitor the mains power in real time;

[0009] If the mains power outage is detected, control each energy storage converter to stop and control the first contactor to disconnect;

[0010] Control each energy storage converter to switch from the PQ mode to the VSG mode; and control each energy storage converter to start in parallel in the VSG mode.

[0011] In a second aspect, an embodiment of the present invention provides an energy management system, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method according to any possible implementation manner of the first aspect above are implemented.

[0012] In a third aspect, an embodiment of the present invention provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the steps of the method according to any possible implementation manner of the first aspect above are implemented.

[0013] The beneficial effects of the embodiments of the present invention compared with the prior art are as follows:

[0014] In the embodiments of the present invention, by monitoring the mains power supply in real time; when it is detected that the mains power supply is cut off, each energy storage converter can be controlled to stop, and the first contactor can be controlled to disconnect; then each energy storage converter is controlled to switch from the PQ mode to the VSG mode; and each energy storage converter is controlled to start in parallel in the VSG mode. Through the above solution, this embodiment can timely perform grid-connected and off-grid switching on all energy storage converters when it is detected that the mains power supply is cut off, thereby ensuring the stable operation of the microgrid system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0016] Figure 1 It is an application scenario diagram of the unplanned microgrid grid-connected and off-grid switching method provided by the embodiments of the present invention;

[0017] Figure 2 It is an implementation flowchart of the unplanned microgrid grid-connected and off-grid switching method provided by the embodiments of the present invention;

[0018] Figure 3 It is an implementation flowchart of the grid-connected to off-grid conversion of the microgrid system provided by the embodiments of the present invention;

[0019] Figure 4 It is an implementation flowchart of the off-grid to grid-connected conversion of the microgrid system provided by the embodiments of the present invention;

[0020] Figure 5It is a schematic structural diagram of an unplanned microgrid parallel and off-grid switching device provided by an embodiment of the present invention;

[0021] Figure 6 It is a schematic diagram of an energy management system provided by an embodiment of the present invention. Specific embodiments

[0022] In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present invention. However, those skilled in the art should clearly understand that the present invention can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present invention.

[0023] To make the purpose, technical solution, and advantages of the present invention clearer, the following will be illustrated through specific embodiments in conjunction with the accompanying drawings.

[0024] Figure 1 It is a circuit diagram of a microgrid system provided by an embodiment of the present invention. As Figure 1 shown, the microgrid system includes a first contactor K1, at least one photovoltaic energy storage device, and at least one energy storage converter PCS; and the photovoltaic energy storage devices and the energy storage converters are in one-to-one correspondence;

[0025] The first contactor K1 is connected between the mains power and the first bus, the first bus is connected to the photovoltaic energy storage bus, the photovoltaic energy storage bus is respectively connected to each energy storage converter PCS, each energy storage converter PCS is respectively connected to the corresponding photovoltaic energy storage device, and the first bus is also used to connect a load.

[0026] In this embodiment, the first bus can be an emergency bus with a continuous power supply requirement.

[0027] As Figure 2 shown, Figure 2 shows the implementation process of the unplanned microgrid parallel and off-grid switching method provided by this embodiment, and the process is described in detail as follows:

[0028] S101: Monitor the mains power in real time;

[0029] S102: If the mains power outage is detected, control each energy storage converter to stop, and control the first contactor to disconnect;

[0030] S103: Control each energy storage converter to switch from the PQ mode to the VSG mode; and control each energy storage converter to start in parallel in the VSG mode.

[0031] The execution entity of this embodiment can be an energy management system (EMS). Through the EMS, unified control of various devices in the microgrid system can be achieved.

[0032] Specifically, the EMS uses a power monitoring device to continuously monitor whether the mains power supply is normal. If the mains power supply suddenly fails, each power conversion system (PCS) of the energy storage will immediately enter the islanding protection state. At this time, the microgrid system needs to switch from the grid-connected state to the off-grid state. During the process of switching from the grid-connected state to the off-grid state, the EMS first controls the first contactor K1 to open. After disconnecting the first contactor K1, in the prior art, the controller of the energy storage converter itself usually directly switches from the PQ mode to the VF mode and then starts. When there are multiple energy storage converters, it is difficult to implement the above process. In this embodiment, in order to start multiple energy storage converters in parallel in the off-grid state, the energy storage converters are switched from the PQ control mode in the grid-connected state to the virtual synchronous generator (VSG) control mode, and then multiple energy storage converters PCS are started in parallel in the VSG mode.

[0033] Through the above process, this embodiment can achieve the grid-connected to off-grid process of the microgrid system with multiple energy storage converters when the mains power supply fails unexpectedly.

[0034] As can be seen from the above embodiments, the embodiments of the present invention continuously monitor the mains power supply; when detecting a power outage of the mains power supply, control each energy storage converter to stop and control the first contactor to open; then control each energy storage converter to switch from the PQ mode to the VSG mode; and control each energy storage converter to start in parallel in the VSG mode. Through the above solution, this embodiment can timely perform grid-connected to off-grid switching on all energy storage converters when detecting a power outage of the mains power supply, thus ensuring the stable operation of the microgrid system.

[0035] In one embodiment, the specific implementation process of S103 includes:

[0036] Control any one of the energy storage converters to start, and after this energy storage converter starts, control the other energy storage converters except this one to start, so that the other energy storage converters except this one are started in parallel with this energy storage converter.

[0037] In this embodiment, controlling all energy storage converters to start in parallel means making the output voltages, frequencies, and phases of all energy storage converters consistent.

[0038] In one embodiment, the specific implementation process of S102 includes:

[0039] If it is detected that each energy storage converter enters the islanding protection state after a power outage of the mains power supply, then control each energy storage converter to stop.

[0040] In this embodiment, when the existing energy storage converter detects a power outage of the main power supply, it will automatically switch to the island protection state. After the energy management system in this embodiment detects a power outage of the main power supply and the energy storage converter enters the island protection state, it controls each energy storage converter to shut down.

[0041] In one embodiment, the microgrid system includes a photovoltaic power generation device and a photovoltaic inverter INV. The photovoltaic power generation device is connected to the photovoltaic energy storage bus through the photovoltaic inverter INV.

[0042] After S103, the method provided in this embodiment further includes:

[0043] Control the photovoltaic inverter to start so that the photovoltaic inverter is paralleled with all energy storage converters.

[0044] In this embodiment, after the energy management system detects that all energy storage converters have started, it controls the photovoltaic inverter to start. After starting, the photovoltaic inverter controls its own output power to gradually increase from zero until the output voltage, frequency, and phase of the photovoltaic inverter are consistent with those of all energy storage converters, realizing the paralleling process with all energy storage converters.

[0045] In one embodiment, after controlling the photovoltaic inverter to start, the method provided in this embodiment further includes:

[0046] Monitor the remaining power of the photovoltaic energy storage device;

[0047] If the remaining power of the photovoltaic energy storage device is greater than the first preset threshold, switch the control right of the photovoltaic inverter to the first control right, and determine the output power of the photovoltaic inverter according to the remaining power of the photovoltaic energy storage device under the first control right, and the remaining power and the output power of the photovoltaic inverter are in an inverse proportion relationship;

[0048] If the remaining power of the photovoltaic energy storage device is less than the first preset threshold, switch the control right of the photovoltaic inverter to the second control right, and send a self-operation instruction to the photovoltaic inverter under the second control right to enable the photovoltaic inverter to control its own operation state.

[0049] In this embodiment, after the microgrid system switches from grid-connected to off-grid, the energy management system determines who the controller of the photovoltaic inverter belongs to according to the size of the remaining power of the photovoltaic energy storage device.

[0050] Specifically, the first preset threshold can be 80%. If the remaining battery power (State Of Charge, SOC) is less than the first preset threshold, the control right of the photovoltaic inverter is the second control right. Under the second control right, the photovoltaic inverter decides how to control its own operating state by itself. Usually, the photovoltaic inverter operates in the Maximum Power Point Tracking (MPPT) mode. If the remaining battery power is greater than or equal to the first preset threshold, the control right of the photovoltaic inverter is the first control right, that is, the control right lies with the energy management system. At this time, the energy management system linearly controls the output power of the photovoltaic inverter according to the remaining battery power of the photovoltaic energy storage device. The more the remaining battery power, the less the output power of the photovoltaic inverter. Thus, when the remaining battery power of the photovoltaic energy storage device is relatively large, the photovoltaic energy storage device is preferentially used to supply power to the load.

[0051] Through the above process, this embodiment can, based on the remaining battery power of the photovoltaic energy storage device, coordinate the energy flow of the entire microgrid system through the energy management system, thereby improving the energy utilization rate of the microgrid system.

[0052] In one embodiment, the microgrid system further includes a second contactor, a third contactor, and a first generator set; the first generator set is a generator set that generates electricity using other energy sources except for photovoltaic power generation;

[0053] The second contactor is connected between the photovoltaic energy storage bus and the first bus;

[0054] The first generator set is connected to the first bus through the third contactor;

[0055] The method provided in this embodiment further includes:

[0056] If the remaining battery power of the photovoltaic energy storage device is less than the second preset threshold, control the second contactor to disconnect;

[0057] Control the first generator set to start, and close the third contactor after monitoring that the first generator set has started;

[0058] If the remaining battery power of the photovoltaic energy storage device is greater than the third preset threshold, control the third contactor to disconnect, the first generator set to stop, and the second contactor to close in sequence;

[0059] The third preset threshold is greater than the second preset threshold and less than the first preset threshold.

[0060] In this embodiment, the first generator set can be a diesel generator set, a gas generator set, or other energy generator sets except for photovoltaic power generation.

[0061] Specifically, the second preset threshold may be 20%, and the third preset threshold may be 50%.

[0062] In one embodiment, after S103, the method provided in this embodiment further includes a control process for the grid-connected power generation system to switch from off-grid to grid-connected after the mains power is restored, which is described in detail as follows:

[0063] S104: If it is detected that the mains power is restored, control the first contactor to close, and control each energy storage converter to switch from the VSG mode to the PQ mode.

[0064] In this embodiment, when it is detected that the mains power is restored, first control the first contactor K1 to close, and then control each energy storage converter PCS to switch from the VSG mode to the PQ mode.

[0065] In one embodiment, the specific implementation process of S104 includes:

[0066] If it is detected that the mains power is restored, perform synchronization control on each energy storage converter and the mains power;

[0067] Control the first contactor to close, and control each energy storage converter to switch from the VSG mode to the PQ mode.

[0068] Specifically, if the microgrid system includes a photovoltaic power generation device and a photovoltaic inverter, after the energy management system detects that the mains power is restored, it controls each energy storage converter and the photovoltaic inverter to be synchronized with the mains power.

[0069] Specifically, synchronization control is to control the voltage, frequency, and phase of the photovoltaic inverter and the energy storage converter to be consistent with the power grid.

[0070] In one embodiment, the microgrid system further includes a second contactor, a third contactor, and a first generator set; the first generator set is a generator set that generates electricity using other energy sources except for photovoltaic;

[0071] The second contactor is connected between the photovoltaic and energy storage bus and the first bus; the first generator set is connected to the first bus through the third contactor.

[0072] In this embodiment, if the microgrid system includes a first generator set, it is necessary to check the current operating state of the microgrid system in the off-grid mode when it is detected that the mains power is restored, determine whether the first generator set or the photovoltaic power generation device is working currently, and adopt different off-grid to grid-connected processes according to different operating states. Specifically, the specific implementation process of S104 includes:

[0073] If it is detected that the mains power is restored and the second contactor is in the closed state while the third contactor is in the open state, control the first contactor to close and control each energy storage converter to switch from the VSG mode to the PQ mode;

[0074] If it is detected that the mains power is restored and the second contactor is in the open state while the third contactor is in the closed state, control the third contactor to open and then control the first contactor to close;

[0075] Control the photovoltaic inverter and each energy storage converter to stop and switch each energy storage converter to the PQ mode;

[0076] Control the second contactor to close and start each energy storage converter and the photovoltaic inverter so that the microgrid system enters the grid-connected operation mode.

[0077] As Figure 3 shown, as a specific application scenario of this embodiment, this embodiment provides an implementation process for the grid-connected to off-grid conversion of a microgrid system, and the process is described in detail as follows:

[0078] S1: If the energy management system detects a mains power outage, jump to S2;

[0079] S2: After detecting a mains power outage, the photovoltaic inverter and the energy storage converters automatically enter the islanding protection state, and jump to S3;

[0080] S3: The energy management system controls the first contactor K1 to open, and jump to S3;

[0081] S4: The energy management system controls all energy storage converters to switch to the VSG mode and start, and jump to S5;

[0082] S5: The energy management system controls the photovoltaic inverter INV to start, and jump to S6;

[0083] S6: The energy management system determines whether the SOC of the photovoltaic energy storage device is less than 10%. If it is less, jump to S7, otherwise jump to S9;

[0084] S7: The energy management system controls all energy storage converters to stop, and jump to S8;

[0085] S8: Transfer to black start.

[0086] S9: The energy management system determines whether the SOC of the photovoltaic energy storage device is less than 20%. If it is less, jump to S10, otherwise jump to S17;

[0087] S10: The energy management system disconnects the second contactor K2, and jump to S11;

[0088] S11: The energy management system controls the first generating unit to start, and after detecting that the first generating unit has started, it jumps to S12;

[0089] S12: The energy management system controls the third contactor K3 to close, and jumps to S13;

[0090] S13: The energy management system determines whether the SOC of the photovoltaic energy storage device is greater than 50%. If it is greater, it jumps to S14; otherwise, it jumps to S6;

[0091] S14: The energy management system disconnects the third contactor K3 and jumps to S15;

[0092] S15: The energy management system controls the first generating unit to shut down and jumps to S16;

[0093] S16: The energy management system closes the second contactor K2 and jumps to S19;

[0094] S17: The energy management system determines whether the SOC of the photovoltaic energy storage device is less than 25%. If it is less, it jumps to S18; otherwise, it jumps to S19;

[0095] S18: The energy management system issues an audible and visual alarm signal;

[0096] S19: The energy management system determines whether the SOC of the photovoltaic energy storage device is less than 80%. If it is less, it jumps to S20; otherwise, it jumps to S21;

[0097] S20: Switch the control right to the second control right, and the photovoltaic inverter controls its own operating state by itself;

[0098] S21: Switch the control right to the first control right, and the energy management system controls the output power of the photovoltaic inverter according to the SOC of the photovoltaic energy storage device under the first control right.

[0099] In an embodiment of the present invention, the off-grid to grid-connected process of the microgrid system is as follows:

[0100] S01: If the energy management system detects that the mains power is restored, it jumps to S02;

[0101] S02: The energy management system determines whether the current operating state is K2 closed and K3 disconnected. If it is, it jumps to S04; if not, it jumps to S03;

[0102] S03: The energy management system determines whether the current operating state is K3 closed and K2 disconnected. If it is, it jumps to S09;

[0103] S04: The energy management system controls the PCS and INV to be synchronized with the grid through the synchronization controller, and jumps to S05;

[0104] S05: The energy management system determines whether synchronization is completed. If so, it jumps to S06; otherwise, it jumps to S04.

[0105] S06: The energy management system controls the first contactor K1 to close and jumps to S07.

[0106] S07: The energy management system controls each PCS to switch from the VSG mode to the PQ mode and jumps to S08.

[0107] S08: Enter the grid-connected operation mode.

[0108] S09: The energy management system controls the third contactor K3 to open and jumps to S010.

[0109] S010: The energy management system controls the first contactor K1 to close and jumps to S011.

[0110] S011: The energy management system turns off the INV and PCS, controls the PCS to switch to the PQ mode, and jumps to S012.

[0111] S012: The energy management system controls the second contactor K2 to close and jumps to S013.

[0112] S013: The energy management system turns on the PCS and INV and jumps to S08.

[0113] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0114] The following is an embodiment of the device of the present invention. For the details not described in detail, reference can be made to the corresponding method embodiments above.

[0115] Figure 5 The structure diagram of the unplanned microgrid grid-connected and islanding switching device 100 provided by the embodiment of the present invention is shown, which is applied to a microgrid system. The microgrid system includes a first contactor, at least one photovoltaic energy storage device, and at least one energy storage converter; and the photovoltaic energy storage device and the energy storage converter correspond one by one.

[0116] The first contactor is connected between the mains power and the first bus. The first bus is connected to the photovoltaic energy storage bus. The photovoltaic energy storage bus is respectively connected to each energy storage converter. Each energy storage converter is respectively connected to the corresponding photovoltaic energy storage device. The first bus is also used to connect to a load. For the convenience of description, only the parts related to the embodiments of the present invention are shown in the device provided in this embodiment, and are described in detail as follows:

[0117] The mains power monitoring module 110 is used to monitor the mains power in real time;

[0118] The shutdown module 120 is used to control each energy storage converter to shut down and control the first contactor to disconnect if the mains power outage is detected;

[0119] The off-grid parallel startup module 130 is used to control each energy storage converter to switch from the PQ mode to the VSG mode; and control each energy storage converter to start in parallel in the VSG mode.

[0120] In one embodiment, the off-grid parallel startup module 130 is specifically used for:

[0121] Control any one energy storage converter to start, and after the energy storage converter starts, control the other energy storage converters except this energy storage converter to start, so that the other energy storage converters except this energy storage converter are paralleled with this energy storage converter.

[0122] In one embodiment, the shutdown module 120 is specifically used for:

[0123] If it is detected that each energy storage converter enters the island protection state after the mains power outage, control each energy storage converter to shut down. [[ID=2's0]]

[0124] In one embodiment, the unplanned microgrid parallel-off-grid switching device 100 further includes an off-grid / on-grid switching module, which is used for:

[0125] If the mains power recovery is detected, control the first contactor to close and control each energy storage converter to switch from the VSG mode to the PQ mode.

[0126] In one embodiment, the microgrid system includes a photovoltaic power generation device and a photovoltaic inverter, and the photovoltaic power generation device is connected to the photovoltaic energy storage bus through the photovoltaic inverter;

[0127] The unplanned microgrid parallel-off-grid switching device 100 further includes an inverter parallel module, which is used for:

[0128] Control the photovoltaic inverter to start so that the photovoltaic inverter is paralleled with all energy storage converters.

[0129] In one embodiment, the unplanned microgrid parallel-off-grid switching device 100 further includes a photovoltaic inverter control module, which is used for:

[0130] Monitor the remaining power of the photovoltaic energy storage device;

[0131] If the remaining power of the photovoltaic energy storage device is greater than the first preset threshold, switch the control right of the photovoltaic inverter to the first control right, and determine the output power of the photovoltaic inverter according to the remaining power of the photovoltaic energy storage device under the first control right, and the remaining power and the output power of the photovoltaic inverter are in an inverse proportion relationship;

[0132] If the remaining power of the photovoltaic energy storage device is less than the first preset threshold, switch the control right of the photovoltaic inverter to the second control right, and send a self-operation instruction to the photovoltaic inverter under the second control right to enable the photovoltaic inverter to control its own operation state by itself.

[0133] In one embodiment, the microgrid system further includes a second contactor, a third contactor and a first generator set; the first generator set is a generator set that generates electricity using other energy sources except photovoltaic;

[0134] The second contactor is connected between the photovoltaic energy storage bus and the first bus;

[0135] The first generator set is connected to the first bus through the third contactor;

[0136] The unplanned microgrid grid-connected and off-grid switching device 100 further includes a grid-connected device switching module, which is specifically used for:

[0137] If the remaining power of the photovoltaic energy storage device is less than the second preset threshold, control the second contactor to disconnect;

[0138] Control the first generator set to start, and close the third contactor after monitoring that the first generator set has started;

[0139] If the remaining power of the photovoltaic energy storage device is greater than the third preset threshold, control the third contactor to disconnect, the first generator set to stop, and the second contactor to close in sequence;

[0140] The third preset threshold is greater than the second preset threshold and less than the first preset threshold.

[0141] In one embodiment, the grid-connected and off-grid switching module specifically includes:

[0142] If it is monitored that the mains power is restored, perform synchronization control on each energy storage converter and the mains power;

[0143] Control the first contactor to close, and control each energy storage converter to switch from the VSG mode to the PQ mode.

[0144] Figure 6 It is a schematic diagram of an energy management system provided by an embodiment of the present invention. As Figure 6As shown, the energy management system 6 of this embodiment includes: a processor 60, a memory 61, and a computer program 62 stored in the memory 61 and executable on the processor 60. When the processor 60 executes the computer program 62, the steps in the above-mentioned embodiments of the unplanned microgrid connection and disconnection switching method are implemented, such as Figure 2 the steps 101 to 103 shown. Alternatively, when the processor 60 executes the computer program 62, the functions of each module / unit in the above-mentioned device embodiments are implemented, such as Figure 5 the functions of the units 110 to 130 shown.

[0145] Exemplarily, the computer program 62 can be divided into one or more modules / units. The one or more modules / units are stored in the memory 61 and executed by the processor 60 to complete the present invention. The one or more modules / units can be a series of computer program instruction segments capable of performing specific functions, and these instruction segments are used to describe the execution process of the computer program 62 in the energy management system 6.

[0146] The energy management system 6 may include, but is not limited to, a processor 60 and a memory 61. Those skilled in the art can understand that Figure 6 this is only an example of the energy management system 6 and does not constitute a limitation on the energy management system 6. It may include more or fewer components than shown in the figure, or combine certain components, or different components. For example, the energy management system may further include input / output devices, network access devices, buses, etc.

[0147] The so-called processor 60 may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0148] The memory 61 may be an internal storage unit of the energy management system 6, such as a hard disk or memory of the energy management system 6. The memory 61 may also be an external storage device of the energy management system 6, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. equipped on the energy management system 6. Further, the memory 61 may also include both an internal storage unit of the energy management system 6 and an external storage device. The memory 61 is used to store the computer program and other programs and data required by the energy management system. The memory 61 may also be used to temporarily store the data that has been output or will be output.

[0149] Those skilled in the art can clearly understand that for the convenience and brevity of description, only the above division of each functional unit and module is used as an example. In actual applications, the above functions can be allocated to different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit. In addition, the specific names of each functional unit and module are only for the convenience of mutual distinction and do not limit the protection scope of the present application. The specific working processes of the units and modules in the above system can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0150] In the above embodiments, the descriptions of each embodiment have their own emphases. For the parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0151] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or by the combination of computer software and electronic hardware. Whether these functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0152] In the embodiments provided by the present invention, it should be understood that the disclosed device / energy management system and method can be implemented in other ways. For example, the device / energy management system embodiments described above are merely illustrative. For example, the division of the modules or units is only a logical function division. In actual implementation, there may be other division methods. 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 displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces. The indirect couplings or communication connections of the devices or units can be in electrical, mechanical or other forms.

[0153] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0154] In addition, in each embodiment of the present invention, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above integrated units can be implemented in the form of hardware or in the form of software functional units.

[0155] If the integrated module / 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, to implement all or part of the processes in the above method embodiments, it can also be completed by a computer program instructing the relevant hardware. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above embodiments of the unplanned microgrid connection and disconnection switching method can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file or some intermediate form, etc. The computer-readable medium can include: any entity or device that can carry the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0156] The above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for unplanned microgrid on-grid and off-grid switching, characterized in that: Applied to a microgrid system, the microgrid system includes a first contactor, at least one photovoltaic energy storage device and at least one energy storage converter; and the photovoltaic energy storage device and the energy storage converter correspond one to one; The first contactor is connected between the mains and the first busbar, the first busbar is connected to the photovoltaic energy storage busbar, the photovoltaic energy storage busbar is connected to each energy storage converter, each energy storage converter is connected to a corresponding photovoltaic energy storage device, and the first busbar is also used to connect a load; The method comprises: Real-time monitoring of mains electricity; If a mains power outage is detected, each energy storage converter is controlled to shut down, and the first contactor is controlled to disconnect; Control each energy storage converter to switch from PQ mode to VSG mode; and control each energy storage converter to start in parallel under VSG mode; The microgrid system includes a photovoltaic power generation device and a photovoltaic inverter, and the photovoltaic power generation device is connected to the photovoltaic storage bus through the photovoltaic inverter; After controlling each energy storage converter to start in parallel in the VSG mode, the method further includes: Controlling the photovoltaic inverter to start up so that the photovoltaic inverter and all energy storage converters are connected in parallel; After controlling the photovoltaic inverter to start, the method further includes: monitoring the remaining power of the photovoltaic energy storage device; When the photovoltaic inverter supplies power to the load, if the remaining power of the photovoltaic energy storage device is greater than a first preset threshold, the control right of the photovoltaic inverter is switched to the first control right, and under the first control right, the output power of the photovoltaic inverter is determined according to the remaining power of the photovoltaic energy storage device, and the remaining power is inversely proportional to the output power of the photovoltaic inverter; If the remaining power of the photovoltaic energy storage device is less than the first preset threshold, the control right of the photovoltaic inverter is switched to the second control right, and a self-operation instruction is sent to the photovoltaic inverter under the second control right, so that the photovoltaic inverter controls the operating state by itself.

2. The unplanned microgrid on-grid and off-grid switching method according to claim 1, characterized in that: The controlling of the energy storage converters to start in parallel in the VSG mode includes: Control any energy storage converter to start, and after the energy storage converter is started, control other energy storage converters except the energy storage converter to start, so that the other energy storage converters except the energy storage converter are connected in parallel with the energy storage converter.

3. The unplanned microgrid on-grid and off-grid switching method according to claim 1, characterized in that: If a mains power outage is detected, each energy storage converter is controlled to shut down, including: If it is detected that each energy storage converter enters the island protection state after the mains power outage, each energy storage converter is controlled to shut down.

4. The unplanned microgrid on-grid and off-grid switching method according to claim 1, characterized in that: After controlling each energy storage converter to start in parallel in the VSG mode, the method further includes: If it is detected that the mains power is restored, the first contactor is controlled to close, and each energy storage converter is controlled to switch from the VSG mode to the PQ mode.

5. The unplanned microgrid on-grid and off-grid switching method according to any one of claims 1 to 4, characterized in that: The microgrid system further includes a second contactor, a third contactor and a first generator set; the first generator set is a generator set that generates electricity using energy other than photovoltaics; The second contactor is connected between the solar storage bus and the first bus; The first generator set is connected to the first busbar via the third contactor; The method further comprises: If the remaining power of the photovoltaic energy storage device is less than a second preset threshold, controlling the second contactor to disconnect; controlling the first generator set to start, and closing the third contactor after monitoring the start of the first generator set; If the remaining power of the photovoltaic energy storage device is greater than a third preset threshold, the third contactor is controlled to be disconnected, the first generator set is stopped, and the second contactor is closed in sequence; The third preset threshold is greater than the second preset threshold and less than the first preset threshold.

6. The unplanned microgrid on-grid and off-grid switching method according to claim 4, characterized in that: If the mains power is restored, the first contactor is controlled to close, and each energy storage converter is controlled to switch from the VSG mode to the PQ mode, including: If it is detected that the mains power is restored, each energy storage converter is synchronously controlled with the mains power; The first contactor is controlled to close, and each energy storage converter is controlled to switch from the VSG mode to the PQ mode.

7. An energy management system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

8. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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