Method, system, device and medium for planned on-grid and off-grid switching of photovoltaic and energy storage microgrid

Abstract

The present invention relates to the technical field of grid-connected photovoltaic storage microgrids, and in particular to a method, system, device and medium for planned on-grid and off-grid switching of photovoltaic storage microgrids. By designing a planned on-grid and off-grid switching method of photovoltaic storage microgrids, when the upstream of a PCC point needs to be disconnected due to planned maintenance, the microgrid can have two modes of on-grid operation at a connecting switch and off-grid autonomous operation. In the on-grid and off-grid switching method, it is decided whether the microgrid is off-grid or on-grid at a connecting point by repeatedly checking whether the parallel operation conditions are met, thereby improving the operational reliability of the microgrid. When it is detected that the conditions are not met, the system can automatically switch to the corresponding operation mode, thereby improving the operational flexibility of the microgrid, enabling it to automatically select the most suitable operation mode according to actual conditions, and ensuring the stable operation of the microgrid.

Description

Technical Field

[0001] The present invention relates to the technical field of a grid-connected photovoltaic and storage microgrid, and in particular to a method, system, device and medium for planned on-grid and off-grid switching of a photovoltaic and storage microgrid. Background Art

[0002] The large-scale access of distributed photovoltaics in the distribution network brings problems such as reverse overload of distribution transformers and overvoltage at the end of loads to the substation area, affecting the safety of the distribution network and limiting the absorption level of distributed photovoltaics. By rationally arranging distributed energy storage to build a photovoltaic storage microgrid, the energy storage can store the surplus photovoltaic power at noon for the evening load peak, which can alleviate the above problems to a certain extent. At the same time, the photovoltaic storage microgrid has the ability of off-grid autonomy. When there is a fault outside the area, off-grid operation can ensure the reliable power supply of part of the load in the area and improve the reliability of the distribution network.

[0003] However, in the prior art, the system architecture considered when the microgrid switches from grid-connected operation to off-grid operation is relatively simple, which only considers the closing or disconnection of the PCC point, without considering whether there is a tie switch inside the microgrid. When there is a tie switch inside the microgrid, it means that there are two potential grid-side power sources in the microgrid. In addition, after switching from grid-connected to off-grid, energy storage needs to use network control to construct the voltage and frequency inside the microgrid. At this time, if the tie switch, PCC switch, and energy storage network control do not cooperate properly, it will cause the microgrid to have "multi-source network construction", which violates the principle of "closed-loop design, open-loop operation" of the AC distribution network and is prone to cause distribution network oscillation.

[0004] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0005] The present invention provides a method, system, device and medium for planned on-grid and off-grid switching of a photovoltaic storage microgrid, thereby effectively solving the problems in the background technology.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a method for planned on-grid and off-grid switching of a photovoltaic storage microgrid, and a device used in the method for planned on-grid and off-grid switching of a photovoltaic storage microgrid comprises:

[0007] The photovoltaic inverter, energy storage battery management system, energy storage inverter, tie switch, and PCC switch communicate quickly with the microgrid energy management system through optical fiber;

[0008] The photovoltaic inverter, the energy storage battery management system, the energy storage inverter and the microgrid energy management system are in two-way communication, uploading their own operating status to the microgrid energy management system and receiving control instructions from the microgrid energy management system;

[0009] The microgrid energy management system communicates with the distribution automation master station through a gateway, wherein the microgrid energy management system and the gateway are in two-way communication, and the gateway and the distribution automation master station are in two-way communication, uploading the microgrid operation status to the distribution automation master station and forwarding the distribution automation master station control instructions;

[0010] The tie switch and the PCC switch are both automated switches, which use wireless communication with the distribution automation master station for two-way communication, upload their own open and close position status to the distribution automation master station and receive remote control instructions from the distribution automation master station;

[0011] The method comprises:

[0012] S10: The tie switch, PCC switch, microgrid energy management system and distribution automation master station are synchronized, and the energy storage inverter, energy storage battery management system, photovoltaic inverter and microgrid energy management system are synchronized;

[0013] S20: The tie switch and PCC switch upload the local voltage amplitude, frequency and phase to the microgrid energy management system and the distribution automation master station at the same time, and the energy storage inverter uploads the local voltage amplitude, frequency and phase to the microgrid energy management system; at this time, if the microgrid is in the grid-connected operation mode, go to step S30; if the microgrid is in the off-grid operation mode, go to step S50;

[0014] S30: The microgrid energy management system determines whether the tie switch and the PCC switch meet the conditions for parallel operation, and the distribution automation master station determines whether the tie switch and the PCC switch meet the conditions for parallel operation;

[0015] S40: The judgment result of the microgrid energy management system is compared with the judgment result of the distribution automation master station, and the mode is switched according to the comparison result;

[0016] S50: The microgrid energy management system determines whether the tie switch and the energy storage inverter meet the conditions for parallel operation, and the distribution automation master station determines whether the tie switch and the energy storage inverter meet the conditions for parallel operation;

[0017] S60: The judgment result of the microgrid energy management system is compared with the judgment result of the distribution automation master station, and the mode is switched according to the comparison result.

[0018] Furthermore, in step S40, the determination result of the microgrid energy management system is compared with the determination result of the distribution automation master station, specifically including:

[0019] If the judgment results show that both of them meet the conditions for parallel operation, then it is determined that the tie switch and PCC switch meet the conditions for parallel operation;

[0020] If the judgment results are that the conditions for parallel operation are not met, it is determined that the tie switch and PCC switch do not meet the conditions for parallel operation;

[0021] If there is one result that does not meet the parallel operation conditions, go to step S10 for repeated confirmation. When the number of repeated confirmations is greater than N times and there is still one result that does not meet the parallel operation conditions, it is determined that the connecting switch and the PCC switch do not meet the parallel operation conditions, where N is the set confirmation number threshold for jumping out of the repeated confirmation cycle.

[0022] Furthermore, if the determination result is that the tie switch and the PCC switch meet the conditions for parallel operation, the operation mode of the photovoltaic grid-connected inverter and the energy storage grid-connected inverter remains unchanged, and the distribution automation master station first remotely controls the tie switch to close, and then remotely controls the PCC switch to open.

[0023] Furthermore, if the judgment result is that the tie switch and the PCC switch do not meet the conditions for parallel operation, the active output of the photovoltaic grid-connected inverter and the energy storage grid-connected inverter is adjusted and the power flow information of the PCC point is monitored at the same time.

[0024] Furthermore, if the PCC switch power flow is 0±XkW, the photovoltaic grid-connected inverter and the energy storage grid-connected inverter stop power adjustment and the microgrid energy management system sends information to the distribution automation master station to request a planned off-grid operation. The distribution automation master station remotely controls the PCC switch to open, where X is the power difference that will not affect the internal operation of the microgrid during the on-grid and off-grid conversion.

[0025] If the PCC switch power flow is not 0±XkW, part of the photovoltaic power or load will be cut off to make the PCC switch power flow meet 0±XkW.

[0026] Furthermore, in step S60, the determination result of the microgrid energy management system is compared with the determination result of the distribution automation master station, specifically including:

[0027] If the judgment results show that both are in parallel operation condition, it is determined that the tie switch and the energy storage inverter are in parallel operation condition;

[0028] If the judgment results are that the conditions for parallel operation are not met, it is determined that the tie switch and the energy storage inverter do not meet the conditions for parallel operation;

[0029] If there is one result that does not meet the parallel operation conditions, go to step S10 for repeated confirmation. When there is still one result that does not meet the parallel operation conditions after repeated confirmation for more than N times, it is determined that the connecting switch and the energy storage inverter do not meet the parallel operation conditions, where N is the set confirmation number threshold for jumping out of the repeated confirmation cycle.

[0030] Furthermore, if the determination result is that the tie switch and the energy storage inverter meet the conditions for parallel operation, the distribution automation master station remotely controls the tie switch to close.

[0031] Further, if the determination result is that the tie switch and the energy storage inverter do not meet the conditions for parallel operation, the voltage, frequency and phase of the microgrid are adjusted through the energy storage inverter;

[0032] If the power of the energy storage inverter does not exceed the limit, go to step S20;

[0033] If the power of the energy storage inverter reaches the limit, the interconnecting switch and the energy storage inverter cannot be adjusted to parallel operation conditions, and the microgrid remains off-grid.

[0034] The present invention also includes a planned on-grid and off-grid switching system for a photovoltaic storage microgrid, using the above method, including: a time synchronization module, a mode judgment module, a first result comparison switching module, a second result comparison switching module, a first parallel operation condition judgment module, and a second parallel operation condition judgment module;

[0035] Timing module, used for synchronizing the contact switch, PCC switch, microgrid energy management system with the distribution automation master station, energy storage inverter, energy storage battery management system, photovoltaic inverter and microgrid energy management system;

[0036] A mode judgment module is used for the tie switch and the PCC switch to upload the local voltage amplitude, frequency and phase to the microgrid energy management system and the distribution automation master station at the same time, and the energy storage inverter to upload the local voltage amplitude, frequency and phase to the microgrid energy management system; at this time, if the microgrid is in the grid-connected operation mode, it will switch to the first parallel operation condition judgment module; if the microgrid is in the off-grid operation mode, it will switch to the second parallel operation condition judgment module;

[0037] The first parallel operation condition judgment module is used for the microgrid energy management system to judge whether the tie switch and the PCC switch have the parallel operation conditions, and the distribution automation master station judges whether the tie switch and the PCC switch have the parallel operation conditions;

[0038] The first result comparison switching module is used to compare the judgment result of the microgrid energy management system with the judgment result of the distribution automation master station, and perform mode switching according to the comparison result;

[0039] The second parallel operation condition judgment module, the microgrid energy management system judges whether the tie switch and the energy storage inverter meet the parallel operation conditions, and the distribution automation master station judges whether the tie switch and the energy storage inverter meet the parallel operation conditions;

[0040] The second result comparison switching module compares the judgment result of the microgrid energy management system with the judgment result of the distribution automation master station, and switches the mode according to the comparison result.

[0041] The present invention also includes a computer device, including 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 method described above is implemented.

[0042] The present invention also includes a storage medium on which a computer program is stored. When the computer program is executed by a processor, the method described above is implemented.

[0043] The beneficial effects of the present invention are:

[0044] By constructing a communication architecture system, the foundation is laid for executing the on-grid and off-grid switching method. Then, the on-grid and off-grid switching method is executed. When the upstream of the PCC point needs to be disconnected due to planned maintenance, the microgrid can have two modes: on-grid operation at the connecting switch and off-grid autonomous operation. In the method, whether the parallel operation conditions are met is repeatedly checked to decide whether the microgrid is off-grid operation or on-grid operation at the contact point, thereby improving the operation reliability of the microgrid. When it is detected that the conditions are not met, the system can automatically switch to the corresponding operation mode, thereby improving the operation flexibility of the microgrid, enabling it to automatically select the most suitable operation mode according to the actual situation, and ensuring the stable operation of the microgrid. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1 This is the architecture diagram of the planned on-grid and off-grid switching device for the photovoltaic and storage microgrid;

[0047] Figure 2 A flow chart of the planned on-grid and off-grid switching method for a photovoltaic and storage microgrid;

[0048] Figure 3 It is a structural diagram of an implementation case of the present invention;

[0049] Figure 4 This is a schematic diagram of the structure of the planned on-grid and off-grid switching system of the photovoltaic and energy storage microgrid;

[0050] Figure 5 A schematic diagram of the structure of a computer device. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0052] like Figure 1 Shown: A method for planned on-grid and off-grid switching of a photovoltaic and energy storage microgrid.

[0053] The device used in the method for planned on-grid and off-grid switching of the photovoltaic storage microgrid includes:

[0054] The photovoltaic inverter, energy storage battery management system (BMS), energy storage inverter (PCS), tie switch, and PCC switch communicate quickly with the microgrid energy management system (EMS) through optical fiber;

[0055] Among them, the photovoltaic inverter, energy storage battery management system (BMS), energy storage inverter (PCS) and microgrid energy management system (EMS) are two-way communication, uploading their own operating status to the microgrid energy management system (EMS) and receiving the microgrid energy management system (EMS) control instructions; thus achieving efficient management of energy and maximizing the use of photovoltaic power generation and energy storage batteries;

[0056] The microgrid energy management system (EMS) communicates with the distribution automation master station through the gateway. Considering the long distance, wireless communication using base station signals can be used. The microgrid energy management system and the gateway communicate in two directions, and the gateway and the distribution automation master station communicate in two directions. The microgrid operation status is uploaded to the distribution automation master station and the distribution automation master station control instructions are forwarded. Real-time control and monitoring of the microgrid and the entire distribution system are achieved, which helps to respond to changes in the system operation status in a timely manner and improve the robustness and adaptability of the microgrid.

[0057] Both the tie switch and PCC switch are automatic switches, which use wireless communication with the distribution automation master station for two-way communication, upload their own open and close status to the distribution automation master station and receive remote control commands from the distribution automation master station. This increases the flexibility of the system, reduces the complexity of wiring, and improves the convenience of system installation and maintenance;

[0058] As automatic switches, the contact switch and PCC switch realize intelligent control of the system status by uploading their own open and close position status and receiving remote control commands, which helps to improve the system's automation level, reduce manual intervention, and reduce operational risks. Through the application of two-way communication and automatic switches, the system can respond to external commands and adjust the internal status more quickly, which helps to improve the system's reliability, reduce the possibility of failures, optimize energy management, improve the system's real-time performance and flexibility, enhance the system's automation and reliability, and ensure the stable operation of the microgrid during the off-grid and grid-connected process.

[0059] like Figure 2 As shown, the above method includes:

[0060] S10: The interconnecting switch, PCC switch, microgrid energy management system (EMS) and distribution automation master station are synchronized, and the energy storage inverter (PCS), energy storage battery management system (BMS), photovoltaic inverter and microgrid energy management system (EMS) are synchronized; through the synchronization operation, it can be ensured that all components operate based on the same time reference to avoid errors and mismatches caused by time differences, and to ensure the consistency of real-time data and control signals of each component during operation.

[0061] S20: The tie switch and PCC switch upload the local voltage amplitude, frequency and phase to the microgrid energy management system (EMS) and the distribution automation master station at the same time, and the energy storage inverter (PCS) uploads the local voltage amplitude, frequency and phase to the microgrid energy management system (EMS); it is used to monitor the operation status and load demand of the microgrid so as to perform corresponding control and adjustment. At this time, if the microgrid is in the grid-connected operation mode, it goes to step S30; if the microgrid is in the off-grid operation mode, it goes to step S50;

[0062] S30: The microgrid energy management system (EMS) determines whether the tie switch and the PCC switch meet the conditions for parallel operation, and the distribution automation master station determines whether the tie switch and the PCC switch meet the conditions for parallel operation;

[0063] S40: The judgment result of the microgrid energy management system (EMS) is compared with the judgment result of the distribution automation master station, and the mode is switched according to the comparison result;

[0064] S50: The microgrid energy management system (EMS) determines whether the tie switch and the energy storage inverter (PCS) are in parallel operation condition, and the distribution automation master station determines whether the tie switch and the energy storage inverter (PCS) are in parallel operation condition;

[0065] S60: The judgment result of the microgrid energy management system (EMS) is compared with the judgment result of the distribution automation master station, and the mode is switched according to the comparison result.

[0066] By designing an on-grid and off-grid switching method, when the upstream of the PCC point needs to be disconnected due to planned maintenance, the microgrid can have two modes: on-grid operation at the connecting switch and off-grid autonomous operation. In this method, the decision is made whether the microgrid should operate off-grid or on-grid at the contact point by repeatedly checking whether the parallel operation conditions are met, which improves the operation reliability of the microgrid. When it is detected that the conditions are not met, the system can automatically switch to the corresponding operation mode, which improves the operation flexibility of the microgrid and enables it to automatically select the most suitable operation mode according to the actual situation to ensure the stable operation of the microgrid.

[0067] As a preferred embodiment of the above, in step S40, the judgment result of the microgrid energy management system (EMS) is compared with the judgment result of the distribution automation master station, specifically including:

[0068] If the judgment results show that both of them meet the conditions for parallel operation, then it is determined that the tie switch and PCC switch meet the conditions for parallel operation;

[0069] If the judgment results are that the conditions for parallel operation are not met, it is determined that the tie switch and PCC switch do not meet the conditions for parallel operation;

[0070] If there is one result that does not meet the parallel operation conditions, go to step S10 for repeated confirmation. When the number of repeated confirmations is greater than N times and there is still one result that does not meet the parallel operation conditions, it is determined that the connecting switch and the PCC switch do not meet the parallel operation conditions, where N is the set confirmation number threshold for jumping out of the repeated confirmation cycle.

[0071] The microgrid energy management system (EMS) and the distribution automation master station determine whether the tie switch and PCC switch meet the conditions for parallel operation by comparing the judgment results. This comparison can ensure that the various components in the system can work in coordination during operation to prevent inconsistent or conflicting operations; through repeated confirmation and the set confirmation number threshold, if there is a result that does not meet the conditions for parallel operation, it is determined that the tie switch and PCC switch do not meet the conditions for parallel operation. In this way, problems can be discovered in advance and corresponding measures can be taken to ensure the stability and reliability of the system, effectively improving the reliability, safety and automated operation management of the system.

[0072] As a preferred embodiment of the above, if the judgment result is that the tie switch and the PCC switch meet the conditions for parallel operation, the operation mode of the photovoltaic grid-connected inverter and the energy storage grid-connected inverter (PCS) remains unchanged, and the distribution automation master station first remotely controls the tie switch to close, and then remotely controls the PCC switch to open. After closing, the microgrid is reconnected to the main grid to achieve grid-connected operation, which can ensure seamless switching between the microgrid and the main grid and maintain a stable connection with the external grid.

[0073] In this embodiment, if the determination result is that the tie switch and the PCC switch do not meet the parallel operation conditions, the active output of the photovoltaic grid-connected inverter and the energy storage grid-connected inverter (PCS) is adjusted and the PCC point power flow information is monitored at the same time.

[0074] Among them, if the PCC switch power flow is 0±XkW, the photovoltaic grid-connected inverter and energy storage grid-connected inverter (PCS) stop power adjustment and the microgrid energy management system (EMS) sends information to the distribution automation master station to request a planned off-grid operation. The distribution automation master station remotely controls the PCC switch to open according to the gateway request signal, where X is the power difference that will not affect the internal operation of the microgrid during the set on-grid and off-grid conversion; the microgrid can safely and reliably operate off-grid. This planned off-grid operation ensures that the microgrid has sufficient power supply and energy reserves when operating off-grid, provides a stable power supply, and avoids negative impacts on the internal operation of the microgrid;

[0075] If the PCC switch power flow is not 0±XkW, some photovoltaic or load will be cut off to make the PCC switch power flow meet 0±XkW. The set power difference X can ensure that the off-grid conversion will not affect the internal operation of the microgrid, so that in the off-grid mode, the load demand in the microgrid can be met and the operation status in the microgrid can be kept stable.

[0076] As a preferred embodiment of the above, in step S60, the judgment result of the microgrid energy management system (EMS) is compared with the judgment result of the distribution automation master station, specifically including:

[0077] If the judgment results show that both are in parallel operation condition, it is determined that the tie switch and the energy storage inverter (PCS) are in parallel operation condition;

[0078] If the judgment results are that the conditions for parallel operation are not met, it is determined that the tie switch and the energy storage inverter (PCS) do not meet the conditions for parallel operation;

[0079] If there is one result that does not meet the parallel operation conditions, go to step S10 for repeated confirmation. If there is still one result that does not meet the parallel operation conditions after repeated confirmation for more than N times, it is determined that the tie switch and the energy storage inverter (PCS) do not meet the parallel operation conditions, where N is the set confirmation number threshold for jumping out of the repeated confirmation cycle. When the comparison result shows that the parallel operation conditions are not met, the device has a repeated confirmation mechanism. By setting the confirmation number threshold N for jumping out of the repeated confirmation cycle, it can ensure that repeated confirmations are performed within a certain number of times, so as to identify and solve temporary or occasional problems, which helps to improve the robustness and reliability of the system.

[0080] In this embodiment, if the result of the determination is that the tie switch and the energy storage inverter (PCS) are in parallel operation condition, the distribution automation master station remotely controls the tie switch to close. At this time, the microgrid operates in the grid-connected mode, and the photovoltaic inverter and the energy storage inverter (PCS) can adjust the operation mode to the optimal state when connected to the grid. Working in the best state, the photovoltaic inverter can maximize the absorption of light energy and convert it into electrical energy to inject into the grid, providing renewable energy. At the same time, the energy storage inverter (PCS) can release the stored electrical energy during peak demand and provide stable power supply to maximize energy utilization and supply efficiency.

[0081] Among them, if the judgment result is that the tie switch and the energy storage inverter (PCS) do not have the conditions for parallel operation, the voltage, frequency and phase of the microgrid are adjusted through the energy storage inverter (PCS) to ensure the stable operation of the microgrid.

[0082] If the power of the energy storage inverter (PCS) does not exceed the limit, go to step S20;

[0083] If the power of the energy storage inverter (PCS) reaches the limit, the tie switch and the energy storage inverter (PCS) cannot be adjusted to parallel operation conditions, and the microgrid remains off-grid. This protection mechanism can prevent the energy storage inverter from overloading, thereby protecting the safe operation of the energy storage inverter.

[0084] Through the judgment logic of the device, the microgrid can switch between grid-connected and off-grid according to actual conditions. When the power of the energy storage inverter does not exceed the limit, the microgrid can further optimize its performance and achieve grid-connected operation to meet greater power demand.

[0085] As a preferred embodiment of the above, in order to further ensure the reliability of the microgrid operation, the microgrid should be connected to the grid as soon as possible through the tie switch if the operating conditions permit, and then go to step S10.

[0086] like Figure 3 As shown, the structural diagram of the implementation case of the present invention, Figure 3 The switches are all automatic switches. Among them, switch #0 is the substation exit switch, and switch #K PCC is the switch at the common connection point between the microgrid and the distribution network, #K PV is the photovoltaic system grid-connected switch, #K B is the grid-connected switch of the energy storage system, #K F1 , #K F2 is the load grid-connected switch, #K L It is a contact switch with adjacent lines. The photovoltaic system, energy storage system and load form a photovoltaic storage microgrid. The energy storage PCS adopts a grid-type control strategy. Under normal circumstances, the microgrid is controlled by #K PCCIn the method of the present invention, the microgrid will repeatedly confirm whether the tie switch can run in parallel with the grid-forming PCS during the on-grid and off-grid switching process. If conditions permit, the parallel operation of the two can improve the reliability of the microgrid operation.

[0087] The following is combined with Figure 3 The technical solution of the present invention is further described in detail with typical cases:

[0088] Example 1: The microgrid is initially running in the grid-connected mode, and the upper distribution network is disconnected for maintenance. PCC , the microgrid needs to switch between grid connection and off-grid connection, and the microgrid switches from grid connection operation at the PCC to grid connection operation at the tie switch. Set N=3, X=5, and the operation is as follows:

[0089] (1) #KL, #KPCC, EMS and distribution automation master station are synchronized, and PCS, BMS, photovoltaic inverter and EMS are synchronized.

[0090] (2) #KL and #KPCC upload the local voltage amplitude, frequency and phase to EMS and distribution automation master station at the same time. PCS uploads the local voltage amplitude, frequency and phase to EMS.

[0091] (3) EMS determines whether #KL and #KPCC are ready for parallel operation, and the distribution automation master station determines whether #KL and #KPCC are ready for parallel operation.

[0092] (4) Compare the judgment result of EMS with that of the distribution automation master station. The judgment result of EMS is that the conditions for parallel operation are met, while the judgment result of the distribution automation master station is that the conditions for parallel operation are not met. Therefore, the process goes to step (1) for repeated confirmation. After repeated confirmation for 2 times, the conditions for parallel operation are met. Therefore, it is determined that #KL and #KPCC meet the conditions for parallel operation.

[0093] (5) #KL and #KPCC meet the conditions for parallel operation. The operation modes of photovoltaic and energy storage remain unchanged. The distribution automation master station first remotely controls #KL to close the circuit breaker, and then remotely controls #KPCC to open the circuit breaker.

[0094] (6) The microgrid is switched from being connected to the grid at the PCC to being connected to the grid at the contact point.

[0095] Example 2: The microgrid is initially running in the grid-connected mode, and the upper distribution network is disconnected for maintenance. PCC , the microgrid needs to switch from grid-connected to off-grid operation. Set N=3, X=5, and the operation is as follows:

[0096] (1) #KL, #KPCC, EMS and distribution automation master station are synchronized, and PCS, BMS, photovoltaic inverter and EMS are synchronized.

[0097] (2) #KL and #KPCC upload the local voltage amplitude, frequency and phase to EMS and distribution automation master station at the same time. PCS uploads the local voltage amplitude, frequency and phase to EMS.

[0098] (3) EMS determines whether #KL and #KPCC are ready for parallel operation, and the distribution automation master station determines whether #KL and #KPCC are ready for parallel operation.

[0099] (4) The judgment result of EMS is compared with that of the distribution automation master station. The results are both that the conditions for parallel operation are not met, so it is determined that #KL and #KPCC do not meet the conditions for parallel operation.

[0100] (5) #KL and #KPCC do not have the conditions for parallel operation. The active output of photovoltaic and energy storage PCS is adjusted and the PCC point power flow information is monitored at the same time. When the PCC switch power flow is adjusted to 0±5kW, photovoltaic and energy storage PCS stop power adjustment and the EMS sends information to the master station to request a planned off-grid operation. The master station disconnects #KPCC according to the gateway request signal, and the microgrid initially completes off-grid operation.

[0101] (6) To further ensure the reliability of microgrid operation, determine as soon as possible whether #KL and PCS are ready for parallel operation. #KL, #KPCC, and EMS are synchronized with the distribution automation master station, and PCS, BMS, and photovoltaic inverters are synchronized with EMS.

[0102] (7) EMS determines whether #KL and PCS meet the conditions for parallel operation, and the distribution automation master station determines whether #KL and PCS meet the conditions for parallel operation.

[0103] (8) Compare the judgment result of EMS with that of the distribution automation master station. The judgment result of EMS is that the conditions for parallel operation are met, while the judgment result of the distribution automation master station is that the conditions for parallel operation are not met. Therefore, the process goes to step (1) for repeated confirmation. If the conditions for parallel operation are still not met after three repeated confirmations, it is determined that #KL and PCS do not meet the conditions for parallel operation.

[0104] (9) #KL and PCS do not meet the conditions for parallel operation, so the energy storage PCS adjusts the voltage, frequency and phase of the microgrid. However, when the power adjustment of the energy storage PCS reaches the limit, #KL and PCS still do not meet the conditions for parallel operation.

[0105] (10) The microgrid maintains off-grid operation.

[0106] Example 3: The microgrid is initially running in the grid-connected mode, and the upper distribution network is disconnected for maintenance. PCC , the microgrid needs to switch between grid-connected and off-grid operation. The microgrid switches from grid-connected operation at the PCC to off-grid operation, and then switches back to grid-connected operation at the tie switch after power adjustment. Set N=3, X=5, and the operation is as follows:

[0107] (1) #KL, #KPCC, EMS and distribution automation master station are synchronized, and PCS, BMS, photovoltaic inverter and EMS are synchronized.

[0108] (2) #KL and #KPCC upload the local voltage amplitude, frequency and phase to EMS and distribution automation master station at the same time. PCS uploads the local voltage amplitude, frequency and phase to EMS.

[0109] (3) EMS determines whether #KL and #KPCC are ready for parallel operation, and the distribution automation master station determines whether #KL and #KPCC are ready for parallel operation.

[0110] (4) The judgment result of EMS is compared with that of the distribution automation master station. The results are both that the conditions for parallel operation are not met, so it is determined that #KL and #KPCC do not meet the conditions for parallel operation.

[0111] (5) #KL and #KPCC do not have the conditions for parallel operation. The active output of photovoltaic and energy storage PCS is adjusted and the PCC point power flow information is monitored at the same time. When the PCC switch power flow is adjusted to 0±5kW, photovoltaic and energy storage PCS stop power adjustment and the EMS sends information to the master station to request a planned off-grid operation. The master station disconnects #KPCC according to the gateway request signal, and the microgrid initially completes off-grid operation.

[0112] (6) To further ensure the reliability of microgrid operation, determine as soon as possible whether #KL and PCS are ready for parallel operation. #KL, #KPCC, and EMS are synchronized with the distribution automation master station, and PCS, BMS, and photovoltaic inverters are synchronized with EMS.

[0113] (7) EMS determines whether #KL and PCS meet the conditions for parallel operation, and the distribution automation master station determines whether #KL and PCS meet the conditions for parallel operation.

[0114] (8) Compare the judgment result of EMS with that of the distribution automation master station. The judgment result of EMS is that the conditions for parallel operation are met, while the judgment result of the distribution automation master station is that the conditions for parallel operation are not met. Therefore, the process goes to step (1) for repeated confirmation. If the conditions for parallel operation are still not met after three repeated confirmations, it is determined that #KL and PCS do not meet the conditions for parallel operation.

[0115] (9) #KL and PCS do not meet the conditions for parallel operation, so the energy storage PCS adjusts the voltage, frequency and phase of the microgrid until #KL and PCS meet the conditions for parallel operation. During this process, the power of the energy storage PCS does not exceed the limit.

[0116] (10) #KL and PCS are ready for parallel operation, and the distribution automation master station first controls #KL to close the circuit breaker remotely.

[0117] (11) The microgrid is transformed from off-grid operation to grid-connected operation at the contact point.

[0118] like Figure 4 As shown, the present invention also includes a planned on-grid and off-grid switching system for photovoltaic and energy storage microgrids, using the above method, including: a time synchronization module, a mode judgment module, a first result comparison switching module, a second result comparison switching module, a first parallel operation condition judgment module, and a second parallel operation condition judgment module; the time synchronization module is used for synchronizing the contact switch, the PCC switch, the microgrid energy management system (EMS) with the distribution automation master station, the energy storage inverter (PCS), the energy storage battery management system (BMS), the photovoltaic inverter and the microgrid energy management system (EMS);

[0119] The mode judgment module is used for the tie switch and PCC switch to upload the local voltage amplitude, frequency and phase to the microgrid energy management system (EMS) and the distribution automation master station at the same time, and the energy storage inverter (PCS) to upload the local voltage amplitude, frequency and phase to the microgrid energy management system (EMS); at this time, if the microgrid is in the grid-connected operation mode, it will switch to the first parallel operation condition judgment module; if the microgrid is in the off-grid operation mode, it will switch to the second parallel operation condition judgment module;

[0120] The first parallel operation condition judgment module is used for the microgrid energy management system (EMS) to judge whether the tie switch and the PCC switch have the parallel operation conditions, and the distribution automation master station judges whether the tie switch and the PCC switch have the parallel operation conditions;

[0121] The first result comparison switching module is used to compare the judgment result of the microgrid energy management system (EMS) with the judgment result of the distribution automation master station, and perform mode switching according to the comparison result;

[0122] The second parallel operation condition judgment module, the microgrid energy management system (EMS) judges whether the tie switch and the energy storage inverter (PCS) have the parallel operation conditions, and the distribution automation master station judges whether the tie switch and the energy storage inverter (PCS) have the parallel operation conditions;

[0123] In the second result comparison switching module, the judgment result of the microgrid energy management system (EMS) is compared with the judgment result of the distribution automation master station, and the mode is switched according to the comparison result.

[0124] See also Figure 5 A computer device 400 provided in an embodiment of the present application includes: a processor 410 and a memory 420, wherein the memory 420 stores a computer program executable by the processor 410, and when the computer program is executed by the processor 410, the above method is executed.

[0125] The embodiment of the present application further provides a storage medium 430 on which a computer program is stored. When the computer program is run by the processor 410, the above method is executed.

[0126] Among them, the storage medium 430 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, disk or optical disk.

[0127] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0128] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0129] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0130] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0131] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples (non-exhaustive list) of computer-readable media include the following: an electrical connection with one or more wires (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk 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 and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0132] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0133] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0134] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for planned on-grid and off-grid switching of a photovoltaic and energy storage microgrid, characterized in that: The device used in the method for planned on-grid and off-grid switching of the photovoltaic storage microgrid includes: The photovoltaic inverter, energy storage battery management system, energy storage inverter, tie switch, and PCC switch communicate quickly with the microgrid energy management system through optical fiber; The photovoltaic inverter, the energy storage battery management system, the energy storage inverter and the microgrid energy management system are in two-way communication, uploading their own operating status to the microgrid energy management system and receiving control instructions from the microgrid energy management system; The microgrid energy management system communicates with the distribution automation master station through a gateway, wherein the microgrid energy management system and the gateway are in two-way communication, and the gateway and the distribution automation master station are in two-way communication, uploading the microgrid operation status to the distribution automation master station and forwarding the distribution automation master station control instructions; The tie switch and the PCC switch are both automated switches, which use wireless communication with the distribution automation master station for two-way communication, upload their own open and close position status to the distribution automation master station and receive remote control instructions from the distribution automation master station; The method comprises: S10: The tie switch, PCC switch, microgrid energy management system and distribution automation master station are synchronized, and the energy storage inverter, energy storage battery management system, photovoltaic inverter and microgrid energy management system are synchronized; S20: The tie switch and PCC switch upload the local voltage amplitude, frequency and phase to the microgrid energy management system and the distribution automation master station at the same time, and the energy storage inverter uploads the local voltage amplitude, frequency and phase to the microgrid energy management system; at this time, if the microgrid is in the grid-connected operation mode, go to step S30; if the microgrid is in the off-grid operation mode, go to step S50; S30: The microgrid energy management system determines whether the tie switch and the PCC switch meet the conditions for parallel operation, and the distribution automation master station determines whether the tie switch and the PCC switch meet the conditions for parallel operation; S40: The judgment result of the microgrid energy management system is compared with the judgment result of the distribution automation master station, and the mode is switched according to the comparison result; S50: The microgrid energy management system determines whether the tie switch and the energy storage inverter meet the conditions for parallel operation, and the distribution automation master station determines whether the tie switch and the energy storage inverter meet the conditions for parallel operation; S60: The judgment result of the microgrid energy management system is compared with the judgment result of the distribution automation master station, and the mode is switched according to the comparison result; By repeatedly checking whether the conditions for parallel operation are met, a decision is made as to whether the microgrid should operate off-grid or on-grid at the contact point. When it is detected that the conditions are not met, the system can automatically switch to the corresponding operating mode.

2. The method for planned on-grid and off-grid switching of a photovoltaic energy storage microgrid according to claim 1, characterized in that: In step S40, the determination result of the microgrid energy management system is compared with the determination result of the distribution automation master station, specifically including: If the judgment results show that both of them meet the conditions for parallel operation, then it is determined that the tie switch and PCC switch meet the conditions for parallel operation; If the judgment results are that the conditions for parallel operation are not met, it is determined that the tie switch and PCC switch do not meet the conditions for parallel operation; If there is one result that does not meet the parallel operation conditions, go to step S10 for repeated confirmation. When the number of repeated confirmations is greater than N times and there is still one result that does not meet the parallel operation conditions, it is determined that the connecting switch and the PCC switch do not meet the parallel operation conditions, where N is the set confirmation number threshold for jumping out of the repeated confirmation cycle.

3. The method for planned on-grid and off-grid switching of a photovoltaic energy storage microgrid according to claim 2 is characterized in that: If the judgment result is that the tie switch and the PCC switch meet the conditions for parallel operation, the operation mode of the photovoltaic grid-connected inverter and the energy storage grid-connected inverter remains unchanged. The distribution automation master station first remotely controls the tie switch to close, and then remotely controls the PCC switch to open.

4. The method for planned on-grid and off-grid switching of a photovoltaic energy storage microgrid according to claim 2, characterized in that: If the judgment result is that the tie switch and the PCC switch do not meet the conditions for parallel operation, the active output of the photovoltaic grid-connected inverter and the energy storage grid-connected inverter is adjusted and the power flow information of the PCC point is monitored at the same time.

5. The method for planned on-grid and off-grid switching of a photovoltaic energy storage microgrid according to claim 4 is characterized in that: If the PCC switch power flow is 0±XkW, the photovoltaic grid-connected inverter and the energy storage grid-connected inverter stop power adjustment and the microgrid energy management system sends information to the distribution automation master station to request a planned off-grid operation. The distribution automation master station remotely controls the PCC switch to open, where X is the power difference that will not affect the internal operation of the microgrid during the on-grid and off-grid conversion. If the PCC switch power flow is not 0±XkW, part of the photovoltaic power or load will be cut off to make the PCC switch power flow meet 0±XkW.

6. The method for planned on-grid and off-grid switching of a photovoltaic energy storage microgrid according to claim 1, characterized in that: In step S60, the determination result of the microgrid energy management system is compared with the determination result of the distribution automation master station, specifically including: If the judgment results show that both are in parallel operation condition, it is determined that the tie switch and the energy storage inverter are in parallel operation condition; If the judgment results are that the conditions for parallel operation are not met, it is determined that the tie switch and the energy storage inverter do not meet the conditions for parallel operation; If there is one result that does not meet the parallel operation conditions, go to step S10 for repeated confirmation. When there is still one result that does not meet the parallel operation conditions after repeated confirmation for more than N times, it is determined that the connecting switch and the energy storage inverter do not meet the parallel operation conditions, where N is the set confirmation number threshold for jumping out of the repeated confirmation cycle.

7. The method for planned on-grid and off-grid switching of a photovoltaic energy storage microgrid according to claim 6, characterized in that: If the result of the determination is that the interconnecting switch and the energy storage inverter are capable of parallel operation, the distribution automation master station remotely controls the interconnecting switch to close.

8. The method for planned on-grid and off-grid switching of a photovoltaic energy storage microgrid according to claim 6, characterized in that: If the result of the determination is that the tie switch and the energy storage inverter do not meet the conditions for parallel operation, the voltage, frequency and phase of the microgrid are adjusted through the energy storage inverter; If the power of the energy storage inverter does not exceed the limit, go to step S20; If the power of the energy storage inverter reaches the limit, the interconnecting switch and the energy storage inverter cannot be adjusted to parallel operation conditions, and the microgrid remains off-grid.

9. A planned on-grid and off-grid switching system for a photovoltaic and energy storage microgrid, characterized in that: Using the method as claimed in any one of claims 1 to 8, comprising: a time synchronization module, a mode judgment module, a first result comparison switching module, a second result comparison switching module, a first parallel operation condition judgment module and a second parallel operation condition judgment module; Timing module, used for synchronizing the contact switch, PCC switch, microgrid energy management system with the distribution automation master station, energy storage inverter, energy storage battery management system, photovoltaic inverter and microgrid energy management system; A mode judgment module is used for the tie switch and the PCC switch to upload the local voltage amplitude, frequency and phase to the microgrid energy management system and the distribution automation master station at the same time, and the energy storage inverter to upload the local voltage amplitude, frequency and phase to the microgrid energy management system; at this time, if the microgrid is in the grid-connected operation mode, it will switch to the first parallel operation condition judgment module; if the microgrid is in the off-grid operation mode, it will switch to the second parallel operation condition judgment module; The first parallel operation condition judgment module is used for the microgrid energy management system to judge whether the tie switch and the PCC switch have the parallel operation conditions, and the distribution automation master station judges whether the tie switch and the PCC switch have the parallel operation conditions; The first result comparison switching module is used to compare the judgment result of the microgrid energy management system with the judgment result of the distribution automation master station, and switch the mode according to the comparison result; The second parallel operation condition judgment module, the microgrid energy management system judges whether the tie switch and the energy storage inverter meet the parallel operation conditions, and the distribution automation master station judges whether the tie switch and the energy storage inverter meet the parallel operation conditions; The second result comparison switching module compares the judgment result of the microgrid energy management system with the judgment result of the distribution automation master station, and switches the mode according to the comparison result.

10. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 8 is implemented.

11. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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