Multi-source cooperative fault ride-through method and device for isolated power grid

Abstract

The application provides a multi-source cooperative fault ride-through method and device for an isolated power grid. The method comprises the following steps: acquiring a grid-connected point voltage of the isolated power grid at a first time; determining whether the grid-connected point voltage is within a preset voltage range to obtain a first determination result; in the case that the first determination result is no, performing first excitation control on a synchronous generator in the isolated power grid; acquiring a grid-connected point voltage of the isolated power grid at a second time, and determining whether the grid-connected point voltage at the second time is within the preset voltage range to obtain a second determination result, wherein the grid-connected point voltage at the second time is the grid-connected point voltage after the first excitation control on the synchronous generator; in the case that the second determination result is yes, performing second excitation control on the synchronous generator, and controlling a photovoltaic system in the isolated power grid to generate power for the isolated power grid by using a first control method; in the case that the second determination result is no, controlling the photovoltaic system to generate power for the isolated power grid by using a second control method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fault ride-through, in particular to a multi-source cooperative fault ride-through method for an isolated power grid, a multi-source cooperative fault ride-through device for an isolated power grid, a computer readable storage medium and an electronic device. BACKGROUND

[0002] The feature of a new power system is that new energy is the main body and conventional synchronous units are auxiliary. The new power system has the characteristics of "high proportion of new energy and high proportion of power electronic equipment". New energy generation has the characteristics of strong randomness, weak support, low disturbance resistance and low inertia response. Therefore, in complex or special scenarios, new complex chain reaction problems may occur in the new power system, which brings great challenges to the safe operation of the system and the transformation and upgrading of the traditional power system.

[0003] With the energy saving index of fuel units, the auxiliary machines of the existing technology of thermal power units gradually adopt frequency converter driving. However, the overload capacity of auxiliary machine frequency converter is weak, and there is a problem similar to the weak fault ride-through capability of photovoltaic power generation units. Low voltage may occur during fault ride-through, which may cause the auxiliary machine frequency converter to lock output, and then large-scale boiler shutdown may occur, and even trigger the fuel unit to trip, thereby causing shutdown accidents. Therefore, for an isolated power system with new energy photovoltaic power generation units and traditional synchronous generators, the adaptability of new energy equipment and stations to traditional power systems needs to be considered, and the fault ride-through capability is an important link in the network involved in new energy stations. SUMMARY

[0004] The main purpose of the present application is to provide a multi-source cooperative fault ride-through method for an isolated power grid, a multi-source cooperative fault ride-through device for an isolated power grid, a computer readable storage medium and an electronic device. To at least solve the problem that new energy power generation is difficult to be compatible with traditional power systems during fault ride-through in the prior art.

[0005] To achieve the above object, according to one aspect of the present application, a multi-source cooperative fault ride-through method for an isolated power grid is provided, comprising: obtaining a grid-connected point voltage of the isolated power grid at a first time; determining whether the grid-connected point voltage is within a preset voltage range to obtain a first determination result; in a case where the first determination result indicates no, performing first excitation control on a synchronous generator in the isolated power grid, the first excitation control being used to update an initial voltage of the synchronous generator to a first preset voltage; obtaining a grid-connected point voltage of the isolated power grid at a second time, and determining whether the grid-connected point voltage at the second time is within the preset voltage range to obtain a second determination result, the second time being the grid-connected point voltage after the first excitation control on the synchronous generator; in a case where the second determination result indicates yes, performing second excitation control on the synchronous generator, and controlling a photovoltaic system in the isolated power grid to generate power for the isolated power grid by using a first control method, the second excitation control being used to update the first preset voltage of the synchronous generator to the initial voltage, the first control method comprising a maximum power point tracking method and a rated power control method, the maximum power point tracking method being used to track a maximum power point of the photovoltaic system, and the rated power control method being used to control the photovoltaic system to output rated active power and rated reactive power; in a case where the second determination result indicates no, controlling the photovoltaic system to generate power for the isolated power grid by using a second control method, the second control method comprising a direct-current voltage control method and a first power control method, the direct-current voltage control method being used to stabilize a direct-current bus voltage of the photovoltaic system, and the first power control method being used to control the photovoltaic system to output first active power and first reactive power.

[0006] Optionally, the power generation device of the isolated power grid further comprises auxiliary machine equipment, and in the case where the second determination result indicates yes, the multi-source cooperative fault ride-through method further comprises: controlling the auxiliary machine equipment to supply power to first loads, the first loads being all loads in the isolated power grid supplied by the auxiliary machine equipment.

[0007] Optionally, the power generation device of the isolated power grid further comprises auxiliary machine equipment, and in the case where the second determination result indicates no, the multi-source cooperative fault ride-through method further comprises: controlling the auxiliary machine equipment to supply power to second loads, the second loads being part of all loads in the isolated power grid supplied by the auxiliary machine equipment.

[0008] Optionally, the power generation device of the isolated power grid further comprises auxiliary machine equipment and a battery, and in the case where the first determination result indicates yes, the multi-source cooperative fault ride-through method further comprises: controlling the auxiliary machine equipment to supply power to third loads, the third loads being all loads in the isolated power grid supplied by the auxiliary machine equipment, and controlling the auxiliary machine equipment to charge the battery.

[0009] Optionally, in the case where the second determination result indicates no, the multi-source cooperative fault ride-through method further comprises: determining whether the DC bus voltage of the photovoltaic system is overvoltage, obtaining a third determination result; in the case where the third determination result indicates yes, performing the step of controlling the photovoltaic system to generate power for the isolated power grid by using the second control method; in the case where the third determination result indicates no, controlling the photovoltaic system to generate power for the isolated power grid by using the maximum power point tracking method and the second power control method, the second power control method being used to control the photovoltaic system to output the second active power and the second reactive power.

[0010] Optionally, the photovoltaic system comprises a photovoltaic cell panel and a two-stage photovoltaic inverter, the two-stage photovoltaic inverter comprising a front stage and a rear stage, the front stage being used for DC-DC boost conversion, and the rear stage being used for AC-DC conversion, the second excitation control of the synchronous generator and the control of the photovoltaic system to generate power for the isolated power grid by using the first control method in the isolated power grid comprising: performing the first preset excitation control of the synchronous generator to update the first preset voltage to the second preset voltage; performing the second preset excitation control of the synchronous generator to update the second preset voltage to the initial voltage, the second excitation control comprising the first preset excitation control and the second preset excitation control; controlling the front stage to track the maximum power point of the photovoltaic cell panel by using the maximum power point tracking control method; and controlling the rear stage to control the two-stage photovoltaic inverter to output the rated active power and the rated reactive power by using the rated power control method, so as to generate power for the isolated power grid.

[0011] Optionally, the photovoltaic system comprises a photovoltaic cell panel and a two-stage photovoltaic inverter, the structure of the two-stage photovoltaic inverter comprising a front stage and a rear stage, the front stage being used for DC-DC boost conversion, and the rear stage being used for AC-DC conversion, the control of the photovoltaic system to generate power for the isolated power grid by using the second control method comprising: controlling the front stage to stabilize the DC bus voltage of the photovoltaic system by using the DC voltage control method; and controlling the rear stage to control the two-stage photovoltaic inverter to output the first active power and the first reactive power by using the first power control method, so as to generate power for the isolated power grid.

[0012] According to another aspect of the present application, a multi-source cooperative fault ride-through device for an isolated power grid is provided, comprising: an acquisition module configured to acquire a grid-connected point voltage of the isolated power grid at a first time; a first judgment module configured to determine whether the grid-connected point voltage is within a preset voltage range, and obtain a first judgment result; a first execution module configured to, in a case where the first judgment result indicates no, perform first excitation control on a synchronous generator in the isolated power grid, the first excitation control being configured to update an initial voltage of the synchronous generator to a first preset voltage; a second judgment module configured to acquire a grid-connected point voltage of the isolated power grid at a second time, and determine whether the grid-connected point voltage at the second time is within the preset voltage range, and obtain a second judgment result, the second time being the grid-connected point voltage after the first excitation control on the synchronous generator; a second execution module configured to, in a case where the second judgment result indicates yes, perform second excitation control on the synchronous generator, and control a photovoltaic system in the isolated power grid to generate power for the isolated power grid using a first control method, the second excitation control being configured to update the first preset voltage of the synchronous generator to the initial voltage, the first control method comprising a maximum power point tracking method and a rated power control method, the maximum power point tracking method being configured to track a maximum power point of the photovoltaic system, and the rated power control method being configured to control the photovoltaic system to output rated active power and rated reactive power; and a third execution module configured to, in a case where the second judgment result indicates no, control the photovoltaic system to generate power for the isolated power grid using a second control method, the second control method comprising a direct-current voltage control method and a first power control method, the direct-current voltage control method being configured to stabilize a direct-current bus voltage of the photovoltaic system, and the first power control method being configured to control the photovoltaic system to output first active power and first reactive power.

[0013] According to still another aspect of the present application, a computer-readable storage medium is provided, the computer-readable storage medium comprising a stored program, wherein the program, when executed, controls a device in which the computer-readable storage medium is located to perform the multi-source cooperative fault ride-through method for an isolated power grid described above.

[0014] According to yet another aspect of the present application, one or more processors, a memory, and one or more programs are provided, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs comprise a program for performing the multi-source cooperative fault ride-through method for an isolated power grid described above.

[0015] With the technical solution of the application, firstly, the bus voltage of the grid-connected point of the isolated power grid is acquired, and whether the voltage of the grid-connected point of the isolated power grid is located in a preset voltage range is judged, so that a first judgment result can be obtained, and it can be considered that the voltage of the grid-connected point at this time is acquired at a first time. In the case that the first judgment result indicates no, the synchronous generator in the isolated power grid is subjected to first excitation control, and in this step, the first excitation control can be used to update the initial voltage of the synchronous generator to a first preset voltage. Further, after the first excitation control of the synchronous generator, the voltage of the grid-connected point of the isolated power grid is acquired again, and whether the voltage acquired again is located in the preset voltage range is judged, so that a second judgment result can be obtained, wherein it can be considered that the voltage of the grid-connected point of the isolated power grid acquired again is acquired at a second time, and the first time occurs before the second time. Then, in the case that the second judgment result indicates yes, the synchronous generator subjected to the first excitation control can be subjected to second excitation control, and the photovoltaic system is controlled to generate power for the isolated power grid by using a first control method. In this step, the second excitation control can be used to update the first preset voltage of the synchronous generator to the initial voltage, so that during the fault, the problem that the first excitation control of the synchronous generator causes the power angle to be reversed due to the additional first preset voltage is avoided, and a positive role is played in system recovery; the first control method can include a maximum power point tracking method and a rated power control method, wherein the maximum power point tracking method is used to track the maximum power point of the photovoltaic system to maintain the direct-current bus voltage balance of the photovoltaic system, and the rated power control method is used to control the photovoltaic system to output rated active power and rated reactive power to realize power balance. In addition, in the case that the second judgment result indicates no, the photovoltaic system can be controlled to generate power for the isolated power grid by using a second control method. In this step, the second control method can include a direct-current voltage control method and a first power control method. In this step, the direct-current voltage control method can be used to stabilize the direct-current bus voltage of the photovoltaic system to maintain the direct-current bus voltage balance of the photovoltaic system, and the first power control method is used to control the photovoltaic system to output first active power and first reactive power, that is, to realize power balance by recalculating the first active power and the first reactive power of the photovoltaic system. In summary, the synchronous generator and the photovoltaic system in the application can realize cooperative fault ride-through, so that the problem that new energy power generation (photovoltaic system) is difficult to be compatible with traditional power systems (synchronous generators) during fault ride-through in the prior art is solved, and large-scale grid disconnection accidents in the isolated power grid can be avoided. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which form a part of the present description, are included to provide a further understanding of the application and are incorporated herein for explanation by way of exemplification. The present description and drawings are not intended to limit the application thereto.

[0017] Figure 1 A hardware structure block diagram of a mobile terminal performing a multi-source cooperative fault ride-through method of an isolated power grid is shown according to an embodiment of the present application;

[0018] Figure 2 A flowchart of a multi-source cooperative fault ride-through method of an isolated power grid is shown according to an embodiment of the present application;

[0019] Figure 3 A circuit schematic diagram of a front-stage circuit and a rear-stage circuit of a two-stage photovoltaic inverter in a multi-source cooperative fault ride-through method of an isolated power grid is shown according to an embodiment of the present application;

[0020] Figure 4 A control block diagram of a front-stage circuit switching process in a multi-source cooperative fault ride-through method of an isolated power grid is shown according to an embodiment of the present application;

[0021] Figure 5 A control strategy schematic diagram of a rear-stage circuit in a multi-source cooperative fault ride-through method of an isolated power grid is shown according to an embodiment of the present application;

[0022] Figure 6 A control block diagram of a rear-stage circuit switching process in a multi-source cooperative fault ride-through method of an isolated power grid is shown according to an embodiment of the present application;

[0023] Figure 7 A control block diagram of an excitation process of a synchronous generator in a multi-source cooperative fault ride-through method of an isolated power grid is shown according to an embodiment of the present application;

[0024] Figure 8 A compensation device schematic diagram of an auxiliary machine frequency converter additional energy storage device in a multi-source cooperative fault ride-through method of an isolated power grid is shown according to an embodiment of the present application;

[0025] Figure 9 A flowchart of a specific multi-source cooperative fault ride-through method of an isolated power grid is shown according to an embodiment of the present application;

[0026] Figure 10 A three-phase fault system voltage situation schematic diagram of Case 1 in a specific multi-source cooperative fault ride-through method of an isolated power grid is shown according to an embodiment of the present application;

[0027] Figure 11 A three-phase fault system reactive power situation schematic diagram of Case 1 in a specific multi-source cooperative fault ride-through method of an isolated power grid is shown according to an embodiment of the present application;

[0028] Figure 12Fig. 2 shows a schematic diagram of a three-phase fault system voltage condition of Case 2 in a specific multi-source cooperative fault ride-through method of an isolated power grid according to an embodiment of the present application;

[0029] Figure 13 Fig. 3 shows a schematic diagram of a three-phase fault system reactive power condition of Case 2 in a specific multi-source cooperative fault ride-through method of an isolated power grid according to an embodiment of the present application;

[0030] Figure 14 Fig. 4 shows a structure block diagram of a multi-source cooperative fault ride-through device of an isolated power grid according to an embodiment of the present application.

[0031] In the above drawings, the following reference signs apply:

[0032] 102, processor; 104, memory; 106, transmission device; 108, input and output device; 10, acquisition module; 20, first judging module; 30, first execution module; 40, second judging module; 50, second execution module; 60, third execution module. DETAILED DESCRIPTION

[0033] It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other without conflict. The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0034] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0035] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units need not be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0036] As described in the background section, auxiliary equipment in existing thermal power units is increasingly driven by frequency converters. However, the overload capacity of auxiliary equipment frequency converters is weak, and they have a similar problem to the weak fault ride-through capability of photovoltaic generator sets. Low voltage may occur during fault ride-through, causing the auxiliary equipment frequency converter to lock out its output, which may lead to large-scale boiler shutdowns or even triggering the tripping of fuel units, resulting in shutdown accidents. In order to solve the problem that new energy power generation is difficult to be compatible with traditional power systems during fault ride-through in the existing technology, the embodiments of this application provide a multi-source cooperative fault ride-through method for isolated power grids, a multi-source cooperative fault ride-through device for isolated power grids, a computer-readable storage medium, and an electronic device.

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0038] The methods and embodiments provided in this application can be executed on a mobile terminal, computer terminal, or similar computing device. Taking running on a mobile terminal as an example, Figure 1 This is a hardware structure block diagram of a mobile terminal for a multi-source cooperative fault ride-through method for an isolated power grid according to an embodiment of the present invention. Figure 1 As shown, a mobile terminal may include one or more ( Figure 1 Only one is shown in the diagram. A processor 102 (which may include, but is not limited to, a microprocessor MCU or a programmable logic device FPGA, etc.) and a memory 104 for storing data are also shown. The mobile terminal may further include a transmission device 106 for communication functions and an input / output device 108. Those skilled in the art will understand that... Figure 1 The structure shown is for illustrative purposes only and does not limit the structure of the mobile terminal described above. For example, the mobile terminal may also include components that are more... Figure 1 The more or fewer components shown, or having the same Figure 1 The different configurations shown.

[0039] The memory 104 can be used to store computer programs, such as software programs of application software and modules, such as the computer program corresponding to the multi-source cooperative fault ride-through method of isolated power grid in the embodiments of the present application. The processor 102 can execute various functional applications and data processing, i.e., implement the above method, by running the computer program stored in the memory 104. The memory 104 can include a high-speed random access memory, and can further include a non-volatile memory, such as one or more magnetic storage devices, flash memories, or other non-volatile solid-state memories. In some examples, the memory 104 can further include a memory remotely arranged with respect to the processor 102, which can be connected to the mobile terminal through a network. Examples of the above network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof. The transmission device 106 is used to receive or send data via a network. The specific examples of the above network can include a wireless network provided by a communication provider of the mobile terminal. In one example, the transmission device 106 includes a network adapter (NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 106 can be a radio frequency (RF) module, which is used to communicate with the Internet in a wireless manner.

[0040] In the embodiments of the present application, a multi-source cooperative fault ride-through method of isolated power grid running on a mobile terminal, a computer terminal or a similar computing device is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0041] Figure 2 is a flowchart of the multi-source cooperative fault ride-through method of isolated power grid according to the embodiments of the present application. As shown in Figure 2 , the method comprises the following steps:

[0042] In step S201, the grid-connected point voltage of the isolated power grid at a first time is acquired.

[0043] Specifically, in the case of failure of the AC power supply of the isolated power grid, the grid-connected point voltage of the isolated power grid will appear voltage sag or power supply interruption phenomenon, thereby causing large-scale off-grid accidents in the isolated power grid. Therefore, the present application first acquires the grid-connected point voltage of the isolated power grid, thereby providing an analysis basis for the fault ride-through method for avoiding large-scale off-grid accidents in the isolated power grid.

[0044] Step S202, judging whether the grid-connected point voltage is located in a preset voltage range, to obtain a first judgment result;

[0045] Specifically, the grid-connected point voltage in the normal operation of the isolated power grid can be taken as a standard voltage, the minimum voltage in the preset voltage range can be the voltage after the sudden drop of the grid-connected point voltage, and the maximum voltage in the preset voltage range can be the standard voltage. Those skilled in the art can reasonably set the preset voltage range according to the actual situation, which is not limited in the present application.

[0046] Optionally, the obtaining step can also be obtaining the grid-connected point voltage drop depth of the grid-connected point voltage in the isolated power grid, and the judging step can also be judging whether the grid-connected point voltage drop depth is located in a preset drop depth range. The preset drop depth range can be the grid-connected point voltage drop depth allowed to drop, and those skilled in the art can reasonably select according to the actual situation.

[0047] Step S203, in the case that the first judgment result indicates no, performing first excitation control on the synchronous generator in the isolated power grid, and the first excitation control is used to update the initial voltage of the synchronous generator to a first preset voltage;

[0048] Specifically, the case that the first judgment result indicates no means that the grid-connected point voltage in the isolated power grid has dropped suddenly.

[0049] Optionally, most of the traditional power generation systems have strong anti-disturbance ability and strong support ability for the isolated power grid due to the voltage characteristics and excitation automatic regulation system of the synchronous generator. Unlike new energy generators (photovoltaic systems) which are limited by power electronic devices, the synchronous generator has stronger short-circuit current capacity. Therefore, in the case that the grid-connected point voltage drops suddenly, considering the recovery effect of the excitation regulation process of the synchronous generator after the fault of the system (isolated power grid), the first excitation control can be performed on the synchronous generator in the isolated power grid to update the initial voltage of the synchronous generator to the first preset voltage, so as to realize the first excitation control of the synchronous generator.

[0050] Step S204, obtaining the grid-connected point voltage of the isolated power grid at a second time, and judging whether the grid-connected point voltage at the second time is located in a preset voltage range, to obtain a second judgment result, and the grid-connected point voltage at the second time is the grid-connected point voltage after the first excitation control on the synchronous generator;

[0051] Specifically, after the first excitation control of the synchronous generator, the grid-connected point voltage of the isolated power grid can be acquired again, i.e., the grid-connected point voltage at the second time. Then, it can be determined again whether the grid-connected point voltage at the second time is within the preset voltage range, and a second determination result indicating yes or a second determination result indicating no can be obtained.

[0052] In the case where the second determination result indicates yes, the second excitation control of the synchronous generator is performed, and the photovoltaic system is controlled to generate power for the isolated power grid by using the first control method. The second excitation control is used to update the first preset voltage of the synchronous generator to the initial voltage. The first control method includes a maximum power point tracking method and a rated power control method. The maximum power point tracking method is used to track the maximum power point of the photovoltaic system, and the rated power control method is used to control the photovoltaic system to output rated active power and rated reactive power.

[0053] Specifically, in the case where the second determination result indicates yes, it indicates that the fault of the isolated power grid has been cleared, so that the second excitation control of the synchronous generator can be performed to restore the first preset voltage of the synchronous generator to the initial voltage. In addition, since the synchronous generator and the photovoltaic system are used to cooperatively perform fault ride-through in the present application, the first control method is used to control the photovoltaic system to generate power for the isolated power grid at the same time, wherein the first control method includes the maximum power point tracking method and the rated power control method, so as to maintain the balance of the direct-current bus voltage and the balance of the power of the photovoltaic system.

[0054] In the case where the second determination result indicates no, the photovoltaic system is controlled to generate power for the isolated power grid by using the second control method. The second control method includes a direct-current voltage control method and a first power control method. The direct-current voltage control method is used to stabilize the direct-current bus voltage of the photovoltaic system, and the first power control method is used to control the photovoltaic system to output first active power and first reactive power.

[0055] Specifically, in the case where the second determination result indicates no, it indicates that the fault of the isolated power grid has not been cleared. Therefore, the fault ride-through method of controlling the photovoltaic system to generate power for the isolated power grid by using the second control method is also used in the present application, so as to achieve the purpose of cooperatively performing fault ride-through of the first excitation control of the synchronous generator and the second control method of the photovoltaic system for the isolated power grid, thereby avoiding large-scale off-grid accidents.

[0056] By the embodiment, firstly, in the case of obtaining the bus voltage of the grid-connected point of the isolated power grid, a first determination result can be obtained by judging whether the grid-connected point voltage is within a preset voltage range. In the case of indicating no for the first determination result, firstly, the synchronous generator in the isolated power grid is subjected to first excitation control, and secondly, a second determination result can be obtained by judging whether the power generation equipment in the isolated power grid is normally operated. In this step, the first excitation control can be used to update the initial voltage of the synchronous generator to a first preset voltage. Further, in the case of indicating yes for the second determination result, the synchronous generator subjected to the first excitation control can be subjected to second excitation control, and the photovoltaic system can be controlled to generate power for the isolated power grid by using a first control method. In this step, the second excitation control can be used to update the first preset voltage of the synchronous generator to the initial voltage, thereby avoiding the problem that the first excitation control of the synchronous generator during the fault causes the first preset voltage to be added, resulting in a reverse power angle, and playing a positive role in system recovery; the first control method can include a maximum power point tracking method and a rated power control method, wherein the maximum power point tracking method is used to track the maximum power point of the photovoltaic system to maintain the bus voltage balance, and the rated power control method is used to control the photovoltaic system to output rated active power and rated reactive power to achieve power balance. In addition, in the case of indicating no for the second determination result, the photovoltaic system can be controlled to generate power for the isolated power grid by using a second control method. In this step, the second control method can include the maximum power point tracking method and the first power control method, and the maximum power point tracking method is used to track the maximum power point of the photovoltaic system to maintain the direct-current bus voltage balance of the photovoltaic system, and the first power control method is used to control the photovoltaic system to output first active power and first reactive power, i.e., to achieve power balance by recalculating the first active power and the first reactive power of the photovoltaic system. That is, by the application, the fault ride-through of the synchronous generator and the photovoltaic system can be synergistically acted, and large-scale grid separation accidents in the isolated power grid can be avoided, thereby solving the problem in the prior art that new energy power generation (photovoltaic system) is difficult to be compatible with traditional power systems (synchronous generators) during fault ride-through.

[0057] In one aspect, in some optional embodiments, the power generation equipment of the isolated power grid further includes auxiliary equipment, i.e., after the first excitation control of the synchronous generator, in order to improve the safe and reliable operation of the isolated power grid, the fault ride-through capability of the auxiliary equipment can also be considered, so that in the case of indicating yes for the second determination result, the multi-source synergistic fault ride-through method further includes: controlling the auxiliary equipment to supply power to the first load, and the first load is all the loads in the isolated power grid that are supplied with power by the auxiliary equipment.

[0058] In some optional embodiments, the power generation device of the isolated power grid further comprises auxiliary equipment. After the first excitation control of the synchronous generator, in order to improve the safe and reliable operation of the isolated power grid, the fault ride-through capability of the auxiliary equipment can also be considered. Therefore, when the second determination result is negative, the multi-source cooperative fault ride-through method further comprises: controlling the auxiliary equipment to supply power to the second load, the second load being part of all loads in the isolated power grid that are supplied by the auxiliary equipment. It can be understood that when the second determination result is negative, the grid connection point voltage of the isolated power grid has not yet recovered to the grid connection point voltage in the normal operation stage of the isolated power grid, so that the grid connection point voltage at this time may threaten the auxiliary equipment, causing the auxiliary equipment to trip and protect. Therefore, the method adopted in this embodiment cuts off part of the load in the isolated power grid for operation, so as to achieve the purpose of improving the safety and stability of the isolated power grid.

[0059] It should be noted that the power generation device of the isolated power grid of the present application can further comprise a battery. Therefore, when the second determination result is negative, although the grid connection point voltage of the isolated power grid has not yet recovered to the grid connection point voltage in the normal operation stage of the isolated power grid, it will not threaten the auxiliary equipment, causing the auxiliary equipment to trip and protect. At this time, it is not necessary to cut off part of the load in the isolated power grid, that is, the auxiliary equipment can be controlled to supply power to the first load, and at the same time, the battery can be controlled to drive the auxiliary equipment, so as to achieve the purpose of improving the safety and stability of the isolated power grid.

[0060] In some optional embodiments, the power generation device of the isolated power grid further comprises auxiliary equipment and a battery. In order to enable the battery to have the ability to drive the auxiliary equipment when the grid connection point voltage of the isolated power grid is a fault voltage (the grid connection point voltage is not located in the preset voltage range), the multi-source cooperative fault ride-through method further comprises, when the first determination result is positive: controlling the auxiliary equipment to supply power to the third load, the third load being all loads in the isolated power grid that are supplied by the auxiliary equipment, and controlling the auxiliary equipment to charge the battery.

[0061] In some optional embodiments, when the second determination result is negative, the multi-source cooperative fault ride-through method further comprises: determining whether the direct-current bus voltage of the photovoltaic system is overvoltage, to obtain a third determination result; when the third determination result is positive, performing the step of controlling the photovoltaic system to generate power for the isolated power grid by using the second control method; and when the third determination result is negative, controlling the photovoltaic system to generate power for the isolated power grid by using a third control method, the third control method comprising a maximum power point tracking method and a second power control method, the second power control method being used to control the photovoltaic system to output a second active power and a second reactive power.

[0062] In the above embodiments, after the step of performing the first excitation control on the synchronous generator, in the case that the grid-connected point voltage of the isolated power grid is still the fault voltage, i.e., the second determination result indicates no, different fault ride-through strategies are adopted for the two cases of overvoltage of the DC bus voltage of the photovoltaic system and no overvoltage of the DC bus voltage of the photovoltaic system. That is, in the case that the detected DC bus voltage exceeds the rated voltage that the inverter in the photovoltaic system can withstand, it can be considered that the DC bus voltage of the photovoltaic system is overvoltage (i.e., the third determination result indicates yes), at this time, the step of controlling the photovoltaic system to generate power for the isolated power grid by using the second control method can be performed; and in the case that the detected DC bus voltage does not exceed the rated voltage that the inverter in the photovoltaic system can withstand, it can be considered that the DC bus voltage of the photovoltaic system is not overvoltage (i.e., the third determination result indicates no), at this time, the photovoltaic system can be controlled to generate power for the isolated power grid by using the third control method, wherein the third control method can include the maximum power point tracking method and the second control method, and the second control method can be used to control the photovoltaic system to recalculate and output the second active power and the second reactive power.

[0063] In some optional embodiments, the photovoltaic system includes a photovoltaic panel and a two-stage photovoltaic inverter, the two-stage photovoltaic inverter includes a front stage and a rear stage, the front stage is used for DC-DC conversion, and the rear stage is used for AC-DC conversion, the second excitation control on the synchronous generator, and the control of the photovoltaic system in the isolated power grid to generate power for the isolated power grid by using the first control method, includes: performing the first preset excitation control on the synchronous generator to update the first preset voltage to the second preset voltage; performing the second preset excitation control on the synchronous generator to update the second preset voltage to the initial voltage, the second excitation control includes the first preset excitation control and the second preset excitation control; controlling the front stage to track the maximum power point of the photovoltaic panel by using the maximum power point tracking control method; and controlling the rear stage to output the rated active power and the rated reactive power of the two-stage photovoltaic inverter by using the rated power control method, so as to generate power for the isolated power grid.

[0064] First of all, it needs to be clear that the first preset voltage is a positive reference voltage that the synchronous generator increases in order to increase the voltage support for the system in the case that the fault has not been cleared, so as to increase the excitation effect. Then in the above embodiments, since the fault has been cleared, the rear stage circuit can be restored to the rated power control, therefore, during the process of the synchronous generator fault clearing to the maximum power angle swing, the positive reference voltage added during the fault is first maintained. Then during the process of the power angle from the maximum value to the minimum value, the positive reference voltage is cleared and a negative reference voltage is added to prevent the power angle from reversing, i.e., the first preset voltage is updated to the second preset voltage. During the subsequent swing and oscillation calming stage, the normal state is restored, and no additional value is added to the reference voltage, i.e., the second preset voltage is updated to the initial voltage.

[0065] In some optional embodiments, the photovoltaic system comprises a photovoltaic panel and a two-stage photovoltaic inverter, the structure of the two-stage photovoltaic inverter comprises a front stage and a rear stage, the front stage is used for DC-DC conversion, and the rear stage is used for AC-DC conversion. The second control method is used to control the photovoltaic system to generate power for the isolated power grid, comprising: controlling the front stage to use a DC voltage control method to stabilize the DC bus voltage of the photovoltaic system; and controlling the rear stage to use a first power control method to control the two-stage photovoltaic inverter to output a first active power and a first reactive power, so as to generate power for the isolated power grid.

[0066] In the above embodiments, by controlling the front stage to use the DC voltage control method, the maximum power point tracking method control is suspended, so that the DC bus voltage is stabilized. By controlling the rear stage to use the first power control method, the active power and the reactive power of the two-stage photovoltaic inverter are recalculated, so that the two-stage photovoltaic inverter is switched from the rated active power to the first active power, and the two-stage photovoltaic inverter is switched from the rated reactive power to the first reactive power, so as to achieve the purpose of line-of-sight low-voltage ride-through using the new first active power and the first reactive power to generate power for the isolated power grid.

[0067] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the implementation process of the isolated power grid multi-source cooperative fault ride-through method of the present application will be described in detail below in conjunction with specific embodiments.

[0068] The present embodiment relates to a specific isolated power grid multi-source cooperative fault ride-through method, comprising the following steps:

[0069] Step S1: analyze the characteristics of photovoltaic generator sets and fuel generator sets, and establish an isolated power grid model containing photovoltaic power generation, fuel generator excitation control, power plant auxiliary machines and power load;

[0070] Step S2: considering the output characteristics and fault ride-through capability requirements of new energy photovoltaic power generation, the recovery effect of generator excitation throughout the process after system failure, and the low-voltage ride-through capability requirements of power plant auxiliary machine frequency converters, design respective fault ride-through methods;

[0071] Step S3: considering the fault drop depth and the time scale of different fault ride-through control strategies of the power generation unit, the multi-source cooperative switching control method is used to improve the coordinated fault ride-through capability of new energy power generation units and traditional power systems, and ensure safe and reliable operation of the system.

[0072] Among them, considering that the photovoltaic generator set is constrained by power electronic devices and has low overcurrent tolerance, the photovoltaic power generation system can use a two-stage photovoltaic inverter control method. Optionally, the two-stage photovoltaic inverter comprises a front stage circuit and a rear stage circuit, as shown in Figure 3PV is the solar panel in the front-end circuit, g1 is the PWM control signal in the front-end circuit, Vdc is the DC bus voltage, g2 is the PWM control signal in the back-end circuit, L is the filter inductance in the back-end circuit, AC is the alternating current (whose alternating current is , and , AC voltage is , and ).

[0073] Optionally, the front-end circuit adopts a Boost circuit to realize maximum power point tracking (MPPT) control. The front-end control is specifically as shown in Figure 4 , the output voltage U pv and the current i pv of the solar panel are detected, the voltage of the maximum power point of the solar panel can be gradually approached using the Perturb & Observe algorithm (P&O), the duty cycle is obtained, and then the PWM driving signal is obtained by comparison with the triangular carrier. The back-end circuit adopts a virtual synchronous generator control strategy to realize a three-phase grid-connected inverter.

[0074] Optionally, when the system is in a normal condition (i.e., without voltage sag), the control strategy is as shown in Figure 4 , at this time, the control switch is S1, the front-end circuit of the photovoltaic power generation system is used to stabilize the voltage of the DC bus, and the back-end virtual synchronous generator controls the active and reactive power output of the inverter. When the system voltage sags, the front-end Boost circuit is still performing maximum power point tracking, the modulation signal d generated thereby is compared with the carrier to obtain the PWM control signal g1, g1 controls the on-off of the front-end circuit thyristor, the output power of the front-end inverter remains unchanged, the grid-side voltage drops, causing power imbalance of the system, DC bus voltage rise, causing overcurrent protection or overvoltage protection, and thus leading to photovoltaic inverter off-grid. Further, in order to realize fault ride-through of the photovoltaic inverter, the fault voltage sag depth and the DC bus voltage are detected, and the front-end circuit switch is switched to S2, the maximum power point tracking is temporarily suspended, and a constant DC voltage U dc_ref control is adopted, a proportional-integral controller (PI control) is used to ensure the stability of the DC bus voltage according to the control deviation between and U dc_ref . After the fault is removed, the maximum power point tracking reference voltage in the normal working state can be used.Smooth transition; the latter circuit by re-computing the active power and reactive power reference value, the reference power from the rated value to the new power value, so as to realize low voltage penetration with new active, reactive reference power.

[0075] Optionally, due to the relevant photovoltaic grid-connected standard, the inverter needs to meet the specified standard to absorb or emit reactive current to the system during fault, so as to realize the voltage support to the system. The calculation formula of the inverter reactive current reference value during fault is as follows:

[0076] ,

[0077] In the formula, Indicates the system rated voltage, Indicates the system rated current, Indicates the fault drop voltage.

[0078] Optionally, according to the required output of the inverter, the inverter output reactive power reference value can be re-calculated, while the input of the active power is ensured as much as possible. The calculation formula of the active power reference value and the reactive power reference value is as follows:

[0079] ,

[0080] ,

[0081] In the formula, Indicates the inverter output reactive current during fault, Indicates the fault drop voltage, S indicates the system rated capacity, Indicates the rated active power.

[0082] Optionally, in the case that the new energy generator set of the system is in normal working condition, the front stage of the photovoltaic inverter can adopt maximum power tracking control, and the rear stage circuit can change the active power reference value to realize power output change. When the system fails, the front stage circuit appears overvoltage, and the switch can be switched from S1 to S2, as shown in Figure 4 , into DC voltage control; the rear stage circuit can calculate the active power reference value and the reactive power reference value according to the fault voltage condition, so as to maintain the system power balance as much as possible, so that the system can not appear the cut-off operation condition as much as possible, and improve the fault penetration capability.

[0083] Optionally, as shown in Figure 5 , the rear stage control is as follows: voltage and current information is collected from the AC end (AC current is , and , and the AC voltage is​ , and ), then the active power P and the reactive power Q are calculated by dq / abc transformation, when the fault voltage U g The switch is set to S1 by amplitude detection without overvoltage, and the P, Q, f ref , P N , Q N The output voltage amplitude E and phase θ are controlled by VSG. If the amplitude detection overvoltage occurs, the switch is switched to S2, and the P, Q, f ref , P ref , Q ref The new voltage amplitude E and phase θ are generated by VSG control to generate a reference voltage, and the control signal g2 is obtained by inner loop control to realize switch control of the rear stage circuit.

[0084] Specifically, as Figure 6 shown, virtual synchronous generator control is adopted, the synchronous generator frequency modulation and excitation voltage regulation process are simulated, and the synchronous generator swing equation is used to enhance the inertia support of the system. The inverter frequency droop characteristic is used, combined with the virtual inertia regulation characteristic of the synchronous generator to obtain the voltage reference phase of the inverter, and the reactive power-voltage droop characteristic is used to generate the voltage reference amplitude of the inverter, that is, the reference voltage amplitude and phase of the inverter are obtained by using the active power-phase and reactive power-voltage two formulas to realize control, and the power outer loop control is as follows:

[0085] ,

[0086] ,

[0087] In the formula, represents the rated frequency of the system, represents the rated angular velocity of the system, represents the active power and frequency droop coefficient, represents the reactive power and voltage droop coefficient, represents the virtual inertia constant, represents the actual angular velocity change rate of the inverter, represents the reference active power of the inverter, represents the actual output active power of the inverter, represents the actual frequency of the inverter, represents the control voltage amplitude of the inverter, represents the rated voltage reference value, represents the reference reactive power of the inverter, represents the actual output reactive power of the inverter.

[0088] Wherein, considering the voltage characteristics and excitation automatic regulation system of the synchronous generator, the fuel unit can adopt excitation control method, so that reactive power support can be provided in fault ride-through, which has strong anti-disturbance ability, and relative to new energy generator unit limited by power electronic devices, the synchronous generator has stronger short-circuit current capacity and stronger grid support ability.

[0089] Specifically, when the system is in a fault state, the synchronous generator excitation control plays a regulating role and has strong voltage stability. As shown in Figure 7 , the synchronous generator excitation system control structure diagram is Figure 7 , the additional voltage of the excitation control for the fault recovery process is selected according to the reference value of different fault recovery stages; the additional reference voltage of the power system stabilizer is , the terminal voltage of the generator is , and the three are added to form the reference voltage of the control system . The terminal voltage of the generator is detected by the measurement link G R (s) of the excitation controller , and the detected voltage is compared with the reference voltage to obtain the voltage difference . The measurement signal and the reference voltage deviation are solved by the comprehensive amplification unit G A (s) to solve the problem that the circuit cannot work due to small deviation, and then the limiting link is used to prevent the driving signal from being too large to obtain the control voltage . The excitation unit G(s) is controlled to realize the excitation regulation process of the synchronous generator to obtain the voltage output of the synchronous generator .

[0090] Optionally, as shown in Figure 7 , the voltage measurement comparison unit of the synchronous generator excitation system generally ignores the delay of the comparison circuit, and measures the terminal voltage of the synchronous generator in real time , compares the deviation of the terminal voltage from the reference voltage , and the transfer function is generally as follows:

[0091] ,

[0092] In the formula, represents the transfer function of the voltage measurement comparison unit, is the proportional coefficient of the measurement unit, is the time constant of the measurement unit, represents the symbol of complex frequency, which is the expression after Laplace transform.

[0093] Since the measurement signal output by the measurement unit is compared with the reference voltage The bias signal is small, and needs to be amplified by a comprehensive power amplification unit to obtain a power driving signal, as shown in Figure 7 The output signal of the amplification unit needs to pass through a limiting section, and its control model is as follows:

[0094] ,

[0095] In the formula, is the transfer function of the comprehensive amplification unit, is the voltage amplification coefficient, is the amplifier time constant, represents the symbol of complex frequency, and is the expression after Laplace transform.

[0096] By establishing a simple synchronous generator excitation loop mathematical model, ignoring the damping effect in the excitation process, as shown in Figure 7 The excitation unit transfer function is obtained:

[0097] ,

[0098] In the formula, G G (s) is the excitation unit transfer function, is the synchronous motor amplification coefficient, is the synchronous motor response time constant, represents the symbol of complex frequency, and is the expression after Laplace transform.

[0099] Alternatively, the synchronous generator often uses excitation control to ensure stable operation during fault ride-through, in order to improve the ability of the synchronous generator to maintain system stability during fault process, the fault transient process can be divided into five stages according to the power angle relationship of the synchronous generator. Different control strategies are adopted according to the characteristics of each stage, which is beneficial to improve the fault recovery ability of the system. As shown in Figure 7 , is the additional voltage of the excitation control during fault recovery process, is the additional reference voltage of the power system stabilizer, and the specific switching control process is:

[0100] 1) The first stage and the second stage refer to the process from the occurrence of short-circuit fault in the system to the removal of the fault, and then to the power angle swing to the maximum value. In order to enhance the excitation effect of the synchronous generator as quickly as possible in the first two stages, a suitable positive voltage ΔV ref is added to the reference voltage 0 of the automatic voltage regulator (AVR) in the excitation control system at this time, and the switch is switched from S1 to S2.

[0101] 2) The third stage refers to the process from the maximum value of the synchronous generator's power angle to its minimum value. During this process, it is necessary to remove the positive voltage ΔV added to the reference voltage of the automatic voltage regulator. ref The control logic switches from S2 to S3, and an additional negative voltage -ΔV is applied. ref This is to prevent the generator from losing synchronism due to reverse power angle swing.

[0102] 3) Stages 4 and 5 refer to the subsequent oscillation and calming phases of the power angle. During these stages, it is necessary to switch back to S1 control in a timely manner to remove the negative reference voltage -ΔV added during the third stage. ref Meanwhile, the power system stabilizer isolates the multi-source coordinated fault ride-through of the power grid, thereby stabilizing the oscillations as quickly as possible and promoting the entire fault recovery process.

[0103] During a fault, the synchronous generator excitation process needs to quickly increase a positive voltage reference value ΔV. ref To maintain system stability, after a fault is cleared, a negative voltage reference value -ΔV needs to be added to prevent overexcitation from causing a reverse angle. ref During the subsequent oscillation subsidence phase, S1 control should be restored to promote normal system operation.

[0104] In addition to providing power to the grid, traditional fuel-fired power plants typically rely on self-powered auxiliary equipment (such as coal mills and conveyor belts) for critical auxiliary equipment. To achieve speed regulation and economical operation, these auxiliary machines are mostly driven by frequency converters, which impose strict requirements on fault ride-through capability. A sudden voltage drop, overvoltage, or power outage can cause the frequency converter to lock up, and tripping of critical auxiliary equipment can trigger the furnace fire extinguishing protection (MFT) to shut down the unit, potentially leading to generator shutdowns and other serious threats to system stability and safety, resulting in economic losses and personal safety risks. To address the insufficient fault ride-through capability of frequency converters, energy storage units such as batteries can be added to maintain bus voltage stability using active DC compensation. This can be achieved using an "uncontrolled rectifier + battery" structure, as illustrated in the diagram below. Figure 8 As shown.

[0105] like Figure 8 As shown, the auxiliary equipment operates as follows: Under normal operating conditions or when the voltage drops by more than 0.9 pu, the low-voltage ride-through strategy is not activated, and power is supplied by the power plant (phase A voltage u). a Phase B voltage u b and C-phase voltage u c) to the auxiliary machinery M, while the energy storage unit is charged by the uncontrolled rectification (AC / DC) to maintain the battery in the state of saturation charging. When the AC power supply fails and the voltage drops or the power supply is interrupted, the grid voltage drops to 0.9pu or below, the fault ride-through is started, the battery is boosted by the voltage sag protector to supply the DC bus voltage U dc of the frequency converter, and the voltage sag protector automatically returns to the standby state, while the battery is charged to the saturation state.

[0106] Alternatively, the multi-source coordinated fault ride-through control of the isolated grid system can be realized according to the coordination of the new energy photovoltaic power generation and the different fault ride-through strategies of the fuel unit. Since the photovoltaic power generation system is limited by the power electronic device, the voltage support provided by the system during system failure is limited. The synchronous generator has strong short-circuit current resistance due to the regulation of the excitation system, and the system failure has less impact on the synchronous generator unit. Most of the important auxiliary equipment of the thermal power plant is driven by the frequency converter, and once the fault is serious, the auxiliary machinery may be tripped. The system fault voltage drop depth and different generation technology control scales can realize the coordinated switching control strategy. In order to protect the important auxiliary machinery from being blocked and causing fuel unit shutdown accidents, part of the unimportant load can be removed to ensure the safe and reliable operation of the system.

[0107] In summary, in the isolated grid system including the above-mentioned photovoltaic power generation system (control), fuel generator unit (control), auxiliary equipment (control) and power load, as shown in Figure 9 , the specific control method of the fault ride-through can be:

[0108] When the system fails and the fault voltage drops to 0.9pu or below, and if the photovoltaic system (photovoltaic power generation system) is overvoltage (overvoltage), the front stage and circuit are switched to S2 (DC voltage control and new active power and reactive power reference value control). If the photovoltaic system (photovoltaic power generation system) does not have overvoltage, the front stage remains S1 (maximum power point tracking control), and the rear stage is switched to S2 (new active power and reactive power control). At the same time, in order to increase the voltage support of the system, a positive reference voltage is added to the excitation control of the synchronous generator (1 stage) (i.e. the excitation control of the synchronous generator (1 stage) + ΔV ref), and increase the excitation effect. Then, it is judged whether the fault voltage threatens the auxiliary equipment drive. If the fault voltage does not threaten the auxiliary equipment drive (i.e., the fault voltage does not threaten the auxiliary tripping protection (No)), the auxiliary equipment can be temporarily driven by the battery (i.e., battery power supply). Once the auxiliary tripping protection is threatened (Yes), part of the load is removed to ensure the safety and stability of the system.

[0109] As shown in Figure 9 , it is judged whether the fault is cleared. If the fault is cleared, the front stage and the rear stage of the photovoltaic system are switched back to S1 control (the front stage circuit adopts maximum power fault smooth transition under normal working condition, and the rear stage circuit resumes rated power control). The synchronous generator fault is removed to the maximum power angle swing process to maintain the additional positive reference voltage during the fault (i.e., the additional voltage of the synchronous generator excitation control (2 stages) + ΔV ref ). In the process of the power angle from the maximum value to the minimum value, the positive reference voltage is cleared, and the negative reference voltage is increased to prevent the power angle from reversing (i.e., the additional voltage of the synchronous generator excitation control (3 stages) - ΔV ref ). In the subsequent swing and oscillation calming stage, the normal state is restored, and the reference voltage is not added with any value (i.e., the additional voltage of the synchronous generator excitation control (4, 5 stages) is 0). After the fault clearance voltage is restored, the auxiliary equipment restores the normal power supply mode, and charges the battery (battery charging) for the next standby.

[0110] In this embodiment, when the isolated grid system containing a high proportion of new energy photovoltaic power generation and fuel units has a voltage drop due to a system fault, to avoid large-scale off-grid accidents, the fault ride-through control of the photovoltaic system during the fault can be used to support the voltage of the system. The front stage circuit switches the maximum power tracking to maintain the bus voltage balance, and the rear stage circuit recalculates the active and reactive power reference values to achieve power balance. At the same time, after the fault is cleared, to avoid the problem of power angle reversal caused by the additional positive voltage reference of the synchronous generator excitation during the fault, the control needs to be switched to an additional negative voltage in a timely manner, and the system needs to be switched to a normal working state during the subsequent oscillation calming process to play a positive role in restoring the system. The auxiliary equipment of the power plant will also be affected during the fault. Once the voltage is lower than 0.9pu, the energy storage unit supplies power to the frequency converter to maintain the normal operation of the auxiliary equipment. Once the voltage drops too low, part of the non-essential load needs to be removed to ensure the stable operation of the system.

[0111] Exemplarily, the system can be composed of an auxiliary machine, a synchronous generator, a photovoltaic inverter, and a 60MW load. The synchronous generator outputs a voltage of 13.8kV, which is raised to 230kV through a step-up transformer. The photovoltaic inverter outputs a voltage of 380V, which is connected to the system through a transformer, and a fault simulation is performed on the isolated grid system.

[0112] Case1: system in 5s three-phase short-circuit fault, voltage drop to 0.8pu, 5.5s fault clearance, at this time the system voltage as shown in Figure 10 , including the dashed line corresponding to the prior art under normal control of the system voltage and the solid line corresponding to the improved control of the system voltage in the present application, the system power change as shown in Figure 11 , including the dashed line corresponding to the prior art under normal control of the system reactive power and the solid line corresponding to the improved control of the system reactive power in the present application).

[0113] Case2: system in 5s three-phase short-circuit serious fault, fault voltage drop to 0.6pu, 5.5s fault clearance, compared with the fault, in order to prevent auxiliary machine trip, cut off part of the load running under the improved control of the system voltage as shown in Figure 12 , the solid line (as Figure 12 , the dashed line as shown in the prior art under normal control of the system voltage), the system reactive power under the improved control of the cut-off part of the load running as shown in Figure 13 , the solid line (as Figure 13 , the dashed line as shown in the prior art under normal control of the system reactive power).

[0114] It can be seen that Figure 10 after the occurrence of three-phase fault, the voltage drops to 0.8pu, due to the participation of power system stabilizer and synchronous generator excitation link in control, the system has large inertia, the voltage support of the system is strong, in order to maintain voltage stability, the system output reactive power, so that the voltage of the isolated grid system does not drop below 0.9pu, which ensures the stable operation of the system. When a serious three-phase short-circuit fault occurs, the voltage drops seriously, in order to ensure the stable operation of the system and improve the recovery ability after the fault process, the load shedding operation is carried out, through Figure 12 and Figure 13 , it can be seen from the comparison of voltage drop during fault of different control strategies that the voltage support of the system under the control of multi-source coordinated control fault ride-through is better.

[0115] The embodiment of the present application also provides a multi-source collaborative fault ride-through device of isolated power grid. It should be noted that the multi-source collaborative fault ride-through device of isolated power grid of the embodiment of the present application can be used to execute the multi-source collaborative fault ride-through method for isolated power grid provided by the embodiment of the present application. The device is used to realize the above-mentioned embodiment and preferred embodiment, which has been described. As used below, the term "module" can be a combination of software and / or hardware that realizes a predetermined function. Although the device described in the following embodiment is preferably realized in software, the realization of hardware, or the combination of software and hardware, is also possible and conceived.

[0116] The multi-source collaborative fault ride-through device of isolated power grid provided by the embodiment of the present application is introduced below.

[0117] Figure 14 is a schematic diagram of a multi-source cooperative fault ride-through device of an isolated power grid according to an embodiment of the present application. As shown in the figure, the device comprises: Figure 14

[0118] an acquisition module 10, configured to acquire a grid-connected point voltage of the isolated power grid at a first time;

[0119] Specifically, in the case of a fault of an AC power source of the isolated power grid, the grid-connected point voltage of the isolated power grid may appear voltage sag or power supply interruption, thereby causing large-scale off-grid accidents in the isolated power grid. Therefore, the present application first acquires the grid-connected point voltage of the isolated power grid, thereby providing an analysis basis for the fault ride-through method for avoiding large-scale off-grid accidents in the isolated power grid.

[0120] a first judgment module 20, configured to judge whether the grid-connected point voltage is located in a preset voltage range, to obtain a first judgment result;

[0121] Specifically, the grid-connected point voltage in the normal operation of the isolated power grid can be taken as a standard voltage, the minimum voltage in the above-mentioned preset voltage range can be the voltage after the grid-connected point voltage appears sag, and the maximum voltage in the above-mentioned preset voltage range can be the above-mentioned standard voltage. The above-mentioned preset voltage range can be reasonably set by the person skilled in the art according to the actual situation, which is not limited in the present application.

[0122] Optionally, the above-mentioned acquisition step can also be acquiring a grid-connected point voltage sag depth of the grid-connected point voltage in the isolated power grid; and the above-mentioned judgment step can also be judging whether the grid-connected point voltage sag depth is located in a preset sag depth range. The preset sag depth range can be the grid-connected point voltage sag depth allowed to sag, which can be reasonably selected by the person skilled in the art according to the actual situation.

[0123] a first execution module 30, configured to, in the case that the first judgment result indicates no, perform first excitation control on a synchronous generator in the isolated power grid, the first excitation control being used to update an initial voltage of the synchronous generator to a first preset voltage;

[0124] Specifically, the case that the above-mentioned first judgment result indicates no, that is, the grid-connected point voltage in the isolated power grid has sagged.

[0125] ​Optionally, the traditional power generation system has strong anti-disturbance ability and strong support ability for isolated power grid due to the voltage characteristics and excitation automatic regulation system of the synchronous generator. Unlike the new energy generator set (photovoltaic power generation system) which is limited by power electronic devices, the synchronous generator has stronger short-circuit current capacity. Therefore, in the case of sudden drop of the point-of-common coupling voltage, considering the recovery effect of the excitation regulation process of the synchronous generator after the system (isolated power grid) fault, the first excitation control can be performed on the synchronous generator in the isolated power grid to update the initial voltage of the synchronous generator to the first preset voltage, so as to realize the first excitation control of the synchronous generator.

[0126] The second determination module 40 is configured to acquire the point-of-common coupling voltage of the isolated power grid at the second time, and determine whether the point-of-common coupling voltage at the second time is within the preset voltage range, to obtain a second determination result, the point-of-common coupling voltage at the second time being the point-of-common coupling voltage after the first excitation control of the synchronous generator;

[0127] Specifically, after the first excitation control of the synchronous generator, the point-of-common coupling voltage of the isolated power grid, i.e. the point-of-common coupling voltage at the second time, can be acquired again. Then, it can be determined again whether the point-of-common coupling voltage at the second time is within the preset voltage range, to obtain the second determination result indicating yes or no.

[0128] The second execution module 50 is configured to, in the case that the second determination result indicates yes, perform second excitation control on the synchronous generator, and control the photovoltaic system to generate power for the isolated power grid by using the first control method, the second excitation control being configured to update the first preset voltage of the synchronous generator to the initial voltage, and the first control method including a maximum power point tracking method and a rated power control method, the maximum power point tracking method being configured to track the maximum power point of the photovoltaic system, and the rated power control method being configured to control the photovoltaic system to output rated active power and rated reactive power.

[0129] Specifically, in the case that the second determination result indicates yes, it indicates that the fault of the isolated power grid has been cleared, so that the second excitation control can be performed on the synchronous generator to restore the first preset voltage of the synchronous generator to the initial voltage. In addition, since the synchronous generator and the photovoltaic system are used to cooperatively perform fault ride-through in the present application, the first control method including the maximum power point tracking method and the rated power control method is needed to be used to control the photovoltaic system to generate power for the isolated power grid while the second excitation control is performed on the synchronous generator, so as to maintain the balance of the direct-current bus voltage and the balance of the power of the photovoltaic system.

[0130] The third execution module 60 is configured to control the photovoltaic system to generate power for the isolated power grid by using a second control method when the second determination result indicates no, the second control method comprising a direct-current voltage control method and a first power control method, the direct-current voltage control method being used to stabilize the direct-current bus voltage of the photovoltaic system, and the first power control method being used to control the photovoltaic system to output the first active power and the first reactive power.

[0131] Specifically, when the second determination result indicates no, it indicates that the fault of the isolated power grid has not been cleared, so that the application also adopts a fault ride-through method of controlling the photovoltaic system to generate power for the isolated power grid by using the second control method, so as to realize the purpose of the first field control of the synchronous generator and the second control method of the photovoltaic system for the coordinated fault ride-through of the isolated power grid, thereby avoiding the occurrence of a large-area off-grid accident. Optionally, the power generation equipment of the isolated power grid further comprises auxiliary equipment, and when the second determination result indicates yes, the multi-source coordinated fault ride-through device further comprises a first control module configured to control the auxiliary equipment to supply power to the first load, the first load being all loads in the isolated power grid supplied by the auxiliary equipment.

[0132] Optionally, the power generation equipment of the isolated power grid further comprises auxiliary equipment, and when the second determination result indicates no, the multi-source coordinated fault ride-through device further comprises a second control module configured to control the auxiliary equipment to supply power to the second load, the second load being part of all loads in the isolated power grid supplied by the auxiliary equipment.

[0133] Optionally, the power generation equipment of the isolated power grid further comprises auxiliary equipment and a battery, and when the first determination result indicates yes, the multi-source coordinated fault ride-through device further comprises a third control module configured to control the auxiliary equipment to supply power to the third load, the third load being all loads in the isolated power grid supplied by the auxiliary equipment, and control the auxiliary equipment to charge the battery.

[0134] Optionally, when the second determination result indicates no, the multi-source coordinated fault ride-through device further comprises a third determination module configured to determine whether the direct-current bus voltage of the photovoltaic system is overvoltage, to obtain a third determination result; a fourth control module configured to execute the step of controlling the photovoltaic system to generate power for the isolated power grid by using the second control method when the third determination result indicates yes; and the fourth control module is configured to control the photovoltaic system to generate power for the isolated power grid by using a maximum power point tracking method and a second power control method when the third determination result indicates no, the second power control method being used to control the photovoltaic system to output a second active power and a second reactive power.

[0135] Optionally, the photovoltaic system comprises a photovoltaic panel and a two-stage photovoltaic inverter, the two-stage photovoltaic inverter comprises a front stage and a rear stage, the front stage is used for DC-DC conversion for voltage boosting, and the rear stage is used for AC-DC conversion, the second execution module comprises: a first updating unit, configured to perform first preset excitation control on the synchronous generator to update the first preset voltage to the second preset voltage; a second updating unit, configured to perform second preset excitation control on the synchronous generator to update the second preset voltage to the initial voltage, the second excitation control comprises the first preset excitation control and the second preset excitation control; a first control unit, configured to control the front stage to track the maximum power point of the photovoltaic panel by using a maximum power point tracking control method; and a second control unit, configured to control the rear stage to output rated active power and rated reactive power of the two-stage photovoltaic inverter by using a rated power control method, so as to generate power for the isolated power grid.

[0136] Optionally, the photovoltaic system comprises a photovoltaic panel and a two-stage photovoltaic inverter, the structure of the two-stage photovoltaic inverter comprises a front stage and a rear stage, the front stage is used for DC-DC conversion for voltage boosting, and the rear stage is used for AC-DC conversion, the third execution module comprises: a third control unit, configured to control the front stage to stabilize the DC bus voltage of the photovoltaic system by using a DC voltage control method; and a fourth control unit, configured to control the rear stage to output first active power and first reactive power of the two-stage photovoltaic inverter by using a first power control method, so as to generate power for the isolated power grid.

[0137] The multi-source cooperative fault ride-through device for the isolated power grid comprises a processor and a memory, the above-mentioned acquisition module, the first judgment module, the first execution module, the second judgment module, the second execution module and the third execution module are all stored in the memory as program units, and the corresponding functions are realized by the processor executing the above-mentioned program units stored in the memory. The above-mentioned modules are located in the same processor; or the above-mentioned modules are located in different processors in any combination.

[0138] The processor comprises a core, and the core retrieves the corresponding program unit from the memory. The core can be set to one or more, and the problem that the new energy power generation (photovoltaic system) is difficult to be compatible with the traditional power system (synchronous generator) during fault ride-through in the prior art can be solved by adjusting the core parameters.

[0139] The memory can comprise a non-persistent memory in a computer readable medium, a random access memory (RAM) and / or a non-volatile memory such as a read-only memory (ROM) or a flash memory (flash RAM), and the memory comprises at least one memory chip.

[0140] The embodiment of the present application provides a computer readable storage medium, the computer readable storage medium comprises a stored program, wherein the computer readable storage medium controls the device to execute a multi-source cooperative fault ride-through method of an isolated power grid when the program is running.

[0141] The embodiment of the present application provides an electronic device, the device comprises a processor, a memory and a program stored in the memory and executable on the processor, and the processor implements the steps of the multi-source cooperative fault ride-through method of an isolated power grid when executing the program. The device herein can be a server, a PC, a PAD, a mobile phone and the like.

[0142] The present application also provides a computer program product, when executed on a data processing device, is suitable for executing the program initialized with the steps of the multi-source cooperative fault ride-through method of an isolated power grid.

[0143] Obviously, those skilled in the art should understand that the modules or steps of the present application described above can be realized by general computing devices, which can be concentrated on a single computing device or distributed on a network composed of multiple computing devices, which can be realized by program codes executable by computing devices, so that they can be stored in storage devices and executed by computing devices, and in some cases, the steps shown or described can be executed in different order, or they can be manufactured into individual integrated circuit modules, or multiple modules or steps can be manufactured into a single integrated circuit module. Thus, the present application is not limited to any particular hardware and software combination.

[0144] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system or a computer program product. Therefore, the present application can adopt a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware aspects. Moreover, the present application can adopt a computer program product implemented on one or more computer usable storage media containing computer usable program codes (including but not limited to disk storage, CD-ROM, optical storage, etc.).

[0145] The present application is described with reference to flowcharts and / or block diagrams according to the method, device (system) and computer program product of the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be realized by computer program instructions. These computer program instructions can be provided to a general purpose computer, a special purpose computer, an embedded processor or other programmable data processing devices to produce a machine, so that the instructions executed by the computer or other programmable data processing devices produce a device for realizing the functions described in the flowcharts and / or block diagrams. Figure 1 The flow or the combination of multiple flows and / or blocksFigure 1 means for performing the function specified by the block or blocks.

[0146] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a Figure 1 one or more processes and / or blocks Figure 1 means for performing the function specified by the block or blocks.

[0147] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the processes Figure 1 one or more processes and / or blocks Figure 1 means for performing the function specified by the block or blocks.

[0148] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0149] The memory can include non-persistent memory and / or volatile memory, such as a random access memory (RAM) including a cache area for the temporary storage of data. The memory can also include non-volatile memory, such as read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, or non-volatile random access memory (NVRAM), for the storage of information, such as data files or program

[0150] Computer readable media includes permanent and non-permanent, removable and non-removable media implemented in any method or technology for the storage of information. The information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), digital versatile disc (DVD), or other optical storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information accessible to a computing device. According to the definition herein, computer readable media does not include transitory media, such as modulated data signals and carrier waves.

[0151] It is also to be noted that the terms "comprising", "including", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without limitation, an element preceded by "comprises a" does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0152] From the above description, it can be seen that the above-described embodiments of the present application achieve the following technical effects:

[0153] The isolated power grid multi-source cooperative fault ride-through method of the application first obtains the bus voltage of the grid connection point of the isolated power grid, and can obtain a first judgment result by judging whether the grid connection point voltage is within a preset voltage range. In the case of indicating no for the first judgment result, the application first performs first excitation control on the synchronous generator in the isolated power grid, and can obtain a second judgment result by judging whether the power generation equipment in the isolated power grid is normally running. In this step, the first excitation control can be used to update the initial voltage of the synchronous generator to a first preset voltage. Further, in the case of indicating yes for the second judgment result, the application can perform second excitation control on the synchronous generator subjected to the first excitation control, and control the photovoltaic system to generate power for the isolated power grid by using a first control method. In this step, the second excitation control can be used to update the first preset voltage of the synchronous generator to the initial voltage, thereby avoiding the problem that the first preset voltage of the first excitation control of the synchronous generator during the fault causes the power angle to reverse, which plays a positive role in system recovery; the first control method can include a maximum power point tracking method and a rated power control method, wherein the maximum power point tracking method is used to track the maximum power point of the photovoltaic system to maintain the bus voltage balance, and the rated power control method is used to control the photovoltaic system to output rated active power and rated reactive power to achieve power balance. In addition, in the case of indicating no for the second judgment result, the application can control the photovoltaic system to generate power for the isolated power grid by using a second control method. In this step, the second control method can include the above-mentioned maximum power point tracking method and first power control method, and for the same reason, the maximum power point tracking method is used to track the maximum power point of the photovoltaic system to maintain the direct current bus voltage balance of the photovoltaic system, and the first power control method is used to control the photovoltaic system to output first active power and first reactive power, i.e. to achieve power balance by recalculating the first active power and first reactive power of the photovoltaic system. That is, through the application, the fault ride-through of the synchronous generator and the photovoltaic system can be synergistically affected, and large-scale grid separation accidents in the isolated power grid can be avoided, thereby solving the problem in the prior art that new energy power generation (photovoltaic system) is difficult to be compatible with traditional power systems (synchronous generators) during fault ride-through.

[0154] The above only describes the preferred embodiments of the application and is not intended to limit the application. Those skilled in the art can make various changes and modifications to the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A multi-source cooperative fault ride-through method for an isolated power grid, characterized in that, The method comprises: acquiring a grid-connected point voltage of the isolated power grid at a first time point; determining whether the grid-connected point voltage is within a preset voltage range to obtain a first determination result; in a case where the first determination result indicates no, performing first excitation control on a synchronous generator in the isolated power grid, the first excitation control being used to update an initial voltage of the synchronous generator to a first preset voltage; acquiring a grid-connected point voltage of the isolated power grid at a second time point, and determining whether the grid-connected point voltage at the second time point is within the preset voltage range to obtain a second determination result, the grid-connected point voltage at the second time point being the grid-connected point voltage after the first excitation control is performed on the synchronous generator; in a case where the second determination result indicates yes, performing second excitation control on the synchronous generator, and controlling a photovoltaic system in the isolated power grid to generate power for the isolated power grid by using a first control method, the second excitation control being used to update the first preset voltage of the synchronous generator to the initial voltage, the first control method comprising a maximum power point tracking method and a rated power control method, the maximum power point tracking method being used to track a maximum power point of the photovoltaic system, and the rated power control method being used to control the photovoltaic system to output rated active power and rated reactive power; in a case where the second determination result indicates no, controlling the photovoltaic system to generate power for the isolated power grid by using a second control method, the second control method comprising a direct-current voltage control method and a first power control method, the direct-current voltage control method being used to stabilize a direct-current bus voltage of the photovoltaic system, and the first power control method being used to control the photovoltaic system to output first active power and first reactive power, the power generation equipment of the isolated power grid further comprises auxiliary equipment, and in the case where the second determination result indicates yes, the multi-source cooperative fault ride-through method further comprises: controlling the auxiliary equipment to supply power to a first load, the first load being all loads in the isolated power grid that are supplied with power by using the auxiliary equipment.

2. The multi-source co-ordinated fault ride-through method of claim 1, wherein, the power generation equipment of the isolated power grid further comprises auxiliary equipment, and in the case where the second determination result indicates no, the multi-source cooperative fault ride-through method further comprises: controlling the auxiliary equipment to supply power to a second load, the second load being part of all loads in the isolated power grid that are supplied with power by using the auxiliary equipment.

3. The multi-source co-ordinated fault ride-through method of claim 1, wherein, the power generation equipment of the isolated power grid further comprises auxiliary equipment and a battery, and in the case where the first determination result indicates yes, the multi-source cooperative fault ride-through method further comprises: controlling the auxiliary equipment to supply power to a third load, the third load being all loads in the isolated power grid that are supplied with power by using the auxiliary equipment, and controlling the auxiliary equipment to charge the battery.

4. The multi-source co-ordinated fault ride-through method of any one of claims 1 to 3, wherein, in the case where the second determination result indicates no, the multi-source cooperative fault ride-through method further comprises: determining whether a direct-current bus voltage of the photovoltaic system is overvoltage to obtain a third determination result; In the case where the third determination result indicates yes, a step of controlling the photovoltaic system to generate power for the isolated power grid by using the second control method is performed; In the case where the third determination result indicates no, a third control method is used to control the photovoltaic system to generate power for the isolated power grid, the third control method comprising the maximum power point tracking method and a second power control method, the second power control method being used to control the photovoltaic system to output second active power and second reactive power.

5. The multi-source co-ordinated fault ride-through method of any one of claims 1 to 3, wherein, The photovoltaic system comprises photovoltaic cell panels and a two-stage photovoltaic inverter, the two-stage photovoltaic inverter comprising a front stage and a rear stage, the front stage being used for step-up DC-DC conversion, and the rear stage being used for AC-DC conversion, the synchronous generator is subjected to second excitation control, and the photovoltaic system in the isolated power grid is controlled to generate power for the isolated power grid by using a first control method, comprising: The synchronous generator is subjected to first preset excitation control to update the first preset voltage to a second preset voltage; The synchronous generator is subjected to second preset excitation control to update the second preset voltage to the initial voltage, the second excitation control comprising the first preset excitation control and the second preset excitation control; The front stage is controlled to track the maximum power point of the photovoltaic cell panel by using the maximum power point tracking control method; The rear stage is controlled to control the two-stage photovoltaic inverter to output the rated active power and the rated reactive power by using the rated power control method, so as to generate power for the isolated power grid.

6. The multi-source co-ordinated fault ride-through method of any one of claims 1 to 3, wherein, The photovoltaic system comprises photovoltaic cell panels and a two-stage photovoltaic inverter, the structure of the two-stage photovoltaic inverter comprising a front stage and a rear stage, the front stage being used for step-up DC-DC conversion, and the rear stage being used for AC-DC conversion, the photovoltaic system is controlled to generate power for the isolated power grid by using a second control method, comprising: The front stage is controlled to stabilize the DC bus voltage of the photovoltaic system by using the DC voltage control method; The rear stage is controlled to control the two-stage photovoltaic inverter to output the first active power and the first reactive power by using the first power control method, so as to generate power for the isolated power grid.

7. A multi-source cooperative fault ride-through device for an isolated power grid, characterized in that, Comprise: An acquisition module is configured to acquire a grid-connected point voltage of the isolated power grid at a first time; A first determination module is configured to determine whether the grid-connected point voltage is within a preset voltage range, to obtain a first determination result; A first execution module is configured to, in the case where the first determination result indicates no, perform first excitation control on a synchronous generator in the isolated power grid, the first excitation control being used to update an initial voltage of the synchronous generator to a first preset voltage; A second determination module is configured to acquire a grid-connected point voltage of the isolated power grid at a second time, and determine whether the grid-connected point voltage at the second time is within the preset voltage range, to obtain a second determination result, the second time being after the first excitation control is performed on the synchronous generator; a second execution module, configured to, when the second determination result indicates yes, perform second excitation control on the synchronous generator, and control a photovoltaic system in the isolated power grid to generate power for the isolated power grid by using a first control method, the second excitation control being used to update the first preset voltage of the synchronous generator to the initial voltage, the first control method including a maximum power point tracking method and a rated power control method, the maximum power point tracking method being used to track a maximum power point of the photovoltaic system, and the rated power control method being used to control the photovoltaic system to output rated active power and rated reactive power; a third execution module, configured to, when the second determination result indicates no, control the photovoltaic system to generate power for the isolated power grid by using a second control method, the second control method including a direct-current voltage control method and a first power control method, the direct-current voltage control method being used to stabilize a direct-current bus voltage of the photovoltaic system, and the first power control method being used to control the photovoltaic system to output first active power and first reactive power, the power generation device of the isolated power grid further includes auxiliary machine equipment, and when the second determination result indicates yes, the multi-source cooperative fault ride-through apparatus further includes a first control module, configured to control the auxiliary machine equipment to supply power to first loads, the first loads being all loads in the isolated power grid that are supplied with power by using the auxiliary machine equipment.

8. A computer-readable storage medium, characterized in that, The computer readable storage medium includes a stored program, wherein the program, when executed, controls a device in which the computer readable storage medium is located to perform the multi-source cooperative fault ride-through method of the isolated power grid according to any one of claims 1 to 6.

9. An electronic device, comprising: comprise: one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include a program for performing the multi-source cooperative fault ride-through method of the isolated power grid according to any one of claims 1 to 6.

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