DC fault self-clearing method and device for sending terminal system of new energy island power grid

Abstract

The application relates to a DC fault self-clearing method, device and equipment of a new energy island power grid sending end system. After a DC fault of the new energy island power grid sending end system occurs, an AC / DC decoupling control strategy with AC voltage droop optimization control is adopted for the sending end flexible DC converter station to maximize the smooth improvement of the AC voltage within a feasible range. In cooperation with the over-throw strategy of the AC energy consumption device, the absorption of the surplus power of the new energy island power grid is realized, the problem of AC voltage drop at the moment of energy consumption resistor input, the problem of surplus energy surge into the flexible DC valve to cause the overvoltage blocking of the sub-module capacitor are solved, the DC side of the new energy island power grid sending end system is not blocked under the fault, the DC fault is self-cleared, the number of full-bridge modules required by the full / half-bridge hybrid flexible DC valve in the sending end flexible DC converter station is minimized, the overall cost and volume of the new energy island power grid sending end system are reduced, and the power regulation capacity and system stability of the new energy island power grid sending end system are improved.

Description

Technical Field

[0001] This application relates to the field of new energy power transmission technology, and in particular to a method, apparatus and equipment for self-clearing DC faults in a new energy islanded power grid sending-end system. Background Technology

[0002] Most new energy bases are built in remote areas, where the load level of new energy transmission systems is low and the grid structure is weak, resulting in a significant need for stable transmission of new energy from isolated islands. Flexible DC transmission, with its flexibility, controllability, and high efficiency, is one of the important power transmission methods for new energy. For the sending end of the new energy transmission system, flexible DC converters can provide a stable AC voltage for the new energy electric field, can operate in islanded mode, and can provide fast and dynamic compensation to reduce the risk of new energy units disconnecting from the grid, thereby improving the utilization rate of new energy.

[0003] DC fault ride-through technology is a key technology to consider when applying flexible DC transmission systems to new scenarios of large-scale onshore renewable energy development and long-distance transmission. Current DC fault ride-through technologies still face several technical challenges: First, the energy storage capacity of the converter valve submodules in flexible DC transmission systems is relatively small, resulting in weak overcurrent and overvoltage capabilities. During a DC fault in the flexible DC transmission system, the new energy power regulation capability is weak and slow, making it difficult to quickly and significantly resolve the energy imbalance between the AC and DC sides. Second, at longer distances, when a fault occurs at the far end of the line, the energy-consuming devices of the flexible DC transmission system receive the fault signal. The longer communication time for fault command input, the more likely surplus power from isolated renewable energy sources will flood into the converter valves of the flexible DC transmission system, potentially causing module overvoltage issues. Thirdly, larger capacity overhead lines reduce the arc-extinguishing speed, and the flexible DC converter station in the flexible DC transmission system uses full-bridge output negative voltage for arc extinguishing, increasing the risk of module overvoltage in the flexible DC converter station. Fourthly, for large-scale renewable energy islands, when a DC fault occurs in the flexible DC transmission system, the simultaneous input of its large-capacity AC power consumption causes AC voltage drops, affecting the absorption of surplus energy by its power consumption devices, and the influx of more energy into the flexible DC valve modules can easily cause module overvoltage. Summary of the Invention

[0004] This application provides a method, apparatus, and equipment for self-clearing DC faults in a renewable energy islanded power grid sending-end system. It is applied to the renewable energy islanded power grid sending-end system to solve the technical problems of energy imbalance and overvoltage in existing flexible DC transmission systems applied to renewable energy.

[0005] To achieve the above objectives, the embodiments of this application provide the following technical solutions:

[0006] A method for self-clearing DC faults in a renewable energy islanded power grid sending-end system is provided. The method is applied to the renewable energy islanded power grid sending-end system, which includes an AC bus, a renewable energy islanded power grid connected to the AC bus, a sending-end flexible DC converter station, and an AC energy dissipation device. The method includes the following steps:

[0007] Configure the sending-end flexible DC converter station of the new energy island power grid sending-end system with AC-DC decoupling control strategy with AC voltage droop optimization control;

[0008] Acquire DC fault signals and the configuration number and power parameters of AC energy-consuming devices in the sending-end system of the new energy island grid. The power parameters include the rated capacity of the sending-end flexible DC converter station, the power output of the new energy island grid before the fault, and the capacity of each AC energy-consuming device.

[0009] According to the DC fault signal, the current of the DC current controller of the AC-DC decoupling control strategy is switched to 0. At the same time, according to the DC fault signal, the AC energy consumption device is controlled to adopt the over-feed strategy to absorb the surplus power of the islanded grid, so as to eliminate the fault of the sending end system of the new energy islanded grid.

[0010] Preferably, before controlling the AC energy-consuming device to absorb the surplus power of the islanded power grid using the over-discharge strategy according to the DC fault signal, the method includes: determining the number of AC energy-consuming devices to be put into operation to absorb the surplus power of the islanded power grid according to the power parameters using the formula for calculating the number of energy-consuming groups;

[0011] The formula for calculating the number of energy-consuming groups is:

[0012]

[0013] In the formula, n is the number of AC energy-consuming devices, and P XS P represents the power output of the isolated renewable energy grid before the fault. HR The capacity of the AC power consumption device in each group.

[0014] Preferably, the DC fault self-clearing method of the new energy islanded grid sending-end system includes: if the fault of the new energy islanded grid sending-end system is cleared, the DC voltage controller using the AC / DC decoupling control strategy restores the DC voltage of the new energy islanded grid sending-end system; and the AC energy-consuming devices that absorb the surplus power of the islanded grid are disconnected one by one by the sending-end flexible DC converter station to restore the DC current of the new energy islanded grid sending-end system, so that the new energy islanded grid sending-end system can achieve fault restart.

[0015] Preferably, controlling the AC energy-consuming device to absorb surplus power from the islanded power grid according to the DC fault signal includes: controlling the AC energy-consuming device to absorb surplus power from the islanded power grid while controlling the operation of the AC voltage droop optimization controller in the AC / DC decoupling control strategy to increase the AC side voltage of the sending-end flexible DC converter station until the full-bridge submodule capacitor voltage in the sending-end flexible DC converter station reaches a preset value, and then stopping the operation of the AC voltage droop optimization controller.

[0016] Preferably, the acquisition of DC fault signals and the configuration number of AC energy-consuming devices in the sending-end system of the new energy islanded power grid includes: obtaining the configuration number of the corresponding AC energy-consuming devices by using the configuration number calculation formula based on the rated capacity of the sending-end flexible DC converter station and the capacity of each group of AC energy-consuming devices according to the power parameters;

[0017] The formula for calculating the number of configuration groups is:

[0018]

[0019] In the formula, N is the number of configuration groups, and P SE For the rated capacity of the sending-end flexible DC converter station, P HR The capacity of the AC power consumption device in each group.

[0020] This application also provides a DC fault self-clearing device for a new energy islanded grid sending-end system, which is applied to the new energy islanded grid sending-end system. The new energy islanded grid sending-end system includes an AC bus and a new energy islanded grid, a sending-end flexible DC converter station and an AC energy consumption device connected to the AC bus. The DC fault self-clearing device for the new energy islanded grid sending-end system includes a strategy configuration module, a data acquisition module and a fault clearing control module.

[0021] The strategy configuration module is used to configure an AC / DC decoupling control strategy with AC voltage droop optimization control for the sending-end flexible DC converter station of the new energy island grid sending-end system.

[0022] The data acquisition module is used to acquire DC fault signals and the configuration number and power parameters of AC energy-consuming devices in the sending-end system of the new energy island grid. The power parameters include the rated capacity of the sending-end flexible DC converter station, the power output of the new energy island grid before the fault, and the capacity of each AC energy-consuming device.

[0023] The fault clearing control module is used to control the current of the DC current controller of the AC-DC decoupling control strategy to switch to 0 according to the DC fault signal, and at the same time, control the AC energy consumption device to adopt the over-feed strategy to absorb the surplus power of the islanded grid according to the DC fault signal, so as to eliminate the fault of the sending end system of the new energy islanded grid.

[0024] Preferably, the DC fault self-clearing device of the new energy islanded grid sending-end system includes a restart module. The restart module is used to restore the DC voltage of the new energy islanded grid sending-end system by using the DC voltage controller of the AC-DC decoupling control strategy after the fault of the new energy islanded grid sending-end system is cleared; and to restore the DC current of the new energy islanded grid sending-end system by disconnecting the AC energy-consuming devices that absorb the surplus power of the islanded grid one by one through the sending-end flexible DC converter station, so as to enable the new energy islanded grid sending-end system to achieve fault restart.

[0025] Preferably, the fault clearing control module is also used to control the AC energy dissipation device to absorb the surplus power of the islanded power grid while controlling the operation of the AC voltage droop optimization controller in the AC-DC decoupling control strategy, so as to improve the AC side voltage of the sending-end flexible DC converter station until the full-bridge submodule capacitor voltage in the sending-end flexible DC converter station reaches the preset value, and then stop the operation of the AC voltage droop optimization controller.

[0026] Preferably, the data acquisition module is further configured to obtain the configuration number of the corresponding AC energy consumption device based on the rated capacity of the sending-end flexible DC converter station and the capacity of each group of AC energy consumption devices using a configuration group calculation formula.

[0027] The formula for calculating the number of configuration groups is:

[0028]

[0029] In the formula, N is the number of configuration groups, and P SE For the rated capacity of the sending-end flexible DC converter station, P HR The capacity of the AC power consumption device in each group.

[0030] This application also provides a storage device storing a plurality of program codes, the program codes being adapted to be loaded and run by a processor to execute the above-described method for self-clearing DC faults in a renewable energy islanded grid sending-end system.

[0031] This application also provides a terminal device, including a processor and a memory;

[0032] The memory is used to store program code and transmit the program code to the processor;

[0033] The processor is used to execute the DC fault self-clearing method for the sending-end system of the new energy islanded power grid as described above, according to the instructions in the program code.

[0034] As can be seen from the above technical solutions, the embodiments of this application have the following advantages: The DC fault self-clearing method, device, and equipment of the new energy islanded power grid sending-end system are applied to the new energy islanded power grid sending-end system, which includes an AC bus and a new energy islanded power grid connected to the AC bus, a sending-end flexible DC converter station, and AC energy-consuming devices. The method includes configuring an AC / DC decoupling control strategy with AC voltage droop optimization control for the sending-end flexible DC converter station of the new energy islanded power grid sending-end system; acquiring the DC fault signal and the configuration number and power parameters of the AC energy-consuming devices in the new energy islanded power grid sending-end system, including the rated capacity of the sending-end flexible DC converter station, the power output of the new energy islanded power grid before the fault, and the capacity of each group of AC energy-consuming devices; controlling the current of the DC current controller of the AC / DC decoupling control strategy to switch to 0 according to the DC fault signal, and simultaneously controlling the AC energy-consuming devices to adopt an over-feeding strategy to absorb the surplus power of the islanded power grid according to the DC fault signal, so as to eliminate the fault in the new energy islanded power grid sending-end system. This self-clearing method for DC faults in the sending-end system of a renewable energy islanded power grid employs an AC / DC decoupling control strategy for the flexible DC converter station at the sending end after a DC fault occurs. This allows the AC voltage to rise smoothly to the maximum extent within feasible limits, accelerating the absorption of surplus power from the renewable energy islanded power grid by the AC energy-consuming devices. It solves the technical problem of AC voltage drop at the moment of energy-consuming resistor connection, causing surplus energy to surge into the flexible DC valve in the sending-end flexible DC converter station and resulting in overvoltage blocking of the submodule capacitor. It also achieves self-clearing of DC faults on the DC side without blocking under fault conditions in the sending-end system of the renewable energy islanded power grid, and minimizes the number of full-bridge modules required for the full-half-bridge hybrid flexible DC valve in the sending-end flexible DC converter station. This reduces the overall cost and volume of the renewable energy islanded power grid sending-end system, improves the power regulation capability and system stability of the renewable energy islanded power grid sending system, and solves the technical problems of energy imbalance and overvoltage in existing flexible DC transmission systems applied to renewable energy. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a flowchart illustrating the steps of the DC fault self-clearing method for the sending-end system of a new energy islanded power grid as described in the embodiments of this application.

[0037] Figure 2This is an electrical framework diagram of the new energy islanded grid sending-end system in the DC fault self-clearing method of the new energy islanded grid sending-end system described in the embodiments of this application;

[0038] Figure 3 This is a framework diagram of the control strategy for the sending-end system of the new energy islanded power grid in the DC fault self-clearing method of the sending-end system of the new energy islanded power grid described in the embodiments of this application;

[0039] Figure 4 This is a framework diagram of the DC fault self-clearing device for the sending-end system of the new energy islanded power grid described in the embodiments of this application. Detailed Implementation

[0040] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0041] This application provides a method, apparatus, and equipment for self-clearing DC faults in a renewable energy islanded power grid sending-end system. It is applied to the renewable energy islanded power grid sending-end system and solves the technical problems of energy imbalance and overvoltage in existing flexible DC transmission systems applied to renewable energy.

[0042] Example 1:

[0043] Figure 1 This is a flowchart illustrating the steps of the DC fault self-clearing method for a new energy islanded power grid sending-end system described in this application embodiment. Figure 2 This is an electrical framework diagram of the new energy islanded grid sending-end system in the DC fault self-clearing method of the new energy islanded grid sending-end system described in the embodiments of this application. Figure 3 This is a framework diagram of the control strategy for the sending-end system of the new energy islanded power grid in the DC fault self-clearing method of the sending-end system of the new energy islanded power grid described in the embodiments of this application.

[0044] like Figure 2 As shown, this application provides a DC fault self-clearing method for a new energy islanded grid sending-end system, which is applied to the new energy islanded grid sending-end system. The new energy islanded grid sending-end system includes an AC bus 10 and a new energy islanded grid 20, a sending-end flexible DC converter station 30, and N sets of AC energy consumption devices 40 connected to the AC bus 10.

[0045] It should be noted that the new energy islanded grid 20 is connected to the sending-end flexible DC converter station 30 through the three-phase AC bus 10. The AC energy dissipation device 40 is connected at the AC bus connecting the sending-end flexible DC converter station 30 and the new energy islanded grid 20. The AC energy dissipation device 40 is used to dissipate the continuous active power output of the electric field of the new energy islanded grid 20 when the active power transmission channel of the DC line is blocked, so as to avoid overvoltage problems caused by energy accumulation on the sending-end AC feeder.

[0046] like Figure 1 As shown, the DC fault self-clearing method of the sending-end system of the new energy islanded power grid includes the following steps:

[0047] S1. Configure the sending-end flexible DC converter station of the new energy islanded power grid with AC voltage droop optimization control as an AC-DC decoupling control strategy.

[0048] It should be noted that step S1 mainly involves configuring control strategies for the sending-end flexible DC converter station of the new energy islanded power grid sending-end system.

[0049] Furthermore, the AC-DC decoupling control strategy configured in the sending-end flexible DC converter station is as follows: the AC side of the sending-end flexible DC converter station adopts a dual closed-loop constant AC voltage-frequency control with an AC voltage droop optimization controller, and the DC side of the sending-end flexible DC converter station adopts DC voltage control.

[0050] It should be noted that the sending-end flexible DC converter station of this new energy islanded power grid adopts a hybrid full-bridge and half-bridge topology. The negative voltage output capability of the full-bridge module of the sending-end flexible DC converter station can achieve AC / DC decoupling control. In this embodiment, as... Figure 3 As shown, the AC side of the sending-end flexible DC converter station adopts a dual-closed-loop constant AC voltage-frequency (VF) control strategy to provide stable voltage and frequency for the new energy islanded grid. The DC side of the sending-end flexible DC converter station adopts a DC current control strategy. When the sending-end flexible DC converter station detects an increase in the DC port current, the DC current controller of the DC current control strategy automatically reduces the DC voltage bias. At this time, the full-bridge module of the sending-end flexible DC converter station outputs a negative level to reduce the current to zero, thereby achieving the purpose of actively clearing DC faults.

[0051] S2. Obtain the DC fault signal and the configuration number and power parameters of the AC energy-consuming devices in the sending-end system of the new energy islanded grid. The power parameters include the rated capacity of the sending-end flexible DC converter station, the power output of the new energy islanded grid before the fault, and the capacity of each AC energy-consuming device.

[0052] It should be noted that in step S2, the DC fault signal indicating a fault has occurred in the sending-end system of the new energy islanded power grid, as well as the power parameters of the sending-end system, are obtained. In this embodiment, the signal indicating a fault has occurred on the DC line in the sending-end system of the new energy islanded power grid is used as the DC fault signal.

[0053] S3. Based on the DC fault signal, the DC current controller of the AC-DC decoupling control strategy is switched to 0. At the same time, based on the DC fault signal, the AC energy consumption device is controlled to adopt the over-transfer strategy to absorb the surplus power of the islanded grid, so as to eliminate the fault of the sending end system of the new energy islanded grid.

[0054] It should be noted that in step S3, the control strategy of the sending-end system of the new energy islanded grid is mainly based on the DC fault signal to eliminate the fault. In this embodiment, the current command value of the DC current controller of the sending-end flexible DC converter station is switched from the preset value to 0, and the DC current of the sending-end flexible DC converter station quickly drops to zero, realizing direct control of DC voltage, outputting negative DC voltage, and actively clearing the DC fault. According to the DC fault signal, after receiving the operation command, the AC energy consumption device of the sending-end system of the new energy islanded grid immediately adopts the over-connection strategy to absorb the surplus power of the new energy islanded grid. Among them, considering that the port voltage of the sending-end system of the new energy islanded grid will drop instantly during the operation of the AC energy consumption device, affecting the energy absorption, and considering that the energy consumption resistor needs a certain amount of time to absorb energy, in order to avoid the surplus energy flowing into the flexible DC valve of the sending-end flexible DC converter station and causing module overvoltage, the number of AC energy consumption devices connected is required to be greater than the power sent out by the new energy islanded grid before the fault, which is the over-connection strategy.

[0055] In this embodiment of the application, before the AC energy-consuming device is controlled to absorb the surplus power of the islanded power grid using an over-investment strategy according to the DC fault signal, the DC fault self-clearing method of the new energy islanded power grid sending end system includes: determining the number of AC energy-consuming devices to be invested to absorb the surplus power of the islanded power grid according to the power parameters using the formula for calculating the number of invested energy-consuming devices.

[0056] It should be noted that the number of AC energy-consuming devices to be put into operation to absorb the surplus power of the isolated renewable energy grid is calculated using the formula based on the power output of the isolated grid before the power failure and the capacity of each AC energy-consuming device. The formula for calculating the number of energy-consuming devices to be put into operation is as follows:

[0057]

[0058] In the formula, n is the number of AC energy-consuming devices, and P is the number of AC energy-consuming devices. XS P represents the power output of the isolated renewable energy grid before the fault. HRThe capacity of each group of AC energy-consuming devices is defined. In this embodiment, at least one additional group of AC energy-consuming devices is activated based on the DC fault signal to absorb the surplus power of the isolated power grid, thereby eliminating the fault in the sending-end system of the renewable energy isolated power grid.

[0059] Furthermore, the control of the AC energy dissipation device to absorb the surplus power of the islanded grid according to the DC fault signal includes: controlling the AC energy dissipation device to absorb the surplus power of the islanded grid while controlling the operation of the AC voltage droop optimization controller in the AC-DC decoupling control strategy to increase the AC side voltage of the sending-end flexible DC converter station until the full-bridge submodule capacitor voltage in the sending-end flexible DC converter station reaches the preset value, and then stopping the operation of the AC voltage droop optimization controller.

[0060] It should be noted that while controlling the AC energy dissipation device to absorb surplus power from the islanded grid, controlling the operation of the AC voltage droop optimization controller in the AC / DC decoupling control strategy can maximize the AC side voltage of the sending-end flexible DC converter station, accelerating the absorption of surplus energy from the new energy islanded grid by the AC energy dissipation device. As the AC energy dissipation device absorbs energy, the full-bridge submodule capacitor voltage of the sending-end flexible DC converter station briefly rises and then gradually decreases. When it reaches a preset value, the operation of the AC voltage droop optimization controller stops (i.e., there is no signal input at the enable signal terminal of the AC voltage droop optimization controller). In this embodiment, as... Figure 3 As shown, while the AC energy-consuming device is put into operation in the sending-end system of the new energy island grid, the AC voltage droop optimization controller in the AC-DC decoupling control strategy is activated (the enable signal control terminal of the AC voltage droop optimization controller is triggered). At this time, the enable control terminal of the voltage control outer loop d-axis (q-axis controls 0) of the fixed AC voltage-frequency control is triggered based on the capacitor voltage of the sub-module in the sending-end flexible DC converter station. The AC voltage command value of the AC voltage droop optimization controller changes from the preset value to follow the change of the average voltage of the full-bridge sub-module of the flexible DC valve in the sending-end flexible DC converter station. In the case of a DC fault occurring in the sending-end system of a renewable energy islanded power grid, the lack of AC energy dissipation devices prevents the instantaneous absorption of all surplus power from the renewable energy islanded power grid in the sending-end system. This causes energy to surge into the full-bridge module of the sending-end flexible DC converter station. Especially for ultra-long-distance transmission systems, the energy on the line is even greater, and the voltage of the full-bridge module of the flexible DC valve in the sending-end flexible DC converter station rises rapidly. It is necessary to quickly absorb the surplus power after the AC energy dissipation device is put into operation to prevent energy from continuing to surge into the full-bridge module of the flexible DC valve in the sending-end flexible DC converter station and causing overvoltage.

[0061] In this embodiment, the VF control strategy for the sending-end flexible DC converter station enables optimized control of AC voltage droop based on the capacitor voltage of the submodule in the sending-end flexible DC converter station. This allows the AC voltage of the sending-end flexible DC converter station to be smoothly increased to the maximum extent within feasible limits, accelerating the absorption of surplus power from the renewable energy island grid by the AC energy-consuming device. At the same time, combined with the over-connection strategy of the AC energy-consuming device, it solves the technical problem of AC voltage drop at the moment of connecting the energy-consuming resistor, causing surplus energy to surge into the flexible DC valve in the sending-end flexible DC converter station and causing overvoltage lockout of the submodule capacitor.

[0062] This application provides a self-clearing method for DC faults in a renewable energy islanded grid sending-end system. The method is applied to the sending-end system of a renewable energy islanded grid, which includes an AC bus, a renewable energy islanded grid connected to the AC bus, a sending-end flexible DC converter station, and AC energy-consuming devices. The method includes configuring the sending-end flexible DC converter station of the renewable energy islanded grid sending-end system with an AC / DC decoupling control strategy featuring optimized AC voltage droop control; acquiring DC fault signals and the configuration number and power parameters of the AC energy-consuming devices in the renewable energy islanded grid sending-end system. The power parameters include the rated capacity of the sending-end flexible DC converter station, the power transmitted from the renewable energy islanded grid before the fault, and the capacity of each group of AC energy-consuming devices; controlling the current controller of the AC / DC decoupling control strategy to switch to 0 based on the DC fault signal; and simultaneously controlling the AC energy-consuming devices to adopt an over-feeding strategy to absorb surplus power from the islanded grid, thereby eliminating the fault in the renewable energy islanded grid sending-end system. This self-clearing method for DC faults in the sending-end system of a renewable energy islanded power grid employs an AC / DC decoupling control strategy for the flexible DC converter station at the sending end after a DC fault occurs. This allows the AC voltage to rise smoothly to the maximum extent within feasible limits, accelerating the absorption of surplus power from the renewable energy islanded power grid by the AC energy-consuming devices. It solves the technical problem of AC voltage drop at the moment of energy-consuming resistor connection, causing surplus energy to surge into the flexible DC valve in the sending-end flexible DC converter station and resulting in overvoltage blocking of the submodule capacitor. It also achieves self-clearing of DC faults on the DC side without blocking under fault conditions in the sending-end system of the renewable energy islanded power grid, and minimizes the number of full-bridge modules required for the full-half-bridge hybrid flexible DC valve in the sending-end flexible DC converter station. This reduces the overall cost and volume of the renewable energy islanded power grid sending-end system, improves the power regulation capability and system stability of the renewable energy islanded power grid sending system, and solves the technical problems of energy imbalance and overvoltage in existing flexible DC transmission systems applied to renewable energy.

[0063] It should be noted that by adopting the DC fault self-clearing method of the new energy island grid sending-end system, the AC voltage droop optimization controller in the AC-DC decoupling control strategy controls the sending-end flexible DC converter station without switching the control strategy. This allows the AC side voltage of the sending-end flexible DC converter station to change smoothly with the voltage changes of its sub-modules, without causing a sudden voltage / current surge in the new energy island grid sending-end system.

[0064] In one embodiment of this application, the DC fault self-clearing method of the sending-end system of the new energy islanded grid includes: after the fault of the sending-end system of the new energy islanded grid is cleared, a DC voltage controller using an AC / DC decoupling control strategy restores the DC voltage of the sending-end system of the new energy islanded grid; and by disconnecting the AC energy-consuming devices that absorb the surplus power of the islanded grid one by one through the sending-end flexible DC converter station, the DC current of the sending-end system of the new energy islanded grid is restored, so that the sending-end system of the new energy islanded grid can achieve fault restart.

[0065] It should be noted that after the DC current of the sending-end system of the new energy islanded grid drops to zero and the arc is extinguished, the DC voltage is maintained at 0 for deionization. When the deionization time is reached, the fault of the sending-end system of the new energy islanded grid is eliminated. In this embodiment, after the fault of the sending-end system of the new energy islanded grid is eliminated, the sending-end flexible DC converter station restores the slope of the DC reference value input to the DC current controller of the faulty pole, restores the DC voltage of the sending-end system of the new energy islanded grid, and the sending-end flexible DC converter station disconnects AC energy-consuming devices one by one to restore the DC current of the sending-end system of the new energy islanded grid, thus completing the restart of the DC fault of the sending-end system of the new energy islanded grid.

[0066] In one embodiment of this application, obtaining the DC fault signal and the configuration number of AC energy-consuming devices in the sending-end system of the new energy islanded power grid includes: obtaining the configuration number of the corresponding AC energy-consuming devices by using the configuration number calculation formula based on the rated capacity of the sending-end flexible DC converter station and the capacity of each group of AC energy-consuming devices according to the power parameters.

[0067] The formula for calculating the number of configuration groups is:

[0068]

[0069] In the formula, N is the number of configuration groups, and P SE For the rated capacity of the sending-end flexible DC converter station, P HR The capacity of the AC power consumption device in each group.

[0070] It should be noted that the number of AC energy dissipation devices 40 configured in the new energy islanded grid sending-end system is calculated by rounding up the capacity of the sending-end flexible DC converter station and then adding two more sets of AC energy dissipation devices 40. One set of AC energy dissipation devices 40 is used for over-connection of one set of AC energy dissipation devices 40 under the most severe DC fault conditions, and the other set of AC energy dissipation devices 40 is used for maintenance backup. This is the number of sets of AC energy dissipation devices 40 configured for the new energy islanded grid sending-end system in the over-connection strategy.

[0071] Example 2:

[0072] Figure 4 This is a framework diagram of the DC fault self-clearing device for the sending-end system of a new energy islanded power grid, according to an embodiment of this application.

[0073] like Figure 4 As shown, this application embodiment also provides a DC fault self-clearing device for a new energy islanded power grid sending-end system, which is applied to the new energy islanded power grid sending-end system. The new energy islanded power grid sending-end system includes an AC bus and a new energy islanded power grid, a sending-end flexible DC converter station and an AC energy consumption device connected to the AC bus. The DC fault self-clearing device for the new energy islanded power grid sending-end system includes a strategy configuration module 100, a data acquisition module 200 and a fault clearing control module 300.

[0074] The strategy configuration module 100 is used to configure an AC / DC decoupling control strategy with AC voltage droop optimization control for the sending-end flexible DC converter station of the new energy island grid sending-end system.

[0075] The data acquisition module 200 is used to acquire DC fault signals and the configuration number and power parameters of AC energy-consuming devices in the sending-end system of the new energy island grid. The power parameters include the rated capacity of the sending-end flexible DC converter station, the power output of the new energy island grid before the fault, and the capacity of each AC energy-consuming device.

[0076] The fault clearing control module 300 is used to control the current of the DC current controller of the AC-DC decoupling control strategy to switch to 0 according to the DC fault signal, and at the same time, control the AC energy consumption device to adopt the over-transfer strategy to absorb the surplus power of the islanded grid according to the DC fault signal, so as to eliminate the fault of the sending end system of the new energy islanded grid.

[0077] Among them, the AC / DC decoupling control strategy is to use dual closed-loop constant AC voltage-frequency control on the AC side of the sending-end flexible DC converter station, and DC voltage control on the DC side of the sending-end flexible DC converter station.

[0078] In this embodiment, the DC fault self-clearing device of the new energy islanded grid sending-end system includes a restart module. The restart module is used to restore the DC voltage of the new energy islanded grid sending-end system by a DC voltage controller using an AC / DC decoupling control strategy after the fault of the new energy islanded grid sending-end system is cleared; and to restore the DC current of the new energy islanded grid sending-end system by disconnecting the AC energy-consuming devices that absorb the surplus power of the islanded grid one by one through the sending-end flexible DC converter station, so as to enable the new energy islanded grid sending-end system to achieve fault restart.

[0079] In this embodiment, the fault clearing control module 300 is also used to control the AC energy dissipation device to absorb the surplus power of the islanded power grid while controlling the operation of the AC voltage droop optimization controller in the AC-DC decoupling control strategy, so as to improve the AC side voltage of the sending-end flexible DC converter station until the full-bridge submodule capacitor voltage in the sending-end flexible DC converter station reaches the preset value, and then stop the operation of the AC voltage droop optimization controller.

[0080] In this embodiment of the application, the data acquisition module 200 is further configured to obtain the configuration number of the corresponding AC energy consumption device by using the configuration group calculation formula based on the rated capacity of the sending-end flexible DC converter station and the capacity of each group of AC energy consumption devices according to the power parameters.

[0081] The formula for calculating the number of configuration groups is:

[0082]

[0083] In the formula, N is the number of configuration groups, and P SE For the rated capacity of the sending-end flexible DC converter station, P HR The capacity of the AC power consumption device in each group.

[0084] It should be noted that the modules in the device of Embodiment 2 correspond to the steps in the method of Embodiment 1. The content of the DC fault self-clearing method of the new energy islanded power grid sending-end system has been described in detail in Embodiment 1. Therefore, the content of the modules in the device will not be described in detail in this Embodiment 2.

[0085] Example 3:

[0086] This application provides a storage device storing multiple lines of program code, which are adapted to be loaded and run by a processor to execute the above-described DC fault self-clearing method for a new energy islanded grid sending-end system.

[0087] Example 4:

[0088] This application provides a terminal device, including a processor and a memory;

[0089] Memory is used to store program code and transfer the program code to the processor;

[0090] The processor is used to execute the aforementioned DC fault self-clearing method for the sending-end system of the new energy islanded power grid according to the instructions in the program code.

[0091] It should be noted that the processor is used to execute the steps in the above-described embodiment of a DC fault self-clearing method for a new energy islanded power grid sending-end system according to the instructions in the program code. Alternatively, when the processor executes the computer program, it implements the functions of each module / unit in the above-described system / device embodiments.

[0092] For example, a computer program can be divided into one or more modules / units, one or more of which are stored in memory and executed by a processor to complete this application. One or more modules / units can be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in a terminal device.

[0093] Terminal devices can be computing devices such as desktop computers, laptops, handheld computers, and cloud servers. Terminal devices may include, but are not limited to, processors and memory. Those skilled in the art will understand that this does not constitute a limitation on the terminal device, which may include more or fewer components than illustrated, or combinations of certain components, or different components. For example, a terminal device may also include input / output devices, network access devices, buses, etc.

[0094] The processor referred to can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor.

[0095] Memory can be an internal storage unit of a terminal device, such as a hard drive or RAM. Memory can also be an external storage device, such as a plug-in hard drive, SmartMedia Card (SMC), Secure Digital (SD) card, or Flash Card. Furthermore, memory can include both internal and external storage units. Memory is used to store computer programs and other programs and data required by the terminal device. Memory can also be used to temporarily store data that has been output or will be output.

[0096] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0097] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between apparatuses or units through some interfaces, and may be electrical, mechanical, or other forms.

[0098] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0099] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0100] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0101] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for self-clearing DC faults in a renewable energy islanded grid sending-end system, applied to the renewable energy islanded grid sending-end system, wherein the renewable energy islanded grid sending-end system includes an AC bus and a renewable energy islanded grid, a sending-end flexible DC converter station, and an AC energy dissipation device connected to the AC bus, characterized in that, The self-clearing method for DC faults in the sending-end system of this new energy islanded power grid includes the following steps: Configure the sending-end flexible DC converter station of the new energy island power grid sending-end system with AC-DC decoupling control strategy with AC voltage droop optimization control; Acquire DC fault signals and the configuration number and power parameters of AC energy-consuming devices in the sending-end system of the new energy island grid. The power parameters include the rated capacity of the sending-end flexible DC converter station, the power output of the new energy island grid before the fault, and the capacity of each AC energy-consuming device. According to the DC fault signal, the current of the DC current controller of the AC-DC decoupling control strategy is switched to 0. At the same time, according to the DC fault signal, the AC energy consumption device is controlled to adopt the over-feed strategy to absorb the surplus power of the islanded grid, so as to eliminate the fault of the sending end system of the new energy islanded grid. Before controlling the AC energy-consuming device to absorb the surplus power of the isolated power grid using the over-feeding strategy according to the DC fault signal, the process includes: determining the number of AC energy-consuming devices to be put into operation to absorb the surplus power of the isolated power grid according to the power parameters using the formula for calculating the number of energy-consuming groups to be put into operation; The formula for calculating the number of energy-consuming groups is: In the formula, n is the number of AC energy-consuming devices, and P XS P represents the power output of the isolated renewable energy grid before the fault. HR The capacity of the AC power consumption device in each group; Controlling the AC energy dissipation device to absorb surplus power from the islanded power grid according to the DC fault signal includes: controlling the AC energy dissipation device to absorb surplus power from the islanded power grid while controlling the operation of the AC voltage droop optimization controller in the AC-DC decoupling control strategy to increase the AC side voltage of the sending-end flexible DC converter station until the full-bridge submodule capacitor voltage in the sending-end flexible DC converter station reaches a preset value, and then stopping the operation of the AC voltage droop optimization controller. The acquisition of DC fault signals and the configuration number of AC energy-consuming devices in the sending-end system of the new energy island power grid includes: obtaining the configuration number of the corresponding AC energy-consuming devices by using the configuration number calculation formula based on the rated capacity of the sending-end flexible DC converter station and the capacity of each group of AC energy-consuming devices according to the power parameters; The formula for calculating the number of configuration groups is: In the formula, N is the number of configuration groups, and P SE This refers to the rated capacity of the sending-end flexible DC converter station.

2. The method for self-clearing DC faults in a new energy islanded power grid sending-end system according to claim 1, characterized in that, include: If the fault in the sending-end system of the new energy islanded power grid is cleared, the DC voltage controller using the AC / DC decoupling control strategy restores the DC voltage of the sending-end system of the new energy islanded power grid; by disconnecting the AC energy-consuming devices that absorb the surplus power of the islanded power grid one by one through the sending-end flexible DC converter station, the DC current of the sending-end system of the new energy islanded power grid is restored, so that the sending-end system of the new energy islanded power grid can achieve fault restart.

3. A DC fault self-clearing device for a renewable energy islanded power grid sending-end system, applied to the renewable energy islanded power grid sending-end system, the renewable energy islanded power grid sending-end system including an AC bus and a renewable energy islanded power grid, a sending-end flexible DC converter station, and an AC energy dissipation device connected to the AC bus, characterized in that, The DC fault self-clearing device of the new energy islanded power grid sending-end system includes a strategy configuration module, a data acquisition module, and a fault clearing control module; The strategy configuration module is used to configure an AC / DC decoupling control strategy with AC voltage droop optimization control for the sending-end flexible DC converter station of the new energy island grid sending-end system. The data acquisition module is used to acquire DC fault signals and the configuration number and power parameters of AC energy-consuming devices in the sending-end system of the new energy island grid. The power parameters include the rated capacity of the sending-end flexible DC converter station, the power output of the new energy island grid before the fault, and the capacity of each AC energy-consuming device. The fault clearing control module is used to control the current of the DC current controller of the AC-DC decoupling control strategy to switch to 0 according to the DC fault signal, and at the same time control the AC energy consumption device to adopt the over-feed strategy to absorb the surplus power of the islanded grid according to the DC fault signal, so as to eliminate the fault of the sending end system of the new energy islanded grid. Before controlling the AC energy-consuming device to absorb the surplus power of the isolated power grid using the over-feeding strategy according to the DC fault signal, the process includes: determining the number of AC energy-consuming devices to be put into operation to absorb the surplus power of the isolated power grid according to the power parameters using the formula for calculating the number of energy-consuming groups to be put into operation; The formula for calculating the number of energy-consuming groups is: In the formula, n is the number of AC energy-consuming devices, and P XS P represents the power output of the isolated renewable energy grid before the fault. HR The capacity of the AC power consumption device in each group; The fault clearing control module is also used to control the AC energy consumption device to absorb the surplus power of the islanded power grid, while controlling the operation of the AC voltage droop optimization controller in the AC-DC decoupling control strategy, so as to improve the AC side voltage of the sending-end flexible DC converter station until the full-bridge submodule capacitor voltage in the sending-end flexible DC converter station reaches the preset value, and then stop the operation of the AC voltage droop optimization controller. The data acquisition module is also used to obtain the configuration group number of the corresponding AC energy consumption device by using the configuration group number calculation formula based on the rated capacity of the sending-end flexible DC converter station and the capacity of each group of AC energy consumption devices according to the power parameters. The formula for calculating the number of configuration groups is: In the formula, N is the number of configuration groups, and P SE This refers to the rated capacity of the sending-end flexible DC converter station.

4. The DC fault self-clearing device for the sending-end system of a new energy islanded power grid according to claim 3, characterized in that, The system includes a restart module, which is used to restore the DC voltage of the sending-end system of the new energy islanded grid by employing the AC / DC decoupling control strategy after the fault of the sending-end system of the new energy islanded grid is cleared; and to restore the DC current of the sending-end system of the new energy islanded grid by disconnecting the AC energy-consuming devices that absorb the surplus power of the islanded grid one by one through the sending-end flexible DC converter station, so as to enable the sending-end system of the new energy islanded grid to restart after the fault.

5. A terminal device, characterized in that, Including the processor and memory; The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the DC fault self-clearing method for the sending-end system of a new energy islanded power grid as described in claim 1 or 2, according to the instructions in the program code.

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