Low-frequency wind power plant fault ride-through control method, system, equipment and medium
By monitoring the DC bus voltage of the onshore low-frequency converter station in real time and entering the overvoltage fault protection mode, reducing the AC bus voltage and performing the fan converter unloading protection action, the protection problem of low-frequency wind farms in the event of overvoltage fault is solved, and a fast and efficient control and protection effect is achieved.
Patent Information
- Application Number
- CN202411904151.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-23
- Publication Date
- 2025-02-28
AI Technical Summary
Low-frequency wind farms are difficult to effectively protect when overvoltage failures, and there is a risk of batch disconnection.
By monitoring the DC bus voltage of the land low-frequency converter station in real time, when the voltage rises abnormally, it enters the overvoltage fault protection mode, reduces the expected value of the AC bus voltage, calculates and executes the unload protection action of the fan converter unloading circuit, and controls the wind farm to enter a standby operation state.
It realizes fast and efficient wind farm overvoltage control protection, reduces system costs and losses, and reduces the risk of disconnection.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of wind power grid connection, and in particular to a low-frequency wind farm fault ride-through control method, system, equipment and medium. Background Art
[0002] As the global demand for clean energy continues to grow, wind power generation has developed rapidly as an important renewable energy utilization method. However, wind power has the characteristics of intermittent, fluctuating and random, and its output instability has brought many challenges to the stable operation of the power system and the quality of power.
[0003] In terms of wind power grid connection, the traditional industrial frequency transmission method faces some technical bottlenecks in the transmission of large-capacity wind power over long distances. For example, when offshore wind power is transmitted to the land load center over long distances, the transmission capacity will be limited at the industrial frequency due to the influence of the cable capacitance charging current, requiring larger reactive power compensation equipment, increasing system costs and operational complexity. Against this background, wind power low-frequency transmission system technology came into being. This technology can effectively reduce the impact of cable capacitance, increase transmission capacity, and reduce reactive power compensation requirements by converting the output frequency of wind power to a lower frequency (such as 50 / 3Hz, 16.7Hz, etc.) for transmission, thereby reducing system costs and losses. The solution of low-frequency collection of offshore wind farms through DRU (uncontrolled rectifier) and flexible DC transmission can effectively reduce costs, volume and weight.
[0004] However, since the DRU is an uncontrolled device, it is difficult to control the voltage of the low-frequency system. When the AC system fails, it is difficult to protect the low-frequency system from overvoltage. There is a risk of mass disconnection of low-frequency wind farms due to overvoltage protection.
[0005] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to those skilled in the art. Summary of the invention
[0006] The present invention provides a low-frequency wind farm fault ride-through control method, system, device and medium, thereby effectively solving the problems in the background technology.
[0007] In order to achieve the above object, the technical solution adopted by the present invention is: a low-frequency wind farm fault ride-through control method, comprising the following steps: Monitor the voltage of the DC bus of the onshore low-frequency converter station in real time. When the DC bus voltage rises abnormally, it enters the overvoltage fault protection mode. After entering the voltage fault protection mode, the expected value of the AC bus voltage is reduced to below the start-up threshold voltage of the uncontrolled rectifier DRU, and the amount of energy required to be consumed by the wind turbine converter unloading circuit connected to the low-frequency wind farm is calculated; According to the energy quantity, the converter unloading circuits of all wind turbines are controlled to perform unloading protection actions, Monitor whether the current value of the AC bus voltage of the offshore wind farm is lower than the DRU start-up threshold voltage. If so, the offshore low-frequency wind farm enters the standby operation state; Determine whether the conditions for transmitting power from the low-frequency wind farm are met. If so, exit the overvoltage fault protection mode.
[0008] Furthermore, the abnormal increase in DC bus voltage includes: the DC bus voltage exceeds an upper threshold, or the voltage increase rate exceeds a protection value.
[0009] Furthermore, the calculation of the amount of energy required to be consumed by the unloading circuit of the wind turbine converter connected to the low-frequency wind farm comprises the following steps: The total energy to be consumed is calculated based on the difference between the current value and the expected value of the AC bus voltage; The amount of energy that needs to be consumed by the unloading circuit of each wind turbine converter is calculated according to the total energy and the operating status of the wind turbines connected to the low-frequency wind farm.
[0010] Furthermore, the determining whether the conditions for power transmission from the low-frequency wind farm are met includes: determining whether the DC bus voltage of the low-frequency converter station is normal.
[0011] Furthermore, after entering the overvoltage fault protection mode, the method further includes: Start timing and determine whether the time exceeds the set threshold; If the offshore low-frequency wind farm exceeds the set threshold and has not entered the standby operation state, a shutdown command is issued to control the low-frequency wind turbine to execute the shutdown action.
[0012] The present invention also includes a low-frequency wind farm fault ride-through control system, using the above method, the device includes: The acquisition unit is used to monitor the voltage of the DC bus of the onshore low-frequency converter station in real time. When the DC bus voltage rises abnormally, it enters the overvoltage fault protection mode; The energy calculation unit is used to reduce the expected value of the AC bus voltage to below the start-up threshold voltage of the uncontrolled rectifier DRU after entering the voltage fault protection mode, and calculate the amount of energy that needs to be consumed by the wind turbine converter unloading circuit connected to the low-frequency wind farm; A load unloading control unit is used to control the converter unloading circuits of all wind turbines to perform load unloading protection actions according to the energy quantity. A monitoring unit is used to monitor whether the current value of the AC bus voltage of the offshore wind farm is lower than the DRU start threshold voltage. If so, the offshore low-frequency wind farm enters a standby operation state; The judgment unit is used to judge whether the conditions for transmitting power from the low-frequency wind farm are met, and if so, exit the overvoltage fault protection mode.
[0013] Furthermore, the load unloading control unit includes a plurality of high-speed communication lines, and the plurality of high-speed communication lines are respectively connected to converters of low-frequency wind turbines in the offshore wind farm to transmit information.
[0014] Furthermore, the high-speed communication line is based on communication optical fiber, and the communication protocol includes a real-time industrial Ethernet communication protocol using a real-time communication mode such as EtherCAT or PROFINET.
[0015] Furthermore, the acquisition unit includes an AC bus detection sensor and a DC bus detection sensor, which respectively collect electrical parameters of the AC bus and electrical parameters of the DC bus.
[0016] The present invention also includes a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method described above is implemented.
[0017] The present invention also includes a storage medium on which a computer program is stored. When the computer program is executed by a processor, the method described above is implemented.
[0018] The beneficial effects of the present invention are: the DC bus voltage of the low-frequency converter station is monitored in real time by the control and protection system. When the bus voltage rises abnormally, the wind farm control system directly issues a command and directly controls each low-frequency wind turbine converter to perform a load-shedding action. The control and protection method of the present invention has a small number of control levels, fast communication speed, and fast execution of actions from fault discovery to execution of protection actions. Therefore, compared with traditional methods, it is a fast and efficient wind farm overvoltage control and protection method. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0020] Figure 1 is a flow chart of the method in Example 1; Figure 2 It is a structural schematic diagram of the system in Example 1; Figure 3 This is a topological diagram of the offshore low-frequency wind power plant in Example 2; Figure 4 This is a topological diagram of the low-frequency wind farm control and protection system in Example 2; Figure 5 It is a structural schematic diagram of the computer device of the present invention. DETAILED DESCRIPTION
[0021] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.
[0022] Embodiment 1: like Figure 1 As shown: A low-frequency wind farm fault ride-through control method comprises the following steps: Monitor the voltage of the DC bus of the onshore low-frequency converter station in real time. When the DC bus voltage rises abnormally, it enters the overvoltage fault protection mode. After entering the voltage fault protection mode, the expected value of the AC bus voltage is reduced to below the start-up threshold voltage of the uncontrolled rectifier DRU, and the amount of energy required to be consumed by the wind turbine converter unloading circuit connected to the low-frequency wind farm is calculated; According to the energy quantity, the inverter unloading circuit of all wind turbines is controlled to perform unloading protection action. Monitor whether the current value of the AC bus voltage of the offshore wind farm is lower than the DRU start-up threshold voltage. If so, the offshore low-frequency wind farm enters the standby operation state; Determine whether the conditions for transmitting power from the low-frequency wind farm are met. If so, exit the overvoltage fault protection mode.
[0023] The fault ride-through control method in this embodiment is an active protection method. The control and protection system monitors the DC bus voltage of the low-frequency converter station in real time. When the bus voltage rises abnormally (for example, the voltage exceeds the upper threshold or the voltage rise rate exceeds the protection value), the wind farm control system directly issues a command and directly controls each low-frequency wind turbine converter to perform a load-shedding action. The control and protection method in this embodiment has fewer control levels, faster communication speed, and faster execution of actions from fault detection to protection action execution. Therefore, compared with the traditional method, it is a fast and efficient wind farm overvoltage control and protection method. The traditional wind farm overvoltage protection system is a passive protection method. That is, when the wind farm control system or wind turbine detects an AC bus overvoltage, the wind farm or wind turbine enters a high-through fault state, and only then will the main control system of the wind turbine issue a command to the converter to execute high-through protection. It has many control levels, slow communication speed, and cannot directly control / call the load-shedding circuit in the converter, so the efficiency is relatively low.
[0024] By flexibly utilizing the DRU start-stop voltage threshold, relying on the low-frequency wind farm's entire energy control system and the actual local unloading resistors of the wind turbines, fault protection of the low-frequency wind farm system under transient conditions is achieved. In the event of an AC power grid failure, when a three-phase to ground short circuit occurs in the onshore power grid, the offshore low-frequency wind farm control system directly calls the control method of the unloading circuit configured for the converters of all wind turbines in the low-frequency wind farm (rather than just the unloading circuit of the converter of the wind turbine that is generating electricity). This allows full use of the hardware unloading circuit equipment configured on the wind turbine side of the wind farm, without the need to configure dedicated and expensive unloading circuits and other equipment at the AC bus position of the wind farm.
[0025] Different from the conventional passive response to fault crossing method, the method in this embodiment can realize that when a three-phase to ground short circuit fault occurs in the land AC power grid, the offshore low-frequency wind farm can quickly and actively enter the fault protection state in the first time. The characteristic of this method is to actively mobilize and control the fault protection and fault handling of the offshore wind turbine generator set as soon as the fault occurs, which obviously helps to reduce and alleviate the overvoltage caused by the short circuit fault, and significantly improve the recovery speed of the short circuit fault. The conventional method for dealing with the three-phase to ground short circuit fault of the power grid is that the offshore wind farm end outputs energy to the DRU end. If the DRU end stops working due to a fault, an overvoltage occurs in the offshore AC bus. When the wind turbine detects the overvoltage, it enters a fault state or enters a high-throughput mode. Obviously, this is a passive and hysteretic way to deal with faults.
[0026] In this embodiment, the abnormal increase of the DC bus voltage includes: the DC bus voltage exceeds an upper threshold, or the voltage increase rate exceeds a protection value.
[0027] As a preferred embodiment of the above, calculating the amount of energy required to be consumed by the unloading circuit of the wind turbine converter connected to the low-frequency wind farm includes the following steps: The total energy to be consumed is calculated based on the difference between the current value and the expected value of the AC bus voltage; According to the total energy and the operating status of the wind turbines connected to the low-frequency wind farm, the amount of energy that needs to be consumed by the unloading circuit of the converter of each wind turbine is calculated.
[0028] After entering the voltage fault protection mode, the low-frequency wind farm control and protection system sets the AC bus voltage expected value U Grid-desired Reduced to below the DRU unit start threshold voltage, and then according to the current value of the AC bus voltage U Grid The expected value of AC bus voltage U Grid-desired The energy E that needs to be consumed is calculated by the difference exhaustThe low-frequency wind farm control and protection system calculates the energy E to be consumed according to the status of the wind turbine converter that has been connected to the low-frequency wind farm energy protection system. exhaust The analysis is performed to calculate the amount of energy that needs to be consumed by the converter unloading circuit of each wind turbine that has been connected to the low-frequency wind farm energy protection system. Since the operating state of each wind turbine is different, the energy that needs to be released by the converter unloading circuit of each wind turbine is also different. For example, a wind turbine running at full power cannot send power when it fails, so the energy it needs to consume is roughly full power; and a wind turbine running at 30% of the rated power, when it fails, the energy it needs to consume is roughly 30% of the rated power.
[0029] The low-frequency wind farm control and protection system issues a command to directly control the converter unloading circuits of all wind turbines connected to the low-frequency wind farm at the time of the fault through high-speed communication lines to perform unloading protection actions. The amount of energy required to be consumed by each wind turbine is executed according to the energy data required to be consumed by each wind turbine calculated in the second step. It should be noted that the number of converters that can perform unloading actions at this time is different from the number of wind turbines that are running to generate electricity in the low-frequency wind farm. Ideally, the number of converters that can perform unloading actions should be equal to the number of all wind turbine converters in the low-frequency wind farm. In general, there are always some wind turbines in a wind farm that are in a non-generating state, such as a maintenance state or a fault state. As long as the converters of these wind turbines are in a grid-connected state, their unloading circuits can all participate in the execution of this unloading protection action. In other words, the energy control and protection system of this embodiment can call the converter unloading circuits of the entire wind farm to perform protection actions when the grid side is overvoltage.
[0030] Through the unloading circuit equipped with the wind turbine converter, each wind turbine discharges the energy on the wind turbine DC bus at the time of the fault, so that the offshore low-frequency wind farm directly reduces or stops the energy output to the low-frequency converter station DRU unit. Due to the control of the low-frequency wind farm control and protection system, the current value of the AC bus voltage U Grid When the voltage is lower than the DRU unit start-up threshold voltage, the offshore low-frequency wind farm enters the standby operation state.
[0031] In this embodiment, judging whether the condition for transmitting electric energy from the low-frequency wind farm is met includes judging whether the DC bus voltage of the low-frequency converter station is normal.
[0032] As a preferred embodiment of the above, after entering the overvoltage fault protection mode, the method further includes: Start timing and determine whether the time exceeds the set threshold; If the offshore low-frequency wind farm exceeds the set threshold and has not entered the standby operation state, a shutdown command is issued to control the low-frequency wind turbine to execute the shutdown action.
[0033] If the subsequent grounding fault disappears, the DC bus voltage of the low-frequency converter station returns to normal, and when the conditions for power transmission of other low-frequency wind farms are met, the low-frequency wind farm control and protection system will increase the AC bus voltage of the low-frequency wind farm to the DRU unit start-up threshold voltage, and the low-frequency wind farm will resume outputting energy. If the subsequent grounding fault does not disappear, and the continuous fault time exceeds the high-through fault requirement, the low-frequency wind farm control and protection system will issue a shutdown command, and the low-frequency wind turbine will perform a normal shutdown action.
[0034] like Figure 2 As shown, this embodiment also includes a low-frequency wind farm fault ride-through control system, using the above method, the device includes: The acquisition unit is used to monitor the voltage of the DC bus of the onshore low-frequency converter station in real time. When the DC bus voltage rises abnormally, it enters the overvoltage fault protection mode; The energy calculation unit is used to reduce the expected value of the AC bus voltage to below the start-up threshold voltage of the uncontrolled rectifier DRU after entering the voltage fault protection mode, and calculate the amount of energy that needs to be consumed by the wind turbine converter unloading circuit connected to the low-frequency wind farm; The unloading control unit is used to control the unloading circuit of the converter of all wind turbines to perform unloading protection actions according to the energy quantity. A monitoring unit is used to monitor whether the current value of the AC bus voltage of the offshore wind farm is lower than the DRU start threshold voltage. If so, the offshore low-frequency wind farm enters a standby operation state; The judgment unit is used to judge whether the conditions for transmitting power from the low-frequency wind farm are met, and if so, exit the overvoltage fault protection mode.
[0035] The load unloading control unit includes a plurality of high-speed communication lines, which are respectively connected to converters of low-frequency wind turbines in the offshore wind farm to transmit information.
[0036] This embodiment simplifies the traditional three-level wind farm energy management system. There are only two levels of control systems from the wind farm energy management control system to the converter that actually executes the active / reactive equipment. A fast energy control system for a wind farm is implemented based on real-time industrial Ethernet communication technology. The fast energy control system implemented in this embodiment can achieve an active / reactive response speed within tens of milliseconds (typical value 40-60ms); and the low-frequency wind farm fault crossing control system can directly control / call the unloading circuit configured in the wind turbine converter. Therefore, when an overvoltage fault occurs on the grid side, the unloading circuit configured in all wind turbine converters can participate in the unloading protection action, so there is no need to configure expensive AC / DC unloading protection equipment separately.
[0037] In this embodiment, the high-speed communication line is based on a communication optical fiber, and the communication protocol includes a real-time industrial Ethernet communication protocol using a real-time communication mode such as EtherCAT or PROFINET.
[0038] As a preference of the above embodiment, the acquisition unit comprises an AC bus detection sensor and a DC bus detection sensor, which respectively acquire electrical parameters of the AC bus and electrical parameters of the DC bus.
[0039] The low-frequency wind farm control system of this embodiment is a fast wind farm control system based on real-time industrial Ethernet communication technology. It is based on real-time industrial Ethernet communication technology, and it is directly connected to the controlled object, that is, the converter of each wind turbine in the offshore wind farm through a high-speed communication line such as an optical fiber. This design enables the converter configured for each wind turbine to respond quickly to the active / reactive adjustment command sent by the low-frequency wind farm control system, and the response time can reach less than 40ms or lower.
[0040] Conventional wind farm control systems are limited by traditional design methods and traditional multi-level communication methods. For example, conventional wind farm control systems usually send active / reactive regulation commands to each wind turbine controller, which then parses the active / reactive regulation commands and sends the parsed active / reactive regulation commands to the converter for execution. Therefore, the execution response time of the conventional wind farm control system to control and regulate active / reactive energy is at the second level, and it is difficult to achieve a fast response. Therefore, traditional energy control is only for steady-state control and does not have the regulation function under transient conditions.
[0041] Usually, when the industry designs and implements it, the first step is for the wind farm control system to communicate directly with the wind turbine control system, that is, to send the active / reactive power regulation command to the wind turbine control system; the second step is for the wind turbine control system to parse the active / reactive power regulation command according to the wind turbine control strategy. If the machine cannot execute the reactive power demand / reactive power call command due to the working conditions, the information that cannot be executed will be fed back to the wind farm reactive power control system; if the machine can execute the active / reactive power regulation command according to the working conditions, the execution feedback of the active / reactive power regulation command will be fed back to the wind farm control system, and the executable active / reactive power regulation command will be sent to the converter at the same time; the third step is for the converter to execute and issue the active / reactive power action according to the active / reactive power regulation command sent by the wind turbine master control system.
[0042] The wind farm control system of this patent is characterized by: (1) direct communication connection with the converter equipped with each wind turbine without going through any intermediate level; (2) having transient control function, breaking through the disadvantage that the traditional scheme only provides steady-state control function; (3) introducing a fast communication mechanism, which has the advantage of achieving real-time communication, simple communication architecture and fast communication speed, so that the converter of the wind turbine can respond quickly to the active / reactive adjustment command.
[0043] Embodiment 2: The main technical problem to be solved by this embodiment is: how an offshore low-frequency wind farm working in the DRU mode can ride through a high voltage fault.
[0044] from Figure 3 It can be seen that when a three-phase symmetrical grounding fault occurs in the AC system of the onshore power grid (power frequency 50Hz) at the position shown in the figure, the AC bus voltage of the power grid drops, and the grid-side unit of the onshore-DC / AC converter station reduces the active power transmitted to the onshore power grid. However, at this time, the active power transmitted by the offshore wind farm to the onshore low-frequency converter station remains unchanged, which causes the DC bus voltage of the low-frequency converter station to rise rapidly. When the DC bus voltage rises and exceeds the upper limit threshold of the DC voltage, the onshore low-frequency converter station unit will be shut down. When the onshore low-frequency converter station unit is shut down, the offshore low-frequency wind farm will not be able to send out electric energy, which will cause the AC bus voltage of the offshore low-frequency wind farm to rise. When the voltage rises and exceeds the upper limit threshold of the AC voltage, it will trigger an overvoltage fault in the offshore wind farm, which will lead to batch disconnection from the grid.
[0045] This embodiment designs a low-frequency wind farm control and protection system, which will monitor the DC bus voltage of the onshore low-frequency converter station in real time. When the DC bus voltage of the low-frequency converter station increases abnormally (for example, the voltage exceeds the upper threshold or the voltage increase rate exceeds the protection value), the low-frequency wind farm control and protection system will immediately execute the overvoltage protection program. It will directly control the converters of all wind turbines connected to the low-frequency wind farm at the time of fault protection action execution and execute the converter unloading protection action. In this way, the AC bus voltage of the low-frequency wind farm will be reduced to below the DRU unit starting threshold voltage in the shortest time, and the offshore low-frequency wind farm will be controlled to enter the standby mode within the high-through fault time. If the subsequent grounding fault disappears, the DC bus voltage of the low-frequency converter station returns to normal, and the conditions for power transmission of other low-frequency wind farms are met, the low-frequency wind farm control and protection system will increase the AC bus voltage of the low-frequency wind farm to the DRU unit start-up threshold voltage, and the low-frequency wind farm will resume outputting energy. If the subsequent grounding fault does not disappear, and the continuous fault time exceeds the high-through fault requirement (the default value can be set according to GB / T 19963.2-2024 or executed according to the time required by the customer), the low-frequency wind farm control and protection system will issue a shutdown command, and the low-frequency wind turbine will perform a normal shutdown action.
[0046] Since the low-frequency wind farm control and protection system designed in this embodiment is directly connected to each low-frequency wind turbine in the low-frequency wind farm through fast communication lines such as optical fiber, each low-frequency wind turbine in the offshore low-frequency wind farm can stop or reduce energy output within tens of ms or faster.
[0047] Through this protection and control method, the power transmitted from the offshore low-frequency wind farm to the DRU unit of the low-frequency converter station will be greatly reduced or even zero, and can be flexibly controlled, which will effectively assist the low-frequency converter station to survive a three-phase symmetrical grounding fault.
[0048] like Figure 4 As shown, this embodiment designs a low-frequency wind farm control and protection system. The system detects two signals in real time, one for real-time monitoring of the voltage of the DC bus in the onshore low-frequency converter station and the other for real-time monitoring of the voltage of the AC bus in the offshore low-frequency wind farm.
[0049] At the same time, the control and protection system is directly connected to the converter of the low-frequency wind turbine in the offshore wind farm through a high-speed communication line, generally in series, but also in parallel, without passing through the traditional wind turbine control system level. In addition, the communication hardware itself is based on communication optical fiber, and the communication protocol uses real-time industrial Ethernet communication protocols such as EtherCAT or PROFINET that use real-time communication mode (other high-speed communication protocols can also be used). This ensures that the wind turbine converter can send active / reactive power at high speed and in a timely manner to respond to the control and protection commands issued by the control system.
[0050] This embodiment designs a high voltage fault ride-through control method for an offshore low-frequency wind farm suitable for a DRU mode.
[0051] In the first step, when the offshore low-frequency wind farm is normally exporting electric energy, the low-frequency wind farm control and protection system described in this embodiment monitors the voltage of the DC bus of the onshore low-frequency converter station in real time. When the DC bus voltage of the low-frequency converter station increases abnormally (for example, the voltage exceeds the upper threshold or the voltage increase rate exceeds the protection value), the low-frequency wind farm control and protection system immediately enters the overvoltage fault protection mode.
[0052] In the second step, after entering the voltage fault protection mode, the low-frequency wind farm control and protection system sets the AC bus voltage expected value U Grid-desired Reduced to below the DRU unit start threshold voltage, and then according to the current value of the AC bus voltage U Grid The expected value of AC bus voltage U Grid-desired The energy E that needs to be consumed is calculated by the difference exhaust The low-frequency wind farm control and protection system calculates the energy E to be consumed according to the status of the wind turbine converter that has been connected to the low-frequency wind farm energy protection system.exhaust The analysis is performed to calculate the amount of energy that needs to be consumed by the converter unloading circuit of each wind turbine that has been connected to the low-frequency wind farm energy protection system. Since the operating state of each wind turbine is different, the energy that needs to be released by the converter unloading circuit of each wind turbine is also different. For example, a wind turbine running at full power cannot send power when it fails, so the energy it needs to consume is roughly full power; and a wind turbine running at 30% of the rated power, when it fails, the energy it needs to consume is roughly 30% of the rated power.
[0053] In the third step, the low-frequency wind farm control and protection system issues a command to directly control the converter unloading circuits of all wind turbines connected to the low-frequency wind farm at the time of the fault through high-speed communication lines to perform unloading protection actions. The amount of energy required to be consumed by each wind turbine is executed according to the energy data required to be consumed by each wind turbine calculated in the second step. It should be noted that the number of converters that can perform unloading actions at this time is different from the number of wind turbines that are running and generating electricity in the low-frequency wind farm. Ideally, the number of converters that can perform unloading actions should be equal to the number of all wind turbine converters in the low-frequency wind farm. In general, there are always some wind turbines in a wind farm that are in a non-power generation state, such as a maintenance state or a fault state. As long as the converters of these wind turbines are in a grid-connected state, their unloading circuits can all participate in the execution of this unloading protection action. In other words, the energy control and protection system described in this embodiment can call the converter unloading circuits of the entire wind farm to perform protection actions when the grid side is overvoltage.
[0054] In the fourth step, after the action in the third step, that is, through the unloading circuit equipped with the wind turbine converter, each wind turbine discharges the energy on the wind turbine DC bus at the time of the fault, so that the offshore low-frequency wind farm directly reduces or stops the energy output to the low-frequency converter station DRU unit. Due to the control of the low-frequency wind farm control and protection system, the current value of the AC bus voltage of the offshore wind farm U Grid When the voltage is lower than the DRU unit start-up threshold voltage, the offshore low-frequency wind farm enters the standby operation state.
[0055] Step 5: If the subsequent grounding fault disappears, the DC bus voltage of the low-frequency converter station returns to normal, and when the conditions for other low-frequency wind farms to transmit power are met, the low-frequency wind farm control and protection system will increase the AC bus voltage of the low-frequency wind farm to the DRU unit start-up threshold voltage, and the low-frequency wind farm will resume outputting energy. If the subsequent grounding fault does not disappear, and the continuous fault time exceeds the high-through fault requirement, the low-frequency wind farm control and protection system will issue a shutdown command, and the low-frequency wind turbine will perform a normal shutdown action.
[0056] See also Figure 5A computer device 400 provided in an embodiment of the present application includes: a processor 410 and a memory 420, wherein the memory 420 stores a computer program executable by the processor 410, and when the computer program is executed by the processor 410, the above method is executed.
[0057] The embodiment of the present application further provides a storage medium 430 on which a computer program is stored. When the computer program is run by the processor 410, the above method is executed.
[0058] Among them, the storage medium 430 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, disk or optical disk.
[0059] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. "Multiple" means two or more, unless otherwise clearly and specifically defined.
[0060] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0061] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.
[0062] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.
[0063] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples (non-exhaustive list) of computer-readable media include the following: an electrical connection with one or more wires (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.
[0064] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.
[0065] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.
[0066] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.
Claims
1. A low-frequency wind farm fault ride-through control method, characterized in that: The steps include: Real-time monitoring of the DC bus voltage of the onshore low-frequency converter station. When the DC bus voltage rises abnormally, the overvoltage fault protection mode is entered; After entering the voltage fault protection mode, the expected value of the AC bus voltage is reduced to below the start-up threshold voltage of the uncontrolled rectifier DRU, and the amount of energy required to be consumed by the wind turbine converter unloading circuit connected to the low-frequency wind farm is calculated; According to the energy quantity, controlling the converter unloading circuits of all wind turbines to perform unloading protection action; Monitor whether the current value of the AC bus voltage of the offshore wind farm is lower than the DRU start-up threshold voltage. If so, the offshore low-frequency wind farm enters the standby operation state; Determine whether the conditions for transmitting power from the low-frequency wind farm are met. If so, exit the overvoltage fault protection mode.
2. The low-frequency wind farm fault ride-through control method according to claim 1, characterized in that: The abnormal increase in DC bus voltage includes: the DC bus voltage exceeds the upper limit threshold, or the voltage increase rate exceeds the protection value.
3. The low-frequency wind farm fault ride-through control method according to claim 1, characterized in that: The step of calculating the amount of energy that needs to be consumed by the unloading circuit of the wind turbine converter connected to the low-frequency wind farm comprises the following steps: The total energy to be consumed is calculated based on the difference between the current value and the expected value of the AC bus voltage; The amount of energy that needs to be consumed by the unloading circuit of each wind turbine converter is calculated according to the total energy and the operating status of the wind turbines connected to the low-frequency wind farm.
4. The low-frequency wind farm fault ride-through control method according to claim 1, characterized in that: The determining whether the conditions for power transmission from the low-frequency wind farm are met includes: determining whether the DC bus voltage of the low-frequency converter station is normal.
5. The low-frequency wind farm fault ride-through control method according to claim 1, characterized in that: After entering the overvoltage fault protection mode, the method further includes: Start timing and determine whether the time exceeds the set threshold; If the offshore low-frequency wind farm exceeds the set threshold and has not entered the standby operation state, a shutdown command is issued to control the low-frequency wind turbine to execute the shutdown action.
6. A low-frequency wind farm fault ride-through control system, characterized in that: Using the method according to any one of claims 1 to 5, the device comprises: The acquisition unit is used to monitor the voltage of the DC bus of the onshore low-frequency converter station in real time. When the DC bus voltage rises abnormally, it enters the overvoltage fault protection mode; The energy calculation unit is used to reduce the expected value of the AC bus voltage to below the start-up threshold voltage of the uncontrolled rectifier DRU after entering the voltage fault protection mode, and calculate the amount of energy that needs to be consumed by the wind turbine converter unloading circuit connected to the low-frequency wind farm; A load unloading control unit is used to control the converter unloading circuits of all wind turbines to perform load unloading protection actions according to the energy quantity. A monitoring unit is used to monitor whether the current value of the AC bus voltage of the offshore wind farm is lower than the DRU start threshold voltage. If so, the offshore low-frequency wind farm enters a standby operation state; The judgment unit is used to judge whether the conditions for transmitting power from the low-frequency wind farm are met, and if so, exit the overvoltage fault protection mode.
7. The low-frequency wind farm fault ride-through control system according to claim 6, characterized in that: The load unloading control unit includes a plurality of high-speed communication lines, and the plurality of high-speed communication lines are respectively connected to converters of low-frequency wind turbines in an offshore wind farm to transmit information.
8. The low-frequency wind farm fault ride-through control system according to claim 7, characterized in that: The high-speed communication line is based on communication optical fiber, and the communication protocol includes a real-time industrial Ethernet communication protocol using a real-time communication mode such as EtherCAT or PROFINET.
9. The low-frequency wind farm fault ride-through control system according to claim 6, characterized in that: The acquisition unit comprises an AC bus detection sensor and a DC bus detection sensor, which respectively collect electrical parameters of the AC bus and electrical parameters of the DC bus.
10. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 5 is implemented.
11. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.