Low-frequency wind turbine generator set and wind power plant island crossing method, system, equipment and medium

Abstract

The invention relates to the technical field of wind power integration, in particular to a low-frequency wind turbine generator and wind power plant island crossing method, system and device and a medium, and the method comprises the steps: carrying out the wind power plant networking through employing a network construction type low-frequency wind turbine generator and a network following type low-frequency wind turbine generator based on a low-frequency transmission technology, and integrating an energy storage unit in the network construction type low-frequency wind turbine generator; collecting a closing state signal of a main circuit breaker at the high and low voltage sides of the main transformer and a locking signal of an M3C converter power electronic device in real time; in the island working mode, calculating a total active power balance state in real time to obtain a power difference value, and generating a power instruction according to the power difference value; the method comprises the following steps: scanning the operation state of a network-forming type low-frequency wind turbine generator in operation in real time, issuing a droop control mode instruction and a power instruction according to the operation state, maintaining the system voltage and the system frequency in a wind power plant according to the instructions, and absorbing active power by an energy storage unit; and tracking whether the real-time total active power is balanced or not, if not, updating the power instruction, and circulating the instruction issuing process.

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 turbine set and a wind farm island crossing method, system, equipment and medium. Background Art

[0002] In order to solve the problems of energy shortage and environmental pollution, clean, renewable and green energy such as wind energy has begun to receive high attention and has been developed rapidly. Among them, wind power generation, as the most mature application of wind energy, has been widely used and has begun to develop rapidly.

[0003] The vast majority of wind power development and utilization scenarios are onshore wind farms. With the continuous advancement of wind power technology, offshore wind power has also developed rapidly in recent years. In existing technologies, there are two main technical routes for offshore wind power transmission: The first is a transmission solution based on industrial frequency high-voltage alternating current transmission (HVAC). This solution has low overall cost, mature technology and rich engineering experience. Most of the offshore wind farm projects that have been put into operation currently adopt this solution. However, affected by the charging current of the submarine cable system, when the offshore wind farm is farther from the shore or the transmission distance of wind power exceeds a certain distance (about 80km), the traditional transmission solution based on industrial frequency high-voltage alternating current transmission (HVAC) is no longer the most economical solution.

[0004] The second is a transmission scheme based on high-voltage direct current transmission (VSC-HVAC). Compared with the HVAC scheme, its cost indicators are better in deep sea scenarios. However, the VSC-HVDC scheme requires the configuration of an offshore converter station, which has high construction and operation and maintenance costs. The DC circuit breaker technology is not yet fully mature, and the "space charge effect" of the DC cable will have an adverse effect on the cable insulation.

[0005] As the normalization of offshore wind power is approaching, based on the engineering reality that "the price reduction space of wind turbines has reached the capacity limit", cost reduction has begun to shift from single-machine cost reduction to system-level cost reduction. In view of this, a third technical route has emerged: a system networking solution based on the principle of low-frequency high-voltage AC transmission (LFAC). Different from the conventional HVAC solution or the conventional VSC-HVDC solution, the high-voltage side of the booster substation of the LFAC solution is 66kV, which is much higher than the previous 35kV; at the same time, the frequency is only about one-third of the power frequency, which has improved the power transmission capacity of the collection system and reduced losses. However, in the LFAC system, if the AC / AC converter (M3C) suddenly locks due to its own protection and other reasons, it will inevitably cause the low-frequency system to be disconnected from the grid; however, under the off-grid condition, the wind farm side will experience system instability caused by power imbalance and overvoltage faults at the wind turbine end, which will cause shutdown and reduce the life of the wind turbine, or even cause the entire power station to be disconnected from the grid due to overvoltage or wind turbine equipment to be damaged in batches due to transient overvoltage.

[0006] Therefore, how to reduce the transmission cost of offshore wind farms when the offshore distance is 80km~200km, avoid system instability in wind farms, and enable offshore wind farms to quickly cross isolated islands has become an urgent problem to be solved.

[0007] 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

[0008] The present invention provides a low-frequency wind turbine set and a wind farm island crossing method, system, equipment and medium, thereby effectively solving the problems in the background technology.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is: a low-frequency wind turbine and a wind farm island crossing method, comprising the following steps: Based on low-frequency transmission technology, wind farms are networked using grid-building low-frequency wind turbines and grid-following low-frequency wind turbines, and power storage units are integrated into the grid-building low-frequency wind turbines. Real-time acquisition of the closing state signal of the main circuit breaker on the high and low voltage sides of the main transformer and the blocking signal of the power electronic device of the modular multi-level matrix M3C converter. If any signal is disconnected, the wind farm enters the island working mode; In the island working mode, the total active power balance state of the off-grid system is calculated in real time to obtain the power difference between the active power and the load, and a power command is generated accordingly; Scanning the operating status of the grid-forming low-frequency wind turbines in operation in real time, and issuing a droop control mode instruction and the power instruction to the grid-forming low-frequency wind turbines accordingly, so that the grid-forming low-frequency wind turbines maintain the system voltage and system frequency in the wind farm according to the droop control mode instruction, and control the energy storage unit to absorb active power according to the power instruction; Track whether the real-time total active power is balanced. If not, update the power command and circulate the command process; if yes, exit the wind farm island working mode.

[0010] Furthermore, the real-time calculation of the total active power balance state of the off-grid system includes: Collect various parameters or power command values ​​required for power balance within the wind farm in real time, and calculate the total active power based on the collected parameters and power command values; By making the total active power zero, the total active power balance state is determined.

[0011] Furthermore, the real-time collection of various parameters or power command values ​​required for internal power balance of the wind farm includes: The power command value Pref_gfm of the grid-building type low-frequency wind turbine that can be operated, the power command value Pref_gfl of the grid-following type low-frequency wind turbine that can be operated, the instantaneous power dissipation value Pchop of the chopper of the grid-following / grid-building type low-frequency wind turbine that can be operated, and the total limit value P_bess of the rechargeable standby capacity of the energy storage unit of the grid-building type low-frequency wind turbine that can be operated; The calculation of total active power P is: P=Pref_gfl+Pref_gfm-Pchop-P_bess.

[0012] Further, the issuing of the droop control mode instruction and the power instruction to the grid-type low-frequency wind turbine generator set so that the grid-type low-frequency wind turbine generator set maintains the system voltage and system frequency in the wind farm according to the droop control mode instruction and controls the energy storage unit to absorb active power according to the power instruction, including: The grid-type low-frequency wind turbine generator set reduces the internal potential amplitude and phase angle, and realizes power back absorption to the DC bus; The energy storage unit absorbing active power includes: the energy storage unit converts the charging mode to absorb active power, aiming to balance the total active power of the off-grid system.

[0013] Furthermore, the updating of the power instruction and the process of issuing the instruction cyclically also include: Starting timing while updating the power instruction; If the timing exceeds the set time, and the difference between the real-time active power and the load power exceeds the power corresponding to the highest transient overvoltage set by the wind turbine, the entire site will enter the shutdown process.

[0014] Furthermore, the updating of the power instruction and the process of issuing the instruction cyclically also include: Consider the charging capacity limit of the energy storage unit; If the total active power of the off-grid system is still not balanced after reaching the limit, the power command value of the grid-following low-frequency wind turbine will be reduced.

[0015] The present invention also includes a low-frequency wind turbine and a wind farm island crossing system, using the above method, the system includes: A wind farm networking system, which is based on low-frequency transmission technology, uses a networking type low-frequency wind turbine and a grid-following type low-frequency wind turbine to network the wind farm, and integrates a power storage unit in the networking type low-frequency wind turbine; The acquisition unit is used to collect the closing state signal of the main circuit breaker on the high and low voltage sides of the main transformer and the locking signal of the power electronic device of the modular multi-level matrix M3C converter in real time. If any signal is disconnected, the wind farm enters the island working mode; A calculation unit, used for calculating the total active power balance state of the off-grid system in real time in the island working mode, obtaining the power difference between the active power and the load, and generating a power instruction accordingly; A control unit, used for scanning the operating status of the grid-forming low-frequency wind turbine in operation in real time, and issuing a droop control mode instruction and the power instruction to the grid-forming low-frequency wind turbine accordingly, so that the grid-forming low-frequency wind turbine maintains the system voltage and system frequency in the wind farm according to the droop control mode instruction, and controls the energy storage unit to absorb active power according to the power instruction; The control unit is also used to track whether the real-time total active power is balanced. If not, the power command is updated and the command issuing process is cyclical; if yes, the wind farm island working mode is exited.

[0016] Furthermore, the power energy storage unit is a fast-charge and fast-discharge power energy storage unit.

[0017] 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.

[0018] 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.

[0019] The beneficial effects of the present invention are as follows: based on the low-frequency transmission technology, the power transmission capacity of the collection system can be improved, the loss can be reduced, and thus the transmission cost of offshore wind farms at long distances can be reduced. Moreover, under the low-frequency transmission technology, the voltage suppression effect and island crossing effect of the grid-forming low-frequency wind turbine set in the M3C locked state or the wind farm isolated grid operation state are introduced for the first time, and a power-type energy storage unit is integrated on the grid-forming wind turbine set to respond to the transient overvoltage suppression effect in the isolated island operation state and the island crossing demand within a limited time. The grid-forming unit maintains the off-grid system from becoming unstable, and the energy storage unit stores the unbalanced active power energy of the off-grid system at the same time. In the short period after the system is off-grid, the grid-forming wind turbine controls the voltage of the entire field, and the field-level control controls the wind turbine to shut down in an orderly manner until the system is restored, thereby finally achieving the operation stability and island crossing of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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.

[0021] 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 schematic diagram of the structure of the offshore wind farm transmission system in Example 2; Figure 4 This is a schematic diagram of the main circuit of a wind turbine generator set integrated with an energy storage unit in Example 2; Figure 5 It is a structural schematic diagram of the computer device of the present invention. DETAILED DESCRIPTION

[0022] 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.

[0023] Embodiment 1: like Figure 1 As shown: A low-frequency wind turbine and wind farm island crossing method, comprising the following steps: Based on low-frequency transmission technology, wind farms are networked using grid-building low-frequency wind turbines and grid-following low-frequency wind turbines, and power storage units are integrated into the grid-building low-frequency wind turbines. Real-time acquisition of the closing state signal of the main circuit breaker on the high and low voltage sides of the main transformer and the blocking signal of the power electronic device of the modular multi-level matrix M3C converter. If any signal is disconnected, the wind farm enters the island working mode; In the island working mode, the total active power balance state of the off-grid system is calculated in real time to obtain the power difference between the active power and the load, and a power command is generated accordingly; Scanning the operating status of the grid-forming low-frequency wind turbines in operation in real time, and issuing droop control mode instructions and power instructions to the grid-forming low-frequency wind turbines accordingly, so that the grid-forming low-frequency wind turbines maintain the system voltage and system frequency in the wind farm according to the droop control mode instructions, and control the energy storage units to absorb active power according to the power instructions; Track whether the real-time total active power is balanced. If not, update the power command and circulate the command process; if so, exit the wind farm island working mode.

[0024] Based on low-frequency transmission technology, the transmission capacity of the collection system can be improved, and the loss can be reduced, thereby reducing the transmission cost of offshore wind farms at long distances. Under the low-frequency transmission technology, the voltage suppression and island crossing effects of grid-type low-frequency wind turbines in the M3C locked or wind farm isolated grid operation state are introduced for the first time, and power storage units are integrated on the grid-type wind turbines to respond to the transient overvoltage suppression effect in the island operation state and the island crossing requirements within a limited time. The grid-type units maintain the off-grid system from instability, and the energy storage units store the unbalanced active power energy of the off-grid system at the same time. In the short period after the system is off-grid, the grid-type wind turbine controls the voltage of the entire field, and the field-level control controls the wind turbines to shut down in an orderly manner until the system is restored, ultimately achieving the operating stability and island crossing of the entire system.

[0025] In this embodiment, the real-time calculation of the total active power balance state of the off-grid system includes: Collect various parameters or power command values ​​required for power balance within the wind farm in real time, and calculate the total active power based on the collected parameters and power command values; By making the total active power zero, the total active power balance state is determined.

[0026] Real-time collection of various parameters or power command values ​​required for internal power balance of wind farms, including: The power command value Pref_gfm of the grid-building type low-frequency wind turbine that can be operated, the power command value Pref_gfl of the grid-following type low-frequency wind turbine that can be operated, the instantaneous power dissipation value Pchop of the chopper of the grid-following / grid-building type low-frequency wind turbine that can be operated, and the total limit value P_bess of the rechargeable standby capacity of the energy storage unit of the grid-building type low-frequency wind turbine that can be operated; Calculate the total active power P: P=Pref_gfl+Pref_gfm-Pchop-P_bess.

[0027] Wherein, a droop control mode instruction and a power instruction are issued to the grid-type low-frequency wind turbine generator set, so that the system voltage and system frequency in the wind farm are maintained according to the droop control mode instruction, and the energy storage unit is controlled to absorb active power according to the power instruction, including: The grid-type low-frequency wind turbine generator set reduces the internal potential amplitude and phase angle, and realizes power back absorption to the DC bus; The energy storage unit absorbs active power including: the energy storage unit performs charging mode conversion, absorbs active power, and aims to balance the total active power of the off-grid system.

[0028] As a preferred embodiment of the above, the process of updating the power instruction and issuing the instruction cyclically also includes: Starting timing while updating the power instruction; If the timing exceeds the set time, and the difference between the real-time active power and the load power exceeds the power corresponding to the highest transient overvoltage set by the wind turbine, the entire site will enter the shutdown process.

[0029] In this embodiment, the power instruction is updated and the instruction is issued cyclically, and the following steps are also included: Consider the charging capacity limit of the energy storage unit; If the total active power of the off-grid system is still not balanced after reaching the limit, the power command value of the grid-following low-frequency wind turbine will be reduced.

[0030] like Figure 2 As shown, this embodiment also includes a low-frequency wind turbine and a wind farm island ride-through system, using the above method, the system includes: Wind farm networking system: The wind farm networking system is based on low-frequency transmission technology, using grid-building low-frequency wind turbines and grid-following low-frequency wind turbines to network the wind farm, and integrating power storage units in the grid-building low-frequency wind turbines; The acquisition unit is used to collect the closing state signal of the main circuit breaker on the high and low voltage sides of the main transformer and the locking signal of the power electronic device of the modular multi-level matrix M3C converter in real time. If any signal is disconnected, the wind farm enters the island working mode; A calculation unit is used to calculate the total active power balance state of the off-grid system in real time in the island working mode, obtain the power difference between the active power and the load, and generate a power command accordingly; A control unit is used to scan the operating status of the grid-forming low-frequency wind turbine in operation in real time, and issue a droop control mode instruction and a power instruction to the grid-forming low-frequency wind turbine accordingly, so that the grid-forming low-frequency wind turbine maintains the system voltage and system frequency in the wind farm according to the droop control mode instruction, and controls the energy storage unit to absorb active power according to the power instruction; The control unit is also used to track whether the real-time total active power is balanced. If not, the power command is updated and the command issuing process is cyclical; if so, the wind farm island working mode is exited.

[0031] Among them, the power energy storage unit is a fast-charging and fast-discharging power energy storage unit.

[0032] Embodiment 2: like Figure 3 As shown, this embodiment includes a low-frequency wind turbine and a wind farm system, and proposes a wind farm system-level networking solution based on low-frequency transmission technology, a grid-forming low-frequency wind turbine, and a grid-following low-frequency wind turbine, which is the first in the field of low-frequency wind power solutions; a low-frequency wind power transmission control and protection solution based on fast communication technology is proposed, such as Figure 3 As shown by the red dotted line in the figure, this is the first time it has been mentioned in the field of low-frequency wind power solutions.

[0033] based on Figure 3 The flexible low-frequency system solution shown in the figure, and around the problems of overvoltage faults and island crossing existing in technical route 3, a wind-storage integrated design solution based on power-type energy storage units is proposed, such as Figure 4 As shown: Its core solution is to integrate low-frequency wind turbines and power energy storage units into a low-frequency wind-storage integrated machine main circuit solution.

[0034] based on Figure 3 The flexible low-frequency system solution shown in the figure proposes an island ride-through method to solve the problems of transient overvoltage and island ride-through in technical route 3: Step 1: The wind farm control system reads the closing status signal of the main circuit breaker on the high and low voltage sides of the main transformer and the locking signal of the M3C converter power electronic device in real time (sampling frequency should be <1ms), and performs an "or" calculation. If any signal is in the disconnected (high level) state, the wind farm enters the island working mode. Because of the supporting fast communication link, communication with a sampling frequency of <1ms becomes feasible.

[0035] Step 2: The wind farm control system calculates in real time the various parameters or power command values ​​required for real-time power balance within the wind farm. The command values ​​collected include: The power command value Pref_gfm of the operational grid-type unit; The power command value Pref_gfl of the grid-following type unit can be operated; The instantaneous power dissipation value Pchop of the chopper of the operational / grid-type unit; The total limit value P_bess of the rechargeable backup capacity of the energy storage unit of the operational grid-connected unit; Because of the fast communication link, the command update speed of <1ms becomes feasible, and the wind farm control system can monitor each wind turbine in real time.

[0036] Step 3: The wind farm control and dispatching system calculates the total active power balance state of the off-grid system, obtains the power difference between the power source (active power of wind turbines) and the load (energy storage rechargeable reserve capacity of grid-forming units + chopper dissipated active power), and generates power instructions accordingly to calculate P, with the goal of making P=0; P=Pref_gfl+Pref_gfm-Pchop-P_bess; Step 4: The wind farm control system scans the operating status of the grid-connected wind turbines in real time, and issues droop control mode instructions and Pref_gfl to the grid-connected wind turbines accordingly. The grid-connected wind turbines maintain the system voltage and system frequency in the wind farm according to the instructions, and respond to the power output instructions of the grid-connected units. The grid-connected units control to reduce the internal potential amplitude and phase angle to achieve power back to the DC bus. The DC bus energy storage module performs charging mode conversion to absorb active power. The goal is to achieve real-time P=0 off-grid system power balance. Step 5: The wind farm control system tracks the real-time power P to see if it is equal to zero. If it is not equal to zero, it returns to the third step to update the new instruction, and repeats this cycle. At the same time, the timing starts. If the accumulated time exceeds the specified time (such as the default value of the island crossing time requirement is 2 seconds), and P is greater than the overvoltage limit that the wind turbine can withstand, the whole farm will be shut down. Real-time power deviation P and allowable power deviation Pdelta; Pdelta corresponds to the transient overvoltage limit caused by power imbalance, that is, the maximum power deviation corresponding to the highest transient overvoltage that wind turbines and other equipment can withstand. If P is greater than Pref_gfl, the whole farm will be shut down.

[0037] During the off-grid system power balance period, the wind farm control system should consider the energy storage charging capacity limit. If the off-grid system power is still unbalanced after reaching the limit, the system should control the power command value of the grid-following unit to drop to the new limit after power balance.

[0038] Power balance is achieved by linear regulation. During this period, the grid-connected units maintain the off-grid system from becoming unstable, and the energy storage also stores the unbalanced active power energy of the off-grid system.

[0039] During the short period after the system is off-grid, the grid-type wind turbines control the voltage of the entire field, and the field-level control controls the wind turbines to shut down in an orderly manner until the system is restored, ultimately achieving operational stability and island crossing of the entire system.

[0040] Different from the conventional solution in which the wind turbine is a conventional wind turbine + conventional lithium battery and other energy storage solutions, the wind turbine in this embodiment is a low-frequency wind turbine, and the energy storage unit is a fast-charging and fast-discharging power energy storage unit such as a supercapacitor, so as to respond to the transient overvoltage suppression effect in the island operation state and the island crossing demand within a limited time.

[0041] See also Figure 5 A computer device 400 provided in an embodiment of the present application includes: a processor 410 and a memory 420, wherein the memory 420 stores a computer program executable by the processor 410, and when the computer program is executed by the processor 410, the above method is executed.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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 turbine and wind farm island crossing method, characterized in that: The steps include: Based on low-frequency transmission technology, wind farms are networked using grid-building low-frequency wind turbines and grid-following low-frequency wind turbines, and power storage units are integrated into the grid-building low-frequency wind turbines. Real-time acquisition of the closing state signal of the main circuit breaker on the high and low voltage sides of the main transformer and the blocking signal of the power electronic device of the modular multi-level matrix M3C converter. If any signal is disconnected, the wind farm enters the island working mode; In the island working mode, the total active power balance state of the off-grid system is calculated in real time to obtain the power difference between the active power and the load, and a power command is generated accordingly; Scanning the operating status of the grid-forming low-frequency wind turbines in operation in real time, and issuing a droop control mode instruction and the power instruction to the grid-forming low-frequency wind turbines accordingly, so that the grid-forming low-frequency wind turbines maintain the system voltage and system frequency in the wind farm according to the droop control mode instruction, and control the energy storage unit to absorb active power according to the power instruction; Track whether the real-time total active power is balanced. If not, update the power command and circulate the command process; if yes, exit the wind farm island working mode.

2. The low-frequency wind turbine and wind farm island crossing method according to claim 1 is characterized in that: The real-time calculation of the total active power balance state of the off-grid system includes: Collect various parameters or power command values ​​required for power balance within the wind farm in real time, and calculate the total active power based on the collected parameters and power command values; By making the total active power zero, the total active power balance state is determined.

3. The low-frequency wind turbine generator set and wind farm island crossing method according to claim 2 is characterized in that: The real-time collection of various parameters or power command values ​​required for power balance within the wind farm, and calculation of total active power based on the collected parameters and power command values, include: Real-time collection of the power command value Pref_gfm of the operational grid-building low-frequency wind turbine, the power command value Pref_gfl of the operational grid-following low-frequency wind turbine, the instantaneous power dissipation value Pchop of the chopper of the operational grid-following / grid-building low-frequency wind turbine, and the total limit value P_bess of the rechargeable standby capacity of the energy storage unit of the operational grid-building low-frequency wind turbine; The total active power P is calculated by the following formula: P=Pref_gfl+Pref_gfm-Pchop-P_bess.

4. The low-frequency wind turbine generator set and wind farm island crossing method according to claim 1, characterized in that: The step of issuing the droop control mode instruction and the power instruction to the grid-type low-frequency wind turbine generator set so that the grid-type low-frequency wind turbine generator set maintains the system voltage and system frequency in the wind farm according to the droop control mode instruction and controls the energy storage unit to absorb active power according to the power instruction, including: The grid-type low-frequency wind turbine generator set reduces the internal potential amplitude and phase angle, and realizes power back absorption to the DC bus; The energy storage unit absorbing active power includes: the energy storage unit converts the charging mode to absorb active power, aiming to balance the total active power of the off-grid system.

5. The low-frequency wind turbine generator set and wind farm island crossing method according to claim 4 is characterized in that: The process of updating the power instruction and issuing the instruction cyclically also includes: Starting timing while updating the power instruction; If the timing exceeds the set time, and the difference between the real-time active power and the load power exceeds the power corresponding to the highest transient overvoltage set by the wind turbine, the entire site will enter the shutdown process.

6. The low-frequency wind turbine generator set and wind farm island crossing method according to claim 4 is characterized in that: The updating of the power instruction and the process of issuing the instruction cyclically also include: Consider the charging capacity limit of the energy storage unit; If the total active power of the off-grid system is still not balanced after reaching the limit, the power command value of the grid-following low-frequency wind turbine will be reduced.

7. A low-frequency wind turbine and wind farm island ride-through system, characterized in that: Using the method according to any one of claims 1 to 6, the system comprises: A wind farm networking system, which is based on low-frequency transmission technology, uses a networking type low-frequency wind turbine and a grid-following type low-frequency wind turbine to network the wind farm, and integrates a power storage unit in the networking type low-frequency wind turbine; The acquisition unit is used to collect the closing state signal of the main circuit breaker on the high and low voltage sides of the main transformer and the locking signal of the power electronic device of the modular multi-level matrix M3C converter in real time. If any signal is disconnected, the wind farm enters the island working mode; A calculation unit, used for calculating the total active power balance state of the off-grid system in real time in the island working mode, obtaining the power difference between the active power and the load, and generating a power instruction accordingly; A control unit, used for scanning the operating status of the grid-forming low-frequency wind turbine in operation in real time, and issuing a droop control mode instruction and the power instruction to the grid-forming low-frequency wind turbine accordingly, so that the grid-forming low-frequency wind turbine maintains the system voltage and system frequency in the wind farm according to the droop control mode instruction, and controls the energy storage unit to absorb active power according to the power instruction; The control unit is also used to track whether the real-time total active power is balanced. If not, the power command is updated and the command issuing process is cyclical; if yes, the wind farm island working mode is exited.

8. The low-frequency wind turbine generator set and wind farm island ride-through system according to claim 7, characterized in that: The power energy storage unit is a fast-charge and fast-discharge power energy storage unit.

9. 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 6 is implemented.

10. 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 6 is implemented.

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