Medium-voltage doubly-fed wind turbine generator stand-alone reactive closed-loop control method and device and medium

Abstract

The invention discloses a medium-voltage doubly-fed wind turbine generator single-machine reactive closed-loop control method and device and a medium. Relates to the field of wind power generation, and solves the problems that the traditional reactive closed-loop control has strong dependence on a station-level system and cannot adapt to independently complete the reactive closed-loop control requirement of a single machine. Real-time reactive power loss and unit reactive power are calculated by directly collecting real-time electrical parameters of the medium-voltage side and the low-voltage side of the transformer and combining inherent parameters of the transformer, and accurate quantification of the reactive power loss of the transformer is achieved. And taking the deviation between the reactive power of the unit and the corrected reactive value as a compensation basis, dynamically generating a compensation amount, and forming feedback regulation of the deviation and the reactive compensation value. And finally, the reactive instruction not only comprises basic loss compensation, but also is superposed with dynamic correction, so that the output of the converter is ensured to be accurately matched. The reactive power loss of the transformer is actively compensated only through the single-machine layer of the wind turbine generator, and high-frequency data interaction with a wind power plant energy management system is not needed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wind power generation, in particular to a medium-voltage doubly-fed wind turbine unit single-machine reactive power closed-loop control method, device and medium. BACKGROUND

[0002] As a core clean energy, wind power continues to increase in the energy structure, and the industry focus shifts to the deep sea. Deep-sea wind power is mostly transmitted by flexible HVDC. The offshore converter station converts wind power AC into high-voltage DC, which is transmitted to the onshore converter station by DC submarine cable and then converted into AC and connected to the main grid. HVDC does not have reactive power transmission capability, which directly changes the reactive power control requirements of wind turbine units. In this scenario, if the wind turbine outlet reactive power is 0, only a small-capacity static var generator (SVG) needs to be configured to meet the basic requirements.

[0003] The traditional reactive power regulation method of the wind farm is that the automatic voltage control (AVC) system of the station level takes the voltage at the grid connection point of the wind farm as the basis to calculate and determine the total reactive power demand of the entire farm, and then distributes the reactive power instructions to the static var generator (SVG) and the wind turbine energy management (energy management) system. The energy management system then decomposes the total reactive power instruction into single-machine reactive power instructions for each wind turbine according to the actual conditions of the units. The wind turbine adjusts the output through the generator stator side (doubly-fed wind turbine) or converter network side (full-power wind turbine) according to the single-machine reactive power instruction issued by the energy management system to achieve the corresponding reactive power output.

[0004] Considering that the wind turbine itself, the single-machine step-up transformer, the internal cable of the tower, the power collection line, and the main transformer all have reactive power losses, the "split measurement point closed-loop compensation" is adopted: the energy management system takes the low-voltage side of the single-machine step-up transformer as the measurement point to adjust the single-machine reactive power instruction and compensate for the reactive power losses of the wind turbine itself and the internal cable of the tower; the AVC system takes the grid connection point of the wind farm as the measurement point to adjust the reactive power instruction issued to the SVG and the energy management system, and compensates for the reactive power losses of the single-machine step-up transformer, the power collection line, and the main transformer.

[0005] As the proportion of wind power in the power system continues to increase, the grid requires more active support from units. In some scenarios, wind turbine units are required to independently complete single-machine reactive power closed-loop control, free from dependence on station-level systems, significantly improve the reactive power compensation response speed, and meet the requirements of active grid support.

[0006] Therefore, it is a technical problem that needs to be solved in the field to provide a medium-voltage doubly-fed wind turbine unit that can independently complete single-machine reactive power closed-loop control relying on existing reactive power measurement equipment and adjustment capabilities. SUMMARY

[0007] The application aims to provide a medium-voltage doubly-fed wind turbine single-machine reactive power closed-loop control method, device and medium, solve the problem that the traditional reactive power closed-loop control is strongly dependent on the field station level system and cannot adapt to the demand of independently completing single-machine reactive power closed-loop control.

[0008] To solve the above technical problems, the application provides a medium-voltage doubly-fed wind turbine single-machine reactive power closed-loop control method, which comprises the following steps:

[0009] Obtaining real-time electrical parameters of the medium-voltage side and the low-voltage side of the transformer of the doubly-fed wind turbine and inherent parameters of the transformer;

[0010] Obtaining real-time reactive power loss of the transformer and unit reactive power of the doubly-fed wind turbine according to the inherent parameters and the real-time electrical parameters;

[0011] Superimposing the real-time reactive power loss on an initial reactive power instruction input from outside to obtain a corrected reactive power value;

[0012] Determining a reactive power compensation value according to the deviation of the unit reactive power and the corrected reactive power value;

[0013] Superimposing the corrected reactive power value and the reactive power compensation value to obtain a final reactive power instruction and issuing the final reactive power instruction to the converter of the doubly-fed wind turbine.

[0014] As an optional solution, in the above-mentioned medium-voltage doubly-fed wind turbine single-machine reactive power closed-loop control method, the step of obtaining the real-time electrical parameters of the medium-voltage side and the low-voltage side of the transformer of the doubly-fed wind turbine and the inherent parameters of the transformer comprises the following steps:

[0015] Collecting real-time current value, voltage value and reactive power of the medium-voltage side of the transformer;

[0016] Collecting real-time current value, voltage value and reactive power of the low-voltage side of the transformer;

[0017] Obtaining preset actual reactance value and no-load reactive power value of the transformer.

[0018] As an optional solution, in the above-mentioned medium-voltage doubly-fed wind turbine single-machine reactive power closed-loop control method, the step of obtaining real-time reactive power loss of the transformer and unit reactive power of the doubly-fed wind turbine according to the inherent parameters and the real-time electrical parameters comprises the following steps:

[0019] Obtaining real-time reactive power loss of the transformer according to the first formula, actual reactance value, no-load reactive power value and real-time electrical parameters of the transformer;

[0020] The first formula is:

[0021] ;

[0022] In the formula, This refers to the real-time reactive power loss of the transformer. This represents the no-load reactive power value of the transformer. , , These represent the actual reactance values ​​of the low-voltage side, medium-voltage side, and high-voltage side of the transformer, respectively. , , These represent the real-time current values ​​on the low-voltage, medium-voltage, and high-voltage sides of the transformer, respectively; where, It is based on , Obtained;

[0023] The reactive power of the unit is obtained by summing the reactive power on the medium-voltage side and the low-voltage side of the transformer.

[0024] As an optional solution, in the above-mentioned closed-loop reactive power control method for a single medium-voltage doubly-fed wind turbine, the reactive power compensation value is determined based on the reactive power of the unit and the deviation of the corrected reactive power value, including:

[0025] Every preset period, a reactive power deviation value is obtained based on the deviation between the unit's reactive power and the corrected reactive power value.

[0026] Based on the comparison result between the reactive power deviation value and the preset reactive power compensation allowable deviation threshold, the current reactive power compensation value is updated.

[0027] Based on the comparison between the updated reactive power compensation value and the preset reactive power compensation boundary threshold, it is determined whether the updated reactive power compensation value needs to be restricted and adjusted.

[0028] If not, output the updated reactive power compensation value and proceed to the next step;

[0029] If so, the updated reactive power compensation value will be adjusted, and the adjusted reactive power compensation value will be used to proceed to the next step.

[0030] As an optional solution, in the above-mentioned single-unit reactive power closed-loop control method for medium-voltage doubly-fed wind turbines, the step of updating the current reactive power compensation value based on the comparison result between the reactive power deviation value and the preset reactive power compensation allowable deviation threshold includes:

[0031] The preset reactive power compensation allowable deviation threshold is the range from the minimum preset reactive power compensation allowable deviation to the maximum preset reactive power compensation allowable deviation.

[0032] If the reactive power deviation value is greater than the preset maximum allowable reactive power compensation deviation value, then the current reactive power compensation value is superimposed with the preset positive compensation amount to obtain the updated reactive power compensation value.

[0033] if the reactive power deviation value is less than the preset reactive power compensation allowable deviation minimum value, subtracting a preset positive compensation amount from a current reactive power compensation value to obtain an updated reactive power compensation value;

[0034] if the reactive power deviation value is between the preset reactive power compensation allowable deviation maximum value and the preset reactive power compensation allowable deviation minimum value, keeping the current reactive power compensation value unchanged.

[0035] As an optional solution, in the above medium-voltage doubly-fed wind turbine unit reactive power closed-loop control method, based on a comparison result of the updated reactive power compensation value and a preset reactive power compensation boundary threshold value, it is determined whether the updated reactive power compensation value needs to be adjusted by limitation, comprising:

[0036] The preset reactive power compensation boundary threshold value is an interval of a preset reactive power compensation upper limit value and a preset reactive power compensation lower limit value;

[0037] if the updated reactive power compensation value is greater than the preset reactive power compensation upper limit value or the updated reactive power compensation value is less than the preset reactive power compensation lower limit value, it is determined that the reactive power compensation value needs to be adjusted by limitation;

[0038] if the updated reactive power compensation value is between the preset reactive power compensation lower limit value and the preset reactive power compensation upper limit value, it is determined that the reactive power compensation value does not need to be adjusted by limitation.

[0039] As an optional solution, in the above medium-voltage doubly-fed wind turbine unit reactive power closed-loop control method, the updated reactive power compensation value is adjusted by limitation, comprising:

[0040] if the updated reactive power compensation value is greater than the preset reactive power compensation upper limit value, the reactive power compensation value is adjusted to the preset reactive power compensation upper limit value;

[0041] if the updated reactive power compensation value is less than the preset reactive power compensation lower limit value, the reactive power compensation value is adjusted to the preset reactive power compensation lower limit value.

[0042] To solve the above technical problems, the application also provides a medium-voltage doubly-fed wind turbine unit reactive power closed-loop control device, comprising:

[0043] an acquisition module, configured to acquire real-time electrical parameters of a medium-voltage side and a low-voltage side of a transformer of a doubly-fed wind turbine unit, and inherent parameters of the transformer;

[0044] a calculation module, configured to obtain real-time reactive power loss of the transformer and unit reactive power of the doubly-fed wind turbine unit according to the inherent parameters and the real-time electrical parameters;

[0045] a correction module, configured to add the real-time reactive power loss to an initial reactive power instruction input from outside to obtain a corrected reactive power value;

[0046] The compensation module determines the reactive power compensation value based on the reactive power of the unit and the deviation of the corrected reactive power value.

[0047] The execution module sends the superposition result of the corrected reactive power value and the reactive power compensation value as the final reactive power command to the converter of the doubly fed wind turbine.

[0048] To address the aforementioned technical problems, this application also provides a closed-loop reactive power control device for a single unit of a medium-voltage doubly-fed wind turbine, comprising:

[0049] Memory, used to store computer programs;

[0050] The processor is used to execute the computer program to implement the steps of the above-described closed-loop reactive power control method for a single unit of a medium-voltage doubly-fed wind turbine.

[0051] To address the aforementioned technical problems, this application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the aforementioned closed-loop reactive power control method for a single medium-voltage doubly-fed wind turbine generator.

[0052] The medium-voltage doubly-fed induction generator (DFIG) wind turbine single-unit reactive power closed-loop control method provided in this application directly collects real-time electrical parameters from the medium-voltage and low-voltage sides of the transformer, and calculates real-time reactive power loss and unit reactive power by combining the transformer's inherent parameters, thus achieving precise quantification of the transformer's own reactive power loss. The deviation between the unit's reactive power and the corrected reactive power value is used as the basis for compensation, dynamically generating compensation amounts to form a feedback adjustment between the deviation and the reactive power compensation value. The final reactive power command includes both basic loss compensation and a dynamically adjusted amount, ensuring that the converter output accurately matches the requirements. This application achieves active compensation of transformer reactive power loss only at the wind turbine single-unit level. The control logic relies solely on parameter acquisition and local calculation on both sides of the transformer, eliminating the need for high-frequency data interaction with the wind farm's energy management system. This reduces the reactive power regulation tasks that would otherwise be undertaken by the wind farm's collection system or converter station, lowering the capacity requirements for station-level reactive power compensation equipment and thus saving on the overall construction and operation costs of the wind farm.

[0053] In addition, this application also provides a device and medium that correspond to the above-mentioned single-unit reactive power closed-loop control method for medium-voltage doubly fed wind turbine generators, with the same effect. Attached Figure Description

[0054] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This application provides a flowchart of a single-unit reactive power closed-loop control method for a medium-voltage doubly-fed wind turbine generator set.

[0056] Figure 2 A single-line diagram of the electrical system of a medium-voltage doubly-fed wind turbine generator set is provided for embodiments of this application;

[0057] Figure 3 A schematic diagram of a control logic provided in an embodiment of this application;

[0058] Figure 4 This is a topology diagram of a flexible DC-DC offshore wind power system.

[0059] Figure 5 A comparison diagram of reactive power commands and fan outlet reactive power curves for a single-unit reactive power closed-loop control provided in this application;

[0060] Figure 6 A structural diagram of a single-unit reactive power closed-loop control device for a medium-voltage doubly-fed wind turbine generator provided in this application embodiment;

[0061] Figure 7 A structural diagram of another medium-voltage doubly fed wind turbine single-unit reactive power closed-loop control device provided in this application embodiment. Detailed Implementation

[0062] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0063] The core of this application is to provide a method, device, and medium for closed-loop reactive power control of a single unit of a medium-voltage doubly-fed wind turbine.

[0064] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] As one of the most promising clean energy sources, wind power is rapidly increasing its share in China's and the global energy mix. With wind energy resources in traditionally easily developed areas becoming increasingly saturated, the wind power industry is shifting its strategic focus to desert and barren areas and deep-sea regions with larger wind energy reserves.

[0066] Because long-distance AC power transmission is limited by the charging power of submarine cables, offshore wind power projects are increasingly adopting flexible DC transmission. The converter station at the offshore wind farm's collection point converts the AC power generated by the wind farm into high-voltage DC, which is then transmitted via DC submarine cables. It is then inverted back into AC power at an onshore converter station and fed into the main AC grid. High-voltage DC does not conduct reactive power, and this change in the wind farm's transmission system has also brought new changes to the reactive power control mode of wind turbine units.

[0067] Traditional wind farm reactive power regulation typically involves a site-level automatic voltage control (AVC) system that determines the overall reactive power command based on the grid connection voltage of the wind farm and distributes it to the static var generator (SVG) and the wind turbine energy management system (energy management system). The energy management system then distributes the overall reactive power command to each wind turbine, which in turn responds to the individual turbine reactive power command by issuing the corresponding reactive power value on the generator stator side (doubly fed wind turbine) or converter grid side (full-power wind turbine). Since the electrical components of the wind turbine itself, the single-unit step-up transformer, the internal cables of the wind turbine tower, the collector lines, and the main transformer all have reactive power losses, the energy management system and the AVC perform closed-loop control of reactive power based on their respective reactive power measurement points: the energy management system adjusts the reactive power command of each wind turbine based on the reactive power of each wind turbine (the measurement point is located on the low-voltage side of the single-unit step-up transformer) to compensate for the reactive power of the wind turbine's own electrical components and the internal cables of the wind turbine tower; the AVC adjusts the reactive power of the grid connection point and issues reactive power commands to the SVG and the energy management system to compensate for the reactive power losses of the single-unit step-up transformer, the collector lines, and the main transformer.

[0068] For wind farms using flexible DC transmission, offshore wind farms do not have main transformers. Offshore converter stations can achieve AC voltage control through IGBTs (Inverter Gauges for Power Transfer). Furthermore, offshore wind farms have short AC lines with low line losses. If the wind turbine's own reactive power output is zero, the offshore converter station only needs to install a small-capacity SVG for black-start grid connection, providing initial voltage support, assisting the flexible DC converter station in rapid recovery, and compensating for a small amount of collector line losses when needed. As the proportion of wind power in the power system increases, the grid's requirements for the grid adaptability and active support of wind turbine units are becoming increasingly stringent. The reactive power control mode traditionally used by wind farms for reactive power closed-loop control and compensation through field-level energy management systems can no longer meet grid requirements. Taking Zhejiang Province as an example, Zhejiang's direct-connection wind farms require wind turbine units to complete single-unit reactive power closed-loop control themselves to quickly compensate for the reactive power losses of the wind turbine units.

[0069] Currently, reactive power compensation for single-unit wind turbines is mostly achieved by energy management systems, which requires bidirectional communication between the turbine and the energy management system, as well as collaborative calculations between the energy management system and multiple wind turbines, etc., which is time-consuming. A single-unit autonomous reactive power closed-loop system eliminates unnecessary processes and provides faster adjustment.

[0070] To address the aforementioned problems, embodiments of this application provide a closed-loop reactive power control method for a single unit of a medium-voltage doubly-fed wind turbine, such as... Figure 1 As shown, it includes:

[0071] S1: Obtain the real-time electrical parameters of the medium-voltage side and low-voltage side of the transformer of the doubly fed wind turbine generator set, as well as the inherent parameters of the transformer;

[0072] S2: Based on inherent parameters and real-time electrical parameters, obtain the real-time reactive power loss of the transformer and the reactive power of the doubly-fed wind turbine unit;

[0073] S3: The real-time reactive power loss is superimposed on the initial reactive power command input by the external input to obtain the corrected reactive power value;

[0074] S4: Determine the reactive power compensation value based on the unit's reactive power and the deviation of the corrected reactive power value;

[0075] S5: The result of the superposition of the corrected reactive power value and the reactive power compensation value is used as the final reactive power command and sent to the converter of the doubly fed wind turbine.

[0076] Figure 2 A single-line diagram of the electrical system of a medium-voltage doubly-fed wind turbine generator set is provided for embodiments of this application, such as... Figure 2 As shown, the 10.5kV side of the single transformer connected to the stator (Figure 101) is the medium voltage side, the 1140V side connected to the grid-side converter (Figure 103) is the low voltage side, and the side connected to the grid is the high voltage side 66kV (Figure 105).

[0077] Step S1 forms the data foundation of the entire control method, with its core being the acquisition of parameters across the entire chain. The acquisition of real-time electrical parameters is explicitly limited to the medium-voltage and low-voltage sides of the transformer, as these two measurement points directly reflect the transformer's input and output states. Inherent parameters, on the other hand, are the transformer's own physical properties, which do not change with operating conditions and can be obtained by querying factory data.

[0078] First, the specific types of real-time electrical parameters are not unique, but generally include, but are not limited to: three-phase voltage, three-phase current, active power, and reactive power on the medium-voltage side, and three-phase voltage, three-phase current, active power, and reactive power on the low-voltage side. It should be noted that three-phase parameters are collected instead of single-phase parameters because wind power systems are three-phase AC systems, and three-phase parameters can more comprehensively reflect the system status.

[0079] Secondly, the inherent parameters typically include: the transformer's rated capacity, rated voltage ratio, no-load reactive power loss, and short-circuit reactance (including high-voltage side reactance, medium-voltage side reactance, and low-voltage side reactance). This doesn't mean that only these parameters are included; depending on the transformer type, parameters such as winding resistance may also be included. The specific parameters should be selected based on the calculation requirements.

[0080] On the other hand, there are multiple implementation paths for parameter acquisition: voltage and current signals can be obtained through current transformers (CTs) and voltage transformers (PTs) installed on the medium-voltage and low-voltage sides of the transformer, and then power parameters can be calculated through a data acquisition unit (DAU); alternatively, processed power parameters can be directly obtained through the transformer's built-in intelligent terminal. This embodiment does not impose strict limitations.

[0081] Step S2 obtains the real-time reactive power loss of the transformer and the reactive power of the doubly-fed wind turbine based on the inherent parameters and real-time electrical parameters, which is used to transform the original collected data into key variables required for control.

[0082] First, when calculating the real-time reactive power loss of a transformer, it is necessary to consider both the transformer's inherent characteristics and the real-time load status. Specifically, it can be calculated as follows: Real-time reactive power loss = No-load reactive power loss (inherent parameters) + Load reactive power loss, where the load reactive power loss is calculated based on the short-circuit reactance in the inherent parameters and the current in the real-time electrical parameters. Alternatively, other calculation models based on the principle of electromagnetic induction can be used, as long as they reflect the superposition characteristics of no-load loss and load loss.

[0083] Secondly, the reactive power of the generator set refers to the reactive power output on both the medium-voltage and low-voltage sides of the integrated transformer. Generally speaking, the generator set's reactive power = real-time reactive power on the medium-voltage side + real-time reactive power on the low-voltage side. It should be noted that this calculation method reflects the concept of "overall reactive power output of a single unit," comprehensively reflecting the unit's reactive power capacity.

[0084] Furthermore, the calculation frequency should match the parameter acquisition frequency in S1 to ensure data real-time performance. At this point, both real-time reactive power loss and unit reactive power are dynamically updated values, not fixed values.

[0085] Step S3 adds the real-time reactive power loss to the externally input initial reactive power command to obtain the corrected reactive power value, the purpose of which is to reserve the amount of loss compensation in advance.

[0086] First, the initial reactive power command input from the outside usually comes from the wind farm's energy management system (EMS) or grid dispatch command, representing the grid's reactive power demand on the wind turbine outlet (high-voltage side of the transformer). For example, in a flexible direct transmission scenario, the initial reactive power command is usually 0, requiring zero reactive power at the wind turbine outlet (position 105).

[0087] Secondly, the real-time reactive power loss is added to the initial reactive power command, meaning the corrected reactive power value = initial reactive power command + real-time reactive power loss. The physical meaning of this operation is that the converter needs to output additional reactive power equal to the transformer's real-time reactive power loss to ensure that, after deducting transformer losses, the reactive power reaching the grid equals the initial command. For example, if the initial command is 0 and the real-time reactive power loss is 50 kvar, then the corrected reactive power value is 50 kvar, meaning the converter needs to output an additional 50 kvar to offset the transformer losses.

[0088] On the other hand, the timing of the superposition operation should be consistent with the update frequency of real-time reactive power loss in S2 to ensure that the corrected reactive power value can dynamically track changes in loss. Based on the above principle, the corrected reactive power value is a real-time dynamically adjusted value, rather than a fixed value.

[0089] Step S4 determines the reactive power compensation value based on the unit's reactive power and the deviation of the corrected reactive power value, so as to achieve precise control through deviation adjustment.

[0090] First, the deviation is calculated as follows: Deviation value = Corrected reactive power value - Generator reactive power. This deviation value reflects the difference between the current generator reactive power output and the target value. For example, if the corrected reactive power value is 50 kvar and the generator reactive power is 40 kvar, then the deviation value is 10 kvar, indicating that an increase of 10 kvar in reactive power output is needed.

[0091] Secondly, there are several lower-level implementation methods for determining the specific strategy of reactive power compensation value: proportional adjustment: compensation value = proportional coefficient × deviation value; step adjustment: when the deviation value is greater than the first threshold, the compensation value is a fixed large step size; when the deviation value is less than the second threshold, the compensation value is a fixed small step size; integral adjustment: the compensation value changes cumulatively with the duration of the deviation. This embodiment does not impose strict limitations, as long as the compensation amount can be dynamically adjusted according to the deviation value.

[0092] Step S5 sends the result of the superposition of the corrected reactive power value and the reactive power compensation value as the final reactive power command to the converter of the doubly fed wind turbine, and converts the previous calculation results into equipment action commands.

[0093] The final reactive power command equals the corrected reactive power value plus the reactive power compensation value. The final command includes both the basic amount to offset transformer losses (corrected reactive power value) and the adjustment amount to eliminate real-time deviations (reactive power compensation value), ensuring that the converter output accurately meets system requirements. Commands are typically issued through the converter's communication interface; this embodiment does not impose restrictions on this method. It should be noted that issuing the command does not end the control flow, but rather marks the beginning of a new round of closed-loop control. After the converter executes the command, its output reactive power will re-enter the control flow through parameter acquisition in S1, forming continuous closed-loop regulation.

[0094] The medium-voltage doubly-fed induction generator (DFIG) wind turbine single-unit reactive power closed-loop control method provided in this application directly collects real-time electrical parameters from the medium-voltage and low-voltage sides of the transformer, and calculates real-time reactive power loss and unit reactive power by combining the transformer's inherent parameters, thus achieving precise quantification of the transformer's own reactive power loss. The deviation between the unit's reactive power and the corrected reactive power value is used as the basis for compensation, dynamically generating compensation amounts to form a feedback adjustment between the deviation and the reactive power compensation value. The final reactive power command includes both basic loss compensation and a dynamically adjusted amount, ensuring that the converter output accurately matches the requirements. This application achieves active compensation of transformer reactive power loss only at the wind turbine single-unit level. The control logic relies solely on parameter acquisition and local calculation on both sides of the transformer, eliminating the need for high-frequency data interaction with the wind farm's energy management system. This reduces the reactive power regulation tasks that would otherwise be undertaken by the wind farm's collection system or converter station, lowering the capacity requirements for station-level reactive power compensation equipment and thus saving on the overall construction and operation costs of the wind farm.

[0095] According to the above embodiments, in one specific embodiment, obtaining the real-time electrical parameters of the medium-voltage side and low-voltage side of the transformer of the doubly-fed wind turbine, as well as the inherent parameters of the transformer, includes:

[0096] Collect real-time current, voltage, and reactive power values ​​on the medium-voltage side of the transformer;

[0097] Collect real-time current, voltage, and reactive power values ​​on the low-voltage side of the transformer;

[0098] Obtain the preset actual reactance value and no-load reactive power value of the transformer.

[0099] First, this embodiment defines real-time electrical parameters as current, voltage, and reactive power. It should be noted that current and voltage are the fundamental physical quantities for calculating power and losses, while directly collecting reactive power reduces subsequent calculations. Furthermore, the real-time nature of the data acquisition is reflected in the sampling frequency, which generally needs to match the grid frequency.

[0100] This embodiment limits the inherent parameters to the actual reactance value and the no-load reactive power value for real-time reactive power loss calculation. It should also be noted that the actual reactance value, rather than the rated reactance value, can be obtained through factory testing or field short-circuit testing, which can reduce system errors.

[0101] In a further specific embodiment, the real-time reactive power loss of the transformer and the reactive power of the doubly-fed wind turbine are obtained based on inherent parameters and real-time electrical parameters, including:

[0102] The real-time reactive power loss of the transformer is obtained based on the first formula, the actual reactance value of the transformer, the no-load reactive power value, and the real-time electrical parameters.

[0103] First formula:

[0104] ;

[0105] In the formula, This indicates the real-time reactive power loss of the transformer. This indicates the no-load reactive power value of the transformer. , , These represent the actual reactance values ​​of the low-voltage side, medium-voltage side, and high-voltage side of the transformer, respectively. , , These represent the real-time current values ​​on the low-voltage, medium-voltage, and high-voltage sides of the transformer, respectively; where, It is based on , Obtained;

[0106] The reactive power of the unit is obtained by summing the reactive power on the medium-voltage side and the low-voltage side of the transformer.

[0107] In the first formula, the conversion from single-phase loss to total three-phase loss is achieved through the coefficient 3. Of course, it is also possible to collect data for each phase separately and perform corresponding superposition calculations, but the computational workload is relatively larger. According to , It is obtained through ratio conversion.

[0108] The sum of the reactive power on the medium-voltage side and the low-voltage side of the transformer is taken as the unit's reactive power. The unit's reactive power reflects the current overall reactive power output status of the wind turbine.

[0109] According to the above embodiments, in one specific embodiment, determining the reactive power compensation value based on the unit's reactive power and the deviation of the corrected reactive power value includes:

[0110] Every preset cycle, the reactive power deviation value is obtained based on the unit's reactive power and the deviation of the corrected reactive power value.

[0111] The current reactive power compensation value is updated based on the comparison between the reactive power deviation value and the preset reactive power compensation allowable deviation threshold.

[0112] Based on the comparison between the updated reactive power compensation value and the preset reactive power compensation boundary threshold, it is determined whether the updated reactive power compensation value needs to be restricted and adjusted.

[0113] If not, output the updated reactive power compensation value and proceed to the next step;

[0114] If so, the updated reactive power compensation value will be adjusted, and the adjusted reactive power compensation value will be used to proceed to the next step.

[0115] The core of this embodiment is to determine the balance control accuracy and equipment safety in stages, so as to avoid frequent adjustments caused by instantaneous fluctuations and prevent the compensation value from exceeding the equipment's capacity range.

[0116] Generally, the preset cycle needs to match the parameter acquisition cycle mentioned earlier. A cycle that is too short will overload the computing power of the control unit, while a cycle that is too long will reduce the closed-loop response speed and make it impossible to compensate for reactive power fluctuations in a timely manner. It should be noted that the reactive power deviation value is calculated every cycle, and the reactive power deviation value is dynamically updated to ensure that the compensation value can track the deviation changes in real time.

[0117] Figure 3 A schematic diagram of control logic provided in an embodiment of this application, such as... Figure 3 As shown, the reactive power deviation value = corrected reactive power value - generator reactive power, reflecting the difference between the target value and the actual value. For example, if the corrected reactive power value is 60 kvar and the generator reactive power is 52 kvar, then the deviation value is 8 kvar, indicating that the current generator output has not met the target and the gap needs to be made up through compensation. It should be emphasized that the positive and negative reactive power values ​​in this embodiment have clear physical meanings: positive reactive power represents capacitive reactive power, and negative reactive power represents inductive reactive power; correspondingly, a positive reactive power deviation value represents compensation for capacitive reactive power, and a negative reactive power deviation value represents compensation for inductive reactive power.

[0118] Furthermore, the compensation value is updated based on a comparison between the deviation and the allowable deviation threshold. Over-adjustment is avoided through threshold judgment, ensuring a smooth compensation process. It should be noted that the preset allowable deviation threshold for reactive power compensation is a small range. Its function is to preset an acceptable deviation range. When the deviation is within the threshold, it means that the unit output is close to the target and does not require frequent adjustments. The compensation value is only updated when the deviation exceeds the threshold. This effectively avoids "oscillation" of the compensation value caused by measurement noise or small fluctuations.

[0119] The specific update rules need to be determined by considering the relationship between the deviation direction and the threshold, and do not mean that there is only a single update method. Figure 3 The reactive power closed-loop controller in the system performs this analysis and control. For example, proportional update: compensation value update amount = proportional coefficient × deviation value (e.g., proportional coefficient is 0.5). If the deviation value is 8kvar, then the update amount is 4kvar, and the current compensation value = original compensation value + 4kvar. This method adjusts more smoothly and is suitable for scenarios with small deviations and requiring fine control.

[0120] It should be noted that this embodiment does not limit the specific update method. An adaptation strategy can be selected according to the wind turbine model and grid requirements. If the deviation exceeds the threshold, it will be adjusted; otherwise, it will be stabilized, ensuring the necessity and stability of the compensation value update.

[0121] Finally, adjustments are made based on a comparison between the compensation value and the boundary threshold. Presetting a reactive power compensation boundary threshold is to prevent the compensation value from exceeding the physical capacity of the equipment. This typically includes an upper and lower limit for reactive power compensation. The boundary threshold acts as a "safety net," not implying that the compensation value will be frequently triggered, but rather preventing extreme deviations (such as a sudden increase in deviation due to a sharp drop in grid voltage) from causing the compensation value to exceed the converter's capacity and leading to equipment failure. Even if calculation errors occur in the preceding deviation judgment and update stages, the boundary threshold ensures that the final output compensation value is safe and controllable, preventing the converter from tripping due to overcurrent.

[0122] This embodiment first ensures real-time performance by periodically calculating the deviation, ensures stability by judging the allowable deviation threshold, and ensures safety by limiting the boundary threshold. These steps are progressively advanced to form a complete compensation value update logic chain.

[0123] In a further specific embodiment, the current reactive power compensation value is updated based on the comparison result between the reactive power deviation value and the preset reactive power compensation allowable deviation threshold, including:

[0124] The preset reactive power compensation allowable deviation threshold is the range from the preset minimum reactive power compensation allowable deviation to the preset maximum reactive power compensation allowable deviation.

[0125] If the reactive power deviation value is greater than the preset maximum allowable reactive power compensation deviation value, the current reactive power compensation value will be superimposed with the preset positive compensation amount to obtain the updated reactive power compensation value.

[0126] If the reactive power deviation value is less than the preset minimum allowable reactive power compensation deviation value, then the current reactive power compensation value is subtracted from the preset positive compensation amount to obtain the updated reactive power compensation value.

[0127] If the reactive power deviation value is between the preset maximum allowable reactive power compensation deviation value and the preset minimum allowable reactive power compensation deviation value, then the current reactive power compensation value remains unchanged.

[0128] This embodiment reduces ineffective actions by using a range threshold plus step adjustment method, while ensuring the stability of the adjustment by using a fixed step size.

[0129] The preset reactive power compensation allowable deviation threshold is set based on engineering considerations of measurement error tolerance and system inertia. Setting an interval threshold can filter errors caused by natural fluctuations and avoid frequent adjustments to the compensation value. Furthermore, this does not mean the interval must be symmetrical. In practical applications, asymmetrical intervals (e.g., -3kvar to +1kvar) can be set according to the grid's sensitivity to reactive power, but symmetrical intervals are easier to implement in engineering. The upper and lower limits of the interval (minimum and maximum allowable deviations) must match the unit's control accuracy.

[0130] This embodiment employs a stepped adjustment method of superimposing / subtracting preset positive compensation amounts, rather than continuous adjustment. When the deviation value exceeds the maximum allowable value, positive compensation is added to prevent continuous insufficient reactive power output from the unit; when the deviation value is less than the minimum allowable value, positive compensation is subtracted to suppress excessive reactive power output from the unit; when the deviation is within the range, it remains unchanged to prevent system oscillations caused by excessive intervention.

[0131] It is important to emphasize that the value of the preset positive compensation amount should take into account both adjustment speed and stability. Too large a step size may lead to overshoot, while too small a step size will result in low adjustment efficiency.

[0132] This embodiment filters out minor fluctuations by using interval thresholds, so that the compensation value is adjusted only when necessary (when the deviation is significant), avoiding the problem of fluctuations with noise in traditional continuous regulation; the step-type regulation matches the actual response capability of the converter, ensuring that the command can be executed accurately, while the fixed step size simplifies the control logic and reduces the computing burden on the unit's main control unit.

[0133] In a further specific embodiment, based on the comparison result between the updated reactive power compensation value and the preset reactive power compensation boundary threshold, it is determined whether the updated reactive power compensation value needs to be restricted and adjusted, including:

[0134] The preset reactive power compensation boundary threshold is the range between the preset upper limit value and the preset lower limit value of reactive power compensation;

[0135] If the updated reactive power compensation value is greater than the preset upper limit of reactive power compensation or less than the preset lower limit of reactive power compensation, then it is determined that the reactive power compensation value needs to be restricted and adjusted.

[0136] If the updated reactive power compensation value is between the preset lower limit and the preset upper limit of reactive power compensation, then it is determined that no limit adjustment is needed for the reactive power compensation value.

[0137] First, in this embodiment, the boundary threshold is defined as "the range between the preset upper limit and the preset lower limit of reactive power compensation," and the value must correspond to the reactive power output capability characteristics of the doubly-fed induction generator (DFIG) converter. The reactive power output of the converter has physical limits (limited by the power module capacity, heat dissipation capacity, etc.), and exceeding these limits will lead to faults such as overcurrent and overtemperature. Therefore, the safe output range must be defined by upper and lower limits.

[0138] Secondly, the upper and lower limits are not fixed, but are strongly related to the actual capacity of the converter. The specific values ​​need to be determined through the converter's factory testing. It is important to emphasize that the boundary thresholds are rigid limits, unlike the allowable deviation thresholds (flexible fluctuation ranges) mentioned earlier. Their purpose is to prevent equipment damage, not to optimize the regulation effect.

[0139] When the updated compensation value is greater than the upper limit or less than the lower limit, it indicates that the compensation value has exceeded the equipment's safe range and must be adjusted. Whether the exceedance is positive or negative, it is included in the adjustment scope to ensure no omissions. When the compensation value is "between the lower and upper limits," it indicates that the compensation value is within the equipment's safe range and can be directly output, avoiding unnecessary intervention and ensuring adjustment efficiency.

[0140] This embodiment serves as the final step in the compensation value determination process. Even if the preceding deviation calculation and step update are abnormal, the boundary threshold can still intercept the excessive compensation value, thus preventing the converter from being damaged due to overload.

[0141] Specifically, the updated reactive power compensation value will be subject to restrictions and adjustments, including:

[0142] If the updated reactive power compensation value is greater than the preset reactive power compensation upper limit, then the reactive power compensation value will be adjusted to the preset reactive power compensation upper limit.

[0143] If the updated reactive power compensation value is less than the preset lower limit of reactive power compensation, the reactive power compensation value will be adjusted to the preset lower limit of reactive power compensation.

[0144] The adjustment rules use direct replacement rather than proportional reduction to ensure that the final command is within the range that the converter can execute, thus avoiding invalid commands or equipment failures.

[0145] Although the adjusted compensation value may differ from the ideal compensation value, it will not affect the final effect of the closed-loop control. Based on the negative feedback principle of closed-loop control, if the error is calculated in the next cycle, the compensation value will continue to be increased, but since the boundary has been reached, the output will still be the boundary value to avoid equipment risk and maximize the utilization of the converter.

[0146] Figure 4 This is a topology diagram of an offshore wind power flexible DC system. After being controlled by this control method, the reactive power at the wind turbine outlets 501 and 502 can be reduced to 0. Therefore, the offshore converter station can be equipped with a small-capacity SVG to provide initial reactive power support and compensate for a small amount of losses in the collector lines and main transformer.

[0147] This invention achieves precise control of zero reactive power output from a single wind turbine in a flexible direct power transmission scenario by utilizing a single-unit autonomous reactive power closed-loop control function. This reduces the capacity of the SVG system in offshore converter stations and eliminates the need for a heavy single-unit reactive power control module in the energy management system, thereby lowering costs. It also enables rapid compensation of the turbine's own reactive power, meeting the grid's requirements for rapid reactive power support from wind turbines.

[0148] Figure 5The comparison diagram of reactive power command and wind turbine outlet reactive power curve provided in this application for a single-unit reactive power closed-loop control shows that when the reactive power command shows a step, the reactive power at the wind turbine outlet can be adjusted to the correct position within 1 second. Its control rate is much higher than the control requirement of no more than 30 seconds for reactive power steady-state control response time specified in the industry standard.

[0149] In the above embodiments, the reactive power closed-loop control method for a single unit of a medium-voltage doubly-fed induction generator (DFIG) wind turbine has been described in detail. This application also provides embodiments corresponding to the reactive power closed-loop control device for a single unit of a medium-voltage DFIG wind turbine. It should be noted that this application describes the embodiments of the device from two perspectives: one based on functional modules and the other based on hardware.

[0150] From the perspective of functional modules Figure 6 A structural diagram of a single-unit reactive power closed-loop control device for a medium-voltage doubly-fed wind turbine generator provided in this application embodiment is shown below. Figure 6 As shown, a single-unit reactive power closed-loop control device for a medium-voltage doubly-fed wind turbine includes:

[0151] The acquisition module 11 is used to acquire the real-time electrical parameters of the medium-voltage side and low-voltage side of the transformer of the doubly fed wind turbine generator set, as well as the inherent parameters of the transformer.

[0152] Calculation module 12 is used to obtain the real-time reactive power loss of the transformer and the reactive power of the doubly-fed wind turbine based on inherent parameters and real-time electrical parameters.

[0153] Correction module 13 is used to superimpose real-time reactive power loss onto the externally input initial reactive power command to obtain the corrected reactive power value;

[0154] Compensation module 14 determines the reactive power compensation value based on the unit's reactive power and the deviation of the corrected reactive power value;

[0155] Execution module 15 sends the result of the superposition of the corrected reactive power value and the reactive power compensation value as the final reactive power command to the converter of the doubly fed wind turbine.

[0156] Since the embodiments of the apparatus and the embodiments of the method correspond to each other, please refer to the description of the embodiments of the method for the embodiments of the apparatus, which will not be repeated here.

[0157] Figure 7 A structural diagram of another medium-voltage doubly-fed wind turbine single-unit reactive power closed-loop control device provided in this application embodiment is shown below. Figure 7 As shown, the single-unit reactive power closed-loop control device for medium-voltage doubly-fed wind turbine generators includes: a memory 20 for storing computer programs;

[0158] The processor 21 is used to execute computer programs to implement the steps of the method for obtaining user operation habit information as described in the above embodiment (Medium-voltage Doubly Fed Wind Turbine Unit Single Unit Reactive Power Closed-Loop Control Method).

[0159] The medium-voltage doubly-fed wind turbine generator single-unit reactive power closed-loop control device provided in this embodiment can include, but is not limited to, mobile terminals, personal computers, workstations, etc.

[0160] The processor 21 may include one or more processing cores, such as a quad-core processor or an octa-core processor. The processor 21 may be implemented using at least one of the following hardware forms: Digital Signal Processor (DSP), Field-Programmable Gate Array (FPGA), or Programmable Logic Array (PLA). The processor 21 may also include a main processor and a coprocessor. The main processor, also known as the Central Processing Unit (CPU), is used to process data in the wake-up state; the coprocessor is a low-power processor used to process data in the standby state. In some embodiments, the processor 21 may integrate a Graphics Processing Unit (GPU), which is responsible for rendering and drawing the content to be displayed on the screen. In some embodiments, the processor 21 may also include an Artificial Intelligence (AI) processor, which handles computational operations related to machine learning.

[0161] The memory 20 may include one or more computer-readable storage media, which may be non-transitory. The memory 20 may also include high-speed random access memory and non-volatile memory, such as one or more disk storage devices or flash memory devices. In this embodiment, the memory 20 is used to store at least the following computer program 201, which, after being loaded and executed by the processor 21, is capable of implementing the relevant steps of the single-unit reactive power closed-loop control method for medium-voltage doubly-fed wind turbines disclosed in any of the foregoing embodiments. In addition, the resources stored in the memory 20 may also include an operating system 202 and data 203, and the storage method may be temporary or permanent storage. The operating system 202 may include Windows, Unix, Linux, etc. The data 203 may include, but is not limited to, the data involved in implementing the single-unit reactive power closed-loop control method for medium-voltage doubly-fed wind turbines.

[0162] In some embodiments, the single-unit reactive power closed-loop control device for medium-voltage doubly-fed wind turbine generators may further include a display screen 22, an input / output interface 23, a communication interface 24, a power supply 25, and a communication bus 26.

[0163] Those skilled in the art will understand that Figure 7 The structure shown does not constitute a limitation on the single-unit reactive power closed-loop control device of a medium-voltage doubly fed wind turbine, and may include more or fewer components than shown.

[0164] The medium-voltage doubly-fed induction generator (DFIG) single-unit reactive power closed-loop control device provided in this application includes a memory and a processor. When the processor executes the program stored in the memory, it can implement the following method: medium-voltage DFIG single-unit reactive power closed-loop control method.

[0165] Finally, this application also provides an embodiment corresponding to a computer-readable storage medium. The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps described in the above embodiment of the single-unit reactive power closed-loop control method for medium-voltage doubly-fed wind turbine generators.

[0166] It is understood that if the methods in the above embodiments are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and executes all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0167] The computer-readable storage medium provided in this embodiment stores a computer program. When the processor executes the program, it can implement the following method: a closed-loop reactive power control method for a single unit of a medium-voltage doubly-fed wind turbine.

[0168] The foregoing provides a detailed description of the single-unit reactive power closed-loop control method, apparatus, and medium for medium-voltage doubly-fed wind turbine generators provided in this application. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

[0169] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A closed-loop reactive power control method for a single unit of a medium-voltage doubly-fed wind turbine generator set, characterized in that, include: Obtain the real-time electrical parameters of the medium-voltage side and low-voltage side of the transformer of the doubly fed wind turbine, as well as the inherent parameters of the transformer; The real-time reactive power loss of the transformer and the reactive power of the doubly-fed wind turbine are obtained based on the inherent parameters and the real-time electrical parameters. The real-time reactive power loss is superimposed on the externally input initial reactive power command to obtain the corrected reactive power value; The reactive power compensation value is determined based on the unit's reactive power and the deviation of the corrected reactive power value. The result of superimposing the corrected reactive power value and the reactive power compensation value is used as the final reactive power command and sent to the converter of the doubly fed wind turbine.

2. The single-unit reactive power closed-loop control method for medium-voltage doubly-fed wind turbine generators according to claim 1, characterized in that, The acquisition of real-time electrical parameters of the medium-voltage and low-voltage sides of the transformer of the doubly-fed wind turbine generator, and the inherent parameters of the transformer, includes: Collect real-time current, voltage, and reactive power values ​​on the medium-voltage side of the transformer; Collect real-time current, voltage, and reactive power values ​​on the low-voltage side of the transformer; Obtain the preset actual reactance value and no-load reactive power value of the transformer.

3. The single-unit reactive power closed-loop control method for medium-voltage doubly-fed wind turbine generators according to claim 2, characterized in that, The real-time reactive power loss of the transformer and the reactive power of the doubly-fed wind turbine are obtained based on the inherent parameters and the real-time electrical parameters, including: The real-time reactive power loss of the transformer is obtained based on the first formula, the actual reactance value of the transformer, the no-load reactive power value, and the real-time electrical parameters. First formula: ； In the formula, This refers to the real-time reactive power loss of the transformer. This represents the no-load reactive power value of the transformer. , , These represent the actual reactance values ​​of the low-voltage side, medium-voltage side, and high-voltage side of the transformer, respectively. , , These represent the real-time current values ​​on the low-voltage, medium-voltage, and high-voltage sides of the transformer, respectively; where, It is based on , Obtained; The reactive power of the unit is obtained by summing the reactive power on the medium-voltage side and the low-voltage side of the transformer.

4. The single-unit reactive power closed-loop control method for medium-voltage doubly-fed wind turbine generators according to claim 2, characterized in that, Determining the reactive power compensation value based on the deviation of the unit's reactive power and the corrected reactive power value includes: Every preset period, a reactive power deviation value is obtained based on the deviation between the unit's reactive power and the corrected reactive power value. Based on the comparison result between the reactive power deviation value and the preset reactive power compensation allowable deviation threshold, the current reactive power compensation value is updated. Based on the comparison between the updated reactive power compensation value and the preset reactive power compensation boundary threshold, it is determined whether the updated reactive power compensation value needs to be restricted and adjusted. If not, output the updated reactive power compensation value and proceed to the next step; If so, the updated reactive power compensation value will be adjusted, and the adjusted reactive power compensation value will be used to proceed to the next step.

5. The single-unit reactive power closed-loop control method for medium-voltage doubly-fed wind turbine generators according to claim 4, characterized in that, The step of updating the current reactive power compensation value based on the comparison result between the reactive power deviation value and the preset reactive power compensation allowable deviation threshold includes: The preset reactive power compensation allowable deviation threshold is the range from the minimum preset reactive power compensation allowable deviation to the maximum preset reactive power compensation allowable deviation. If the reactive power deviation value is greater than the preset maximum allowable reactive power compensation deviation value, then the current reactive power compensation value is superimposed with the preset positive compensation amount to obtain the updated reactive power compensation value. If the reactive power deviation value is less than the preset minimum allowable reactive power compensation deviation value, then the current reactive power compensation value is subtracted from the preset positive compensation amount to obtain the updated reactive power compensation value. If the reactive power deviation value is between the preset maximum allowable reactive power compensation deviation value and the preset minimum allowable reactive power compensation deviation value, then the current reactive power compensation value remains unchanged.

6. The single-unit reactive power closed-loop control method for medium-voltage doubly-fed wind turbine generators according to claim 4, characterized in that, Based on the comparison between the updated reactive power compensation value and the preset reactive power compensation boundary threshold, determine whether it is necessary to adjust the restrictions on the updated reactive power compensation value, including: The preset reactive power compensation boundary threshold is the range between the preset upper limit value and the preset lower limit value of reactive power compensation. If the updated reactive power compensation value is greater than the preset upper limit of reactive power compensation or less than the preset lower limit of reactive power compensation, then it is determined that the reactive power compensation value needs to be restricted and adjusted. If the updated reactive power compensation value is between the preset lower limit and the preset upper limit, then it is determined that no limit adjustment is needed for the reactive power compensation value.

7. The single-unit reactive power closed-loop control method for medium-voltage doubly-fed wind turbine generators according to claim 6, characterized in that, Adjustments were made to the limits of the updated reactive power compensation values, including: If the updated reactive power compensation value is greater than the preset reactive power compensation upper limit value, then the reactive power compensation value is adjusted to the preset reactive power compensation upper limit value. If the updated reactive power compensation value is less than the preset reactive power compensation lower limit, then the reactive power compensation value is adjusted to the preset reactive power compensation lower limit.

8. A closed-loop reactive power control device for a single unit of a medium-voltage doubly-fed wind turbine generator set, characterized in that, include: The acquisition module is used to acquire the real-time electrical parameters of the medium-voltage side and low-voltage side of the transformer of the doubly fed wind turbine generator set, as well as the inherent parameters of the transformer. The calculation module is used to obtain the real-time reactive power loss of the transformer and the unit reactive power of the doubly-fed wind turbine based on the inherent parameters and the real-time electrical parameters. The correction module is used to superimpose the real-time reactive power loss onto the externally input initial reactive power command to obtain the corrected reactive power value; The compensation module determines the reactive power compensation value based on the reactive power of the unit and the deviation of the corrected reactive power value. The execution module sends the superposition result of the corrected reactive power value and the reactive power compensation value as the final reactive power command to the converter of the doubly fed wind turbine.

9. A closed-loop reactive power control device for a single unit of a medium-voltage doubly-fed wind turbine generator set, characterized in that, include: Memory, used to store computer programs; A processor is configured to execute the computer program to implement the steps of the single-unit reactive power closed-loop control method for medium-voltage doubly-fed wind turbine generators as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the single-unit reactive power closed-loop control method for medium-voltage doubly-fed wind turbine generators as described in any one of claims 1 to 7.

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