Reactive power control method, device and storage medium for network-constructed doubly-fed wind turbine generator

Abstract

The application discloses a kind of reactive power control method, equipment and storage medium of network type doubly-fed wind turbine, belong to new energy grid-connected field, for in machine side converter controller and grid side converter controller respectively through reactive power output regulation grid point voltage, solved the response accuracy of wind farm reactive power control instruction is poor and the problem that the support ability of doubly-fed wind turbine for grid voltage is limited;When reactive power control instruction and the reactive power that machine side converter controller is used for voltage regulation is reversed, the reactive power that grid side converter controller outputs and the direction of reactive power control instruction is consistent, can offset circulating current in wind turbine, to improve the response accuracy of reactive power control instruction;And when reactive power control instruction and the reactive power that machine side converter controller is used for voltage regulation is in the same direction, the reactive power that grid side converter controller outputs can improve the support ability of doubly-fed wind turbine for grid voltage.

Description

Technical Field

[0001] This invention relates to the field of new energy grid connection, and in particular to a reactive power control method, equipment and storage medium for grid-connected doubly-fed wind turbine generators. Background Technology

[0002] For grid-connected doubly-fed induction generators (DFIGs), both their stator and rotor windings have energy interaction paths with the power grid. In this case, how to accurately respond to the reactive power control commands that the wind farm may send to the DFIGs and improve the DFIGs' ability to support the grid voltage is an urgent problem to be solved.

[0003] Therefore, how to provide a solution to the above-mentioned technical problems is a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a reactive power control method, device, and storage medium for grid-connected doubly-fed induction generator (DFIG) wind turbines. When the reactive power control command is in the opposite direction to the reactive power used for voltage regulation by the turbine-side converter, the reactive power output by the grid-side converter in the same direction as the reactive power control command can cancel the circulating current in the wind turbine, thereby improving the response accuracy of the reactive power control command. When the reactive power control command is in the same direction as the reactive power used for voltage regulation by the turbine-side converter, the reactive power output by the grid-side converter can improve the support capability of the DFIG wind turbine for grid voltage.

[0005] To address the aforementioned technical problems, this invention provides a reactive power control method for grid-connected doubly-fed induction generator (DFIG) wind turbines, applied to the grid-side converter controller of the DFIG wind turbine, comprising: If the sampled voltage value at the grid connection point deviates from the rated voltage value at the grid connection point, a first reactive power command is generated through a closed-loop control algorithm based on the deviation between the sampled voltage value at the grid connection point and the rated voltage value at the grid connection point; where the grid connection point is the connection point between the doubly fed wind turbine and the power grid. If the doubly fed wind turbine receives a reactive power control command from the wind farm, then the sign of the first reactive power command will be set to the sign of the reactive power control command. According to the first reactive power command, reactive power is output to the grid through the grid-side converter and grid connection point; The generator-side converter controller of the doubly fed wind turbine is used to: if the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage, generate a second reactive power command through a closed-loop control algorithm based on the deviation between the sampled value of the grid connection point voltage and the rated value of the grid connection point voltage; and output reactive power to the grid through the stator winding grid connection point according to the second reactive power command.

[0006] On the other hand, the step of setting the sign of the first reactive power command to the sign of the reactive power control command if the doubly-fed wind turbine currently receives a reactive power control command from the wind farm includes: If the doubly fed wind turbine receives a reactive power control command from the wind farm, then determine whether the sign of the reactive power control command is opposite to the sign of the first reactive power command. Conversely, it is determined whether the deviation between the sampled voltage value at the grid connection point and the rated voltage value at the grid connection point is greater than the preset deviation threshold. If the value is greater than the value, then the response to the reactive power control command is prohibited, and the step of outputting reactive power to the grid through the grid-side converter connection point according to the first reactive power command is executed. If it is not greater than, then the sign of the first reactive power command will be set to the sign of the reactive power control command.

[0007] On the other hand, if the doubly-fed induction generator (DFIG) currently receives a reactive power control command sent by the wind farm, after determining whether the positive or negative sign of the reactive power control command is opposite to the positive or negative sign of the first reactive power command, the reactive power control method for the grid-type DFIG wind turbine further includes: If not the opposite, then the sign of the first reactive power command is set to the sign of the reactive power control command.

[0008] On the other hand, the process of determining the preset deviation threshold includes: Based on the preset power factor operating range of the doubly fed wind turbine, the preset reactive current protection threshold, the first voltage regulation coefficient used in the closed-loop control algorithm, and the collector line impedance value between the turbine outlet and the wind farm grid connection point, the preset deviation threshold is determined through the preset first relationship.

[0009] On the other hand, the first relation includes: ; in, V 0 For preset deviation threshold, I 0 The reactive power circulating current protection threshold, K V The first voltage regulation coefficient, Z line The impedance value of the collector line, The power factor is the operating range.

[0010] On the other hand, if the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage, generating a first reactive power command through a closed-loop control algorithm based on the deviation between the sampled value and the rated value of the grid connection point voltage includes: If the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage, a first reactive power command is generated through a closed-loop control algorithm based on the deviation between the sampled value of the grid connection point voltage and the rated value of the grid connection point voltage and the first voltage regulation coefficient. The generator-side converter controller of the doubly fed wind turbine is specifically used for: if the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage, generating a second reactive power command through a closed-loop control algorithm based on the deviation between the sampled value of the grid connection point voltage and the rated value of the grid connection point voltage and the second voltage regulation coefficient; and outputting reactive power to the grid through the stator winding grid connection point according to the second reactive power command. If the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage, a second reactive power command is generated through a closed-loop control algorithm based on the deviation between the sampled value of the grid connection point voltage and the rated value of the grid connection point voltage. The first voltage regulation coefficient is equal to the second voltage regulation coefficient.

[0011] On the other hand, the reactive power control method for the grid-type doubly-fed wind turbine also includes: Real-time monitoring of power grid impedance indicators; When the grid impedance strength index is lower than the preset weak grid threshold, the weight of the first voltage regulation coefficient relative to the second voltage regulation coefficient is increased, and reactive power support is provided preferentially through the grid-side converter. When the grid impedance strength index is not lower than the preset weak grid threshold, the weight of the first voltage regulation coefficient relative to the second voltage regulation coefficient is reduced, and reactive power support is provided preferentially through the generator-side converter. Wherein, the first voltage regulation coefficient is the voltage regulation coefficient in the closed-loop control algorithm used by the grid-side converter controller to generate the first reactive power command, and the second voltage regulation coefficient is the voltage regulation coefficient in the closed-loop control algorithm used by the machine-side converter controller to generate the second reactive power command.

[0012] On the other hand, increasing the weight of the first voltage regulation coefficient relative to the second voltage regulation coefficient when the grid impedance index is lower than the preset weak grid threshold includes: When the grid impedance strength index is lower than the preset weak grid threshold, the first weight ratio corresponding to the deviation between the grid impedance strength index and the preset weak grid threshold is determined according to the first correspondence relationship, and the first voltage regulation coefficient and the second voltage regulation coefficient are determined according to the first weight ratio; wherein, in the first correspondence relationship, the deviation is positively correlated with the first weight ratio, and the first weight ratio is the ratio of the first voltage regulation coefficient to the second voltage regulation coefficient. When the grid impedance strength index is not lower than the preset weak grid threshold, reducing the weight of the first voltage regulation coefficient relative to the second voltage regulation coefficient includes: When the grid impedance strength index is not lower than the preset weak grid threshold, the second weight ratio corresponding to the deviation between the grid impedance strength index and the preset weak grid threshold is determined according to the second correspondence, and the first voltage regulation coefficient and the second voltage regulation coefficient are determined according to the second weight ratio; wherein, in the second correspondence, the deviation is negatively correlated with the second weight ratio, and the second weight ratio is the ratio of the first voltage regulation coefficient to the second voltage regulation coefficient.

[0013] To address the aforementioned technical problems, this invention also provides a reactive power control device for a grid-connected doubly-fed wind turbine generator, comprising: Memory, used to store computer programs; A processor is used to execute the computer program to implement the reactive power control method for the grid-type doubly fed wind turbine generator as described above.

[0014] To address the aforementioned technical problems, the present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the reactive power control method for grid-type doubly-fed wind turbine generators as described above.

[0015] Beneficial Effects: This invention provides a reactive power control method for grid-connected doubly-fed induction generator (DFIG) wind turbines. When the sampled voltage value at the grid connection point deviates from the rated voltage value, the grid-side converter controller generates a first reactive power command based on the deviation between the sampled voltage value and the rated voltage value using a closed-loop control algorithm. If the DFIG wind turbine currently receives a reactive power control command from the wind farm, the sign of the first reactive power command is set to the sign of the reactive power control command, and reactive power is output to the grid through the grid-side converter at the grid connection point according to the first reactive power command. The generator-side converter controller can also output reactive power for regulating the grid connection point voltage through the stator winding grid connection point. In this case, when the reactive power control command is in the opposite direction to the reactive power used by the generator-side converter controller for voltage regulation, the reactive power output by the grid-side converter controller in the same direction as the reactive power control command can cancel the circulating current in the wind turbine, thereby improving the response accuracy of the reactive power control command. When the reactive power control command is in the same direction as the reactive power used by the generator-side converter controller for voltage regulation, the reactive power output by the grid-side converter controller can improve the doubly-fed induction generator's ability to support the grid voltage.

[0016] The present invention also provides a reactive power control device and a computer-readable storage medium for a grid-type doubly-fed wind turbine generator set, which have the same beneficial effects as the reactive power control method for the grid-type doubly-fed wind turbine generator set described above. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the relevant technologies and the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the first process of the reactive power control method for grid-type doubly fed wind turbine generators provided by the present invention. Figure 2 A schematic diagram of the reactive power control system of the grid-type doubly fed wind turbine provided by the present invention; Figure 3 A schematic diagram of a reactive current circulation provided by the present invention; Figure 4 The reactive power path diagram for the first reactive power control condition of the grid-type doubly fed wind turbine provided by the present invention; Figure 5 The reactive power path diagram for the second reactive power control condition of the grid-type doubly fed wind turbine provided by the present invention; Figure 6 The reactive power path diagram for the third reactive power control condition of the grid-type doubly fed wind turbine provided by this invention; Figure 7 The reactive power path diagram for the fourth reactive power control condition of the grid-type doubly fed wind turbine provided by this invention; Figure 8 A schematic diagram of the reactive power control device for a grid-type doubly fed wind turbine provided by the present invention. Detailed Implementation

[0019] The core of this invention is to provide a reactive power control method, device, and storage medium for grid-connected doubly-fed induction generator (DFIG) wind turbines. When the reactive power control command is in the opposite direction to the reactive power used for voltage regulation by the turbine-side converter, the reactive power output by the grid-side converter in the same direction as the reactive power control command can cancel the circulating current in the wind turbine, thereby improving the response accuracy of the reactive power control command. When the reactive power control command is in the same direction as the reactive power used for voltage regulation by the turbine-side converter, the reactive power output by the grid-side converter can improve the DFIG wind turbine's ability to support grid voltage.

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please refer to Figure 1 , Figure 1 This is a first flowchart illustrating the reactive power control method for a grid-connected doubly-fed induction generator (DFIG) wind turbine provided by the present invention. The reactive power control method for this grid-connected DFIG wind turbine is applied to the grid-side converter controller of the DFIG wind turbine and includes: S101: If the sampled voltage value at the grid connection point deviates from the rated voltage value at the grid connection point, a first reactive power command is generated through a closed-loop control algorithm based on the deviation between the sampled voltage value at the grid connection point and the rated voltage value at the grid connection point; where the grid connection point is the connection point between the doubly fed wind turbine and the power grid. Specifically, considering the technical problems mentioned in the background above, and taking into account that: when the reactive power control command issued by the wind farm is in the opposite direction to the second reactive power command used by the turbine-side converter for voltage regulation, the first reactive power command output by the grid-side converter in the same direction as the reactive power control command can cancel the circulating current in the wind turbine, thereby improving the response accuracy of the reactive power control command; while when the reactive power control command and the second reactive power command used by the turbine-side converter for voltage regulation are in the same direction, the first reactive power command output by the grid-side converter can improve the support capability of the doubly-fed induction generator (DFIG) wind turbine for grid voltage; therefore, in this embodiment of the invention, while the turbine-side converter regulates the grid connection point voltage through reactive power, the grid-side converter also regulates the grid connection point voltage through reactive power, and controls the first reactive power command of the grid-side converter to be in the same direction as the reactive power control command, thereby not only improving the response accuracy of the reactive power control command, but also improving the support capability of the DFIG wind turbine for grid voltage.

[0022] Specifically, based on the above concept, the grid-side converter controller in this step can generate a first reactive power command through a closed-loop control algorithm when the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage. This command is then used as the data basis for subsequent steps, thereby realizing the regulation of the grid connection point voltage on the grid side.

[0023] It is worth mentioning that for doubly-fed wind turbines, the stator winding and rotor winding are connected to the power grid through wind turbine transformers. If the voltage levels of the stator winding and rotor winding sides are the same, the stator winding and rotor winding sides and the wind turbine transformer can use the same connection point, and this connection point is used as the grid connection point. If there is a deviation in the voltage levels of the stator winding and rotor winding sides (if there is, it is a slight deviation), the stator winding and rotor winding sides and the wind turbine transformer can use different connection points, and these two different connection points are used as grid connection points respectively.

[0024] S102: If the doubly fed wind turbine receives a reactive power control command from the wind farm, then set the sign of the first reactive power command to the sign of the reactive power control command. Specifically, considering that reactive power circulation is based on the opposite signs of the reactive power control command and the second reactive power command from the turbine-side converter, if the first and second reactive power commands can be controlled to have the same sign as the reactive power control command, then it means that when the reactive power control command and the second reactive power command from the turbine-side converter have opposite signs, the first and second reactive power commands will also have opposite signs. In this case, within the wind turbine, the reactive power generated by the first reactive power command can cancel out the reactive power generated by the second reactive power command. That is, the reactive power generated by the first reactive power command satisfies the second reactive power command, thereby reducing the cancellation effect of the second reactive power command on the reactive power control command and improving the response accuracy of the reactive power control command. Furthermore, if the reactive power control command and the second reactive power command from the turbine-side converter have the same sign, and if the first reactive power command and the reactive power control command also have the same sign, then internal circulation will not occur in this case. Therefore, the first reactive power command improves the doubly-fed induction generator's ability to support grid voltage.

[0025] Therefore, based on the above considerations, in this step, when the doubly fed wind turbine receives the reactive power control command from the wind farm, the positive and negative signs of the first reactive power command can be set to the positive and negative signs of the reactive power control command, thereby satisfying the above two advantages.

[0026] S103: According to the first reactive power command, output reactive power to the grid through the grid-side converter connection point; The generator-side converter controller of the doubly fed wind turbine is used to: if the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage, generate a second reactive power command through a closed-loop control algorithm based on the deviation between the sampled value of the grid connection point voltage and the rated value of the grid connection point voltage; and output reactive power to the grid through the stator winding grid connection point according to the second reactive power command.

[0027] Specifically, after obtaining the first reactive power command through S102, reactive power can be output to the grid through the grid-side converter and grid connection point according to the first reactive power command, which realizes the reactive power control of the grid-side converter controller and achieves the two advantages discussed above.

[0028] Specifically, for a better explanation of the embodiments of the present invention, please refer to... Figures 2 to 7 , Figure 2 A schematic diagram of the reactive power control system of the grid-type doubly fed wind turbine provided by the present invention; Figure 3 A schematic diagram of a reactive current circulation provided by the present invention; Figure 4 The reactive power path diagram for the first reactive power control condition of the grid-type doubly fed wind turbine provided by the present invention; Figure 5 The reactive power path diagram for the second reactive power control condition of the grid-type doubly fed wind turbine provided by the present invention; Figure 6The reactive power path diagram for the third reactive power control condition of the grid-type doubly fed wind turbine provided by this invention; Figure 7 The reactive power path diagram for the fourth reactive power control condition of the grid-type doubly fed wind turbine provided by this invention.

[0029] in, Figure 2 The stator winding of the doubly-fed generator set is connected to the grid via a wind turbine transformer, and the rotor winding is connected to the grid via a generator-side converter, a grid-side converter, and a wind turbine transformer. The generator-side converter is connected to the DC side of the grid-side converter, and the generator-side converter is connected to a generator-side converter controller. The grid-side converter is also connected to a grid-side converter controller. The generator-side converter controller can operate based on the rated voltage at the grid connection point. V ref With grid connection point voltage sampling value V 1 Closed-loop control of the grid connection point voltage is achieved through reactive power control; the grid-side converter controller can be based on the rated value of the grid connection point voltage. V ref With grid connection point voltage sampling value V 1 Closed-loop control of the grid connection point voltage is achieved through reactive power control, and the voltage is controlled according to the reactive power control commands issued by the wind farm. Perform reactive power control. Figure 3 This presents a working condition where reactive power circulation occurs within the wind turbine, assuming the grid connection voltage is [not specified]. V At rated values, the wind turbine receives reactive power control commands from the wind farm or power factor commands used to generate these commands. The grid-side converter controller then responds to these commands by outputting reactive power to the grid. Q This causes current to flow through the line impedance between the wind turbine and the power grid. I Increase, grid connection point voltage V The reactive power will increase, and because the generator-side converter control will adjust the reactive power according to the voltage deviation at the grid connection point, V An increase in power will cause the generator-side converter controller to control the stator of the doubly-fed generator to absorb reactive power, thereby generating... Figure 3 The two reactive power loops shown have a portion of the reactive power output from the grid-side converter passing through the wind turbine transformer to the stator side of the doubly-fed generator, and then returning to the turbine-side converter through the rotor winding of the doubly-fed generator. This constitutes a reactive power circulation within the wind turbine unit.

[0030] Specifically, Figure 4 In the operating condition shown, when the reactive power control command is positive, meaning the wind farm has a reactive power output demand, and the grid connection point voltage is normal, the grid connection point voltage will be raised due to the reactive power control command response of the wind turbine (i.e., V(Greater than the normal multiplier by 1). At this time, the grid-side converter outputs reactive power according to the reactive power control command of the wind farm. Due to the rise in the grid connection point voltage, the generator-side converter controller and the grid-side converter controller simultaneously perform reactive power control according to the deviation of the grid connection point voltage. Since the reactive power control command is positive, the reactive power adjustment amount of the first reactive power command of the generator-side converter controller and the second reactive power command generated by the grid-side converter controller are opposite in sign, forming a reactive power circulation inside the wind turbine, which cancels each other out. The overall reactive power output of the wind turbine accurately responds to the reactive power value calculated by the reactive power control command of the wind farm.

[0031] Specifically, Figure 5 In the operating condition shown, when the reactive power control command is positive, meaning the wind farm has a reactive power output demand, and the grid connection point voltage... V When the voltage is lower than the normal multiplier of 1, the grid-side converter outputs reactive power according to the reactive power control command of the wind farm. Due to the reduction in the grid connection point voltage, the generator-side converter controller and the grid-side converter controller simultaneously perform reactive power control based on the deviation of the grid connection point voltage. Since the reactive power control command is positive, the reactive power adjustment amount of the first reactive power command of the generator-side converter controller and the second reactive power command generated by the grid-side converter controller have the same sign. In addition to the reactive power value calculated by the wind turbine in response to the reactive power control command of the wind farm, two additional reactive power adjustment amounts are contributed, which can improve the grid-connected doubly-fed induction generator's ability to support the grid voltage.

[0032] Specifically, Figure 6 In the operating condition shown, when the reactive power control command is negative, meaning the wind farm has a reactive power absorption demand, and the grid connection point voltage... V When the voltage is higher than the normal multiplier by 1, the grid-side converter absorbs reactive power according to the reactive power control command of the wind farm. Due to the high level of the grid connection point voltage, the generator-side converter controller and the grid-side converter controller simultaneously perform reactive power control based on the deviation of the grid connection point voltage. Since the reactive power control command is negative, the reactive power adjustment amount of the first reactive power command of the generator-side converter controller and the second reactive power command generated by the grid-side converter controller have the same sign. In addition to the reactive power value calculated by the wind turbine in response to the reactive power control command of the wind farm, two additional reactive power adjustment amounts are contributed, which can improve the grid-type doubly-fed induction generator's ability to support the grid voltage.

[0033] Specifically, Figure 7 In the operating condition shown, when the reactive power control command is negative, meaning the wind farm has a reactive power absorption demand, and the grid connection point voltage is normal, the grid connection point voltage will be reduced due to the reactive power control command response of the wind turbine (i.e., V(Less than the normal multiplier by 1). At this time, the grid-side converter outputs reactive power according to the reactive power control command of the wind farm. Due to the reduction of the grid connection point voltage, the generator-side converter controller and the grid-side converter controller simultaneously perform reactive power control according to the deviation of the grid connection point voltage. Since the reactive power control command is negative, the reactive power adjustment amount of the first reactive power command of the generator-side converter controller and the second reactive power command generated by the grid-side converter controller are opposite in sign, forming a reactive power circulation inside the wind turbine, which cancels each other out. The wind turbine absorbs reactive power as a whole, thus accurately responding to the reactive power value calculated by the reactive power control command of the wind farm.

[0034] This invention provides a reactive power control method for grid-connected doubly-fed induction generator (DFIG) wind turbines. When the sampled voltage value at the grid connection point deviates from the rated grid connection voltage, the grid-side converter controller generates a first reactive power command based on the deviation between the sampled voltage value and the rated grid connection voltage using a closed-loop control algorithm. If the DFIG wind turbine currently receives a reactive power control command from the wind farm, the sign of the first reactive power command is set to the sign of the reactive power control command, and reactive power is output to the grid through the grid-side converter at the grid connection point according to the first reactive power command. Furthermore, the turbine-side converter... The current controller can also output reactive power to regulate the grid connection point voltage through the stator winding grid connection point. In this case, when the reactive power control command is in the opposite direction to the reactive power used for voltage regulation by the turbine-side converter controller, the reactive power output by the grid-side converter controller in the same direction as the reactive power control command can cancel the circulating current in the wind turbine, thereby improving the response accuracy of the reactive power control command. When the reactive power control command is in the same direction as the reactive power used for voltage regulation by the turbine-side converter controller, the reactive power output by the grid-side converter controller can improve the doubly-fed induction generator's ability to support the grid voltage.

[0035] As an optional embodiment, if the doubly-fed induction generator (DFIG) currently receives a reactive power control command from the wind farm, setting the sign of the first reactive power command to the sign of the reactive power control command includes: If the doubly fed wind turbine receives a reactive power control command from the wind farm, then determine whether the sign of the reactive power control command is opposite to the sign of the first reactive power command. Conversely, it is determined whether the deviation between the sampled voltage value at the grid connection point and the rated voltage value at the grid connection point is greater than the preset deviation threshold. If it is greater than the value, then the response to the reactive power control command is prohibited, and the step of outputting reactive power to the grid through the grid-side converter connection point according to the first reactive power command is executed. If it is not greater than, then the sign of the first reactive power command will be set to the sign of the reactive power control command.

[0036] Specifically, based on the above discussion, the generation of reactive power circulating current within a wind turbine is based on the opposite signs of the reactive power control command and the second reactive power command. However, in this case, if the voltage deviation at the grid connection point is too large, it may lead to excessive reactive power circulating current within the wind turbine, threatening the safe operation of the equipment. In this embodiment of the invention, by setting a preset deviation threshold, when the voltage deviation at the grid connection point exceeds the preset deviation threshold, the response to the reactive power control command is prohibited, and it is not necessary to set the first reactive power command and the reactive power control command to the same sign. This prioritizes voltage stability, avoids the problem of excessive reactive power circulating current within the unit caused by forced response to reactive power commands, ensures the safe and stable operation of the grid-connected doubly-fed induction generator (DFIG) wind turbine, and can still accurately respond to the reactive power control commands of the wind farm when the voltage deviation is small.

[0037] As an optional embodiment, if the doubly-fed induction generator (DFIG) currently receives a reactive power control command sent by the wind farm, after determining whether the positive or negative sign of the reactive power control command is opposite to the positive or negative sign of the first reactive power command, the reactive power control method for the grid-connected DFIG wind turbine further includes: If not the opposite, then the sign of the first reactive power command is set to the sign of the reactive power control command.

[0038] Specifically, considering that even if the voltage deviation at the grid connection point is too large, reactive circulating current will not be generated inside the wind turbine unit when the positive and negative signs of the reactive power control command and the first reactive power command are not opposite, in this embodiment of the invention, the step of setting the positive and negative signs of the first reactive power command to the positive and negative signs of the reactive power control command can continue to be executed in this case, thereby realizing the logic in the aforementioned operating conditions.

[0039] As an optional embodiment, the process of determining the preset deviation threshold includes: Based on the preset power factor operating range of the doubly fed wind turbine, the preset reactive current protection threshold, the first voltage regulation coefficient used in the closed-loop control algorithm, and the collector line impedance value between the turbine outlet and the wind farm grid connection point, the preset deviation threshold is determined through the preset first relationship.

[0040] Specifically, the setting of the preset deviation threshold comprehensively considers the unit's safe operation limitations and control performance requirements, making it more accurate than simply using a fixed value. Therefore, in this embodiment of the invention, the preset deviation threshold is determined through a preset first relationship based on the preset power factor operating range of the doubly-fed induction generator (DFIG) wind turbine, the preset reactive power circulating current protection threshold, the first voltage regulation coefficient used in the closed-loop control algorithm, and the collector line impedance value between the turbine terminal outlet and the wind farm grid connection point. This ensures that the preset deviation threshold setting closely matches the actual operating characteristics of the unit, maximizing the reactive power command response capability while ensuring safety, and avoiding the control performance degradation caused by conservative settings or the safety risks caused by aggressive settings.

[0041] Of course, in addition to this specific form, the preset deviation threshold can be set in many other ways, and this embodiment of the invention does not limit it here.

[0042] As an optional embodiment, the first relation includes: ; in, V 0 For preset deviation threshold, I 0 For reactive power circulating current protection threshold, K V Z is the first voltage regulation coefficient. line For the impedance value of the collector line, This refers to the operating range of the power factor.

[0043] Among them, the power factor command can be further obtained as a reactive power control command. The power factor operating range refers to the limited range of the power factor command, which is usually ±0.9. The reactive power circulating current protection threshold is generally taken as 12% to 15% of the rated current. The value range of the first voltage regulation coefficient can be 0 to 10. All parameters in the first relation can be normalized before participating in the calculation.

[0044] Specifically, the first relational expression in the embodiments of the present invention can make the determined preset deviation threshold more reasonable, further improving the matching degree between the preset deviation threshold and the actual operating characteristics of the unit.

[0045] Of course, besides this specific form, the first relation can also be in other forms, and the embodiments of the present invention are not limited here.

[0046] As an optional embodiment, if the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage, the first reactive power command is generated through a closed-loop control algorithm based on the deviation between the sampled value and the rated value of the grid connection point voltage, including: If the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage, a first reactive power command is generated through a closed-loop control algorithm based on the deviation between the sampled value of the grid connection point voltage and the rated value of the grid connection point voltage and the first voltage regulation coefficient. The generator-side converter controller of the doubly-fed induction generator (DFIG) is specifically used for: if the sampled voltage value at the grid connection point deviates from the rated voltage value at the grid connection point, generating a second reactive power command through a closed-loop control algorithm based on the deviation between the sampled voltage value at the grid connection point and the rated voltage value at the grid connection point and the second voltage regulation coefficient; and outputting reactive power to the grid through the stator winding grid connection point according to the second reactive power command. If the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage, a second reactive power command is generated through a closed-loop control algorithm based on the deviation between the sampled value of the grid connection point voltage and the rated value of the grid connection point voltage. The first voltage regulation coefficient is equal to the second voltage regulation coefficient.

[0047] Specifically, considering that if the first voltage regulation coefficient is equal to the second voltage regulation coefficient, then when the reactive power control command and the first reactive power command have opposite signs, the reactive power adjustment amount generated by the first reactive power command can completely cancel the reactive power adjustment amount generated by the second reactive power command, so that the response of the reactive power control command fully meets the reactive power demand of the wind farm, the first voltage regulation coefficient and the second voltage regulation coefficient are set to be equal in this embodiment of the invention.

[0048] As an optional embodiment, the reactive power control method for grid-connected doubly-fed wind turbine generators also includes: Real-time monitoring of power grid impedance indicators; When the grid impedance strength index is lower than the preset weak grid threshold, the weight of the first voltage regulation coefficient relative to the second voltage regulation coefficient is increased, and reactive power support is provided preferentially through the grid-side converter. When the grid impedance strength index is not lower than the preset weak grid threshold, the weight of the first voltage regulation coefficient relative to the second voltage regulation coefficient is reduced, and reactive power support is provided preferentially through the generator-side converter. Wherein, the first voltage regulation coefficient is the voltage regulation coefficient in the closed-loop control algorithm used by the grid-side converter controller to generate the first reactive power command, and the second voltage regulation coefficient is the voltage regulation coefficient in the closed-loop control algorithm used by the machine-side converter controller to generate the second reactive power command.

[0049] Specifically, in this embodiment of the invention, a grid impedance index is introduced as a dynamic adjustment parameter to realize the optimal reactive power allocation strategy under different grid conditions. Under weak grid conditions, that is, when the grid impedance index is lower than the preset weak grid threshold, the grid-side converter with faster response is given priority to provide voltage support. Under strong grid conditions, that is, when the grid impedance index is not lower than the preset weak grid threshold, the reactive power capacity of the generator-side converter is utilized more, thereby improving the overall system stability and efficiency.

[0050] Among them, the grid impedance strength index is a key parameter for measuring the strength of the grid. It can be represented by the short-circuit ratio (SCR) or the impedance ratio (Z). The short-circuit ratio is the ratio of the grid short-circuit capacity to the rated capacity of the wind farm. The grid impedance strength index is inversely proportional to the short-circuit ratio, that is, the smaller the short-circuit ratio, the larger the grid impedance strength index.

[0051] As an optional embodiment, when the grid impedance index is lower than a preset weak grid threshold, increasing the weight of the first voltage regulation coefficient relative to the second voltage regulation coefficient includes: When the grid impedance strength index is lower than the preset weak grid threshold, the first weight ratio corresponding to the deviation between the grid impedance strength index and the preset weak grid threshold is determined according to the first correspondence relationship, and the first voltage regulation coefficient and the second voltage regulation coefficient are determined according to the first weight ratio; wherein, in the first correspondence relationship, the deviation is positively correlated with the first weight ratio, and the first weight ratio is the ratio of the first voltage regulation coefficient to the second voltage regulation coefficient. When the grid impedance strength index is not lower than the preset weak grid threshold, reducing the weight of the first voltage regulation coefficient relative to the second voltage regulation coefficient includes: When the grid impedance strength index is not lower than the preset weak grid threshold, the second weight ratio corresponding to the deviation between the grid impedance strength index and the preset weak grid threshold is determined according to the second correspondence, and the first voltage regulation coefficient and the second voltage regulation coefficient are determined according to the second weight ratio; wherein, in the second correspondence, the deviation is negatively correlated with the second weight ratio, and the second weight ratio is the ratio of the first voltage regulation coefficient to the second voltage regulation coefficient.

[0052] Specifically, considering that the grid impedance is a continuously changing quantity, determining the weighting ratio by the deviation between the grid impedance index and the preset weak grid threshold yields a more accurate weighting ratio. Therefore, in this embodiment of the invention, when the grid impedance index is lower than the preset weak grid threshold, a first weighting ratio corresponding to the deviation between the grid impedance index and the preset weak grid threshold is determined according to a first correspondence; when the grid impedance index is not lower than the preset weak grid threshold, a second weighting ratio corresponding to the deviation between the grid impedance index and the preset weak grid threshold is determined according to a second correspondence. This efficiently and accurately determines the ratio of the first voltage regulation coefficient to the second voltage regulation coefficient.

[0053] Of course, besides this specific form, there are many other ways to adjust the ratio of the first voltage regulation coefficient to the second voltage regulation coefficient, and this embodiment of the invention does not limit them here.

[0054] Please refer to Figure 8 , Figure 8 A schematic diagram of the reactive power control device for a grid-type doubly-fed wind turbine provided by the present invention includes: Memory 81 is used to store computer programs; The processor 82 is used to execute computer programs to implement the reactive power control method for grid-type doubly fed wind turbine generators as described in the foregoing embodiments.

[0055] For an introduction to the reactive power control equipment of the grid-type doubly-fed wind turbine provided in the embodiments of the present invention, please refer to the aforementioned embodiments of the reactive power control method for the grid-type doubly-fed wind turbine. The embodiments of the present invention will not be repeated here.

[0056] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the reactive power control method for a grid-type doubly fed wind turbine generator as described in the foregoing embodiments.

[0057] For a description of the computer-readable storage medium provided in the embodiments of the present invention, please refer to the aforementioned embodiments of the reactive power control method for grid-type doubly fed wind turbine generators. The embodiments of the present invention will not be repeated here.

[0058] The various embodiments described in this specification are presented 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. 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 a..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0059] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of reactive power control for a grid forming doubly-fed wind turbine, characterized in that, A grid-side converter controller for doubly-fed wind turbines includes: If the sampled voltage value at the grid connection point deviates from the rated voltage value at the grid connection point, a first reactive power command is generated through a closed-loop control algorithm based on the deviation between the sampled voltage value at the grid connection point and the rated voltage value at the grid connection point; where the grid connection point is the connection point between the doubly fed wind turbine and the power grid. If the doubly fed wind turbine receives a reactive power control command from the wind farm, then the sign of the first reactive power command will be set to the sign of the reactive power control command. According to the first reactive power command, reactive power is output to the grid through the grid-side converter and grid connection point; The generator-side converter controller of the doubly fed wind turbine is used to: if the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage, generate a second reactive power command through a closed-loop control algorithm based on the deviation between the sampled value of the grid connection point voltage and the rated value of the grid connection point voltage; and output reactive power to the grid through the stator winding grid connection point according to the second reactive power command.

2. The method for reactive power control of network configured doubly-fed wind turbine generator according to claim 1, characterized in that, If the doubly-fed induction generator (DFIG) currently receives a reactive power control command from the wind farm, then setting the sign of the first reactive power command to the sign of the reactive power control command includes: If the doubly fed wind turbine receives a reactive power control command from the wind farm, then determine whether the sign of the reactive power control command is opposite to the sign of the first reactive power command. Conversely, it is determined whether the deviation between the sampled voltage value at the grid connection point and the rated voltage value at the grid connection point is greater than the preset deviation threshold. If the value is greater than the value, then the response to the reactive power control command is prohibited, and the step of outputting reactive power to the grid through the grid-side converter connection point according to the first reactive power command is executed. If it is not greater than, then the sign of the first reactive power command will be set to the sign of the reactive power control command.

3. The reactive power control method for grid-type doubly-fed wind turbine generators according to claim 2, characterized in that, If the doubly-fed induction generator (DFIG) currently receives a reactive power control command from the wind farm, after determining whether the positive or negative sign of the reactive power control command is opposite to that of the first reactive power command, the reactive power control method for the grid-connected DFIG wind turbine further includes: If not the opposite, then the sign of the first reactive power command is set to the sign of the reactive power control command.

4. The reactive power control method for a grid-type doubly-fed wind turbine generator according to claim 2, characterized in that, The process of determining the preset deviation threshold includes: Based on the preset power factor operating range of the doubly fed wind turbine, the preset reactive current protection threshold, the first voltage regulation coefficient used in the closed-loop control algorithm, and the collector line impedance value between the turbine outlet and the wind farm grid connection point, the preset deviation threshold is determined through the preset first relationship.

5. The reactive power control method for a grid-type doubly-fed wind turbine generator according to claim 4, characterized in that, The first relation includes: ； in, V 0 For preset deviation threshold, I 0 The reactive power circulating current protection threshold, K V The first voltage regulation coefficient, Z line The impedance value of the collector line, The power factor is the operating range.

6. The reactive power control method for a grid-type doubly-fed wind turbine generator according to claim 1, characterized in that, If the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage, the first reactive power command is generated through a closed-loop control algorithm based on the deviation between the sampled value and the rated value of the grid connection point voltage, including: If the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage, a first reactive power command is generated through a closed-loop control algorithm based on the deviation between the sampled value of the grid connection point voltage and the rated value of the grid connection point voltage and the first voltage regulation coefficient. The generator-side converter controller of the doubly fed wind turbine is specifically used for: if the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage, generating a second reactive power command through a closed-loop control algorithm based on the deviation between the sampled value of the grid connection point voltage and the rated value of the grid connection point voltage and the second voltage regulation coefficient; and outputting reactive power to the grid through the stator winding grid connection point according to the second reactive power command. If the sampled value of the grid connection point voltage deviates from the rated value of the grid connection point voltage, a second reactive power command is generated through a closed-loop control algorithm based on the deviation between the sampled value of the grid connection point voltage and the rated value of the grid connection point voltage. The first voltage regulation coefficient is equal to the second voltage regulation coefficient.

7. The reactive power control method for a grid-type doubly-fed wind turbine generator according to any one of claims 1 to 5, characterized in that, The reactive power control method for grid-type doubly fed wind turbine generators also includes: Real-time monitoring of power grid impedance indicators; When the grid impedance strength index is lower than the preset weak grid threshold, the weight of the first voltage regulation coefficient relative to the second voltage regulation coefficient is increased, and reactive power support is provided preferentially through the grid-side converter. When the grid impedance strength index is not lower than the preset weak grid threshold, the weight of the first voltage regulation coefficient relative to the second voltage regulation coefficient is reduced, and reactive power support is provided preferentially through the generator-side converter. Wherein, the first voltage regulation coefficient is the voltage regulation coefficient in the closed-loop control algorithm used by the grid-side converter controller to generate the first reactive power command, and the second voltage regulation coefficient is the voltage regulation coefficient in the closed-loop control algorithm used by the machine-side converter controller to generate the second reactive power command.

8. The reactive power control method for a grid-type doubly-fed wind turbine generator according to claim 7, characterized in that, When the grid impedance index is lower than a preset weak grid threshold, increasing the weight of the first voltage regulation coefficient relative to the second voltage regulation coefficient includes: When the grid impedance strength index is lower than the preset weak grid threshold, the first weight ratio corresponding to the deviation between the grid impedance strength index and the preset weak grid threshold is determined according to the first correspondence relationship, and the first voltage regulation coefficient and the second voltage regulation coefficient are determined according to the first weight ratio; wherein, in the first correspondence relationship, the deviation is positively correlated with the first weight ratio, and the first weight ratio is the ratio of the first voltage regulation coefficient to the second voltage regulation coefficient. When the grid impedance strength index is not lower than the preset weak grid threshold, reducing the weight of the first voltage regulation coefficient relative to the second voltage regulation coefficient includes: When the grid impedance strength index is not lower than the preset weak grid threshold, the second weight ratio corresponding to the deviation between the grid impedance strength index and the preset weak grid threshold is determined according to the second correspondence, and the first voltage regulation coefficient and the second voltage regulation coefficient are determined according to the second weight ratio; wherein, in the second correspondence, the deviation is negatively correlated with the second weight ratio, and the second weight ratio is the ratio of the first voltage regulation coefficient to the second voltage regulation coefficient.

9. A reactive power control device for a grid-connected doubly-fed wind turbine generator, characterized in that, include: Memory, used to store computer programs; A processor, configured to execute the computer program to implement the steps of the reactive power control method for a grid-type doubly fed wind turbine generator as described in any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the reactive power control method for a grid-type doubly-fed wind turbine generator as described in any one of claims 1 to 8.

Images