Method and apparatus for controlling reactive power

Abstract

This application provides a method and apparatus for controlling reactive power; the method includes: determining the basic reactive power based on the line parameters of the transmission line; the basic reactive power characterizes the reactive power currently available on the transmission line; the transmission line is a doubly-fed generator line transmitting power to the grid; determining the input active power and input reactive power of the grid-side converter based on the operating parameters of the doubly-fed generator; determining a compensation value for the basic reactive power based on the input reactive power and input active power; compensating the basic reactive power based on the compensation value to obtain the compensated reactive power; and controlling the reactive power output of the transmission line based on the compensated reactive power.

Description

Technical Field

[0001] This application relates to power generation technology, and more particularly to a method and apparatus for controlling reactive power. Background Technology

[0002] Doubly fed generators exchange power with the grid through the stator, rotor, and AC excitation system. When the rotor outputs power to the grid, the proportion of reactive power and active power in the output power can be controlled by the grid-side converter, thereby controlling the reactive power of the transmission line.

[0003] Doubly fed generators are mainly used in doubly fed variable speed pumped storage units. However, there is little research on how to perform reactive power compensation and control in doubly fed variable speed pumped storage units. Summary of the Invention

[0004] This application provides a method and apparatus for controlling reactive power, and provides a scheme for reactive power compensation and control for doubly-fed variable speed pumped storage units.

[0005] The technical solution of this application embodiment is implemented as follows: This application provides a reactive power control method, which includes: determining a base reactive power based on the line parameters of a transmission line; the base reactive power characterizes the reactive power currently available on the transmission line; the transmission line is a doubly-fed generator line transmitting power to the grid; determining the input active power and input reactive power of the grid-side converter based on the operating parameters of the doubly-fed generator; determining a compensation value for the base reactive power based on the input reactive power and input active power; compensating the base reactive power based on the compensation value to obtain the compensated reactive power; and controlling the reactive power output by the transmission line based on the compensated reactive power.

[0006] This application provides a reactive power control device, comprising: a first determining unit for determining a base reactive power based on line parameters of a transmission line; the base reactive power characterizes the reactive power currently available on the transmission line; a second determining unit for determining the input active power and input reactive power of the grid-side converter based on the operating parameters of a doubly-fed generator; a third determining unit for determining a compensation value for the base reactive power based on the input reactive power and the input active power; a compensation unit for compensating the base reactive power based on the compensation value to obtain the compensated reactive power; and a control unit for controlling the transmission line based on the compensated reactive power.

[0007] This application provides an electronic device, which includes: a memory for storing computer-executable instructions or computer programs; and a processor for executing the computer-executable instructions or computer programs stored in the memory to implement the reactive power control method provided in this application.

[0008] This application provides a computer-readable storage medium storing a computer program or computer-executable instructions for implementing the reactive power control method provided in this application when executed by a processor.

[0009] This application provides a computer program product, including a computer program or computer-executable instructions. When the computer program or computer-executable instructions are executed by a processor, they implement the reactive power control method provided in this application.

[0010] The embodiments of this application have the following beneficial effects: First, the basic reactive power is determined based on the transmission line parameters, thus clarifying the reactive power available in the current transmission line and avoiding excessively high or low voltage caused by blind compensation, thereby improving the voltage stability of the transmission line. Second, the active and reactive power input to the grid-side converter are calculated based on the operating parameters of the doubly-fed generator (DFIG). Compensation values ​​are then determined based on these values. On the one hand, this allows for the exploration of the potential reactive power output of the grid-side converter; on the other hand, the reactive power compensation is matched with the operating state of the DFIG, enabling the grid-side converter to have reasonable compensation capabilities. Finally, the basic reactive power is adjusted using the compensation values, and the reactive power output of the transmission line is controlled, providing a reactive power compensation and control scheme. This improves the controllability and stability of the reactive power of the transmission line, resulting in smaller voltage fluctuations and more stable operation of the power grid. Attached Figure Description

[0011] Figure 1 This is a flowchart illustrating the reactive power control method provided in an embodiment of this application; Figure 2 This is a flowchart illustrating the calculation method for the output reactive power of the grid-side converter of a doubly-fed variable-speed pumped-storage generator provided in the embodiments of this application. Figure 3 This is a schematic diagram of the equivalent circuit of the doubly fed generator motor provided in the embodiments of this application.

[0012] Figure 4 This is a topology diagram of a doubly-fed variable-speed pumped-storage unit provided in an embodiment of this application; Figure 5 This is a flowchart illustrating the control method for the reactive power output of the grid-side converter of a doubly-fed variable-speed pumped-storage generator provided in the embodiments of this application. Figure 6This is a flowchart illustrating the method for determining the reactive power output of the grid-side converter of a doubly-fed variable-speed pumped-storage generator provided in an embodiment of this application. Figure 7 This is a schematic diagram of the process for reactive power compensation in the AC excitation system of a doubly-fed variable-speed pumped-storage unit under different operating conditions, provided in the embodiments of this application. Figure 8 This is a schematic diagram of the reactive power control device provided in the embodiments of this application; Figure 9 This is a schematic diagram of an optional structure of an electronic device provided in an embodiment of this application.

[0013] It should be noted that the terms "first" and "second" mentioned above are only used to distinguish between different options and do not represent the degree of superiority or inferiority of the options or their priority in the implementation process. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on this application. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0015] This application provides a method, apparatus, device, storage medium, and program product for controlling reactive power. In practical applications, the reactive power control method can be implemented by a reactive power control device, and the functional entities in the reactive power control device can be collaboratively implemented by the hardware resources of electronic equipment (such as computing resources like processors and communication resources).

[0016] The following describes various embodiments of the reactive power control method, apparatus, equipment, storage medium, and program product provided in this application.

[0017] The reactive power control method provided in this application embodiment will now be described using a doubly-fed generator motor as the actuator. (Reference) Figure 1 The process may include, but is not limited to, S101 to S105 described below.

[0018] S101. Determine the basic reactive power based on the line parameters of the transmission line.

[0019] A doubly-fed generator-motor (DFIG) is a type of motor that can simultaneously supply active and reactive power to the power grid through both the stator and rotor. It is widely used in wind power and pumped storage units. Its operating modes include generation mode and motoring mode, and it has the ability to flexibly adjust reactive power under different operating conditions.

[0020] Line parameters are used to calculate the basic reactive power on the transmission line. In some implementations, line parameters may include information such as the phase voltage, phase current, and their angles of the transmission line.

[0021] Reactive power refers to the portion of electrical energy that is transmitted in an AC circuit but not converted into useful power. It is usually caused by the phase difference between voltage and current. Although reactive power does not perform work, it plays an important role in maintaining grid voltage stability and improving transmission capacity.

[0022] Base reactive power characterizes the reactive power currently available on a transmission line. For example, when the base reactive power is low, more reactive power compensation is needed to maintain voltage stability; while when the base reactive power is high, only a small amount of compensation or no compensation may be needed. In some implementations, the base reactive power can be determined based on line parameters on the transmission line. The transmission circuit is a line where a doubly-fed induction generator (DFIG) transmits power to the grid. Further, the base reactive power can be determined based on the line parameters of the transmission line where the DFIG transmits power to the grid.

[0023] In some implementations, the base reactive power can be determined based on the phase voltage, phase current, and angle of the transmission line.

[0024] S102. Determine the input active power and input reactive power of the grid-side converter based on the operating parameters of the doubly-fed generator motor.

[0025] The grid-side converter is a key device connecting the doubly-fed generator motor and the power grid. It is mainly responsible for converting the energy of the AC excitation system into electrical energy that is suitable for grid access, and for controlling the active and reactive power.

[0026] The operating parameters of a doubly-fed generator (DFIG) are used to determine the input active power and input reactive power of the grid-side converter. In some implementations, the operating parameters of the DFIG may include resistance, current, and leakage reactance.

[0027] The input active power of the grid-side converter refers to the active power absorbed by the grid-side converter from the DC bus side. In a doubly-fed variable-speed pumped-storage unit, the generator-side converter rectifies the slip power on the rotor side into DC power and supplies it to the DC bus. The grid-side converter can absorb active power from the DC bus side to obtain the input active power. In some implementations, the input active power can be determined based on the operating parameters of the doubly-fed generator motor. Specifically, the input active power can be determined based on resistance and current.

[0028] The input reactive power of the grid-side converter refers to the reactive power absorbed by the grid-side converter from the grid side. Reactive power does not directly transfer energy; it is only used to establish a magnetic field (such as for motor excitation and line inductive loss compensation). In some implementations, the input reactive power can be determined based on the operating parameters of the doubly-fed generator. Specifically, it can be determined based on current and leakage reactance.

[0029] S103. Based on the input reactive power and input active power, determine the compensation value for the base reactive power.

[0030] The compensation value is a numerical value used to adjust the base reactive power. In some implementations, it can be calculated based on the input active and reactive power. This compensation value can increase the reactive power output of the transmission line, bringing it closer to its ideal operating state.

[0031] In some implementations, the compensation range can be determined based on the input reactive power and the input active power, and the compensation value can be any value within that compensation range.

[0032] S104. Compensate the base reactive power based on the compensation value to obtain the compensated reactive power.

[0033] In some implementations, the compensation range can be determined based on the compensation value and the baseline reactive power, and the compensated reactive power can be determined based on this compensation range. Specifically, mathematical operations are performed on the compensation value and the baseline reactive power to obtain the compensation range. The compensated reactive power can be one of the compensation values ​​within this compensation range.

[0034] S105. Control the reactive power output of the transmission line based on the compensated reactive power.

[0035] In some implementations, compensation can be achieved by adjusting the control of the rotor of the doubly-fed generator-motor (DFIG) so that the reactive power output of the rotor is close to the compensated reactive power. In other implementations, compensation can be achieved by adjusting the control of the grid-side converter by the DFIG so that the reactive power output of the grid-side converter is close to the compensated reactive power through adjustment of the DC capacitor.

[0036] The reactive power control scheme provided in this application includes, but is not limited to, reactive power control methods, devices, equipment, storage media, and program products. Specifically, the method includes: determining the basic reactive power based on the line parameters of the transmission line; the basic reactive power characterizing the reactive power currently available on the transmission line; the transmission line being a doubly-fed generator line transmitting power to the grid; determining the input active power and input reactive power of the grid-side converter based on the operating parameters of the doubly-fed generator; determining a compensation value for the basic reactive power based on the input reactive power and input active power; compensating the basic reactive power based on the compensation value to obtain the compensated reactive power; and controlling the reactive power output from the transmission line based on the compensated reactive power.

[0037] For this reactive power control scheme, firstly, the basic reactive power is determined based on the transmission line parameters, thereby clarifying the reactive power available in the current transmission line, avoiding excessively high or low voltage caused by blind compensation, and improving the voltage stability of the transmission line. Secondly, the active and reactive power input to the grid-side converter are calculated based on the operating parameters of the doubly-fed generator, and the compensation value is determined based on this active and reactive power. On the one hand, the potential of the reactive power output of the grid-side converter can be tapped; on the other hand, the reactive power compensation is matched with the operating state of the doubly-fed generator, enabling the grid-side converter to have reasonable compensation capabilities. Finally, the basic reactive power is adjusted through the compensation value, and the reactive power output of the transmission line is controlled, providing a reactive power compensation and control scheme that can improve the controllability and stability of the reactive power of the transmission line, resulting in smaller voltage fluctuations and more stable operation of the power grid.

[0038] The following describes the process in S102 of determining the input active power of the grid-side converter based on the operating parameters of the doubly-fed generator motor, assuming that the operating parameters of the doubly-fed generator motor include: stator end resistance, stator end current, rotor end resistance, and rotor end current. This process may include, but is not limited to, S111 to S113 described below.

[0039] S111. Determine the stator winding copper loss based on the stator end resistance and stator end current.

[0040] Stator terminal resistance refers to the resistance value connected to the stator winding of a doubly-fed generator motor, used to characterize the resistance of the internal conductors of the stator winding to the current. Stator terminal current is the actual current value passing through the stator winding, the magnitude of which depends on the load conditions and the motor's operating conditions. Stator winding copper losses are the energy losses generated by the stator terminal current across the stator terminal resistance.

[0041] In some implementations, the stator winding copper loss is obtained by multiplying the stator terminal resistance and the stator terminal current. Specifically, the square of the stator terminal current is first calculated, and then the product of the square of the stator terminal current and the stator terminal resistance is calculated to obtain the stator winding copper loss.

[0042] S112. Determine the rotor winding copper loss based on the rotor end resistance and rotor end current.

[0043] Rotor end resistance is the resistance value of the rotor windings in a doubly-fed generator motor. This resistance value reflects the resistance of the rotor windings to current. Rotor end current is the current flowing through the rotor windings, and its magnitude is determined by the slip and the regulation of the excitation system. The copper losses of the rotor windings are determined by both the rotor end current and the rotor end resistance.

[0044] In some implementations, the rotor winding copper loss is obtained by multiplying the rotor end resistance and the rotor end current. Specifically, the square of the rotor end current is first calculated, and then the product of the square of the rotor end current and the rotor end resistance is calculated to obtain the rotor winding copper loss.

[0045] S113. Determine the input active power based on the stator winding copper loss, rotor winding copper loss, and stator end active power.

[0046] In some implementations, the input active power is determined based on the sum of stator winding copper losses, rotor winding copper losses, and stator end active power. Further, the sum of stator end active power and stator winding copper losses is first calculated, and then the input active power is determined based on this sum, slip, and rotor winding copper losses. Specifically, the product of this sum and slip is first calculated, and then the sum of this product and rotor winding copper losses is calculated to obtain the input active power.

[0047] Based on the above technical means, by calculating the copper losses of the stator and rotor windings separately and combining them with the active power at the stator end, the active power input to the grid-side converter can be estimated more accurately, thereby providing more reliable basic data for the calculation of subsequent compensation values ​​and improving the overall control accuracy.

[0048] The following describes the process in S102 of determining the input reactive power of the grid-side converter based on the operating parameters of the doubly-fed generator motor, assuming that the operating parameters of the doubly-fed generator motor include: stator end current, rotor end current, stator leakage reactance, and rotor leakage reactance. This process may include, but is not limited to, S121 to S123 described below.

[0049] S121. Based on the stator leakage reactance and stator terminal current, determine the reactive power consumed by the stator leakage reactance.

[0050] Stator terminal current refers to the current in the stator winding of a doubly-fed generator (DFIG). This current reflects the DFIG's ability to output active and reactive power on the grid side. The rotor winding of a DFIG also contains rotor terminal current, which is typically controlled by an AC excitation system to regulate the DFIG's electromagnetic state.

[0051] The stator winding contains stator leakage reactance, a type of inductive reactance mainly caused by incomplete magnetic flux coupling due to uneven magnetic field distribution. Stator leakage reactance consumes a certain amount of reactive power. The rotor winding contains rotor leakage reactance, also a type of inductive reactance, which also affects reactive power. Stator leakage reactance, rotor leakage reactance, and rotor terminal current, among other parameters, serve as fundamental data for calculating the input reactive power of the grid-side converter.

[0052] By introducing the above parameters, the reactive power characteristics of the doubly-fed generator motor under different operating conditions can be reflected more accurately, thereby improving the accuracy of the grid-side converter in compensating for the reactive power of the transmission line.

[0053] The reactive power consumed by the stator leakage reactance is the reactive power loss caused by the stator leakage reactance. The magnitude of the reactive power consumed by the stator leakage reactance increases with the square of the stator terminal current. In some implementations, the square of the stator terminal current is first calculated, and then the product of the square of the stator terminal current and the stator leakage reactance is calculated to obtain the reactive power consumed by the stator leakage reactance. Since the calculation process of the reactive power consumed by the stator leakage reactance takes into account the energy loss caused by magnetic field asymmetry in the stator winding, it helps to improve the accuracy of the overall reactive power calculation.

[0054] In practical applications, the method of determining the reactive power consumed by the stator leakage reactance based on the stator leakage reactance and stator terminal current can help the system accurately identify the reactive power loss in the stator winding caused by ineffective energy conversion, thereby providing a basis for subsequent compensation strategies.

[0055] S122. Based on the rotor leakage reactance and rotor end current, determine the reactive power consumed by the rotor leakage reactance.

[0056] The reactive power consumed by the rotor leakage reactance is similar to that of the stator leakage reactance. However, due to the more complex structure and motion of the rotor windings, the reactive power consumption of the rotor windings exhibits greater dynamics. In some implementations, the square of the rotor terminal current is first calculated, and then the product of the square of the rotor terminal current and the rotor leakage reactance is calculated to obtain the reactive power consumed by the rotor leakage reactance.

[0057] By determining the reactive power consumed by the rotor leakage reactance based on the rotor leakage reactance and rotor end current, the additional reactive power demand that may exist in the rotor winding can be identified, thereby avoiding deviations in the reactive power compensation process.

[0058] S123. Determine the input reactive power based on the reactive power consumed by the stator leakage reactance, the reactive power consumed by the rotor leakage reactance, and the reactive power at the stator end.

[0059] In some implementations, the input reactive power is determined by summing the reactive power consumed by the stator leakage reactance, the reactive power consumed by the rotor leakage reactance, and the reactive power at the stator terminals. In other implementations, the reactive power consumed by the magnetizing reactance is determined based on the magnetizing reactance and the magnetizing current, and then the input reactive power is determined based on the reactive power consumed by the stator leakage reactance, the rotor leakage reactance, the stator terminals, and the magnetizing reactance. For determining the reactive power consumed by the magnetizing reactance based on the magnetizing reactance and the magnetizing current, the square of the magnetizing current is first calculated, and then the product of the square of the magnetizing current and the magnetizing reactance is calculated to obtain the reactive power consumed by the magnetizing reactance. To determine the input reactive power based on the reactive power consumed by the stator leakage reactance, rotor leakage reactance, stator terminal reactive power, and magnetizing reactance, the following steps are taken: First, calculate the sum of the stator terminal reactive power, stator winding copper losses, and magnetizing reactance. Then, based on this sum, slip, and rotor winding copper losses, determine the input reactive power. Specifically, first calculate the product of this sum and slip, then calculate the sum of this product and rotor winding copper losses to obtain the input reactive power.

[0060] Based on the reactive power consumed by the stator leakage reactance, the reactive power consumed by the rotor leakage reactance, and the reactive power at the stator end, the input reactive power is determined, realizing a comprehensive modeling of the input reactive power of the grid-side converter. It not only considers the reactive power at the stator end itself, but also includes the additional reactive power brought by the winding structure, thereby improving the reliability of the compensation effect.

[0061] Based on the above technical means, by calculating the reactive power consumed by the stator and rotor leakage reactance separately, and combining it with the reactive power at the stator end, the reactive power situation can be reflected more comprehensively, providing a more reasonable basis for determining the compensation value and further optimizing the reactive power control effect.

[0062] The following describes the process in S103 of determining the compensation value for the base reactive power based on the input reactive power and input active power. This process may include, but is not limited to, S131 and S132 described below.

[0063] S131. Determine the capacity of the machine-side converter based on the input reactive power and input active power.

[0064] The capacity of a generator-side converter characterizes the maximum reactive power output of the generator-side converter. Specifically, it refers to the maximum reactive power output capability of the generator-side converter under specific operating conditions, reflecting its capacity boundary in regulating the reactive power of the power grid. The capacity of the generator-side converter is typically determined by the capacity of the generator-side converter in the AC excitation system, which in turn depends on factors such as the slip rate of the doubly-fed variable-speed pumped-storage unit, the active power at the stator end, and the copper losses and leakage reactance of the stator and rotor windings. By calculating the apparent power of the generator-side converter, the upper limit of its capacity can be derived.

[0065] In some implementations, the capacity of the generator-side converter is determined based on the squares of the input reactive power and the input active power. Specifically, the sum of the squares of the input reactive power and the input active power is calculated, and the square root of the sum is determined as the capacity of the generator-side converter.

[0066] S132. Determine the compensation value based on the capacity of the machine-side converter and the compensation coefficient.

[0067] The compensation factor is a coefficient used to adjust the proportion of reactive power output from the grid-side converter. The value of the compensation factor is usually between 0 and 1, and can be set according to the actual needs of the power grid.

[0068] The compensation factor and the capacity of the generator-side converter jointly determine the final compensation value. Specifically, the compensation value is the generator-side converter capacity multiplied by the compensation factor. By setting the compensation value as the generator-side converter capacity multiplied by the compensation factor, precise control of reactive power output can be achieved. The generator-side converter can flexibly adjust the reactive power output under different operating conditions to better meet the dynamic needs of the power grid.

[0069] Based on the above technical means, by determining the compensation value based on the input active and reactive power of the computer-side converter capacity and in combination with the compensation coefficient, it is possible to dynamically adjust the size of the compensation value, ensuring that the compensation process does not exceed the capacity of the equipment, while maximizing the compensation efficiency and improving the stability and response speed of the power grid.

[0070] The following describes the process in S104 of compensating the base reactive power based on the compensation value to obtain the compensated reactive power. This process may include, but is not limited to, S141 to S143 described below.

[0071] S141. Determine the power difference between the base reactive power and the compensation value.

[0072] The power difference refers to the numerical difference between the base reactive power and the compensation value, which indicates the amount of reactive power that needs to be adjusted in the current system.

[0073] S142. Determine the sum of the base reactive power and the compensation value.

[0074] The sum of power refers to the total of the base reactive power and the compensation value. The sum of power reflects the total reactive power distribution in the power grid, that is, the total amount of reactive power originally existing in the power grid plus the compensation reactive power injected by the converter.

[0075] S503. Determine the compensated reactive power based on the power difference and the sum of the powers.

[0076] Compensated reactive power refers to the reactive power ultimately injected into the power grid after being regulated by the converter. In some implementations, a compensation range is constructed based on the power difference and the sum of the powers. Further, the power difference is determined as the lower limit of the compensation range, and the sum of the powers is determined as the upper limit. After obtaining the compensation range, the compensation value is determined based on it; this can be understood as the compensation value fluctuating within the compensation range.

[0077] Based on the above technical means, by calculating the power difference and the sum of power, the trend of reactive power change after compensation can be reflected more intuitively, thereby achieving more precise reactive power control and improving the stability and reliability of power grid operation.

[0078] The process of determining the basic reactive power based on the line parameters of the transmission line in S101 is described below, assuming that the line parameters include: phase voltage, phase current, phase voltage angle, and phase current angle. This process may include, but is not limited to, S151 to S153 described below.

[0079] S151. Determine the angle difference between the angle of the phase voltage and the angle of the phase current.

[0080] In AC circuits, both phase voltage and corresponding phase current change according to a sinusoidal law. However, due to the presence of inductive impedance (such as motor windings or inductors) or capacitive impedance (such as capacitors or cable-to-ground capacitance), there will be a difference in the time it takes for the two to reach their maximum value or zero point. This time difference is quantified by angle, which is the angle difference between phase voltage and phase current.

[0081] The phase voltage of a transmission line is a comprehensive representation of the voltage amplitude and phase angle of a certain phase relative to the neutral point in a three-phase AC transmission system. The phase current of a transmission line is a comprehensive representation of the current amplitude and phase angle flowing through a certain phase line in the transmission line. The angle difference between the phase voltage and the phase current of a transmission line reflects the ratio of active power to reactive power. For example, under a purely resistive load, the phase voltage and phase current of the transmission line are in phase, and the angle difference is 0 degrees; while under inductive or capacitive loads, the angle difference is greater than or less than 0 degrees, respectively. By measuring the phase difference between the phase voltage and the phase current of the transmission line, it is possible to determine whether there is reactive power demand in the transmission line, and this phase difference serves as the basis for subsequent reactive power calculations.

[0082] S152. Determine the sine value of the angle difference.

[0083] In some implementations, the sine value of the angle difference is obtained by performing a sine transformation on the angle difference.

[0084] The sine value of the angle difference between the phase voltage angle and the phase current angle of a transmission line is a key coefficient for calculating base reactive power. According to trigonometric function principles, base reactive power is directly proportional to the sine value; therefore, the larger the sine value, the higher the base reactive power. For example, if the angle difference is 30 degrees, the sine value for 30 degrees is 0.5; if the angle difference is 90 degrees, the sine value for 90 degrees is 1, indicating that the total power is base reactive power.

[0085] S153. Determine the base reactive power based on the product of the sine value, phase voltage, and phase current.

[0086] The product of the sine value of the angle difference, the phase voltage, and the phase current is used to determine the basic reactive power.

[0087] Based on the above technical means, the basic reactive power can be determined by the product of the sine value of the angle difference, the phase voltage and the phase current. This can quickly and accurately obtain the basic reactive power in the transmission line, providing reliable data support for subsequent compensation operations and improving the real-time performance and accuracy of the entire control process.

[0088] The following describes the process of controlling the reactive power output of the transmission line based on the compensated reactive power in step S105, assuming the line parameters include phase voltage. This process may include, but is not limited to, steps S161 to S165 described below.

[0089] S161. Perform sine and cosine transformations on each phase voltage setpoint to obtain the first sine component and the first cosine component.

[0090] The first sinusoidal component represents the voltage component of reactive power. The sinusoidal component represents the portion of the voltage perpendicular to the current and mainly corresponds to the transmission of reactive power.

[0091] The first cosine component represents the voltage component of active power. The cosine component represents the portion of the voltage that is in phase with the current, and mainly corresponds to the transmission of active power.

[0092] The phase voltage setpoint is determined based on the compensated reactive power. For example, if a significant reactive power deficit is detected in the transmission line at a certain moment, the proportion of the sinusoidal component will be increased accordingly to enhance the reactive power output capability. This achieves preliminary decoupling of the voltage signal, thereby improving response speed and control accuracy.

[0093] By performing sine and cosine decomposition on the three-phase AC voltage signal, the voltage components related to reactive power (sine components) and active power (cosine components) can be separated. A method for controlling the reactive power output of transmission lines using the compensated reactive power maps the voltage signal to a Cartesian coordinate system, thus facilitating subsequent PI regulator processing.

[0094] By decomposing the three-phase AC voltage signal into sine and cosine and mapping it to a rectangular coordinate system, changes in reactive power can be identified and controlled more accurately, providing a basis for subsequent control strategies.

[0095] S162. Perform sine and cosine transformations on each phase voltage to obtain the second sine component and the second cosine component.

[0096] In addition to using the setpoint, the current actual phase voltage also needs to undergo the same sine and cosine transformation to obtain a second sine component and a second cosine component. This operation of performing a sine and cosine transformation on the current actual phase voltage to obtain the second sine and cosine components is to obtain real-time voltage information for comparison with the setpoint, in order to perform closed-loop control. The sine and cosine components of the actual voltage reflect the current state of the power grid and are an important basis for determining whether output adjustment is needed.

[0097] The difference between the second sine and second cosine components and the first sine and first cosine components serves as the input signal for the PI controller. By comparing the setpoint and the actual value, the error signal can be calculated more accurately, providing a basis for the next adjustment step.

[0098] S163. The first sine component and the second sine component are adjusted by the PI controller to obtain the first PI value.

[0099] The PI controller is a commonly used control algorithm, consisting of a proportional (P) part and an integral (I) part. The proportional part enables a rapid response to the current error, while the integral part eliminates steady-state errors. When the difference between a first sine component and a second sine component is input into the PI controller, it generates a regulation signal called the first PI value. The first PI value represents the magnitude of the reactive power output adjustment and can be used for subsequent control execution.

[0100] A system that controls the reactive power output of transmission lines based on compensated reactive power can adjust parameters according to different operating conditions. For example, under high load conditions, the proportional gain can be increased to speed up the response; while under low load or stable operation, the proportional gain can be appropriately reduced to avoid over-adjustment. This flexible adjustment mechanism allows the system to adapt to the operational needs of different scenarios.

[0101] S164. The first cosine component and the second cosine component are adjusted by the PI controller to obtain the second PI value.

[0102] The difference between the first and second cosine components is input into the PI controller to generate the second PI value. This second PI value is then used to adjust the active power output to ensure the overall power balance of the power system. By simultaneously adjusting reactive and active power, refined control of the entire power system is achieved.

[0103] S165. Control the reactive power output of the transmission line based on the first PI value and the second PI value.

[0104] Based on the first and second PI values, a corresponding voltage command signal is generated and sent to the grid-side converter. The grid-side converter adjusts the magnitude and phase of its output voltage according to these commands, thereby changing the reactive power output of the transmission line. This process of controlling the reactive power output of the transmission line based on the compensated reactive power achieves dynamic regulation of reactive power, ensuring that the transmission line remains in optimal operating condition.

[0105] Based on the aforementioned technical means, precise control of reactive power is achieved by decomposing the phase voltage into sine and cosine and introducing it into a PI regulator. The method of controlling the reactive power output of transmission lines based on the compensated reactive power can effectively separate the control channels for active and reactive power. This method can independently adjust the output level of reactive power, thereby improving the stability and efficiency of transmission lines.

[0106] The process of controlling the reactive power output of the transmission line based on the compensated reactive power in S105 will be described below. This process may also include, but is not limited to, S171 to S173 described below.

[0107] S171. Determine the slip power based on the product of slip rate and electromagnetic power.

[0108] Slip refers to the relative difference between the rotor speed and the synchronous speed of the stator magnetic field in a doubly-fed generator motor. It reflects the degree of matching between the motor's operating state and the grid frequency, and is usually expressed as a percentage. The fixed speed of the stator magnetic field, determined by the grid frequency, is the synchronous speed, while the rotor speed is the actual mechanical speed at which the rotor rotates. In some implementations, slip is the ratio of the difference between the synchronous speed and the rotor speed to the synchronous speed.

[0109] Electromagnetic power characterizes the total electromagnetic energy transferred from the stator side to the rotor side. When alternating current is applied to the stator windings, a rotating magnetic field is generated. This magnetic field cuts the rotor windings, inducing a current. The current experiences a force in the magnetic field, generating an electromagnetic torque. The energy transferred through the magnetic field in this process is the electromagnetic power. In some implementations, the electromagnetic power can be determined based on the active power and slip at the stator end.

[0110] Slip power is the portion of electromagnetic power that is not converted into mechanical power due to the speed difference between the rotor and stator magnetic fields. In some implementations, slip power is calculated by multiplying the slip rate by the electromagnetic power.

[0111] S172. When the slip power is greater than the power threshold, the rotor rotation is controlled based on the compensated reactive power to control the reactive power output of the transmission line.

[0112] Controlling the rotor's rotation involves adjusting the phase and amplitude of the rotor current, which indirectly changes the coupling relationship between the rotor magnetic field and the stator magnetic field, thereby controlling the reactive power output from the stator side.

[0113] A slip power exceeding the power threshold indicates that the doubly-fed variable-speed pumped-storage unit is in a high-energy interaction state (e.g., the rotor feeds a large amount of slip power during power generation, or the rotor absorbs a large amount of energy during motoring). In this state, the generator-side converter is tightly coupled with the rotor, resulting in a fast response. Rotor control directly affects the stator reactive power output through magnetic field coupling, with a response time in the millisecond range. This allows for rapid filling of sudden reactive power gaps in the power grid and avoids continuous voltage fluctuations.

[0114] S173. When the slip power is less than or equal to the power threshold, the rotor rotation is controlled based on the compensated reactive power, and the grid-side converter is controlled to charge and discharge the DC capacitor to control the reactive power output of the transmission line.

[0115] Controlling the charging and discharging operation of the DC capacitor by the grid-side converter refers to adjusting the interaction of active power with the DC bus through the grid-side converter, changing the voltage and charge storage of the DC capacitor, and thus indirectly regulating the reactive power output of the grid-side converter to the grid. The DC capacitor acts as an energy buffer between the generator-side converter and the grid-side converter. During charging, the grid-side converter absorbs active power from the grid and stores it in the capacitor, while simultaneously adjusting the output current phase to output reactive power to the grid; during discharging, the capacitor releases energy, and the grid-side converter feeds active power back to the grid, which can also be superimposed on reactive power regulation. By utilizing the energy buffering characteristics of the DC capacitor, the grid-side converter can undertake additional reactive power compensation tasks while stabilizing the DC bus voltage, avoiding energy conflicts caused by relying solely on rotor control.

[0116] A slip power less than or equal to the power threshold indicates that the doubly-fed variable-speed pumped-storage unit is in a low-energy interaction state (e.g., close to synchronous speed, with smooth energy exchange between the rotor and the grid), the DC capacitor load is light, and it has redundancy to participate in reactive power regulation. The rotor control is responsible for basic reactive power regulation (maintaining the unit's excitation), while the grid-side converter undertakes additional reactive power compensation through charging and discharging. The two work together to cover a wider range of reactive power regulation with higher accuracy.

[0117] Based on the above technical means, by judging whether the slip power exceeds the set threshold, different control strategies can be selected to achieve optimal reactive power regulation under different operating conditions, enhance the system's ability to adapt to complex operating environments, and improve the safety and efficiency of power grid operation. For example, high slip is achieved by using rotor fast response, and low slip is achieved by using dual-device collaborative fine-tuning, always allowing the most suitable equipment to undertake reactive power control, and avoiding regulation lag or overload caused by capacity mismatch.

[0118] The reactive power control scheme provided in this application will be described below through an embodiment.

[0119] In recent years, new energy sources such as wind power and photovoltaics have been developed on a large scale. However, due to the unstable supply of these new energy sources, which are easily affected by factors such as weather, season, and altitude, the large-scale integration of these new energy sources into the grid will greatly increase the nonlinearity of the system. At the same time, more and more equipment requiring reactive power is being connected to the grid, necessitating reactive power compensation equipment to increase the transmission capacity of transmission lines. In addition, long transmission lines also have a certain amount of reactance.

[0120] Doubly-fed induction generators (DFIGs) exchange power with the power grid through their stator, rotor, and AC excitation system. When the rotor outputs power to the grid, the proportion of reactive and active power in the output power can be controlled by a converter, thereby controlling the reactive power of the transmission line. Currently, DFIGs are mainly used in DFIG wind turbines and DFIG-type variable-speed pumped storage units. DFIG wind turbines suffer from unstable energy supply and small AC excitation system capacity, while DFIG-type variable-speed pumped storage units offer stable energy supply, large single-unit capacity, and fast system response. Through frequent power absorption and output, they can effectively alleviate the nonlinearity of the system.

[0121] Currently, there is limited research in China's hydropower sector on reactive power output through the rotor of doubly-fed variable-speed pumped storage units. Furthermore, variable-speed pumped storage units are characterized by large single-unit power (typically, the single-unit rotor power of large units exceeds 100MW). Therefore, researching reactive power compensation control of the grid-side converter of the doubly-fed variable-speed pumped storage rotor is crucial for grid friendliness.

[0122] This application innovatively studies a reactive power control and calculation method for a doubly-fed variable-speed pumped-storage unit, which uses a grid-side converter and a DC capacitor in the AC excitation system to achieve reactive power compensation similar to that of a unified power flow controller.

[0123] Currently, the main reactive power compensation equipment used in transmission lines includes unified power flow controllers, static synchronous series compensators, and static synchronous compensators. Conventional reactive power compensation equipment is highly specialized, but requires separate installation, and margin must be considered to reduce the cost of subsequent grid expansion, which may result in significant upfront investment.

[0124] Doubly fed-forward (DFFP) variable-speed turbine generator sets include a DFFP generator motor and an AC excitation system. The DFFP generator motor can control its reactive power output by adjusting the rotor excitation current through the AC excitation system, and it can also output reactive power to the grid through the AC excitation system. In certain operating conditions of both generator and motor modes, the slip power of the DFFP generator motor is output through the rotor and the AC excitation system. Therefore, the control method of the grid-side converter and the reactive power calculation method of the transmission line are crucial. This application provides a control method and a reactive power calculation method for the grid-side converter of the AC excitation system of a DFFP variable-speed pumped-storage turbine generator set, which compensates for the reactive power of the transmission line by injecting reactive power.

[0125] The active and reactive power on a transmission line can be calculated from the voltage and current amplitudes and phase differences of the line. By calculating the apparent power on the rotor side of a doubly-fed variable-speed pumped storage unit, the capacity of the generator-side converter of the AC excitation system can be obtained, and then the reactive power that the grid-side converter can provide can be calculated.

[0126] The calculation process of apparent power of transmission lines: (1); in, The apparent power of the transmission line. , , This represents the vector form of the phase voltages of an AC transmission line. , , This represents the vector form of the phase current in an AC transmission line.

[0127] The following is combined with Figure 2 This paper provides a detailed explanation of the calculation method for the reactive power output of the grid-side converter of a doubly-fed variable-speed pumped-storage generator.

[0128] S201. Determine the basic parameters of the transmission line and the basic parameters of the doubly-fed generator.

[0129] S202. Determine the reactive power compensation data required for the transmission line.

[0130] The calculation process for reactive power of transmission lines: (2); in, The reactive power of the transmission line. , , This refers to the effective value of the phase voltage of an AC transmission line. , , This refers to the effective value of the phase voltage of an AC transmission line. , , The angle of the phase voltage of an AC transmission line. , , The angle of the phase current in an AC transmission line.

[0131] S203. Calculate the capacity of the machine-side converter of the rotor AC excitation system by using the slip rate of the doubly fed generator motor, stator and rotor losses, and excitation parameters.

[0132] The capacity of the machine-side converter in the rotor AC excitation system is calculated using the slip rate, stator and rotor losses, and excitation parameters of the doubly-fed generator motor. For example... Figure 3 As shown, the stator terminal phase voltage is The slip ratio is The phase voltage referred from the rotor end to the stator end is: The stator terminal resistance is The stator terminal current is The rotor end resistance is The rotor end current is stator leakage current is Rotor leakage reactance is The excitation reactance is The excitation current is The specific calculation steps are as follows: S211. Determine the reactive power consumed by the stator winding copper loss and leakage reactance: (3); S212. Determine the reactive power consumed by the rotor winding copper loss and leakage reactance: (4); S213. Determine the reactive power consumed by the excitation reactor: (5); The calculation process for the active power input to the generator-side converter of the AC excitation system of a doubly-fed variable-speed pumped storage unit is as follows: (6); in, The active power input to the machine-side converter of the AC excitation system. For doubly-fed variable speed units, slip rate This refers to the active power at the stator end of the doubly-fed generator unit. For stator winding copper loss, This refers to the copper loss of the rotor winding.

[0133] The calculation process for the reactive power input of the generator-side converter of the AC excitation system of a doubly-fed variable-speed pumped storage unit is as follows: (7); in, The reactive power input to the machine-side converter of the AC excitation system. This refers to the reactive power at the stator end of the doubly-fed generator unit. For stator leakage reactance, For rotor leakage reactance, This refers to the reactive power consumed by the magnetizing reactor.

[0134] S216. Based on the active and reactive power inputs of the AC excitation system's machine-side converter, the capacity of the AC excitation system's machine-side converter is calculated as follows: (8); in, This refers to the inverter capacity.

[0135] S204. Determine the reactive power output of the grid-side converter of the rotor AC excitation system based on the capacity of the machine-side converter. The calculation process is shown in formula (9): (9); in, The reactive power output of the grid-side converter in the AC excitation system. The coefficient is added based on the reactive power compensation required for the transmission line, and theoretically can be taken as 0-1.

[0136] S205. Based on the reactive power of the transmission line and the reactive power output of the grid-side converter of the AC excitation system of the doubly-fed variable-speed pumped storage unit, calculate the compensated reactive power of the transmission line. The calculation process is shown in formula (10): (10); in, To compensate for the reactive power of the transmission line.

[0137] Figure 4 This is a topology diagram of a doubly-fed variable-speed pumped-storage unit provided in an embodiment of this application. See also... Figure 4 The grid 402 is connected to the grid-side converter 404 of the doubly-fed induction generator (DFIG) 401. The grid-side converter 404 converts the three-phase AC power to DC power, and then the generator-side converter 403 converts the DC power back to three-phase AC power, which is then input to the rotor of the DFIG 401. The rotor of the DFIG 401 exchanges power with the stator through a magnetic field. The stator is directly connected to the grid 402, enabling power flow. The DFIG 401 includes stator windings and rotor windings. The stator windings are directly connected to the grid 402, transmitting or absorbing most of the active power. The rotor windings are connected to the generator-side converter 403 via slip rings, receiving the excitation current. By controlling the amplitude, frequency, and phase of the rotor current, the speed, torque, reactive power output from the rotor side to the grid 402 via the grid-side converter 404, and reactive power output from the stator side to the grid 402 can be precisely adjusted. Both the grid-side converter 404 and the generator-side converter 403 are composed of insulated-gate bipolar transistors 405. Furthermore, the AC excitation system employs a three-level neutral-point clamping control method. Each bridge arm consists of four power switching devices and two diodes. This structure is primarily used to reduce switching losses and increase the withstand voltage of each bridge arm.

[0138] like Figure 5 As shown, a control method for the reactive power output of the grid-side converter in a doubly-fed variable-speed pumped-storage (DFFP) generator is proposed. This method achieves control of the reactive power output of the DFFP grid-side converter by splitting the AC voltage into sine and cosine components for control. Based on the AC current phase, the AC voltage is split into sine and cosine components for control. Decoupling is achieved through dqo transformation, completing the control of the grid-side converter's output reactive power. The output reactive power is determined based on the output AC current and voltage phase. The specific operation steps are as follows: S501. Determine the phase of the AC current, determine the set values ​​of the sine and cosine components of the AC voltage based on the phase, and control the AC voltage by combining the actual values ​​of the sine and cosine components of the AC voltage.

[0139] Wherein, PLL stands for Phase-Locked Loop. and This represents the function changes corresponding to sine and cosine. , , This indicates the set value of the phase voltage of an AC transmission line. , , , , , This indicates a corresponding functional change in the effective value of the phase voltage of an AC transmission line. To represent multiplication, This represents superposition. The phase voltage is split into active and reactive components and controlled separately by PI. The data obtained from the PI control are then varied using sine and cosine functions and multiplied by a factor. After superposition, the three-phase voltage data are transformed using the abc / dqo method.

[0140] S502. Determine the components of the AC voltage in the dqo coordinate system and complete the construction of the voltage loop control method; in, and These represent the voltage components in the d and q coordinate systems, respectively. and These represent the reference values ​​of the voltage components in the d and q coordinates, respectively, and the voltage loop is constructed by varying the PI.

[0141] S503. Determine the components of the alternating current in the dq0 coordinate system and complete the construction of the current loop control method; in, and These represent the current components in the d and q coordinates, respectively. and These represent the reference values ​​of the current components in the d and q coordinate systems, respectively. A current loop is constructed through PI control. Finally, the voltage components are superimposed to complete the control.

[0142] S504. Based on the control method, obtain the control waveform of SVPWM.

[0143] like Figure 6 The diagram shows a flowchart illustrating a method for determining the reactive power output of the grid-side converter in a doubly-fed variable-speed pumped-storage generator. (See also...) Figure 6 PLL stands for Phase-Locked Loop. and This represents the function changes corresponding to sine and cosine. Indicates phase voltage. Indicates phase current, To represent multiplication, The process involves superposition. First, the phase angle obtained from the PLL based on the phase current is sinusoidally transformed to obtain the sine and cosine values ​​of the phase angle. Second, the product of the sinusoidal component of the phase voltage and the sine value of the phase angle is calculated to obtain the first product result. Then, the product of the cosine component of the phase voltage and the cosine value of the phase angle is calculated to obtain the second product result. Finally, the first and second product results are superimposed to determine the reactive power output of the grid-side converter.

[0144] like Figure 7 As shown, a flowchart illustrating reactive power compensation for AC excitation systems under different operating conditions of doubly-fed variable-speed pumped-storage units is presented. Based on different operating conditions of the doubly-fed variable-speed pumped-storage units, the AC excitation system achieves reactive power compensation for transmission lines through two methods: using a grid-side converter alone and through slip power. The specific operation steps are as follows: S701. Determine the operating conditions of the doubly-fed generator motor.

[0145] S702. Determine if the unit has slip power. If the unit has slip power, proceed to S703; otherwise, proceed to S705. The slip power is calculated as follows (11): (11); in, Electromagnetic power, For slippage, This refers to slip power.

[0146] S703. Determine the reactive power compensation data required for transmission lines.

[0147] S704. By controlling the phase and amplitude of the output AC voltage and AC current through the grid-side converter of the rotor AC excitation system, reactive power compensation is provided for the transmission line.

[0148] S705. Shut down the machine-side converter of the AC excitation system, and only connect the grid-side converter and DC capacitor.

[0149] S706. Determine the reactive power compensation data required for transmission lines.

[0150] S707. The grid-side converter controls the charging and discharging of DC capacitors to achieve reactive power compensation for transmission lines.

[0151] This application presents a schematic flowchart illustrating the coordinated operation of grid-side converters for multiple doubly-fed variable-speed pumped-storage units. Based on the AC excitation systems of multiple doubly-fed variable-speed pumped-storage units, flexible control of reactive power in transmission lines can be achieved through coordinated operation. The method includes the following steps: S11. Determine the operating conditions of the doubly-fed generator motor.

[0152] S12. Determine the reactive power compensation data required for the transmission line.

[0153] S13. Prioritize starting grid-side converters and DC capacitors of units without slip power in operating conditions to perform reactive power compensation on transmission lines.

[0154] S14. The reactive power compensation function of the AC excitation system of the unit with slip power is started according to a certain proportion.

[0155] This application presents a flowchart illustrating a method for replacing part of the redundant capacity of flexible AC transmission system equipment with a grid-side converter in a doubly-fed variable-speed pumped-storage generator unit. Based on the capacity, slip power, and flexibility of the AC excitation system, the grid-side converter can compensate for the reactive power of the transmission line. By determining the required reactive power of the transmission line and the operating conditions of the doubly-fed generator unit, the method replaces part of the redundant capacity of the flexible AC transmission system equipment. The operational steps of this method are as follows: S21. Determine the operating conditions of the doubly-fed generator motor.

[0156] S22. Determine the reactive power compensation data required for the transmission line.

[0157] S23. Determine the compensation capacity of the reactive power compensation equipment for existing transmission lines.

[0158] S24. Based on the scheme of coordinated operation of grid-side converters of multiple doubly-fed variable-speed pumped-storage units, reactive power compensation is performed on transmission lines.

[0159] S25. After the output compensation power of multiple units reaches a certain level, it replaces the redundant capacity of the flexible AC transmission system equipment and provides reactive power compensation for the transmission line.

[0160] This application presents a flowchart illustrating the collaborative operation of a grid-side converter in a doubly-fed variable-speed pumped-storage generator unit with flexible AC transmission system equipment. Based on the capacity and slip power of the AC excitation system, the grid-side converter can flexibly compensate for reactive power in transmission lines by working collaboratively with flexible AC transmission system equipment. The method includes the following operational steps: S31. Determine the operating conditions of the doubly-fed generator motor.

[0161] S32. Determine the reactive power compensation data required for the transmission line.

[0162] S33. Based on the scheme of coordinated operation of grid-side converters of multiple doubly-fed variable-speed pumped-storage units, reactive power compensation is performed on transmission lines.

[0163] S34. After the reactive power compensation capacity of multiple AC excitation systems reaches the capacity of one flexible DC transmission equipment, the reactive power of the AC excitation systems will be slowly transferred to the flexible DC transmission equipment.

[0164] This application proposes a method for the coordinated operation of a grid-side converter and a generator motor in a doubly-fed variable-speed pumped-storage unit. Based on the operating conditions of the generator motor, the capacity of the AC excitation system, and the slip power, the grid-side converter can compensate for the reactive power of the transmission line by working in coordination with the generator motor. The method includes the following operational steps: S41. Determine the operating conditions of the doubly-fed generator motor.

[0165] S42. Determine the reactive power compensation data required for the transmission line.

[0166] S43. Prioritize the use of the unit's AC excitation system capacity for reactive power compensation of transmission lines.

[0167] S44. After the reactive power compensation capacity of multiple AC excitation systems reaches the capacity of one generator motor, the reactive power of the AC excitation system is slowly transferred to the generator motor by adjusting the excitation system.

[0168] This application proposes a method for the coordinated operation of a grid-side converter, flexible AC transmission system equipment, and a generator motor in a doubly-fed variable-speed pumped-storage unit. Based on the operating conditions of the generator motor, the capacity of the AC excitation system, and the slip power, the grid-side converter can compensate for the reactive power of the transmission line by cooperating with the generator motor and the flexible AC transmission system equipment. The method includes the following operational steps: S51. Determine the operating conditions of the doubly-fed generator motor.

[0169] S52. Determine the reactive power compensation data required for transmission lines.

[0170] S53. Prioritize the use of the AC excitation system capacity of the generating unit for reactive power compensation of the transmission line.

[0171] S54. Determine the current stage of the power grid. For example, normal hours, peak hours, and off-peak hours.

[0172] S55. During peak and off-peak electricity consumption periods, the reactive power compensation capacity of the AC excitation system is gradually transferred to the flexible DC transmission equipment, with the generator motor providing auxiliary regulation. During normal periods, the reactive power compensation capacity of the AC excitation system is gradually transferred to the generator motor, and then to the flexible DC transmission equipment.

[0173] As can be seen from the above embodiments, the embodiments of this application bring the following beneficial effects: This application provides a method for calculating the reactive power output of a grid-side converter in a doubly-fed variable-speed pumped-storage generator (DFIG) system. The method determines the rotor-side converter capacity by analyzing the input power of the generator motor rotor, and then determines the reactive power output of the rotor-side converter. Compared to related technologies, this application enables the rotor AC excitation system of the DFIG generator motor to have reactive power compensation functionality.

[0174] This application provides a control method for the reactive power output of a grid-side converter in a doubly-fed variable-speed pumped-storage generator unit. By preprocessing AC voltage data, the reactive power output of the rotor grid-side converter is determined. Compared to related technologies, this application improves control accuracy.

[0175] In this embodiment, the rotor AC excitation system of the doubly-fed generator motor has the same reactive power compensation function as the flexible AC transmission system equipment, but the reactive power output of the doubly-fed generator motor's AC excitation system is more flexible. For example, the unified power flow controller needs to consider margin and the increase in subsequent transmission line capacity during installation, which increases construction costs, while the AC excitation system of the variable-speed pumped-storage unit can flexibly change the amount of reactive power output according to the needs of the transmission line.

[0176] In this embodiment, the rotor AC excitation system of the doubly fed generator can cooperate with the generator motor and the flexible AC transmission system equipment to jointly achieve reactive power compensation of the transmission line, effectively reducing the operating cost of the transmission line.

[0177] Based on the above-described reactive power control method, this application provides a reactive power control device, such as... Figure 8 As shown, the reactive power control device 80 includes a first determining unit 801, a second determining unit 802, a third determining unit 803, a compensation unit 804, and a control unit 805.

[0178] in: The first determining unit 801 is used to determine the basic reactive power based on the line parameters of the transmission line; the basic reactive power represents the reactive power that can be provided on the transmission line at present. The second determining unit 802 is used to determine the input active power and input reactive power of the grid-side converter based on the operating parameters of the doubly fed generator motor. The third determining unit 803 is used to determine the compensation value for the base reactive power based on the input reactive power and the input active power. The compensation unit 804 is used to compensate the base reactive power based on the compensation value to obtain the compensated reactive power. Control unit 805 is used to control the transmission line based on the compensated reactive power.

[0179] In some embodiments, when the operating parameters of the doubly-fed generator motor include: stator end resistance, stator end current, rotor end resistance, and rotor end current, the second determining unit is further configured to: determine the stator winding copper loss based on the stator end resistance and stator end current; determine the rotor winding copper loss based on the rotor end resistance and rotor end current; and determine the input active power based on the stator winding copper loss, rotor winding copper loss, and stator end active power.

[0180] In some embodiments, when the operating parameters of the doubly-fed generator motor include: stator terminal current, rotor terminal current, stator leakage reactance, and rotor leakage reactance, the second determining unit is further configured to: determine the reactive power consumed by the stator leakage reactance based on the stator leakage reactance and stator terminal current; determine the reactive power consumed by the rotor leakage reactance based on the rotor leakage reactance and rotor terminal current; and determine the input reactive power based on the reactive power consumed by the stator leakage reactance, the reactive power consumed by the rotor leakage reactance, and the stator terminal reactive power.

[0181] In some embodiments, the third determining unit is further configured to: determine the capacity of the machine-side converter based on the input reactive power and the input active power; the capacity of the machine-side converter characterizes the maximum reactive power output by the machine-side converter; and determine the compensation value based on the capacity of the machine-side converter and the compensation coefficient.

[0182] In some embodiments, the compensation unit is further configured to: determine the power difference between the base reactive power and the compensation value; determine the sum of the power of the base reactive power and the compensation value; and determine the compensated reactive power based on the power difference and the sum of the power.

[0183] In some embodiments, when the line parameters include phase voltage, phase current, the angle of phase voltage, and the angle of phase current, the third determining unit is further configured to: determine the angle difference between the angle of phase voltage and the angle of phase current; determine the sine value of the angle difference; and determine the basic reactive power based on the product of the sine value, phase voltage, and phase current.

[0184] In some embodiments, when the line parameters include phase voltages, the control unit is further configured to: perform sine and cosine transformations on each phase voltage setpoint to obtain a first sine component and a first cosine component; the first sine component represents the voltage component of reactive power; the first cosine component represents the voltage component of active power; the phase voltage setpoint is determined based on the compensated reactive power; perform sine and cosine transformations on each phase voltage to obtain a second sine component and a second cosine component; adjust the first sine component and the second sine component using a PI regulator to obtain a first PI value; adjust the first cosine component and the second cosine component using a PI regulator to obtain a second PI value; and control the reactive power output of the transmission line based on the first PI value and the second PI value.

[0185] In some embodiments, the control unit is further configured to: determine the slip power based on the product of slip rate and electromagnetic power; the electromagnetic power characterizes the total electromagnetic energy transferred from the stator side to the rotor side; when the slip power is greater than a power threshold, control the rotation of the rotor based on the compensated reactive power to control the reactive power output of the transmission line; when the slip power is less than or equal to the power threshold, control the rotation of the rotor based on the compensated reactive power, and control the grid-side converter to perform charging and discharging operations on the DC capacitor to control the reactive power output of the transmission line.

[0186] It should be noted that the reactive power control device provided in this application embodiment includes all the units included, which can be implemented by a processor in an electronic device; of course, it can also be implemented by specific logic circuits; in the implementation process, the processor can be a central processing unit (CPU), a microprocessor (MPU), a digital signal processor (DSP), or a field-programmable gate array (FPGA), etc.

[0187] The descriptions of the above device embodiments are similar to those of the above method embodiments, and have similar beneficial effects. For technical details not disclosed in the device embodiments of this application, please refer to the descriptions of the method embodiments of this application for understanding.

[0188] It should be noted that, in the embodiments of this application, if the above-mentioned reactive power control method is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiments of this application, or the part that contributes to the related technology, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, mobile hard drives, read-only memory (ROM), magnetic disks, or optical disks. Thus, the embodiments of this application are not limited to any specific hardware and software combination.

[0189] This application provides an electronic device that can implement the reactive power control method described above.

[0190] In one example, Figure 9 This is a schematic diagram of the structure of the electronic device provided in the embodiments of this application, such as... Figure 9 As shown, the electronic device 90 includes: a processor 901 and a memory 902 configured to store computer programs capable of running on the processor; The processor 901 is configured to execute the method steps in the foregoing embodiments when running a computer program.

[0191] Of course, in practical applications, such as Figure 9 As shown, the various components in the electronic device 90 are coupled together via a bus system 903. It is understood that the bus system 903 is used to achieve communication between these components. In addition to a data bus, the bus system 903 also includes a power bus, a control bus, and a status signal bus. However, for clarity, in... Figure 9 The general designated all buses as Bus System 903.

[0192] In practical applications, the aforementioned processor can be at least one of the following: Application-Specific Integrated Circuit (ASIC), Digital Signal Processing Device (DSPD), Programmable Logic Device (PLD), Field-Programmable Gate Array (FPGA), controller, microcontroller, and microprocessor. It is understood that, for different devices, the electronic device used to implement the above processor function can also be other types, and the embodiments of this application do not specifically limit it.

[0193] The aforementioned memory can be volatile memory, such as random access memory (RAM). Access memory); or non-volatile memory, such as read-only memory (ROM), flash memory, hard disk drive (HDD), or solid-state drive (SSD); or a combination of the above types of memory, and providing instructions and data to the processor.

[0194] This application provides a storage medium, namely a computer-readable storage medium, on which a computer program or instructions are stored. When the computer program or instructions are executed by a processor, they implement the steps in any of the reactive power control methods provided in the above embodiments.

[0195] This application provides a computer program product, which includes a computer program or instructions. When the computer program or instructions are executed by a processor, they implement the steps in any of the reactive power control methods provided in the above embodiments.

[0196] It should be noted that the descriptions of the above embodiments of storage media, devices, apparatuses, and program products are similar to the descriptions of the above method embodiments and have similar beneficial effects. For technical details not disclosed in the embodiments of storage media, devices, apparatuses, and program products of this application, please refer to the descriptions of the method embodiments of this application for understanding.

[0197] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "in one embodiment" or "in some embodiments" appearing throughout the specification do not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It should be understood that in the various embodiments of this application, the sequence numbers of the above-described processes do not imply a sequential order of execution; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application. The sequence numbers of the above-described embodiments are merely descriptive and do not represent the superiority or inferiority of the embodiments.

[0198] It should be noted that, in this document, 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. Unless otherwise specified, 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 that element.

[0199] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, and the indirect coupling or communication connection between devices or units can be electrical, mechanical, or other forms.

[0200] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units. They may be located in one place or distributed across multiple network units. Some or all of the units may be selected to achieve the purpose of this embodiment according to actual needs.

[0201] In addition, each functional unit in the various embodiments of this application can be integrated into one processing unit, or each unit can be a separate unit, or two or more units can be integrated into one unit; the integrated unit can be implemented in hardware or in the form of hardware plus software functional units.

[0202] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps of the above method embodiments. The aforementioned storage medium includes various media that can store program code, such as mobile storage devices, read-only memory (ROM), magnetic disks, or optical disks.

[0203] Alternatively, if the integrated units described above are implemented as software functional modules and sold or used as independent products, they can also be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the embodiments of this application, or the parts that contribute to related technologies, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, ROMs, magnetic disks, or optical disks.

[0204] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of this application are included within the scope of protection of this application.

Claims

1. A reactive power control method applied to a doubly-fed generator motor, characterized in that, The method includes: The basic reactive power is determined based on the line parameters of the transmission line; the basic reactive power represents the reactive power currently available on the transmission line; the transmission circuit is the line through which the doubly-fed generator transmits power to the power grid. The input active power and input reactive power of the grid-side converter are determined based on the operating parameters of the doubly fed generator motor. Based on the input reactive power and the input active power, determine the compensation value for the base reactive power; The basic reactive power is compensated based on the compensation value to obtain the compensated reactive power. The reactive power output of the transmission line is controlled based on the compensated reactive power.

2. The method according to claim 1, characterized in that, When the operating parameters of the doubly-fed generator motor include: stator end resistance, stator end current, rotor end resistance, and rotor end current, determining the input active power of the grid-side converter based on the operating parameters of the doubly-fed generator motor includes: The stator winding copper loss is determined based on the stator terminal resistance and the stator terminal current. The rotor winding copper loss is determined based on the rotor end resistance and the rotor end current. The input active power is determined based on the stator winding copper loss, the rotor winding copper loss, and the stator end active power.

3. The method according to claim 1, characterized in that, When the operating parameters of the doubly-fed generator motor include: stator terminal current, rotor terminal current, stator leakage reactance, and rotor leakage reactance, determining the input reactive power of the grid-side converter based on the operating parameters of the doubly-fed generator motor includes: Based on the stator leakage reactance and the stator terminal current, determine the reactive power consumed by the stator leakage reactance; Based on the rotor leakage reactance and the rotor terminal current, determine the reactive power consumed by the rotor leakage reactance; The input reactive power is determined based on the reactive power consumed by the stator leakage reactance, the reactive power consumed by the rotor leakage reactance, and the reactive power at the stator end.

4. The method according to claim 1, characterized in that, The step of determining the compensation value for the base reactive power based on the input reactive power and the input active power includes: The capacity of the machine-side converter is determined based on the input reactive power and the input active power; the capacity of the machine-side converter characterizes the maximum reactive power output by the machine-side converter. The compensation value is determined based on the capacity of the machine-side converter and the compensation coefficient.

5. The method according to claim 1, characterized in that, The step of compensating the base reactive power based on the compensation value to obtain the compensated reactive power includes: Determine the power difference between the base reactive power and the compensation value; Determine the sum of the base reactive power and the compensation value; The compensated reactive power is determined based on the power difference and the sum of the power values.

6. The method according to claim 1, characterized in that, When the line parameters include phase voltage, phase current, phase voltage angle, and phase current angle, the determination of the basic reactive power based on the transmission line parameters includes: Determine the angle difference between the angle of the phase voltage and the angle of the phase current; Determine the sine value of the angle difference; The base reactive power is determined based on the product of the sine value, the phase voltage, and the phase current.

7. The method according to any one of claims 1-6, characterized in that, When the line parameters include phase voltage, controlling the reactive power output of the transmission line based on the compensated reactive power includes: Each phase voltage setpoint is subjected to sine and cosine transformations to obtain a first sine component and a first cosine component; the first sine component represents the voltage component of reactive power; the first cosine component represents the voltage component of active power; the phase voltage setpoint is determined based on the compensated reactive power. By performing sine and cosine transformations on each phase voltage, the second sine component and the second cosine component are obtained. The first PI value is obtained by adjusting the first sine component and the second sine component using a PI controller. The first cosine component and the second cosine component are adjusted by the PI regulator to obtain the second PI value; The reactive power output of the transmission line is controlled based on the first PI value and the second PI value.

8. The method according to any one of claims 1-6, characterized in that, The control of reactive power output from the transmission line based on the compensated reactive power includes: The slip power is determined based on the product of slip rate and electromagnetic power; the electromagnetic power represents the total electromagnetic energy transferred from the stator side to the rotor side. When the slip power is greater than the power threshold, the rotor rotation is controlled based on the compensated reactive power to control the reactive power output of the transmission line. When the slip power is less than or equal to the power threshold, the rotor is controlled to rotate based on the compensated reactive power, and the grid-side converter is controlled to charge and discharge the DC capacitor to control the reactive power output of the transmission line.

9. A reactive power control device, characterized in that, The device includes: The first determining unit is used to determine the basic reactive power based on the line parameters of the transmission line; the basic reactive power represents the reactive power currently available on the transmission line. The second determining unit is used to determine the input active power and input reactive power of the grid-side converter based on the operating parameters of the doubly fed generator motor. The third determining unit is used to determine the compensation value for the base reactive power based on the input reactive power and the input active power. The compensation unit is used to compensate the basic reactive power based on the compensation value to obtain the compensated reactive power; A control unit is used to control the transmission line based on the compensated reactive power.

10. An electronic device, characterized in that, The electronic device includes a memory and a processor. The memory stores a computer program or instructions, which, when executed by the processor, implement any of the methods provided in claims 1-8.

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