Method and device for frequency adjustment of an alternating current network, storage medium and computer device

Abstract

The application discloses a frequency adjustment method and device of an alternating current power grid, a storage medium and computer equipment. The method comprises the following steps: monitoring the power grid frequency of the alternating current power grid, determining the frequency fluctuation range of the power grid, and comparing the frequency fluctuation range with three preset fluctuation ranges; when the frequency fluctuation range exceeds the first preset fluctuation range and is less than the second preset fluctuation range, performing voltage outer loop current inner loop control of a full-power converter based on frequency feedback control, so as to adjust the active power output by the full-power converter and reduce the frequency fluctuation range of the alternating current power grid; and when the frequency fluctuation range exceeds the third preset fluctuation range, performing voltage outer loop current inner loop control of the full-power converter based on frequency feedback control and virtual voltage feedback control, so as to adjust the active power output by the full-power converter and reduce the power grid frequency fluctuation range of the alternating current power grid. The above method can improve the stability of the alternating current power grid.

Description

Technical Field

[0001] This invention relates to the field of wind power and power grid frequency control technology, and in particular to a method, apparatus, storage medium and computer equipment for adjusting the frequency of an AC power grid. Background Technology

[0002] As new power systems accelerate their transition to high-proportion renewable energy, wind power penetration continues to rise. However, its characteristic of connecting to the grid through full-power converters leads to the decoupling of generators from the AC grid, making it difficult to provide the inertia and frequency regulation support of traditional synchronous units, posing a severe challenge to the frequency stability of the AC grid.

[0003] Existing wind turbines mostly use virtual inertia control or droop control to participate in frequency regulation control in order to stabilize the frequency fluctuations of the AC power grid. However, the former is prone to energy overdraft and secondary drops, while the latter is limited by reserve capacity and has limited regulation capabilities. Especially in the scenario of wind power being transmitted over long distances via multi-terminal flexible DC transmission (VSC-MTDC), it may exacerbate the dynamic instability of the AC power grid frequency, resulting in low stability of the AC power grid. Summary of the Invention

[0004] In view of this, this application provides a frequency adjustment method, apparatus, storage medium and computer equipment for AC power grids, with the main purpose of solving the technical problem of low stability of AC power grids.

[0005] According to a first aspect of the present invention, a frequency regulation method for an AC power grid is provided, applied to a full-power converter for connecting a DC power grid to an AC power grid, the method comprising:

[0006] Monitor the grid frequency of the AC power grid, determine the frequency fluctuation range of the AC power grid, and compare the frequency fluctuation range with a first preset fluctuation range, a second preset fluctuation range, and a third preset fluctuation range, wherein the third preset fluctuation range is greater than the second preset fluctuation range, and the second preset fluctuation range is greater than the first preset fluctuation range;

[0007] When the frequency fluctuation range exceeds the first preset fluctuation range but is less than the second preset fluctuation range, the full-power converter is subjected to voltage outer loop current inner loop control based on frequency feedback control to adjust the active power output of the full-power converter and reduce the frequency fluctuation range of the AC grid.

[0008] When the frequency fluctuation range exceeds the third preset fluctuation range, the full-power converter is subjected to voltage outer loop current inner loop control based on frequency feedback control and virtual voltage feedback control to adjust the active power output of the full-power converter and reduce the frequency fluctuation range of the AC grid.

[0009] In an optional embodiment, the voltage outer loop and current inner loop control of the full-power converter based on frequency feedback control includes: acquiring the actual value of the reactive power output of the full-power converter, obtaining a preset reactive power target value, and performing proportional-integral calculation on the reactive power difference between the actual reactive power value and the reactive power target value to obtain the q-axis current target value; acquiring the actual value of the AC grid frequency of the AC grid, obtaining a preset AC grid frequency target value, and determining the frequency response power of the full-power converter based on the frequency difference between the actual AC grid frequency value and the AC grid frequency target value; acquiring the DC voltage value of the DC voltage input to the full-power converter, and the full-power converter... The system obtains the actual active power output of the full-power converter, and acquires preset active power target values ​​and DC voltage target values. Based on the actual active power value, the active power target value, and the frequency response power, it performs active-voltage droop control on the voltage difference between the DC voltage value and the DC voltage target value to obtain the d-axis current target value. It then determines the actual d-axis current value and q-axis current value of the full-power converter's output current, and performs inner-loop current control on the full-power converter based on these values ​​to change the output voltage of the full-power converter, thereby adjusting the active power output of the full-power converter.

[0010] In an optional embodiment, the voltage outer loop and current inner loop control of the full-power converter based on frequency feedback control and virtual voltage feedback control includes: acquiring the actual reactive power output of the full-power converter, obtaining a preset reactive power target value, and performing proportional-integral calculation on the reactive power difference between the actual reactive power value and the reactive power target value to obtain a q-axis current target value; adjusting the reactive power damping of the actual reactive power value to obtain a reactive power damping output signal, and adding the reactive power damping output signal to the q-axis current target value to obtain a corrected q-axis current target value; acquiring the actual AC grid frequency of the AC grid, obtaining a preset AC grid frequency target value, and determining the frequency response power of the full-power converter based on the frequency difference between the actual AC grid frequency and the AC grid frequency target value. The system employs inertial response frequency modulation power; it acquires the DC voltage value input to the full-power converter and the actual value of the active power output of the full-power converter, and obtains preset active power target values ​​and DC voltage target values. Based on the actual active power value, the active power target value, the frequency response power, and the inertial response frequency modulation power, it performs active-voltage droop control on the voltage difference between the DC voltage value and the DC voltage target value to obtain the d-axis current target value; it determines the actual d-axis current value and the actual q-axis current value of the output current of the full-power converter, and performs current inner-loop control on the full-power converter based on the actual d-axis current value, the actual q-axis current value, the d-axis current target value, and the q-axis current target value to change the output voltage of the full-power converter, thereby adjusting the active power output of the full-power converter.

[0011] In an optional embodiment, the current inner-loop control of the full-power converter based on the actual d-axis current value, the actual q-axis current value, the target d-axis current value, and the target q-axis current value includes: acquiring the d-axis output voltage value and the q-axis output voltage value of the full-power converter, and obtaining the angular frequency of the AC grid voltage; calculating the product of the actual d-axis current value, the angular frequency, and the equivalent inductance value of the full-power converter to obtain the d-axis voltage coupling value, and calculating the product of the actual q-axis current value, the angular frequency, and the equivalent inductance value of the full-power converter to obtain the q-axis voltage coupling value; and adjusting the d-axis current target value and the actual q-axis current value... The difference between the actual and d-axis voltage values ​​is adjusted proportionally and integrally to obtain the d-axis voltage reference signal. The sum of the d-axis output voltage value and the q-axis voltage coupling value is subtracted from the d-axis voltage reference signal to obtain the d-axis voltage value. The difference between the target q-axis current value and the actual q-axis current value is adjusted proportionally and integrally to obtain the q-axis voltage reference signal. The difference between the q-axis output voltage value and the d-axis voltage coupling value is subtracted from the q-axis voltage reference signal to obtain the q-axis voltage value. Based on the d-axis voltage value and the q-axis voltage value, the A-phase voltage value, B-phase voltage value, and C-phase voltage value to be output by the full-power converter are determined, and the full-power converter is controlled to output the A-phase voltage value, the B-phase voltage value, and the C-phase voltage value.

[0012] In an optional embodiment, determining the A-phase voltage, B-phase voltage, and C-phase voltage values ​​to be output by the full-power converter based on the d-axis voltage value and the q-axis voltage value includes: determining the angle between the AC voltage and AC current supplied by the AC grid; and based on the angle, performing an inverse transformation on the d-axis voltage value and the q-axis voltage value to obtain the A-phase voltage value, B-phase voltage value, and C-phase voltage value in a three-phase stationary coordinate system.

[0013] In an optional embodiment, the generator in the DC grid is a wind turbine generator, and the full-power converter is a grid-connected converter for connecting the DC grid where the wind turbine generator is located to the AC grid; when the frequency fluctuation range exceeds the third preset fluctuation range, the method further includes: performing active power damping control on the grid-connected converter to adjust the active power output of the grid-connected converter by adjusting the d-axis generation voltage and q-axis generation voltage output by the grid-connected converter, so as to reduce the frequency fluctuation range of the AC grid.

[0014] In an optional embodiment, the active power damping control of the grid-connected converter includes: acquiring the rotor angular frequency setpoint of the wind turbine generator and the reactive power setpoint of the grid-connected converter, and determining the actual rotor angular frequency of the wind turbine generator, the reactive power output of the grid-connected converter, and the active power output; performing proportional-integral adjustment on the difference between the rotor angular frequency setpoint and the actual rotor angular frequency to obtain the d-axis current setpoint, and performing proportional-integral adjustment on the difference between the reactive power setpoint and the reactive power output to obtain the q-axis current setpoint; performing active power damping control on the active power output to obtain an active power damping output signal, and adding the active power damping output signal to the d-axis current setpoint to obtain a corrected d-axis current setpoint; and performing inner-loop current control on the grid-connected converter based on the actual d-axis current, the actual q-axis current, the d-axis current setpoint, and the q-axis current setpoint to adjust the d-axis generation voltage and the q-axis generation voltage output by the grid-connected converter.

[0015] According to a second aspect of the present invention, a frequency regulation device for an AC power grid is provided, the device comprising:

[0016] The fluctuation identification module is used to monitor the grid frequency of the AC power grid, determine the frequency fluctuation range of the AC power grid, and compare the frequency fluctuation range with a first preset fluctuation range, a second preset fluctuation range, and a third preset fluctuation range, wherein the third preset fluctuation range is greater than the second preset fluctuation range, and the second preset fluctuation range is greater than the first preset fluctuation range.

[0017] The first control module is used to perform voltage outer loop and current inner loop control based on frequency feedback control on the full-power converter when the frequency fluctuation range exceeds the first preset fluctuation range and is less than the second preset fluctuation range, so as to adjust the active power output of the full-power converter and reduce the frequency fluctuation range of the AC grid.

[0018] The second control module is used to perform voltage outer loop and current inner loop control on the full-power converter based on frequency feedback control and virtual voltage feedback control when the frequency fluctuation range exceeds the third preset fluctuation range, so as to adjust the active power output of the full-power converter and reduce the frequency fluctuation range of the AC grid.

[0019] According to a third aspect of the present invention, a storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the above-described AC power grid frequency adjustment method.

[0020] According to a fourth aspect of the present invention, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the above-described AC power grid frequency adjustment method.

[0021] This invention provides a frequency adjustment method, apparatus, storage medium, and computer equipment for AC power grids. By introducing a hierarchical control strategy based on frequency fluctuation range in a full-power converter, it effectively improves the frequency stability of wind power grid-connected systems. Specifically, this application achieves adaptive switching of control modes by setting multiple ranges: when the frequency fluctuation of the AC power grid is small, only frequency feedback control is engaged to quickly adjust the active power of the full-power converter and avoid over-response; when the fluctuation intensifies, virtual voltage feedback control is superimposed to enhance dynamic support capabilities and prevent frequency instability of the AC power grid. This hierarchical mechanism balances sensitivity and robustness, overcoming the shortcomings of traditional virtual inertia control, which easily leads to energy overdraft and insufficient droop control adjustment margin. Combined with the voltage outer loop and current inner loop structure, it achieves multi-feedback coordinated regulation, significantly improving the converter's response capability to changes in grid frequency, effectively suppressing large fluctuations in grid frequency, and thus improving the stability of the AC power grid.

[0022] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0024] Figure 1 A flowchart illustrating a frequency adjustment method for an AC power grid provided by an embodiment of the present invention is shown;

[0025] Figure 2 This diagram illustrates the structure of a multi-terminal flexible DC transmission system according to an embodiment of the present invention.

[0026] Figure 3 This diagram illustrates an overall control framework for voltage outer loop and current inner loop control provided by an embodiment of the present invention.

[0027] Figure 4 A logic diagram of a current inner loop control provided by an embodiment of the present invention is shown;

[0028] Figure 5A logic diagram of an active power damping control provided by an embodiment of the present invention is shown;

[0029] Figure 6 This diagram illustrates the frequency of a second active AC system AC2 according to an embodiment of the present invention.

[0030] Figure 7 A voltage schematic diagram of a second rectifier station VSC2 provided in an embodiment of the present invention is shown;

[0031] Figure 8 A schematic diagram of the structure of an AC power grid frequency adjustment device provided in an embodiment of the present invention is shown. Detailed Implementation

[0032] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the present application can be combined with each other.

[0033] Currently, most existing wind turbines use virtual inertia control or droop control to participate in frequency regulation control in order to stabilize the frequency fluctuations of the AC power grid. However, the former is prone to energy overdraft and secondary voltage drops, while the latter is limited by reserve capacity and has limited regulation capabilities. Especially in scenarios where wind power is transmitted over long distances via multi-terminal flexible DC transmission (VSC-MTDC), it may exacerbate the dynamic instability of the AC power grid frequency, resulting in lower stability of the AC power grid.

[0034] To address the above problems, in one embodiment, such as Figure 1 As shown, a frequency regulation method for an AC power grid is provided. Taking the application of this method to a full-power converter as an example, this full-power converter is used to connect a DC power grid to an AC power grid. Further, the method includes the following steps:

[0035] 101. Monitor the grid frequency of the AC power grid, determine the frequency fluctuation range of the AC power grid, and compare the frequency fluctuation range with a first preset fluctuation range, a second preset fluctuation range, and a third preset fluctuation range, wherein the third preset fluctuation range is greater than the second preset fluctuation range, and the second preset fluctuation range is greater than the first preset fluctuation range.

[0036] The first preset fluctuation range can be ±0.05Hz, the second preset fluctuation range can be ±0.5Hz, and the third preset fluctuation range can be ±1Hz. The actual numerical range of the above fluctuation ranges can be determined according to the actual situation. Here, when the frequency fluctuation range is ±0.05Hz, its frequency change level can be determined as level A; when the frequency fluctuation range is ±0.5Hz, its frequency change level is level B; and when the frequency fluctuation range is ±1Hz, its frequency change level is level C.

[0037] Here, the full-power converter can be located within a multi-terminal flexible DC transmission system that includes wind power. For example, Figure 2 As shown, the multi-terminal flexible DC transmission system includes multiple generators, multiple transformers, multiple rectifier stations, and an inverter station. The first generator G1 and the first bus L1 can serve as the first active AC system AC1, which is connected to the first transformer. The second generator G2 and the third bus L3 are connected to the first rectifier station VCS1 via the second bus L2; ​​the second generator G2 and the third bus L3 can serve as the second active AC system AC2, which is connected to the second transformer. The first rectifier station (VCS1) and the second rectifier station (VCS2) are connected to the second rectifier station (VSC3) via the fourth bus (L4). The second rectifier station (VCS1) and the second rectifier station (VCS2) can be connected to the inverter station (VSC3) via the fifth bus (L5). The inverter station (VSC3) is connected to the third transformer. Connected to the sixth bus L6; the sixth bus L6 and the wind turbine G3 can serve as the third active AC system AC3. Here, the fifth bus L5 can be connected to the AC grid (not shown in the figure), and the active AC system is a grid system containing synchronous generators or other components that can provide inertia and voltage support. Furthermore, the first rectifier station VCS1, the second rectifier station VCS2, and the inverter station VSC3 can all have full-power converters, which can serve as the main implementers of this method to stabilize the frequency fluctuation range of the AC grid. Here, the full-power converter can receive the DC power output from the generator, convert it into AC power, and send the AC power to the AC grid.

[0038] Specifically, voltage signals can be acquired in real time using a synchronous phasor measurement unit (PMU) installed in the AC power grid, and the system frequency of the AC power grid can be obtained through signal processing. Further, the difference between the measured system frequency and the preset rated frequency of the power grid is taken as the current AC power grid fluctuation value. The dynamic range of this fluctuation value within a preset time range is the frequency fluctuation range. Furthermore, the frequency fluctuation range can be compared with a first preset fluctuation range, a second preset fluctuation range, and a third preset fluctuation range to determine the numerical relationship between the frequency fluctuation range and each of these preset fluctuation ranges.

[0039] 102. When the frequency fluctuation range exceeds the first preset fluctuation range but is less than the second preset fluctuation range, the full-power converter is subjected to voltage outer loop current inner loop control based on frequency feedback control to adjust the active power output of the full-power converter and reduce the frequency fluctuation range of the AC grid.

[0040] Here, when the frequency fluctuation range exceeds ±0.05Hz but is within ±0.5Hz, the primary frequency regulation function of the full-power converter can be activated first to quickly stabilize the grid frequency. Specifically, firstly, the actual reactive power output of the full-power converter can be collected, and a preset reactive power target value for the full-power converter can be obtained. The reactive power difference between the actual and target values ​​is then proportionally integrated to obtain the q-axis current target value. Alternatively, the three-phase voltage and current at the grid connection point between the full-power converter and the AC grid can be collected in real time. Using instantaneous reactive power theory or dq transformation, the product of the q-axis voltage and current components can be calculated to obtain the actual reactive power value. Furthermore, the q-axis current target value can be calculated using Formula 1.

[0041] (1)

[0042] in, The target value for the q-axis current. This is the target value for reactive power. This represents the actual value of reactive power. as well as The first proportional coefficient and integral coefficient are preset respectively, and 1 / s is the integral operator.

[0043] Then, the actual value of the AC grid frequency is collected at the AC bus of the AC grid, and a preset AC grid frequency target value is obtained. The frequency response power of the full-power converter is determined based on the frequency difference between the actual AC grid frequency and the AC grid frequency target value.

[0044] Here, the three-phase voltage at the grid connection point of the full-power converter can be monitored in real time using a phase-locked loop (PLL), phase information can be extracted, and the phase can be differentiated to obtain the actual value of the AC grid frequency, thereby adjusting the phase of the grid-connected voltage output by the full-power converter. Furthermore, the frequency response power can be calculated using formula 2:

[0045] (2)

[0046] in, For frequency response power, It is the preset frequency modulation coefficient. It is the frequency change of an AC system, i.e., the frequency difference.

[0047] Next, the DC voltage value input from the DC grid to the full-power converter and the actual value of the active power output of the full-power converter are collected. The preset active power target value and DC voltage target value are obtained. Based on the actual active power value, the active power target value, and the frequency response power, active-voltage droop control is performed on the voltage difference between the DC voltage value and the DC voltage target value to obtain the d-axis current target value. The values ​​of the active power target value and the DC voltage target value can be determined according to the actual situation.

[0048] Specifically, the actual active power value can be obtained by measuring the three-phase voltage and output current at the grid connection point of the full-power converter, and then performing dq transformation or instantaneous power theory calculations. Further, the sum of the frequency response power and the target active power value can be calculated, and the actual active power value can be subtracted to obtain the process power value. This process power value is then amplified by a proportional gain of k, yielding the proportionally amplified process power value. The amplification factor can be determined based on the specific circumstances.

[0049] Furthermore, the sum of the process power value and the DC voltage target value is calculated, and the DC voltage value is subtracted from the summation result to obtain the first calculation parameter used to calculate the d-axis current target value. The first calculation parameter is then adjusted by proportional-integral method to obtain the d-axis current target value.

[0050] Here, a voltage outer loop PU droop control for a multi-terminal flexible DC transmission system can also be constructed, as shown in Equation 3. Under steady-state conditions, the relationship between the DC voltage and active power of the converter station is:

[0051] (3)

[0052] in, The target value for DC voltage. The preset droop coefficient, The target value for active power. This represents the actual value of active power. This is the DC voltage value.

[0053] Furthermore, after incorporating frequency feedback control, the first calculation parameter can be calculated based on Formula 4:

[0054] (4)

[0055] in, The target value for DC voltage. The preset droop coefficient, The target value for active power. This represents the actual value of active power. This is the DC voltage value. As the first calculation parameter, This represents the frequency response power. Furthermore, combining Equation 2, Equation 4 can be transformed into Equation 5:

[0056] (5)

[0057] in, The target value for DC voltage. The preset droop coefficient, The target value for active power. This represents the actual value of active power. This is the DC voltage value. As the first calculation parameter, It is the preset frequency modulation coefficient. This is the frequency difference. Based on this, the first calculation parameter can be calculated according to Formula 5, and the first calculation parameter can be adjusted by proportional-integral adjustment to obtain the target value of the d-axis current.

[0058] Finally, the actual values ​​of the d-axis current and q-axis current of the output current of the full-power converter are determined. Based on the actual values ​​of the d-axis current, the actual values ​​of the q-axis current, the target values ​​of the d-axis current, and the target values ​​of the q-axis current, the inner loop current control of the full-power converter is performed to change the amplitude of the voltage output by the full-power converter, thereby adjusting the active power output by the full-power converter and rapidly reducing the frequency fluctuation range to stabilize the AC grid frequency.

[0059] Furthermore, the frequency fluctuation range of the AC power grid can be monitored in real time. When the frequency fluctuation range no longer increases, reactive power damping control can be added to the active power-voltage droop control. Specifically, in the process of calculating the target value of the q-axis current, the reactive power at the grid connection point of the AC bus of the AC power grid to which the generator is connected is collected. The generator is connected to the AC power grid through this AC bus.

[0060] Furthermore, the reactive power damping output signal is calculated based on Formula 6:

[0061] (6)

[0062] in, This is the reactive damping output signal. The reactive power at the grid connection point, Ts is the preset second proportional coefficient, Ts is the DC isolation time constant, and Ts1, Ts2, Ts3, and Ts4 are the time constants of the time advance and lag compensation links.

[0063] Furthermore, after obtaining the reactive power damping output signal, the reactive power damping output signal is added to the q-axis current target value obtained in Formula 1 to obtain the corrected q-axis current target value. Based on the q-axis current target value, it participates in the current inner loop control environment to add reactive power damping control function to the voltage outer loop current inner loop control process based on frequency feedback control. Furthermore, when the frequency fluctuation range falls back to within ±0.1Hz, the primary frequency regulation function of frequency feedback control is exited, and the DC additional reactive power damping control function is used to quickly suppress frequency oscillation.

[0064] Furthermore, when the frequency fluctuation range is within ±0.05Hz, only the voltage outer loop and current inner loop control based on frequency feedback control can be performed on the full-power converter, and other additional control functions are not activated.

[0065] 103. When the frequency fluctuation range exceeds the third preset fluctuation range, the full-power converter is subjected to voltage outer loop current inner loop control based on frequency feedback control and virtual voltage feedback control, so as to adjust the active power output of the full-power converter and reduce the frequency fluctuation range of the AC grid.

[0066] Specifically, firstly, the actual reactive power output of the full-power converter is collected, and a preset reactive power target value is obtained. Then, the reactive power difference between the actual reactive power value and the reactive power target value is calculated by proportional integration to obtain the q-axis current target value. Here, the q-axis current target value can also be calculated using the above formula 1.

[0067] Then, reactive power damping is adjusted on the actual value of reactive power to obtain a reactive power damping output signal, and the reactive power damping output signal is added to the target value of q-axis current to obtain the corrected target value of q-axis current; here, the reactive power damping output signal can be calculated by the above formula 6.

[0068] Next, the actual AC grid frequency is collected at the AC bus of the AC grid, and a target AC grid frequency value preset for the output voltage is obtained. Based on the frequency difference between the actual AC grid frequency and the target AC grid frequency, the frequency response power and inertia response frequency modulation power of the full-power converter are determined. Here, the actual AC grid frequency can be the grid frequency of the AC grid. Furthermore, the frequency response power can be calculated based on Formula 2. Furthermore, the inertia response frequency modulation power can be calculated using Formula 7.

[0069] (7)

[0070] in, For inertial response frequency modulation power, The preset inertia coefficient, t represents the frequency difference, and t represents time.

[0071] Next, the DC voltage value input to the full-power converter and the actual value of the active power output by the full-power converter are collected, and a preset active power target value and a preset DC voltage target value for the DC voltage of the full-power converter are obtained. Based on the actual active power value, the active power target value, the frequency response power and the inertia response frequency modulation power, active power-voltage droop control is performed on the voltage difference between the DC voltage value and the DC voltage target value to obtain the d-axis current target value.

[0072] Here, the inertial response frequency modulation power can be added to the frequency response power to obtain the sum of inertial frequency feedback; further, the sum of inertial frequency feedback can be added to the active power target value, and the actual active power value can be subtracted from the sum to obtain the process power value. The process power value is then amplified by a proportional gain of k to obtain the proportionally amplified process power value.

[0073] Furthermore, the sum of the process power value and the DC voltage target value is calculated, and the DC voltage value is subtracted from the summation result to obtain the second calculation parameter used to calculate the d-axis current target value. The second calculation parameter is then adjusted proportionally and integrally to obtain the d-axis current target value.

[0074] Here, a voltage outer loop PU droop control for a multi-terminal flexible DC transmission system can also be constructed. After incorporating frequency feedback control and virtual voltage feedback control into Equation 3 above, the second calculation parameter can be calculated based on Equation 8:

[0075] (8)

[0076] in, The target value for DC voltage. The preset droop coefficient, The target value for active power. This represents the actual value of active power. This is the DC voltage value. This is the second calculation parameter. For frequency response power, This represents the frequency modulation power of the inertial response. Furthermore, combining formulas 2 and 7 above, formula 8 can be transformed into formula 9:

[0077] (9)

[0078] in, The target value for DC voltage. The preset droop coefficient, The target value for active power. This represents the actual value of active power. This is the DC voltage value. This is the second calculation parameter. It is the preset frequency modulation coefficient. It is the frequency difference. The preset inertia coefficient, This represents the frequency difference. Based on this, the second calculation parameter can be calculated according to Formula 9, and the second calculation parameter can be adjusted using proportional-integral methods to obtain the target value of the d-axis current.

[0079] Finally, the actual values ​​of the d-axis current and q-axis current of the full-power converter are determined. Further, based on the actual values ​​of the d-axis current, the actual values ​​of the q-axis current, the target values ​​of the d-axis current, and the target values ​​of the q-axis current, current inner-loop control is performed on the full-power converter to change the output voltage of the full-power converter, thereby adjusting the active power output of the full-power converter.

[0080] Here, the frequency fluctuation range of the AC power grid can be monitored in real time. When the frequency fluctuation range falls back to within ±0.5Hz, the virtual voltage feedback control process is stopped, i.e., the process described in Formula 7... Set to zero, or set the value in formula 9 to zero. Set the value to zero to stop the virtual voltage feedback control process. Furthermore, when the frequency fluctuation range falls back to within ±0.1Hz, stop the frequency feedback control, i.e., the frequency response power in Equation 2. Set to zero, or set the value in formula 5 to zero. Set to zero to stop frequency feedback control. Here, the overall control framework diagram of the voltage outer loop and current inner loop control can be shown as follows: Figure 3 As shown.

[0081] The AC grid frequency adjustment method provided in this embodiment adjusts the amplitude and phase of the grid-connected voltage output by the full-power converter, thereby changing the amplitude difference and phase angle difference between the converter and the grid voltage, and thus regulating the output active power. According to power transmission characteristics, active power is mainly affected by voltage phase difference. When the grid frequency fluctuates, the converter is controlled to quickly adjust its output d-axis voltage component, changing the magnitude and direction of its output active power, injecting or absorbing power into the grid, simulating inertial response and primary frequency regulation, offsetting unbalanced power from load or generation, and thus suppressing the rate of frequency change and steady-state deviation, achieving active suppression of grid frequency fluctuations. In actual operation, introducing a hierarchical control strategy based on frequency fluctuations into the full-power converter can effectively improve the frequency stability of the wind power grid-connected system. By setting multiple ranges, adaptive switching of control modes is achieved. When there are small disturbances in the grid frequency, only frequency feedback control is engaged to quickly adjust the active power of the full-power converter and avoid over-response; while during large disturbances, virtual voltage feedback control is superimposed to enhance dynamic support and prevent frequency instability. This hierarchical mechanism balances response sensitivity and control robustness, effectively overcoming the problems of energy overdraft in traditional virtual inertia control and insufficient regulation capability in droop control. Simultaneously, by combining an outer voltage loop and an inner current loop structure, it achieves multi-feedback coordination, enhancing the converter's adaptability to frequency changes and significantly suppressing large frequency fluctuations in the AC power grid, thereby improving the operational stability of the AC power grid.

[0082] In an optional embodiment, the method of performing inner-loop current control on the full-power converter based on the actual value of the d-axis current, the actual value of the q-axis current, the target value of the d-axis current, and the target value of the q-axis current in step 102 or 103 includes:

[0083] First, such as Figure 4 As shown, the d-axis output voltage value of the full-power converter is collected. and q-axis output voltage value The angular frequency ω of the AC grid voltage is obtained. Specifically, the three-phase grid voltage at the full-power converter connection point can be tracked in real time using a phase-locked loop (PLL) to obtain the rotation angle of the synchronous rotating coordinate system. This angle is then used to perform a dq transformation on the three-phase output voltage, thereby decoupling and obtaining the d-axis output voltage value. and q-axis output voltage value Meanwhile, the angular frequency ω output by the PLL is the real-time angular frequency of the grid voltage, which is used for frequency feedback control.

[0084] Then, calculate the actual value of the d-axis current. The d-axis voltage coupling value is obtained by multiplying the angular frequency ω and the equivalent inductance L of the full-power converter, and the actual value of the q-axis current is calculated. The q-axis voltage coupling value is obtained by multiplying the angular frequency ω and the equivalent inductance L of the full-power converter; where the equivalent inductance L of the full-power converter refers to the sum of its output filter inductance and line inductance, used to reflect electromagnetic inertia when the current changes. Specifically, the actual value of the d-axis current is... Multiplying by the angular frequency ω and the equivalent inductance L, we obtain the d-axis voltage coupling value; similarly, we obtain the actual q-axis current value. Multiply by the angular frequency ω and the equivalent inductance L to obtain the q-axis voltage coupling value.

[0085] Next, the target value of the d-axis current... Compared with the actual value of the d-axis current The difference is used for proportional-integral adjustment to obtain the d-axis voltage reference signal, and the d-axis output voltage value is calculated. The sum of the q-axis voltage coupling values, minus the d-axis voltage reference signal, yields the d-axis voltage value. ;

[0086] Next, the target value of the q-axis current... Compared with the actual value of the q-axis current The difference is used for proportional-integral adjustment to obtain the q-axis voltage reference signal, and the q-axis output voltage value is calculated. The difference between the d-axis voltage coupling value and the q-axis voltage reference signal is used to obtain the q-axis voltage value. ;

[0087] Finally, based on the d-axis voltage value With the q-axis voltage value Determine the voltage values ​​of phase A, phase B, and phase C, and control the full-power converter to output the voltage values ​​of phase A, phase B, and phase C.

[0088] Specifically, it can collect the three-phase AC voltage of the AC power grid. And the three-phase alternating current, and determine the angle between the alternating voltage and alternating current of the AC power grid; here, the alternating voltage It can be the grid voltage of an AC power grid; further, based on the included angle, the voltage value along the d-axis... With the q-axis voltage value By performing the inverse transformation, the voltage value of phase A in the three-phase stationary coordinate system is obtained. The voltage value of phase B and the C-phase voltage value To enable the full-power converter to output phase A voltage to the AC grid. Phase B voltage value and C-phase voltage value .

[0089] Here, the d-axis voltage value can be determined using the mathematical model expression in the dq synchronous rotating coordinate system, i.e., Formula 10. and q-axis voltage value :

[0090] (10)

[0091] in, This represents the actual value of the d-axis current. Let ω be the actual value of the q-axis current, L be the equivalent inductance of the full-power converter, t be time, R be the equivalent resistance of the full-power converter, and ω be the real-time angular frequency of the AC grid voltage. and These are the preset coefficients for the direct-axis voltage and quadrature-axis voltage, respectively. This represents the d-axis voltage value. This represents the q-axis voltage value; here, the magnitude of the dq-axis current is easily affected by the system voltage and coupling. as well as It can be used as a coupling term in mathematical model expressions.

[0092] Furthermore, regarding , To achieve decoupling control, the grid-side dq-axis current is introduced in equation (10) to eliminate system voltage disturbances. A first intermediate variable Ud and a second intermediate variable Uq are introduced, as shown in equations 11 and 12:

[0093] (11)

[0094] (12)

[0095] in, This represents the actual value of the d-axis current. Let L be the actual value of the q-axis current, L be the equivalent inductance of the full-power converter, R be the equivalent resistance of the full-power converter, and t be time. Furthermore, substituting Equations 11 and 12 into Equation 10, and introducing the grid-side dq-axis current into Equation 10 to eliminate system voltage disturbances, we obtain Equation 13:

[0096] (13)

[0097] Furthermore, Formula 13 can be adjusted to Formula 14:

[0098] (14)

[0099] in, This represents the actual value of the d-axis current. Ud is the actual value of the q-axis current, L is the equivalent inductance of the full-power converter, R is the equivalent resistance of the full-power converter, t is time, Ud is the first intermediate variable, and Uq is the second intermediate variable. The target value for the d-axis current. This represents the d-axis voltage value. Let ω be the q-axis voltage value, and ω be the real-time angular frequency of the AC grid voltage. These are the preset direct-axis integral coefficients. These are the preset cross-axis integral coefficients. This is the preset direct axis scaling factor. This is the preset cross-axis scaling factor. The d-axis voltage value can be calculated using formula 14. and q-axis voltage value .

[0100] The embodiments provided in this application effectively improve the dynamic response accuracy and stability of a full-power converter by introducing dq-axis current decoupling control. By real-time acquisition of d- and q-axis voltages and compensation for coupling terms, cross-coupling interference in coordinate transformation is suppressed, enhancing the control robustness of the inner current loop. Furthermore, three-phase voltage signals are generated through dq / abc inverse transformation to precisely control the converter output voltage. This method significantly improves the response speed and steady-state accuracy of current control, effectively suppresses the impact of grid disturbances, and enhances the power quality and operational reliability of grid-connected systems for wind power and other new energy sources.

[0101] In an optional embodiment, the generator in the DC grid is a wind turbine generator, and the full-power converter is a grid-connected converter used to connect the DC grid where the wind turbine generator is located to the AC grid. When the frequency fluctuation range is greater than the third preset fluctuation range, that is, when the frequency fluctuation range is greater than ±1Hz, in order to fully utilize the damping control function of the wind farm and improve the stability of the grid-connected system, an additional active power damping controller for the wind farm can be constructed to perform active power damping control on the grid-connected converter, so as to adjust the d-axis generation voltage and q-axis generation voltage output by the grid-connected converter, thereby reducing the frequency fluctuation range of the AC grid by adjusting the active power output of the grid-connected converter connected to the wind turbine generator.

[0102] Here, the wind turbine can be set to operate under overspeed and load reduction conditions. The power of the wind turbine in maximum power point tracking (MPPT) mode and the power in load reduction mode can be set using formulas 15 and 16, respectively.

[0103] (15)

[0104] (16)

[0105] in, This refers to the power under maximum power point tracking (MPPT) conditions. Power under unload conditions. For wind turbine load reduction rate; ωr is the maximum power point tracking factor; ωr is the rotor speed of the wind turbine.

[0106] Specifically, the method for active power damping control of the grid-connected converter includes:

[0107] First, such as Figure 5 As shown, the preset rotor angular frequency setting value for the DFIG wind turbine is obtained. and reactive power setpoint And determine the actual value of the current rotor angular frequency of the DFIG wind turbine. It also collects the reactive power output value of the grid-connected converter. And the active power value P.

[0108] Then, the rotor angular frequency setting value is... Compared with the actual value of the rotor angular frequency The difference is adjusted using a proportional-integral method to obtain the d-axis current setpoint. and the reactive power setpoint With the aforementioned reactive power value The difference is adjusted using proportional-integral methods to obtain the q-axis current setpoint. ;

[0109] Next, active power value P is subjected to active damping control to obtain an active damping output signal. and the active damping output signal With the d-axis current setting value Adding them together, we obtain the corrected d-axis current setting value. The grid-connected converter is intended to have an additional active power damping function.

[0110] Here, the active damping output signal can be calculated according to Formula 17:

[0111] (17)

[0112] in, This is the active power damping output signal, where P is the active power value. This is a preset proportional coefficient. The DC blocking time constant, , , , This is the time constant for the time lead-lag compensation process.

[0113] Finally, based on the d-axis voltage value output by the grid-connected converter and q-axis voltage value The actual value of the d-axis current The actual value of the q-axis current The d-axis current setting value and the q-axis current setting value The grid-connected converter is subjected to inner-loop current control to determine the d-axis generating voltage to be output by the converter. and q-axis generation voltage It also sends control commands to the grid-connected converter to control the converter to output d-axis generating voltage to the AC grid. and q-axis generation voltage Here, the current inner loop control method can be referenced. Figure 4 The current inner loop control method shown is not described in detail here.

[0114] Here, the frequency fluctuation range of the AC power grid can be monitored in real time. When the frequency fluctuation range falls back to within ±0.5Hz, the virtual voltage feedback control process is stopped, and the active power damping control of the grid-connected converter is also stopped, i.e., the... (The sentence is incomplete and requires more context to translate accurately). Set to zero, or set the value in formula 9 to zero. The voltage feedback control process is stopped by setting the output signal to zero. Simultaneously, the active power damping output signal is also set to zero to stop active power damping control of the grid-connected converter. Furthermore, when the frequency fluctuation range falls back to within ±0.1Hz, frequency feedback control is stopped, i.e., the frequency response power in Equation 2 is... Set to zero, or set the value in formula 5 to zero. Set to zero to stop frequency feedback control.

[0115] The embodiments provided in this application effectively improve the dynamic stability of wind power systems by constructing an additional active power damping controller for wind farms and combining it with overspeed load shedding operation. When frequency fluctuations are excessive, active power damping control is activated, utilizing active power feedback to suppress power oscillations, enhancing system damping, improving the adaptability of wind turbine units to grid disturbances, fully exploring their active support potential, and significantly improving the frequency stability and disturbance rejection capability of high-penetration wind power grid-connected systems.

[0116] In actual use, when the frequency fluctuation range of the AC power grid is within ±0.05Hz, only the primary frequency regulation function of the multi-terminal flexible DC converter station is activated to perform voltage outer loop and current inner loop control based on frequency feedback control on the full-power converter. Other additional control functions are not activated.

[0117] Furthermore, when the frequency fluctuation range of the AC power grid exceeds ±0.05Hz but is within ±0.5Hz, the primary frequency regulation function of the multi-terminal flexible DC converter station is first activated to quickly stabilize the power grid frequency. Then, the reactive power damping control function is activated. When the power grid frequency is detected to fall back to within ±0.1Hz, the primary frequency regulation function of the multi-terminal flexible DC converter station is deactivated, and the reactive power damping control function is used to quickly suppress the frequency oscillation.

[0118] Furthermore, when the grid frequency fluctuation exceeds ±1Hz, voltage outer loop and current inner loop control based on frequency feedback control and virtual voltage feedback control are activated, along with reactive power damping control and wind turbine additional active power damping function. When the grid frequency is detected to have fallen back to within ±0.5Hz, virtual voltage feedback control and wind turbine active power damping function are stopped. When the AC grid frequency falls back to within ±0.1Hz, frequency feedback control is stopped, and only the DC additional reactive power damping control function continues to operate until the grid frequency returns to stability.

[0119] Furthermore, in combination Figure 2 The effectiveness of this method will be explained. Figure 2 To build a simulation model of a multi-terminal flexible DC transmission system including wind power in PSCAD / EMTDC, as shown in the figure, AC1, AC2, and AC3 are all active AC systems, VSC1 and VSC2 are rectifier stations, and VSC3 is an inverter station. VSC1 and VSC3 employ droop control strategies, while VSC2 uses constant power control. At 2.5s, the power command value of VSC2 decreases from 40MW to 20MW. The simulation comparison results are shown below. Figure 6 The frequency diagram of the second active AC system AC2 shown is as follows: Figure 7 The diagram shows the voltage of the second rectifier station VSC2. It is evident that the method proposed in this invention effectively reduces frequency deviation compared to traditional control methods. This demonstrates that the additional control frequency modulation effect is better, the active power provided by the DC capacitor is smaller, effectively reducing voltage deviation and avoiding the risk of voltage exceeding limits, thus proving the effectiveness of the method proposed in this invention.

[0120] The frequency adjustment method for AC power grids provided in this embodiment introduces a graded collaborative control strategy based on frequency fluctuations in full-power converters, significantly improving the frequency stability of wind power grid-connected systems. By setting multi-level fluctuation thresholds, adaptive switching of control modes is achieved: for small disturbances, only frequency feedback control is engaged to quickly adjust active power and avoid excessive energy consumption; for large disturbances, virtual voltage feedback control is superimposed to enhance dynamic support capabilities and prevent frequency instability. This graded mechanism balances response sensitivity and control robustness, effectively overcoming the shortcomings of traditional virtual inertia control, such as easy energy overdraft and insufficient adjustment margin of droop control. Combining the voltage outer loop and current inner loop structure, frequency and voltage feedback are integrated to achieve multi-dimensional collaborative adjustment. At the same time, by coordinating with wind turbine overspeed load reduction, additional active power damping control, and flexible DC systems, a comprehensive response mechanism with multiple time scales and spatial dimensions is formed. This not only improves the converter's adaptability to frequency changes but also effectively suppresses low-frequency oscillations and large frequency fluctuations, comprehensively enhancing the dynamic stability and operational safety of AC power grids in high-penetration wind power scenarios.

[0121] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties. In addition, the labels corresponding to each step in the above embodiments are only for identification purposes and are not intended to limit the execution order of the steps. The execution order of the steps in each embodiment can be set according to the actual situation.

[0122] Furthermore, as Figure 1 The specific implementation of the method shown in this embodiment provides a frequency adjustment device for an AC power grid, such as... Figure 8 As shown, the device includes: a wave recognition module 81, a first control module 82, and a second control module 83.

[0123] The fluctuation identification module 81 can be used to monitor the grid frequency of the AC power grid, determine the frequency fluctuation range of the AC power grid, and compare the frequency fluctuation range with a first preset fluctuation range, a second preset fluctuation range, and a third preset fluctuation range, wherein the third preset fluctuation range is greater than the second preset fluctuation range, and the second preset fluctuation range is greater than the first preset fluctuation range.

[0124] The first control module 82 can be used to perform voltage outer loop and current inner loop control based on frequency feedback control on the full-power converter when the frequency fluctuation range exceeds the first preset fluctuation range and is less than the second preset fluctuation range, so as to adjust the active power output by the full-power converter and reduce the frequency fluctuation range of the AC grid.

[0125] The second control module 83 can be used to perform voltage outer loop and current inner loop control on the full-power converter based on frequency feedback control and virtual voltage feedback control when the frequency fluctuation range exceeds the third preset fluctuation range, so as to adjust the active power output of the full-power converter and reduce the frequency fluctuation range of the AC grid.

[0126] In specific application scenarios, the first control module 82 can be used to collect the actual value of reactive power output by the full-power converter, obtain a preset reactive power target value, and perform proportional-integral calculation on the reactive power difference between the actual reactive power value and the reactive power target value to obtain the q-axis current target value; collect the actual value of the AC grid frequency of the AC grid, obtain a preset AC grid frequency target value, and determine the frequency response power of the full-power converter based on the frequency difference between the actual AC grid frequency value and the AC grid frequency target value; collect the DC voltage value input to the full-power converter and the active power output by the full-power converter. The system obtains the actual value of the active power and the target value of the DC voltage, and performs active-voltage droop control on the voltage difference between the DC voltage and the target value based on the actual value of the active power, the target value of the active power, and the frequency response power to obtain the target value of the d-axis current. It also determines the actual value of the d-axis current and the actual value of the q-axis current of the full-power converter, and performs inner-loop current control on the full-power converter based on these values ​​to change the output voltage of the full-power converter, thereby adjusting the active power output of the full-power converter.

[0127] In specific application scenarios, the second control module 83 can be used to collect the actual reactive power output of the full-power converter, obtain a preset reactive power target value, and perform proportional-integral calculation on the reactive power difference between the actual reactive power value and the reactive power target value to obtain the q-axis current target value; adjust the reactive power damping of the actual reactive power value to obtain a reactive power damping output signal, and add the reactive power damping output signal to the q-axis current target value to obtain the corrected q-axis current target value; collect the actual AC bus frequency of the AC bus, obtain a preset AC grid frequency target value, and determine the frequency response power and inertia response frequency modulation power of the full-power converter based on the frequency difference between the actual AC grid frequency and the AC grid frequency target value; and collect the input to the... The DC voltage value of the full-power converter and the actual value of the active power output of the full-power converter are obtained, and preset active power target value and DC voltage target value are acquired. Based on the actual active power value, the active power target value, the frequency response power, and the inertia response frequency modulation power, active power-voltage droop control is performed on the voltage difference between the DC voltage value and the DC voltage target value to obtain the d-axis current target value. The actual d-axis current value and the actual q-axis current value of the output current of the full-power converter are determined, and based on the actual d-axis current value, the actual q-axis current value, the d-axis current target value, and the q-axis current target value, the inner current loop control of the full-power converter is performed to change the output voltage of the full-power converter, thereby adjusting the active power output of the full-power converter.

[0128] In specific application scenarios, the first control module 82 and the second control module 83 can be used to acquire the d-axis output voltage value and q-axis output voltage value of the full-power converter, respectively, and obtain the angular frequency of the grid voltage; calculate the product of the actual d-axis current value, the angular frequency, and the equivalent inductance value of the full-power converter to obtain the d-axis voltage coupling value, and calculate the product of the actual q-axis current value, the angular frequency, and the equivalent inductance value of the full-power converter to obtain the q-axis voltage coupling value; perform proportional-integral adjustment on the difference between the target d-axis current value and the actual d-axis current value to obtain the d-axis voltage reference signal. The d-axis voltage value is obtained by subtracting the d-axis voltage reference signal from the sum of the d-axis output voltage value and the q-axis voltage coupling value. The difference between the target q-axis current value and the actual q-axis current value is adjusted proportionally and integrally to obtain the q-axis voltage reference signal. The q-axis voltage value is then obtained by subtracting the q-axis voltage reference signal from the difference between the q-axis output voltage value and the d-axis voltage coupling value. Based on the d-axis voltage value and the q-axis voltage value, the A-phase voltage value, B-phase voltage value, and C-phase voltage value to be output by the full-power converter are determined, and the full-power converter is controlled to output the A-phase voltage value, the B-phase voltage value, and the C-phase voltage value.

[0129] In specific application scenarios, the first control module 82 and the second control module 83 can be used to determine the angle between the AC voltage and AC current transmitted by the AC power grid; based on the angle, the d-axis voltage value and the q-axis voltage value are inversely transformed to obtain the A-phase voltage value, the B-phase voltage value and the C-phase voltage value in the three-phase stationary coordinate system.

[0130] In a specific application scenario, the generator in the DC grid is a wind turbine generator, and the full-power converter is a grid-connected converter used to connect the DC grid where the wind turbine generator is located to the AC grid. The second control module 83 can be used to perform active power damping control on the grid-connected converter, so as to adjust the active power output of the grid-connected converter by adjusting the d-axis generation voltage and q-axis generation voltage output by the grid-connected converter, thereby reducing the frequency fluctuation range of the AC grid.

[0131] In a specific application scenario, the second control module 83 can be used to acquire the rotor angular frequency setpoint and reactive power setpoint of the wind turbine generator, and determine the actual rotor angular frequency of the wind turbine generator, the reactive power value and the active power value output by the grid-connected converter; perform proportional-integral adjustment on the difference between the rotor angular frequency setpoint and the actual rotor angular frequency to obtain the d-axis current setpoint, and perform proportional-integral adjustment on the difference between the reactive power setpoint and the reactive power value to obtain the q-axis current setpoint; perform active damping control on the active power value to obtain an active damping output signal, and add the active damping output signal to the d-axis current setpoint to obtain the corrected d-axis current setpoint; and perform inner-loop current control on the grid-connected converter based on the actual d-axis current value, the actual q-axis current value, the d-axis current setpoint, and the q-axis current setpoint to adjust the d-axis generating voltage and the q-axis generating voltage output by the grid-connected converter.

[0132] It should be noted that other corresponding descriptions of the functional units involved in the AC power grid frequency adjustment device provided in this embodiment can be found in [reference]. Figure 1 The corresponding descriptions in [the document] will not be repeated here.

[0133] Based on the above, Figure 1 Accordingly, this embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements the above-described method. Figure 1 The frequency adjustment method for the AC power grid is shown.

[0134] Based on this understanding, the technical solution of this application can be embodied in the form of a software product. The software product to be identified can be stored in a non-volatile storage medium (such as a CD-ROM, USB flash drive, mobile hard drive, etc.) and includes several instructions to cause a computer device (such as a personal computer, server, or network device, etc.) to execute the methods described in the various implementation scenarios of this application.

[0135] Based on the above, Figure 1 The method shown, and Figure 8 The embodiment of the AC power grid frequency adjustment device shown herein, in order to achieve the above objectives, also provides a computer device for AC power grid frequency adjustment, specifically a personal computer, server, smartphone, tablet computer, smartwatch, or other network device, etc. This computer device includes a storage medium and a processor; the storage medium is used to store computer programs and an operating system; the processor is used to execute the computer program to achieve the above-described... Figures 1 to 4 The method shown.

[0136] Optionally, the computer device may also include internal memory, a communication interface, a network interface, a camera, radio frequency (RF) circuitry, sensors, audio circuitry, a Wi-Fi module, a display screen, and input devices such as a keyboard. The communication interface may also include a USB interface, a card reader interface, etc. The network interface may optionally include a standard wired interface or a wireless interface (such as a Wi-Fi interface).

[0137] Those skilled in the art will understand that the computer device structure for recognizing operational actions provided in this embodiment does not constitute a limitation on the computer device, and may include more or fewer components, or combine certain components, or have different component arrangements.

[0138] The storage medium may also include an operating system and a network communication module. The operating system is a program that manages the aforementioned computer hardware and the software resources to be identified, supporting the operation of information processing programs and other software and / or programs to be identified. The network communication module is used to enable communication between the various components within the storage medium, as well as communication with other hardware and software in the information processing computer device.

[0139] Through the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented using software plus necessary general-purpose hardware platforms, or it can be implemented in hardware. By applying the technical solution of this application, firstly, the grid voltage of the AC power grid is monitored, and the frequency fluctuation range of the grid voltage is determined. This frequency fluctuation range is then compared with a first preset fluctuation range, a second preset fluctuation range, and a third preset fluctuation range, wherein the third preset fluctuation range is greater than the second preset fluctuation range, and the second preset fluctuation range is greater than the first preset fluctuation range. Then, when the frequency fluctuation range exceeds the first preset fluctuation range but is less than the second preset fluctuation range, voltage outer loop and current inner loop control based on frequency feedback control is applied to the full-power converter to adjust the active power output of the full-power converter and reduce the frequency fluctuation range of the AC power grid voltage. Next, when the frequency fluctuation range exceeds the third preset fluctuation range, voltage outer loop and current inner loop control based on frequency feedback control and virtual voltage feedback control is applied to the full-power converter to adjust the active power output of the full-power converter and reduce the frequency fluctuation range of the AC power grid voltage. Compared with the prior art, this improves the stability of the AC power grid.

[0140] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing this application. Those skilled in the art will understand that the modules in the apparatus of the embodiment can be distributed within the apparatus of the embodiment as described, or can be modified to be located in one or more apparatuses different from this embodiment. The modules of the above-described embodiment can be combined into one module, or further divided into multiple sub-modules.

[0141] The serial numbers in this application are for descriptive purposes only and do not represent the superiority or inferiority of any particular implementation scenario. The above disclosures are merely a few specific implementation scenarios of this application; however, this application is not limited thereto, and any variations conceived by those skilled in the art should fall within the protection scope of this application.

Claims

1. A frequency regulation method for an AC power grid, applied to a full-power converter, the full-power converter being used to connect a DC power grid to an AC power grid, characterized in that, The method includes: Monitor the grid frequency of the AC power grid, determine the frequency fluctuation range of the AC power grid, and compare the frequency fluctuation range with a first preset fluctuation range, a second preset fluctuation range, and a third preset fluctuation range, wherein the third preset fluctuation range is greater than the second preset fluctuation range, and the second preset fluctuation range is greater than the first preset fluctuation range; When the frequency fluctuation range exceeds the first preset fluctuation range but is less than the second preset fluctuation range, the full-power converter is subjected to voltage outer loop current inner loop control based on frequency feedback control to adjust the active power output of the full-power converter and reduce the frequency fluctuation range of the AC grid. When the frequency fluctuation range exceeds the third preset fluctuation range, the full-power converter is subjected to voltage outer loop current inner loop control based on frequency feedback control and virtual voltage feedback control to adjust the active power output of the full-power converter and reduce the frequency fluctuation range of the AC grid. The voltage outer loop and current inner loop control based on frequency feedback control of the full-power converter includes: The actual reactive power output of the full-power converter is collected, and a preset reactive power target value is obtained. The reactive power difference between the actual reactive power value and the reactive power target value is calculated by proportional integration to obtain the q-axis current target value. The actual value of the AC grid frequency of the AC grid is collected, and a preset target value of the AC grid frequency is obtained. The frequency response power of the full-power converter is determined based on the frequency difference between the actual value of the AC grid frequency and the target value of the AC grid frequency. The DC voltage value input to the full-power converter and the actual value of the active power output by the full-power converter are collected. A preset active power target value and DC voltage target value are obtained. Based on the actual active power value, the active power target value, and the frequency response power, active power-voltage droop control is performed on the voltage difference between the DC voltage value and the DC voltage target value to obtain the d-axis current target value. The actual values ​​of the d-axis current and q-axis current of the output current of the full-power converter are determined, and the current inner loop control of the full-power converter is performed based on the actual values ​​of the d-axis current, the actual values ​​of the q-axis current, the target values ​​of the d-axis current, and the target values ​​of the q-axis current to change the voltage output of the full-power converter, thereby adjusting the active power output of the full-power converter.

2. The method according to claim 1, characterized in that, The voltage outer loop and current inner loop control of the full-power converter based on frequency feedback control and virtual voltage feedback control includes: The actual reactive power output of the full-power converter is collected, and a preset reactive power target value is obtained. The reactive power difference between the actual reactive power value and the reactive power target value is calculated by proportional integration to obtain the q-axis current target value. The reactive power actual value is adjusted by reactive power damping to obtain a reactive power damping output signal, and the reactive power damping output signal is added to the q-axis current target value to obtain the corrected q-axis current target value. The actual value of the AC grid frequency of the AC grid is collected, and a preset AC grid frequency target value is obtained. Based on the frequency difference between the actual value of the AC grid frequency and the AC grid frequency target value, the frequency response power and inertia response frequency modulation power of the full-power converter are determined. The DC voltage value input to the full-power converter and the actual value of the active power output by the full-power converter are collected. A preset target value of active power and target value of DC voltage are obtained. Based on the actual value of active power, the target value of active power, the frequency response power and the inertia response frequency modulation power, active power-voltage droop control is performed on the voltage difference between the DC voltage value and the target value of DC voltage to obtain the target value of d-axis current. The actual values ​​of the d-axis current and q-axis current of the output current of the full-power converter are determined, and the current inner loop control of the full-power converter is performed based on the actual values ​​of the d-axis current, the actual values ​​of the q-axis current, the target values ​​of the d-axis current, and the target values ​​of the q-axis current to change the voltage output of the full-power converter, thereby adjusting the active power output of the full-power converter.

3. The method according to claim 2, characterized in that, The current inner-loop control of the full-power converter based on the actual value of the d-axis current, the actual value of the q-axis current, the target value of the d-axis current, and the target value of the q-axis current includes: The d-axis and q-axis output voltage values ​​of the full-power converter are collected, and the angular frequency of the AC grid voltage is obtained. The d-axis voltage coupling value is obtained by multiplying the actual value of the d-axis current, the angular frequency, and the equivalent inductance value of the full-power converter. The q-axis voltage coupling value is also obtained by multiplying the actual value of the q-axis current, the angular frequency, and the equivalent inductance value of the full-power converter. The difference between the target value of the d-axis current and the actual value of the d-axis current is adjusted proportionally and integrally to obtain the d-axis voltage reference signal. The d-axis voltage value is obtained by subtracting the d-axis voltage reference signal from the sum of the d-axis output voltage value and the q-axis voltage coupling value. The difference between the target value of the q-axis current and the actual value of the q-axis current is adjusted proportionally and integrally to obtain the q-axis voltage reference signal. The difference between the q-axis output voltage value and the d-axis voltage coupling value is subtracted from the q-axis voltage reference signal to obtain the q-axis voltage value. Based on the d-axis voltage value and the q-axis voltage value, determine the A-phase voltage value, B-phase voltage value and C-phase voltage value to be output by the full-power converter, and control the full-power converter to output the A-phase voltage value, the B-phase voltage value and the C-phase voltage value.

4. The method according to claim 3, characterized in that, The process of determining the A-phase, B-phase, and C-phase voltage values ​​to be output by the full-power converter based on the d-axis and q-axis voltage values ​​includes: Determine the angle between the AC voltage and AC current transmitted by the AC power grid; Based on the included angle, the d-axis voltage value and the q-axis voltage value are inversely transformed to obtain the A-phase voltage value, the B-phase voltage value, and the C-phase voltage value in the three-phase stationary coordinate system.

5. The method according to claim 1, characterized in that, The generator in the DC grid is a wind turbine generator, and the full-power converter is a grid-connected converter used to connect the DC grid where the wind turbine generator is located to the AC grid. When the frequency fluctuation range exceeds the third preset fluctuation range, the method further includes: Active power damping control is applied to the grid-connected converter to adjust the active power output of the converter by adjusting the d-axis and q-axis generation voltages, thereby reducing the frequency fluctuation range of the AC power grid.

6. The method according to claim 5, characterized in that, The active power damping control of the grid-connected converter includes: The rotor angular frequency setting value of the wind turbine generator and the reactive power setting value of the grid-connected converter are obtained, and the actual value of the rotor angular frequency of the wind turbine generator, the reactive power value and the active power value output by the grid-connected converter are determined. The difference between the rotor angular frequency setpoint and the actual rotor angular frequency is adjusted proportionally and integrally to obtain the d-axis current setpoint, and the difference between the reactive power setpoint and the reactive power value is adjusted proportionally and integrally to obtain the q-axis current setpoint. The active power value is subjected to active damping control to obtain an active damping output signal, and the active damping output signal is added to the d-axis current setting value to obtain the corrected d-axis current setting value. The grid-connected converter is subjected to inner-loop current control based on the actual value of the d-axis current, the actual value of the q-axis current, the set value of the d-axis current, and the set value of the q-axis current, so as to adjust the output d-axis generation voltage and q-axis generation voltage of the grid-connected converter.

7. A frequency adjustment device for an AC power grid, characterized in that, The device includes: The fluctuation identification module is used to monitor the grid frequency of the AC power grid, determine the frequency fluctuation range of the AC power grid, and compare the frequency fluctuation range with a first preset fluctuation range, a second preset fluctuation range, and a third preset fluctuation range, wherein the third preset fluctuation range is greater than the second preset fluctuation range, and the second preset fluctuation range is greater than the first preset fluctuation range. The first control module is configured to perform voltage outer loop and current inner loop control based on frequency feedback control on the full-power converter when the frequency fluctuation range exceeds the first preset fluctuation range but is less than the second preset fluctuation range, so as to adjust the active power output of the full-power converter and reduce the frequency fluctuation range of the AC grid. The voltage outer loop and current inner loop control based on frequency feedback control on the full-power converter includes: acquiring the actual value of the reactive power output of the full-power converter, obtaining a preset reactive power target value, and performing a proportional-integral calculation on the reactive power difference between the actual reactive power value and the reactive power target value to obtain a q-axis current target value; acquiring the actual value of the AC grid frequency, obtaining a preset AC grid frequency target value, and performing a proportional-integral calculation on the frequency difference between the actual AC grid frequency and the AC grid frequency target value. The frequency response power of the full-power converter is determined; the DC voltage value input to the full-power converter and the actual value of the active power output of the full-power converter are collected, and preset active power target value and DC voltage target value are obtained. Based on the actual active power value, the active power target value, and the frequency response power, active-voltage droop control is performed on the voltage difference between the DC voltage value and the DC voltage target value to obtain the d-axis current target value; the actual d-axis current value and the actual q-axis current value of the output current of the full-power converter are determined, and based on the actual d-axis current value, the actual q-axis current value, the d-axis current target value, and the q-axis current target value, current inner loop control is performed on the full-power converter to change the output voltage of the full-power converter, thereby adjusting the active power output of the full-power converter; The second control module is used to perform voltage outer loop and current inner loop control on the full-power converter based on frequency feedback control and virtual voltage feedback control when the frequency fluctuation range exceeds the third preset fluctuation range, so as to adjust the active power output of the full-power converter and reduce the frequency fluctuation range of the AC grid.

8. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

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