A frequency control method and system for a flexible low-frequency transmission system for offshore wind power

Abstract

This invention discloses a frequency control method and system for a flexible low-frequency power transmission system for offshore wind power, relating to the field of power system frequency support technology. The method involves acquiring the operating parameters of the flexible low-frequency power transmission system and the frequency of the wind turbine generators. A power frequency-side control model is used to perform power frequency coordination optimization control on the operating parameters to obtain power frequency control commands and the target system frequency. A low-frequency-side control model is used to perform low-frequency coordination optimization control on the target system frequency and operating parameters to obtain low-frequency control commands. A frequency active support control model is used to perform frequency support optimization control on the wind turbine generator frequency to obtain additional power commands. Power frequency control commands, low-frequency control commands, and additional power commands are then used to perform power control on the flexible low-frequency power transmission system for offshore wind power. This invention solves the technical problem that existing frequency coordination control systems using offshore wind power connected to the grid via flexible low-frequency transmission often result in actual frequency deviations from the rated operating point, increasing the difficulty of system control.

Description

Technical Field

[0001] This invention relates to the field of power system frequency support technology, and in particular to a frequency control method and system for a flexible low-frequency transmission system for offshore wind power. Background Technology

[0002] Flexible low-frequency (LHF) transmission systems, utilizing power electronics technology, operate at frequencies lower than the power frequency (typically 20Hz), resulting in reduced line impedance, lower voltage drop and charging power, and increased cable current carrying capacity, significantly enhancing transmission capacity. They also offer advantages such as zero-crossing current interruption and ease of grid integration. Furthermore, wind turbines within LHF systems can directly output low-frequency energy without the need for additional frequency converters, reducing costs. However, with the increasing penetration of renewable energy sources such as offshore wind power, frequency stability issues in power systems are becoming increasingly prominent. Active frequency support for offshore wind power LHF transmission systems is one effective means of mitigating frequency stability problems; therefore, there is an urgent need to propose frequency control methods for offshore wind power LHF transmission systems.

[0003] Currently, existing technologies mainly achieve frequency control of offshore wind power flexible low-frequency transmission systems through frequency coordination control systems with and without communication coordination control via flexible DC grid connection. However, this can lead to a significant deviation of the actual frequency from the rated operating point, increasing the control difficulty of the offshore wind power flexible low-frequency transmission system. Summary of the Invention

[0004] This invention provides a frequency control method and system for a flexible low-frequency transmission system for offshore wind power. It solves the technical problem that the existing technology mainly achieves frequency control of the flexible low-frequency transmission system for offshore wind power through a frequency coordination control system with and without communication coordination control. However, this results in a large deviation of the actual frequency from the rated operating point, which increases the control difficulty of the flexible low-frequency transmission system for offshore wind power.

[0005] The first aspect of this invention provides a frequency control method for a flexible low-frequency transmission system for offshore wind power, comprising:

[0006] The operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine are obtained, and the operating parameters and the frequency of the wind turbine are input into a preset frequency support control model. The frequency support control model includes a power frequency side control model, a low-frequency side control model and a frequency active support control model.

[0007] The power frequency side control model is used to perform power frequency coordinated optimization control on the operating parameters to obtain the power frequency control command and the target system frequency.

[0008] The target system frequency and the operating parameters are subjected to low-frequency coordinated optimization control through the low-frequency side control model to obtain low-frequency control commands.

[0009] The frequency support optimization control of the wind turbine is performed by the frequency active support control model to obtain the additional power command.

[0010] The power frequency control command, the low frequency control command, and the additional power command are used to control the power of the offshore wind power flexible low frequency transmission system.

[0011] Optionally, the power frequency side control model includes a first phase-locked loop, a first difference arithmetic unit, a frequency transfer coefficient unit, a first current inner loop controller, a voltage outer loop controller, and a first converter. The operating parameters include power frequency side current and power frequency side voltage. The step of using the power frequency side control model to perform power frequency coordinated optimization control on the operating parameters to obtain the power frequency control command and the target system frequency includes:

[0012] The power frequency side current is optimized and controlled by phase-locked loop through the first phase-locked loop to obtain the system frequency and the first phase value.

[0013] The first difference calculation is performed on the system frequency and the pre-acquired rated frequency of the power frequency system by the first difference calculation to obtain the first difference;

[0014] The frequency transfer coefficient is used to correct the first difference to obtain the target system frequency;

[0015] The voltage outer loop controller performs voltage optimization control on the pre-acquired DC voltage value and DC voltage control command value to obtain the power frequency current control parameters;

[0016] Based on the first phase value, the power frequency side current and the power frequency side voltage are subjected to coordinate transformation operation by the first converter to obtain the power frequency component parameters;

[0017] The first current inner loop controller is used to perform current optimization control on the power frequency current control parameters and the power frequency component parameters to obtain the power frequency control command.

[0018] Optionally, the voltage outer loop controller includes a second differential operator, a first PI controller, and a first reactive power controller. The step of performing voltage optimization control on the pre-acquired DC voltage value and DC voltage control command value through the voltage outer loop controller to obtain the power frequency current control parameters includes:

[0019] The second difference calculator performs a difference calculation on the pre-acquired DC voltage value and the DC voltage control command value to obtain the DC voltage deviation;

[0020] The DC voltage deviation is corrected by the first PI controller to obtain the first current control reference value;

[0021] The first reactive power controller is used to perform reactive power optimization operation to obtain a second current control reference value, and the first current control reference value and the second current control reference value are used as power frequency current control parameters.

[0022] Optionally, the operating parameters further include low-frequency side voltage and low-frequency side current. The low-frequency side control model includes a third difference arithmetic unit, an integral arithmetic unit, a second converter, a low-frequency voltage controller, and a second current inner loop controller. The step of performing low-frequency coordinated optimization control on the target system frequency and the operating parameters through the low-frequency side control model to obtain low-frequency control commands includes:

[0023] The third difference calculator performs a difference calculation between the preset low-frequency system rated frequency and the target system frequency to obtain the system frequency deviation.

[0024] The system frequency deviation is integrated by the integrator to obtain the low-frequency side system control phase.

[0025] Based on the low-frequency side system control phase, the low-frequency side voltage and low-frequency side current are subjected to coordinate transformation operation through the second converter to obtain low-frequency component parameters;

[0026] The low-frequency voltage controller is used to perform voltage optimization control on the pre-acquired AC voltage value and AC voltage control reference value to obtain low-frequency current control parameters;

[0027] The second current inner loop controller is used to perform current optimization control on the low-frequency component parameters and the low-frequency current control parameters to obtain low-frequency control commands.

[0028] Optionally, the low-frequency voltage controller includes a fourth differential operator, a second PI controller, and a second reactive power controller. The step of using the low-frequency voltage controller to perform voltage optimization control on the pre-acquired AC voltage value and AC voltage control reference value to obtain low-frequency current control parameters includes:

[0029] The AC voltage deviation is obtained by performing a difference calculation on the pre-acquired AC voltage value and the AC voltage control reference value through the fourth difference calculation unit.

[0030] The AC voltage deviation is corrected by the second PI controller to obtain the third current control reference value;

[0031] The second reactive power controller is used to perform reactive power optimization operation to obtain a fourth current control reference value, and the third current control reference value and the fourth current control reference value are used as low-frequency current control parameters.

[0032] Optionally, the step of performing frequency support optimization control on the wind turbine frequency through the frequency active support control model to obtain an additional power command includes:

[0033] The frequency of the wind turbine is input into the frequency active support control model, wherein the frequency active support control model includes a second phase-locked loop, a virtual inertia controller, a frequency droop power controller, and an adder.

[0034] The frequency of the wind turbine is obtained by performing phase-locked synchronization optimization control on the wind turbine side through the second phase-locked loop.

[0035] The virtual inertia controller is used to optimize the wind turbine frequency to obtain the first additional power. The virtual inertia controller includes a differential arithmetic unit and a virtual inertia coefficient unit connected in sequence.

[0036] The frequency droop power controller is used to optimize the frequency droop control of the wind turbine side frequency to obtain the second additional power.

[0037] The first additional power and the second additional power are summed by the summing arithmetic unit to obtain the additional power command.

[0038] The second aspect of this invention provides a frequency control system for a flexible low-frequency transmission system for offshore wind power, comprising:

[0039] The acquisition module is used to acquire the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine, and input the operating parameters and the frequency of the wind turbine into a preset frequency support control model. The frequency support control model includes a power frequency side control model, a low-frequency side control model and a frequency active support control model.

[0040] The power frequency control module is used to perform power frequency coordinated optimization control on the operating parameters using the power frequency side control model to obtain power frequency control commands and target system frequency;

[0041] The low-frequency control module is used to perform low-frequency coordinated optimization control on the target system frequency and the operating parameters through the low-frequency side control model to obtain low-frequency control commands;

[0042] The frequency control module is used to perform frequency support optimization control on the frequency of the wind turbine through the frequency active support control model to obtain additional power commands;

[0043] The control module is used to perform power control on the offshore wind power flexible low-frequency transmission system using the power frequency control command, the low-frequency control command, and the additional power command.

[0044] A third aspect of the present invention provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor causes the processor to perform the steps of the frequency control method for the offshore wind power flexible low-frequency transmission system as described in any of the preceding claims.

[0045] The fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed, it implements the frequency control method of the offshore wind power flexible low-frequency transmission system as described in any of the preceding claims.

[0046] The fifth aspect of the present invention provides a computer program product, the computer program product comprising a computer program stored on a non-transitory computer-readable storage medium, the computer program comprising program instructions, wherein, when the program instructions are executed by a computer, the computer performs a frequency control method for a flexible low-frequency transmission system for offshore wind power as described in any of the preceding claims.

[0047] As can be seen from the above technical solutions, the present invention has the following advantages:

[0048] This invention utilizes a pre-defined frequency support control model to perform frequency modulation control on an offshore wind power flexible low-frequency transmission system, obtaining corresponding power frequency control commands, low-frequency control commands, and additional power commands. This achieves frequency control of the offshore wind power flexible low-frequency transmission system without requiring communication-coordinated control or non-communication-coordinated control, overcoming the technical problem of existing technologies that primarily rely on communication-coordinated control systems for offshore wind power connected to flexible DC grids. However, this often results in significant deviations of the actual frequency from the rated operating point, increasing the control difficulty of the offshore wind power flexible low-frequency transmission system. This invention achieves frequency control of the offshore wind power flexible low-frequency transmission system by acquiring the operating parameters of the system and the wind turbine frequency, obtaining corresponding power frequency control commands, low-frequency control commands, and additional power commands. The power frequency and low-frequency control commands are used to regulate the system, ensuring that the low-frequency side of the system matches the power frequency side. The additional power commands then provide active support control for the system, reducing the control difficulty of the offshore wind power flexible low-frequency transmission system and improving its operational reliability. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a flowchart of the steps of a frequency control method for a flexible low-frequency transmission system for offshore wind power provided in Embodiment 1 of the present invention;

[0051] Figure 2 This is a flowchart illustrating the steps of a frequency control method for a flexible low-frequency transmission system for offshore wind power, provided in Embodiment 2 of the present invention.

[0052] Figure 3 This is a schematic diagram of the frequency support control model provided in Embodiment 2 of the present invention;

[0053] Figure 4 This is a structural block diagram of the frequency control system of a flexible low-frequency transmission system for offshore wind power provided in Embodiment 3 of the present invention;

[0054] Figure 5 This is a structural block diagram of an electronic device provided in Embodiment 4 of the present invention. Detailed Implementation

[0055] This invention provides a frequency control method for a flexible low-frequency transmission system for offshore wind power, which addresses the technical problem that existing technologies mainly rely on frequency coordination control systems with and without communication coordination control for offshore wind power connected to the DC grid to achieve frequency control of the flexible low-frequency transmission system for offshore wind power. However, this can lead to a significant deviation of the actual frequency from the rated operating point, increasing the control difficulty of the flexible low-frequency transmission system for offshore wind power.

[0056] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0057] Please see Figure 1 , Figure 1 This is a flowchart illustrating the steps of a frequency control method for a flexible low-frequency transmission system for offshore wind power, as provided in Embodiment 1 of the present invention.

[0058] This invention provides a frequency control method for a flexible low-frequency transmission system for offshore wind power, comprising:

[0059] Step 101: Obtain the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine, and input the operating parameters and the frequency of the wind turbine into the preset frequency support control model. The frequency support control model includes the power frequency side control model, the low-frequency side control model and the frequency active support control model.

[0060] Operating parameters refer to the grid-connected voltage and current of the power frequency side PCC point and the grid-connected voltage and current of the low frequency side PCC point of the offshore wind power flexible low frequency transmission system.

[0061] In this embodiment of the invention, the grid-connected voltage, grid-connected current, low-frequency PCC point voltage, low-frequency PCC point current, and wind turbine frequency of the offshore wind power flexible low-frequency transmission system are obtained, and the grid-connected voltage, current, and frequency of the wind turbine are input into a preset frequency support control model.

[0062] Step 102: Use the power frequency side control model to perform power frequency coordinated optimization control on the operating parameters to obtain the power frequency control command and the target system frequency;

[0063] In this embodiment of the invention, the grid-connected voltage and grid-connected current at the PCC point on the power frequency side are input into the power frequency side control model for power frequency coordinated optimization control to obtain the power frequency control command and the target system frequency. The power frequency side control model includes a first phase-locked loop, a first difference arithmetic unit, a frequency transfer coefficient unit, a first current inner loop controller, a voltage outer loop controller, and a first converter.

[0064] Step 103: Perform low-frequency coordinated optimization control on the target system frequency and operating parameters using the low-frequency side control model to obtain low-frequency control commands;

[0065] In this embodiment of the invention, the target system frequency, the grid-connected voltage at the low-frequency side PCC point, and the grid-connected current at the low-frequency side PCC point are input into the low-frequency side control model for low-frequency coordinated optimization control to obtain low-frequency control commands. The low-frequency side control model includes a third difference arithmetic unit, an integrator, a second converter, a low-frequency voltage controller, and a second current inner-loop controller.

[0066] Step 104: Perform frequency support optimization control on the wind turbine frequency using the frequency active support control model to obtain additional power commands;

[0067] In this embodiment of the invention, the frequency input frequency active support control model of the wind turbine is subjected to frequency support optimization control to obtain additional power commands.

[0068] Step 105: Use power frequency control commands, low frequency control commands, and additional power commands to control the power of the offshore wind power flexible low frequency transmission system.

[0069] In this embodiment of the invention, power frequency control commands and low frequency control commands are used to regulate the power of the onshore frequency converter of the offshore wind power flexible low frequency transmission system, and additional power commands are used to perform active frequency support control on the wind turbines of the offshore wind power flexible low frequency transmission system.

[0070] In this embodiment of the invention, frequency modulation control of the offshore wind power flexible low-frequency transmission system is performed through a preset frequency support control model to obtain corresponding power frequency control commands, low-frequency control commands, and additional power commands. Frequency control of the offshore wind power flexible low-frequency transmission system can be achieved without communication coordination control or non-communication coordination control. This overcomes the technical problem that the existing technology mainly uses the frequency coordination control system of offshore wind power connected to the DC grid with or without communication coordination control to achieve frequency control of the offshore wind power flexible low-frequency transmission system. However, this will cause the actual frequency to deviate significantly from the rated operating point, increasing the control difficulty of the offshore wind power flexible low-frequency transmission system. This invention acquires the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine to perform frequency control on the offshore wind power flexible low-frequency transmission system, thereby obtaining corresponding power frequency control commands, low-frequency control commands, and additional power commands. By adjusting the system through the power frequency control commands and low-frequency control commands, the changes on the low-frequency side of the system are consistent with those on the power frequency side. Then, the additional power commands provide active support control for the system, reducing the control difficulty of the offshore wind power flexible low-frequency transmission system and improving the reliability of its operation.

[0071] Please see Figure 2 , Figure 2 This is a flowchart illustrating the steps of a frequency control method for a flexible low-frequency transmission system for offshore wind power, as provided in Embodiment 2 of the present invention.

[0072] This invention provides a frequency control method for a flexible low-frequency transmission system for offshore wind power, comprising:

[0073] Step 201: Obtain the operating parameters of the offshore wind power flexible low-frequency transmission system and the wind turbine frequency, and input the operating parameters and wind turbine frequency into the preset frequency support control model. The frequency support control model includes the power frequency side control model, the low-frequency side control model and the frequency active support control model.

[0074] In the embodiments of the present invention, see Figure 3As shown, the frequency f of the wind turbine in the offshore wind power flexible low-frequency transmission system is obtained. Pw The grid connection voltage u of the power frequency side PCC points on both sides of the onshore frequency converter station D , grid-connected current i at PCC point on the power frequency side D Low-frequency side PCC point grid connection voltage u D and the grid-connected current i at the low-frequency side PCC point D Input a preset frequency support control model, which includes a power frequency side control model, a low frequency side control model, and a frequency active support control model.

[0075] It should be noted that the frequency of the wind turbine is collected through a PLL phase-locked loop.

[0076] Step 202: Use the power frequency side control model to perform power frequency coordinated optimization control on the operating parameters to obtain the power frequency control command and the target system frequency;

[0077] Further, see Figure 3 As shown, the power frequency side control model includes a first phase-locked loop, a first difference arithmetic unit, a frequency transfer coefficient unit, a first current inner loop controller, a voltage outer loop controller, and a first converter. The operating parameters include power frequency side current and power frequency side voltage. Step 202 includes the following sub-steps:

[0078] S11. The power frequency side current is optimized by phase-locked synchronization through the first phase-locked loop to obtain the system frequency and the first phase value;

[0079] The first phase value refers to the phase of the PCC point grid connection vector.

[0080] In this embodiment of the invention, the power frequency side current (i.e., the grid-connected current i at the power frequency side PCC point) is controlled by a first phase-locked loop (PLL). D Phase-locked synchronization optimization control is performed to obtain the system frequency f. D and the first phase value .

[0081] S12. The first difference calculation is performed on the system frequency and the pre-acquired rated frequency of the power frequency system by the first difference calculation unit to obtain the first difference;

[0082] In this embodiment of the invention, the preset rated frequency of the power frequency system and the system frequency f are used. D Input the first difference operator to perform difference processing and obtain the first difference.

[0083] S13. Use a frequency transfer coefficient device to correct the first difference to obtain the target system frequency;

[0084] In this embodiment of the invention, a frequency transfer coefficient generator is used to multiply the first difference with a preset frequency transfer coefficient H0 to obtain the target system frequency.

[0085] S14. The voltage outer loop controller performs voltage optimization control on the pre-acquired DC voltage value and DC voltage control command value to obtain the power frequency current control parameters.

[0086] Further, see Figure 3 As shown, the voltage outer loop controller includes a second differential calculator, a first PI controller, and a first reactive power controller. S14 includes the following sub-steps:

[0087] S141. The second difference arithmetic unit performs difference calculation on the pre-acquired DC voltage value and DC voltage control command value to obtain the DC voltage deviation.

[0088] In this embodiment of the invention, the pre-acquired DC voltage value U dc and DC voltage control command value U dcref Input the second difference calculator to perform difference calculations and obtain the DC voltage deviation.

[0089] S142. The DC voltage deviation is corrected by the first PI controller to obtain the first current control reference value;

[0090] In this embodiment of the invention, the DC voltage deviation is corrected by the first PI controller to obtain the first current control reference value i. Ddref .

[0091] S143. A first reactive power controller is used to perform reactive power optimization operation to obtain a second current control reference value, and the first current control reference value and the second current control reference value are used as power frequency current control parameters.

[0092] In this embodiment of the invention, a second current control reference value i is generated by a first reactive power controller. Dqref The first current control reference value and the second current control reference value are used as the power frequency current control parameters.

[0093] S15. Based on the first phase value, the power frequency side current and power frequency side voltage are transformed by the first converter to obtain the power frequency component parameters.

[0094] The power frequency component parameter refers to the grid-connected voltage u at the PCC point on the power frequency side. D Current i D dq axis component u Dd u Dq i Dd i Dq .

[0095] In this embodiment of the invention, the first phase value, the power frequency side current, and the power frequency side voltage are input into the first converter for coordinate transformation to obtain the power frequency component parameters.

[0096] S16. The first current inner loop controller is used to optimize the current control of the power frequency current control parameters and power frequency component parameters to obtain the power frequency control command.

[0097] In this embodiment of the invention, the power frequency current control parameters and power frequency component parameters are input into the first current inner loop controller for current optimization control to obtain the power frequency control command.

[0098] Step 203: Perform low-frequency coordinated optimization control on the target system frequency and operating parameters using the low-frequency side control model to obtain low-frequency control commands;

[0099] Furthermore, the operating parameters also include low-frequency side voltage and low-frequency side current. The low-frequency side control model includes a third difference arithmetic unit, an integrator, a second converter, a low-frequency voltage controller, and a second current inner loop controller. Step 203 includes the following sub-steps:

[0100] S21. The system frequency deviation is obtained by performing a difference calculation on the preset low-frequency system rated frequency and the target system frequency through the third difference calculation unit.

[0101] In this embodiment of the invention, the preset low-frequency system rated frequency f is... Pref The system frequency deviation f is obtained by performing a difference operation between the target system frequency input and the third difference operator. P .

[0102] It should be noted that, in order to synchronize the frequency changes of the power frequency side system to the low frequency side, a frequency transfer stage is introduced in the control, and a system frequency deviation f is set. P As shown below:

[0103]

[0104] S22. The system frequency deviation is integrated by the integrator to obtain the control phase of the low-frequency side system;

[0105] In this embodiment of the invention, the system frequency deviation is integrated by an integrator to obtain the low-frequency side system control phase. .

[0106] S23. Based on the low-frequency side system control phase, the low-frequency side voltage and low-frequency side current are transformed by the second converter to obtain the low-frequency component parameters.

[0107] Low-frequency component parameters refer to the grid-connected voltage u at the low-frequency side PCC point. P Current i Pdq axis component u Pd u Pq i Pd i Pq .

[0108] In this embodiment of the invention, the low-frequency side system control phase and the low-frequency side voltage (i.e., the grid-connected voltage u at the low-frequency side PCC point) are... D ) and low-frequency side current (i.e., low-frequency side PCC point grid-connected current i) D The input is used to perform coordinate transformation operation on the second transformer to obtain the low-frequency component parameters.

[0109] S24. A low-frequency voltage controller is used to perform voltage optimization control on the pre-acquired AC voltage value and AC voltage control reference value to obtain low-frequency current control parameters;

[0110] Furthermore, the low-frequency voltage controller includes a fourth differential operator, a second PI controller, and a second reactive power controller. S24 includes the following sub-steps:

[0111] S241. The AC voltage deviation is obtained by performing a difference calculation on the pre-acquired AC voltage value and AC voltage control reference value through the fourth difference calculation unit.

[0112] In this embodiment of the invention, the pre-acquired AC voltage value U ac and AC voltage control reference value U acref Input the fourth difference operator to perform difference calculations and obtain the AC voltage deviation.

[0113] S242. The AC voltage deviation is corrected by the second PI controller to obtain the third current control reference value;

[0114] In this embodiment of the invention, the AC voltage deviation is corrected by the second PI controller to obtain the third current control reference value i. Pdref .

[0115] S243. A second reactive power controller is used to perform reactive power optimization operation to obtain a fourth current control reference value, and the third and fourth current control reference values ​​are used as low-frequency current control parameters.

[0116] In this embodiment of the invention, a fourth current control reference value i is generated by a second reactive power controller. Pqref The third and fourth current control reference values ​​are used as low-frequency current control parameters.

[0117] S25. The second current inner loop controller is used to optimize the current control of the low-frequency component parameters and low-frequency current control parameters to obtain the low-frequency control command.

[0118] In this embodiment of the invention, low-frequency component parameters and low-frequency current control parameters are input into the second current inner loop controller for current optimization control to obtain low-frequency control commands.

[0119] Step 204: Input the wind turbine frequency into the frequency active support control model, wherein the frequency active support control model includes a second phase-locked loop, a virtual inertia controller, a frequency droop power controller, and an adder.

[0120] In this embodiment of the invention, the frequency of the wind turbine is optimized and controlled using a frequency active support control model, wherein, see reference... Figure 3 As shown, the frequency active support control model includes a second phase-locked loop, a virtual inertia controller, a frequency droop power controller, and an adder.

[0121] Step 205: Perform phase-locked synchronization optimization control on the wind turbine frequency through the second phase-locked loop to obtain the wind turbine side frequency;

[0122] In this embodiment of the invention, the wind turbine frequency is input to the second phase-locked loop (PLL) for phase-locked synchronization optimization control to obtain the wind turbine side frequency f. Pw .

[0123] Step 206: Use a virtual inertia controller to optimize the wind turbine frequency and obtain the first additional power. The virtual inertia controller includes a differential arithmetic unit and a virtual inertia coefficient unit connected in sequence.

[0124] In this embodiment of the invention, the wind turbine side frequency is optimized and controlled sequentially by a differential arithmetic unit and a virtual inertia coefficient unit to obtain the first additional power. .

[0125] It should be noted that the virtual inertia coefficient is specifically:

[0126]

[0127] in, The absolute value of the rate of change of frequency for wind turbine generators is given, where m is the power exponent of the rate of change of frequency. This serves as the baseline value for the virtual inertia constant of the wind turbine. This represents the increment coefficient of the virtual inertia constant of the wind turbine. The dead zone value for measuring the rate of change of frequency of wind turbine generators.

[0128] It should be noted that the expression for the first additional power is:

[0129]

[0130] Step 207: Use a frequency droop power controller to perform frequency droop optimization control on the wind turbine side to obtain the second additional power;

[0131] In this embodiment of the invention, the frequency droop power controller on the wind turbine side is subjected to frequency droop optimization control to obtain a second additional power. .

[0132]

[0133] in, This is the power-frequency droop factor. This is a reference value for the measured frequency of the wind turbine.

[0134] Step 208: The first additional power and the second additional power are summed by the summation arithmetic unit to obtain the additional power instruction.

[0135] In this embodiment of the invention, the first additional power and the second additional power are input into an adder for addition to obtain an additional power instruction. .

[0136]

[0137] Step 209: Use power frequency control commands, low frequency control commands, and additional power commands to control the power of the offshore wind power flexible low frequency transmission system.

[0138] In this embodiment of the invention, additional power commands are used to perform active frequency support additional control on the wind turbines of the offshore wind power flexible low-frequency transmission system. Power frequency control commands and low-frequency control commands are input to a PWM modulator for conversion, resulting in power frequency control signals and low-frequency control signals. These power frequency control signals and low-frequency control signals are then used to control the power output of the onshore frequency converter station of the offshore wind power flexible low-frequency transmission system.

[0139] In this embodiment of the invention, frequency modulation control of the offshore wind power flexible low-frequency transmission system is performed through a preset frequency support control model to obtain corresponding power frequency control commands, low-frequency control commands, and additional power commands. Frequency control of the offshore wind power flexible low-frequency transmission system can be achieved without communication coordination control or non-communication coordination control. This overcomes the technical problem that the existing technology mainly uses the frequency coordination control system of offshore wind power connected to the DC grid with or without communication coordination control to achieve frequency control of the offshore wind power flexible low-frequency transmission system. However, this will cause the actual frequency to deviate significantly from the rated operating point, increasing the control difficulty of the offshore wind power flexible low-frequency transmission system. This invention acquires the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine to perform frequency control on the offshore wind power flexible low-frequency transmission system, thereby obtaining corresponding power frequency control commands, low-frequency control commands, and additional power commands. By adjusting the system through the power frequency control commands and low-frequency control commands, the changes on the low-frequency side of the system are consistent with those on the power frequency side. Then, the additional power commands provide active support control for the system, reducing the control difficulty of the offshore wind power flexible low-frequency transmission system and improving the reliability of its operation.

[0140] Please see Figure 4 , Figure 4 This is a structural block diagram of the frequency control system of a flexible low-frequency transmission system for offshore wind power provided in Embodiment 3 of the present invention.

[0141] This invention provides a frequency control system for a flexible low-frequency transmission system for offshore wind power, comprising:

[0142] The acquisition module 301 is used to acquire the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine, and input the operating parameters and the frequency of the wind turbine into a preset frequency support control model. The frequency support control model includes a power frequency side control model, a low-frequency side control model and a frequency active support control model.

[0143] The power frequency control module 302 is used to perform power frequency coordinated optimization control on the operating parameters using the power frequency side control model, so as to obtain the power frequency control command and the target system frequency;

[0144] The low-frequency control module 303 is used to perform low-frequency coordinated optimization control on the target system frequency and operating parameters through the low-frequency side control model to obtain low-frequency control commands.

[0145] The frequency control module 304 is used to perform frequency support optimization control on the wind turbine frequency through the active frequency support control model to obtain additional power commands.

[0146] The control module 305 is used to control the power of the offshore wind power flexible low-frequency transmission system using power frequency control commands, low-frequency control commands, and additional power commands.

[0147] Furthermore, the power frequency side control model includes a first phase-locked loop, a first difference arithmetic unit, a frequency transfer coefficient unit, a first current inner loop controller, a voltage outer loop controller, and a first converter. The power frequency control module 302 includes:

[0148] The first synchronization submodule is used to perform phase-locked synchronization optimization control on the power frequency side current through the first phase-locked loop to obtain the system frequency and the first phase value.

[0149] The first deviation submodule is used to perform a difference calculation on the system frequency and the pre-acquired rated frequency of the power frequency system through the first difference calculator to obtain the first difference.

[0150] The first correction submodule is used to perform frequency correction on the first difference using a frequency transfer coefficient generator to obtain the target system frequency.

[0151] The first voltage optimization submodule is used to perform voltage optimization control on the pre-acquired DC voltage value and DC voltage control command value through the voltage outer loop controller to obtain the power frequency current control parameters;

[0152] The first transformation submodule is used to perform coordinate transformation operations on the power frequency side current and power frequency side voltage based on the first phase value through the first converter to obtain the power frequency component parameters.

[0153] The first current optimization submodule is used to perform current optimization control on the power frequency current control parameters and power frequency component parameters using the first current inner loop controller to obtain power frequency control commands.

[0154] Furthermore, the voltage outer loop controller includes a second differential calculator, a first PI controller, and a first reactive power controller. The first voltage optimization submodule includes:

[0155] The first deviation unit is used to perform a difference calculation on the pre-acquired DC voltage value and DC voltage control command value through the second difference arithmetic unit to obtain the DC voltage deviation;

[0156] The first calibration unit is used to correct the DC voltage deviation through the first PI controller to obtain the first current control reference value;

[0157] The first reactive power optimization unit is used to perform reactive power optimization operation using the first reactive power controller to obtain the second current control reference value, and uses the first current control reference value and the second current control reference value as power frequency current control parameters.

[0158] Furthermore, the operating parameters also include low-frequency side voltage and low-frequency side current. The low-frequency side control model includes a third difference arithmetic unit, an integrator, a second converter, a low-frequency voltage controller, and a second current inner loop controller. The low-frequency control module 303 includes:

[0159] The second deviation submodule is used to perform difference calculation between the preset low-frequency system rated frequency and the target system frequency through the third difference calculator to obtain the system frequency deviation;

[0160] The integral submodule is used to perform integral calculations on the system frequency deviation through the integrator to obtain the low-frequency side system control phase.

[0161] The second transformation submodule is used to perform coordinate transformation operations on the low-frequency side voltage and low-frequency side current through the second converter based on the low-frequency side system control phase to obtain low-frequency component parameters.

[0162] The second voltage optimization submodule is used to perform voltage optimization control on the pre-acquired AC voltage value and AC voltage control reference value using a low-frequency voltage controller to obtain low-frequency current control parameters;

[0163] The second current optimization submodule is used to perform current optimization control on the low-frequency component parameters and low-frequency current control parameters using the second current inner loop controller to obtain low-frequency control commands.

[0164] Furthermore, the low-frequency voltage controller includes a fourth differential operator, a second PI controller, a second reactive power controller, and a second voltage optimization submodule, including:

[0165] The second deviation unit is used to perform difference calculation on the pre-acquired AC voltage value and AC voltage control reference value through the fourth difference arithmetic unit to obtain the AC voltage deviation.

[0166] The second correction unit is used to correct the AC voltage deviation through the second PI controller to obtain the third current control reference value.

[0167] The second reactive power optimization unit is used to perform reactive power optimization operation using the second reactive power controller to obtain the fourth current control reference value, and uses the third current control reference value and the fourth current control reference value as low-frequency current control parameters.

[0168] Furthermore, the frequency control module 304 includes:

[0169] The input submodule is used to input the wind turbine frequency into the frequency active support control model, wherein the frequency active support control model includes a second phase-locked loop, a virtual inertia controller, a frequency droop power controller, and an adder.

[0170] The second synchronization submodule is used to perform phase-locked synchronization optimization control on the wind turbine frequency through the second phase-locked loop to obtain the wind turbine side frequency.

[0171] The wind turbine optimization submodule is used to optimize the wind turbine side frequency using a virtual inertia controller to obtain the first additional power. The virtual inertia controller includes a differential arithmetic unit and a virtual inertia coefficient unit connected in sequence.

[0172] The frequency droop optimization submodule is used to perform frequency droop optimization control on the wind turbine side frequency using a frequency droop power controller to obtain a second additional power.

[0173] The summation submodule is used to sum the first additional power and the second additional power through the summation arithmetic unit to obtain the additional power instruction.

[0174] Please see Figure 5 , Figure 5 This is a structural block diagram of an electronic device provided in Embodiment 4 of the present invention.

[0175] An electronic device according to an embodiment of the present invention includes: a memory 401 and a processor 402. The memory 402 stores a computer program. When the computer program is executed by the processor 402, the processor 402 executes the frequency control method of the offshore wind power flexible low-frequency transmission system as described in any of the above embodiments.

[0176] Memory 401 may be an electronic memory such as flash memory, EEPROM (Electrically Erasable Programmable Read-Only Memory), EPROM, hard disk, or ROM. Memory 401 has storage space 403 for program code 413 for performing any of the method steps described above. For example, storage space 403 for program code may include individual program codes 413 for implementing the various steps in the methods described above. This program code may be read from or written to one or more computer program products. These computer program products include program code carriers such as hard disks, compact discs (CDs), memory cards, or floppy disks. The program code may be compressed, for example, in a suitable form. When run by a computing processing device, this code causes the computing processing device to perform the various steps in the methods described above.

[0177] Embodiment 5 of the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the frequency control method of the offshore wind power flexible low-frequency transmission system as described in any of the above embodiments.

[0178] Embodiment 6 of the present invention also provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer performs a frequency control method for a flexible low-frequency transmission system for offshore wind power as described in any of the above embodiments.

[0179] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0180] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between apparatuses or units, and may be electrical, mechanical, or other forms.

[0181] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0182] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0183] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and 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 steps of the methods of the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0184] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A frequency control method for a flexible low-frequency transmission system for offshore wind power, characterized in that, include: The operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine are obtained, and the operating parameters and the frequency of the wind turbine are input into a preset frequency support control model. The frequency support control model includes a power frequency side control model, a low-frequency side control model and a frequency active support control model. The power frequency side control model is used to perform power frequency coordinated optimization control on the operating parameters to obtain the power frequency control command and the target system frequency. The target system frequency and the operating parameters are subjected to low-frequency coordinated optimization control through the low-frequency side control model to obtain low-frequency control commands. The frequency support optimization control of the wind turbine is performed by the frequency active support control model to obtain the additional power command. The power frequency control command, the low frequency control command, and the additional power command are used to control the power of the offshore wind power flexible low frequency transmission system. The power frequency side control model includes a first phase-locked loop, a first difference arithmetic unit, a frequency transfer coefficient unit, a first current inner loop controller, a voltage outer loop controller, and a first converter. The operating parameters include power frequency side current and power frequency side voltage. The step of using the power frequency side control model to perform power frequency coordinated optimization control on the operating parameters to obtain power frequency control commands and the target system frequency includes: The power frequency side current is optimized and controlled by phase-locked loop through the first phase-locked loop to obtain the system frequency and the first phase value. The first difference calculation is performed on the system frequency and the pre-acquired rated frequency of the power frequency system by the first difference calculation to obtain the first difference; The frequency transfer coefficient is used to correct the first difference to obtain the target system frequency; The voltage outer loop controller performs voltage optimization control on the pre-acquired DC voltage value and DC voltage control command value to obtain the power frequency current control parameters; Based on the first phase value, the power frequency side current and the power frequency side voltage are subjected to coordinate transformation operation by the first converter to obtain the power frequency component parameters; The first current inner loop controller is used to perform current optimization control on the power frequency current control parameters and the power frequency component parameters to obtain the power frequency control command.

2. The frequency control method for the offshore wind power flexible low-frequency transmission system according to claim 1, characterized in that, The voltage outer loop controller includes a second differential calculator, a first PI controller, and a first reactive power controller. The step of performing voltage optimization control on the pre-acquired DC voltage value and DC voltage control command value through the voltage outer loop controller to obtain the power frequency current control parameters includes: The second difference calculator performs a difference calculation on the pre-acquired DC voltage value and the DC voltage control command value to obtain the DC voltage deviation; The DC voltage deviation is corrected by the first PI controller to obtain the first current control reference value; The first reactive power controller is used to perform reactive power optimization operation to obtain a second current control reference value, and the first current control reference value and the second current control reference value are used as power frequency current control parameters.

3. The frequency control method for the offshore wind power flexible low-frequency transmission system according to claim 1, characterized in that, The operating parameters also include low-frequency side voltage and low-frequency side current. The low-frequency side control model includes a third difference arithmetic unit, an integral arithmetic unit, a second converter, a low-frequency voltage controller, and a second current inner loop controller. The step of performing low-frequency coordinated optimization control on the target system frequency and the operating parameters through the low-frequency side control model to obtain low-frequency control commands includes: The third difference calculator performs a difference calculation between the preset low-frequency system rated frequency and the target system frequency to obtain the system frequency deviation. The system frequency deviation is integrated by the integrator to obtain the low-frequency side system control phase. Based on the low-frequency side system control phase, the low-frequency side voltage and low-frequency side current are subjected to coordinate transformation operation through the second converter to obtain low-frequency component parameters; The low-frequency voltage controller is used to perform voltage optimization control on the pre-acquired AC voltage value and AC voltage control reference value to obtain low-frequency current control parameters; The second current inner loop controller is used to perform current optimization control on the low-frequency component parameters and the low-frequency current control parameters to obtain low-frequency control commands.

4. The frequency control method for the offshore wind power flexible low-frequency transmission system according to claim 3, characterized in that, The low-frequency voltage controller includes a fourth differential operator, a second PI controller, and a second reactive power controller. The step of using the low-frequency voltage controller to perform voltage optimization control on the pre-acquired AC voltage value and AC voltage control reference value to obtain low-frequency current control parameters includes: The AC voltage deviation is obtained by performing a difference calculation on the pre-acquired AC voltage value and the AC voltage control reference value through the fourth difference calculation unit. The AC voltage deviation is corrected by the second PI controller to obtain the third current control reference value; The second reactive power controller is used to perform reactive power optimization operation to obtain a fourth current control reference value, and the third current control reference value and the fourth current control reference value are used as low-frequency current control parameters.

5. The frequency control method for the offshore wind power flexible low-frequency transmission system according to claim 1, characterized in that, The step of performing frequency support optimization control on the wind turbine frequency through the frequency active support control model to obtain the additional power command includes: The frequency of the wind turbine is input into the frequency active support control model, wherein the frequency active support control model includes a second phase-locked loop, a virtual inertia controller, a frequency droop power controller, and an adder. The frequency of the wind turbine is obtained by performing phase-locked synchronization optimization control on the wind turbine side through the second phase-locked loop. The virtual inertia controller is used to optimize the wind turbine frequency to obtain the first additional power. The virtual inertia controller includes a differential arithmetic unit and a virtual inertia coefficient unit connected in sequence. The frequency droop power controller is used to optimize the frequency droop control of the wind turbine side frequency to obtain the second additional power. The first additional power and the second additional power are summed by the summing arithmetic unit to obtain the additional power command.

6. A frequency control system for a flexible low-frequency transmission system for offshore wind power, based on the frequency control method for the flexible low-frequency transmission system for offshore wind power according to any one of claims 1-5, characterized in that, include: The acquisition module is used to acquire the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine, and input the operating parameters and the frequency of the wind turbine into a preset frequency support control model. The frequency support control model includes a power frequency side control model, a low-frequency side control model and a frequency active support control model. The power frequency control module is used to perform power frequency coordinated optimization control on the operating parameters using the power frequency side control model to obtain power frequency control commands and target system frequency; The low-frequency control module is used to perform low-frequency coordinated optimization control on the target system frequency and the operating parameters through the low-frequency side control model to obtain low-frequency control commands; The frequency control module is used to perform frequency support optimization control on the frequency of the wind turbine through the frequency active support control model to obtain additional power commands; The control module is used to perform power control on the offshore wind power flexible low-frequency transmission system using the power frequency control command, the low-frequency control command, and the additional power command.

7. An electronic device, characterized in that, The system includes a memory and a processor. The memory stores a computer program, which, when executed by the processor, causes the processor to perform the steps of the frequency control method for the offshore wind power flexible low-frequency transmission system as described in any one of claims 1-5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed, it implements the frequency control method of the offshore wind power flexible low-frequency transmission system as described in any one of claims 1-5.

9. A computer program product, characterized in that, The computer program product includes a computer program stored on a non-transitory computer-readable storage medium, the computer program including program instructions, wherein when the program instructions are executed by a computer, the computer performs the frequency control method for the offshore wind power flexible low-frequency transmission system as described in any one of claims 1-5.

Images