Frequency control method and system for offshore wind power flexible low-frequency sending-out system

Abstract

The invention discloses a frequency control method and system for an offshore wind power flexible low-frequency sending-out system, and relates to the technical field of power system frequency supporting. The working condition parameters are subjected to power frequency coordinated optimization control through a power frequency side control model to obtain a power frequency control instruction and a target system frequency, and the target system frequency and the working condition parameters are subjected to low-frequency coordinated optimization control through a low-frequency side control model to obtain a low-frequency control instruction; and performing frequency support optimization control on the frequency of the wind turbine generator through the active frequency support control model to obtain an additional power instruction, and performing power control on the offshore wind power flexible low-frequency sending-out system by adopting a power frequency control instruction, a low-frequency control instruction and the additional power instruction. The technical problems that the actual frequency deviates from a rated working point and the system control difficulty is increased due to the fact that the frequency control of the system is realized through the flexible low-frequency grid-connected frequency coordination control system by offshore wind power in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power system frequency support, and in particular to a frequency control method and system for an offshore wind power flexible low-frequency transmission system. Background Art

[0002] With the help of power electronics technology, the operating frequency (usually 20Hz) of the flexible low-frequency transmission system is lower than the industrial frequency, the line impedance is reduced, the line voltage drop and charging power are small, and the cable current carrying capacity is increased, which can significantly improve the transmission capacity. At the same time, it has the advantages of current zero-crossing breaking and easy networking. In addition, the wind turbines in the flexible low-frequency transmission system can directly output low-frequency electricity without adding frequency conversion stations, which reduces costs. However, with the continuous increase in the penetration rate of renewable energy such as offshore wind power, the frequency stability problem faced by the power system has gradually become prominent. Active frequency support for the flexible low-frequency transmission system of offshore wind power is one of the effective means to alleviate the frequency stability problem. Therefore, it is urgent to propose a frequency control method for the flexible low-frequency transmission system of offshore wind power.

[0003] At present, the existing technology mainly realizes the frequency control of the offshore wind power flexible low-frequency transmission system through the offshore wind power flexible direct current grid-connected frequency coordination control system with communication coordination control and without communication coordination control. However, this will cause the actual frequency to deviate greatly from the rated operating point, increasing the control difficulty of the offshore wind power flexible low-frequency transmission system. Summary of the invention

[0004] The present invention provides a frequency control method and system for an offshore wind power flexible low-frequency transmission system, which solves the technical problem that the prior art mainly realizes the frequency control of the offshore wind power flexible low-frequency transmission system through a flexible direct current grid-connected frequency coordination control system with or without communication coordination control, but this will cause the actual frequency to deviate significantly from the rated operating point, thereby increasing the control difficulty of the offshore wind power flexible low-frequency transmission system.

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

[0006] Obtaining the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine generator set, and inputting the operating parameters and the frequency of the wind turbine generator set into a preset frequency support control model, wherein 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 condition parameters to obtain a power frequency control instruction and a target system frequency;

[0008] Performing low-frequency coordinated optimization control on the target system frequency and the operating condition parameters through the low-frequency side control model to obtain a low-frequency control instruction;

[0009] Performing frequency support optimization control on the frequency of the wind turbine generator set through the frequency active support control model to obtain an additional power instruction;

[0010] The power frequency control instruction, the low frequency control instruction and the additional power instruction 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 operator, a frequency transfer coefficient device, a first current inner loop controller, a voltage outer loop controller and a first converter, the operating condition parameters include a power frequency side current and a power frequency side voltage, and the step of using the power frequency side control model to perform power frequency coordinated optimization control on the operating condition parameters to obtain a power frequency control instruction and a target system frequency includes:

[0012] Performing phase-locked synchronous optimization control on the power frequency side current through the first phase-locked loop to obtain a system frequency and a first phase value;

[0013] Performing a difference operation on the system frequency and the pre-acquired rated frequency of the power frequency system by the first difference operator to obtain a first difference;

[0014] Using the frequency transfer coefficient device to perform frequency correction on the first difference to obtain a target system frequency;

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

[0016] Based on the first phase value, performing a coordinate transformation operation on the power frequency side current and the power frequency side voltage through the first converter to obtain a power frequency component parameter;

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

[0018] Optionally, the voltage outer loop controller includes a second difference operator, a first PI controller and a first reactive controller, and the step of performing voltage optimization control on the pre-acquired DC voltage value and the DC voltage control instruction value by the voltage outer loop controller to obtain the power frequency current control parameter includes:

[0019] The second difference operator performs a difference operation on the pre-acquired DC voltage value and the DC voltage control instruction value to obtain a DC voltage deviation;

[0020] Correcting the DC voltage deviation by using the first PI controller to obtain a 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 a low-frequency side voltage and a low-frequency side current, the low-frequency side control model includes a third difference operator, an integral operator, a second converter, a low-frequency voltage controller, and a second current inner loop controller, and 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 a low-frequency control instruction includes:

[0023] Performing a difference operation on the preset low-frequency system rated frequency and the target system frequency through the third difference operator to obtain a system frequency deviation;

[0024] Performing an integration operation on the system frequency deviation by the integration operator to obtain a low-frequency side system control phase;

[0025] Based on the low-frequency side system control phase, the second converter performs a coordinate transformation operation on the low-frequency side voltage and the low-frequency side current to obtain a low-frequency component parameter;

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

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

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

[0029] The fourth difference operator performs a difference operation on the pre-acquired AC voltage value and the AC voltage control reference value to obtain an AC voltage deviation;

[0030] Correcting the AC voltage deviation by the second PI controller to obtain a third current control reference value;

[0031] The second reactive controller is used to perform reactive 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 frequency of the wind turbine generator set through the frequency active support control model to obtain an additional power instruction includes:

[0033] Inputting 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 a summing operator;

[0034] Performing phase-locked synchronization optimization control on the frequency of the wind turbine generator set by using the second phase-locked loop to obtain a wind turbine generator set side frequency;

[0035] The virtual inertia controller is used to optimize the wind turbine frequency at the wind turbine generator set side to obtain a first additional power, wherein the virtual inertia controller includes a differential operator and a virtual inertia coefficient unit connected in sequence;

[0036] Using the frequency droop power controller to perform frequency droop optimization control on the frequency at the wind turbine side to obtain a second additional power;

[0037] The first additional power and the second additional power are added by the adding operator to obtain an additional power instruction.

[0038] A second aspect of the present invention provides a frequency control system for an offshore wind power flexible low-frequency transmission system, comprising:

[0039] An acquisition module is used to obtain the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine generator set, and input the operating parameters and the frequency of the wind turbine generator set into a preset frequency support control model, wherein 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] A power frequency control module, used to perform power frequency coordinated optimization control on the operating parameters using the power frequency side control model to obtain a power frequency control instruction and a target system frequency;

[0041] A low-frequency control module, used for performing low-frequency coordinated optimization control on the target system frequency and the operating condition parameters through the low-frequency side control model to obtain a low-frequency control instruction;

[0042] A frequency control module, used for performing frequency support optimization control on the frequency of the wind turbine generator set through the frequency active support control model to obtain an additional power instruction;

[0043] A control module is used to use the industrial frequency control instruction, the low frequency control instruction and the additional power instruction to control the power of the offshore wind power flexible low frequency transmission system.

[0044] A third aspect of the present invention provides an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the frequency control method of the offshore wind power flexible low-frequency transmission system as described in any one of the above items.

[0045] A fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements a frequency control method for an offshore wind power flexible low-frequency transmission system as described in any one of the above items.

[0046] A fifth aspect of the present invention provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer executes the frequency control method for the offshore wind power flexible low-frequency transmission system as described in any one of the above items.

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

[0048] The frequency control of the offshore wind power flexible low-frequency transmission system is carried out through the preset frequency support control model, and the corresponding power frequency control command, low frequency control command and additional power command are obtained. The frequency control of the offshore wind power flexible low-frequency transmission system can be realized without communication coordination control and non-communication coordination control, which overcomes the technical problem that the existing technology mainly realizes the frequency control of the offshore wind power flexible low-frequency transmission system through the flexible direct current grid-connected frequency coordination control system with communication coordination control and non-communication coordination control, but this will cause the actual frequency to deviate greatly from the rated working point, increasing the control difficulty of the offshore wind power flexible low-frequency transmission system. The present invention controls the frequency of the offshore wind power flexible low-frequency transmission system by obtaining the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine set, and obtains the corresponding power frequency control command, low frequency control command and additional power command. The system is regulated by the power frequency control command and the low frequency control command so that the low frequency side of the system changes in accordance with the power frequency side, and then the system is provided with active support control through the additional power command, which reduces the control difficulty of the offshore wind power flexible low-frequency transmission system and improves the reliability of the operation of the offshore wind power flexible low-frequency transmission system. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

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

[0051] Figure 2 A flow chart of the steps of a frequency control method for an offshore wind power flexible low-frequency transmission system provided in Embodiment 2 of the present invention;

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

[0053] Figure 4 A structural block diagram of a frequency control system of an offshore wind power flexible low-frequency transmission system 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 DESCRIPTION

[0055] An embodiment of the present invention provides a frequency control method for an offshore wind power flexible low-frequency transmission system, which is used to solve the technical problem that the prior art mainly realizes the frequency control of the offshore wind power flexible low-frequency transmission system through a flexible direct current grid-connected frequency coordination control system with or without communication coordination control, but this will cause the actual frequency to deviate significantly from the rated operating point, thereby increasing the control difficulty of the offshore wind power flexible low-frequency transmission system.

[0056] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] See also Figure 1 , Figure 1 A flow chart of the steps of a frequency control method for an offshore wind power flexible low-frequency transmission system provided in Embodiment 1 of the present invention.

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

[0059] Step 101, obtaining the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine generator set, and inputting the operating parameters and the frequency of the wind turbine generator set into a preset frequency support control model, wherein 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;

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

[0061] In an embodiment of the present invention, the power frequency side PCC point grid-connected voltage, power frequency side PCC point grid-connected current, low frequency side PCC point grid-connected voltage, low frequency side PCC point grid-connected current and wind turbine frequency of the offshore wind power flexible low frequency transmission system are obtained, and the power frequency side PCC point grid-connected voltage, power frequency side PCC point grid-connected current, low frequency side PCC point grid-connected voltage, low frequency side PCC point grid-connected current and wind turbine frequency 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 a power frequency control instruction and a target system frequency;

[0063] In an embodiment of the present invention, the grid-connected voltage and grid-connected current of the power frequency side PCC point of the operating condition parameters are input into the power frequency side control model for power frequency coordinated optimization control to obtain the power frequency control instruction and the target system frequency. The power frequency side control model includes a first phase-locked loop, a first difference operator, a frequency transfer coefficient, 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 through the low-frequency side control model to obtain a low-frequency control instruction;

[0065] In the embodiment of the present 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 a low-frequency control instruction. The low-frequency side control model includes a third difference operator, an integral operator, 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 frequency of the wind turbine generator set through the frequency active support control model to obtain an additional power instruction;

[0067] In the embodiment of the present invention, the frequency of the wind turbine generator set is input into the frequency active support control model to perform frequency support optimization control to obtain an additional power instruction.

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

[0069] In an embodiment of the present invention, industrial frequency control instructions and low frequency control instructions are used to perform power regulation on the onshore frequency conversion station of the offshore wind power flexible low frequency transmission system, and additional power instructions are used to perform active frequency support control on the wind turbines of the offshore wind power flexible low frequency transmission system.

[0070] In an embodiment of the present invention, the 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 industrial frequency control instructions, low-frequency control instructions and additional power instructions. The frequency control of the offshore wind power flexible low-frequency transmission system can be achieved without communication coordination control and non-communication coordination control. This overcomes the technical problem that the prior art mainly realizes the frequency control of the offshore wind power flexible low-frequency transmission system through the offshore wind power flexible direct current grid-connected frequency coordination control system with communication coordination control and non-communication coordination control, but 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. The present invention controls the frequency of the offshore wind power flexible low-frequency transmission system by acquiring the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine generator set, and obtains corresponding power frequency control instructions, low-frequency control instructions and additional power instructions. The power frequency control instructions and low-frequency control instructions are used to regulate the system so that the changes of the low-frequency side of the system are consistent with the power frequency side. The additional power instructions are used to provide active support control for the system, which reduces the control difficulty of the offshore wind power flexible low-frequency transmission system and improves the reliability of the operation of the offshore wind power flexible low-frequency transmission system.

[0071] See also Figure 2 , Figure 2 A flow chart of the steps of a frequency control method for an offshore wind power flexible low-frequency transmission system provided in Embodiment 2 of the present invention.

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

[0073] Step 201, obtaining the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine generator set, and inputting the operating parameters and the frequency of the wind turbine generator set into a preset frequency support control model, wherein 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;

[0074] In the embodiment of the present invention, refer to Figure 3As shown in the figure, the wind turbine frequency f in the offshore wind power flexible low-frequency transmission system is obtained. Pw , the grid-connected voltage u of the power frequency side PCC points on both sides of the onshore frequency conversion station D , the grid-connected current i of the PCC point on the power frequency side D , low frequency side PCC point grid voltage u D and the grid-connected current i of the PCC point on the low-frequency side D , and input a preset frequency support control model, wherein 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.

[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 a power frequency control instruction and a 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 operator, a frequency transfer coefficient device, a first current inner loop controller, a voltage outer loop controller and a first converter, and the operating parameters include the power frequency side current and the power frequency side voltage. Step 202 includes the following sub-steps:

[0078] S11, performing phase-locked synchronous optimization control on the power frequency side current through a first phase-locked loop to obtain a system frequency and a first phase value;

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

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

[0081] S12, performing a difference operation on the system frequency and the pre-acquired rated frequency of the power frequency system by a first difference operator to obtain a first difference;

[0082] In the embodiment of the present invention, the preset rated frequency of the power frequency system and the system frequency f D The first difference operator performs difference processing to obtain a first difference.

[0083] S13, using a frequency transfer coefficient device to perform frequency correction on the first difference to obtain a target system frequency;

[0084] In the embodiment of the present invention, a frequency transfer coefficient is used to convert the first difference value into a preset frequency transfer coefficient H. 0Perform multiplication processing to obtain the target system frequency.

[0085] S14, performing voltage optimization control on the pre-acquired DC voltage value and the DC voltage control command value through a voltage outer loop controller to obtain a power frequency current control parameter;

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

[0087] S141, performing a difference operation on the pre-acquired DC voltage value and the DC voltage control instruction value by a second difference operator to obtain a DC voltage deviation;

[0088] In the embodiment of the present invention, the pre-acquired DC voltage value U dc and DC voltage control command value U dcref The second difference operator performs difference operation to obtain a DC voltage deviation.

[0089] S142, correcting the DC voltage deviation by a first PI controller to obtain a first current control reference value;

[0090] In the embodiment of the present invention, the first PI controller performs correction processing on the DC voltage deviation to obtain a first current control reference value i Ddref .

[0091] S143: Use the first reactive power controller to perform reactive power optimization operation to obtain a second current control reference value, and use the first current control reference value and the second current control reference value as power frequency current control parameters.

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

[0093] S15. Based on the first phase value, a first converter is used to perform a coordinate transformation operation on the power frequency side current and the power frequency side voltage to obtain a power frequency component parameter;

[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 The dq-axis component u Dd 、u Dq 、i Dd 、i Dq .

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

[0096] S16. Use the first current inner loop controller to perform current optimization control on the power frequency current control parameter and the power frequency component parameter to obtain a power frequency control instruction.

[0097] In the embodiment of the present invention, the power frequency current control parameter and the power frequency component parameter are input into the first current inner loop controller to perform current optimization control to obtain the power frequency control instruction.

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

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

[0100] S21, performing a difference operation on a preset low-frequency system rated frequency and a target system frequency through a third difference operator to obtain a system frequency deviation;

[0101] In the embodiment of the present invention, the preset low-frequency system rated frequency f Pref The target system frequency is input into the third difference operator for difference operation to obtain the system frequency deviation f P .

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

[0103]

[0104] S22, performing an integration operation on the system frequency deviation through an integration operator to obtain a low-frequency side system control phase;

[0105] In the embodiment of the present invention, the system frequency deviation is integrated by the 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 the low-frequency side current are subjected to coordinate transformation operation by a second converter to obtain low-frequency component parameters;

[0107] The low-frequency component parameter refers to the grid-connected voltage u at the PCC point on the low-frequency side. P 、Current i PThe dq-axis component u Pd 、u Pq 、i Pd 、i Pq .

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

[0109] S24, using a low-frequency voltage controller to perform voltage optimization control on the pre-acquired AC voltage value and the AC voltage control reference value to obtain a low-frequency current control parameter;

[0110] Further, the low-frequency voltage controller includes a fourth difference operator, a second PI controller and a second reactive controller, and S24 includes the following sub-steps:

[0111] S241, performing a difference operation on the pre-acquired AC voltage value and the AC voltage control reference value through a fourth difference operator to obtain an AC voltage deviation;

[0112] In the embodiment of the present invention, the pre-acquired AC voltage value U ac And AC voltage control reference value U acref The voltage is input into the fourth difference operator to perform difference operation to obtain an AC voltage deviation.

[0113] S242, correcting the AC voltage deviation by a second PI controller to obtain a third current control reference value;

[0114] In the embodiment of the present invention, the second PI controller corrects the AC voltage deviation to obtain a third current control reference value i Pdref .

[0115] S243: Use the second reactive power controller to perform reactive power optimization operation to obtain a fourth current control reference value, and use the third current control reference value and the fourth current control reference value as low-frequency current control parameters.

[0116] In the embodiment of the present invention, the fourth current control reference value i is generated by the second reactive power controller. Pqref and taking the third current control reference value and the fourth current control reference value as low-frequency current control parameters.

[0117] S25. Use the second current inner loop controller to perform current optimization control on the low-frequency component parameters and the low-frequency current control parameters to obtain a low-frequency control instruction.

[0118] In the embodiment of the present invention, the low-frequency component parameter and the low-frequency current control parameter are input into the second current inner loop controller to perform current optimization control to obtain a low-frequency control instruction.

[0119] Step 204, inputting the frequency of the wind turbine generator set into a 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 a summing operator;

[0120] In an embodiment of the present invention, the frequency of the wind turbine generator set is subjected to frequency support optimization control through a frequency active support control model, wherein, referring to 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 a summing operator.

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

[0122] In the embodiment of the present invention, the wind turbine frequency is input into 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 at the wind turbine generator set side to obtain a first additional power, wherein the virtual inertia controller includes a differential operator and a virtual inertia coefficient unit connected in sequence;

[0124] In the embodiment of the present invention, the wind turbine side frequency is optimized and controlled by the differential operator and the virtual inertia coefficient device in sequence to obtain the first additional power. .

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

[0126]

[0127] in, is the absolute value of the frequency change rate of the wind turbine, m is the power exponent of the frequency change rate, is the reference value of the virtual inertia constant of the wind turbine, is the incremental coefficient of the virtual inertia constant of the wind turbine, The dead zone value for measuring the frequency change rate of the wind turbine.

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

[0129]

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

[0131] In the embodiment of the present invention, the frequency of the wind turbine generator set is input into the frequency droop power controller for frequency droop optimization control to obtain the second additional power .

[0132]

[0133] in, is the power-frequency droop coefficient, Measure frequency reference values ​​for wind turbine groups.

[0134] Step 208: The first additional power and the second additional power are added by a summing operator to obtain an additional power instruction.

[0135] In the embodiment of the present invention, the first additional power and the second additional power are input to the summing operator for summing operation to obtain the additional power instruction .

[0136]

[0137] Step 209: Use the industrial frequency control command, the low frequency control command and the additional power command to perform power control on the offshore wind power flexible low frequency transmission system.

[0138] In the embodiment of the present invention, an additional power instruction is used to perform frequency active support additional control on the wind turbines of the offshore wind power flexible low-frequency transmission system, and the power frequency control instruction and the low-frequency control instruction are respectively input into the PMW modulator for conversion to obtain the power frequency control signal and the low-frequency control signal. The power frequency control signal and the low-frequency control signal are used to perform power control on the onshore frequency conversion station of the offshore wind power flexible low-frequency transmission system.

[0139] In an embodiment of the present invention, the 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 industrial frequency control instructions, low-frequency control instructions and additional power instructions. The frequency control of the offshore wind power flexible low-frequency transmission system can be achieved without communication coordination control and non-communication coordination control. This overcomes the technical problem that the prior art mainly realizes the frequency control of the offshore wind power flexible low-frequency transmission system through the offshore wind power flexible direct current grid-connected frequency coordination control system with communication coordination control and non-communication coordination control, but 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. The present invention controls the frequency of the offshore wind power flexible low-frequency transmission system by acquiring the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine generator set, and obtains corresponding power frequency control instructions, low-frequency control instructions and additional power instructions. The power frequency control instructions and low-frequency control instructions are used to regulate the system so that the changes of the low-frequency side of the system are consistent with the power frequency side. The additional power instructions are used to provide active support control for the system, which reduces the control difficulty of the offshore wind power flexible low-frequency transmission system and improves the reliability of the operation of the offshore wind power flexible low-frequency transmission system.

[0140] See also Figure 4 , Figure 4 This is a structural block diagram of a frequency control system of an offshore wind power flexible low-frequency transmission system provided in Example 3 of the present invention.

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

[0142] The acquisition module 301 is used to obtain the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine generator set, and input the operating parameters and the frequency of the wind turbine generator set into a preset frequency support control model, wherein 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 to obtain the power frequency control instruction 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 a low-frequency control instruction;

[0145] The frequency control module 304 is used to perform frequency support optimization control on the frequency of the wind turbine generator set through a frequency active support control model to obtain an additional power instruction;

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

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

[0148] A first synchronization submodule, used for performing phase-locked synchronization optimization control on the power frequency side current through a first phase-locked loop to obtain a system frequency and a first phase value;

[0149] A first deviation submodule, configured to perform a difference operation on the system frequency and a pre-acquired rated frequency of the power frequency system through a first difference operator to obtain a first difference;

[0150] A first correction submodule, configured to perform frequency correction on the first difference using a frequency transfer coefficient device to obtain a target system frequency;

[0151] A first voltage optimization submodule is used to perform voltage optimization control on a pre-acquired DC voltage value and a DC voltage control instruction value through a voltage outer loop controller to obtain an industrial frequency current control parameter;

[0152] A first conversion submodule, configured to perform a coordinate transformation operation on the power frequency side current and the power frequency side voltage through a first converter based on the first phase value to obtain a power frequency component parameter;

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

[0154] Furthermore, the voltage outer loop controller includes a second difference operator, a first PI controller and a first reactive power controller, and a first voltage optimization submodule, including:

[0155] A first deviation unit, configured to perform a difference operation on a pre-acquired DC voltage value and a DC voltage control instruction value through a second difference operator to obtain a DC voltage deviation;

[0156] A first calibration unit, configured to perform correction processing on a DC voltage deviation through a first PI controller to obtain a first current control reference value;

[0157] The first reactive power optimization unit is used to perform reactive power optimization operation by using the first reactive power controller to obtain a second current control reference value, and use 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 the low-frequency side voltage and the low-frequency side current. The low-frequency side control model includes a third difference operator, an integral operator, a second converter, a low-frequency voltage controller and a second current inner loop controller. The low-frequency control module 303 includes:

[0159] A second deviation submodule, configured to perform a difference operation on a preset low-frequency system rated frequency and a target system frequency through a third difference operator to obtain a system frequency deviation;

[0160] The integral submodule is used to perform an integral operation on the system frequency deviation through an integral operator to obtain a control phase of the low-frequency side system;

[0161] A second transformation submodule is used to control the phase based on the low-frequency side system, and to perform a coordinate transformation operation on the low-frequency side voltage and the low-frequency side current through a second converter to obtain a low-frequency component parameter;

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

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

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

[0165] a second deviation unit, configured to perform a difference operation on a pre-acquired AC voltage value and an AC voltage control reference value through a fourth difference operator to obtain an AC voltage deviation;

[0166] A second correction unit, configured to correct the AC voltage deviation through a second PI controller to obtain a third current control reference value;

[0167] The second reactive power optimization unit is used to perform reactive power optimization operation by using the second reactive power controller to obtain a fourth current control reference value, and use 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] An input submodule, used for inputting the frequency of the wind turbine generator set into a 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 a summing operator;

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

[0171] The wind turbine optimization submodule is used to optimize the wind turbine control on the wind turbine side frequency by using a virtual inertia controller to obtain a first additional power, wherein the virtual inertia controller includes a differential operator and a virtual inertia coefficient unit connected in sequence;

[0172] A frequency droop optimization submodule, used to perform frequency droop optimization control on the frequency of the wind turbine generator set side by using a frequency droop power controller to obtain a second additional power;

[0173] The adding submodule is used to perform a summing process on the first additional power and the second additional power through a summing operator to obtain an additional power instruction.

[0174] See also 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 comprises: a memory 401 and a processor 402, wherein the memory 402 stores a computer program; when the computer program is executed by the processor 402, the processor 402 executes a frequency control method for an offshore wind power flexible low-frequency transmission system according to any of the above embodiments.

[0176] The memory 401 may be an electronic memory such as a flash memory, an EEPROM (electrically erasable programmable read-only memory), an EPROM, a hard disk or a ROM. The memory 401 has a storage space 403 for a program code 413 for executing any method step in the above method. For example, the storage space 403 for the program code may include individual program codes 413 for implementing the various steps in the above method, respectively. These program codes may be read from or written to one or more computer program products. These computer program products include program code carriers such as a hard disk, a compact disk (CD), a memory card or a floppy disk. The program code may be compressed, for example, in an appropriate form. When these codes are run by a computing and processing device, the computing and processing device is caused to execute the various steps in the above-described method.

[0177] Embodiment 5 of the present invention further provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, a frequency control method for an offshore wind power flexible low-frequency transmission system as in any of the above embodiments is implemented.

[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, and the computer program includes program instructions. When the program instructions are executed by a computer, the computer executes the frequency control method of the offshore wind power flexible low-frequency transmission system as described in any of the above embodiments.

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

[0180] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

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

[0182] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0183] If the integrated unit is implemented in the form of 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. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0184] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A frequency control method for an offshore wind power flexible low-frequency transmission system, characterized in that: include: Obtaining the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine generator set, and inputting the operating parameters and the frequency of the wind turbine generator set into a preset frequency support control model, wherein 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 condition parameters to obtain a power frequency control instruction and a target system frequency; Performing low-frequency coordinated optimization control on the target system frequency and the operating condition parameters through the low-frequency side control model to obtain a low-frequency control instruction; Performing frequency support optimization control on the frequency of the wind turbine generator set through the frequency active support control model to obtain an additional power instruction; The power frequency control instruction, the low frequency control instruction and the additional power instruction are used to control the power of the offshore wind power flexible low frequency transmission system.

2. The frequency control method of the offshore wind power flexible low-frequency transmission system according to claim 1 is characterized in that: The power frequency side control model includes a first phase-locked loop, a first difference operator, a frequency transfer coefficient device, a first current inner loop controller, a voltage outer loop controller and a first converter, the operating condition parameters include power frequency side current and power frequency side voltage, and the step of using the power frequency side control model to perform power frequency coordinated optimization control on the operating condition parameters to obtain a power frequency control instruction and a target system frequency includes: Performing phase-locked synchronous optimization control on the power frequency side current through the first phase-locked loop to obtain a system frequency and a first phase value; Performing a difference operation on the system frequency and the pre-acquired rated frequency of the power frequency system by the first difference operator to obtain a first difference; Using the frequency transfer coefficient device to perform frequency correction on the first difference to obtain a target system frequency; The voltage outer loop controller performs voltage optimization control on the pre-acquired DC voltage value and the DC voltage control command value to obtain the power frequency current control parameter; Based on the first phase value, performing a coordinate transformation operation on the power frequency side current and the power frequency side voltage through the first converter to obtain a power frequency component parameter; The first current inner loop controller is used to perform current optimization control on the power frequency current control parameter and the power frequency component parameter to obtain a power frequency control instruction.

3. The frequency control method of the offshore wind power flexible low-frequency transmission system according to claim 2 is characterized in that: The voltage outer loop controller includes a second difference operator, a first PI controller and a first reactive controller. The step of performing voltage optimization control on a pre-acquired DC voltage value and a DC voltage control instruction value by the voltage outer loop controller to obtain a power frequency current control parameter includes: The second difference operator performs a difference operation on the pre-acquired DC voltage value and the DC voltage control instruction value to obtain a DC voltage deviation; Correcting the DC voltage deviation by using the first PI controller to obtain a 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.

4. The frequency control method of the offshore wind power flexible low-frequency transmission system according to claim 1 is characterized in that: The operating parameters also include a low-frequency side voltage and a low-frequency side current. The low-frequency side control model includes a third difference operator, an integral operator, 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 a low-frequency control instruction includes: Performing a difference operation on the preset low-frequency system rated frequency and the target system frequency through the third difference operator to obtain a system frequency deviation; Performing an integration operation on the system frequency deviation by the integration operator to obtain a low-frequency side system control phase; Based on the low-frequency side system control phase, the second converter performs a coordinate transformation operation on the low-frequency side voltage and the low-frequency side current to obtain a low-frequency component parameter; The low-frequency voltage controller is used to perform voltage optimization control on the pre-acquired AC voltage value and the AC voltage control reference value to obtain a low-frequency current control parameter; The second current inner loop controller is used to perform current optimization control on the low-frequency component parameter and the low-frequency current control parameter to obtain a low-frequency control instruction.

5. The frequency control method of the offshore wind power flexible low-frequency transmission system according to claim 4 is characterized in that: The low-frequency voltage controller includes a fourth difference operator, a second PI controller and a second reactive controller. The step of using the low-frequency voltage controller to perform voltage optimization control on the pre-acquired AC voltage value and the AC voltage control reference value to obtain the low-frequency current control parameter includes: The fourth difference operator performs a difference operation on the pre-acquired AC voltage value and the AC voltage control reference value to obtain an AC voltage deviation; Correcting the AC voltage deviation by the second PI controller to obtain a third current control reference value; The second reactive controller is used to perform reactive 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.

6. The frequency control method of 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 frequency of the wind turbine generator set through the frequency active support control model to obtain an additional power instruction includes: Inputting 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 a summing operator; Performing phase-locked synchronization optimization control on the frequency of the wind turbine generator set by using the second phase-locked loop to obtain a wind turbine generator set side frequency; The virtual inertia controller is used to optimize the wind turbine frequency at the wind turbine generator set side to obtain a first additional power, wherein the virtual inertia controller includes a differential operator and a virtual inertia coefficient unit connected in sequence; Using the frequency droop power controller to perform frequency droop optimization control on the frequency at the wind turbine side to obtain a second additional power; The first additional power and the second additional power are added by the adding operator to obtain an additional power instruction.

7. A frequency control system for an offshore wind power flexible low-frequency transmission system, characterized in that: include: An acquisition module is used to obtain the operating parameters of the offshore wind power flexible low-frequency transmission system and the frequency of the wind turbine generator set, and input the operating parameters and the frequency of the wind turbine generator set into a preset frequency support control model, wherein 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; A power frequency control module, used to perform power frequency coordinated optimization control on the operating parameters using the power frequency side control model to obtain a power frequency control instruction and a target system frequency; A low-frequency control module, used for performing low-frequency coordinated optimization control on the target system frequency and the operating condition parameters through the low-frequency side control model to obtain a low-frequency control instruction; A frequency control module, used for performing frequency support optimization control on the frequency of the wind turbine generator set through the frequency active support control model to obtain an additional power instruction; A control module is used to use the industrial frequency control instruction, the low frequency control instruction and the additional power instruction to control the power of the offshore wind power flexible low frequency transmission system.

8. An electronic device, characterized in that: It includes a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor executes the steps of the frequency control method of the offshore wind power flexible low-frequency transmission system as described in any one of claims 1-6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the frequency control method of the offshore wind power flexible low-frequency transmission system as described in any one of claims 1-6 is implemented.

10. A computer program product, characterized in that The computer program product includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer executes the frequency control method for the offshore wind power flexible low-frequency transmission system as described in any one of claims 1-6.

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