Wind farm coordinated support method for grid connection point voltage and frequency and related device

Abstract

The present invention relates to the field of power grids and provides a method and related device for collaboratively supporting the voltage and frequency of a wind farm at a grid connection point. A discretized grid frequency response model during a grid fault is constructed based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-voltage cylinder power coefficient, and reheater time constant of synchronous generators within the grid. A collaborative support model for the voltage and frequency of the wind farm at the grid connection point during a grid fault is constructed based on the grid frequency response model and the grid equivalent circuit during the grid fault. Based on the collaborative support model, current commands for each generator in the wind farm are calculated and generated, and each generator is controlled to operate according to its respective current command to collaboratively support the frequency and voltage of the grid connection point. The present invention actively supports the recovery of grid frequency and voltage based on the parameters of the generators, avoids abnormal grid frequency and voltage caused by the fault, and improves grid stability during the fault.

Description

Technical Field

[0001] The present invention relates to the field of power grids, and in particular to a method and related device for collaboratively supporting voltage and frequency of a wind farm at a grid connection point. Background Art

[0002] As wind power accounts for an increasing proportion of power in the grid, its role and status in the power system are growing. The mutual impact between wind power and the grid has become an important issue that cannot be ignored, especially in the event of a grid failure.

[0003] Grid failures may cause the voltage at the wind farm grid connection point to drop or rise, and sometimes also cause abnormal frequency at the wind farm grid connection point. Grid failures can cause a series of transient processes to wind turbines and other wind farm electrical equipment, such as overcurrent, low voltage, and overspeed. Currently, wind turbines do not have the ability to ride through faults. Therefore, when a grid failure occurs, wind turbines will generally automatically disconnect from the grid for their own safety reasons. As the proportion of wind power in the grid continues to increase, if wind turbines do not have qualified grid failure resistance capabilities, automatically disconnecting in the event of a grid failure will increase the difficulty of recovering from local grid failures, worsen grid stability, and even aggravate failures and cause system collapse. Therefore, how to enhance the ability of wind farms to resist grid failures and maintain the stability of grid connection point voltage and frequency has become a technical problem that needs to be urgently solved by people in this field. Summary of the Invention

[0004] In view of the above problems, the present invention provides a method and related devices for collaboratively supporting the voltage and frequency of a wind farm at a grid connection point, which overcome the above problems or at least partially solve the above problems.

[0005] In a first aspect, a method for collaboratively supporting voltage and frequency at a grid connection point by a wind farm includes:

[0006] A discretized grid frequency response model during a grid fault is constructed based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant of the synchronous generator within the grid.

[0007] Constructing a coordinated support model for the voltage and frequency of the wind farm to the grid connection point during the grid fault period based on the grid frequency response model and the grid equivalent circuit during the grid fault period;

[0008] According to the collaborative support model, current instructions for each generator in the wind farm are calculated and generated, and each generator in the wind farm is controlled to operate according to its own current instruction, so as to collaboratively support the frequency and voltage of the grid connection point.

[0009] Optionally, in certain optional embodiments, constructing a discretized grid frequency response model during a grid fault period based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant of the synchronous generator within the grid includes:

[0010] A grid frequency response model is constructed based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant of the synchronous generator within the grid.

[0011] The grid frequency response model is calculated and transformed according to the change in active power of the wind farm during the grid fault period to obtain a discretized grid frequency response model during the grid fault period.

[0012] Optionally, in certain optional embodiments, constructing a grid frequency response model based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant of the synchronous generator within the grid includes:

[0013] Establishing a grid connection point frequency deviation model based on the active power-frequency transfer function of each synchronous generator within the grid and the disturbance power within the grid, wherein the active power-frequency transfer function includes: inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant; and the grid connection point frequency deviation model is a high-order complex domain expression;

[0014] Performing variable substitution on the governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant in the grid-connected point frequency deviation model;

[0015] The grid connection point frequency deviation model after variable substitution is subjected to time domain conversion to obtain the grid frequency response model, wherein the grid frequency response model is a low-order time domain expression.

[0016] Optionally, in certain optional embodiments, the calculating and transforming the grid frequency response model according to the change in active power of the wind farm during the grid fault to obtain a discretized grid frequency response model during the grid fault includes:

[0017] determining a change in the active power of the wind farm during the grid fault according to the active power of the wind farm during the grid fault and the active power of the wind farm before the grid fault;

[0018] Calculating a grid frequency response model of the wind farm in any control period according to the variation and the grid frequency response model;

[0019] The grid frequency response model of the wind farm in any control period is subjected to an inverse Laplace transform and deduced to obtain a discretized grid frequency response model during a grid fault. The discretized grid frequency response model during a grid fault represents the mathematical relationship between the deviation value of the grid frequency at the n+1th control node and the active power command of the wind farm at the nth control node.

[0020] Optionally, in certain optional embodiments, constructing a collaborative support model for voltage and frequency of the wind farm to the grid connection point during a grid fault based on the grid frequency response model and the grid equivalent circuit during a grid fault includes:

[0021] Determine the grid connection point voltage model of the wind farm during the grid fault period according to the grid equivalent circuit during the grid fault period;

[0022] Determining an optimization target model according to the grid connection point voltage model, the grid frequency response model, and the optimization target, wherein the optimization target model represents: a mathematical relationship of the optimization target at the nth control node;

[0023] Constraints are established for the optimization target model to construct a collaborative support model for the voltage and frequency of the wind farm to the grid connection point during a power grid fault, wherein the constraints include: voltage constraints, current constraints and power constraints.

[0024] Optionally, in certain optional embodiments, calculating and generating current instructions for each generator in the wind farm according to the collaborative support model, and controlling each generator in the wind farm to operate according to the respective current instructions to collaboratively support the frequency and voltage at the grid connection point includes:

[0025] Performing convex optimization on the collaborative support model to obtain a collaborative support model in a second-order cone form;

[0026] Based on the second-order cone-shaped collaborative support model, current instructions for each generator in the wind farm are calculated and generated, and each generator in the wind farm is controlled to operate according to its own current instruction to collaboratively support the frequency and voltage of the grid connection point.

[0027] Optionally, in certain optional embodiments, the collaborative support model based on the second-order cone form calculates and generates current instructions for each generator in the wind farm, and controls each generator in the wind farm to operate according to the respective current instructions to collaboratively support the frequency and voltage at the grid connection point, including:

[0028] Controlling each generator of the wind farm to follow the collaborative support model based on the second-order cone form, using a solver to perform a calculation to obtain a target current of each generator of the wind farm;

[0029] generating a current command for each generator based on the target current of each generator;

[0030] The generators in the wind farm are controlled to operate according to their respective current instructions to coordinate the frequency and voltage of the grid connection point.

[0031] In a second aspect, a wind farm collaborative support device for grid connection point voltage and frequency includes: a frequency response model construction unit, a collaborative support model construction unit, and a generator operation unit;

[0032] The frequency response model construction unit is used to construct a discretized grid frequency response model during a grid fault period based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient and reheater time constant of the synchronous generator inside the grid;

[0033] The collaborative support model construction unit is configured to construct a collaborative support model for the voltage and frequency of the wind farm to the grid connection point during a grid fault according to the grid frequency response model and the grid equivalent circuit during a grid fault;

[0034] The generator operation unit is used to calculate and generate current instructions for each generator in the wind farm according to the collaborative support model, and control each generator in the wind farm to operate according to its own current instruction to collaboratively support the frequency and voltage of the grid connection point.

[0035] In a third aspect, a computer-readable storage medium stores a program thereon, wherein when the program is executed by a processor, the method for collaboratively supporting the voltage and frequency of the grid connection point by a wind farm as described in any one of the above items is implemented.

[0036] In a fourth aspect, an electronic device comprises at least one processor, and at least one memory and bus connected to the processor; wherein the processor and the memory communicate with each other through the bus; the processor is used to call the program instructions in the memory to execute any of the above-mentioned methods for collaborative support of the voltage and frequency of the grid connection point by the wind farm.

[0037] By means of the above technical solution, the present invention provides a method and related device for collaboratively supporting the voltage and frequency of the grid connection point by a wind farm. A discretized grid frequency response model during a grid fault is constructed based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-voltage cylinder power coefficient, and reheater time constant of the synchronous generator within the grid. A collaborative support model for the voltage and frequency of the grid connection point during a grid fault is constructed based on the grid frequency response model and the grid equivalent circuit during the grid fault. Based on the collaborative support model, current instructions for each generator in the wind farm are calculated and generated, and each generator in the wind farm is controlled to operate according to its own current instruction to collaboratively support the frequency and voltage of the grid connection point. It can be seen from this that the present invention can actively support the recovery of the grid frequency and voltage based on the parameters of the generator, avoid abnormal grid frequency and voltage caused by the fault, and improve the stability of the grid during the fault.

[0038] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0040] Figure 1 A flow chart showing a method for collaboratively supporting voltage and frequency at a grid connection point by a wind farm provided by the present invention is shown;

[0041] Figure 2 The present invention shows a power grid equivalent circuit during a power grid fault period;

[0042] Figure 3 A system architecture diagram of a power grid model provided by the present invention is shown;

[0043] Figure 4 A schematic diagram of a power grid frequency waveform provided by the present invention is shown;

[0044] Figure 5 A schematic diagram showing the effective value of the grid connection point voltage provided by the present invention is shown;

[0045] Figure 6 A schematic diagram showing a reference value and an actual value of a first rotor current provided by the present invention;

[0046] Figure 7 A schematic diagram showing a first wind farm output waveform provided by the present invention is shown;

[0047] Figure 8 A schematic diagram showing a second wind farm output waveform provided by the present invention is shown;

[0048] Figure 9 A schematic diagram showing a third wind farm output waveform provided by the present invention is shown;

[0049] Figure 10 A schematic diagram showing a fourth wind farm output waveform provided by the present invention is shown;

[0050] Figure 11 A schematic diagram showing a grid frequency waveform during a fault period provided by the present invention is shown;

[0051] Figure 12 A schematic diagram showing the effective value of a grid connection point voltage provided by the present invention;

[0052] Figure 13 A schematic diagram showing a reference value and an actual value of a second rotor current provided by the present invention;

[0053] Figure 14 A schematic diagram showing a fifth wind farm output waveform provided by the present invention is shown;

[0054] Figure 15 A schematic diagram showing a sixth wind farm output waveform provided by the present invention is shown;

[0055] Figure 16 A schematic diagram showing a seventh wind farm output waveform provided by the present invention is shown;

[0056] Figure 17 A schematic diagram showing an eighth wind farm output waveform provided by the present invention is shown;

[0057] Figure 18 A schematic structural diagram of a device for collaboratively supporting voltage and frequency at a wind farm connection point provided by the present invention is shown;

[0058] Figure 19 A schematic structural diagram of an electronic device provided by the present invention is shown. DETAILED DESCRIPTION

[0059] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0060] like Figure 1 As shown, the present invention provides a method for collaboratively supporting voltage and frequency of a wind farm to a grid connection point, comprising: S100, 200 and S300;

[0061] S100, constructing a discretized grid frequency response model during a grid fault period based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant of the synchronous generator within the grid;

[0062] Optionally, the inertia time constant, also known as the inertia time constant, is a technical term used in power systems. Its physical meaning is the time required for a generator set to accelerate from a standstill to its rated speed when a unit mechanical torque is applied to the generator shaft and the output electromagnetic torque is zero. The inertia time constant reflects the generator's ability to store kinetic energy and is an important indicator of its ability to withstand disturbances (such as sudden load changes).

[0063] Optionally, the damping time constant of the present invention combines the effects of mechanical friction and electrical damping (such as damping windings). The damping time constant quantifies the system's ability to suppress frequency oscillations: the larger its value, the smaller the frequency fluctuation amplitude.

[0064] Optionally, the mechanical power proportionality coefficient, referred to in this disclosure, refers to the steady-state proportional relationship between mechanical power and electromagnetic power and is used for power balance correction in primary frequency regulation. Estimating mechanical power using thermal quantities (such as steam pressure) ensures precise governor output distribution during load disturbances, avoiding over- or under-regulation.

[0065] Optionally, the speed regulator droop coefficient mentioned in the present invention is a core parameter that determines the frequency modulation sensitivity. The smaller the droop coefficient, the greater the power compensation amount triggered by the unit frequency deviation, and the faster the response.

[0066] Optionally, the high-pressure cylinder power coefficient mentioned in the present invention refers to: the ratio of the high-pressure cylinder output power to the total power, which is affected by the flow efficiency and structural design.

[0067] Optionally, the reheater time constant mentioned in the present invention refers to the delay time of steam in the reheater system, reflecting the hysteresis characteristics of the power response of the medium and low pressure cylinders.

[0068] Optionally, the discretized grid frequency response model during a grid fault period in the present invention reflects: a function expression of the grid frequency value with respect to time or complex frequency.

[0069] Optionally, the grid frequency is related to the speed of the synchronous generators in the grid, that is, the speed of the thermal power units. The speed of the wind turbine is decoupled from the grid frequency and has no direct correlation. In engineering, the node differences of the grid frequency are generally ignored, and the grid frequency is considered to be a unified quantity. That is, the grid connection point frequency mentioned in the present invention can also be understood as the grid frequency, which is jointly determined by the speed of the thermal power units in the grid. The corresponding models can also be understood equivalently. For example, the grid connection point frequency model can also be understood as the grid frequency model, and the present invention does not limit this.

[0070] Optionally, the present invention does not limit the specific process of constructing a discretized grid frequency response model during a grid fault. For example, in some optional embodiments, the S100 includes: step 1.1 and step 1.2;

[0071] Step 1.1: Construct a grid frequency response model based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant of the synchronous generator within the grid;

[0072] For example, in some optional embodiments, the step 1.1 includes: step 2.1, step 2.2 and step 2.3;

[0073] Step 2.1: Establish a grid connection point frequency deviation model based on the active power-frequency transfer function of each synchronous generator within the grid and the disturbance power within the grid, wherein the active power-frequency transfer function includes: inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant. The grid connection point frequency deviation model is a high-order complex domain expression;

[0074] Optionally, the present invention first establishes an expression for the grid connection point frequency deviation based on the active power-frequency transfer function, as shown in the following formula 1.

[0075] Formula 1: ;

[0076] in, Represents the frequency deviation of the grid connection point, represents the active power-frequency transfer function of all synchronous generators, and represents the disturbance power in the power grid, and S is the complex frequency variable in the Laplace transform.

[0077] According to the governor and turbine model, the above formula 1 The specific expression of is shown in the following formula 2.

[0078] Formula 2: ;

[0079] Wherein, the subscript y represents the yth synchronous generator in the power grid, and m represents the number of synchronous generators in the power grid. represents the inertia time constant, Represents the damping time constant. represents the proportionality coefficient of mechanical power, represents the governor droop coefficient, Represents the high-pressure cylinder power coefficient, Represents the time constant of the reheater.

[0080] Optionally, the mechanical power refers to the mechanical power input to the thermal power unit, which together with the electromagnetic power output by the thermal power unit determines the change in the rotor speed of the thermal power unit.

[0081] Optionally, the frequency regulator, high-pressure cylinder and reheater are all common components of thermal power units: the speed regulator controls the unit speed (frequency) by adjusting the steam inlet volume (steam flow or gas flow) of the turbine to maintain the stability of the power system frequency; high-temperature and high-pressure steam (such as 600℃, 24MPa) first enters the high-pressure cylinder, drives the rotor blades to rotate, and converts thermal energy into mechanical energy. After the steam expands in the high-pressure cylinder, the pressure drops to the medium-pressure level (such as 4MPa-6MPa), and the temperature drops to about 350℃; the low-temperature and low-pressure steam discharged from the high-pressure cylinder returns to the boiler, and the reheater reheats it to a high temperature (such as 620℃), and then sends it to the medium-pressure cylinder to continue to do work. The reheat cycle increases the enthalpy of the steam, increases the total output of the turbine, and reduces the steam consumption rate.

[0082] Step 2.2, performing variable substitution on the governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant in the grid connection point frequency deviation model;

[0083] Step 2.3: Perform time domain conversion on the grid connection point frequency deviation model after variable substitution to obtain the grid frequency response model, wherein the grid frequency response model is a low-order time domain expression.

[0084] Optionally, based on Formula 2, the inertia time constant is expressed as The damping time constant is expressed as To express it, the expressions of the two are shown in the following formula 3.

[0085] Formula 3: ;

[0086] Based on the above analysis, the grid frequency response model is shown in Formula 4, where all parameters have been normalized according to a unified reference value.

[0087] Specifically, by combining Formula 1, Formula 2, and Formula 3, the expression shown in the following Formula 4 is obtained.

[0088] Formula 4: ;

[0089] Based on Formula 4, it can be seen that this is a high-order model, and it is difficult to solve the time-domain analytical expression of the grid connection point frequency deviation. To achieve model order reduction, the present invention performs variable substitution as shown in Formula 5.

[0090] Formula 5: ;

[0091] Optionally, after the above variable substitution, The expression of is converted into the expression shown in Formula 6.

[0092] Formula 6: ,in, Represents the power coefficient of the high-pressure cylinder after polymerization, represents the reheater time constant after polymerization, and R represents the governor droop coefficient after polymerization.

[0093] Optionally, combined with Formula 6, Formula 4 is reduced to an expression shown in the following Formula 7.

[0094] Formula 7: ,in, represents the natural oscillation frequency, represents the damping ratio, which is defined as shown in Formula 8 below.

[0095] Formula 8: ;

[0096] Step 1.2: Calculate and transform the grid frequency response model according to the change in active power of the wind farm during the grid fault period to obtain a discretized grid frequency response model during the grid fault period.

[0097] For example, in some optional embodiments, the step 1.2 includes: step 3.1, step 3.2 and step 3.3;

[0098] Step 3.1, determining a change in the active power of the wind farm during the grid fault based on the active power of the wind farm during the grid fault and the active power of the wind farm before the grid fault;

[0099] Step 3.2: Calculate the grid frequency response model of the wind farm in any control period based on the variation and the grid frequency response model;

[0100] Step 3.3: Perform the inverse Laplace transform on the grid frequency response model of the wind farm in any control period, and conduct derivation and calculation to obtain the discretized grid frequency response model during grid faults. The discretized grid frequency response model during grid faults represents the mathematical relationship between the deviation value of the grid frequency at the (n + 1)-th control node and the active power command of the wind farm at the n-th control node.

[0101] Optionally, calculate according to Formula 7. When the active power output of the wind farm decreases during grid faults, the expression of the grid frequency response model is as shown in Formula 9: as shown.

[0102] Where, represents the change in the active power output of the wind farm during grid faults, represents the active power output of the wind farm during the fault, and represents the active power output of the wind farm before the fault occurs.

[0103] When the output power of the wind farm changes once every control period ΔT, Formula 9 represents the expression of the grid frequency response model within the first control period (0 < t < ΔT). Within the second control period (ΔT < t < 2ΔT), the expression of the grid frequency response model is as shown in Formula 10 below.

[0104] Formula 10: ; [[ID=2,4]]

[0105] Where, represents the change in the active power output of the wind farm within the first control period, and represents the change in the active power output of the wind farm within the second control period, and e is the natural constant.

[0106] Similarly, within the n-th control period (nΔT - ΔT < t < nΔT), the expression of the grid frequency response model is as shown in Formula 11 below.

[0107] Formula 11: ;

[0108] Where, represents the change in the active power output of the wind farm within the i-th control period, that is, the difference between the active power output of the wind farm within the i-th control period and the active power output before the fault occurs.

[0109] Optionally, the present invention further performs the inverse Laplace transform, and the time-domain expression corresponding to Formula 11 is as shown in Formula 12 below.

[0110] Formula 12: ;

[0111] Where, , 、 、 and etc. are intermediate variables and have no actual meaning.

[0112] Optionally, according to Formula 12, the deviation value of the grid frequency at the n+1th control node, that is, at time nΔT, can be derived as shown in the following Formula 13.

[0113] Formula 13: ;

[0114] Based on the above formula, the mathematical relationship between the deviation value of the grid frequency at the n+1th control node and the wind farm active power command at the nth control node can be derived as shown in the following formula 14.

[0115] Formula 14: , where the values ​​of the two parameters are related to the wind farm active power instructions at the first n-1 control nodes, as shown in the following formula 15.

[0116] Formula 15: , in, The value of is greater than 0, so The value of The value of is positively correlated.

[0117] Optionally, the control period in the present invention refers to the time required for a control instruction to be updated once. A control node refers to the time when the control instruction is updated, and the interval between two control nodes is one control node.

[0118] S200: Constructing a coordinated support model for voltage and frequency of the wind farm to the grid connection point during a grid fault according to the grid frequency response model and the grid equivalent circuit during a grid fault;

[0119] Optionally, in some optional embodiments, the S200 includes: step 4.1, step 4.2 and step 4.3;

[0120] Step 4.1, determining a grid connection point voltage model of the wind farm during the grid fault period based on the grid equivalent circuit during the grid fault period;

[0121] Step 4.2: Determine an optimization target model based on the grid connection point voltage model, the grid frequency response model, and the optimization target, wherein the optimization target model represents: a mathematical relationship of the optimization target at the nth control node;

[0122] Step 4.3: Establish constraint conditions for the optimization target model to construct a collaborative support model for the voltage and frequency of the wind farm to the grid connection point during a grid fault, wherein the constraint conditions include: voltage constraint, current constraint and power constraint.

[0123] Optionally, the grid equivalent circuit of the present invention is as follows: Figure 2 As shown, according to Figure 2 According to the grid equivalent circuit, the present invention can obtain the expression of the wind farm grid connection point voltage during the grid fault as shown in the following formula 16.

[0124] Formula 16: ;

[0125] in, represents the equivalent voltage of the grid during the grid fault period, r and x represent the equivalent resistance and equivalent inductive reactance of the grid respectively, and They represent the active current and reactive current output by the wind farm respectively.

[0126] It should be noted that the wind farm collaborative support model during a grid fault has two optimization objectives: one is to restore the grid frequency to its rated value, and the other is to restore the voltage at the wind farm connection point to its rated value. Therefore, the mathematical expression for the optimization objective at the nth control node is shown in Equation 17.

[0127] Formula 17: ;

[0128] Wherein, the subscript n represents the grid state and optimization variables at the nth control node, Represents the difference between the voltage at the wind farm grid connection point and the rated value, represents the voltage rating of the wind farm grid connection point, and It represents the weight coefficient of the optimization target. When the frequency deviation of the grid connection point is small, the wind farm should mainly support the voltage recovery of the grid connection point; when the frequency deviation of the grid connection point is large, the wind farm should support the voltage recovery of the grid connection point and the grid frequency recovery at the same time. Therefore, The value should be the same as The values ​​of are directly proportional, for example, as shown in the following formula 18.

[0129] Formula 18: ,in, Represents the initial value of the weight coefficient.

[0130] Optionally, the present invention can further optimize the constraints in the model, where the constraints include voltage constraints, current constraints, and power constraints.

[0131] First, the expression of the voltage constraint is shown in the following formula 19.

[0132] Formula 19: ;

[0133] Among them, the first item is the power flow constraint, the second item is the transient stability constraint, and the third item is the feasibility constraint.

[0134] Secondly, the expression of the current constraint is shown in the following formula 20.

[0135] Formula 20: ;

[0136] Wherein, the superscript j represents the relevant parameters and variables of the j-th wind turbine in the wind farm, m represents the number of wind turbines in the wind farm, and Represent the active current and reactive current output by the fan respectively, and It represents the maximum safe current of the fan.

[0137] Finally, the expression of the power constraint is shown in Equation 21 below.

[0138] Formula 21: ;

[0139] in, Represents the active power output of the fan, and It represents the upper limit of the active output of the wind turbine.

[0140] In summary, the collaborative support model based on model predictive control during power grid faults can be described as shown in the following formula 22.

[0141] Formula 22: ;

[0142] Among them, st is the abbreviation of subject to, which means the constraints are as follows.

[0143] S300: Calculate and generate current instructions for each generator in the wind farm according to the collaborative support model, and control each generator in the wind farm to operate according to its own current instruction to collaboratively support the frequency and voltage of the grid connection point.

[0144] For example, in some optional embodiments, the S300 includes: step 5.1 and step 5.2;

[0145] Step 5.1, performing convex optimization on the collaborative support model to obtain a collaborative support model in a second-order cone form;

[0146] Step 5.2: Based on the second-order cone-shaped collaborative support model, calculate and generate current instructions for each generator in the wind farm, and control each generator in the wind farm to operate according to its own current instruction to collaboratively support the frequency and voltage of the grid connection point.

[0147] Optionally, in some optional embodiments, the step 5.2 includes: step 6.1, step 6.2 and step 6.3;

[0148] Step 6.1, controlling each generator of the wind farm to follow the collaborative support model based on the second-order cone form, using a solver to perform a calculation to obtain a target current of each generator of the wind farm;

[0149] Step 6.2: Generate a current command for each generator based on the target current of each generator;

[0150] Step 6.3: Control each generator of the wind farm to operate according to its own current instruction, so as to coordinately support the frequency and voltage of the grid connection point.

[0151] Optionally, Formula 22 is a typical non-convex optimization problem, and its solution efficiency is difficult to guarantee. In order to transform it into a convex optimization problem to improve the optimization efficiency, the present invention proposes to transform Formula 22 into a second-order cone programming problem.

[0152] First, the square root term in Formula 16 is converted to a square term. The converted expression is shown in Formula 23 below.

[0153] Formula 23: ;

[0154] Next, Formula 23 is scaled, and the scaled expression is shown in Formula 24 below.

[0155] Formula 24: ;

[0156] It should be noted that this scaling is effectively tightened under the optimization objective of Formula 17. At the same time, it can be found from Formula 19 and Formula 24 that the transient stability constraint and feasibility constraint are also included in Formula 24.

[0157] Next, the calculation model of the wind turbine active power in Formula 21 is converted into a second-order cone form to obtain the expression shown in Formula 25.

[0158] Formula 25: , where this scaling is also effectively tightened under the optimization objective of Formula 17.

[0159] In summary, the collaborative support model based on model predictive control during power grid faults is converted into the model shown in the following formula 26:

[0160] Formula 26: ;

[0161] Alternatively, during a grid fault, the wind farm control center can use a commercial solver to solve Equation 26, generating current commands for each wind farm generator and issuing them to each generator. Each generator in the wind farm quickly follows the command, thereby achieving coordinated support for grid frequency and voltage.

[0162] Optionally, in order to verify the effect of the collaborative support method proposed in the present invention, the inventor of this solution is based on the MATLAB / Simulink environment. Figure 3 The power grid model shown was verified by multiple cases. A three-phase symmetrical voltage drop fault occurred at node 3, and the fault duration was 1.5 seconds. The voltage fault detection delay was set to 50ms. The power reference value of the power grid is 1000MW, the voltage reference value is 690V, and the frequency reference value is 50Hz. In the simulation, an aggregated doubly fed wind farm model was used to improve the computational efficiency. Four different wind farm active support strategies were used for comparative analysis: Scheme 1 and Scheme 2 are both existing control strategies, with reactive current droop coefficients of 5.5 and 7 respectively, and Scheme 3 and Scheme 4 are both collaborative support methods proposed by the present invention. Among them, the weight coefficient in Scheme 3 is It is always 0, and the control period ΔT of scheme 4 is 500ms.

[0163] In case 1, the grid voltage dropped to about 0.2 PU (per unit). Figure 4 (Grid frequency waveform in Case 1) and Figure 5 (RMS voltage at the grid connection point in Case 1) shows the grid frequency waveform and RMS voltage at the grid connection point during the fault period. Figure 4 It can be seen from the figure that after the voltage fault occurs, the frequency deviation of the grid connection point corresponding to Scheme 3 and Scheme 4 is significantly lower than that of Scheme 1 and Scheme 2. The minimum frequency of Scheme 1 is 49.247 Hz, the minimum frequency of Scheme 2 is 49.340 Hz, the minimum frequency of Scheme 3 is 49.700 Hz, and the minimum frequency of Scheme 4 is 49.757 Hz.

[0164] In the first control cycle, the supporting effects of Scheme 3 and Scheme 4 on the grid frequency are similar. This is because the frequency deviation of the grid connection point is close to 0 in a short period of time after the fault occurs. Therefore, the weight coefficient of the frequency support part in the optimization objective of the collaborative support model of the present invention is also 0. Therefore, the wind farm only supports the effective value of the grid connection point voltage.

[0165] During the second and third control cycles, the weight coefficient of the frequency support part in the optimization objective of Scheme 4 increases with the increase of frequency deviation. At this time, the wind farm supports both the grid frequency and the effective value of the grid connection point voltage, and the grid frequency begins to gradually recover.

[0166] from Figure 5As can be seen from the figure, after the voltage fault occurs, the effective grid connection point voltage values ​​corresponding to Schemes 3 and 4 are significantly higher than those corresponding to Schemes 1 and 2. The grid connection point voltage recovers to 0.650 PU (per unit) under Scheme 1, 0.714 PU (per unit) under Scheme 2, and 0.777 PU (per unit) under both Schemes 3 and 4. Consistent with the analysis above, since the grid connection point frequency deviation is close to zero in the short period after the fault occurs, the weight coefficient of the frequency support component in the optimization objective of the frequency / voltage joint support model in the first control cycle is also 0. Therefore, Schemes 3 and 4 have similar support effects on the grid connection point voltage in the first control cycle.

[0167] During the second and third control cycles, the weight coefficient for the frequency support component of the optimization objective increased with increasing frequency deviation, so the wind farm's support for the grid connection point voltage under Scheme 4 was not always optimal. Despite this, the lowest grid connection point effective value under Scheme 4 reached 0.756 PU (per unit), close to the optimal value of 0.777 PU (per unit) and significantly higher than the grid connection point effective values ​​under Schemes 1 and 2.

[0168] Optionally, Option 4 significantly improves the wind farm's ability to support grid frequency during a fault while slightly sacrificing the wind farm's ability to support grid voltage.

[0169] Figure 6 (Reference and actual rotor current values ​​in Case 1) shows the reference and actual values ​​of the wind turbine rotor current corresponding to Scheme 4 during a fault. During the fault, the wind turbine can quickly follow the station instructions and provide joint support for the grid frequency and voltage.

[0170] Figure 7 The wind farm output waveforms (a), stator voltage (b), stator current (c), rotor current (d), and power corresponding to Scheme 1 in Case 1 are shown. Figure 8 The wind farm output waveforms corresponding to Option 2 in Case 1 are shown: (a) stator voltage (b) stator current (c) rotor current (d) power. Figure 9 The wind farm output waveforms corresponding to Scheme 3 in Case 1 are shown: (a) stator voltage (b) stator current (c) rotor current (d) power. Figure 10 The wind farm output waveform corresponding to Scheme 4 in Case 1 is shown: (a) stator voltage (b) stator current (c) rotor current (d) power. Figures 7 to 10 , it can be found that the transient stability of the wind farm is not weakened under different schemes.

[0171] Optionally, in Case 2, the grid connection point voltage drops to about 0.1 PU (per unit). At the same time, in order to increase the control group, the reactive current droop coefficients in Scheme 1 and Scheme 2 are adjusted to 2.5 and 3.3, respectively. Figure 11 The grid frequency waveform during the fault period is shown. Figure 12 The effective value of the grid connection point voltage is shown.

[0172] Alternatively, unlike the results in Case 1, the support capability of the grid frequency in Case 2 is significantly improved, and the lowest grid frequency is 49.787Hz. Figure 12 It can be seen that Scheme 1's support effect on the grid connection point voltage is the lowest among the four schemes, at only 0.493 PU (per unit). Meanwhile, Scheme 2's voltage support effect is similar to Scheme 1's, while its frequency support effect is the lowest among the four schemes, at only 49.460 Hz. This further demonstrates that traditional wind farm active support strategies based on a fixed reactive current droop coefficient are difficult to achieve joint support for grid frequency and voltage. Similar to the results in Case 1, Schemes 3 and 4 provide similar support for grid frequency in the first control cycle. In the second and third control cycles, the weighting coefficient for the frequency support component of Scheme 4's optimization objective increases with increasing frequency deviation. At this point, the wind farm supports both the grid frequency and the effective value of the grid connection point voltage, and the grid frequency begins to recover. Schemes 3 and 4 provide similar support for the grid connection point voltage in the first control cycle. However, in the second and third control cycles, because the weighting coefficient for the frequency support component of Scheme 4's optimization objective increases with increasing frequency deviation, the wind farm's support for the grid connection point voltage under Scheme 4 does not always reach optimal levels. Despite this, the supporting effect of Scheme 4 on the grid at the connection point only slightly decreases in the second control cycle. The supporting effect in other control cycles is very close to that of Scheme 30, and is far better than that of Schemes 1 and 2.

[0173] Figure 13 The reference value and actual value of the wind turbine rotor current corresponding to Scheme 4 during the fault period are shown. During the fault period, the wind turbine can quickly follow the station instructions and provide joint support for the grid frequency and voltage. Figure 14 Wind farm output waveforms corresponding to Scheme 1 in Case 2: (a) stator voltage (b) stator current (c) rotor current (d) power. Figure 15 Wind farm output waveforms corresponding to Scheme 2 in Case 2: (a) stator voltage (b) stator current (c) rotor current (d) power. Figure 16 Wind farm output waveforms corresponding to Option 3 in Case 2: (a) stator voltage (b) stator current (c) rotor current (d) power. Figure 17The wind farm output waveform corresponding to Scheme 4 in Case 2: (a) stator voltage (b) stator current (c) rotor current (d) power. Figures 14 to 17 , it can be found that the transient stability of the wind farm is not weakened under different schemes.

[0174] Alternatively, Case 1 and Case 2 effectively demonstrate the superiority of the present invention in actively supporting grid frequency and voltage recovery. This invention not only enables the wind farm to achieve near-optimal support for the effective value of the grid connection point voltage, but also significantly improves grid frequency stability during faults.

[0175] Although the operations are depicted in a particular order, this should not be understood as requiring that the operations be performed in the particular order shown or in a sequential order.Multitasking and parallel processing may be advantageous under certain circumstances.

[0176] It should be understood that the various steps described in the method embodiments of the present invention may be performed in different orders and / or in parallel. In addition, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present invention is not limited in this respect.

[0177] like Figure 18 As shown, the present invention provides a device for collaboratively supporting voltage and frequency of a wind farm to a grid connection point, comprising: a frequency response model building unit 100, a collaborative support model building unit 200 and a generator operation unit 300;

[0178] The frequency response model construction unit 100 is used to construct a discretized grid frequency response model during a grid fault period based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient and reheater time constant of the synchronous generator in the grid;

[0179] The collaborative support model construction unit 200 is used to construct a collaborative support model of the voltage and frequency of the wind farm to the grid connection point during the grid fault period based on the grid frequency response model and the grid equivalent circuit during the grid fault period;

[0180] The generator operation unit 300 is used to calculate and generate current instructions for each generator in the wind farm according to the collaborative support model, and control each generator in the wind farm to operate according to its own current instruction to collaboratively support the frequency and voltage of the grid connection point.

[0181] Optionally, in some optional implementations, the frequency response model construction unit 100 includes: a frequency response model construction subunit and a frequency response model discretization subunit;

[0182] The frequency response model construction subunit is used to construct a power grid frequency response model based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient and reheater time constant of the synchronous generator inside the power grid;

[0183] The frequency response model discrete subunit is used to calculate and transform the grid frequency response model according to the change in active power of the wind farm during the grid fault period to obtain a discretized grid frequency response model during the grid fault period.

[0184] Optionally, in certain optional embodiments, the frequency response model construction subunit includes: a grid connection point frequency deviation establishment subunit, a variable substitution subunit, and a time domain conversion subunit;

[0185] The grid connection point frequency deviation establishment subunit is used to establish a grid connection point frequency deviation model based on the active power-frequency transfer function of each synchronous generator in the power grid and the disturbance power in the power grid, wherein the active power-frequency transfer function includes: inertia time constant, damping time constant, mechanical power proportional coefficient, speed governor droop coefficient, high-pressure cylinder power coefficient and reheater time constant, and the grid connection point frequency deviation model is a high-order complex domain expression;

[0186] The variable substitution subunit is used to perform variable substitution on the governor droop coefficient, high-pressure cylinder power coefficient and reheater time constant in the grid connection point frequency deviation model;

[0187] The time domain conversion subunit is used to perform time domain conversion on the grid connection point frequency deviation model after variable substitution to obtain the grid frequency response model, wherein the grid frequency response model is a low-order time domain expression.

[0188] Optionally, in certain optional embodiments, the frequency response model discrete subunit includes: a variation determination subunit, a control period model calculation subunit, and a model derivation calculation subunit;

[0189] The change amount determining subunit is configured to determine the change amount of the active power of the wind farm during the grid fault period based on the active power of the wind farm during the grid fault period and the active power of the wind farm before the grid fault period;

[0190] The control period model calculation subunit is configured to calculate a grid frequency response model of the wind farm in any control period based on the variation and the grid frequency response model;

[0191] The model derivation and calculation subunit is used to perform an inverse Laplace transform on the grid frequency response model of the wind farm in any control period, and perform derivation and calculation to obtain a discretized grid frequency response model during a grid fault period, wherein the discretized grid frequency response model during a grid fault period represents a mathematical relationship between a deviation value of the grid frequency at the n+1th control node and an active power command of the wind farm at the nth control node.

[0192] Optionally, in certain optional embodiments, the collaborative support model construction unit 200 includes: a grid connection point voltage determination subunit, an optimization target determination subunit, and a collaborative support model construction subunit;

[0193] The grid connection point voltage determination subunit is configured to determine a grid connection point voltage model of the wind farm during a grid fault period based on a grid equivalent circuit during a grid fault period;

[0194] The optimization target determination subunit is used to determine an optimization target model according to the grid connection point voltage model, the grid frequency response model and the optimization target, wherein the optimization target model represents: a mathematical relationship of the optimization target at the nth control node;

[0195] The collaborative support model construction subunit is used to establish constraint conditions for the optimization target model, thereby constructing a collaborative support model for the voltage and frequency of the wind farm to the grid connection point during a power grid fault, wherein the constraint conditions include: voltage constraint, current constraint and power constraint.

[0196] Optionally, in certain optional embodiments, the generator operation unit 300 includes: a convex optimization subunit and a generator operation subunit;

[0197] The convex optimization subunit is used to perform convex optimization on the collaborative support model to obtain a collaborative support model in a second-order cone form;

[0198] The generator operation subunit is used to calculate and generate current instructions for each generator in the wind farm based on the collaborative support model in the second-order cone form, and control each generator in the wind farm to operate according to its own current instruction to collaboratively support the frequency and voltage of the grid connection point.

[0199] Optionally, in certain optional embodiments, the generator operation subunit includes: a target current solving subunit, a current instruction generating subunit and a generator operation control subunit;

[0200] The target current solving subunit is used to control each generator of the wind farm to follow each collaborative support model based on the second-order cone form, and use a solver to perform solution calculation to obtain the target current of each generator of the wind farm;

[0201] The current instruction generating subunit is used to generate a current instruction for each generator based on the target current of each generator;

[0202] The generator operation control subunit is used to control each generator of the wind farm to operate according to its own current instruction, so as to coordinately support the frequency and voltage of the grid connection point.

[0203] Regarding the apparatus in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment of the method, and will not be elaborated here.

[0204] The wind farm's collaborative support device for grid connection point voltage and frequency includes a processor and a memory. The frequency response model construction unit 100, the collaborative support model construction unit 200, and the generator operation unit 300 are all stored in the memory as program units, and the processor executes the program units stored in the memory to implement corresponding functions.

[0205] The processor contains a core, which retrieves the corresponding program unit from memory. One or more cores can be configured. By adjusting core parameters based on generator parameters, they proactively support grid frequency and voltage recovery, preventing abnormal grid frequency and voltage caused by faults and improving grid stability during faults.

[0206] An embodiment of the present invention provides a computer-readable storage medium having a program stored thereon. When the program is executed by a processor, the method for collaboratively supporting the voltage and frequency of the grid connection point by the wind farm is implemented.

[0207] An embodiment of the present invention provides a processor, which is used to run a program, wherein when the program is run, the method for collaboratively supporting the voltage and frequency of the grid connection point by the wind farm is executed.

[0208] like Figure 19 As shown, an embodiment of the present invention provides an electronic device 70, comprising at least one processor 701, at least one memory 702 connected to the processor 701, and a bus 703. The processor 701 and the memory 702 communicate with each other via the bus 703. The processor 701 is configured to invoke program instructions stored in the memory 702 to execute the aforementioned method for collaboratively supporting voltage and frequency at a grid connection point by a wind farm. The electronic device herein may be a server, a PC, a PAD, a mobile phone, or the like.

[0209] The present invention also provides a computer program product, which, when executed on an electronic device, is adapted to execute a program for initializing the following method steps:

[0210] A method for collaboratively supporting voltage and frequency at a grid connection point by a wind farm, comprising:

[0211] A discretized grid frequency response model during a grid fault is constructed based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant of the synchronous generator within the grid.

[0212] Constructing a coordinated support model for the voltage and frequency of the wind farm to the grid connection point during the grid fault period based on the grid frequency response model and the grid equivalent circuit during the grid fault period;

[0213] According to the collaborative support model, current instructions for each generator in the wind farm are calculated and generated, and each generator in the wind farm is controlled to operate according to its own current instruction, so as to collaboratively support the frequency and voltage of the grid connection point.

[0214] Optionally, in certain optional embodiments, constructing a discretized grid frequency response model during a grid fault period based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant of the synchronous generator within the grid includes:

[0215] A grid frequency response model is constructed based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant of the synchronous generator within the grid.

[0216] The grid frequency response model is calculated and transformed according to the change in active power of the wind farm during the grid fault period to obtain a discretized grid frequency response model during the grid fault period.

[0217] Optionally, in certain optional embodiments, constructing a grid frequency response model based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant of the synchronous generator within the grid includes:

[0218] Establishing a grid connection point frequency deviation model based on the active power-frequency transfer function of each synchronous generator within the grid and the disturbance power within the grid, wherein the active power-frequency transfer function includes: inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant; and the grid connection point frequency deviation model is a high-order complex domain expression;

[0219] Performing variable substitution on the governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant in the grid-connected point frequency deviation model;

[0220] The grid connection point frequency deviation model after variable substitution is subjected to time domain conversion to obtain the grid frequency response model, wherein the grid frequency response model is a low-order time domain expression.

[0221] Optionally, in certain optional embodiments, the calculating and transforming the grid frequency response model according to the change in active power of the wind farm during the grid fault to obtain a discretized grid frequency response model during the grid fault includes:

[0222] determining a change in the active power of the wind farm during the grid fault according to the active power of the wind farm during the grid fault and the active power of the wind farm before the grid fault;

[0223] Calculating a grid frequency response model of the wind farm in any control period according to the variation and the grid frequency response model;

[0224] The grid frequency response model of the wind farm in any control period is subjected to an inverse Laplace transform and deduced to obtain a discretized grid frequency response model during a grid fault. The discretized grid frequency response model during a grid fault represents the mathematical relationship between the deviation value of the grid frequency at the n+1th control node and the active power command of the wind farm at the nth control node.

[0225] Optionally, in certain optional embodiments, constructing a collaborative support model for voltage and frequency of the wind farm to the grid connection point during a grid fault based on the grid frequency response model and the grid equivalent circuit during a grid fault includes:

[0226] Determine the grid connection point voltage model of the wind farm during the grid fault period according to the grid equivalent circuit during the grid fault period;

[0227] Determining an optimization target model according to the grid connection point voltage model, the grid frequency response model, and the optimization target, wherein the optimization target model represents: a mathematical relationship of the optimization target at the nth control node;

[0228] Constraints are established for the optimization target model to construct a collaborative support model for the voltage and frequency of the wind farm to the grid connection point during a power grid fault, wherein the constraints include: voltage constraints, current constraints and power constraints.

[0229] Optionally, in certain optional embodiments, calculating and generating current instructions for each generator in the wind farm according to the collaborative support model, and controlling each generator in the wind farm to operate according to the respective current instructions to collaboratively support the frequency and voltage at the grid connection point includes:

[0230] Performing convex optimization on the collaborative support model to obtain a collaborative support model in a second-order cone form;

[0231] Based on the second-order cone-shaped collaborative support model, current instructions for each generator in the wind farm are calculated and generated, and each generator in the wind farm is controlled to operate according to its own current instruction to collaboratively support the frequency and voltage of the grid connection point.

[0232] Optionally, in certain optional embodiments, the collaborative support model based on the second-order cone form calculates and generates current instructions for each generator in the wind farm, and controls each generator in the wind farm to operate according to the respective current instructions to collaboratively support the frequency and voltage at the grid connection point, including:

[0233] Controlling each generator of the wind farm to follow the collaborative support model based on the second-order cone form, using a solver to perform a calculation to obtain a target current of each generator of the wind farm;

[0234] generating a current command for each generator based on the target current of each generator;

[0235] The generators in the wind farm are controlled to operate according to their respective current instructions to coordinate the frequency and voltage of the grid connection point.

[0236] The present invention is described with reference to flowcharts and / or block diagrams of methods, apparatuses, electronic devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable device to produce a machine, so that the instructions executed by the processor of the computer or other programmable device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0237] In a typical configuration, an electronic device includes one or more processors (CPUs), a memory, and a bus. The electronic device may also include an input / output interface, a network interface, and the like.

[0238] Memory may include non-permanent memory in a computer-readable medium, random access memory (RAM), and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory includes at least one memory chip. Memory is an example of a computer-readable medium.

[0239] Computer-readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory media such as modulated data signals and carrier waves.

[0240] In the description of the present invention, it should be understood that if the terms "up", "down", "front", "back", "left" and "right" are used to indicate directions or positional relationships, they are based on the directions or positional relationships shown in the accompanying drawings. They are only used to facilitate the description of the present invention and simplify the description, and do not indicate or imply that the positions or elements referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, they should not be understood as limitations of the present invention.

[0241] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. It should also be noted that the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, commodity, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, commodity, or device comprising the element.

[0242] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROMs, optical storage, etc.) containing computer-usable program code.

[0243] The above are merely embodiments of the present invention and are not intended to limit the present invention. It will be apparent to those skilled in the art that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are intended to be included within the scope of the claims of the present invention.

Claims

1. A method for collaboratively supporting voltage and frequency at a wind farm connection point, characterized in that: include: A discretized grid frequency response model during a grid fault is constructed based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant of the synchronous generator within the grid. Constructing a coordinated support model for the voltage and frequency of the wind farm to the grid connection point during the grid fault period based on the grid frequency response model and the grid equivalent circuit during the grid fault period; According to the collaborative support model, current instructions for each generator in the wind farm are calculated and generated, and each generator in the wind farm is controlled to operate according to its own current instruction to collaboratively support the frequency and voltage of the grid connection point; The discretized grid frequency response model during the grid fault period represents the mathematical relationship between the deviation value of the grid frequency at the n+1th control node and the active power instruction of the wind farm at the nth control node: ； in, ； ΔT represents the control period, represents the change in active output of the wind farm at the nth control node during the grid fault period, R represents the aggregated governor droop coefficient, represents the damping time constant, e is the natural constant, 、 、 and represents the intermediate constant, represents the active power output of the wind farm during the fault period, Represents the change in active power output of the wind farm during the i-th control cycle, represents the change in active power output of the wind farm at the n-1th control node during the grid fault period, and n represents the grid state and optimization variables at the nth control node; , y represents the yth synchronous generator in the power grid, and m represents the number of synchronous generators in the power grid; The collaborative support model is as follows As shown, it is subject to voltage, current and power constraints, where the voltage constraint is expressed as: ； The current constraint is expressed as: ； The power constraint is expressed as: ； Where n represents the grid state and optimization variables at the nth control node, Represents the voltage at the wind farm grid connection point, Represents the voltage rating of the wind farm grid connection point, represents the weight coefficient of the optimization target, j represents the relevant parameters and variables of the j-th wind turbine in the wind farm, and Respectively represent the active current and reactive current output by the fan, It represents the maximum safe current of the fan. represents the equivalent voltage of the grid during the grid fault period, r and x represent the equivalent resistance and equivalent inductive reactance of the grid respectively, and Represent the active current and reactive current output by the wind farm respectively, It represents the active power output of the wind farm before the fault occurs. Represents the active output of the fan, It represents the upper limit of the active output of the wind turbine.

2. The method for collaboratively supporting the voltage and frequency of the grid connection point by a wind farm according to claim 1, characterized in that: The method constructs a discretized grid frequency response model during a grid fault period based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant of the synchronous generator inside the grid, including: A grid frequency response model is constructed based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant of the synchronous generator within the grid. The grid frequency response model is calculated and transformed according to the change in active power of the wind farm during the grid fault period to obtain a discretized grid frequency response model during the grid fault period.

3. The method for collaboratively supporting the voltage and frequency of the grid connection point by a wind farm according to claim 2, characterized in that: The grid frequency response model is constructed based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient and reheater time constant of the synchronous generator inside the grid, including: Establishing a grid connection point frequency deviation model based on the active power-frequency transfer function of each synchronous generator within the grid and the disturbance power within the grid, wherein the active power-frequency transfer function includes: inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant; and the grid connection point frequency deviation model is a high-order complex domain expression; Performing variable substitution on the governor droop coefficient, high-pressure cylinder power coefficient, and reheater time constant in the grid-connected point frequency deviation model; The grid connection point frequency deviation model after variable substitution is subjected to time domain conversion to obtain the grid frequency response model, wherein the grid frequency response model is a low-order time domain expression.

4. The method for collaboratively supporting the voltage and frequency of the grid connection point by a wind farm according to claim 2, characterized in that: The calculating and transforming the grid frequency response model according to the change in the active power of the wind farm during the grid fault to obtain a discretized grid frequency response model during the grid fault includes: determining a change in the active power of the wind farm during the grid fault according to the active power of the wind farm during the grid fault and the active power of the wind farm before the grid fault; Calculating a grid frequency response model of the wind farm in any control period according to the variation and the grid frequency response model; The grid frequency response model of the wind farm in any control period is subjected to an inverse Laplace transform and deduced to obtain a discretized grid frequency response model during a grid fault. The discretized grid frequency response model during a grid fault represents the mathematical relationship between the deviation value of the grid frequency at the n+1th control node and the active power command of the wind farm at the nth control node.

5. The method for collaboratively supporting the voltage and frequency of the grid connection point by a wind farm according to claim 1, characterized in that: The step of constructing a coordinated support model for the voltage and frequency of the wind farm to the grid connection point during a grid fault according to the grid frequency response model and the grid equivalent circuit during a grid fault comprises: Determine the grid connection point voltage model of the wind farm during the grid fault period according to the grid equivalent circuit during the grid fault period; Determining an optimization target model according to the grid connection point voltage model, the grid frequency response model, and the optimization target, wherein the optimization target model represents: a mathematical relationship of the optimization target at the nth control node; Constraints are established for the optimization target model to construct a collaborative support model for the voltage and frequency of the wind farm to the grid connection point during a power grid fault, wherein the constraints include: voltage constraints, current constraints and power constraints.

6. The method for collaboratively supporting the voltage and frequency of the grid connection point by a wind farm according to claim 1, characterized in that: The step of calculating and generating current instructions for each generator of the wind farm according to the collaborative support model, and controlling each generator of the wind farm to operate according to the respective current instructions to collaboratively support the frequency and voltage of the grid connection point includes: Performing convex optimization on the collaborative support model to obtain a collaborative support model in a second-order cone form; Based on the second-order cone-shaped collaborative support model, current instructions for each generator in the wind farm are calculated and generated, and each generator in the wind farm is controlled to operate according to its own current instruction to collaboratively support the frequency and voltage of the grid connection point.

7. The method for collaboratively supporting the voltage and frequency of the grid connection point by a wind farm according to claim 6, characterized in that: The collaborative support model based on the second-order cone form calculates and generates current instructions for each generator in the wind farm, and controls each generator in the wind farm to operate according to the respective current instructions to collaboratively support the frequency and voltage of the grid connection point, including: Controlling each generator of the wind farm to follow the collaborative support model based on the second-order cone form, using a solver to perform a calculation to obtain a target current of each generator of the wind farm; generating a current command for each generator based on the target current of each generator; The generators in the wind farm are controlled to operate according to their respective current instructions to coordinate the frequency and voltage of the grid connection point.

8. A device for collaboratively supporting voltage and frequency at a wind farm's grid connection point, characterized in that: A method for collaboratively supporting the voltage and frequency of a grid connection point by a wind farm according to any one of claims 1 to 7, the device comprising: a frequency response model construction unit, a collaborative support model construction unit, and a generator operation unit; The frequency response model construction unit is used to construct a discretized grid frequency response model during a grid fault period based on the inertia time constant, damping time constant, mechanical power proportional coefficient, governor droop coefficient, high-pressure cylinder power coefficient and reheater time constant of the synchronous generator inside the grid; The collaborative support model construction unit is configured to construct a collaborative support model for the voltage and frequency of the wind farm to the grid connection point during a grid fault according to the grid frequency response model and the grid equivalent circuit during a grid fault; The generator operation unit is used to calculate and generate current instructions for each generator in the wind farm according to the collaborative support model, and control each generator in the wind farm to operate according to its own current instruction to collaboratively support the frequency and voltage of the grid connection point.

9. A computer-readable storage medium having a program stored thereon, characterized in that: When the program is executed by a processor, the method for collaboratively supporting the voltage and frequency of a grid connection point by a wind farm according to any one of claims 1 to 7 is implemented.

10. An electronic device, characterized in that: The electronic device includes at least one processor, and at least one memory and bus connected to the processor; wherein the processor and the memory communicate with each other via the bus; the processor is used to call program instructions in the memory to execute the method for collaborative support of grid connection point voltage and frequency by a wind farm as described in any one of claims 1 to 7.

Images