Wind-storage-load cooperative control method and device considering containment control of deep and far sea wind power plant

Abstract

The invention relates to the field of power system frequency control, in particular to a wind-storage-load cooperative control method and device considering deep and far sea wind power plant containment control, and the method comprises the steps: obtaining the data of a power system and the parameters of a wind turbine generator and a containment controller; establishing a wind power plant single-machine equivalent model considering wind power plant containment control; constructing a wind-storage-load coordinated power system frequency control optimization problem which takes energy storage output power and demand response power after disturbance and frequency modulation stage duration of a containment signal as control variables under a serious fault; and solving a frequency control optimization problem based on a sensitivity method to obtain an optimal control strategy of wind power and energy storage. Compared with the prior art, the single-machine equivalent model considering wind power plant containment control has good applicability during frequency calculation, collaborative optimization is carried out on offshore wind power plant containment signals, energy storage and demand response, and good economical efficiency is achieved while the system frequency safety requirement can be met.

Description

Technical Field

[0001] The present invention belongs to the field of frequency control of new power systems, and particularly relates to a wind-storage-load coordinated frequency control method and device for a power system considering the restraining control of a deep-sea wind farm. Background Art

[0002] In recent years, new energy represented by wind power and photovoltaic power has developed rapidly. The substitution effect of new energy has continuously reduced the system inertia and the frequency regulation ability is insufficient, posing challenges to the system frequency safety. Therefore, various countries have stipulated that grid-connected new energy should have a certain active support ability for frequency and voltage. According to the "Technical Regulations for Wind Farms Connected to the Grid" in China, grid-connected wind power and photovoltaic power should have primary frequency regulation ability to ensure the safety of the frequency system.

[0003] Domestic and foreign experts have conducted a large number of studies on wind power frequency regulation control and proposed methods such as synthetic inertia (SI) control, pitch angle control, overspeed control, and distributed consistency control. SI control increases the power of wind turbines by releasing rotor kinetic energy to provide a certain frequency support. The additional power is equal to the sum of the droop control and inertia control components. In order to suppress the possible "secondary frequency drop" (SFD) phenomenon, methods such as fuzzy control or trajectory optimization are often used to improve the performance of SI control. Both pitch angle control and overspeed control are load reduction controls, which can provide reliable reserves, but they have poor economy and serious mechanical wear. Therefore, control methods based on rotor kinetic energy are more widely used. For large-scale wind farms, the wind speed distribution characteristics cannot be ignored. The frequency regulation potential of wind turbines varies greatly, and the frequency regulation dynamics of wind farms will have strong uncertainty, bringing difficulties to wind power frequency regulation control.

[0004] For example, the solutions disclosed in Chinese patent applications CN202311354168.8, CN202411607909.3, etc., the current research on wind power frequency regulation control has the following main deficiencies:

[0005] 1) The research on frequency calculation methods considering wind speed distribution characteristics is insufficient. Large-scale wind farms have the characteristics of a large number of wind turbines, high model orders, and complex calculations. Direct simulation will face the problem of "curse of dimensionality", and it is difficult to obtain detailed wind speed data in the field when obtaining a multi-machine equivalent model.

[0006] 2) The method for suppressing the SFD risk that may be caused by wind power frequency regulation still needs to be studied. The rotor kinetic energy of wind turbines is limited. How to release the rotor kinetic energy orderly according to the system frequency regulation needs and the available kinetic energy of the units to ensure system frequency safety is a problem to be studied.

[0007] 3) Little consideration is given to the coordination of wind power frequency regulation with other control measures. Existing studies mostly focus on wind power frequency regulation alone. However, when faults are severe, relying solely on wind power frequency regulation cannot guarantee frequency security. At this time, wind power frequency regulation also needs to cooperate with other measures such as DC power support, energy storage, and demand response. Each control measure has different adjustable capacities, control costs, and response speeds. How to perform coordinated control is an issue that needs to be studied in wind power frequency regulation. Summary of the Invention

[0008] The object of the present invention is to overcome the problems existing in the prior art, such as the difficulty in calculating the frequency of the wind power system, the SFD risk in wind power frequency regulation, and the lack of coordinated consideration of multiple frequency control measures. A coordinated frequency control method for the wind-power-storage-load in the power system considering the restraint control of deep-sea wind farms is provided.

[0009] The object of the present invention can be achieved through the following technical solutions:

[0010] As the first aspect of the present invention, a coordinated control method for wind-power-storage-load considering the restraint control of deep-sea wind farms is provided. The method steps include:

[0011] Obtain power system data and the parameters of wind turbines and restraint controllers;

[0012] Establish an equivalent single-machine model of the wind farm considering the restraint control of the wind farm;

[0013] Construct an optimization problem for the coordinated frequency control of the power system of wind-power-storage-load with the minimum economic cost of frequency control as the objective under severe faults. The frequency control optimization problem uses the output power of the energy storage, the demand response power, and the duration of the frequency modulation stage of the restraint signal as control variables;

[0014] Solve the power system frequency control optimization problem based on the sensitivity method to obtain the optimal control strategies for wind power and energy storage.

[0015] As a preferred technical solution, the power system data includes:

[0016] Synchronous generator G s with capacity S g,s , inertia time constant H g,s and damping coefficient D s ; for steam turbines, the governor parameters include governor gain K st , reheater coefficient F H , reheater time constant T R and governor time constant T g ; for hydro turbines, the governor parameters include gain K ht , water hammer effect time constant T wand turbine governor time constants T2, T3 and T4;

[0017] Energy storage system control parameters, including maximum adjustable power Cost factor c1 and response time t ES ;

[0018] Demand response control parameters, including maximum adjustable power Cost factor c2 and response time t dr .

[0019] As a preferred technical solution, the wind turbine and control controller parameters include:

[0020] Impedance Z between lines lk in a wind farm lk And wind turbine G wi Capacity S wi , inertia time constant H wi and the transformer capacity S Ti And short-circuit impedance Z Ti ;

[0021] Obtain the wind farm control topology and control controller parameters, including the proportional coefficient and integral coefficient k p , k i .

[0022] As a preferred technical solution, the wind farm single-machine equivalent model taking into account the wind farm control is established as follows:

[0023] The capacity of an equivalent wind turbine is equal to the sum of the capacities of all wind turbines in the wind farm;

[0024] In the steady state before the disturbance, the mechanical power P captured by the equivalent wind turbine is m,eq Equal to the wind farm grid output power P PCC,0 The loss in the wind farm is P loss According to the maximum power tracking curve of the wind turbine, the corresponding equivalent wind turbine speed ω is calculated. r,eq , and according to the equivalent wind turbine speed ω r,eq and maximum tip speed ratio λ opt Find the equivalent wind turbine G weq Wind speed ν eq ; The connection impedance between the equivalent wind turbine and the common connection point is set as:

[0025]

[0026] Where n lk is the number of wind turbines upstream of line lk, Z lk is the impedance between the lines lk in the wind farm, n wis the total number of wind turbines in the wind farm;

[0027] During the frequency modulation process, the kinetic energy released by the equivalent wind turbine is equal to the additional power ΔP generated by each wind turbine in the wind farm during the frequency modulation process k,i The sum is:

[0028]

[0029] The additional power ΔP generated by the wind turbine i during the frequency modulation process k,i is expressed as follows:

[0030]

[0031] In the formula, x ref is the wind farm restraint signal; x i is the wind turbine consistency state variable; a ij is the communication weight; g i indicates whether the wind turbine receives the restraint signal; k p and k i are the restraint controller parameters, representing the restraint control proportional coefficient and integral coefficient respectively; V = {1, 2, …, n w} represents the set of wind turbine numbers, and n w is the total number of wind turbines in the wind farm;

[0032] After the frequency modulation reaches a steady state, the mechanical power P captured by the equivalent wind turbine m,eq is approximately the sum of the mechanical powers P m,i of all wind turbines.

[0033] As a preferred technical solution, the expression of the restraint signal x ref (t) is:

[0034]

[0035] In the formula, t1 is the fault start time, t2 is the demarcation point between the frequency modulation stage and the recovery stage, and t2 - t1 is denoted as T c , t3 is the frequency modulation control exit time; the parameter b is a positive number used to control the speed recovery speed, and the smaller b is, the slower the speed recovery; θ is a decimal used to ensure the continuity of x ref (t) at the moment t2.

[0036] As a preferred technical solution, the construction of the wind - storage - load coordinated power system frequency control optimization problem uses the frequency security index η to comprehensively evaluate the frequency security of the system, specifically including:

[0037] The initial frequency change rate R cof , which takes the frequency change rate within the set time after the disturbance and is used to reflect the frequency change speed in the initial time period after the disturbance occurs;

[0038] The lowest frequencies f of the two frequency dips nad1 , f nad2 ;

[0039] The frequency peak f during the two dips p1 ,

[0040] The amplitude m1 of the first frequency oscillation in the dynamic process;

[0041] The steady-state frequency f after the fault ss .

[0042] As an optimal technical solution, for the optimization problem of frequency control of the wind-storage-load coordinated power system, with the minimum economic cost of frequency control as the goal, and the output power P of the energy storage after the disturbance ES , the demand response power P dr , and the tie signal x ref (t) The duration T of the frequency modulation stage c are the control variables Z = (P ES , P dr , T c ) T , described as:

[0043]

[0044] In the formula, F is the economic cost of frequency control; c1 and c2 are the cost factors of energy storage and demand response respectively; g(·) represents the non-linear dynamic mapping relationship between the control measure and the system frequency; is the initial frequency change rate R cof maximum value; ε is a set decimal; f min is the lowest frequency value; f ss,min is the lowest frequency allowed by the system at steady state; f ss,min is the minimum value of the steady-state frequency after the fault; T c are the upper and lower bounds of the tie signal parameter T c adjustment respectively; are the upper bounds of the output power of the energy storage and the demand response power after the disturbance respectively.

[0045] As an optimal technical solution, the optimization problem of frequency control of the wind-storage-load coordinated power system is solved iteratively by the sensitivity-based approximate linearization method, and the steps are as follows:

[0046] Randomly initialize the control variable Z;

[0047] Calculate the corresponding system frequency response curve f(t) through numerical simulation and calculate each frequency safety index;

[0048] The sensitivity of the frequency security index η to the control variable Z is obtained by the perturbation method, and the safety index constraint inequalities are all converted into linear inequalities, and the frequency control optimization problem is transformed into a linear programming problem;

[0049] Solve the obtained linear programming problem, obtain the change amount of the control variable, and correct the control variable Z to be optimized;

[0050] Repeat the optimization until the change amount of the control variable is less than the set threshold.

[0051] As a second aspect of the present invention, there is provided an electronic device, including:

[0052] One or more processors;

[0053] A memory for storing one or more programs;

[0054] When the one or more programs are executed by the one or more processors, the one or more processors implement the wind-storage-load coordinated control method considering the far-reaching offshore wind farm restraint control as described above.

[0055] As a third aspect of the present invention, there is provided a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the steps of the wind-storage-load coordinated control method considering the far-reaching offshore wind farm restraint control as described above are implemented.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] 1) For the wind farm considering the restraint consistency control, the present invention constructs a single-machine equivalent model of the wind farm that can be used for rapid frequency calculation, establishes a mathematical model of the wind-storage-load coordinated frequency control problem, and applies the sensitivity method to solve the optimal control measures such as the wind power restraint signal, energy storage, and demand response, which is of great significance for improving the frequency security of the new power system.

[0058] 2) The single-machine equivalent model of the wind farm considering the far-reaching offshore wind farm restraint control established by the method of the present invention has less calculation time, avoids the "curse of dimensionality", and due to the consistency of the dynamic behavior of the units in the field, the single-machine equivalent model has good accuracy and can meet the requirements of system frequency calculation under large disturbance conditions, and has good adaptability.

[0059] 3) The present invention establishes a wind-storage-load coordinated frequency control strategy, synergistically optimizes the wind farm restraint signal, energy storage, and demand response, and can reduce costs while meeting the system frequency security requirements, and has good economy. Description of the Drawings

[0060] Figure 1The flowchart of steps for a wind - storage - load coordinated frequency control method of a power system considering the restraint control of a far - reaching offshore wind farm provided by an embodiment of the present invention;

[0061] Figure 2 The schematic diagram of a 3 - machine 9 - node system with an offshore wind farm connected provided by an embodiment of the present invention;

[0062] Figure 3 The comparison diagram of wind power and system frequency response curves when disturbances occur in the single - machine equivalent model and detailed model of an offshore wind farm provided by an embodiment of the present invention, where (a) is the wind power curve and (b) is the frequency response curve; the solid line is the detailed model and the dashed line is the single - machine equivalent model;

[0063] Figure 4 The flowchart of the sensitivity - based approximate linearization solution method provided by an embodiment of the present invention;

[0064] Figure 5 The frequency response curves of the single - machine equivalent model under different restraint signals provided by an embodiment of the present invention. Specific implementation manners

[0065] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and gives detailed implementation manners and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0066] Embodiment 1

[0067] In order to overcome the problems existing in the existing research, such as the difficulty in calculating the frequency of the wind power system, the SFD risk in wind power frequency modulation, and the lack of coordinated consideration of various frequency control measures, the present invention proposes a wind - storage - load coordinated frequency control method for a power system considering the restraint control of a far - reaching offshore wind farm. For the wind farm considering the restraint consistency control, this method constructs a single - machine equivalent model of the wind farm that can be used for rapid frequency calculation, establishes a mathematical model of the wind - storage - load coordinated frequency control problem, and applies the sensitivity method to solve the optimal control measures such as wind power restraint signals, energy storage, and demand response. As Figure 1 shown, the wind - storage - load coordinated frequency control method of the power system of the present invention includes the following steps:

[0068] Step 1: Obtain the power system data and the parameters of the wind farm, wind turbines, and restraint controllers;

[0069] Step 2: Establish a single - machine equivalent model of the wind farm considering the restraint control of the wind farm;

[0070] Step 3: Construct an optimization problem for the frequency control of the wind - storage - load coordinated power system;

[0071] Step 4: Solve the optimal power system frequency control problem based on the sensitivity method to obtain the optimal control strategies for wind power and energy storage.

[0072] Specifically, in step (1), obtain the power system data and the parameters of the wind turbines and the tie controllers. The implementation process is as follows:

[0073] Obtain the power system data, including the capacity S s of the synchronous generator G g,s , the inertia time constant H g,s and the damping coefficient D s , s = 1, 2, …, n g , where n g is the number of synchronous generators; for steam turbines, the governor parameters include the governor gain K st , the reheater coefficient F H , the reheater time constant T R and the governor time constant T g ; for hydro turbines, the governor parameters include the gain K ht , the water hammer effect time constant T w and the hydro turbine governor time constants T2, T3 and T4; obtain the energy storage system control parameters, including the maximum adjustable power , the cost factor c1 and the response time t ES ; obtain the demand response control parameters, including the maximum adjustable power , the cost factor c2 and the response time t dr .

[0074] Obtain the wind farm and wind turbine parameters, including the impedance Z lk between lines l-k in the wind farm, l = 1, 2, …, m, k = 1, 2, …, m, where l and k are the node numbers in the wind farm and m is the total number of nodes in the wind farm; and the capacity S wi of the wind turbine G wi , the inertia time constant H wi and the capacity S Ti of the generator terminal transformer and the short-circuit impedance Z Ti , i = 1, 2, …, n w , where n w is the total number of wind turbines in the wind farm; define the wind turbine G wi consistency state variable x i :

[0075]

[0076] In the formula: ω i is the rotational speed of the wind turbine G wi , ω i0 is for G wiThe initial speed, ω min is the minimum speed allowed for the wind turbine, x i Reflects the wind turbine G wi The ratio of the residual rotor kinetic energy to the available rotor kinetic energy.

[0077] Obtain the wind farm control topology structure. If the wind turbine G wj To G wi If the state variable is passed, the communication weight a ij =1, otherwise, a ij =0; when the wind turbine receives the restraining signal, g i =1, otherwise, g i =0; Get the control controller parameters, including the proportional coefficient and the integral coefficient k p , k i ; Assume the wind farm restraining signal is x ref (t), then according to the control algorithm, the wind turbine G wi The power ΔP generated during the frequency modulation process k,i :

[0078]

[0079] Where: V = {1,2,…,n w} represents the wind turbine group number set, n w is the total number of wind turbines in the wind farm.

[0080] In step (2), a single-machine equivalent model of a wind farm taking into account the wind farm control is established, and the implementation process is as follows:

[0081] When the single machine is equal, the equivalent wind turbine G weq The capacity is S eq , and the wind turbines in the wind farm have the same capacity, both are S w , then S eq =n w S w ; Assume that the output power of the wind farm grid connection point before the disturbance is P PCC,0 , the field loss is P loss , then the total mechanical energy captured by the wind turbines in the field is P mt,0 =P PCC,0 +P loss According to the principle of power conservation, the equivalent wind turbine G in steady state weq Captured mechanical power P m,eq With P mt,0 Equal; According to the maximum power tracking curve of the wind turbine, the corresponding equivalent machine speed can be calculated where k opt is the optimal power coefficient of the wind turbine, according to the equivalent machine speed ω r,eqand the maximum tip speed ratio λ opt the equivalent wind turbine G can be obtained weq of the wind speed υ eq ; Based on the principle of constant power loss, the collector network is equivalent. Let the connection impedance between the equivalent wind turbine G weq and the common connection point be Z weq , then:

[0082]

[0083] In the formula: n lk is the number of wind turbines upstream of line l-k, Z lk is the impedance between lines l-k in the wind farm, n w is the total number of wind turbines in the wind farm.

[0084] During the frequency modulation process, the output power P wi of the wind turbine G w,i is the sum of the captured mechanical power P m,i and the additional power ΔP k,i generated by releasing the rotor kinetic energy; Since the equivalent calculation requires that the equivalent kinetic energy before the disturbance is equal to the total kinetic energy of the wind turbines in the field, and the kinetic energy release progress of each unit is the same under the constraint control, it can be deduced that the kinetic energy released by the equivalent wind turbine is equal to the sum of the additional power ΔP wi generated by each wind turbine G k,i in the wind farm during the frequency modulation process:

[0085]

[0086] In the formula: ΔP k,eq is the kinetic energy released by the equivalent wind turbine; The mechanical power P m,i of the wind turbine and the rotational speed ω i have a non-linear relationship. P m,i will decrease as ω i decreases. Although the initial rotational speeds ω i0 of each wind turbine are different, ω i varies uniformly within the interval [ω min , ω i0 . At steady state, the mechanical power P weq captured by the equivalent wind turbine G m,eq can be approximately considered as the sum of the mechanical powers P wi of all wind turbines G m,i :

[0087]

[0088] Since the output power P e,eq of the equivalent machine is P m,eq plus ΔP k,eqThe sum is such that under the tie-line consistency control, the output power curve P of the equivalent model e,eq (t) is basically consistent with the detailed model calculation curve.

[0089] After the wind farm considering the tie-line control is equivalent to a single machine, the frequency response curve is calculated based on the single-machine equivalent model of the wind farm, and it is compared with the frequency response curve of the detailed model. The results show that the single-machine equivalent model of the wind farm considering the tie-line control of the wind farm has good accuracy in frequency calculation, which proves the applicability of the single-machine equivalent model adopted in this application in frequency calculation.

[0090] The realization process of constructing the frequency control optimization problem of the wind-storage-load coordinated power system described in step (3) is as follows:

[0091] The frequency security index η = {R cof , f nad1 , f p1 , f nad2 , m1, f ss} is used to comprehensively evaluate the frequency security of the system; where: R cof is the initial frequency change rate, which reflects the frequency change speed in the initial time period after the disturbance. Due to measurement and action delays, etc., generally, the frequency change rate within 1 second after the disturbance can be taken, and its calculation formula is:

[0092]

[0093] Where: f1 is the system frequency at 1 s after the disturbance, f0 is the initial frequency, and Δt is the detection interval, which is set to 1 s in this embodiment. f nad1 , f nad2 are respectively the lowest frequencies of the two frequency dips; f p1 is the frequency peak value during the two dips, m1 = f p1 -f nad1 is the amplitude of the first oscillation of the frequency in the dynamic process. To suppress the oscillation, it is stipulated that m1 ≤ ε, and ε is a set decimal; f ss is the steady-state frequency after the fault.

[0094] The expression of the tie-line signal x ref (t) is:

[0095]

[0096] Where: t1 is the start time of the fault, t2 is the demarcation point between the frequency regulation stage and the recovery stage, and t2 - t1 is denoted as T c , t3 is the time when the frequency regulation control exits; The value of T c determines the period of the sine function in the frequency regulation stage. The smaller T c , the initial moment xref (t) changes faster; the parameter b is a positive number used to control the speed recovery speed. The smaller b is, the slower the speed recovers. Generally, b = 0.1 can be taken; θ is a decimal number used to ensure the continuity of x ref (t) at time t2, θ = -(1 + e 40b ) -1 ; It can be seen that in the pinning signal, the parameters b and θ are known, while T c needs to be further optimized.

[0097] In the case of relatively serious faults, wind power frequency regulation needs to cooperate with other control measures of the system to ensure system frequency safety. Therefore, it is necessary to give full play to the potential of wind power frequency regulation on the premise of ensuring frequency safety, and take reducing the control cost as the goal to jointly optimize the wind farm pinning signal and other control measures; assume that the energy storage output power after disturbance is P ES , the demand response power is P dr , and the pinning signal x ref (t) depends on the value of T c , so the control variable to be optimized can be recorded as: Z = (P ES , P dr , T c ) T , and the frequency control problem of wind-storage-load coordination can be described as:

[0098]

[0099] In the formula: F is the economic cost of frequency control; c1 and c2 are the cost factors of energy storage and demand response respectively; g(·) represents the nonlinear dynamic mapping relationship between the control measure and the system frequency, which can be determined by solving the differential-algebraic equation system; is the maximum value of R cof ; f min is the minimum frequency value; f ss,min is the lowest frequency allowed by the system at steady state; the pinning signal parameter T c has a certain adjustment range, T c are the upper and lower bounds respectively, are the upper bounds of the energy storage output power and the demand response power after disturbance respectively.

[0100] The implementation process of solving the optimal control strategies of wind power and energy storage, etc. based on the sensitivity method described in step (4) is as follows: For the nonlinear dynamic optimization problem described by formula (8), an approximate linearization method based on sensitivity is used for iterative solution. The basic steps are as follows:

[0101] 1) Let the iteration step a = 0, and the initial control variable Z (0) takes a random number within the set interval;

[0102] 2) At the a-th iteration, let the control variable Z = Z (a) , and calculate the corresponding system frequency response curve f(t) through numerical simulation, and calculate each frequency security index η = {R cof , f nad1 , f p1 , f nad2 , m1, f ss};

[0103] 3) Obtain the sensitivity of the frequency security index η to the control variable Z by the perturbation method. Taking R cof as an example, calculate its sensitivity to the tie signal parameter T c , the output power P ES of the energy storage after perturbation, and the demand response power P dr , and convert the corresponding inequality in Equation (8) into Similarly, convert all other inequalities into linear inequalities, and Equation (8) is converted into a linear programming problem;

[0104] 4) Solve the obtained linear programming problem to obtain the change ΔZ (a) of the control variable at the a-th step, and correct the control variable Z to be optimized to obtain Z (a+1) = Z (a) + γ·ΔZ (a) , and generally γ = 0.3 can be taken;

[0105] 5) If ||ΔZ (a) || ≤ ζ, where ζ is a set decimal number, the optimization ends and the optimized result Z opt = Z (a+1) is output; otherwise, let a = a + 1, jump to step 2), and continue the optimization.

[0106] Apply the sensitivity method in step 4 to optimize the wind-storage-load coordinated frequency control strategy, and obtain the tie signal parameter T c of the offshore wind farm, as well as P ES and P dr . Build a single-machine equivalent model of the system in Matlab / Simulink software to obtain the corresponding system frequency response curve f(t), calculate various frequency security indexes, and verify whether the set frequency security requirements are met under this parameter condition.

[0107] Embodiment 2

[0108] In this embodiment, a specific implementation example of applying the wind-storage-load coordinated frequency control method of the power system considering the tie control of the deep-sea offshore wind farm as described above to the 3-machine 9-node system with the offshore wind farm connected is provided. As Figure 2 shown, in the system, the offshore wind farm consists of 6 doubly-fed wind turbines Gw1 -G w2 It is composed of, and is connected to the grid at node 6 through an undersea AC cable. Energy storage and demand response are respectively configured at nodes 7 and 9.

[0109] First, obtain the power system data and the parameters of the wind turbine and the pitch controller. Among them, the power system data includes the parameters of the synchronous generator and the governor and the control parameters of the energy storage system.

[0110] In this embodiment, the parameters of the synchronous generator and the governor are shown in Table 1:

[0111] Table 1 Parameters of the synchronous generator and the governor

[0112]

[0113]

[0114] In this embodiment, the dynamic process when the energy storage and demand response do not adjust the power is not considered, and it is assumed that their action times are 200 milliseconds and 90 seconds after the fault respectively. The maximum adjustable powers of the energy storage and demand response are 40 MW and 50 MW respectively, and the cost factors c1 and c2 of the energy storage and demand response are 200,000 yuan / MW and 100,000 yuan / MW respectively;

[0115] In the embodiment of the present invention, the parameters of the doubly-fed wind turbine and its controller are shown in Table 2:

[0116] Table 2 Parameters of the wind turbine and the controller

[0117]

[0118] The capacity of each wind turbine is 25 MVA, and the total capacity of the wind farm is 150 MVA. Among them, the transformation ratio of T1-T6 is 575 V / 25 kV, the capacity is 30 MVA, and the short-circuit impedance is 0.04 pu. The impedances of lines 10-17, 17-18, 18-19, 10-20, 20-21, and 21-22 are all 0.126 + 1.066 j ohms. Figure 2

[0119] Establish an equivalent model of a single wind turbine in the wind farm considering the pitch control of the wind farm. In this embodiment, the parameters of the equivalent wind turbine are shown in Table 3:

[0120] Table 3 Parameters of the equivalent wind turbine

[0121]

[0122] ​After the wind farm considering the pinning control is equivalent to a single machine, the frequency response curve is calculated based on the single-machine equivalent model of the wind farm, and it is compared with the frequency response curve of the detailed model to verify the applicability of the single-machine equivalent model in frequency calculation. Taking the example system as an example, Figure 3 Figure 5 shows the comparison diagram of the wind power and frequency response curves calculated based on the equivalent model and the detailed model. It can be seen from the figure that the calculation results of the single-machine equivalent model and the detailed model are basically in agreement. However, due to certain deviations in the wind power obtained by the single-machine equivalent model, there are also small deviations in the frequency response curve. At 40 s, the deviation of the lowest frequency value is about 0.03 Hz. Generally speaking, the accuracy of the single-machine equivalent model can meet the requirements of frequency control decision-making.

[0123] Based on the sensitivity method, the optimal control strategy of the wind-storage-load coordinated power system frequency control is solved to obtain the optimal control strategies of wind power and energy storage. In this embodiment, an energy storage with a rated capacity of 80 MW·h and a rated power of 40 MW is configured in the system; the maximum adjustable power of the demand response is 50 MW. At 10 s, the system load suddenly increases by 70 MW. Take f min and f ss,min as 59.5 Hz and 59.8 Hz respectively, take 1 Hz / s, T c take 40 s and 25 s respectively, ε = 0.03 Hz, ζ = 0.01. Using the sensitivity method in step (4), the wind-storage-load coordinated frequency control strategy is optimized and calculated. After 5 iterations, the calculation converges, taking about 800 s. In the obtained optimal control strategy, the pinning signal parameter T c of the offshore wind farm is 36.82 s, P ES and P dr are 26.324 MW and 8.954 MW respectively, and the control cost is 6.16032 million yuan; the system frequency response is as shown by the solid line in Figure 5 . It can be seen from the figure that R cof is 0.112 Hz / s, the two lowest frequency values are 59.679 Hz and 59.501 Hz respectively, and the difference between f p1 and f nad1 is 0.03 Hz, meeting the set frequency safety requirements.

[0124] To analyze the influence of the change of the pinning signal parameter on the frequency response curve, keeping P ES and P dr unchanged, simulations are carried out by taking T c as 28 s and 40 s respectively. The corresponding frequency response curves for different T c are as shown in Figure 5 , and its frequency safety index is shown in Table 4.

[0125] Table 4 System frequency safety indicators under different restraint signals

[0126]

[0127] As can be seen from Table 4, when T c is small, due to the rapid release of kinetic energy, R cof is small and f nad1 is large, but the lowest frequency point f nad2 is low. As T c increases, R cof gradually increases, f nad1 decreases, and the oscillation amplitude m1 increases accordingly, but f nad2 increases somewhat. Thus, when T c is small, short-term power support can be improved, but it is likely to cause f nad2 to exceed the limit. At this time, a larger P ES is required to ensure that f nad2 does not exceed the limit; when T c is large, f nad2 can be increased, but R cof and the oscillation amplitude will also increase. Increasing P ES can comprehensively improve the system frequency security, but the control cost will increase accordingly. Therefore, the present invention formulates a frequency control strategy by co-optimizing P ES , P dr and T c to enable the rapid recovery of the wind power system under severe faults.

[0128] Example 3

[0129] As a second aspect of the present invention, the present application further provides an electronic device, including: one or more processors; a memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the wind-storage-load coordinated control method considering the restraint control of the deep-sea wind farm as described above. In addition to the above-mentioned processors, memory, and interfaces, any device with data processing capabilities where the device in the embodiment is located usually includes other hardware according to the actual functions of the device with data processing capabilities, which will not be elaborated here.

[0130] Example 4

[0131] As a third aspect of the present invention, the present application further provides a computer-readable storage medium, on which computer instructions are stored. When the instructions are executed by a processor, the wind-storage-load collaborative control method involving the far-reaching offshore wind farm restraint control as described above is implemented. The computer-readable storage medium may be an internal storage unit of any device with data processing capabilities described in any of the foregoing embodiments, such as a hard disk or memory. The computer-readable storage medium may also be an external storage device, such as a plug-in hard disk, a Smart Media Card (SMC), an SD card, a Flash Card, etc. equipped on the device. Further, the computer-readable storage medium may also include both an internal storage unit of any device with data processing capabilities and an external storage device. The computer-readable storage medium is used to store the computer program and other programs and data required by any device with data processing capabilities, and may also be used to temporarily store the data that has been output or will be output.

[0132] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention through logical analysis, reasoning, or limited experiments based on the concept of the present invention on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A wind-storage-load coordinated control method considering the restraint control of a far-reaching offshore wind farm, characterized in that The method steps include: Obtain power system data and the parameters of wind turbines and constraint controllers; Establish a single-machine equivalent model of a wind farm considering the constraint control of the wind farm; Construct an optimization problem for the frequency control of a wind-storage-load coordinated power system with the minimum economic cost of frequency control as the objective under severe faults. The frequency control optimization problem uses the output power of the energy storage, the demand response power, and the duration of the frequency modulation stage of the constraint signal as control variables; Solve the power system frequency control optimization problem based on the sensitivity method to obtain the optimal control strategies for wind power and energy storage.

2. The wind-storage-load coordinated control method considering the restraint control of a far-reaching offshore wind farm according to claim 1, characterized in that, The power system data includes: Synchronous generator G s with capacity S g,s , inertia time constant H g,s and damping coefficient D s ; for a steam turbine generator, the governor parameters include governor gain K st , reheater coefficient F H , reheater time constant T R and governor time constant T g ; for a hydro generator, the governor parameters include gain K ht , water hammer effect time constant T w and hydro turbine governor time constants T2, T3 and T4; Energy storage system control parameters, including the maximum adjustable power P ES , cost factor c1, and response time t ES ; Demand response control parameters, including the maximum adjustable power P dr , the cost factor c2, and the response time t dr .

3. A wind-storage-load coordinated control method considering the restraint control of a far-reaching offshore wind farm according to claim 1, characterized in that, The parameters of the wind turbines and constraint controllers include: The impedance Z between lines l-k in the wind farm lk and the capacity S wi of the wind turbine G wi , the inertia time constant H wi and the capacity S Ti of the generator terminal transformer and the short-circuit impedance Z Ti ; Obtain the wind farm pinning control topology structure and the parameters of the pinning controller, including the proportional coefficient and the integral coefficient k p 、k i 。 4. A wind-storage-load coordinated control method considering the restraint control of a far-reaching offshore wind farm according to claim 1, characterized in that The establishment of the single-machine equivalent model of the wind farm considering the constraint control of the wind farm is specifically as follows: The capacity of the equivalent wind turbine is equal to the sum of the capacities of each wind turbine in the wind farm; Before the disturbance, at steady state, the mechanical power P captured by the equivalent wind turbine m,eq is equal to the output power P at the grid connection point of the wind farm PCC,0 plus the losses P within the wind farm loss ; According to the maximum power tracking curve of the wind turbine, the corresponding rotational speed ω of the equivalent wind turbine is obtained r,eq , and based on the rotational speed ω r,eq of the equivalent wind turbine and the maximum tip speed ratio λ opt the wind speed υ weq of the equivalent wind turbine unit G eq is obtained; The connection impedance between the equivalent wind turbine unit and the point of common coupling is set as: Where n lk is the number of upstream wind turbines of line l-k, Z lk is the impedance between lines l-k in the wind farm, n w is the total number of wind turbines in the wind farm; During the frequency modulation process, the kinetic energy released by the equivalent wind turbines is equal to the sum of the additional power ΔP generated by each wind turbine in the wind farm during the frequency modulation process k,i : The additional power ΔP generated by the wind turbine i during the frequency regulation process k,i is expressed as follows: where x ref is the wind farm restraint signal; x i is the consistency state variable of the wind turbine; a ij is the communication weight; g i indicates whether the wind turbine receives the restraint signal; k p , k i respectively represent the proportional coefficient and integral coefficient of the restraint control; V = {1, 2, …, n w} represents the set of wind turbine numbers, and n w is the total number of wind turbines in the wind farm; After the frequency modulation reaches a steady state, the mechanical power P captured by the equivalent wind turbines m,eq is approximately the sum of the mechanical powers P m,i of all wind turbine units.

5. A wind-storage-load coordinated control method considering the restraint control of a far-reaching offshore wind farm according to claim 4, characterized in that, The restraint signal x ref (t) is expressed as: Wherein, t1 is the fault start time, t2 is the demarcation point between the frequency modulation stage and the recovery stage, and t2 - t1 is denoted as T c , t3 is the frequency modulation control exit time; the parameter b is a positive number used to control the speed recovery speed. The smaller b is, the slower the speed recovery is; θ is a decimal number used to ensure the continuity of x ref (t) at the moment of t2.

6. A wind-storage-load coordinated control method considering the restraint control of a far-reaching offshore wind farm according to claim 1, characterized in that, The construction of the optimization problem for the frequency control of a wind-storage-load coordinated power system uses the frequency security index η to comprehensively evaluate the frequency security of the system, specifically including: Initial frequency change rate R cof , which is the frequency change rate within the set time after the perturbation and is used to reflect the frequency change speed in the initial time period after the perturbation occurs; The lowest frequencies f of the two frequency dips nad1 , f nad2 ; Frequency peak f during two drops p1 , The amplitude m1 of the first oscillation of the frequency during the dynamic process; Steady-state frequency f after fault ss .

7. A wind-storage-load coordinated control method considering the restraint control of a far-reaching offshore wind farm according to claim 6, characterized in that, For the optimization problem of frequency control in the wind-storage-load coordinated power system, with the goal of minimizing the economic cost of frequency control, the output power P of the energy storage after disturbance ES , the demand response power P dr , and the pinning signal x ref (t) and the duration T of the frequency modulation stage c are the control variables to be optimized Z=(P ES , P dr , T c ), T described as: where F is the economic cost of frequency control; c1 and c2 are the cost factors of energy storage and demand response respectively; g(·) represents the nonlinear dynamic mapping relationship between the control measure and the system frequency; is the initial frequency change rate R cof maximum value; ε is a set decimal; f min is the minimum frequency value; f ss,min is the lowest allowable frequency of the system at steady state; f ss,min is the minimum steady-state frequency after the fault; T c are the upper and lower bounds of the tie signal parameter T c regulation respectively; are the upper bounds of the energy storage output power and the demand response power after the disturbance respectively.

8. A wind-storage-load coordinated control method considering the restraint control of a far-reaching offshore wind farm according to claim 7, characterized in that, The optimization problem for the frequency control of a wind-storage-load coordinated power system is solved iteratively using an approximate linearization method based on sensitivity, and the steps are as follows: Randomly initialize the control variable Z; Calculate the corresponding system frequency response curve f(t) through numerical simulation and calculate each frequency security index; Obtain the sensitivity of the frequency security index η to the control variable Z by the perturbation method, and convert all the security index constraint inequalities into linear inequalities, and transform the frequency control optimization problem into a linear programming problem; Solve the obtained linear programming problem, obtain the change amount of the control variable, and correct the control variable Z to be optimized; Repeat the optimization until the change amount of the control variable is less than the set threshold.

9. An electronic device, characterized in that, Include: One or more processors; A memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the wind-storage-load coordinated control method considering the constraint control of a deep-sea far-field wind farm as described in any one of claims 1-8.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it realizes the steps of the wind-storage-load coordinated control method considering the constraint control of a deep-sea far-field wind farm as described in any one of claims 1-8.

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