A wind farm optimal control method based on rotor kinetic energy upward frequency modulation

Abstract

The application discloses a wind farm optimal control method based on rotor kinetic energy upward frequency modulation, comprising: real-time monitoring of wind farm grid-connected point frequency, starting upward frequency modulation function when the frequency is lower than the lower limit of frequency modulation dead zone, recording relevant parameters; continuously monitoring wind farm frequency and each wind turbine state, judging whether to exit frequency modulation state; updating total active power given value according to wind farm virtual inertia time constant and primary frequency modulation coefficient; updating operation mode and wind turbine state according to frequency modulation duration, wind turbine speed, mechanical power and active power, determining active power maximum output, realizing speed and mechanical load protection; optimizing distribution of each wind turbine active output, issuing instructions, realizing upward frequency modulation. The application optimizes distribution of wind farm frequency modulation power, realizes flexible rotor speed recovery control of each wind turbine, reduces mechanical power loss of wind turbine during wind farm utilization of rotor kinetic energy upward frequency modulation, reduces frequency secondary drop amplitude, improves performance and economy of wind farm participation in upward frequency modulation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system wind farm frequency modulation, in particular to a wind farm optimization control method based on rotor kinetic energy upward frequency modulation. BACKGROUND

[0002] The penetration rate of wind power generation in the power system is increasing, which reduces the system inertia response and primary frequency modulation capability. Therefore, in view of the frequency problem after the wind power is connected to the grid, some wind farm grid connection guidelines and standards at home and abroad propose that the wind farm connected to the grid should have the same frequency modulation capability as the conventional power plant. Since the power electronic converter of wind power has a flexible active power control system, the wind farm connected to the grid can use the ability to flexibly adjust the active power to improve the frequency stability of the power system.

[0003] The existing wind farm uses the rotor kinetic energy upward frequency modulation method, and in the process of multiple wind turbines cooperating to output, unreasonable output distribution will cause large mechanical power loss, which will release too much rotor kinetic energy of the wind turbine, so that the wind turbine needs to absorb more power in the rotor speed recovery stage, thereby increasing the secondary frequency drop amplitude.

[0004] Therefore, in order to meet the standard of wind farm participating in power system frequency modulation, reduce the mechanical power loss of wind turbine during frequency modulation, and reduce the secondary frequency drop amplitude, it is necessary to optimize the distribution of wind farm frequency modulation power and the flexible rotor speed recovery control of each wind turbine. SUMMARY

[0005] The present application aims to overcome the shortcomings and shortcomings of the prior art, and provides a wind farm optimization control method based on rotor kinetic energy upward frequency modulation, which optimizes the distribution of wind farm frequency modulation power, realizes the flexible rotor speed recovery control of each wind turbine, reduces the mechanical power loss of wind turbine during the wind farm uses rotor kinetic energy upward frequency modulation, reduces the secondary frequency drop amplitude, improves the performance and economy of wind farm participating in upward frequency modulation, and improves the problem that the existing method causes large mechanical power loss in the process of multiple wind turbines cooperating to output.

[0006] To achieve the above purpose, the technical scheme provided by the present application is: a wind farm optimization control method based on rotor kinetic energy upward frequency modulation, comprising:

[0007] Step S1: Real-time monitoring of wind farm grid connection point frequency f, when less than the lower limit of wind farm frequency modulation dead zone, then start the wind farm upward frequency modulation function, set the wind farm operation mode Mode=1, record the current total active power P of the wind farm e_startAs the wind farm upward frequency modulation power initial value, record the current time t0 as the wind farm upward frequency modulation initial time, record the current rotor speed of each wind turbine in the wind farm as the upward frequency modulation initial speed of each wind turbine, according to the upward frequency modulation initial speed of each wind turbine, screen the wind turbine participating in the wind farm upward frequency modulation, and enter step S2, if f is greater than the lower limit of the wind farm frequency modulation dead zone, set the wind farm operation mode Mode=0, and repeat step S1;

[0008] Step S2: record the current time t, real-time monitor the wind farm grid-connected point frequency f, the rotor speed of each wind turbine in the wind farm, the mechanical power captured by each wind turbine, the active power output by each wind turbine and the wind farm operation mode, judge whether the wind farm meets the exit upward frequency modulation condition, if yes, set the wind farm operation mode Mode=0, and return to step S1, otherwise enter step S3;

[0009] Step S3: based on the virtual inertia time constant of the wind farm, the primary frequency modulation coefficient and the wind farm upward frequency modulation power initial value P e_start obtained in step S1, update the total active power given value P e_ref of the wind farm;

[0010] Step S4: according to the current upward frequency modulation duration (t-t0), the total duration t p of participating in primary frequency modulation set by the wind farm, the rotor speed of each wind turbine in the wind farm, the mechanical power captured by each wind turbine in the wind farm and the active power output by each wind turbine in the wind farm, update the wind farm operation mode Mode, update the upward frequency modulation status status of each wind turbine in the wind farm, determine the active power maximum output unit value of each wind turbine in the wind farm, realize the wind turbine rotor speed and mechanical load protection;

[0011] Step S5: according to the rotor speed of each wind turbine in the wind farm, the mechanical power captured by each wind turbine in the wind farm, the active power output by each wind turbine in the wind farm, the total active power given value P e_ref of the wind farm obtained in step S3 and the active power maximum output unit value of each wind turbine obtained in step S4, realize the active power output optimization distribution of each wind turbine in the wind farm, issue the active power output instruction value to each wind turbine in the wind farm, and return to step S2.

[0012] Further, in step S1, the method of screening the wind turbine participating in the wind farm upward frequency modulation is as follows:

[0013] Traverse all the wind turbines running in the wind farm, if then mark the i-th wind turbine in the wind farm as the first type wind turbine, if The i-th wind turbine in the wind farm is marked as a second type wind turbine, and the first type wind turbine does not participate in the upward frequency regulation of the wind farm, and the second type wind turbine participates in the upward frequency regulation of the wind farm.

[0014] wherein, i∈[1,2,3,…,n], i represents the index of the wind turbine in the wind farm, n is the total number of wind turbines running in the wind farm, ωi is the current rotor speed unit value of the i-th wind turbine in the wind farm, r_start_min ωmin is the minimum rotor speed unit value of each wind turbine capable of participating in upward frequency regulation.

[0015] Further, in step S2, the method for determining whether the wind farm meets the exit upward frequency regulation condition is as follows:

[0016] If the current wind farm operation mode Mode=3, and the frequency f of the grid-connected point of the wind farm is greater than the lower limit of the wind farm frequency regulation dead zone, then the determination result is that the wind farm exits the upward frequency regulation, otherwise the determination result is that the wind farm continues to perform the upward frequency regulation.

[0017] Further, in step S3, the total active power given value P e_ref The calculation formula is as follows:

[0018] P e_ref = min{P e_start +P e_primary +P e_inertia ,P e_ref_max}

[0019]

[0020] In the formula, f n is the rated value of the grid-connected point frequency of the wind farm, Δf is the difference between the grid-connected point frequency of the wind farm and the rated value of the grid-connected point frequency of the wind farm, i.e. Δf=f-f n , P e_primary is the additional output of the primary frequency regulation of the wind farm, P e_inertia is the additional output of the inertia response of the wind farm, H is the equivalent inertia time constant of the wind farm, K is the equivalent frequency regulation coefficient of the wind farm, P e_ref_max is the upper limit value of P e_ref , which is determined according to the actual operation needs of the wind farm.

[0021] Further, in step S4, the method for updating the wind farm operation mode Mode is as follows:

[0022] When t-t0<t p , set Mode=1; when t-t0>t p and there exists i∈[1,2,3,…,n] such that Mode = 2; when t - t0> t p and for any i∈[1, 2, 3, …, n] have Mode = 3;

[0023] wherein, Pi is the current mechanical power per unit of the i-th wind turbine in the wind farm, Pi is the active reference per unit of the maximum power point tracking control of the i-th wind turbine in the wind farm, Pi is the maximum power point tracking curve coefficient of the i-th wind turbine in the wind farm, and ξ is the judgment threshold for the wind farm operation mode conversion.

[0024] Further, in step S4, the method for updating the status of the upward frequency regulation of each wind turbine in the wind farm is as follows:

[0025] status i = 0 (first type wind turbine)

[0026] (second type wind turbine)

[0027] wherein, status i is the upward frequency regulation status of the i-th wind turbine in the wind farm, is the current active power per unit of the i-th wind turbine in the wind farm, is the critical speed per unit of the i-th wind turbine start speed recovery, and ε is the judgment threshold for the maximum active power output switching back of the wind turbine.

[0028] Further, the assignment calculation is as follows:

[0029] wherein, is the rotor speed per unit of the i-th wind turbine in the wind farm at t = t p + t0.

[0030] Further, in step S4, the active power maximum output per unit of each wind turbine in the wind farm needs to satisfy:

[0031]

[0032] wherein, is the active power maximum output per unit of the i-th wind turbine in the wind farm, is the maximum electromagnetic torque limit per unit of the i-th wind turbine in the wind farm; and respectively are the i-th wind turbine in the wind farm when participating in the upward frequency regulation, drop to​ mechanical power per unit of the wind turbine and the active power per unit of the wind turbine; P * i is the active power per unit of the i th wind turbine in the wind farm fall to mechanical power per unit of the wind turbine, and δ is the active power disturbance constant when the wind turbine speed recovers.

[0033] Further, in step S5, the method for optimizing the active power output of each wind turbine in the wind farm to increase frequency is as follows:

[0034]

[0035]

[0036] The wind turbines in the wind farm with the status of increasing frequency of 1 participate in the optimization distribution of the wind farm power to increase frequency, wherein P * i is the active power per unit of the i th wind turbine in the wind farm, and the active power per unit of the wind turbine in the wind farm with the status of increasing frequency of 1 is equal to the maximum active power per unit of the wind turbine.

[0037] k i P * i is the optimization distribution coefficient of the i th wind turbine in the wind farm, and a i P * i is the optimization distribution intermediate variable of the i th wind turbine in the wind farm, P * i is the rated active power of the i th wind turbine in the wind farm, and P e_other P is the sum of the real values of the active power instructions of all the wind turbines in the wind farm with the status of increasing frequency of 1, and P m_odd P is the sum of the real values of the current mechanical powers of all the wind turbines in the wind farm with the status of increasing frequency of 1, P * i is the rotor inertia time constant of the i th wind turbine in the wind farm, and η is the distribution correction coefficient.

[0038] Compared with the existing wind farm frequency modulation, the present application has the following advantages and beneficial effects:

[0039] 1. The present application is suitable for both the wind farm working at the maximum power point and the wind farm operating in the overspeed load shedding, and has a wide range of application objects.

[0040] 2. The present application reduces the mechanical power loss of the wind farm during the frequency increase, reduces the rotor kinetic energy loss of the wind turbine during the frequency increase, and improves the frequency modulation capacity of the wind farm.

[0041] 3. The present application prevents the wind turbine rotor speed from falling to the threshold value through the flexible rotor speed recovery control of the wind turbine, and reduces the secondary frequency drop amplitude of the power grid during the rotor speed recovery of the wind turbine. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a flowchart provided by an embodiment of the present application.

[0043] Figure 2 is a structure diagram of a wind farm frequency modulation test system provided by an embodiment of the present application.

[0044] Figure 3 is a diagram of frequency variation of a wind farm grid connection point during upward frequency modulation of the wind farm provided by an embodiment of the present application.

[0045] Figure 4 is a diagram of mechanical power variation of a wind turbine during upward frequency modulation of the wind farm provided by an embodiment of the present application.

[0046] Figure 5 is a diagram of rotor kinetic energy variation of a wind turbine during upward frequency modulation of the wind farm provided by an embodiment of the present application. DETAILED DESCRIPTION

[0047] The present application will be further described below in conjunction with the drawings, and the following embodiments are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0048] As shown in the drawings, Figure 1 the present embodiment discloses a wind farm optimization control method based on rotor kinetic energy upward frequency modulation, comprising the following steps:

[0049] Step S11, set the wind farm operation mode Mode=0, and monitor the wind farm grid connection point frequency f in real time;

[0050] Step S12, judge whether the current wind farm grid connection point frequency is less than the lower limit of the wind farm frequency modulation dead zone, if yes, go to step S13, if not, return to step S11;

[0051] Step S13, set the wind farm operation mode Mode=1, record the current total active power P e_start as the initial value of the wind farm upward frequency modulation power, record the current time t0 as the initial time of the wind farm upward frequency modulation, and record the rotor speed of each wind turbine in the current wind farm as the initial rotor speed of each wind turbine for upward frequency modulation;

[0052] Step S14, according to the initial rotor speed of each wind turbine for upward frequency modulation, screen the wind turbines participating in the wind farm upward frequency modulation:

[0053] traverse all the wind turbines running in the wind farm, if the i-th wind turbine in the wind farm is marked as a first type wind turbine, if the i-th wind turbine in the wind farm is marked as a second type wind turbine, and the first type wind turbine does not participate in the wind farm upward frequency modulation, and the second type wind turbine participates in the wind farm upward frequency modulation;

[0054] wherein i∈[1,2,3,…,n], i represents the serial number of the i-th wind turbine in the wind farm, n is the total number of wind turbines in the wind farm, ωi is the current rotor speed of the i-th wind turbine in the wind farm, ω r_start_min ωmin is the minimum rotor speed of each wind turbine that can participate in the upward frequency regulation, and the reference value is 0.8pu;

[0055] Step S21, record the current time t, and real-time monitor the frequency f of the grid-connected point of the wind farm, the rotor speed of each wind turbine in the wind farm, the mechanical power captured by each wind turbine, the active power output by each wind turbine, and the operation mode of the wind farm;

[0056] Step S22, determine whether the wind farm meets the exit condition of the upward frequency regulation, if the current operation mode of the wind farm Mode=3, and the frequency f of the grid-connected point of the wind farm is greater than the lower limit of the dead zone of the frequency regulation of the wind farm, then exit the upward frequency regulation and return to step S11; otherwise, continue the upward frequency regulation and enter step S31.

[0057] Step S31, based on the equivalent inertia time constant of the wind farm, the equivalent frequency modulation coefficient, and the initial value P e_start of the upward frequency regulation power of the wind farm obtained in step S1, update the total active power given value P e_ref of the wind farm:

[0058] P e_ref = min{P e_start +P e_primary +P e_inertia ,P e_ref_max}

[0059]

[0060] wherein f n is the rated value of the frequency of the grid-connected point of the wind farm, Δf is the difference between the frequency of the grid-connected point of the wind farm and the rated value of the frequency of the grid-connected point of the wind farm, i.e. Δf=f-f n , P e_primary is the additional output of the primary frequency regulation of the wind farm, P e_inertia is the additional output of the inertia response of the wind farm, H is the equivalent inertia time constant of the wind farm, K is the equivalent frequency modulation coefficient of the wind farm, P e_ref_max is the upper limit value of P e_ref , which is determined according to the actual operation of the wind farm, and the reference value is 1.06P e_start .

[0061] Step S41, according to the current duration (t-t0) of the upward frequency regulation, the total duration t p, the rotor speed of each wind turbine in the wind farm, the mechanical power captured by each wind turbine in the wind farm and the active power output by each wind turbine in the wind farm, the wind farm operation mode Mode is updated:

[0062] Mode = 1 is set when t-t0 p , Mode = 2 is set when t-t0 p and there exists i∈[1,2,3,…,n] such that , Mode = 3 is set when t-t0 p and for any i∈[1,2,3,…,n], P

[0063] , where is the current mechanical power per unit of the i-th wind turbine in the wind farm, is the active power reference per unit of the maximum power point tracking control of the i-th wind turbine in the wind farm, is the maximum power point tracking curve coefficient of the i-th wind turbine in the wind farm, and ξ is the judgment threshold for the wind farm operation mode conversion, and the reference value is 0.003pu.

[0064] Step S42, the state status of the upward frequency adjustment of each wind turbine in the wind farm is updated:

[0065] status i = 0 (first type wind turbine)

[0066] (second type wind turbine)

[0067]

[0068] , where is the rotor speed per unit of the i-th wind turbine in the wind farm at t=t p +t0, status i is the upward frequency adjustment state of the i-th wind turbine in the wind farm, is the current active power per unit of the i-th wind turbine in the wind farm, is the critical speed per unit of the i-th wind turbine in the wind farm for starting speed recovery, and ε is the judgment threshold for the maximum active power output switching back to , and the reference value is 0.003pu.

[0069] Step S43, the maximum active power per unit of each wind turbine in the wind farm is determined:

[0070]

[0071] , where​ is the active power maximum output per unit of the i-th wind turbine in the wind farm, is the maximum electromagnetic torque limit per unit of the i-th wind turbine in the wind farm, the reference value is 1.02pu, and are the mechanical power per unit and the active power per unit of the i-th wind turbine in the wind farm when participating in upward frequency regulation, fall to ; is the mechanical power per unit of the i-th wind turbine in the wind farm fall to , and δ is the active power disturbance constant when the wind turbine speed recovers, the reference value is 0.02pu.

[0072] Step S51, according to the rotor speed of each wind turbine in the wind farm, the mechanical power captured by each wind turbine in the wind farm, the active power output by each wind turbine in the wind farm, the total active power given value P e_ref of the wind farm obtained in step S3 and the active power maximum output per unit of each wind turbine obtained in step S4, the active output optimization distribution of each wind turbine in the wind farm to the upward frequency regulation is realized:

[0073]

[0074] The wind turbine in the wind farm with the upward frequency regulation status status of 1 participates in the wind farm upward frequency regulation power optimization distribution, wherein is the active power per unit of the i-th wind turbine in the wind farm, and the active power per unit of the wind turbine in the wind farm with the upward frequency regulation status status not equal to 1 is equal to the active power maximum output per unit of the wind turbine;

[0075] k i is the optimization distribution coefficient of the i-th wind turbine in the wind farm, a i is the optimization distribution intermediate variable of the i-th wind turbine in the wind farm, is the rated active power of the i-th wind turbine in the wind farm, P e_other is the sum of the active power instruction true values of all wind turbines in the wind farm with the upward frequency regulation status status not equal to 1, P m_odd is the sum of the current mechanical power true values of all wind turbines in the wind farm with the upward frequency regulation status status of 1, is the rotor inertia time constant of the i-th wind turbine in the wind farm, and η is the distribution correction coefficient, the reference value is 1.

[0076] Step S52, the active power output instruction value is issued to each wind turbine in the wind farm, and returns to step S21.

[0077] Figure 2The topology diagram of the wind farm frequency modulation test system provided by the embodiment of the present application is divided into two areas, ten nodes, and BUS in the diagram represents the node bus. One area contains two synchronous generators, and the other area contains two synchronous generators and a wind farm, the wind farm contains three groups of wind turbines with different wind speeds, each group of wind turbines contains 10 wind turbines with a capacity of 15MW, the reference frequency of the wind farm frequency modulation test system is set to 50Hz, and the information of each synchronous unit, wind farm unit and load of the wind farm frequency modulation test system is shown in Table 1, Table 2 and Table 3.

[0078] Table 1: Synchronous unit information of the wind farm frequency modulation test system

[0079]

[0080] Table 2: Wind farm information of the wind farm frequency modulation test system

[0081]

[0082] Table 3: Load information of the wind farm frequency modulation test system

[0083]

[0084]

[0085] The simulation working condition is set, at t=50s, the load Load3 suddenly increases by 300MW, the lower limit of the frequency dead zone of the wind farm participating in upward frequency modulation is 49.95Hz, the duration t of the wind farm participating in inertia response and upward frequency modulation is 35s, the equivalent inertia time constant H of the wind farm is 8s, the equivalent frequency modulation coefficient K of the wind farm is 30, and the remaining parameters can be set to the reference values. p The simulation working condition is set, at t=50s, the load Load3 suddenly increases by 300MW, the lower limit of the frequency dead zone of the wind farm participating in upward frequency modulation is 49.95Hz, the duration t of the wind farm participating in inertia response and upward frequency modulation is 35s, the equivalent inertia time constant H of the wind farm is 8s, the equivalent frequency modulation coefficient K of the wind farm is 30, and the remaining parameters can be set to the reference values.

[0086] Simulation scheme Case1: the wind farm does not participate in frequency modulation.

[0087] Simulation scheme Case2: the wind farm participates in frequency modulation, power distribution is performed according to the rotor speed of the wind turbine, and the rotor speed of the wind turbine is recovered by using a conventional scheme at the end of frequency modulation.

[0088] Simulation scheme Case3: the wind farm participates in frequency modulation, power distribution and rotor speed recovery of the wind turbine are performed according to the scheme provided by the present application.

[0089] Figure 3 is a diagram of the frequency change of the wind farm grid connection point during the upward frequency modulation of the wind farm provided by the embodiment of the present application.

[0090] Figure 4 is a diagram of the active power change of the wind turbine during the upward frequency modulation of the wind farm provided by the embodiment of the present application.

[0091] The frequency support effect provided by the wind farm in the sustained frequency modulation time is determined by the equivalent inertia time constant of the wind farm and the equivalent frequency modulation coefficient of the wind farm.

[0092] Figure 5 is a mechanical power change diagram of a wind turbine during upward frequency modulation of a wind farm provided by the embodiment of the present application.

[0093] The simulation results show that the present application can significantly improve the minimum frequency in the case of sudden change of system load, and can improve the steady-state value of the frequency within the sustained frequency modulation time set by the wind farm. Compared with the traditional upward frequency modulation method of the wind farm, more mechanical power can be captured during the speed recovery of the wind farm, and more active power can be output, thereby causing smaller secondary frequency drop. In addition, the rotor speed recovery speed of the present application is faster, and the wind farm can be put into the next upward frequency modulation control earlier.

[0094] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above embodiments, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A wind farm optimal control method based on rotor kinetic energy up-frequency regulation, characterized in that, Comprise: Step S1: real-time monitoring the frequency f of the wind farm grid-connected point, when less than the lower limit of the wind farm frequency modulation dead zone, then start the wind farm upward frequency modulation function, set the wind farm operation mode Mode=1, record the current total active power P of the wind farm e_start As the initial value of the wind farm upward frequency modulation power, record the current time t0 as the initial time of the wind farm upward frequency modulation, record the current rotor speed of each wind turbine in the wind farm as the initial upward frequency modulation speed of each wind turbine, according to the initial upward frequency modulation speed of each wind turbine, screen the wind turbines participating in the wind farm upward frequency modulation, and enter step S2, if f is greater than the lower limit of the wind farm frequency modulation dead zone, set the wind farm operation mode Mode=0, and repeat step S1. Step S2: record the current time t, real-time monitoring of wind farm grid-connected point frequency f, each wind turbine rotor speed, each wind turbine captured mechanical power, each wind turbine output active power and wind farm operation mode, determine whether the wind farm meets the exit upward frequency modulation condition, if yes, set the wind farm operation mode Mode = 0, and return to step S1, otherwise enter step S3; Step S3: Based on the virtual inertial time constant of the wind farm, the primary frequency regulation coefficient, and the initial value P of the wind farm's upward frequency regulation power obtained in step S1. e_start Update the total active power setpoint P of the wind farm. e_ref ; Step S4: updating the wind farm operation mode Mode, updating the state status of each wind turbine in the wind farm, determining the active power maximum output standard value of each wind turbine in the wind farm, and realizing the wind turbine rotor speed and mechanical load protection according to the current duration of upward frequency modulation (t-t0), the total duration t of participating in primary frequency modulation set by the wind farm, the rotor speed of each wind turbine in the wind farm, the mechanical power captured by each wind turbine in the wind farm, and the active power output by each wind turbine in the wind farm. p Step S4: updating the wind farm operation mode Mode, updating the state status of each wind turbine in the wind farm, determining the active power maximum output standard value of each wind turbine in the wind farm, and realizing the wind turbine rotor speed and mechanical load protection according to the current duration of upward frequency modulation (t-t0), the total duration t of participating in primary frequency modulation set by the wind farm, the rotor speed of each wind turbine in the wind farm, the mechanical power captured by each wind turbine in the wind farm, and the active power output by each wind turbine in the wind farm. Step S5: according to the rotor speed of each wind turbine in the wind farm, the mechanical power captured by each wind turbine in the wind farm, the active power output by each wind turbine in the wind farm, the total active power given value P e_ref and the maximum active power output per unit value of each wind turbine obtained in step S4, the active power output optimization distribution of each wind turbine in the wind farm is realized, the active power output instruction value is issued to each wind turbine in the wind farm, and the process returns to step S2.

2. The wind farm optimal control method based on rotor kinetic energy up-conversion according to claim 1, characterized in that, In step S1, the method of screening wind turbines participating in wind farm upward frequency modulation is as follows: Traverse all the wind turbines in the wind farm, if then mark the i-th wind turbine in the wind farm as a first type wind turbine, if then mark the i-th wind turbine in the wind farm as a second type wind turbine, let the first type wind turbine not participate in the upward frequency regulation of the wind farm, and let the second type wind turbine participate in the upward frequency regulation of the wind farm. Wherein, i∈[1, 2, 3, …, n], i represents the label of the wind turbine in the wind farm, and n is the total number of wind turbines in operation in the wind farm, ωi is the current rotor speed unit value of the i th wind turbine in the wind farm, r_start_min ωmin is the minimum rotor speed unit value of each wind turbine capable of participating in upward frequency modulation.

3. The wind farm optimal control method based on rotor kinetic energy up-frequency regulation according to claim 2, characterized in that, In step S2, the method of determining whether the wind farm meets the exit upward frequency modulation condition is as follows: If the current wind farm operation mode Mode = 3, and the wind farm grid-connected point frequency f is greater than the lower limit of the wind farm frequency modulation dead zone, then the judgment result is that the wind farm exits upward frequency modulation, otherwise the judgment result is that the wind farm continues upward frequency modulation.

4. The wind farm optimal control method based on rotor kinetic energy up-conversion frequency according to claim 3, characterized in that, In step S3, the total active power setpoint P e_ref The calculation formula is as follows: P e_ref = min{P e_start + P e_primary + P e_inertia , P e_ref_max} In the formula, f n is the frequency rating of the wind farm grid connection point, and Δf is the difference between the frequency of the wind farm grid connection point and the frequency rating of the wind farm grid connection point, i.e. Δf = f-f n , P e_primary is the additional primary frequency modulation capacity of the wind farm, P e_inertia is the additional inertia response capacity of the wind farm, H is the equivalent inertia time constant of the wind farm, K is the equivalent frequency modulation coefficient of the wind farm, P e_ref_max is the upper limit value of P e_ref , which is determined according to the actual operation needs of the wind farm.

5. The wind farm optimal control method based on rotor kinetic energy up-frequency regulation according to claim 4, characterized in that, In step S4, the method of updating the wind farm operation mode Mode is as follows: When t-t0< t p , set Mode = 1; when t-t0> t p and there exists i ∈ [1, 2, 3, …, n] such that , set Mode = 2; when t-t0> t p and for any i ∈ [1, 2, 3, …, n], it has , set Mode = 3. wherein, Pmiis the current mechanical power per unit of the ith wind turbine in the wind farm, Pmiis the current mechanical power per unit of the ith wind turbine in the wind farm, Pmiis the current mechanical power per unit of the ith wind turbine in the wind farm, and ξ is a judgment threshold for the operation mode conversion of the wind farm.

6. The wind farm optimal control method based on rotor kinetic energy up-conversion frequency according to claim 5, characterized in that, In step S4, the method of updating the status of each wind turbine in the wind farm upward frequency modulation is as follows: status i = 0 (first type fan) (second type of fan) In the formula, status i This represents the upward frequency regulation state of the i-th wind turbine in the wind farm. Let be the per-unit value of the current active power of the i-th wind turbine in the wind farm. Let ε be the per-unit value of the critical speed at which the starting speed of the i-th wind turbine in the wind farm recovers, and let ε be the value of the maximum active power output of the wind turbine when switching back to its starting speed. The judgment threshold.

7. The wind farm optimal control method based on rotor kinetic energy up-conversion frequency according to claim 6, characterized in that, The assignment of the value of A is calculated as follows: wherein is the rotor speed of the i-th wind turbine in the wind farm at t = t p t0.

8. The wind farm optimal control method based on rotor kinetic energy up-conversion frequency according to claim 7, characterized in that, In step S4, the active power maximum output per unit value of each wind turbine in the wind farm needs to meet: wherein, Pmax,i is the maximum active power output per unit of the i th wind turbine in the wind farm, Tmax,i is the maximum electromagnetic torque limit per unit of the i th wind turbine in the wind farm; and Pmech,i and Pactive,i are the mechanical power per unit and the active power per unit of the i th wind turbine when participating in upward frequency regulation, respectively; Pmech,i and Pactive,i are the mechanical power per unit and the active power per unit of the i th wind turbine when participating in upward frequency regulation, respectively; Pmech,i and Pactive,i are the mechanical power per unit and the active power per unit of the i th wind turbine when participating in upward frequency regulation, respectively; Pmech,i is the mechanical power per unit of the i th wind turbine when participating in upward frequency regulation, Pmech,i is the mechanical power per unit of the i th wind turbine when participating in upward frequency regulation, Pmech,i is the mechanical power per unit of the i th wind turbine when participating in upward frequency regulation, and δ is the active power disturbance constant when the wind turbine speed recovers.

9. The wind farm optimal control method based on rotor kinetic energy up-conversion frequency according to claim 8, characterized in that, In step S5, the method of optimizing the distribution of active power output of each wind turbine in the wind farm upward frequency modulation is as follows: The wind turbine with the upward frequency regulation status of 1 in the wind farm participates in the optimal distribution of the upward frequency regulation power of the wind farm, wherein The active power instruction unit value of the i-th wind turbine in the wind farm is equal to the maximum active power output unit value of the wind turbine, and the active power instruction unit value of the wind turbine with the upward frequency regulation status of 1 in the wind farm is equal to the maximum active power output unit value of the wind turbine. k i is the optimized allocation coefficient of the i-th wind turbine in the wind farm, a i is the optimized allocation intermediate variable of the i-th wind turbine in the wind farm, is the rated active power of the i-th wind turbine in the wind farm, P e_other is the sum of the real values of the active power commands of all wind turbines in the wind farm whose up-regulation status status is not 1, P m_odd is the sum of the real values of the current mechanical powers of all wind turbines in the wind farm whose up-regulation status status is 1, is the rotor inertia time constant of the i-th wind turbine in the wind farm, η is the allocation correction coefficient.

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