A wind-solar-storage collaborative frequency control method and system based on frequency index constraint

Abstract

The application discloses a wind-solar-storage collaborative frequency control method and system based on frequency index constraint, belongs to the field of active support of power grid frequency of wind-solar-storage hybrid power station, and the method comprises the following steps: firstly, disturbance boundary values of wind-solar-storage participating in frequency modulation in turn are obtained based on frequency safety index constraint. According to the frequency change rate at the initial time of disturbance, the disturbance value suffered by the system is obtained, and the disturbance boundary value is compared to judge the interval to which the disturbance value belongs, and corresponding frequency modulation instructions are generated to control the active power output of wind-solar-storage. The application can realize adaptive frequency support control of the wind-solar-storage hybrid power station grid-connected system under different working conditions, can accurately allocate the required active power output of wind-solar-storage according to the demand of frequency modulation, can reliably meet the frequency modulation demand and guarantee the safety of power grid frequency, can fully utilize the rotor kinetic energy of wind turbine units in the power station and avoid frequency secondary drop, and can effectively improve the state of charge of energy storage units in the power station.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of grid frequency active support of wind-solar-storage hybrid station grid-connected system, and more particularly relates to a wind-solar-storage collaborative frequency control method and system based on frequency index constraint. BACKGROUND

[0002] In recent years, the penetration rate of fluctuating renewable energy such as wind power and photovoltaic power in the power system has rapidly increased. The proportion of traditional synchronous generators has decreased, resulting in a significant decrease in system inertia and frequency regulation capacity. The characteristics of dispersion, weak support, low inertia and low disturbance resistance of new energy pose serious challenges to new power systems, seriously threatening the stability of the power system. Therefore, domestic and foreign power grid specifications have been introduced to address new energy grid connection, clearly stipulating the requirements for frequency modulation technology. New energy stations need to have the ability to actively respond to changes in grid frequency and reserve standby frequency modulation power to deal with sudden situations such as load surges.

[0003] In existing engineering applications, traditional new energy frequency support control often uses fixed droop or virtual inertia control parameters to improve frequency deviation and rate of change. This method can effectively suppress frequency fluctuations, but lacks a basis for controller parameter tuning, cannot accurately meet system frequency modulation requirements, and relies on online monitoring for evaluation, making it difficult to achieve early warning. SUMMARY

[0004] In view of the defects of the related art, the present application aims to generate wind-solar-storage hybrid station frequency modulation instructions based on the constraint of frequency safety index according to the size of the disturbance when a frequency event occurs in the system, and to control the active power output of wind, solar and storage, in order to solve the problems of lack of basis for controller parameter tuning, insufficient development of the frequency modulation advantages of various new energies, and excessive dependence on energy storage response in existing wind-solar-storage collaborative control.

[0005] To achieve the above-mentioned purpose, the present application provides a wind-solar-storage collaborative frequency control method based on frequency index constraint, applied to a wind-solar-storage hybrid station grid-connected system, which includes wind turbines, battery energy storage units, an AC power grid and a plurality of parallel photovoltaic power generation units; the photovoltaic power generation units, wind turbines and battery energy storage units are respectively connected to the same AC bus through their respective converters and transformers, and are integrated into the AC power grid, the wind-solar-storage collaborative frequency control method based on frequency index constraint comprises:

[0006] The photovoltaic power generation units are controlled to reduce the load and reserve standby power, and the maximum comprehensive inertia control coefficient of the wind turbine is set according to the wind speed at which the wind turbine is located;

[0007] The preset system frequency safety index is used as the first constraint, and the disturbance boundary ΔP LG and the disturbance boundary ΔPLPV Using the maximum integrated inertia control coefficient of the wind turbine as the second constraint, and based on the first and second constraints, calculate the disturbance boundary ΔP for starting the frequency regulation of the battery energy storage unit. LW ;

[0008] Monitor the frequency variation rate of the wind-solar-storage hybrid grid-connected system to obtain the disturbance value ΔP experienced by the system. L And based on the disturbance value ΔP L Based on the comparison results with each disturbance boundary, implement the corresponding frequency modulation strategy:

[0009] If the disturbance value ΔP L Belongs to ΔP LG <ΔP L ≤ΔP LPV In the specified range, the additional power of the photovoltaic power generation unit is calculated based on the preset system frequency security index to meet the frequency regulation requirements;

[0010] If the disturbance value ΔP L Belongs to ΔP LPV <ΔP L ≤ΔP LW Within the specified range, the photovoltaic power generation unit outputs at its maximum capacity. Based on the preset system frequency safety index, the active power of the wind turbine is calculated, and the comprehensive inertial control coefficient is adjusted based on the calculated active power to meet the frequency regulation requirements.

[0011] If the disturbance value ΔP L Belongs to ΔP L >ΔP LW During the interval, both photovoltaic power generation units and wind turbine units operate at their maximum capacity, and the active power output of the battery energy storage unit is controlled according to the state of charge to meet the frequency regulation requirements.

[0012] Optionally, the step of controlling the photovoltaic power generation unit to reserve backup power and adjusting the maximum comprehensive inertia control coefficient of the wind turbine according to the wind speed at which the wind turbine is located includes:

[0013] The initial load shedding rate σ0 of the photovoltaic power generation unit is set, and the reserve power corresponding to the initial load shedding rate σ0 is used for disturbance frequency regulation control; the reserve power ΔP PV =(1-σ0)P MPPT ;

[0014] Among them, P MPPT This represents the power value of the photovoltaic power generation unit when it operates at its maximum power point, and the value of σ0 ranges from 5% to 22%.

[0015] The rotational speed extreme value of the wind turbine and the wind turbine power increase limit value are obtained, and the rotational speed change amount is obtained according to the rotational speed extreme value and the wind turbine power increase limit value, respectively, and the maximum rotational speed change amount Δω of the wind turbine is determined from the rotational speed change amount; the calculation formula of the maximum rotational speed change amount Δω is:

[0016]

[0017] ω r0 is the initial rotational speed of the wind turbine, ω rmax and ω rmin are the maximum and minimum rotational speeds of the wind turbine, P n represents the rated power of the wind turbine, k opt represents the maximum power tracking control coefficient, H w represents the wind turbine inertia coefficient, and t h is the wind turbine frequency modulation duration.

[0018] The maximum comprehensive inertia control coefficient of the wind turbine is set according to the maximum rotational speed change amount Δω.

[0019]

[0020]

[0021] wherein k D is the droop coefficient, k H is the virtual inertia coefficient; ROCOF and Δf max are the maximum frequency change rate and the maximum frequency drop amplitude corresponding to the system disturbance value ΔP LPV ; k opt represents the maximum power tracking coefficient of the wind turbine; P ref and P m (v, ω rmin ) represent the active power instruction value of the wind turbine at the initial rotational speed ω r0 and the minimum rotational speed ω rmin ; P MPPT (v, ω r0 ) and P MPPT (v, ω rmin ) represent the power value of the maximum power operating point of the wind turbine at the initial rotational speed and the minimum rotational speed; t n represents the time when the frequency reaches the extreme point; ΔE k represents the wind turbine rotor kinetic energy change amount; and P m (v, ω r ) represents the mechanical power of the wind turbine.

[0022] Optionally, the preset system frequency safety index is taken as a constraint, and the disturbance boundary ΔP LG ​The disturbance boundary ΔP of starting the frequency modulation of the wind turbine LPV The disturbance boundary ΔP of starting the frequency modulation of the battery energy storage unit is calculated by taking the preset system frequency safety index constraint and the maximum comprehensive inertia control coefficient of the wind turbine as constraints LW , comprising:

[0023] The equivalent inertia coefficient and the damping coefficient of the wind-solar-storage hybrid station grid-connected system are obtained, and the preset system frequency safety index is determined; based on the preset system frequency safety index, the disturbance value corresponding to each safety index is calculated by using the SFR model theoretical formula, and the minimum value is taken as the disturbance boundary ΔP of starting the frequency modulation of the photovoltaic LG ; wherein the preset system frequency safety index includes: the frequency change rate is not more than-0.5Hz / s, the maximum frequency deviation is not more than-0.5Hz, and the steady-state frequency deviation is not more than-0.2Hz;

[0024]

[0025] Wherein, R represents the speed governor setting difference coefficient, H eq represents the equivalent inertia coefficient of the system, D eq represents the equivalent damping coefficient of the system, The limit value-0.5Hz / s, Δf max The limit value-0.5Hz, Δf ss The limit value-0.2Hz, ΔP L1 , ΔP L2 , ΔP L3 respectively represent the disturbance boundary when the limit value of the initial frequency change rate, the maximum frequency deviation and the steady-state frequency deviation is taken, t n represents the time when the frequency reaches the extreme point, ξ represents the damping ratio, ω n represents the natural oscillation angular velocity, ω d represents the damping angular velocity, F H represents the proportion of the high-pressure cylinder work of the prime mover, T R represents the reheating time constant;

[0026] The disturbance boundary value ΔP LPV of the photovoltaic power generation unit is calculated by using the SFR model theoretical formula when the output is limited;

[0027]

[0028] According to the set maximum comprehensive inertia control coefficient of the wind turbine, the disturbance boundary value ΔP LW of the wind turbine is calculated by using the SFR model theoretical formula when the rotor kinetic energy is limited;

[0029] Wherein

[0030]

[0031] H' = H + H eq represents the equivalent inertia coefficient of the system after adding the fan comprehensive inertia control; D' eq represents the equivalent damping coefficient of the system after adding the fan comprehensive inertia control; t' n represents the frequency extreme time after adding the fan; H G represents the inertia constant of the synchronous machine; S sys represents the total capacity of the system; S w represents the capacity of the wind turbine generator set; S G represents the capacity of the synchronous machine.

[0032] Optionally, the disturbance value ΔP L The calculation formula is:

[0033]

[0034] H = H + H eq is the inertia constant of the wind-solar-storage hybrid station grid-connected system, and f represents the grid frequency.

[0035] Optionally, if the disturbance value ΔP L belongs to the interval ΔP LG < ΔP L ≤ ΔP LPV , the incremental power of the photovoltaic power generation unit is calculated based on the preset system frequency safety index to meet the frequency modulation demand, including:

[0036] The incremental power P PV of the standby power of the photovoltaic power generation unit is calculated based on the preset system frequency safety index.

[0037]

[0038] ΔP = ΔP , Δf max = -0.5 Hz / s, Δf ss = -0.5 Hz, and Δf PV = -0.2 Hz.

[0039] The DC capacitor side voltage U PV of the photovoltaic power generation unit is adjusted based on the calculated incremental power P L to meet the frequency modulation demand.

[0040] Optionally, if the disturbance value ΔP LPV belongs to the interval ΔP L < ΔP LWInterval, photovoltaic power generation unit output limit, based on the preset system frequency safety index to calculate the active power of wind turbine, and based on the calculated active power to change its comprehensive inertia control coefficient to meet the frequency modulation demand, including:

[0041] Based on the frequency safety index constraint, the active power of wind turbine is adjusted according to the disturbance to calculate the active power P W :

[0042]

[0043] Where, Δf max Take the maximum deviation limit value of frequency-0.5Hz; f0 represents the standard frequency of power grid, which takes the value of 50Hz;

[0044] According to the index H, the coefficient K c1 is designed, so that the virtual inertia coefficient k' H =K c1 k H Decreases with the decrease of the absolute value of frequency change rate, until the frequency change rate is 0, the virtual inertia coefficient is equal to 0, and the frequency modulation is exited;

[0045]

[0046] Where, H represents the ratio of the frequency change rate at the initial time before the wind turbine participates in frequency modulation and the real-time frequency change rate after participating in frequency modulation, the minimum value H min Take 1-2, the smaller value H0 takes 5-8, and the smaller value H low Take 10-20; n represents the adaptive factor of the function curve, and the value range is 10-20;

[0047] When the speed of wind turbine reaches the minimum point, the normal operating state of tracking maximum power is restored;

[0048]

[0049] Where, ω r Represents the speed of wind turbine t off Represents the time when the wind turbine exits frequency modulation; P ref (t off ) represents the active instruction value at the time when the wind turbine starts to exit frequency modulation; Δt represents the duration time of the wind turbine exiting frequency modulation; P MPPT Represents the power value of the wind turbine operating in the maximum power point tracking; P ref Represents the active power reference value of the wind turbine.

[0050] Optionally, if the disturbance value ΔP L Belongs to ΔP L > ΔP LWThe interval, photovoltaic power generation unit and fan unit all output as much as possible, under the premise of ensuring the state of charge in the normal range of 0.1-0.9, the active power output of the battery energy storage unit is controlled to meet the frequency modulation demand, including:

[0051] According to the difference between the disturbance value ΔP L and the disturbance boundary ΔP LW of starting energy storage frequency modulation, the output of the battery energy storage unit is adjusted to participate in frequency modulation.

[0052]

[0053] Wherein, P En represents the rated power of the energy storage battery, which is set to 10%-20% of the rated power of the fan; K c , K d represent the charging and discharging frequency modulation demand coefficient of energy storage participating in frequency modulation; P Esd , P Esc represent the charging and discharging power of energy storage participating in frequency modulation.

[0054] When the battery energy storage unit outputs for frequency modulation, the charging and discharging frequency modulation demand coefficient K c , K d is adjusted according to the state of charge, and the active power output of the battery energy storage unit is controlled to meet the frequency modulation demand.

[0055]

[0056] Wherein, the minimum value S min of the state of charge is 0.1, the smaller value S0 is 0.15, the slightly smaller value S low is 0.25, the slightly higher value S high is 0.75, the higher value S1 is 0.85, and the highest value S max is 0.9; K max represents the maximum unit regulation power of frequency modulation, which is 1.

[0057] Optionally, it further includes:

[0058] When the system frequency returns to stability, the battery energy storage unit with the state of charge in the overcharge or overdischarge interval is recovered to the normal working interval according to the recovery demand coefficient and the recovery constraint coefficient.

[0059] When the frequency deviation exceeds ±0.002 Hz, the recovery of the state of charge of the battery energy storage unit is stopped.

[0060]

[0061] Wherein, K c1 and K d1 are the recovery demand charging coefficient and the recovery demand discharging coefficient corresponding to the state of charge of the battery energy storage unit itself.

[0062]

[0063] wherein, K c2 and K d2 are the recovery constraint coefficients in the charging and discharging processes under the premise of ensuring the stability of the power grid frequency; the minimum frequency deviation Δf min is-0.002Hz, the smaller value Δf0 is-0.0015Hz, the lower value Δf low is-0.001Hz, the higher value Δf high is 0.001Hz, the higher value Δf1 is 0.0015Hz, and the maximum value Δf max is 0.002Hz.

[0064] Optionally, the smaller value of the recovery demand coefficient and the recovery constraint coefficient is taken as the state of charge recovery coefficient K re of the battery energy storage unit.

[0065]

[0066] wherein, ΔP ES represents the active power output during the state of charge recovery of the battery energy storage unit.

[0067] In a second aspect, the present application further provides a wind-solar-storage collaborative frequency control system based on frequency index constraints, comprising a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to execute the method provided in any one of the first aspect.

[0068] The above technical scheme conceived by the present application can achieve the following beneficial effects compared with the prior art:

[0069] 1. The wind-solar-storage collaborative frequency control method based on frequency index constraints provided by the present application. Since the active response speed of photovoltaic is faster than that of the wind turbine, and the battery energy storage has a high cost, the photovoltaic unit, the wind turbine, and the energy storage unit are arranged in sequence to participate in frequency modulation, which fully utilizes the advantages of the photovoltaic system, protects the service life of the battery energy storage unit, and reduces the economic cost. Based on the frequency safety index constraint of the system, the standby power capacity of the photovoltaic and the maximum control coefficient of the wind turbine frequency modulation are combined to divide the disturbance boundary when the light, wind, and storage participate in frequency modulation in turn. Under different working conditions, not only can the active power output of the wind-solar-storage be accurately controlled to lift the frequency to a safe range, but also the frequency modulation resources of the hybrid station can be reasonably utilized.

[0070] 2、The wind light storage collaborative frequency control method based on frequency index constraint provided by the application, aiming at the problems of insufficient utilization of wind turbine rotor kinetic energy, over-response of wind turbine comprehensive inertia control coefficient and large power shortage caused by wind turbine exiting frequency modulation in the wind light storage hybrid station grid-connected system, the wind turbine rotor comprehensive inertia control coefficient which changes most with wind speed under the safe operation range is determined by determining the rotor operation range and integrating the wind turbine working operation curve power, so as to achieve the effect of fully utilizing the wind turbine rotor kinetic energy and avoiding the secondary drop of power grid frequency. At the same time, due to the higher cost and more serious life loss of energy storage, the state of charge is considered during frequency modulation for economic consideration, so as to avoid the out-of-limit of its state of charge. At the same time, the state of charge recovery control strategy is designed, so as to protect the health state of the energy storage battery in the system and pursue economy. BRIEF DESCRIPTION OF DRAWINGS

[0071] Figure 1 It is a flowchart of the wind light storage collaborative frequency control method based on frequency index constraint in an embodiment of the application.

[0072] Figure 2 It is a wind light storage hybrid station grid-connected system structure and AC power grid fault schematic diagram in an embodiment of the application.

[0073] Figure 3 It is a wind light storage hybrid station frequency support instruction generation schematic diagram in an embodiment of the application.

[0074] Fig. 4(a) is a photovoltaic frequency support control schematic diagram in an embodiment of the application.

[0075] Fig. 4(b) is a wind turbine frequency support control schematic diagram in an embodiment of the application.

[0076] Fig. 4(c) is a storage frequency support control schematic diagram in an embodiment of the application.

[0077] Figure 5 It is a simulation result schematic diagram of the strategy control and the fixed comprehensive inertia control coefficient of wind light storage, MPPT operation control frequency characteristics and new energy field station output when the system disturbance is small in an embodiment of the application, wherein (a) represents the frequency change diagram, (b) represents the photovoltaic unit active power output diagram, (c) represents the wind turbine active power output diagram, and (d) represents the storage unit active power output diagram.

[0078] Figure 6The simulation result schematic diagram of frequency characteristics and new energy field station output of the strategy control and wind, light and storage adopting fixed comprehensive inertia control coefficient and MPPT operation control when the system disturbance is large in an embodiment of the present application, wherein (a) represents a frequency change diagram, (b) represents a photovoltaic unit active power diagram, (c) represents a wind turbine active power diagram, (d) represents a storage unit active power diagram, and (e) represents a wind turbine rotor speed change diagram.

[0079] Figure 7 The simulation result schematic diagram of frequency characteristics and new energy field station output of the strategy control and wind, light and storage adopting fixed comprehensive inertia control coefficient and MPPT operation control when the system disturbance is large in an embodiment of the present application, wherein (a) represents a frequency change diagram, (b) represents a photovoltaic unit active power diagram, (c) represents a wind turbine active power diagram, (d) represents a storage unit active power diagram, and (e) represents a wind turbine rotor speed change diagram.

[0080] In the above figures, the same characters represent the same meaning, and the figure mark is explained as follows:

[0081] G represents four synchronous generators, L1 represents load 1, L2 represents load 2, 1-13 represents system network nodes 1-13, the wind, light and storage hybrid station is aggregated to node 8 and connected to the power grid; Δf B represents the frequency deviation boundary value of starting the storage state of charge self-recovery stage. DETAILED DESCRIPTION

[0082] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the figures and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0083] The content involved in the above embodiments is described below in combination with a preferred embodiment.

[0084] Embodiment one

[0085] As Figure 1As shown, the application provides a wind-solar-storage collaborative frequency control method based on frequency index constraints, applied to a wind-solar-storage hybrid station grid-connected system, the wind-solar-storage hybrid station grid-connected system comprising a wind turbine, a battery energy storage unit, an alternating current power grid and a plurality of parallel photovoltaic power generation units; the photovoltaic power generation units, the wind turbine and the battery energy storage unit are respectively connected to the same alternating current bus through the connection of their respective converters and transformers, and are integrated into the alternating current power grid, the wind-solar-storage collaborative frequency control method based on frequency index constraints comprising:

[0086] S1, the photovoltaic power generation unit is controlled to reserve standby power, and the maximum comprehensive inertia control coefficient of the wind turbine is set according to the wind speed of the wind turbine;

[0087] S2, the preset system frequency safety index is taken as the first constraint, the disturbance boundary ΔP LG for starting the frequency regulation of the photovoltaic power generation unit and the disturbance boundary ΔP LPV for starting the frequency regulation of the wind turbine are calculated respectively; the maximum comprehensive inertia control coefficient of the wind turbine is taken as the second constraint, and based on the first constraint and the second constraint, the disturbance boundary ΔP LW for starting the frequency regulation of the battery energy storage unit is calculated;

[0088] S3, the frequency change rate of the wind-solar-storage hybrid station grid-connected system is monitored to obtain the disturbance value ΔP L suffered by the system, and according to the comparison result of the disturbance value ΔP L and each disturbance boundary, the corresponding frequency regulation strategy is executed:

[0089] S4, if the disturbance value ΔP L belongs to the interval ΔP LG <ΔP L ≤ΔP LPV , the photovoltaic power generation unit is controlled to generate power to meet the frequency regulation demand based on the preset system frequency safety index;

[0090] S5, if the disturbance value ΔP L belongs to the interval ΔP LPV <ΔP L ≤ΔP LW , the photovoltaic power generation unit is controlled to generate power to meet the frequency regulation demand based on the preset system frequency safety index, and the comprehensive inertia control coefficient of the wind turbine is changed based on the calculated active power to meet the frequency regulation demand;

[0091] S6, if the disturbance value ΔP L belongs to the interval ΔP L >ΔP LW , the photovoltaic power generation unit and the wind turbine are controlled to generate power to meet the frequency regulation demand according to the state of charge control of the battery energy storage unit.

[0092] As Figure 2 shown, the photovoltaic power generation unit is connected in sequence with a photovoltaic power generation array, a DC / DC boost circuit and an inverter; the wind turbine generator is a plurality of double-fed wind turbine generators, and the wind turbine generator is connected in sequence with a double-fed induction motor, a rotor-side converter and a stator-side converter; the battery energy storage unit is connected in sequence with a battery equivalent circuit and an inverter; the load disturbance occurs at node 7; and the wind-solar-storage hybrid station is connected to the power grid through node 8. The wind-solar-storage hybrid station frequency support instruction generation is as shown in Figure 3 shown, the disturbance boundary value of the photovoltaic power generation unit and the wind turbine generator participating in frequency modulation is calculated according to the preset system frequency safety index constraint, the disturbance boundary value of the battery energy storage unit participating in frequency modulation is calculated according to the preset system frequency safety index constraint and the maximum comprehensive inertia control coefficient of the wind turbine generator; the disturbance value obtained by monitoring the frequency change rate of the wind-solar-storage hybrid station grid-connected system is compared with the calculated disturbance boundary value to generate a frequency modulation instruction, and the active power output of the wind-solar-storage is controlled; the wind-solar-storage frequency support control schematic diagram is shown in FIG. 4(a), FIG. 4(b) and FIG. 4(c), FIG. 4(a) represents that the disturbance value ΔP L belongs to the interval ΔP LG <ΔP L ≤ΔP LPV , the photovoltaic power generation unit increased power is calculated based on the preset system frequency safety index, and the DC capacitor side voltage U PV of the photovoltaic power generation unit is adjusted; FIG. 4(b) represents that the disturbance value ΔP L belongs to the interval ΔP LPV <ΔP L ≤ΔP LW , the wind turbine adopts comprehensive inertia control to participate in frequency modulation, and the speed recovery process is started when the speed reaches the lowest point or exceeds 0.7p.u.; FIG. 4(c) represents that the disturbance value ΔP L belongs to the interval ΔP L >ΔP LW , the battery energy storage unit frequency modulation charge and discharge active power is controlled to meet the frequency modulation demand on the premise that the state of charge is ensured to be in the normal range of 0.1-0.9, and the state of charge recovery process of the battery energy storage unit is considered in terms of the state of charge and the frequency deviation after the frequency is stabilized.

[0093] The disturbance boundary values of the wind-solar-storage participating in frequency modulation in sequence are obtained based on the frequency safety index constraint and the standby power capacity of the photovoltaic and the maximum frequency modulation control coefficient of the wind turbine. When a frequency event occurs in the system, the disturbance value of the system is obtained according to the frequency change rate measured at the initial time of the disturbance, compared with the disturbance boundary value to determine the interval it belongs to and generate the corresponding frequency modulation instruction. If the disturbance is small, the synchronous machine frequency modulation can meet the frequency modulation demand, otherwise the active power output of the wind-solar-storage is controlled according to the disturbance size.

[0094] Optionally, the S1 comprises:

[0095] S101, setting an initial load shedding rate σ0 of the photovoltaic power generation unit, and using the standby power corresponding to the initial load shedding rate σ0 for the perturbation and frequency modulation control; the standby power ΔP PV = (1- σ0) P MPPT ;

[0096] Wherein, P MPPT represents the power value of the photovoltaic power generation unit operating at the maximum power point, and the initial load shedding rate is in the range of 5% to 22%; in the embodiment, the initial load shedding rate σ0 is preferably 20%.

[0097] S102, obtaining a speed extreme value of the wind turbine and a wind turbine incremental power limit ΔP wmax , obtaining a speed change amount according to the speed extreme value and the wind turbine incremental power limit respectively, and determining a maximum speed change amount Δω of the wind turbine from the two speed changes; the calculation formula of the maximum speed change amount Δω is:

[0098]

[0099] Wherein, ω r0 is an initial speed of the wind turbine, ω rmax and ω rmin are the maximum and minimum safe operating speeds respectively, ω0 is the cut-in speed of the wind turbine entering the maximum power tracking area, P n represents the rated power of the wind turbine, k opt represents the maximum power tracking control coefficient, H w represents the inertia coefficient of the wind turbine, and t h is the frequency modulation duration of the wind turbine. In the embodiment, ω rmax and ω rmin are 1.2 times and 0.7 times of the rated speed respectively, and t h is 3s.

[0100] When the disturbance occurs, the wind turbine participates in frequency modulation by changing the speed to utilize the rotor kinetic energy, and the maximum speed change amount needs to be calculated. When no disturbance occurs, the wind turbine maintains normal operation of the speed. When the frequency drops, the wind turbine provides inertia to suppress the frequency change by releasing the rotor kinetic energy. In another embodiment, in the condition of negative frequency rise, the wind turbine suppresses the frequency fluctuation by absorbing the rotor kinetic energy. The amount of rotor kinetic energy is reflected by the change range of the rotor speed. The change range of the rotor speed is constrained by the speed extreme value and the wind turbine incremental power limit respectively.

[0101] S103, setting a maximum comprehensive inertia control coefficient of the wind turbine according to the maximum speed change amount Δω;

[0102]

[0103]

[0104] wherein, k D is a droop coefficient, k H is a virtual inertia coefficient; ROCOF and Δf max are the maximum frequency rate of change and the maximum frequency drop amplitude corresponding to the system disturbance value ΔP LPV ; k opt represents the maximum power tracking coefficient of the wind turbine; P ref , P m (v, ω rmin ) represent the active power instruction value of the wind turbine at the initial rotational speed ω r0 and the minimum rotational speed ω rmin ; P MPPT (v, ω r0 ), P MPPT (v, ω rmin ) represent the power value of the maximum power operating point of the wind turbine at the initial rotational speed and the minimum rotational speed; t n represents the time when the frequency reaches the extreme point; ΔE k represents the change amount of the kinetic energy of the rotor of the wind turbine; P m (v, ω r ) represents the mechanical power of the wind turbine.

[0105] wherein, the wind turbine participates in frequency modulation through comprehensive inertia control, wherein the comprehensive inertia control represents the combination of virtual inertia control and droop control.

[0106] Optionally, the S2 specifically comprises:

[0107] S201, obtain the equivalent inertia coefficient and the damping coefficient of the wind-solar-storage hybrid station grid-connected system, and determine a preset system frequency safety index; based on the preset system frequency safety index, calculate the disturbance value corresponding to each safety index by using the SFR model theoretical formula, and take the minimum value as the disturbance boundary ΔP LG for starting photovoltaic frequency modulation; wherein, the preset system frequency safety index comprises: the frequency rate of change is not more than -0.5 Hz / s, the maximum frequency deviation is not more than -0.5 Hz, and the steady-state frequency deviation is not more than -0.2 Hz;

[0108]

[0109] wherein, R represents the droop coefficient of the governor, H eq represents the equivalent inertia coefficient of the system, D eq represents the equivalent damping coefficient of the system, take the limit value -0.5 Hz / s, Δf maxThe limit value-0.5Hz, Δf ss The limit value-0.2Hz, ΔP L1 , ΔP L2 , ΔP L3 respectively represent the disturbance boundary when the limit value of the initial rate of frequency change, the maximum deviation of frequency and the steady-state deviation of frequency is taken, t n represents the time when the frequency reaches the extreme point, ξ represents the damping ratio, ω n represents the natural oscillation angular velocity, ω d represents the damping angular velocity, F H represents the proportion of work done by the high-pressure cylinder of the prime mover, T R represents the reheating time constant;

[0110] S202, the disturbance boundary value ΔP when the photovoltaic power generation unit reaches the limit output is calculated by using the theoretical formula of the SFR model LPV ;

[0111]

[0112] S203, according to the maximum comprehensive inertia control coefficient of the wind turbine, the disturbance boundary value ΔP when the wind turbine reaches the limit utilization of rotor kinetic energy is calculated by using the theoretical formula of the SFR model LW ;

[0113] wherein

[0114]

[0115] wherein, H' eq represents the equivalent inertia coefficient of the system after adding the comprehensive inertia control of the wind turbine; D' eq represents the equivalent damping coefficient of the system after adding the comprehensive inertia control of the wind turbine; t' n represents the time when the frequency reaches the extreme value after adding the wind turbine; H G represents the inertia constant of the synchronous machine; S sys represents the total capacity of the system; S w represents the capacity of the wind turbine; S G represents the capacity of the synchronous machine.

[0116] Optionally, the calculation formula of the disturbance value ΔP L is as follows:

[0117]

[0118] wherein, H eq is the inertia constant of the wind-solar-storage hybrid station grid-connected system, and f represents the grid frequency.

[0119] Optionally, S4 specifically comprises:

[0120] S401, calculate the increased power P of the standby power of the photovoltaic power generation unit based on the preset system frequency safety index PV :

[0121]

[0122] wherein, Take the limit value-0.5Hz / s, Δf max Take the limit value-0.5Hz, Δf ss Take the limit value-0.2Hz.

[0123] S402, according to the calculated increased power P of the standby power PV The DC capacitor side voltage U of the photovoltaic power generation unit PV Adjust to meet the frequency modulation requirement: the frequency change rate is not more than-0.5Hz / s, the maximum frequency deviation is not more than-0.5Hz, and the steady-state frequency deviation is not more than-0.2Hz.

[0124] Optionally, the S5 specifically comprises:

[0125] S501, based on the frequency safety index constraint, calculate the active power P of the wind turbine according to the disturbance adjustment of the active power of the wind turbine W :

[0126]

[0127] wherein, Δf max Take the maximum frequency deviation limit value-0.5Hz; f0 represents the grid standard frequency, which takes the value of 50Hz.

[0128] Based on the frequency safety index constraint, the power size of the wind turbine is adjusted according to the disturbance; since the frequency deviation is more sensitive to k D , keep the droop coefficient unchanged and change the virtual inertia control coefficient k H of the wind turbine with the disturbance size, generate the active power P of the wind turbine W .

[0129] S502, design the coefficient K according to the index H c1 , so that the virtual inertia coefficient k' H =K c1 k H Gradually exit frequency modulation as the frequency change rate decreases;

[0130]

[0131] wherein, H represents the ratio of the frequency change rate at the initial time before the wind turbine participates in frequency modulation to the real-time frequency change rate after participating in frequency modulation, and the minimum value H minH0=5~8, H=6, H low H=10~20; n=10~20.

[0132] Since the frequency starts to recover at the minimum point, the frequency rate of change changes sign, and the virtual inertia control is equivalent to absorbing power from the system, so the design coefficient K c1 , so that the virtual inertia coefficient k' H =K c1 k H Gradually exit the frequency modulation as the frequency rate of change decreases. In this embodiment, the minimum value H min H0=6, H=6, H low H=10, n=15, coefficient K c1 The speed of the index H changes appropriately, which can take into account the effect of improving the frequency before the virtual inertia control exits the frequency modulation.

[0133] Optionally, after S5, it further includes:

[0134] When the wind turbine speed reaches the minimum point, the normal operating state of tracking the maximum power is restored;

[0135]

[0136] ω r represents the speed of the wind turbine; t off represents the time when the wind turbine exits the frequency modulation; P ref (t off ) represents the active command value at the time when the wind turbine starts to exit the frequency modulation; Δt represents the duration of the wind turbine exiting the frequency modulation; P MPPT represents the power value when the wind turbine operates at the maximum power point tracking; P ref represents the active power reference value of the wind turbine.

[0137] After the speed reaches the minimum point, the speed starts to recover; in order to not produce a large power shortage, the active increment is smoothly attenuated to zero. Specifically, if the speed drops to 0.7p.u. Immediately restore the MPPT operating state.

[0138] Optionally, S6 specifically includes:

[0139] S601, according to the disturbance value ΔP L The difference between the disturbance boundary ΔP LW of starting the energy storage frequency modulation, the battery energy storage unit output is adjusted to participate in the frequency modulation;

[0140]

[0141] P Enrepresents the rated power of the energy storage battery, which is set to 10% to 20% of the rated power of the fan; K c represents the rated power of the energy storage battery, which is set to 10% to 20% of the rated power of the fan; K d represents the charging and discharging frequency modulation demand coefficient of the energy storage participating in frequency modulation; P Esd represents the charging and discharging frequency modulation demand coefficient of the energy storage participating in frequency modulation; P Esc represents the charging and discharging power of the energy storage participating in frequency modulation. In the embodiment, P En is 10%.

[0142] Further, in another embodiment, the disturbance is a negative frequency rise condition, and the energy storage suppresses frequency fluctuation by absorbing power from the system to charge.

[0143] S602, when the battery energy storage unit is in frequency modulation output, the charging and discharging frequency modulation demand coefficient K c represents the charging and discharging frequency modulation demand coefficient of the energy storage participating in frequency modulation; P d is adjusted according to the state of charge, and the active power of the battery energy storage unit is controlled to meet the frequency modulation demand;

[0144]

[0145] wherein the minimum value S min is 0.1, the smaller value S0 is 0.15, the lower value S low is 0.25, the higher value S high is 0.75, the higher value S1 is 0.85, and the maximum value S max is 0.9; K max represents the maximum unit regulation power of frequency modulation, and the value is 1.

[0146] The output of the energy storage considers the state of charge of the battery, specifically, the frequency modulation demand coefficient is adjusted according to the SOC, and the battery energy storage unit cannot participate in frequency modulation when the state of charge is too small, and the energy storage is not allowed to charge frequency modulation when the state of charge is too large. In the embodiment, the disturbance is a frequency rise condition. Further, in another embodiment, the disturbance is a negative frequency rise condition.

[0147] Optionally, after S6, it further includes:

[0148] When the system frequency returns to stable, the battery energy storage unit with the state of charge in the overcharged or overdischarged region is restored to the normal working interval according to the recovery demand coefficient and the recovery constraint coefficient;

[0149] When the frequency deviation exceeds ±0.002 Hz, the restoration of the state of charge of the battery energy storage unit is stopped;

[0150]

[0151] wherein K c1 and K d1 are the recovery demand charging coefficient and the recovery demand discharging coefficient corresponding to the state of charge of the battery energy storage unit itself;

[0152] When the frequency deviation exceeds ±0.002Hz, the recovery of the state of charge of the battery energy storage unit is stopped;

[0153]

[0154] wherein K c2 and K d2 are the recovery constraint coefficients in the charging and discharging processes under the premise of ensuring the stability of the grid frequency; the minimum frequency deviation Δf min is -0.002Hz, the smaller value Δf0 is -0.0015Hz, the lower value Δf low is -0.001Hz, the higher value Δf high is 0.001Hz, the larger value Δf1 is 0.0015Hz, and the maximum value Δf max is 0.002Hz.

[0155] In this embodiment, the disturbance is a positive frequency drop, and when the frequency is recovered to be stable, the SOC state of the energy storage battery in the over-discharge region needs to be recovered to the normal working region. Further, in another embodiment, the disturbance is a negative frequency rise, and the SOC state of the energy storage battery after over-response is recovered to the normal state.

[0156] Optionally, in S6, the smaller value of the recovery demand coefficient and the recovery constraint coefficient is taken as the state of charge recovery coefficient K re of the battery energy storage unit.

[0157]

[0158] wherein ΔP ES represents the active power when the state of charge of the battery energy storage unit is recovered.

[0159] To verify the effectiveness of the method provided by the present application, a four-region two-machine system of a wind-solar-storage hybrid station as shown in FIG. 1 is built on a Matlab / Simulink platform, and the main parameters are shown in Table 1. Figure 2

[0160] Table 1 Main parameters of the four-region two-machine system of the wind-solar-storage hybrid station

[0161] System parameters Numerical values Total capacity of photovoltaic power station (MVA) 100 Total capacity of wind turbine generator (MVA) 100 Rated power of energy storage (MW) 10 Capacity of each thermal power generator (MVA) 100 Rated frequency of system (Hz) 50 Load L1, L2 (MW) 967、1767 Inertia constant of synchronous machine G (s) 117、117、111.15、111.15 System damping constant D 0 Regulation coefficient of synchronous machine R 1 / 225 Initial load shedding rate of photovoltaic power 20％ SOC of energy storage 0.6 Wind speed (m / s) 11.358 Wind turbine rotor speed limit ω rmax , ω rmin (p.u.) 1.2、0.7 Wind turbine generator frequency modulation duration t h (s)] 3 minimum value H min , smaller value H0, too small value H low ]]> 2、6、10

[0162] Simulation setting 1: the rated operation wind-solar-storage hybrid station grid-connected system is disturbed by 4p.u. at the time of 5s. At this time, the disturbance boundary values calculated according to the SFR theoretical formula are ΔP LG = 3.7pu; ΔP LPV = 4.3pu; ΔP LW ​=4.6 pu; this indicates that photovoltaic power is involved in frequency regulation. Simulation results of frequency characteristics and power output of renewable energy plants under different control conditions are as follows: Figure 5 As shown.

[0163] according to Figure 5 Simulation results show that when wind, solar, and energy storage are operating at their maximum power operating point, such as Figure 5 The maximum frequency drop shown in (a) is -0.52Hz, which does not meet the frequency index requirements and poses a risk of instability, thus requiring frequency regulation by renewable energy sources. This method generates a frequency regulation command immediately after the frequency drop occurs, allowing the photovoltaic system to provide frequency support. Based on the frequency index constraints, the photovoltaic system outputs backup power by changing the capacitor-side voltage, such as... Figure 5 In (b), the photovoltaic active power undergoes a step change in response frequency after 0.2s, demonstrating a fast response speed. Furthermore, compared to the fixed integrated inertia control coefficient method used in wind, solar, and energy storage, this method results in higher photovoltaic output, fully utilizing solar energy resources for frequency regulation and ensuring effective frequency regulation. According to... Figure 5 As shown in (b), for traditional integrated inertial control methods, the reserve power of photovoltaic power still has a large margin that can be used for frequency regulation, but if... Figure 5 (c) and Figure 5 As shown in (d), the photovoltaic resources were not fully utilized before the wind turbines and energy storage were started for frequency regulation together. Although the traditional integrated inertial control frequency improvement effect is slightly better, with the lowest frequency point slightly higher by 0.1Hz, it results in resource waste and reduces economic efficiency. Especially for high-cost energy storage resources, energy storage does not need to participate in frequency regulation when the disturbance is small, thus reducing the number of charge and discharge cycles of energy storage.

[0164] Simulation Setting 2: A grid fault occurs in the rated-operation photovoltaic grid-connected system at 5 seconds, with a grid disturbance of 4.45 pu. It can be determined that frequency regulation with only photovoltaic participation is insufficient; wind turbine participation is also required. Simulation results of frequency characteristics and power output of renewable energy plants under different control conditions are as follows: Figure 6 As shown;

[0165] according to Figure 6 Simulation results show that if the wind, solar, and energy storage systems operate at maximum power, the maximum frequency drop is -0.59Hz, indicating large frequency fluctuations that do not meet frequency performance requirements and pose a risk of instability. In this case, if... Figure 6 In method (b), the photovoltaic system returns all its reserve power to the MPPT operating state to maximize output and fully utilize solar energy resources; while the wind turbine adaptively adjusts its virtual inertia coefficient to release rotor kinetic energy based on disturbances. Figure 6The frequency maximum change rate is-0.3287 Hz / s and-0.3097 Hz / s, the frequency minimum points are 49.48 Hz and 49.51 Hz, and the frequency steady-state deviations are-0.21 Hz and-0.19 Hz, respectively. It can be seen that the frequency demand is met under the present strategy, while the frequency minimum point and the steady-state deviation do not meet the constraint index conditions under the traditional comprehensive inertia control. According to Figure 6 (b) and Figure 6 (c) shown, the photovoltaic under the present method increases all standby power, and the wind turbine also outputs to meet the frequency demand according to the disturbance size; while for the wind-solar-storage using the fixed comprehensive inertia control coefficient frequency modulation method, since the control coefficient is fixed and cannot be adjusted according to the size of the disturbance, the active power output of the photovoltaic and the wind turbine is not sufficient, resulting in the inability to meet the frequency demand. Moreover Figure 6 (d) and Figure 6 (e) shown, under the method of fixed control coefficient, not only the storage output is 0.5 p.u., but also the wind turbine speed drops more, indicating that the wind turbine releases more rotor kinetic energy than the present strategy, causing resource waste. The present strategy takes into account the frequency modulation effect and the rational use of resources.

[0166] Simulation setting 3: the photovoltaic grid-connected system under rated operation has a serious fault in the power grid at 5s, and the power grid disturbance is 4.65 p.u. It can be judged that at this time the photovoltaic and the wind turbine cannot meet the requirements of participating in frequency modulation, and the storage needs to participate in the expansion of the stability domain. The frequency characteristics and the active power output of the new energy station under different controls are shown in Figure 7 .

[0167] According to Figure 7 the simulation results, if the wind-solar-storage operates under the maximum power point control, the maximum frequency drop is-0.61 Hz, the frequency fluctuation is large, and the frequency index conditions are not met, and there is a risk of instability. At this time, as shown in Figure 7 (c) and Figure 7 (d) in the present method, the photovoltaic and the wind turbine participate in frequency modulation to the limit, and the storage adjusts the output to expand the stability domain according to the disturbance size and the state of charge. As shown in Figure 7 (a) shown, the frequency maximum change rate is-0.3287 Hz / s and-0.3097 Hz / s, the frequency minimum points are 49.48 Hz and 49.51 Hz, and the frequency steady-state deviations are-0.21 Hz and-0.19 Hz, respectively. It can be seen that the frequency demand is met under the present strategy, while the frequency minimum point and the steady-state deviation do not meet the constraint index conditions under the traditional comprehensive inertia control. According to Figure 7(b) and Figure 7 The active power of photovoltaic and wind turbine in (c) is not sufficient to meet the frequency modulation requirement. Under the strategy, the wind turbine rotor speed in (e) drops to the minimum speed limit 0.7 p.u., and the rotor kinetic energy is fully released to the limit utilization. As shown in (f), the output of the fixed comprehensive inertia control is 0.05 p.u. more than that of the strategy, and the SOC drops faster. The output does not consider the influence of state of charge, which is not conducive to the service life of the energy storage. Figure 7 The active power of photovoltaic and wind turbine in (c) is not sufficient to meet the frequency modulation requirement. Under the strategy, the wind turbine rotor speed in (e) drops to the minimum speed limit 0.7 p.u., and the rotor kinetic energy is fully released to the limit utilization. As shown in (f), the output of the fixed comprehensive inertia control is 0.05 p.u. more than that of the strategy, and the SOC drops faster. The output does not consider the influence of state of charge, which is not conducive to the service life of the energy storage. ​ The active power of photovoltaic and wind turbine in (c) is not sufficient to meet the frequency modulation requirement. Under the strategy, the wind turbine rotor speed in (e) drops to the minimum speed limit 0.7 p.u., and the rotor kinetic energy is fully released to the limit utilization. As shown in (f), the output of the fixed comprehensive inertia control is 0.05 p.u. more than that of the strategy, and the SOC drops faster. The output does not consider the influence of state of charge, which is not conducive to the service life of the energy storage. ​ The active power of photovoltaic and wind turbine in (c) is not sufficient to meet the frequency modulation requirement. Under the strategy, the wind turbine rotor speed in (e) drops to the minimum speed limit 0.7 p.u., and the rotor kinetic energy is fully released to the limit utilization. As shown in (f), the output of the fixed comprehensive inertia control is 0.05 p.u. more than that of the strategy, and the SOC drops faster. The output does not consider the influence of state of charge, which is not conducive to the service life of the energy storage.

[0168] The embodiment of the present application divides the disturbance boundary of photovoltaic, wind and energy storage participating in frequency modulation in turn based on the frequency safety index constraint of the system, designs the corresponding control strategy for different disturbance intervals, accurately controls the active power of wind, light and storage in the hybrid power station according to the demand of the frequency safety index, and more reliably meets the frequency modulation requirement. The photovoltaic power generation unit has the characteristics of rapid adjustment, controls the photovoltaic to modulate frequency when the disturbance is small, can quickly respond to frequency, and ensures the frequency modulation effect. With the increase of disturbance, the wind turbine and battery energy storage unit are called in turn to participate in frequency modulation. The technical problems of lacking basis for controller parameter setting, not fully developing the frequency modulation advantages of various new energies and over-reliance on energy storage response in new energy collaborative control are solved, and the economic benefits of reasonable utilization of wind, light and storage are realized under the premise of meeting the frequency modulation requirement.

[0169] Embodiment two

[0170] The present application also provides a wind, light and storage collaborative frequency control system based on frequency index constraint, comprising a memory and a processor, the memory stores a computer program, and the processor executes the computer program to execute the method provided in any one of the embodiments.

[0171] Those skilled in the art will readily understand that the above description is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A wind-solar-storage coordinated frequency control method based on frequency index constraints, applied to a wind-solar-storage hybrid grid-connected system, wherein the wind-solar-storage hybrid grid-connected system includes wind turbine generators, battery energy storage units, an AC power grid, and multiple parallel photovoltaic power generation units; the photovoltaic power generation units, wind turbine generators, and battery energy storage units are respectively connected to the same AC bus and integrated into the AC power grid through their respective converters and transformers, characterized in that, The wind-solar-storage coordinated frequency control method based on frequency index constraints includes: The photovoltaic power generation unit is subjected to load reduction control to reserve backup power, and the maximum comprehensive inertia control coefficient of the wind turbine is adjusted according to the wind speed at which the wind turbine is located. Using the preset system frequency security index as the first constraint, the disturbance boundary for initiating frequency regulation of the photovoltaic power generation unit is calculated respectively. Disturbance boundary of starting wind turbine frequency regulation Using the maximum integrated inertia control coefficient of the wind turbine as the second constraint, and based on the first and second constraints, calculate the disturbance boundary for starting the frequency regulation of the battery energy storage unit. ; Monitor the frequency variation rate of the wind-solar-storage hybrid grid-connected system to obtain the disturbance value experienced by the system. And based on the disturbance value Based on the comparison results with each disturbance boundary, implement the corresponding frequency modulation strategy: If the disturbance value belong In the specified range, the additional power of the photovoltaic power generation unit is calculated based on the preset system frequency security index to meet the frequency regulation requirements; If the disturbance value belong Within the specified range, the photovoltaic power generation unit outputs at its maximum capacity. Based on the preset system frequency safety index, the active power of the wind turbine is calculated, and the comprehensive inertial control coefficient is adjusted based on the calculated active power to meet the frequency regulation requirements. If the disturbance value belong During the interval, both the photovoltaic power generation unit and the wind turbine unit are operating at their maximum capacity, and the active power output of the battery energy storage unit is controlled according to the state of charge to meet the frequency regulation requirements. The step of controlling the photovoltaic power generation unit to reserve backup power and adjusting the maximum comprehensive inertia control coefficient of the wind turbine according to the wind speed at which the wind turbine is located includes: Set the initial load shedding rate of the photovoltaic power generation unit. The initial load reduction rate The corresponding reserve power is used for disturbance frequency modulation control; the reserve power ; in, This indicates the power value of the photovoltaic power generation unit operating at its maximum power point. The value range is 5% to 22%; Obtain the extreme speed values ​​and the power increase limit of the wind turbine generator set. Based on these values, calculate the speed change. Then, determine the maximum speed change of the wind turbine generator set from these speed changes. The maximum change in rotational speed The calculation formula is: in, It is the initial speed of the wind turbine. and These are the specified maximum and minimum operating speeds for safe operation. This indicates the rated power of the fan. This represents the maximum power point tracking control coefficient. This represents the fan's moment of inertia coefficient. This refers to the duration of the fan frequency regulation; Based on the maximum change in rotational speed Set the maximum integrated inertia control coefficient of the wind turbine unit; in, The droop coefficient is... This is the virtual inertia coefficient; and The system disturbance value is The corresponding maximum rate of frequency change and maximum frequency drop amplitude; This represents the maximum power tracking coefficient of the wind turbine; Indicates the initial rotational speed and minimum speed The active power command value of the wind turbine at any given time; This represents the power value at the maximum power operating point of the wind turbine at the initial speed and the lowest speed. This indicates the time it takes for the frequency to reach its extreme value. This represents the change in the kinetic energy of the fan rotor; This indicates the mechanical power of the fan.

2. The method as described in claim 1, characterized in that, The preset system frequency security index is used as the first constraint to calculate the disturbance boundary for initiating frequency regulation of the photovoltaic power generation unit. Disturbance boundary of starting wind turbine frequency regulation ; Using the maximum integrated inertia control coefficient of the wind turbine as the second constraint, and based on the first and second constraints, the disturbance boundary for starting the frequency regulation of the battery energy storage unit is calculated. ,include: The equivalent inertia coefficient and damping coefficient of the wind-solar-storage hybrid grid-connected system are obtained, and a preset system frequency safety index is determined. Based on the preset system frequency safety index, the disturbance value corresponding to each safety index is calculated using the SFR model theoretical formula, and the minimum value is taken as the disturbance boundary for initiating photovoltaic frequency regulation. The preset system frequency safety indicators include: frequency change rate not exceeding -0.5 Hz / s, maximum frequency deviation not exceeding -0.5 Hz, and steady-state frequency deviation not exceeding -0.2 Hz. in, This indicates the governor setting droop coefficient. This represents the system's equivalent inertia coefficient. This represents the system's equivalent damping coefficient. Take a limit of -0.5 Hz / s. Take the limit value of -0.5 Hz. Take a limit of -0.2 Hz. These represent the disturbance boundaries when the initial rate of change of frequency, the maximum frequency deviation, and the steady-state frequency deviation reach their limits, respectively. Indicates the damping ratio. Indicates the natural oscillating angular velocity. Indicates the damped angular velocity. F H This indicates the work ratio of the high-pressure cylinder of the prime mover. T R Indicates the reheat time constant; The disturbance boundary value of the photovoltaic power generation unit at its limit output is calculated using the SFR model theoretical formula. ; Based on the set maximum integrated inertia control coefficient of the wind turbine, the disturbance boundary value when the wind turbine fully utilizes the rotor kinetic energy is calculated using the SFR model theoretical formula. ; in, This represents the equivalent inertia coefficient of the system after incorporating integrated inertial control of the wind turbine; This represents the system's equivalent damping coefficient after incorporating integrated inertial control of the wind turbine. This indicates the time of frequency extrema after the addition of the fan; This represents the inertia constant of the synchronous machine; Indicates the total system capacity; Indicates the capacity of the wind turbine unit; This indicates the capacity of the synchronous machine.

3. The method as described in claim 1, characterized in that, The disturbance value The calculation formula is: in, The inertia constant of the wind-solar-storage hybrid grid-connected system. Indicates the power grid frequency.

4. The method as described in claim 1, characterized in that, The perturbation value belong Within a given range, the increased power output of the photovoltaic power generation unit is calculated based on preset system frequency security indicators to meet frequency regulation requirements, including: The additional power generation of the photovoltaic power generation unit's backup power is calculated based on the preset system frequency security index. : in, Take a limit of -0.5 Hz / s. Take the limit value of -0.5 Hz. Set the limit to -0.2 Hz; Increased power generation based on calculated reserve power DC capacitor side voltage of photovoltaic power generation unit Adjustments were made to meet the frequency modulation requirements.

5. The method as described in claim 2, characterized in that, The perturbation value belong Within a given range, the photovoltaic power generation unit operates at its maximum output. Based on a preset system frequency safety index, the active power of the wind turbine is calculated, and the comprehensive inertia control coefficient is adjusted based on the calculated active power to meet frequency regulation requirements, including: Based on frequency security constraints, the active power of the wind turbine is calculated according to the disturbance adjustment of the active power of the wind turbine. : in, The maximum frequency deviation limit is set to -0.5 Hz; This represents the standard frequency of the power grid, with a value of 50 Hz. According to the indicators H Design coefficient Make the virtual inertia coefficient The virtual inertia coefficient decreases as the absolute value of the frequency change rate decreases, until the frequency change rate is 0, at which point the virtual inertia coefficient equals 0 and the frequency modulation ends. in, This represents the ratio of the initial frequency change rate before the wind turbine participates in frequency regulation to the real-time frequency change rate after participating in frequency regulation, with the minimum value being [value missing]. Choose between 1 and 2, the smaller value. A value between 5 and 8 is considered a small value. Take 10~20; n This represents the adaptive factor of the function curve, with a value range of 10 to 20; When the wind turbine speed reaches its lowest point, it resumes normal operation by tracking maximum power. in, Indicates the wind turbine speed. Indicates the moment when the wind turbine unit exits frequency regulation; This indicates the active power command value at the moment when the wind turbine begins to exit frequency regulation; Indicates the duration during which the wind turbine unit is out of frequency regulation; This indicates the power value of the wind turbine when it is operating at its maximum power point. This indicates the reference value for the active power of the wind turbine.

6. The method as described in claim 5, characterized in that, The perturbation value belong During this period, both photovoltaic power generation units and wind turbine units operate at their maximum capacity. While ensuring the state of charge (SOC) remains within the normal range of 0.1 to 0.9, the active power output of the battery energy storage unit is controlled to meet frequency regulation requirements, including: According to the disturbance value Disturbance boundary with the start of energy storage frequency regulation The difference is used to adjust the output of the battery energy storage unit to participate in frequency regulation; in, This indicates the rated power of the energy storage battery, set to 10%~20% of the rated power of the wind turbine; This represents the charging and discharging frequency regulation demand coefficients for energy storage participating in frequency regulation. This indicates the power of energy storage participating in frequency regulation charging and discharging; When the battery energy storage unit is operating at regulated frequency, it adjusts the charging and discharging frequency regulation demand coefficient according to the state of charge. , The active power output of the battery energy storage unit is controlled to meet the frequency regulation requirements. Among them, the minimum state of charge Take 0.1, the smaller value Taking 0.15 is a small value. A value of 0.25 is too high. Take 0.75, a relatively high value. Take 0.85, the highest value Take 0.9; This represents the maximum unit adjustment power of frequency modulation, with a value of 1.

7. The method as described in claim 6, characterized in that, Also includes: Once the system frequency stabilizes, the battery energy storage units that were in the overcharge or over-discharge zone will be restored to the normal operating range based on the recovery demand coefficient and the recovery constraint coefficient. When the frequency deviation exceeds ±0.002 Hz, the recovery of the state of charge of the battery energy storage unit is stopped; in, and These are the charging coefficient and discharging coefficient for recovery demand corresponding to the state of charge of the battery energy storage unit itself. in, and It is the recovery constraint coefficient during charging and discharging processes, under the premise of ensuring grid frequency stability; the minimum frequency deviation. Take -0.002 Hz, the smaller value. Taking -0.0015 Hz is too small. A value of -0.001 Hz is considered too high. Take 0.001 Hz, a relatively high value. Take 0.0015 Hz, the highest value. Take 0.002 Hz.

8. The method as described in claim 7, characterized in that, The smaller of the recovery demand coefficient and the recovery constraint coefficient is taken as the state-of-charge recovery coefficient of the battery energy storage unit. : in, This indicates the active power output of the battery energy storage unit when its state of charge is restored.

9. A wind-solar-storage coordinated frequency control system based on frequency index constraints, characterized in that, include: A memory and a processor, the memory storing a computer program, the processor executing the computer program to perform the method provided as claimed in any one of claims 1-8.

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