CN117060484A - Improved self-adaptive control method based on wind-storage combined frequency modulation system - Google Patents
Improved self-adaptive control method based on wind-storage combined frequency modulation system Download PDFInfo
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
- H02J3/241—The oscillation concerning frequency
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/48—Controlling the sharing of the in-phase component
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/50—Controlling the sharing of the out-of-phase component
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/28—The renewable source being wind energy
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Abstract
The invention discloses an improved self-adaptive control method based on a wind-storage combined frequency modulation system, which belongs to the field of electric power, and comprises the following steps: 1) The mathematical model of the doubly-fed wind turbine is obtained by researching the constitution and the working principle of the doubly-fed wind turbine system; 2) The energy storage system is used for stabilizing the power fluctuation based on a filtering method and simulating the sagging characteristic and the inertia link of the thermal power unit to participate in the primary frequency modulation of the system to be combined in the control system, so that the influence of the power fluctuation of the wind storage system on the power system is reduced; 3) The improved virtual synchronous inertia and primary frequency modulation self-adaptive control are provided on the basis of energy storage virtual synchronous control. 4) And simulating and verifying the influence on wind power grid connection in Matlab/Simulink software and the frequency modulation strategy. By the method, uncertainty of wind power output can be effectively overcome, and high frequency stability during large-scale wind power access is realized.
Description
Technical Field
The invention belongs to the field of electric power, and relates to an improved self-adaptive control method based on a wind-storage combined frequency modulation system.
Background
With large-scale grid connection of wind power, the penetration degree of wind power can be increased continuously, a variable speed fan in a power frequency decoupling mode is adopted, zero inertia characteristic is presented in a power grid, and the difficulty of source load power balance is increased due to the fact that wind power has volatility and randomness, and further primary adjustment of frequency is affected. Wind power is greatly influenced by wind speed, the frequency modulation capability is limited, the traditional frequency modulation resource is limited by objective conditions such as response speed, geographical position and the like, the stored energy is rapidly charged and discharged, the regulation instruction of a power grid can be accurately responded, the wind power frequency modulation control system has excellent characteristics in the aspect of system frequency regulation, and the wind power frequency modulation control system is a novel means for assisting wind power in the frequency modulation of the power grid, so that the research on a control strategy for assisting wind power primary frequency modulation by the stored energy of the power grid is necessary.
In practice, the wind-reservoir joint fm control strategy may be divided into three phases. In the first stage, the energy storage system is used for stabilizing power fluctuation based on a filtering method and is combined in the control system by simulating sagging characteristic and inertia link participation system primary frequency modulation of the thermal power unit. The high-frequency power is sent to the energy storage system to be stored, the low-frequency power is sent to the system, the influence of output power fluctuation on the power system is reduced, the primary frequency modulation capability similar to the sagging characteristic and the inertia effect of the thermal power generating unit can be provided to a certain extent, and a certain contribution is made to maintaining the frequency stability of the power system. In the second stage, the output power of the wind turbine generator is decoupled from the power grid frequency in a shorter time scale, so that the stored rotor kinetic energy cannot be actively released. Therefore, a corresponding inertia response strategy needs to be added in the active control link of the fan, so that the kinetic energy stored in the rotor of the fan is released during frequency fluctuation, and the fan can simulate the rotational inertia characteristic of a traditional synchronous generator. And in the third stage, energy storage can actively participate in system frequency adjustment by adding droop control in an energy storage control strategy in a longer time scale, and the droop control of the energy storage can provide additional spare capacity when the frequency is changed.
The invention firstly analyzes the structure, the working principle and the mathematical model of the doubly-fed wind driven generator and the energy storage system, and elaborates the control method of the doubly-fed wind driven generator and the energy storage system. And secondly, analyzing the working principle and a common simulation model of the super capacitor. And on this basis power stabilization strategies are elucidated. Finally, a mathematical equation of primary frequency modulation of the power system is established, the influence of wind power grid connection on inertia and frequency modulation capacity of the power system is analyzed, virtual inertia control of a wind turbine generator set, sagging control and virtual synchronous control of energy storage are analyzed, and an energy storage frequency modulation control method based on self-adaption of virtual synchronous inertia coefficients is provided. And based on MATLAB/Simulink software, performing simulation analysis on the frequency primary adjustment effect and the energy storage action condition of different control strategies under step and continuous load disturbance.
A series of breakthrough researches are carried out in the field of energy storage battery auxiliary power grid frequency modulation, and the research of large-scale energy storage applied to power system frequency modulation has corresponding demonstration projects in China. However, most of control strategies are analyzed from the mathematical perspective based on intelligent algorithms, and from the perspective of power grid frequency characteristics, in a plurality of control strategies, the virtual synchronous machine technology simulates the operation characteristics of a synchronous generator, tracks the frequency in real time, keeps synchronous operation with the power grid, and has great advantages in the aspect of frequency response. Although a series of achievements are successively obtained in the research of the virtual synchronous machine technology at home and abroad, the application of the virtual synchronous machine technology needs further improvement and intensive research in the primary frequency modulation field of the power grid. Therefore, the invention has a certain significance for further in-depth research on the application of the virtual synchronous generator technology in the control strategy of the energy storage system for assisting wind power in primary frequency modulation of the power grid.
Disclosure of Invention
The invention aims at: the improved self-adaptive control method based on the wind-storage combined frequency modulation system overcomes the defects of the prior art, and can enable the frequency of the system to be kept at a very stable level under the condition of large-scale wind power access, so that the stability of the frequency of the system is improved.
The invention aims at realizing the following technical scheme: an improved adaptive control method based on a wind-stored energy joint frequency modulation system, the method comprising:
step 1: analyzing a doubly-fed wind power generator system, and introducing the composition, the working principle and the mathematical model of the doubly-fed wind power generator system;
step 2: the energy storage system is used for stabilizing the power fluctuation based on the filtering method and simulating the sagging characteristic and the inertia link of the thermal power unit to participate in the primary frequency modulation of the system to be combined in the control system, so that the influence of the power fluctuation of the wind storage system on the power system is reduced, and a certain contribution is made to maintaining the frequency stability of the power system.
Step 3: the improved virtual synchronous inertia and primary frequency modulation self-adaptive control are provided on the basis of energy storage virtual synchronous control;
step 4: and simulating and verifying the influence on wind power grid connection in Matlab/Simulink software and the frequency modulation strategy.
Further, the constitution, the working principle and the mathematical model of the doubly-fed wind power generator system in the step 1 are as follows: the wind turbine is used as a prime motor and is an energy capturing element of the whole wind turbine, and wind turbine blades rotate under the action of air to convert wind energy into kinetic energy. Ideally, the kinetic energy captured by the wind turbine is:
wherein v is the windward speed of the blade, m is the air flow quality, ρ is the air density, S is the wind sweeping area, R is the radius of the wind wheel blade, and E is the kinetic energy captured by the wind turbine;
however, in actual operation, energy such as mechanical friction existsThe conversion between rotational kinetic energy and electric energy is not a percentage loss, so that the wind energy utilization coefficient C is often introduced p To represent the relationship of captured wind energy to output mechanical power:
P m for mechanical power generated on the wind turbine shaft system, C p Is a nonlinear function of tip speed ratio lambda and pitch angle beta, as shown in equation (3). If the tip speed ratio is kept unchanged, the wind energy utilization coefficient is reduced along with the increase of the pitch angle; if the pitch angle is unchanged, the pitch angle is firstly increased and then decreased along with the increase of the tip speed ratio. When the tip speed ratio reaches a certain value, the optimal tip speed ratio lambda opt When the pitch angle is reached, the maximum wind energy utilization coefficient C under the pitch angle can be obtained p,max . From Betz's law, it is known that in the ideal case of no resistance C p,max The value is 0.593, and the actual working condition is usually lower than the value, generally between 0.2 and 0.5.
Wherein omega is t The rotation speed of the blade, n is the gear box transformation ratio and omega r Is the rotor rotating speed of the doubly-fed induction generator, c 1 ～c 7 Are constant coefficients of 0.517, 116, 0.45, 5, 21, 0.0068, 0.08 and 0.035, respectively.
The mathematical model of the doubly-fed induction generator is composed of a stator and rotor voltage equation, a flux linkage equation and a torque equation, wherein the voltage equation is shown as a formula (4):
the flux linkage equation is shown in formula (5):
the torque equation is shown in equation (6):
u in the formula sd 、u rd 、u sq And u rq The voltage component of the stator under the d-axis, the voltage component of the rotor under the d-axis, the voltage component of the stator under the q-axis and the voltage component of the rotor under the q-axis are respectively; i.e sd 、i rd 、i sq And i rq The current components of the stator, the rotor, the stator, the rotor and the rotor are respectively under d axis, q axis and q axis; psi phi type sd 、ψ rd ，ψ sq Sum phi rq The magnetic flux components are the magnetic flux components of the stator under the d axis, the magnetic flux components of the rotor under the d axis, the magnetic flux components of the stator under the q axis and the magnetic flux components of the rotor under the q axis; l (L) m Equivalent mutual inductance between stator and rotor windings; l (L) s Is the self-inductance of the stator winding; l (L) r Is the self-inductance of the rotor winding; omega s Is slip angular velocity; omega r The rotor speed of the doubly-fed induction generator is; t (T) e Is electromagnetic torque; r is R s ，R r The resistances of the stator and the rotor are respectively under d and q axes.
The doubly-fed wind turbine rotor side converter adopts vector control of stator voltage orientation, and has the advantages of high accuracy and high stability compared with stator flux linkage vector control. With stator terminal voltage u s The direction of (2) is the d-axis direction of the rotation coordinate system, as shown in formula (7):
because the stator winding frequency is always the power frequency, the resistance is far smaller than the reactance, if the stator resistance is ignored in a steady state operation state, a rotor voltage equation under stator voltage orientation can be obtained as shown in formula (8):
wherein the equation of the disturbance term is shown in formula (9),
wherein Deltau rd And Deltau rq Referred to as the disturbance term,
wherein u is s Is the stator voltage; omega s1 To slip angular velocity omega s1 ＝ω b -ω r ；ω b Is the rated rotation speed.
And then the active and reactive expressions of the stator are shown as the formula (10). From equation (10), it can be found that the vector control of stator voltage orientation realizes the mutual decoupling of the output active power and reactive power of the stator side, and the active power P s Mainly consists of i rd Determining reactive power Q s Mainly consists of i rq And (5) determining. The control objective of the doubly-fed wind turbine rotor side converter is to adjust the active and reactive power of the stator side, so that the doubly-fed wind turbine rotor side converter can be obtained by controlling dq-axis rotor current according to the formula (10).
The rotor-side converter adopts a double closed-loop control mode, wherein the outer ring is a power control ring, and the inner ring is a rotor current control ring.
Similar to the rotor side, the grid side converter also employs stator voltage directional vector control and dual closed loop control strategy, except for its control targets: firstly, the energy quality of the grid-connected fan is ensured, the input current is as sinusoidal as possible, and secondly, the voltage of the direct current bus is kept constant, so that the d-axis of the control outer ring adopts the voltage of the direct current bus.
If the formula (6) is taken as a mathematical model equation of the grid-side converter, substituting the formula (7) to obtain an alternating voltage equation expression of the grid-side converter, wherein the expression is shown as the formula (11):
wherein the disturbance term equation is shown in formula (12):
wherein Deltau gd And Deltau gq Referred to as a perturbation term. u (u) gd The alternating voltage of the grid-side converter on the d axis under the dq coordinate system; u (u) gq The alternating voltage of the grid-side converter on the q axis under the dq coordinate system; s is S d The expression form of the equivalent switching function of the ith phase of the current transformer on the d axis under the dq coordinate system; s is S q The expression form of the equivalent switching function of the ith phase of the converter on the q axis under the dq coordinate system; u (U) dc The direct-current side voltage of the converter; r is R c The equivalent resistance is the alternating current side of the converter; l (L) c The equivalent inductance is the alternating current side of the converter; i.e gd The current is the alternating current of the grid-side converter on the d axis under the dq coordinate system; i.e gq The current is the alternating current of the grid-side converter on the q axis under the dq coordinate system; u (u) s Is the stator terminal voltage;
and then the active power and the reactive power exchanged by the grid-side converter and the power grid are obtained as shown in a formula (13):
the doubly-fed wind turbine generator generally operates in a unit power factor state, namely Q g =0, so the q-axis power outer loop may be omitted.
In step 2, the energy storage system is used for stabilizing the power fluctuation based on the filtering method and simulating the sagging characteristic and the inertia link participation system primary frequency modulation of the thermal power unit to be combined in the control system, so that the wind power storage system is reducedThe effects of system power fluctuations on the power system include: firstly, the fluctuation stabilizing control calculates a power variation delta P capable of representing the variation trend of the output power of the wind power plant according to the output power of the wind power plant by a formula (14) WT . When DeltaP WT >When 0, the output power of the wind farm has an ascending trend, namely the output power is continuously increased in a future period of time, when delta P WT <At 0, the wind farm output power has a decreasing trend, i.e. the output power is continuously reduced in the future.
ΔP WT (t)＝P WT (t)-P WT (t-1) (14)
P in the formula WT (t) and P WT (t-1) is the output power of the wind power plant at the moment t and the output power of the wind power plant before the moment t for 1s respectively;
secondly, dynamically setting a filtering time constant tau according to parameters such as wind power plant output power, wind power plant power variation, system frequency offset, energy storage SOC, energy storage output power and the like in the control process 1 . And based on tau 1 The output power of the wind power plant is divided into a low-frequency part and a high-frequency part according to frequency by adopting a low-pass filtering method. The low-frequency component of the power is used as the target power for stabilizing and controlling the grid-connected wind power by the power fluctuation, and the high-frequency component of the power is born by an energy storage system, as shown in the formulas (15) and (16). Because the output power difference value of the wind power plant before and after stabilization is stored and released by the hybrid energy storage system, the requirement of the access fluctuation limit value of the power system can be met when the wind power plant runs in a maximum power tracking control mode capable of maximally utilizing wind energy, the waste of the partial power difference value is avoided, and the abandoned wind is further reduced.
P hesss ＝-P WTh ＝-(P WT -P WTl ) (16)
P in the formula hesss To stabilize wind farm output power for hybrid energy storage systemsThe reference output power needed to bear by fluctuation; p (P) WTl And P WTh The low frequency component and the high frequency component of the wind farm output power are respectively.
In step 3, a corresponding inertia response strategy needs to be added in the active control link of the fan, so that the kinetic energy stored in the rotor of the fan is released during frequency fluctuation, and the fan can simulate the rotational inertia characteristic of a traditional synchronous generator. By adding corresponding virtual inertia control, the fan can actively release the kinetic energy possessed by the fan when the frequency is changed, so that the output power of the fan is changed to provide a part of extra inertia. After virtual inertia is added to the doubly-fed fan, when the frequency changes, the magnitude of the output power of the added active power is as follows:
wherein: ΔP W1 Frequency modulation power J which can be provided for fan under virtual inertia control W Is the virtual inertia coefficient of the fan; e is kinetic energy captured by the wind turbine; f is the system frequency. The virtual inertia control of the wind turbine generator system is to release or absorb hidden kinetic energy of the wind motor by controlling the rotating speed of the rotor, so that the wind motor generator system can rapidly respond to the frequency change of the system. But also absorbs or releases the kinetic energy during the rotational speed recovery process, so that the virtual inertia control of the fan may cause a secondary drop of the frequency during the frequency recovery process. The virtual inertia control of the fan can only provide short-time power support for the power grid, can not provide extra spare capacity, can not participate in subsequent frequency adjustment, and has no influence on frequency deviation in a steady state.
The sagging control is that when the system frequency is reduced, according to a sagging control curve, the energy storage output extra power participates in the system frequency adjustment at the moment, and the amplitude of the frequency reduction is reduced; when the system frequency rises, the stored energy absorbs additional power, reducing the amplitude of the frequency rise. When the frequency is changed, the energy storage can provide active power according to droop control as follows:
ΔP S1 ＝-K d Δf＝-K d (f-f N ) (19)
wherein: ΔP S1 Power, K, output for energy storage droop control d The sag coefficient is the frequency modulation coefficient of the energy storage system; the method comprises the steps of carrying out a first treatment on the surface of the f (f) N Rated frequency for the system; Δf is the difference between the system frequency and the nominal frequency.
By adding virtual inertia control and droop control in the energy storage control strategy, the energy storage can simulate the frequency modulation characteristic of the traditional synchronous generator, so that the additional inertia can be provided to delay the initial change rate of the frequency, and meanwhile, the active power output by the energy storage can be adjusted according to the system frequency deviation and the droop characteristic, so that the active power participates in the subsequent frequency adjustment. The energy storage system adopts virtual synchronous control to send out power when primary frequency modulation is as follows:
in conventional synchronous generators, the inertia of the generator is typically fixed, but the inertia provided by the stored energy virtual synchronous control is obtained by the added virtual inertia control and is not fixed and is adjustable. Therefore, the invention improves the system frequency stability by adjusting the inertia coefficient in the energy storage virtual synchronous control in real time.
The control strategy based on the frequency deviation amount and the parameter self-adaptive change of the change rate of the frequency deviation amount is designed by comprehensively considering the advantages of the frequency deterioration working condition and the frequency recovery working condition.
In the frequency degradation working condition, the battery energy storage responding to primary frequency modulation is mainly based on virtual inertial force, virtual droop control force is auxiliary, and the self-adaptive adjustment coefficients alpha and eta are set as shown in a formula (22):
the change trend of the two virtual self-adaptive coefficients is adapted to the change characteristics of the power grid frequency under the frequency degradation working condition. At this stage of the frequency deterioration condition, the absolute value of the rate of change of the frequency deviation amount is large, and the absolute value of the frequency deviation amount is small. By utilizing the characteristic that the speed change of the set adjusting coefficient is from quick to slow, the alpha and beta are respectively gradually reduced (increased) and the speed is slower, the frequency deterioration speed is effectively delayed, and the maximum dynamic frequency deviation amount is restrained.
At this stage of the frequency recovery condition, the energy storage in response to primary frequency modulation should be based on the virtual droop force, the virtual inertia control force is used as an auxiliary force, and the setting of the adaptive adjustment coefficient is shown in formula (23):
the change trend of the two virtual self-adaptive coefficients is adapted to the change characteristics of the power grid frequency under the frequency recovery working condition. At this stage of the frequency recovery operation, the absolute value of the rate of change of the frequency deviation amount is small, and the absolute value of the frequency deviation amount is large. By utilizing the characteristic that the speed change of the set adjusting coefficient is from slow to fast, the alpha and beta are respectively gradually increased (reduced) and the speed is slower, the frequency deterioration speed is effectively delayed, and the maximum dynamic frequency deviation amount is restrained.
The wind power acceptance analysis and assessment method based on wind power prediction has the beneficial effects that:
1. aiming at the characteristics of strong wind power fluctuation and randomness, the invention combines the existing researches, and creatively stabilizes the frequency of the system by improving the control method of the self-adaptive wind storage combined frequency modulation system;
2. the energy storage system is used for stabilizing the power fluctuation based on the filtering method and simulating the sagging characteristic and the inertia link of the thermal power unit to participate in the primary frequency modulation of the system to be combined in the control system, so that the influence of the power fluctuation of the wind storage system on the power system is reduced, and a certain contribution is made to maintaining the frequency stability of the power system.
3. According to the wind power grid-connected system, frequency fluctuation in the wind power grid-connected process is considered, as the blades of the fan cannot be frequently regulated, and the fan and the frequency decoupling of the system are used for guaranteeing good economical efficiency, the fan can always keep the output of the maximum power, when the frequency fluctuation occurs in the system, the fan cannot participate in frequency modulation, so that the frequency stability of the system is seriously threatened, and the frequency of the system can be kept stable at a higher level by using the wind power storage combined system.
4. According to the wind power acceptance capacity analysis and assessment method based on wind power prediction, the energy storage system is used for stabilizing power fluctuation based on a filtering method, high-frequency power is sent into the energy storage system to be stored, 50Hz power is connected in a grid mode, and the stabilizing can enable input power of the system to be stable during the grid connection. The method adopts a self-adaptive control strategy, improves the control coefficient, gives a very large damping at the initial stage of frequency change, and has a small damping in the process of frequency recovery, so that the system can keep a relatively stable frequency when encountering interference.
5. The wind power acceptance analysis and assessment method based on wind power prediction is scientific and reasonable, strong in applicability and good in effect, and can provide an auxiliary decision for actual operation scheduling.
Drawings
FIG. 1 is a schematic diagram of a doubly-fed wind turbine;
FIG. 2 is a wind energy utilization coefficient;
fig. 3 is a rotor-side converter control block diagram;
fig. 4 is a network side converter control block diagram;
FIG. 5 is a graph comparing wind power before and after stabilization;
FIG. 6 is a graph of the frequency comparison of a wind-powered storage unit system with adaptively controlled moment of inertia versus constant moment of inertia;
FIG. 7 is a graph comparing frequency fluctuations throughout the frequency modulation process;
FIG. 8 is a flow chart of virtual parameter adaptive control of the wind-powered electricity generation frequency modulation system.
Detailed Description
The following describes the present invention in detail. The present invention may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the invention, so that the invention is not limited to the specific embodiments disclosed.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
An improved adaptive control method based on a wind-stored energy joint frequency modulation system, the method comprising:
step 1: analyzing a doubly-fed wind power generator system, and introducing the composition, the working principle and the mathematical model of the doubly-fed wind power generator system;
step 2: the energy storage system is used for stabilizing the power fluctuation based on the filtering method and simulating the sagging characteristic and the inertia link of the thermal power unit to participate in the primary frequency modulation of the system to be combined in the control system, so that the influence of the power fluctuation of the wind storage system on the power system is reduced, and a certain contribution is made to maintaining the frequency stability of the power system.
Step 3: the improved virtual synchronous inertia and primary frequency modulation self-adaptive control are provided on the basis of energy storage virtual synchronous control;
step 4: and simulating and verifying the influence on wind power grid connection in Matlab/Simulink software and the frequency modulation strategy.
As shown in fig. 1 to 4, in step 1, analyzing a doubly-fed wind power generator system, and introducing the composition, the working principle and the mathematical model of the doubly-fed wind power generator system includes: the double-fed wind turbine generator system comprises a double-fed wind turbine generator system structure, a wind energy utilization coefficient curve, a rotor side converter control mode and a grid side converter control mode.
The double-fed wind power generator system comprises the following components in terms of constitution, working principle and mathematical model: the wind turbine is used as a prime motor and is an energy capturing element of the whole wind turbine, and wind turbine blades rotate under the action of air to convert wind energy into kinetic energy. Ideally, the kinetic energy captured by the wind turbine is:
wherein v is the windward speed of the blade, m is the air flow quality, ρ is the air density, S is the wind sweeping area, R is the radius of the wind wheel blade, and E is the kinetic energy captured by the wind turbine;
however, in actual operation, due to energy loss such as mechanical friction, the conversion between rotational kinetic energy and electric energy is not a percentage, so that the wind energy utilization coefficient C is often introduced p To represent the relationship of captured wind energy to output mechanical power:
P m for mechanical power generated on the wind turbine shaft system, C p Is a nonlinear function of tip speed ratio lambda and pitch angle beta, as shown in equation (3). If the tip speed ratio is kept unchanged, the wind energy utilization coefficient is reduced along with the increase of the pitch angle; if the pitch angle is unchanged, the pitch angle is firstly increased and then decreased along with the increase of the tip speed ratio. When the tip speed ratio reaches a certain value, the optimal tip speed ratio lambda opt When the pitch angle is reached, the maximum wind energy utilization coefficient C under the pitch angle can be obtained p,max . From Betz's law, it is known that in the ideal case of no resistance C p,max The value is 0.593, and the actual working condition is usually lower than the value, generally between 0.2 and 0.5.
Wherein omega is t The rotation speed of the blade, n is the gear box transformation ratio and omega r Is the rotor rotating speed of the doubly-fed induction generator, c 1 ～c 7 Are constant coefficients of 0.517, 116, 0.45, 5, 21, 0.0068, 0.08 and 0.035, respectively.
The mathematical model of the doubly-fed induction generator is composed of a stator and rotor voltage equation, a flux linkage equation and a torque equation, wherein the voltage equation is shown as a formula (4):
the flux linkage equation is shown in formula (5):
the torque equation is shown in equation (6):
u in the formula sd 、u rd 、u sq And u rq The voltage component of the stator under the d-axis, the voltage component of the rotor under the d-axis, the voltage component of the stator under the q-axis and the voltage component of the rotor under the q-axis are respectively; i.e sd 、i rd 、i sq And i rq The current components of the stator, the rotor, the stator, the rotor and the rotor are respectively under d axis, q axis and q axis; psi phi type sd 、ψ rd ，ψ sq Sum phi rq The magnetic flux components are the magnetic flux components of the stator under the d axis, the magnetic flux components of the rotor under the d axis, the magnetic flux components of the stator under the q axis and the magnetic flux components of the rotor under the q axis; l (L) m Equivalent mutual inductance between stator and rotor windings; l (L) s Is the self-inductance of the stator winding; l (L) r Is the self-inductance of the rotor winding; omega s Is slip angular velocity; omega r The rotor speed of the doubly-fed induction generator is; t (T) e Is electromagnetic torque; r is R s ，R r The resistances of the stator and the rotor are respectively under d and q axes.
The doubly-fed wind turbine rotor side converter adopts vector control of stator voltage orientation, and has the advantages of high accuracy and high stability compared with stator flux linkage vector control. With stator terminal voltage u s Is in the direction of rotationThe d-axis direction of the standard system is shown as the formula (7):
because the stator winding frequency is always the power frequency, the resistance is far smaller than the reactance, if the stator resistance is ignored in a steady state operation state, a rotor voltage equation under stator voltage orientation can be obtained as shown in formula (8):
wherein the equation of the disturbance term is shown in formula (9),
wherein Deltau rd And Deltau rq Referred to as the disturbance term,wherein u is s Is the stator voltage; omega s1 To slip angular velocity omega s1 ＝ω b -ω r ；ω b Is rated rotation speed;
and then the active and reactive expressions of the stator are shown as the formula (10). From equation (10), it can be found that the vector control of stator voltage orientation realizes the mutual decoupling of the output active power and reactive power of the stator side, and the active power P s Mainly consists of i rd Determining reactive power Q s Mainly consists of i rq And (5) determining. The control objective of the doubly-fed wind turbine rotor side converter is to adjust the active and reactive power of the stator side, so that the doubly-fed wind turbine rotor side converter can be obtained by controlling dq-axis rotor current according to the formula (10).
The rotor-side converter adopts a double closed-loop control mode, wherein the outer ring is a power control ring, and the inner ring is a rotor current control ring.
Similar to the rotor side, the grid side converter also employs stator voltage directional vector control and dual closed loop control strategy, except for its control targets: firstly, the energy quality of the grid-connected fan is ensured, the input current is as sinusoidal as possible, and secondly, the voltage of the direct current bus is kept constant, so that the d-axis of the control outer ring adopts the voltage of the direct current bus.
If the formula (6) is taken as a mathematical model equation of the grid-side converter, substituting the formula (7) to obtain an alternating voltage equation expression of the grid-side converter, wherein the expression is shown as the formula (11):
wherein the disturbance term equation is shown in formula (12):
wherein Deltau gd And Deltau gq Referred to as a perturbation term. u (u) gd The alternating voltage of the grid-side converter on the d axis under the dq coordinate system; u (u) gq The alternating voltage of the grid-side converter on the q axis under the dq coordinate system; s is S d The expression form of the equivalent switching function of the ith phase of the current transformer on the d axis under the dq coordinate system; s is S q The expression form of the equivalent switching function of the ith phase of the converter on the q axis under the dq coordinate system; u (U) dc The direct-current side voltage of the converter; r is R c The equivalent resistance is the alternating current side of the converter; l (L) c The equivalent inductance is the alternating current side of the converter; i.e gd The current is the alternating current of the grid-side converter on the d axis under the dq coordinate system; i.e gq The current is the alternating current of the grid-side converter on the q axis under the dq coordinate system; u (u) s Is the stator terminal voltage;
and then the active power and the reactive power exchanged by the grid-side converter and the power grid are obtained as shown in a formula (13):
the doubly-fed wind turbine generator generally operates in a unit power factor state, namely Q g =0, so the q-axis power outer loop may be omitted.
In step 2, the energy storage system is used for stabilizing the power fluctuation based on the filtering method and simulating the sagging characteristic and the inertia link participation system primary frequency modulation of the thermal power unit to be combined in the control system, and the reducing of the influence of the power fluctuation of the wind power storage system on the power system comprises the following steps: firstly, the fluctuation stabilizing control calculates a power variation delta P capable of representing the variation trend of the output power of the wind power plant according to the output power of the wind power plant by a formula (14) WT . When DeltaP WT >When 0, the output power of the wind farm has an ascending trend, namely the output power is continuously increased in a future period of time, when delta P WT <At 0, the wind farm output power has a decreasing trend, i.e. the output power is continuously reduced in the future.
ΔP WT (t)＝P WT (t)-P WT (t-1) (14)
P in the formula WT (t) and P WT (t-1) is the output power of the wind power plant at the moment t and the output power of the wind power plant before the moment t for 1s respectively;
secondly, dynamically setting a filtering time constant tau according to parameters such as wind power plant output power, wind power plant power variation, system frequency offset, energy storage SOC, energy storage output power and the like in the control process 1 . And based on tau 1 The output power of the wind power plant is divided into a low-frequency part and a high-frequency part according to frequency by adopting a low-pass filtering method. The low-frequency component of the power is used as the target power for stabilizing and controlling the grid-connected wind power by the power fluctuation, and the high-frequency component of the power is born by an energy storage system, as shown in the formulas (15) and (16). Because the output power difference values of the wind power plant before and after the stabilization are stored and released by the hybrid energy storage system, the wind power plant can still meet the requirement of the access fluctuation limit value of the power system when running in the maximum power tracking control mode capable of maximally utilizing wind energy, the waste of the partial power difference value is avoided, and the wind power plant is further advancedThe wind disposal is reduced in one step.
P hesss ＝-P WTh ＝-(P WT -P WTl ) (16)
P in the formula hesss The reference output power which is needed to be born by the hybrid energy storage system for stabilizing the fluctuation of the output power of the wind farm; p (P) WTl And P WTh The low frequency component and the high frequency component of the wind farm output power are respectively. As shown in FIG. 5, the comparison of the filtering control method based on energy storage and the power before and after filtering shows that the fluctuation of wind power is larger when the power is stabilized without energy storage, the peak value of the wind power is 5.5MW, the trough value is 2.2MW, and the peak-trough difference is 3.3MW. When the energy storage is used for stabilizing the wind power, the peak value of the wind power is 4MW, the trough value is 2.9MW, and the peak-trough difference is 1.1MW. Therefore, the wind power is stabilized by using the energy storage system, and the wind power stability of the input system can be well improved.
In step 3, a corresponding inertia response strategy needs to be added in the active control link of the fan, so that the kinetic energy stored in the rotor of the fan is released during frequency fluctuation, and the fan can simulate the rotational inertia characteristic of a traditional synchronous generator. By adding corresponding virtual inertia control, the fan can actively release the kinetic energy possessed by the fan when the frequency is changed, so that the output power of the fan is changed to provide a part of extra inertia. After virtual inertia is added to the doubly-fed fan, when the frequency changes, the magnitude of the output power of the added active power is as follows:
wherein: ΔP W1 Frequency modulation power J which can be provided for fan under virtual inertia control W Is the virtual inertia coefficient of the fan; e is wind wheelKinetic energy captured by the machine; f is the system frequency. The virtual inertia control of the wind turbine generator system is to release or absorb hidden kinetic energy of the wind motor by controlling the rotating speed of the rotor, so that the wind motor generator system can rapidly respond to the frequency change of the system. But also absorbs or releases the kinetic energy during the rotational speed recovery process, so that the virtual inertia control of the fan may cause a secondary drop of the frequency during the frequency recovery process. The virtual inertia control of the fan can only provide short-time power support for the power grid, can not provide extra spare capacity, can not participate in subsequent frequency adjustment, and has no influence on frequency deviation in a steady state.
The sagging control is that when the system frequency is reduced, according to a sagging control curve, the energy storage output extra power participates in the system frequency adjustment at the moment, and the amplitude of the frequency reduction is reduced; when the system frequency rises, the stored energy absorbs additional power, reducing the amplitude of the frequency rise. When the frequency is changed, the energy storage can provide active power according to droop control as follows:
ΔP S1 ＝-K d Δf＝-K d (f-f N ) (19)
wherein: ΔP S1 Power, K, output for energy storage droop control d The sag coefficient is the frequency modulation coefficient of the energy storage system; f (f) N Rated frequency for the system; Δf is the difference between the system frequency and the nominal frequency.
By adding virtual inertia control and droop control in the energy storage control strategy, the energy storage can simulate the frequency modulation characteristic of the traditional synchronous generator, so that the additional inertia can be provided to delay the initial change rate of the frequency, and meanwhile, the active power output by the energy storage can be adjusted according to the system frequency deviation and the droop characteristic, so that the active power participates in the subsequent frequency adjustment. The energy storage system adopts virtual synchronous control to send out power when primary frequency modulation is as follows:
in conventional synchronous generators, the inertia of the generator is typically fixed, but the inertia provided by the stored energy virtual synchronous control is obtained by the added virtual inertia control and is not fixed and is adjustable. Therefore, the invention improves the system frequency stability by adjusting the inertia coefficient in the energy storage virtual synchronous control in real time.
TABLE 1 virtual inertia selection for different regions
As can be seen from the analysis of Table 1, a positive virtual inertia is added to delay the rate of frequency change at the beginning of the frequency change, and a negative virtual inertia is set at the frequency recovery stage to increase the frequency recovery rate.
The control strategy based on the frequency deviation amount and the parameter self-adaptive change of the change rate of the frequency deviation amount is designed by comprehensively considering the advantages of the frequency deterioration working condition and the frequency recovery working condition.
In the frequency degradation working condition, the battery energy storage responding to primary frequency modulation is mainly based on virtual inertial force, virtual droop control force is auxiliary, and the self-adaptive adjustment coefficients alpha and eta are set as shown in a formula (22):
the change trend of the two virtual self-adaptive coefficients is adapted to the change characteristics of the power grid frequency under the frequency degradation working condition. At this stage of the frequency deterioration condition, the absolute value of the rate of change of the frequency deviation amount is large, and the absolute value of the frequency deviation amount is small. By utilizing the characteristic that the speed change of the set adjusting coefficient is from quick to slow, the alpha and eta are respectively gradually reduced (increased) and the speed is slower, the frequency deterioration speed is effectively delayed, and the maximum dynamic frequency deviation is restrained.
At this stage of the frequency recovery condition, the energy storage in response to primary frequency modulation should be based on the virtual droop force, the virtual inertia control force is used as an auxiliary force, and the setting of the adaptive adjustment coefficient is shown in formula (23):
the change trend of the two virtual self-adaptive coefficients is adapted to the change characteristics of the power grid frequency under the frequency recovery working condition. At this stage of the frequency recovery operation, the absolute value of the rate of change of the frequency deviation amount is small, and the absolute value of the frequency deviation amount is large. By utilizing the characteristic that the speed change of the set adjusting coefficient is from slow to fast, the alpha and beta are respectively gradually increased (reduced) and the speed is slower, the frequency deterioration speed is effectively delayed, and the maximum dynamic frequency deviation amount is restrained. Fig. 6-7 are frequency comparisons of wind-stored-energy systems incorporating adaptively controlled moment of inertia versus constant moment of inertia, and frequency changes over longer time scales. From the data of fig. 6 and 7, it can be seen that the frequency modulation process is not ideal when the wind reservoir system employs a constant moment of inertia. When the system is disturbed, the frequency of the wind storage system adopting constant rotational inertia drops to 49.55 once, and the response to frequency recovery is not very timely, so that the difference is larger than that of the wind storage system adopting self-adaptive virtual inertia. Under the continuous disturbance simulation within 100s, the frequency fluctuation of the wind-storage combined system controlled by the self-adaptive parameters can be obviously seen to be small, the recovery speed is high, and the stability and the qualitative of the system are greatly facilitated.
The technical features of the above-described embodiments may be arbitrarily combined, and in order to simplify the description, all possible combinations of the technical features in the above-described embodiments are not exhaustive, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims.
Claims (8)
1. An improved self-adaptive control method based on a wind-storage combined frequency modulation system is characterized by comprising the following steps:
step 1: analyzing a doubly-fed wind power generator system, and introducing the composition, the working principle and the mathematical model of the doubly-fed wind power generator system;
step 2: the energy storage system is used for stabilizing the power fluctuation based on a filtering method and simulating the sagging characteristic and the inertia link of the thermal power unit to participate in the primary frequency modulation of the system to be combined in the control system, so that the influence of the power fluctuation of the wind storage system on the power system is reduced, and the contribution to maintaining the frequency stability of the power system is made;
step 3: virtual synchronous inertia and primary frequency modulation self-adaptive control are provided on the basis of energy storage virtual synchronous control;
step 4: and simulating and verifying the influence of wind power grid connection and a frequency modulation strategy in Matlab/Simulink software.
2. The improved adaptive control method based on a wind-energy-storage combined frequency modulation system according to claim 1, wherein in step 1, the wind turbine is an energy capturing element of the whole wind turbine, the wind turbine blade rotates under the action of air to convert wind energy into kinetic energy, and in an ideal state, the kinetic energy captured by the wind turbine is:
wherein v is the windward speed of the blade, m is the air flow quality, ρ is the air density, S is the wind sweeping area, and R represents the radius of the wind wheel blade; e is kinetic energy captured by the wind turbine;
in actual operation, the wind energy utilization coefficient C is introduced p To represent the relationship of captured wind energy to output mechanical power:
P m for mechanical power generated on the wind turbine shaft system, C p Is a nonlinear function of tip speed ratio lambda and pitch angle beta, as shown in equation (3);
wherein omega is t The rotation speed of the blade, n is the gear box transformation ratio and omega r Is the rotor rotating speed of the doubly-fed induction generator, c 1 ～c 8 Are constant coefficients of 0.517, 116, 0.45, 5, 21, 0.0068, 0.08 and 0.035, respectively.
3. The improved adaptive control method based on a wind-stored energy joint frequency modulation system according to claim 2, wherein when the tip speed ratio λ reaches the optimum tip speed ratio λ opt Obtaining the maximum wind energy utilization coefficient C under the pitch angle beta p,max In the ideal case of no resistance C p,max Takes a value of 0.593, and the actual working condition C p,max Between 0.2 and 0.5.
4. The improved adaptive control method based on a wind-stored energy joint frequency modulation system according to claim 1, wherein in step 1, the mathematical model of the doubly-fed induction generator comprises a stator-rotor voltage equation, a flux linkage equation and a torque equation, wherein the voltage equation is represented by formula (4):
the flux linkage equation is shown in formula (5):
the torque equation is shown in equation (6):
u in the formula sd 、u rd 、u sq And u rq The voltage component of the stator under the d-axis, the voltage component of the rotor under the d-axis, the voltage component of the stator under the q-axis and the voltage component of the rotor under the q-axis are respectively; i.e sd 、i rd 、i sq And i rq The current components of the stator, the rotor, the stator, the rotor and the rotor are respectively under d axis, q axis and q axis; psi phi type sd 、ψ rd ，ψ sq Sum phi rq The magnetic flux components are the magnetic flux components of the stator under the d axis, the magnetic flux components of the rotor under the d axis, the magnetic flux components of the stator under the q axis and the magnetic flux components of the rotor under the q axis; l (L) m Equivalent mutual inductance between stator and rotor windings; l (L) s Is the self-inductance of the stator winding; l (L) r Is the self-inductance of the rotor winding; omega s Is slip angular velocity; omega r The rotor speed of the doubly-fed induction generator is; t (T) e Is electromagnetic torque; r is R s ，R r The resistances of the stator and the rotor are respectively under d and q axes.
5. The improved self-adaptive control method based on wind-storage combined frequency modulation system according to claim 4, wherein the rotor-side converter of the doubly-fed wind turbine adopts vector control of stator voltage orientation, and uses stator terminal voltage u s The direction of (2) is the d-axis direction of the rotation coordinate system, as shown in formula (7):
the rotor voltage equation under stator voltage orientation is shown as (8):
wherein the equation of the disturbance term is shown in formula (9),
wherein Deltau rd And Deltau rq Referred to as the disturbance term,
wherein u is s Is the stator voltage; omega s1 To slip angular velocity omega s1 ＝ω b -ω r ；ω b Is rated rotation speed;
the expression of the stator active and reactive is shown as the formula (10), P s For active power, Q s Is reactive power;
the rotor-side converter adopts a double closed-loop control mode, wherein the outer ring is a power control ring, and the inner ring is a rotor current control ring.
6. The improved self-adaptive control method based on the wind-storage combined frequency modulation system according to claim 4, wherein the network-side converter also adopts stator voltage directional vector control and double closed-loop control strategies, and the network-side converter alternating voltage equation expression is shown as formula (11):
wherein the disturbance term equation is shown in formula (12):
wherein Deltau gd And Deltau gq Called disturbance terms; u (u) gd The alternating voltage of the grid-side converter on the d axis under the dq coordinate system; u (u) gq The alternating voltage of the grid-side converter on the q axis under the dq coordinate system; s is S d The expression form of the equivalent switching function of the ith phase of the current transformer on the d axis under the dq coordinate system; s is S q The expression form of the equivalent switching function of the ith phase of the converter on the q axis under the dq coordinate system; u (U) dc The direct-current side voltage of the converter; r is R c The equivalent resistance is the alternating current side of the converter; l (L) c The equivalent inductance is the alternating current side of the converter; i.e gd The current is the alternating current of the grid-side converter on the d axis under the dq coordinate system; i.e gq The current is the alternating current of the grid-side converter on the q axis under the dq coordinate system; u (u) s Is the stator terminal voltage;
active power P exchanged between network side converter and power grid g And reactive power Q g As shown in formula (13):
7. the improved self-adaptive control method based on a wind power storage joint frequency modulation system according to claim 1, wherein in step 2, the energy storage system is utilized to combine the power fluctuation stabilization based on a filtering method and the primary frequency modulation of the system participating in imitating the sagging characteristic and inertia link of a thermal power unit in a control system, and the reduction of the influence of the power fluctuation of the wind power storage system on the power system comprises the following steps: wave stabilization control obtains a power variation delta P capable of representing the variation trend of the output power of the wind power plant according to the output power of the wind power plant through calculation of (14) WT The method comprises the steps of carrying out a first treatment on the surface of the When DeltaP WT >When 0, the output power of the wind power plant has an ascending trend, and when delta P is WT <When 0, the output power of the wind power plant has a descending trend;
ΔP WT (t)＝P WT (t)-P WT (t-1) (14)
p in the formula WT (t) and P WT (t-1) is the output power of the wind power plant at the moment t and the output power of the wind power plant before the moment t for 1s respectively;
dynamically setting a filtering time constant tau according to parameters of wind power plant output power, wind power plant power variation, system frequency offset, energy storage SOC and energy storage output power in a control process 1 Dividing the output power of the wind power plant into a low-frequency part and a high-frequency part according to frequency, wherein the low-frequency part of the power is used as the target power for stabilizing and controlling wind power grid connection by power fluctuation, and the high-frequency part of the power is born by an energy storage system, as shown in a formula (15) and a formula (16);
P hesss ＝-P WTh ＝-(P WT -P WTl ) (16)
p in the formula hesss The reference output power which is needed to be born by the hybrid energy storage system for stabilizing the fluctuation of the output power of the wind farm; p (P) WTl And P WTh The low frequency component and the high frequency component of the wind farm output power are respectively.
8. The improved adaptive control method based on a wind-energy-storage combined frequency modulation system according to claim 1, wherein in step 3, virtual synchronous inertia and primary frequency modulation adaptive control are provided on the basis of energy storage virtual synchronous control, and the method comprises the following steps: after virtual inertia is added to the doubly-fed fan, when the frequency changes, the magnitude of the output power of the added active power is as follows:
wherein: ΔP W1 Frequency modulation power J which can be provided for fan under virtual inertia control W Is the virtual inertia coefficient of the fan; e is kinetic energy captured by the wind turbine; f is the system frequency;
when the frequency is changed, the energy storage can provide active power according to droop control as follows:
ΔP S1 ＝-K d Δf＝-K d (f-f N ) (19)
ΔP S1 power, K, output for energy storage droop control d The sag coefficient is the frequency modulation coefficient of the energy storage system; f (f) N Rated frequency for the system; Δf is the difference between the system frequency and the nominal frequency;
virtual inertia control and sagging control are added in an energy storage control strategy, and the energy storage system adopts virtual synchronous control to send out power when frequency modulation is carried out, wherein the power is as follows:
the control strategy for parameter self-adaptive change based on the frequency deviation amount and the change rate thereof is designed by comprehensively considering the advantages of the frequency deterioration working condition and the frequency recovery working condition, wherein the control strategy comprises the following steps:
in the frequency degradation working condition, the battery energy storage responding to primary frequency modulation is mainly based on virtual inertial force, virtual droop control force is auxiliary, and the self-adaptive adjustment coefficients alpha and eta are set as shown in a formula (22):
at this stage of the frequency recovery condition, the energy storage in response to primary frequency modulation should be based on the virtual droop force, the virtual inertia control force is used as an auxiliary force, and the setting of the adaptive adjustment coefficient is shown in formula (23):
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