CN106786768B - Active interference suppression method and system for load frequency of power system - Google Patents
Active interference suppression method and system for load frequency of power system Download PDFInfo
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Abstract
The invention discloses a method and a system for restraining active interference of load frequency of a power system, wherein the method comprises the following steps: establishing a state space model of a controlled object including a wind power plant power system based on a load frequency control model of a traditional power system; based on the equivalent input interference idea, the influence of the load disturbance of the power system and the random fluctuation of the wind speed on the output is estimated by adopting an internal model, a state feedback controller, a full-dimensional state observer and an interference estimator on the controlled object, the estimated influence is mapped to the input end of the power system, and the disturbance is reversely compensated.
Description
Technical Field
The invention relates to a load frequency control technology of a power system, in particular to a load frequency active interference suppression method and system of an interconnected power system with a large-scale wind power plant.
Background
In order to deal with the increase of energy demand and the deterioration of environment, clean renewable energy sources are vigorously developed in China, and the permeability of wind energy in a power system is remarkably improved. However, due to the random fluctuation of wind power, the weakness of grid structure in wind power development areas and the unreasonable development mode, the frequency stability of the power system is facing more challenges. As a mainstream model of a wind power plant, a frequency relation between a double-fed asynchronous wind turbine generator and a permanent magnet synchronous wind turbine generator is decoupled from a power system, which directly causes the reduction of active-frequency control inertia of the system. In addition, the random fluctuation of wind energy, and the influence of the input and the exit of the wind energy in the power grid on the normal operation of the load and the safety and the stability of the power system cannot be ignored. With the gradual enhancement of the interconnection degree between the power systems, the complexity degree and the scale of the power systems are gradually increased, and the tie-line trend between different areas is gradually developed into an important loop of the frequency control of the power systems. As an important means for maintaining the frequency stability of the power system, a Load Frequency Control (LFC) technology is becoming an important research field of the current wind power grid-connected power system.
In the LFC design of power systems, the well-developed PID controller is still the first to get attention. However, under the complicated and variable operating conditions of the wind power plant, the practicability of the fixed parameter controller is greatly reduced, and the fixed parameter controller cannot adapt to an interconnected power system containing a large-scale wind power plant.
Disclosure of Invention
In order to overcome the above-mentioned deficiencies of the prior art, an object of the present invention is to provide a method and a system for suppressing active disturbance of load frequency of an electrical power system, wherein the load frequency control strategy parameters are flexibly designed and have a good capability of suppressing active disturbance.
In order to achieve the above and other objects, the present invention provides an active interference suppression method for load frequency of an electrical power system, comprising the following steps:
firstly, establishing a state space model of a controlled object including a wind power plant power system based on a load frequency control model of a traditional power system;
and secondly, estimating the influence of the load disturbance and the random fluctuation of the wind speed of the power system on the output by adopting an internal model, a state feedback controller, a full-dimensional state observer and a disturbance estimator based on an equivalent input disturbance idea, mapping the estimation to the input end of the power system, and performing reverse compensation on the disturbance to realize the active suppression of the frequency disturbance of the power system.
Further, in the first step, the following state space model is established:
wherein the content of the first and second substances,
ui(t)＝[ΔPciΔVqri]T
wi(t)＝[ΔPdiΔTmiΔfj]T，yi(t)＝[ΔfiΔωi]T
wherein, Δ PcFor load reference deviation, Δ VqrFor doubly-fed generator rotor voltage deviation, Δ iqrFor doubly-fed generator rotor current deviation, Δ PtieFor tie line power deviation, Δ PdFor load disturbance, delta f is frequency deviation and delta omega is rotation speed deviation of the doubly-fed wind turbine generator, delta Pv、ΔPmAnd Δ PeRespectively representing the deviation of the valve opening position instruction, the deviation of the output mechanical power of the steam turbine and the deviation of the output power of the wind generating set, D is the ratio of the percentage of load change to the percentage of frequency change, M is the inertia constant of the generatortIs inertia constant of wind turbine generator, R is difference adjustment coefficient, X2For the conductance, X, of wind turbines3＝Lm/(Lm+Ls)，LmAnd LsMutual inductance coefficient of stator and rotor of wind turbine generator and self-inductance coefficient of stator, IoptAnd WoptRespectively, to approximate the model to the optimal parameter of the actual system, TTAnd TGTime constants, T, of speed regulators and turbines, respectivelyijFor stiffness constants, the superscripts i, j represent the areas i and j of the power system, and w (t) is the external disturbance of the power system.
Further, the second step further comprises:
step S1, establishing an internal model to accurately track the reference input;
step S2, constructing a full-dimensional state observer to reconstruct the state of the controlled object;
step S3, establishing an expansion system of the controlled power system and the internal model, and optimally obtaining the feedback gain of the state feedback controller from the angle of minimum energy by using an LQR method;
and step S4, estimating the influence of the load disturbance of the power system and the random fluctuation of the wind speed on the output by using the interference estimator, acquiring an equivalent input interference estimation value and mapping the equivalent input interference estimation value to the input end of the power system.
Further, in step S4, the equivalent input interference obtained by the interference estimator is filtered by the low pass filter to output the measurement noise, and then the measurement noise is input to the input terminals of the wind turbine generator and the conventional generator respectively.
Further, the internal model formula is:
wherein x isR(t) is a state variable, ARIs a system matrix, BRTo input the matrix, Δ yref(t) is the ideal output deviation, and the outputs of the power system are y (t), Δ yref(t)＝0。
Further, the full-dimensional state observer is as follows:
wherein the content of the first and second substances,
for the reconstructed state of state x (T), Φ is Hurwitz matrix, Ψ is gain matrix, and the non-singular matrix T satisfies TA- Φ T ═ Ψ C, and the matrix satisfies ═ TB.
Further, in step S2, gain matrices Φ and Ψ of the full-dimensional state observer are obtained by using a pole allocation algorithm, where [ Φ Ψ ] is a fully controllable matrix.
Further, in step S3, an extended system of the controlled power system and the internal model is established
Wherein the content of the first and second substances,
Δyref(t) is the ideal output deviation. Optimal acquisition of state feedback controller from energy minimum angle by using LQR (Low-rank response) method
Feedback gain K ofPAnd KR，
Wherein R isKThe undetermined positive real number in the secondary performance index based on the system state and control needs to be selected according to the coefficient matrix of the expansion system, and P satisfies the requirement
Further, in step S4, an interference estimator is used to obtain the equivalent input interference before filtering:
wherein B is+＝(BTB)-1BT。
In order to achieve the above object, the present invention further provides an active interference suppression system for load frequency of an electrical power system, comprising a state space model building unit, an internal model, a state feedback controller, a full-dimensional state observer, an interference estimator and an electrical power system including a wind farm, wherein the active interference suppression system for load frequency of the electrical power system utilizes the state space model building unit to build a load frequency control model based on a traditional electrical power system, builds a state space model of a controlled object including the electrical power system of the wind farm, estimates the influence of load disturbance and random fluctuation of wind speed on the output of the electrical power system based on the controlled object by using the internal model, the state feedback controller, the full-dimensional state observer and the interference estimator, maps the estimated influence to the input end of the electrical power system including the wind farm, and performs reverse compensation on the disturbance, and active suppression of frequency disturbance of the power system is realized.
Compared with the prior art, the method and the system for restraining the active interference of the load frequency of the power system have the advantages that the state space model containing the large-scale wind power plant power system is established, the state of the controlled object is reconstructed by adopting the full-dimensional state observer, the influence of the load disturbance of the power system and the random fluctuation of the wind speed on the output is estimated based on the idea of equivalent input interference and is mapped to the input end of the system, the input end disturbance is estimated and reversely compensated, so that the active restraint of the wind power fluctuation and other external interference is realized, the fluctuation of the system frequency in a safe and reasonable range is maintained and the stability is finally achieved, the state observer and the state feedback controller can be separately designed, the state observer is designed by adopting a pole configuration method, the state feedback gain is optimized and obtained by adopting an LQR method, and the stability of the control system is judged by utilizing a small, the load frequency control strategy of the invention has flexible parameter design and good disturbance active suppression capability.
Drawings
FIG. 1 is a flowchart illustrating steps of a method for suppressing active interference of a load frequency of an electrical power system according to the present invention;
FIG. 2 is a diagram of a system architecture of an active interference suppression system for load frequency of an electrical power system according to the present invention;
FIG. 3 is a schematic diagram of an LFC model including a wind farm power system in an exemplary embodiment of the invention;
FIG. 4 is a block diagram of a load frequency active interference suppression structure of a power system including a wind farm in an exemplary embodiment of the invention;
FIG. 5 is a block diagram of a separate design structure of a control system according to an embodiment of the present invention;
FIG. 6 is a dynamic response diagram of a power system including a wind farm under random disturbance of a load in an embodiment of the present invention; wherein (a) is a load disturbance; (b) is a frequency deviation; (c) the rotating speed deviation of the wind turbine generator is obtained;
FIG. 7 is a dynamic response diagram of a power system including a wind farm under random fluctuation of wind speed in an embodiment of the present invention; wherein, (a) is the change of mechanical torque of the fan; (b) is a frequency deviation; (c) the rotating speed deviation of the wind turbine generator is obtained;
FIG. 8 is a power response diagram of a tie line of a dual-region power system including a wind farm under random load disturbance according to an embodiment of the present invention, where (a) is load disturbance; (b) responding to tie line power under different control strategies; (c) tie-line power response is controlled for the EID-based load frequency control strategy.
Detailed Description
Other advantages and capabilities of the present invention will be readily apparent to those skilled in the art from the present disclosure by describing the embodiments of the present invention with specific embodiments thereof in conjunction with the accompanying drawings. The invention is capable of other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention.
Fig. 1 is a flowchart illustrating steps of an active interference suppression method for load frequency of an electrical power system according to the present invention. As shown in fig. 1, the method for suppressing active interference of load frequency of power system of the present invention includes the following steps:
In a specific embodiment of the present invention, the state space model is as follows:
wherein the content of the first and second substances,
ui(t)＝[ΔPciΔVqri]T
wi(t)＝[ΔPdiΔTmiΔfj]T，yi(t)＝[ΔfiΔωi]T
wherein, Δ PcFor load reference deviation, Δ VqrFor doubly-fed generator rotor voltage deviation, Δ iqrFor doubly-fed generator rotor current deviation, Δ PtieFor tie line power deviation, Δ PdFor load disturbance, delta f is frequency deviation and delta omega is rotation speed deviation of the doubly-fed wind turbine generator, delta Pv、ΔPmAnd Δ PeRespectively representing the deviation of the valve opening position instruction, the deviation of the output mechanical power of the steam turbine and the deviation of the output power of the wind generating set, D is the ratio of the percentage of load change to the percentage of frequency change, M is the inertia constant of the generatortIs inertia constant of wind turbine generator, R is difference adjustment coefficient, X2For the conductance, X, of wind turbines3＝Lm/(Lm+Ls)，LmAnd LsMutual inductance coefficient of stator and rotor of wind turbine generator and self-inductance coefficient of stator, IoptAnd WoptRespectively, to approximate the model to the optimal parameter of the actual system, TTAnd TGTime constants, T, of speed regulators and turbines, respectivelyijFor stiffness constants, the superscripts i, j represent the areas i and j of the power system, and w (t) is the external disturbance of the power system.
And 102, estimating the influence of load disturbance and random fluctuation of wind speed on output of the power system based on an equivalent input interference (EID) thought and a controlled object by adopting an internal model, a state feedback controller, a full-dimensional state observer and an interference estimator, and mapping the influence to the input end of the power system.
Specifically, step 102 further comprises:
at step S1, an internal model is built to accurately track the reference input. In an embodiment of the present invention, an internal model is built
Including a state variable xR(t), System matrix ARInput matrix BRIdeal output deviation Δ yref(t), the output of the power system y (t). Δ yref(t) is 0, so parameter ARAnd BRCan be determined directly.
Step S2, constructing a full-dimensional state observer
Reconstructing the state of the controlled object, wherein phi, psi and are undetermined matrixes,
is the reconstructed state of state x (t), z (t) is the state estimation variable, uf(t) is an initial control input. To ensure the convergence of the observer, Φ is the Hurwitz matrix, and the non-singular matrix T satisfies TA- Φ T ═ Ψ C, and the matrix satisfies ═ TB.
Preferably, in step S2, a gain matrix Ψ of the state observer is obtained by using a pole allocation algorithm, where [ Φ Ψ ] is a fully controllable matrix. The flexibility of parameter design is increased by adopting a pole allocation algorithm, and the limit of the position of a zero pole of a controlled object is avoided.
Step S3, establishing an extended system of the controlled power system and the internal model
Wherein the content of the first and second substances,
here A, B and C are the matrices of the state space model in step 101, ayref(t) is the ideal output deviation. Optimal acquisition of state feedback controller from the point of minimum energy by using LQR (Linear quadratic form optimal adjustment) method
Feedback gain K ofPAnd KR，
Wherein R isKSelecting undetermined positive real numbers in secondary performance indexes based on system states and control according to a coefficient matrix of an expansion system; p satisfies
And step S4, estimating the influence of the load disturbance of the power system and the random fluctuation of the wind speed on the output by using the interference estimator, acquiring an equivalent input interference estimation value and mapping the equivalent input interference estimation value to the input end of the power system.
Preferably, after step S4, the method further includes:
and (3) filtering the equivalent input interference acquired by the interference estimator by using a low-pass filter to output measurement noise, and acquiring control signals respectively input to the wind turbine generator and the conventional generator set under the combined action of the measurement noise and the state feedback control signal.
In the specific embodiment of the invention, an interference estimator is adopted to obtain the equivalent input interference before filtering:
wherein B is+＝(BTB)-1BT。
Using a low-pass filter F(s) of 1/(T)2s +1) Filtering the output measurement noise, where T2Is the filter time constant.
Is obtained by passing through a filter
Finally, obtaining a control input:
in the embodiment of the invention, the sufficient condition | G for the stability of the closed-loop control system is obtained by the small gain theoremw(s)F(s)||∞Less than or equal to 1. Wherein G isw(s) is
To
Transfer function G ofw(s)＝B+(T-1ΦT-A)(sI-T-1ΦT)-1B+1＝B+(sI-A)T-1(sI-Φ)-1TB, F(s) are filters. The matrix Φ is known as the Hurwitz matrix, so Gw(s) stabilization; let F(s) be 1/(T)2s +1), then F(s) stabilizes. Therefore, the load frequency active interference suppression system designed by the invention is stable, I in sI is a unit matrix, and s is a variable of Laplace transform and is a default symbol.
Fig. 2 is a system architecture diagram of an active interference suppression system for load frequency of an electrical power system according to the present invention. As shown in fig. 2, the present invention provides an active interference suppression system for load frequency of power system, including: a state space model building unit 201, an internal model 202, a state feedback controller 203, a full-dimensional state observer 204, a disturbance estimator 205 and a power system 206 comprising a wind farm.
Specifically, the active interference suppression system for load frequency of the power system utilizes a state space model establishing unit 201 to establish a state space model 201 of the power system including the wind farm based on an LFC (load frequency control) model of the conventional power system, and based on an equivalent input interference (EID) concept, estimates the influence of load disturbance and random fluctuation of wind speed on the output of the power system based on a controlled object by using an internal model 202, a state feedback controller 203, a full-dimensional state observer 204 and an interference estimator 205, and maps the estimated influence to the input end of the power system including the wind farm.
In the embodiment of the present invention, the model of the state space model 201 is as follows:
wherein the content of the first and second substances,
ui(t)＝[ΔPciΔVqri]T
wi(t)＝[ΔPdiΔTmiΔfj]T，yi(t)＝[ΔfiΔωi]T
wherein, Δ PcFor load reference deviation, Δ VqrFor doubly-fed generator rotor voltage deviation, Δ iqrFor doubly-fed generator rotor current deviation, Δ PtieFor tie line power deviation, Δ PdFor load disturbance, delta f is frequency deviation and delta omega is rotation speed deviation of the doubly-fed wind turbine generator, delta Pv、ΔPmAnd Δ PeRespectively representing the deviation of the valve opening position instruction, the deviation of the output mechanical power of the steam turbine and the deviation of the output power of the wind generating set, D is the ratio of the percentage of load change to the percentage of frequency change, M is the inertia constant of the generatortIs inertia constant of wind turbine generator, R is difference adjustment coefficient, X2For the conductance, X, of wind turbines3＝Lm/(Lm+Ls)，LmAnd LsMutual inductance coefficient of stator and rotor of wind turbine generator and self-inductance coefficient of stator, IoptAnd WoptRespectively, to approximate the model to the optimal parameter of the actual system, TTAnd TGTime constants, T, of speed regulators and turbines, respectivelyijFor stiffness constants, the superscripts i, j represent the areas i and j of the power system, and w (t) is the external disturbance of the power system.
An internal model 202 for accurately tracking the reference input. In a specific embodiment of the invention, the internal model is as follows:
due to the ideal output deviation Δ yrefIs zero, parameter ARAnd BRCan directly determine
The full-dimensional state observer 204 is used for reconstructing the state of a controlled object (including a power system of a wind power plant), and the model formula is as follows:
wherein phi, psi and are undetermined matrixes,
is the reconstructed state of state x (t), z (t) is the state estimation variable, uf(t) is an initial control input. To ensure the convergence of the observer, Φ is the Hurwitz matrix, and the non-singular matrix T satisfies TA- Φ T ═ Ψ C, and the matrix satisfies ═ TB.
Preferably, in the present invention, the gain matrices Φ and Ψ of the state observer are obtained using a pole placement algorithm, where Φ Ψ is a fully controllable matrix. The flexibility of parameter design is increased by adopting a pole allocation algorithm, and the limit of the position of a zero pole of a controlled object is avoided.
The interference estimator 205 obtains an estimated value of the equivalent input interference through calculation, and a control signal of the active interference suppression system is obtained through the combined action of the state feedback controller 203 and the interference estimator 205. Specifically, an extended system by building controlled power systems and internal models
Wherein the content of the first and second substances,
Δyref(t) is the ideal output deviation. Using LQR (Linear quadratic form optimal adjustment) method to optimize from the angle of minimum energyState feedback controller for chemical acquisition
Feedback gain K ofPAnd KR，
Wherein R isKThe undetermined positive real number in the secondary performance index based on the system state and control needs to be selected according to the coefficient matrix of the expansion system, and P satisfies the requirement
Then, the interference estimator 205 is used to estimate the influence of the load disturbance of the power system and the random fluctuation of the wind speed on the output, and an equivalent input interference estimation value is obtained and mapped to the input end of the power system.
Preferably, the interference estimator 205 further employs a low-pass filter to filter the equivalent input interference and output the measurement noise, and the measurement noise and the state feedback control signal cooperate to obtain the control signals respectively input to the wind turbine generator and the conventional generator.
In the specific embodiment of the invention, an interference estimator is adopted to obtain the equivalent input interference before filtering:
wherein B is+＝(BTB)-1BT。
Using a low-pass filter F(s) of 1/(T)2s +1) Filtering the output measurement noise, where T2Is the filter time constant.
Is obtained by passing through a filter
Finally, obtaining a control input:
the invention will be further illustrated by the following specific examples: in the specific embodiment of the invention, a double-region power system is taken as an example, and the effectiveness of the proposed active interference suppression method in an interconnected power system comprising a large-scale wind power plant is verified. The method can realize the coordination control of the wind power plant and the power system, effectively inhibit the frequency fluctuation of the system, the power output of the wind power plant and the power fluctuation of the regional tie line under the random fluctuation of wind speed and load disturbance, and comprises the following steps:
1) based on the LFC model of the traditional power system, the LFC model containing the wind power plant power system is built, and is shown in FIG. 3. And constructing a corresponding state space model in Matlab/Simulink
Table 1 shows parameters of the dual-region power system model.
TABLE 1 contains LFC model parameters of wind farm power system
2) An active interference suppression system was built in Matlab/Simulink according to fig. 4 and 5: obtaining state observer by pole allocation method
Secondary performance index based on system state and control by adopting LQR (Low-grade quick response) method
Obtaining state feedback gain K from the angle of minimum energy optimizationPAnd KR(ii) a Obtaining an equivalent input interference estimation value before filtering by adopting an interference estimator; using a low-pass filter F(s) of 1/(T)2s +1) filtering and outputting the measurement noise, and acquiring control signals respectively input into the wind turbine generator set and the conventional generator set. The control system is verified to be stable according to the small gain theorem.
3) In a containerRandom load disturbance delta P input in LFC model of large-scale wind power plant power systemdComparing the dynamic response of the power system including the wind farm under different control conditions, as shown in fig. 6. The frequency deviation delta f represents the frequency fluctuation of the power system, and the rotating speed deviation delta omega of the wind turbine generator represents the active power fluctuation of the wind power plant input power grid. Simulation results show that compared with the traditional load frequency control strategy, the load frequency active interference suppression strategy (EID-LFC) based on equivalent input interference provided by the invention has a better disturbance suppression effect on random load disturbance.
4) Inputting wind speed random fluctuation in an LFC model containing a large-scale wind power plant electric power system, wherein the random fluctuation of the wind speed adopts the change delta T of the mechanical torque of a fanmShowing the dynamic response of the power system including the wind farm in comparison to different control conditions, as shown in fig. 7. Simulation results show that compared with the traditional load frequency control strategy, the EID-LFC provided by the invention has a better inhibiting effect on the frequency fluctuation of a power system and the output power fluctuation of a wind power plant caused by the random fluctuation of wind speed.
5) Inputting random load disturbance delta P in LFC model containing large-scale wind power plant electric power systemdComparing power response delta P of connecting line of double-area power system with wind power plant under different control conditionstieAs shown in fig. 8. Simulation results show that compared with the traditional load frequency control strategy, the EID-LFC provided by the invention has a better suppression effect on the tie line power fluctuation of a multi-region power system.
In summary, the method and system for suppressing active interference of load frequency of power system of the present invention builds a state space model containing large-scale wind power plant power system, adopts a full-dimensional state observer to construct a load frequency control system structure, estimates the influence of load disturbance and random fluctuation of wind speed on the output of the power system, maps the estimated influence to the input end of the system, estimates and reversely compensates the input end disturbance to realize active suppression of wind power fluctuation and other external interference, maintains the fluctuation of system frequency within a safe and reasonable range, and finally achieves stability, the state observer and the state feedback controller of the present invention can be separately designed, and adopts a pole allocation method to design the state observer, adopts an LQR method to optimize and obtain state feedback gain, utilizes a small gain theorem to judge the stability of the control system, and has flexible design of load frequency control strategy parameters, and has good disturbance active inhibition capability.
Modifications and variations can be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the present invention. Therefore, the scope of the invention should be determined from the following claims.
Claims (4)
1. A method for suppressing active interference of load frequency of an electric power system comprises the following steps:
firstly, establishing a state space model of a controlled object including a wind power plant power system based on a load frequency control model;
estimating the influence of load disturbance and random fluctuation of wind speed on output of the power system by adopting an internal model, a state feedback controller, a full-dimensional state observer and an interference estimator based on an equivalent input interference idea, mapping the estimation to the input end of the power system, and performing reverse compensation on the disturbance to realize active suppression on frequency disturbance of the power system;
in the first step, the following state space model is established:
wherein the content of the first and second substances,
ui(t)＝[ΔPciΔVqri]T
wi(t)＝[ΔPdiΔTmiΔfj]T，yi(t)＝[ΔfiΔωi]T
wherein, Δ PciFor load reference deviation, Δ VqriFor doubly-fed wind generator rotor voltage deviation, Δ iqriFor the rotor current deviation of the doubly-fed wind generator,
tie line power deviation, Δ P, for region idiFor load disturbances,. DELTA.fiFrequency deviation, Δ f, for region ijFrequency deviation of region j, Δ ωiIs the speed deviation, delta P, of the doubly-fed wind generatorvi、ΔPmiAnd Δ PeiRespectively representing the deviation of the valve opening position instruction, the deviation of the output mechanical power of the steam turbine and the deviation of the output power of the doubly-fed wind driven generator, DiIs the ratio of percent change in load to percent change in frequency, MtiDoubly-fed wind generator inertia constant, R, for region iiFor adjustment of the difference coefficient, X2iFor the electrical conduction, X, of doubly-fed wind generators3i＝Lm/(Lm+Ls)，LmAnd LsMutual inductance coefficient of stator and rotor of doubly-fed wind generator and self-inductance coefficient of stator, IoptiAnd WoptiRespectively, to approximate the model to the optimal parameter of the actual system, TTiAnd TGiTime constants, T, of speed regulators and turbines, respectivelyijThe upper and lower marks i and j represent the areas i and j of the power system, w (t) is the external disturbance of the power system, and N is the area number of the power system;
the second step further comprises:
step S1, establishing an internal model to accurately track the reference input;
step S2, constructing a full-dimensional state observer to reconstruct the state of the controlled object;
step S3, establishing an expansion system of the controlled power system and the internal model, and optimally obtaining the feedback gain of the state feedback controller from the angle of minimum energy by using a linear quadratic form optimal regulation method;
and step S4, estimating the influence of the load disturbance of the power system and the random fluctuation of the wind speed on the output by using the interference estimator, acquiring an equivalent input interference estimation value and mapping the equivalent input interference estimation value to the input end of the power system.
2. The active interference suppression method for load frequency of electric power system as claimed in claim 1, wherein: in step S4, after the equivalent input interference estimation value obtained by the interference estimator is filtered by the low-pass filter to output the measurement noise, the measurement noise is combined with the state feedback control signal to obtain the control signals respectively input to the wind turbine generator and the conventional generator set, and the control signals are input to the input ends of the wind turbine generator and the conventional generator set.
3. The method as claimed in claim 2, wherein the internal model formula is:
wherein x isR(t) is a state variable, ARIs a system matrix, BRTo input the matrix, Δ yref(t) is the ideal output deviation, and the outputs of the power system are y (t), Δ yref(t)＝0。
4. A power system load frequency active interference suppression system comprises a state space model establishing unit, an internal model, a state feedback controller, a full-dimensional state observer, an interference estimator and a power system comprising a wind power plant, wherein the power system load frequency active interference suppression system establishes a state space model of a controlled object comprising the power system of the wind power plant by using the state space model establishing unit based on a load frequency control model, estimates the influence of the internal model, the state feedback controller, the full-dimensional state observer and the interference estimator on the load disturbance of the power system and the random fluctuation of the wind speed on the output based on an equivalent input interference idea, maps the estimated influence to the input end of the power system comprising the wind power plant, carries out reverse compensation on the disturbance, and realizes the active suppression on the frequency disturbance of the power system;
establishing the following state space model:
wherein the content of the first and second substances,
ui(t)＝[ΔPciΔVqri]T
wi(t)＝[ΔPdiΔTmiΔfj]T，yi(t)＝[ΔfiΔωi]T
wherein, Δ PciFor load reference deviation, Δ VqriFor doubly-fed wind generator rotor voltage deviation, Δ iqriFor the rotor current deviation of the doubly-fed wind generator,
tie line power deviation, Δ P, for region idiFor load disturbances,. DELTA.fiIs a regionFrequency deviation of field i, Δ fjFrequency deviation of region j, Δ ωiIs the speed deviation, delta P, of the doubly-fed wind generatorvi、ΔPmiAnd Δ PeiRespectively representing the deviation of the valve opening position instruction, the deviation of the output mechanical power of the steam turbine and the deviation of the output power of the doubly-fed wind driven generator, DiIs the ratio M of percent change in load to percent change in frequencytiDoubly-fed wind generator inertia constant, R, for region iiFor adjustment of the difference coefficient, X2iFor the electrical conduction, X, of doubly-fed wind generators3i＝Lm/(Lm+Ls)，LmAnd LsMutual inductance coefficient of stator and rotor of doubly-fed wind generator and self-inductance coefficient of stator, IoptiAnd WoptiRespectively, to approximate the model to the optimal parameter of the actual system, TTiAnd TGiTime constants, T, of speed regulators and turbines, respectivelyijThe upper and lower marks i and j represent the areas i and j of the power system, w (t) is the external disturbance of the power system, and N is the area number of the power system;
based on an equivalent input interference idea, estimating the influence of load disturbance and random fluctuation of wind speed on output of the power system by adopting an internal model, a state feedback controller, a full-dimensional state observer and an interference estimator, mapping the estimated influence to the input end of the power system containing the wind power plant, and performing reverse compensation on the disturbance to realize active suppression on frequency disturbance of the power system, wherein the active suppression specifically comprises the following steps:
step S1, establishing an internal model to accurately track the reference input;
step S2, constructing a full-dimensional state observer to reconstruct the state of the controlled object;
step S3, establishing an expansion system of the controlled power system and the internal model, and optimally obtaining the feedback gain of the state feedback controller from the angle of minimum energy by using a linear quadratic form optimal regulation method;
and step S4, estimating the influence of the load disturbance of the power system and the random fluctuation of the wind speed on the output by using the interference estimator, acquiring an equivalent input interference estimation value and mapping the equivalent input interference estimation value to the input end of the power system.
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