CN112636398B - Wind-fire-storage combined secondary frequency modulation method - Google Patents
Wind-fire-storage combined secondary frequency modulation method Download PDFInfo
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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
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
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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
- H02J3/381—Dispersed generators
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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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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses a wind-fire-storage combined secondary frequency modulation method, which considers the factors of inconsistency of modeling methods of a thermal power generating unit, a wind power station and an energy storage power station, uncertainty of secondary frequency modulation communication delay and the like, takes the wind power generating unit, the thermal power generating unit and the energy storage power station as regulation and control objects, describes system communication delay based on delay margin, takes a regional power grid meeting certain system robust performance indexes as a control target, takes robust H-infinity control as a basic controller design method, and designs secondary frequency control of the regional power grid; the method sets the robust performance index aiming at the regional power grid frequency problem after new energy grid connection, can effectively enhance the robust performance of the system frequency, reduces the frequency modulation problem caused by large-scale photovoltaic grid connection and load uncertainty fluctuation, and ensures the safe and stable operation of the power grid frequency.
Description
Technical Field
The invention relates to a wind-fire-storage combined secondary frequency modulation method, and belongs to the technical field of power grid frequency control.
Background
The state of the art and the problems that exist are described closest to the present invention.
The traditional secondary frequency modulation of the power system means that a generator set provides enough adjustable capacity and a certain adjusting rate, and the frequency is tracked in real time under the allowable adjusting deviation so as to meet the requirement of stable system frequency. The secondary frequency modulation can achieve the purpose of adjusting the frequency without difference, and can monitor and adjust the power of the tie line. With the continuous development of energy technology, the proportion of new energy, stored energy and other resources accessing a power grid gradually increases, and the frequency modulation situation of the power grid needs to be improved by effectively controlling and utilizing the new energy due to the change of frequency caused by a large amount of active power transmitted to the power grid. Aiming at the new energy participating in frequency modulation, single station level control is mainly used at present, automatic power generation control and local frequency signals of a power grid are used as the basis, control design is carried out through a local traditional classical control theory of the station, and the effects of realizing power distribution, reducing frequency deviation, improving power grid inertia, improving the safe and stable operation capability of the power grid and the like are achieved.
However, in the face of access of a large number of well-injection new energy stations and stored energy into a power grid, frequency control operation of the traditional power grid faces various more complex problems, the current secondary frequency modulation scheme generally only considers the use of a special communication line for signal transmission, and does not fully consider the problem that inevitable communication delay exists in secondary frequency modulation of a large number of frequency modulation resources such as new energy stations and stored energy along with the continuous promotion of electric power marketization, and the frequency control operation of the power grid is not favorable for stable frequency operation of the whole power grid when the frequency modulation resources participate in secondary frequency modulation of the power grid.
Disclosure of Invention
The technical problem is as follows: aiming at the defects of the prior art, the invention aims to solve the problems that various uncertain factors such as wind speed influence, frequent load fluctuation, communication delay and the like exist in the wind-fire-storage combined secondary frequency modulation, the fluctuation deviation of the power grid frequency is effectively reduced through a robust control theory, and the stable operation of the power grid frequency is ensured.
The technical scheme is as follows:
the invention provides an alternating current-direct current power distribution network optimized operation method considering voltage out-of-limit risks, which mainly comprises the following steps:
a wind-fire-storage combined secondary frequency modulation control method considering uncertainty delay comprises the following steps:
s1, establishing a frequency modulation model of a regional power grid including a wind power plant station, a thermal power generating unit, an energy storage power station and the like;
S2 calculating the delay margin of the whole system based on the direct method;
s3, designing a control gain parameter of wind, fire and storage combined frequency modulation based on the delay margin value and a linear matrix inequality method.
As a preferred scheme of the invention, the step of establishing the model for frequency modulation of the regional power grid including the wind power plant, the thermal power generating unit, the energy storage power station and the like is as follows:
1) wind power station model
The variable-speed wind turbine generator is adopted to participate in system frequency regulation, and a simplified model is expressed as follows:
in the formula, s represents a differential operator, Δ wriRepresenting the variation of the fan rotor speed, Δ q, in zone iiRepresenting the fan pitch angle variation, Deltau, of zone iWiRepresenting the control signal, Δ P, of the wind farm in zone iciFor zone i system control signals, alphaWiDistribution coefficient, N, for power signals of wind power station of region igiFor zone i Fan gearbox ratio, JriAnd JgiIs the inertia coefficient of the fan rotor and the generator in the region i and has Jti＝Jri+Ngi 2Jgi；
In the formula,. DELTA.wfiRepresenting the fan generator speed variation of the region i;
in the formula, TriIndicating zone i fan electromagnetic torque, TgiIndicating region i fan mechanical torque, KpiAnd KiiExpressing the proportional and integral coefficients, K, of the area i fan PI controllersciRepresents a correction coefficient;
2) thermal power plant model comprising
A speed regulator model:
In the formula,. DELTA.PgiFor the region i thermal power generating unit speed regulator valve position variation, TgiTime constant, Deltau, of the governor of a regional i thermal power unitGiFor control signals of thermal power generating units, alphaGiDistributing coefficient, R, for power signals of i thermal power generating units in regiongiThe droop coefficient of the thermal power generating unit is a region i;
the turbine model is as follows:
in the formula,. DELTA.PmiFor the variation of output power of regional thermal power generating units, TgiA thermal power unit turbine time constant of a region i;
3) energy storage power station model
The transfer function in the energy storage power station is equivalent to a first-order inertia link as follows:
in the formula: pBESSiOutputting active power variation, T, for regional i energy storage power stationBESSRepresenting the response time constant, Deltau, of the energy storage plantBiStoring power station control signals, alpha, for zone iBiDistributing coefficients for power signals of the energy storage power station;
the SOC of the energy storage battery reflects the running state and the regulation and control capability of the battery, the SOC of the energy storage unit is estimated by adopting an ampere-hour integration method, and the calculation formula is as follows:
in the formula: pBESSiOutputting active power for the energy storage power station of the region i, wherein the unit is kW; ecap，iRated capacity of an energy storage power station of a region i, wherein the unit is kWh, and h is a power loss coefficient of the energy storage power station;
4) interconnection line model
ΔACEi＝βiΔfi+ΔPtie,i
In the formula, Delta ACEiFor regional control errors, Δ Ptie,iTo tie line power, beta iIs a frequency deviation factor, TijInterconnection gain for the region i and the region j, and communication delay time for d;
5) regional power grid frequency response model
Rotational inertia and load model:
where M is the inertia coefficient of zone i, D is the damping coefficient of zone i, and Δ PdiThe load variation amount of the area i.
As a preferred scheme of the invention, the steps of determining the control objective function and the actual physical constraint of the regional power grid are as follows:
the regional power grid frequency control model comprising various regulation and control resources such as a wind power plant station, a thermal power generating unit, an energy storage power station and the like is expressed as a state space equation form as follows:
x(t)＝Ax(t)+Adx(t-τ)+Bu(t)+Bωω(t)
wherein x (t), x (t-t)i) Is the system overall state vector, u (t) is the system overall control vector, ω (t) is the system overall disturbance vector, A is the overall system matrixdA parameter matrix of the delay state of the whole system, B is a whole control matrix, BωAn integral disturbance matrix;
x(t)＝[x1(t) x2(t) … xn(t)]T
u(t)＝[u1(t) u2(t) … un(t)]T
ω(t)＝[ω1(t) ω2(t) … ωn(t)]T
B＝[B1 B2 … Bn]T
Bω＝[Bω1 Bω2 … Bωn]T
in the formula, xi(t) is the region i System State vector, ui(t) is the region i System control vector, ωi(t) is the system disturbance vector of area i, AiiIs a system matrix of area i, AijSystem interconnection parameter matrix for zone i and zone j, BiAs an overall control matrix, BωiAn integral disturbance matrix; the vectors contain the following specific quantities:
xi(t)＝[Δωri Δωfi Δθi ΔPmi ΔPgi ΔPBESSi ΔSOCi Δfi ∫ΔACEi ΔPtie,i]T
ui(t)＝[ΔuWi ΔuGi ΔuBi]T
ωi(t)＝[ΔPdi Δvmi]T
The characteristic equation of the overall system is then as follows:
from the general stability theory of the dynamic system, it can be known that all roots of the characteristic equation must be positioned in the left half of the complex plane to enable the system to be asymptotically stable; due to the exponential transcendental terms, these characteristic equations may have an infinite number of roots; however, for stability assessment, knowledge of all sources is not required; when the characteristic polynomial has root on the virtual axis, the delay margin value tau is calculated*It is sufficient;
take two-zone interconnected power systems as an example:
Δ(-s,τ)＝a0(-s)+a1(-s)eτs+a2(-s)e2τs＝0
defining a new characteristic equation:
Δ(1)(s,τ)＝a0(-s)Δ(s,τ)-a2(s)e-2τsΔ(-s,τ)
Δ(1)(s,τ)＝[a0(-s)a0(s)-a2(s)a2(-s)]+[a0(-s)a1(s)-a2(s)a1(-s)]e-τs
then s is given as jwcIs the root of the new characteristic equation of the following formula:
in the formula,
establishing a new characteristic equation:
changing s to jwcPut into the above formula and make it equal to zero, have
The system delay margin is
As a preferred scheme of the invention, the control solving control parameter of wind-fire-storage combined frequency modulation is designed based on a linear matrix inequality method, and the method comprises the following steps:
the system model is expressed in the form of the following in consideration of the system control output and the initial condition
Wherein z (t) is a control output vector, C is a state output matrix, DωFor perturbing the output matrix, D is the control output matrix, CdFor a delayed state output matrix, the initial condition φ (t) is at t ∈ - τ *，0]Is a continuous micro-initiatable function;
for a differentiable function with uncertain delay t as a time-varying one, satisfy
In the formula, wherein*For the delay margin value, h, calculated by direct method1And μ is a constant; h is1May be non-zero;
for a given scalar γ >0, the performance of the system is defined as:
the control of the invention is designed for a memory-free state feedback controller based on H infinity control, and the value of the control gain K is found, wherein K belongs to Rm×nI.e. controller parameters, there are:
u(t)＝Kx(t)
and for closed loop systems
In that
Is progressively stable under conditions and e L for all non-zero ω (t) ∈ L2[0, ∞) and given gamma>0 at initial conditions
Are all provided with J (w)<0；
The controller gain parameter K is thus designed as follows:
for a given scalar τ*≥h1≥0，μ，γ>0, if there is a matrix L, Ri≥0，i＝1,2,3，YjNot less than 0, and Wj>0, j-1, 2, matrix M of any suitable dimensionjJ is 1,2,3, and the matrix V satisfies the following matrix inequality:
wherein,
Ξ2＝[M1 M3-M1-M2 M2 -M3 0]
Ξ3＝[AL+BV AdL 0 0 Bω]
Ξ4＝[CL 0 0 0 Dω]
Ξ5＝[0 CdL 0 0 0]
Ξ6＝[DV 0 0 0 0]
to this end, the system is progressively stable and satisfies J (w)<0 for all nonzero ω (t) e L2[0, ∞) and given initial conditions
Controlling gain parameter as K ═ VL-1I.e. u (t) ═ VL-1And x (t) is an H-infinity controller of wind-fire-storage combined secondary frequency modulation.
Has the advantages that:
the invention provides a thermal power and energy storage combined secondary frequency modulation method considering uncertainty delay, aiming at system frequency adjustment such as uncertainty fluctuation of new energy station access and load power and communication delay existing in the process of new energy participating in secondary frequency modulation, and the like, and having the following advantages:
1) After the wind power station is connected into a power grid, although active power output can be carried out to participate in frequency adjustment, the active power cannot be stably output due to the influence of wind speed uncertainty.
2) The invention provides a delay margin calculation technology, which can directly settle delay margins through a characteristic equation based on a state space equation description system and can effectively avoid a complex analysis and solution process;
3) the method carries out control design based on a robust control theory and solves the control parameters based on the linear matrix inequality, thereby reducing the solving complexity and ensuring the optimal control parameters.
Drawings
FIG. 1 is a flow chart of wind-fire-storage combined secondary frequency modulation control design;
FIG. 2 is a wind-fire-storage combined frequency modulation topological diagram;
FIG. 3 is a graph showing the frequency change before and after zone 1 control;
FIG. 4 is a graph showing the frequency change before and after the control of zone 2;
Detailed Description
Example (b):
as shown in the figure, a wind-fire-storage combined secondary frequency modulation control method considering uncertainty delay comprises the following steps:
s1 frequency modulation model of regional power grid including wind power plant, thermal power generating unit, energy storage power station and the like is established
1) Wind power station model
The variable-speed wind turbine generator is adopted to participate in system frequency regulation, and a simplified model is expressed as follows:
in the formula, s represents a differential operator,. DELTA.wriRepresenting the variation of the fan rotor speed, Δ q, in the region iiRepresenting the fan pitch angle variation, Deltau, of zone iWiRepresenting the control signal, Δ P, of the wind farm in zone iciFor zone i system control signals, alphaWiDistribution coefficient, N, for power signals of wind power station of region igiFor zone i Fan gearbox ratio, JriAnd JgiIs the inertia coefficient of the fan rotor and the generator in the region i and has Jti＝Jri+Ngi 2Jgi。
In the formula,. DELTA.wfiAnd indicating the fan generator speed variation of the region i.
In the formula, TriIndicating zone i fan electromagnetic torque, TgiIndicating region i fan mechanical torque, KpiAnd KiiExpressing the proportional and integral coefficients, K, of the area i fan PI controllersciIndicating the correction factor.
2) Thermal power plant model comprising
A speed regulator model:
in the formula,. DELTA.PgiRegulating valve position variation, T, of thermal power generating unit speed regulator for region igiTime constant, Deltau, of governor for regional i thermal power generating unitGiFor control signals of thermal power generating units, alphaGiDistributing coefficient, R, for power signals of i thermal power generating units in regiongiAnd the droop coefficient is the droop coefficient of the thermal power generating unit in the region i.
The turbine model is as follows:
in the formula,. DELTA.PmiFor the variation of output power of regional thermal power generating units, T giIs the turbine time constant of the regional i thermal power generating unit.
3) Energy storage power station model
The transfer function in the energy storage power station is equivalent to a first-order inertia link as follows:
in the formula: pBESSiOutputting active power variation, T, for regional i energy storage power stationBESSRepresenting the response time constant, Deltau, of the energy storage plantBiStoring power station control signals, alpha, for zone iBiAnd distributing coefficients for power signals of the energy storage power station.
The SOC of the energy storage battery reflects the running state and the regulation and control capability of the battery, the SOC of the energy storage unit is estimated by adopting an ampere-hour integration method, and the calculation formula is as follows:
in the formula: pBESSiOutputting active power for the energy storage power station of the region i, wherein the unit is kW; ecap，iRated capacity of energy storage power station for region iThe unit is kWh, and h is the power loss coefficient of the energy storage power station.
4) Interconnection line model
ΔACEi＝βiΔfi+ΔPtie,i
In the formula, Delta ACEiFor regional control errors, Δ Ptie,iTo tie line power, betaiAs a frequency deviation factor, TijThe interconnect gain for zone i and zone j, and d the communication delay time.
5) Regional power grid frequency response model
Rotational inertia and load model:
where M is the inertia coefficient of zone i, D is the damping coefficient of zone i, and Δ PdiThe load variation amount in the area i.
S2 calculating integral system delay margin based on direct method
The regional power grid frequency control model comprising various regulation and control resources such as a wind power plant station, a thermal power generating unit, an energy storage power station and the like is expressed as a state space equation form as follows:
x(t)＝Ax(t)+Adx(t-τ)+Bu(t)+Bωω(t)
In the formula, x (t), x (t-t)i) Is the system overall state vector, u (t) is the system overall control vector, ω (t) is the system overall disturbance vector, A is the overall system matrix, AdA parameter matrix which is the delay state of the whole system, B is a whole control matrix, BωIs an overall perturbation matrix.
x(t)＝[x1(t) x2(t) … xn(t)]T
u(t)＝[u1(t) u2(t) … un(t)]T
ω(t)＝[ω1(t) ω2(t) … ωn(t)]T
B＝[B1 B2 … Bn]T
Bω＝[Bω1 Bω2 … Bωn]T
In the formula, xi(t) is the region i System State vector, ui(t) is the zone i System control vector, ωi(t) is the system disturbance vector of area i, AiiIs a region i system matrix, AijSystem interconnection parameter matrix for zone i and zone j, BiAs an overall control matrix, BωiIs an overall perturbation matrix. The vectors contain the following specific quantities:
xi(t)＝[Δωri Δωfi Δθi ΔPmi ΔPgi ΔPBESSi ΔSOCi Δfi ∫ΔACEi ΔPtie,i]T
ui(t)＝[ΔuWi ΔuGi ΔuBi]T
ωi(t)＝[ΔPdi Δvmi]T
the characteristic equation of the overall system is as follows:
from general stability theory of the dynamical system, it is known that all roots of the characteristic equation must be located in the left half of the complex plane to asymptotically stabilize the system. These characteristic equations may be infinite due to exponential transcendental termsAnd (4) root. However, for stability assessment, knowledge of all sources is not required. When the characteristic polynomial has root (if any) on the virtual axis, the delay margin value tau is calculated*It is sufficient.
Take two-zone interconnected power systems as an example:
Δ(-s,τ)＝a0(-s)+a1(-s)eτs+a2(-s)e2τs＝0
defining a new characteristic equation:
Δ(1)(s,τ)＝a0(-s)Δ(s,τ)-a2(s)e-2τsΔ(-s,τ)
Δ(1)(s,τ)＝[a0(-s)a0(s)-a2(s)a2(-s)]+[a0(-s)a1(s)-a2(s)a1(-s)]e-τs
then s is given as jwcIs the root of the new characteristic equation of the following formula:
In the formula,
establishing a new characteristic equation:
changing s to jwcSubstituted into the above formula and make it equal to zero, have
Then the system delay margin is
S3 design wind, fire and storage combined frequency modulation control gain parameter based on delay margin value and linear matrix inequality method
The system model is expressed in the form of the following in consideration of the system control output and the initial condition
Wherein z (t) is a control output vector, C is a state output matrix, DωFor perturbing the output matrix, D for controlling the output matrix, CdFor a delayed state output matrix, the initial condition φ (t) is at t ∈ - τ*，0]Is a continuously differentiable initial function.
For a differentiable function with uncertain delay t as a time-varying one, satisfy
In the formula, wherein*For the delay margin value, h, calculated by direct method1And μ is a constant. h is1May be non-zero.
For a given scalar γ >0, the performance of the system is defined as:
the control of the present invention is based on a memoryless state feedback controller design of H infinity control, finding the value of the control gain K,K∈Rm×ni.e. controller parameters, there are:
u(t)＝Kx(t)
and for closed loop systems
In that
Is progressively stable under conditions and e L for all non-zero ω (t) ∈ L2[0, ∞) and given gamma>0 at initial conditions
Are all provided with J (w)<0。
The controller gain parameter K is thus designed as follows:
For a given scalar τ*≥h1≥0，μ，γ>0, if there is a matrix L, Ri≥0，i＝1,2,3，YjNot less than 0, and Wj>0, j-1, 2, matrix M of any suitable dimensionjJ is 1,2,3, and the matrix V satisfies the following matrix inequality:
wherein,
Ξ2＝[M1 M3-M1-M2 M2 -M3 0]
Ξ3＝[AL+BV AdL 0 0 Bω]
Ξ4＝[CL 0 0 0 Dω]
Ξ5＝[0 CdL 0 0 0]
Ξ6＝[DV 0 0 0 0]
to this end, the system is progressively stable and satisfies J (w)<0 for all nonzero ω (t) e L2[0, ∞) and given initial conditions
Controlling gain parameter as K ═ VL-1I.e. u (t) ═ VL-1And x (t) is an H-infinity controller of wind-fire-storage combined secondary frequency modulation.
The invention takes an improved IEEE three-machine nine-node power system as an example, the equipment and topology parameters are as follows, and the specific topology is as shown in FIG. 2. The scheduling scheme of the present invention was programmed on MATLAB and simulated using SIMULINK.
Device and topology parameters:
generator parameters:
g1:247.5MVA, 16.5kV, power factor 1, water turbine (saint-Pole), 180rpm, x ═ 0.146, x ═ 0.0608, ddx ═ 0.0969, x ═ 0.0969, x ═ 0.0336, T ═ 8.96s, T ═ 0s, H ═ 23.64s, D ═ 0 qqqqld 0q0
192MVA, 18kV, power factor 0.85, steam turbine (Round-Rotor), 3600rpm, x 0.8958, x ' 0.1198, ddx 0.8645, x ' 0.1969, x ' 0.0521, T ' 6s, T ' 0.535s, H6.4 s, D0 qqqld 0q0
128MVA, 13.8kV, power factor 0.85, turboset (Round-Rotor), 3600rpm, x 1.3125, x 0.1813, ddx 1.2578, x 0.25, x 0.0742, T5.89 s, T0.6 s, H3.01 s, D0 qqqld 0q0
Transformer parameters:
T1:16.5/230kV，X＝0.0576；T2:18/230kV，X＝0.0625；T3:13.8/230kV，X＝0.0586TTT
line parameters:
Line1:Z＝0.01+j0.085，B/2＝j0.088；Line2:Z＝0.032+j0.161，B/2＝j0.153；
Line3:Z＝0.017+j0.092，B/2＝j0.079；Line4:Z＝0.039+j0.17，B/2＝j0.179；
Line5:Z＝0.0085+j0.072，B/2＝j0.0745；Line6:Z＝0.0119+j0.1008，B/2＝j0.1045
loads LumpA 125+ j50MVA, LumpB 90+ j30MVA, LumpC 100+ j35MVA
Setting a generator G1 as a balance node (Slack) of a system, setting a voltage amplitude to be 1.04pu and a voltage reference phase angle to be 0; setting G2 and G3 as PV nodes, setting the active power output to be 1.63pu and 0.85pu respectively, and setting the voltage amplitude to be 1.025 pu.
The installed capacity of the wind power station is 49.5MW, and the total capacity of the energy storage power station is 20 MW.
The invention provides a thermal power and energy storage combined secondary frequency modulation method considering uncertainty delay, aiming at system frequency adjustment of uncertainty fluctuation of new energy station access and load power, communication delay existing in the process of new energy participating in secondary frequency modulation and the like, and the method has the following advantages:
1) after the wind power station is connected to a power grid, although active power output can participate in frequency adjustment, the active power cannot be stably output due to the influence of wind speed uncertainty.
2) The invention provides a delay margin calculation technology, which can directly settle delay margins through a characteristic equation based on a state space equation description system and can effectively avoid a complex analysis and solution process;
3) The method carries out control design based on a robust control theory and solves the control parameters based on the linear matrix inequality, thereby reducing the solving complexity and ensuring the optimal control parameters.
Claims (1)
1. A wind, fire and storage combined secondary frequency modulation control method considering uncertainty delay is characterized by comprising the following steps of:
s1, establishing a frequency modulation model of a regional power grid including a wind power station, a thermal power generating unit and an energy storage power station;
s2, calculating the delay margin of the whole system based on a direct method;
s3, designing a control gain parameter of wind, fire and storage combined frequency modulation based on a delay marginal value and a linear matrix inequality method;
the method for establishing the model for the frequency modulation of the regional power grid of the wind power station, the thermal power generating unit and the energy storage power station comprises the following steps:
1) wind power station model
The variable-speed wind turbine generator is adopted to participate in system frequency regulation, and a simplified model is expressed as follows:
in the formula, s represents a differential operator, Δ wriRepresenting variation of fan rotor speed, Delta theta, in zone iiRepresenting the variation of fan pitch angle, Δ q, in zone iiRepresenting the fan pitch angle variation, Deltau, of zone iWiRepresenting the control signal, Δ P, of the wind farm in zone iciFor zone i system control signals, alphaWiDistribution coefficient, N, for power signals of wind power station of region i giFor zone i Fan gearbox ratio, JtiArea i blower integrated inertia coefficient, JriAnd JgiIs the inertia coefficient of the fan rotor and the generator in the region i, and has
In the formula,. DELTA.wfiRepresenting the fan generator speed variation of the region i;
in the formula, TriIndicating zone i fan electromagnetic torque, TgiIndicating region i fan mechanical torque, KpiAnd KiiExpressing the proportional and integral coefficients, K, of the area i fan PI controllersciRepresents a correction coefficient;
2) thermal power plant model comprising
A speed regulator model:
in the formula,. DELTA.PgiRegulating valve position variation, T, of thermal power generating unit speed regulator for region ieiTime constant, Deltau, of governor for regional i thermal power generating unitGiFor control signals of thermal power generating units, alphaGiDistributing coefficient, R, for power signals of i thermal power generating units in regiongiThe droop coefficient of the thermal power generating unit is a region i;
the turbine model is as follows:
in the formula,. DELTA.PmiFor the variation of output power of regional thermal power generating units, TchiA thermal power unit turbine time constant of a region i;
3) energy storage power station model
The transfer function in the energy storage power station is equivalent to a first-order inertia link as follows:
in the formula: pBESSiOutputting active power variation, T, for regional i energy storage power stationBESSRepresenting the response time constant, Deltau, of the energy storage plantBiStoring power station control signals, alpha, for zone iBiFor power signal distribution in energy storage power stations A coefficient;
the state of charge of the energy storage battery reflects the running state and the regulation and control capacity of the battery, the SOC of the energy storage unit is estimated by adopting an ampere-hour integration method, and the calculation formula is as follows:
in the formula: p isBESSiOutputting active power for an energy storage power station of the region i, wherein the unit is kW; ecap，iThe rated capacity of the energy storage power station of the region i is represented by kWh, h is the power loss coefficient of the energy storage power station, eta is the power loss coefficient of the energy storage power station, and SOC is0iThe initial state of charge of the energy storage power station for the region i;
4) interconnection line model
ΔACEi＝βiΔfi+ΔPtie,i
In the formula, Delta ACEiFor regional control errors, Δ Ptie,iTo tie line power, betaiAs a frequency deviation factor, TijInterconnection gain for the region i and the region j, and communication delay time for d;
5) regional power grid frequency response model
Rotational inertia and load model:
where M is the inertia coefficient of zone i, D is the damping coefficient of zone i, and Δ PdiLoad variation of the area i;
the steps of determining the control objective function and the actual physical constraint of the regional power grid are as follows:
the method comprises the following steps of representing a regional power grid frequency control model containing various regulation and control resources of a wind power station, a thermal power generating unit and an energy storage power station as a state space equation form as follows:
x(t)＝Ax(t)+Adx(t-τ)+Bu(t)+Bωω(t)
wherein x (t), x (t-t)i) Is the system overall state vector, u (t) is the system overall control vector, ω (t) is the system overall disturbance vector, A is the overall system matrix dA parameter matrix which is the delay state of the whole system, B is a whole control matrix, BωIs an integral disturbance matrix;
x(t)＝[x1(t) x2(t)…xn(t)]T
u(t)＝[u1(t) u2(t)…un(t)]T
ω(t)＝[ω1(t) ω2(t)…ωn(t)]T
B＝[B1 B2…Bn]T
Bω＝[Bω1 Bω2…Bωn]T
in the formula, xi(t) is the region i System State vector, ui(t) is the region i System control vector, ωi(t) is the system disturbance vector of area i, AiiIs a region i system matrix, AijSystem interconnection parameter matrix for zone i and zone j, BiAs an overall control matrix, BωiAn integral disturbance matrix; the vectors contain the following specific quantities:
xi(t)＝[Δωri Δωfi Δθi ΔPmi ΔPgi ΔPBESSi ΔSOCi Δfi ∫ΔACEi ΔPtie,i]T
ui(t)＝[ΔuWi ΔuGi ΔuBi]T
ωi(t)＝[ΔPdi Δvmi]T
the characteristic equation of the overall system is as follows:
from the general stability theory of the dynamic system, it can be known that all roots of the characteristic equation must be positioned in the left half of the complex plane to enable the system to be asymptotically stable; due to exponential transcendental terms, these characteristic equations have an infinite number of roots; however, for stability assessment, knowledge of all sources is not required; when the characteristic polynomial has root on the virtual axis, the delay margin value tau is calculated*It is sufficient;
take two-zone interconnected power systems as an example:
Δ(-s,τ)＝a0(-s)+a1(-s)eτs+a2(-s)e2τs＝0
defining a new characteristic equation:
Δ(1)(s,τ)＝a0(-s)Δ(s,τ)-a2(s)e-2τsΔ(-s,τ)
Δ(1)(s,τ)＝[a0(-s)a0(s)-a2(s)a2(-s)]+[a0(-s)a1(s)-a2(s)a1(-s)]e-τs
then s is given as jwcIs the root of the new characteristic equation of the following formula:
in the formula,
establishing a new characteristic equation:
changing s to jwcPut into the above formula and make it equal to zero, have
The system delay margin is
A control solving control parameter of wind-fire-storage combined frequency modulation is designed based on a linear matrix inequality method, and the method comprises the following steps:
The system model is expressed in the form of the following in consideration of the system control output and the initial condition
Wherein z (t) is a control output vector, C is a state output matrix, DωFor perturbing the output matrix, D is the control output matrix, CdFor a delayed state output matrix, the initial condition φ (t) is at t ∈ - τ*，0]Is a continuous micro-initiatable function;
for a differentiable function with uncertain delay t as a time-varying one, satisfy
In the formula, wherein*For the delay margin value, h, calculated by direct method1And μ is a constant; h is1Is non-zero;
for a given scalar γ >0, the performance of the system is defined as:
a memoryless state feedback controller design with control based on H infinity finds the value of the control gain K, K ∈ Rm×nI.e. controller parameters, there are:
u(t)＝Kx(t)
and for closed loop systems
In that
Is progressively stable under conditions and e L for all non-zero ω (t) ∈ L2[0, ∞) and given gamma>0 in the initial condition
Are all provided with J (w)<0；
The controller gain parameter K is thus designed as follows:
for a given scalar τ*≥h1≥0，μ，γ>0, if there is a matrix L, Ri≥0，i＝1,2,3，YjNot less than 0, and Wj>0, j-1, 2, matrix M of any suitable dimensionjJ is 1,2,3, and the matrix V satisfies the following matrix inequality:
wherein,
Ξ2＝[M1 M3-M1-M2 M2 -M3 0]
Ξ3＝[AL+BV AdL 0 0 Bω]
Ξ4＝[CL 0 0 0 Dω]
Ξ5＝[0 CdL 0 0 0]
Ξ6＝[DV 0 0 0 0]
to this end, the system is progressively stable and satisfies J (w) <0 for all nonzero ω (t) e L2[0, ∞) and given initial conditions
Controlling gain parameter as K ═ VL-1I.e. u (t) ═ VL-1And x (t) is an H-infinity controller of wind-fire-storage combined secondary frequency modulation.
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| CN111864813A (en) * | 2020-06-23 | 2020-10-30 | 国网辽宁省电力有限公司电力科学研究院 | Wind/thermal power combined frequency control method based on virtual weight coefficient |
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| CN111864813A (en) * | 2020-06-23 | 2020-10-30 | 国网辽宁省电力有限公司电力科学研究院 | Wind/thermal power combined frequency control method based on virtual weight coefficient |
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