CN116470528A - Multi-time scale auxiliary frequency modulation method for regional power grid optical storage station - Google Patents
Multi-time scale auxiliary frequency modulation method for regional power grid optical storage station 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
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
- H02J3/241—The oscillation concerning frequency
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- H—ELECTRICITY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
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- 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
- H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
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- 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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
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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
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
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Abstract
The invention discloses a multi-time scale auxiliary frequency modulation method for an optical storage station of a regional power grid, which comprises four parts, namely power distribution of frequency response of a plurality of photovoltaic units in the optical storage station, power distribution of a plurality of energy storage units in the optical storage station, inertial support and primary frequency response of a layer of the optical storage station, and cooperative participation of the multi-optical storage station in secondary frequency adjustment of the regional power grid; the method is characterized in that a photovoltaic field station integral inertia supporting and primary frequency modulation control method based on virtual synchronous generator control is designed for an optical storage field station comprising a plurality of photovoltaic units and energy storage units, and a secondary frequency modulation method based on robust control is established for a regional power grid comprising a plurality of optical storage field stations, so that the secondary frequency adjustment of the regional power grid in which the multi-optical storage field station is cooperatively participated is realized. The invention realizes auxiliary inertia and power support through primary and secondary frequency modulation control establishment, power distribution and the like, and can cope with various frequency fluctuation events in a power grid.
Description
Technical Field
The invention relates to the technical field of power grid regulation and control, in particular to an auxiliary frequency modulation method for regional power grid optical storage stations considering multiple time scales.
Background
In recent years, with the increasing problems of global energy crisis, environmental pollution and the like, the development and utilization of renewable energy sources are attracting attention. The photovoltaic power generation is used as a high-efficiency and high-quality renewable energy source, is more favored, and is also widely applied.
However, as more and more traditional synchronous generators are replaced by renewable energy sources accessed through power electronic equipment, the overall inertia of a power system is reduced, the frequency stability of the system is seriously endangered, and the safety and the reliability of power supply are further influenced. In view of the above problems, some areas have been out of the office and related policies, and new energy stations are required to have flexibility adjusting capabilities such as inertial support and frequency response. Therefore, for an optical storage station accessing the power grid, an auxiliary frequency modulation strategy needs to be designed to solve the above problems.
At present, the technical scheme aiming at the participation of new energy sources in frequency response mainly comprises single-type new energy sources and single time scale frequency modulation. For example, a part of researchers respectively propose various control schemes of the new energy unit such as photovoltaic unit, wind power unit, energy storage unit and the like which participate in inertial support, primary frequency modulation and secondary frequency modulation aiming at the cooperation of the new energy unit and the traditional unit. However, the regulation object of the technical scheme is single, so that the method is difficult to be applied to a system with multiple new energy sources coexisting at present. Meanwhile, most schemes only pay attention to frequency adjustment of a certain time scale, and the coordination and cooperation of frequency response of each time scale are ignored. Based on the basis of the technology and the existing problems, the invention aims to provide an auxiliary frequency modulation strategy for the multi-type new energy and multi-time scale optical storage station, so that multi-source multi-time scale frequency support is realized, and the problems of aggravation and out-of-limit of regional power grid frequency fluctuation under high-permeability of the new energy are effectively alleviated.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides an auxiliary frequency modulation method for the regional power grid optical storage station taking into account multiple time scales, and the coordinated cooperation of a photovoltaic unit and an energy storage unit in the optical storage station and the cooperative control between the traditional thermal power unit and the optical storage station are used for realizing inertial support and frequency adjustment of the system and inhibiting the frequency fluctuation of the regional system.
The invention adopts the following technical scheme. The auxiliary frequency modulation method for the regional power grid optical storage station comprises four parts, namely power distribution of frequency response of a plurality of photovoltaic units in the optical storage station, power distribution of a plurality of energy storage units in the optical storage station, inertial support and primary frequency response of an optical storage station layer, and cooperative participation of the multi-optical storage station in secondary frequency adjustment of the regional power grid; in the frequency modulation control process, instructions are sequentially issued from an upper layer to a lower layer, secondary frequency adjustment of the multi-optical storage station cooperative participation regional power grid is firstly carried out, then inertial support and primary frequency response of the optical storage station layer are carried out, and finally power distribution of frequency response of a multi-photovoltaic unit in the optical storage station and power distribution of a multi-energy storage unit in the optical storage station are carried out;
the inertial support and primary frequency response of the optical storage station level are: for an optical storage station comprising a plurality of photovoltaic units and energy storage units, taking all the photovoltaic units and the energy storage units in the optical storage station as a whole, designing a photovoltaic station integral inertia supporting and primary frequency modulation control method based on virtual synchronous generator control, and expressing a frequency control model of an ith optical storage station as follows:
wherein: k (k) p,i The integral active droop coefficient of the ith optical storage station; j (J) i Virtual inertia for the ith optical storage station; omega i The angular velocity at the point of the ith optical storage station; omega n,i An i-th optical storage station angular velocity reference value; d (D) i The damping coefficient of the ith optical storage station; ΔP i The active power adjustment quantity is the whole active power adjustment quantity of the optical storage station, and t is time.
Further preferably, the matching method of the photovoltaic unit and the energy storage unit in the optical storage station during primary frequency modulation is as follows:
wherein: ΔP PV,i For the total photovoltaic active adjustment quantity of the ith optical storage station, delta P BESS,i For the total energy storage regulating quantity P in the ith optical storage station prc,i For the photovoltaic active standby capacity, delta P, in the ith optical storage station at the current moment i And (5) the integral active adjustment quantity of the ith optical storage station.
Further preferably, a robust control-based secondary frequency modulation method is established for a regional power grid comprising a plurality of optical storage stations, so that the cooperation participation of the multiple optical storage stations in the secondary frequency adjustment of the regional power grid is realized:
the state space model for controlling the secondary frequency of the regional power grid of the thermal power generating unit and the optical storage station is established as follows:
in the method, in the process of the invention,the variable quantity of the state variable is z (t) is an output variable, u (t) is a control variable, w (t) is a disturbance variable, and the matrix x of the state variable T ＝[Δf,ΔACE,ΔP m ,ΔP g ,ΔP c,g ,ΔP PV_BESS,i ,ΔP c,PV,i ]Matrix w of disturbance variables T ＝[ΔP PV,i ,ΔP L ]Matrix u of control variables T ＝[ΔP c,g ,ΔP c,PV,i ]Where i=1, 2, …, n; a is a coefficient matrix of state variables, B u Coefficient matrix for control variable, B w The coefficient matrix is the disturbance variable, and C is the coefficient matrix of the output variable; Δf is the regional power grid frequency deviation, ΔACE is the regional frequency deviation signal, ΔP m Is the output power variation quantity delta P of the thermal power unit g Is the valve variable quantity delta P of the thermal power machine speed regulator c,g For the secondary frequency modulation control input of the speed regulator, delta P PV_BESS,i For the ith optical storage stationChange in active output, ΔP c,PV,i For the second FM control input of the ith optical storage station, deltaP PV,i For the total photovoltaic active adjustment quantity of the ith optical storage station, delta P L Is the load deviation amount;
design based on robust H ∞ Controlled system secondary frequency modulation controller u(s) =k(s) y(s); by solving the following optimization problems and searching the optimal solution meeting the constraint, the optimal robust H of the regional power grid can be obtained ∞ The optimal control rate of the feedback control of the controller;
minζ 2
s.t.
X＞0
wherein: zeta is H ∞ Performance index of the controller; i is an identity matrix, K is an optimal control rate of feedback control, X, W is a symmetrical positive definite matrix in the solving process, and T represents transposition.
Further preferably, the power distribution of the frequency response of the multiple photovoltaic units in the optical storage station is as follows: aiming at the photovoltaic units participating in auxiliary frequency modulation in the photovoltaic storage station, a droop control strategy of the photovoltaic unit inverter is designed according to a direct current side control method of the photovoltaic units, so that the active frequency modulation capability of each photovoltaic unit in the photovoltaic storage station is fully exerted, the remaining adjustable capacity of each photovoltaic unit is ensured to be consistent, a power distribution method of frequency response of multiple photovoltaic units in the photovoltaic storage station is designed, and frequency tracking of a single unit level of the photovoltaic units is realized.
Enabling a part of photovoltaic units in the optical storage station to work in a load shedding control mode, enabling the operating points of the photovoltaic units to deviate from the maximum power point, and reserving a certain active standby capacity for participating in frequency modulation; the photovoltaic unit inverter participating in the frequency response can adopt PQ control (constant power control) to realize the goal of participating in primary frequency modulation of the power grid by tracking external instructions; establishing an active distribution weight coefficient alpha of a photovoltaic unit l l The following are provided:
wherein: l is the number of the photovoltaic unit accessed in the optical storage station, delta P PV.i The photovoltaic active power total adjustment quantity of the ith optical storage station; alpha l The weight coefficient is distributed for the active power of the photovoltaic unit l, n is the number of the photovoltaic units, and delta P is the number of the photovoltaic units up,l Active power surplus which can be increased for the photovoltaic unit l; ΔP down,l Active power surplus capable of being reduced for the photovoltaic unit l; reference value P of active power output by photovoltaic unit l in distributed load shedding control mode prc,ref,l The method comprises the following steps:
P prc,ref,l ＝P e,l +α l ·ΔP PV.i 。
wherein: p (P) e,l The active output value of the photovoltaic unit l at the current moment.
Further preferably, the power distribution of the multiple energy storage units in the optical storage station: aiming at the energy storage units participating in auxiliary frequency modulation in the optical storage station, according to the control method of the energy storage inverter of the energy storage units participating in frequency modulation, aiming at keeping the charge state of the energy storage units at 50% and reducing the action times of the energy storage units, a power distribution scheme of a plurality of energy storage units in the optical storage station is formulated, and the power tracking of the energy storage units in the optical storage station is realized.
Further preferably, when power distribution of multiple energy storage units in the optical storage station is performed, an energy storage unit weight distribution strategy is designed based on a fuzzy algorithm: when the energy storage discharges, the energy storage unit with high charge state has high discharge priority, namely the discharge weight is heavy, and the weight of the energy storage unit is reduced along with the reduction of the charge state; when the energy storage unit is charged, the energy storage unit with a low charge state has a high charging priority, and the weight thereof decreases with the increase of the charge state.
Compared with the prior art, the invention comprehensively considers the synergistic effect of the participation of the multi-type frequency modulation resources (photovoltaic and energy storage) in the regional power grid under the high penetration of the new energy, and designs the control strategy and the power distribution scheme of the participation of the frequency modulation resources in the frequency modulation in a targeted manner. Meanwhile, the invention also considers different time scales, designs a comprehensive control scheme aiming at the optical storage station from three time scales of inertial support, primary frequency modulation and secondary frequency modulation, is more complete compared with the prior art, is closer to practical application, and has higher reference value.
According to the invention, the multi-time-scale frequency response characteristics of the optical storage station, such as inertia support, primary frequency modulation and secondary frequency modulation, are comprehensively considered, auxiliary inertia and power support are realized through the establishment of the primary frequency modulation controller and the secondary frequency modulation controller, the power distribution and the like, and various frequency fluctuation events in a power grid can be dealt with. Therefore, the invention aims to provide a multi-time scale auxiliary frequency modulation method for an optical storage station of a regional power grid, which is suitable for solving the problems of aggravation of regional power grid frequency fluctuation and out-of-limit under high-permeability of new energy.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the description of the embodiments will be briefly described below. Wherein:
FIG. 1 is a schematic diagram of a frame control structure of a multi-time scale auxiliary frequency modulation method for an optical storage station of a regional power grid;
fig. 2 is a schematic diagram of SOC division of energy storage units in a method for distributing power of multiple energy storage units in an optical storage station according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. The embodiments described herein are merely some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art without inventive faculty, are within the scope of the invention, based on the spirit of the invention.
The invention provides an auxiliary frequency modulation method for an optical storage station of a regional power grid, which takes multiple time scales into consideration. In the frequency modulation control process, as shown in fig. 1, instructions are sequentially issued from an upper layer to a lower layer, secondary frequency adjustment of the multi-optical storage station cooperative participation regional power grid is firstly carried out, then inertial support and primary frequency response of the optical storage station layer are carried out, and finally power distribution of frequency response of the multi-photovoltaic unit in the optical storage station and power distribution of the multi-energy storage unit in the optical storage station are carried out. In the hierarchical design process, a power distribution method of frequency response of a plurality of photovoltaic units in an optical storage station is designed firstly, and then a power distribution scheme of a plurality of energy storage units in the optical storage station is prepared; the integral control method of the optical storage station based on the virtual synchronous generator control is designed, so that inertial support and primary frequency response of the optical storage station layer are realized; and finally, establishing a secondary frequency modulation method based on robust control, and realizing the cooperative participation of the multi-optical storage station in the secondary frequency adjustment of the regional power grid.
According to the photovoltaic unit with auxiliary frequency modulation in the photovoltaic storage station, a droop control strategy of the photovoltaic unit inverter is designed according to a direct current side control method of the photovoltaic unit, so that the active frequency modulation capability of each photovoltaic unit in the photovoltaic storage station is fully exerted, meanwhile, the remaining adjustable capacity of each photovoltaic unit tends to be consistent is guaranteed, a power distribution method of frequency response of multiple photovoltaic units in the photovoltaic storage station is designed, and frequency tracking of a single unit level of the photovoltaic unit is achieved.
To obtain maximum power, the dc side of the photovoltaic unit is typically controlled using Maximum Power Point Tracking (MPPT). MPPT control ensures the maximum utilization of photovoltaic energy, but leads to poor controllability of active output of a photovoltaic unit, and cannot meet the frequency modulation requirement of a system. Therefore, in order to realize active control of the photovoltaic units, a part of the photovoltaic units in the optical storage station are enabled to work in a load shedding control (PRC) mode, the operation points of the photovoltaic units deviate from the maximum power point, and a certain active standby capacity is reserved for participating in frequency modulation. In the load shedding mode, after the power grid frequency fluctuates, the photovoltaic system can adjust the output power upwards/downwards, and the fluctuation of the power grid frequency is restrained.
The reference value of the active power output by the photovoltaic unit operating in the load shedding control mode can be expressed as:
P prc,ref,l ＝P mppt,l ·γ l
wherein: l is the number of the photovoltaic unit accessed in the light storage station; p (P) prc,ref,l Outputting a reference value of active power for a photovoltaic unit l in a load shedding control (PRC) mode; p (P) mppt,l The estimated value of the active maximum output power of the photovoltaic unit can be obtained by measuring the adjacent photovoltaic units working in the MPPT mode; gamma ray l Active power regulating factor of photovoltaic unit, gamma l ∈[0,1]And has gamma in steady state condition l ＝0.5γ l,max Wherein gamma is l,max The active power adjustment factor corresponding to the maximum value of the adjustable active power of the photovoltaic unit l.
The photovoltaic unit inverter participating in the frequency response can adopt PQ control, and the aim of participating in primary frequency modulation of the power grid is achieved by tracking external instructions.
In order to fully exert the active frequency modulation capability of each photovoltaic unit in the photovoltaic storage station, and simultaneously ensure that the residual adjustable capacity of each photovoltaic unit tends to be consistent, all photovoltaic units applying load shedding control in one photovoltaic storage station receive frequency modulation instructions in proportion. Firstly, calculating the adjustable active residual quantity of the Shan Tai photovoltaic unit:
ΔP up,l ＝P mppt,l -P e,l
ΔP down,l ＝P e,l -P mppt,l ·γ l,max
wherein: ΔP up,l Active power surplus which can be increased for the photovoltaic unit l; ΔP down,l Active power surplus capable of being reduced for the photovoltaic unit l; p (P) e,l The active output value of the photovoltaic unit l at the current moment. Thereby defining the active distribution weight coefficient alpha of the photovoltaic unit l l The following are provided:
wherein: ΔP PV.i Light for the ith optical storage stationTotal regulating quantity of the volt-active power; alpha l The weight coefficient is distributed for the active power of the photovoltaic units l, and n is the number of the photovoltaic units.
To sum up, the photovoltaic unit l in the distributed load shedding control mode outputs a reference value P of active power prc,ref,l The method comprises the following steps:
P prc,ref,l ＝P e,l +α l ·ΔP PV.i 。
aiming at an energy storage unit which participates in auxiliary frequency modulation in an optical storage station, the embodiment aims at keeping the charge State (SOC) of the energy storage unit at 50% and reducing the action times of the energy storage unit at the same time according to an energy storage inverter control method of the energy storage unit which participates in frequency modulation, and establishes a power distribution scheme of multiple energy storage units in the optical storage station, so that power tracking of an auxiliary photovoltaic unit of the energy storage unit in the optical storage station is realized.
In an actual photovoltaic field station, frequency modulation is often limited by a power adjusting range of the single photovoltaic unit, and the frequency modulation effect is affected. Therefore, the mode of configuring the energy storage unit is adopted at present to improve the active regulation and control capability of the optical storage station. The energy storage inverter participating in frequency modulation generally adopts droop control, and simulates the power frequency droop characteristic of a generator set with a speed regulator when participating in primary frequency modulation of a power grid so as to realize primary frequency modulation. Since the droop control method of the energy storage inverter is commonly applied, a detailed description is omitted. Active reference power P for each energy storage unit in an optical storage station bess,ref,i Will be derived from the power allocation strategy described below.
When the energy storage power distribution scheme is designed, in order to avoid the condition of overcharge and overdischarge in the power distribution process of the energy storage units in the optical storage station, the energy storage action times are reduced, and a reasonable action scheme is required to be designed according to the charge state of the energy storage units. Defining the charge state of the energy storage unit as SOC, SOC epsilon [0,1], wherein SOC=1 indicates that the energy storage unit is fully saturated and cannot continuously absorb energy, and SOC=0 indicates that the energy storage unit is exhausted and cannot continuously release energy. The SOC is divided into different sections, and the requirements of each section on the charge and discharge conditions are different:
1) Charging out-of-limit area: SOC (State of Charge) max <SOC<1, the electric quantity of the energy storage unit is too high,the high-voltage power source is marked as H, the priority is highest during discharging, and the output range is more than or equal to 0 and less than or equal to P max ；
2) Charging alert zone: SOC (State of Charge) high <SOC<SOC max The energy storage unit has high electricity quantity, which is marked as 'MH', the discharge priority is higher, and the output range is-P H <P<P max ；
3) Normal working area: SOC (State of Charge) low <SOC<SOC high The electric quantity of the energy storage unit is normal, and the energy storage unit is in a chargeable and dischargeable stage and is marked as M, and the output range is-P max ≤P≤P max ；
4) Discharge warning area: SOC (State of Charge) min <SOC<SOC low The energy storage unit has low electric quantity, is recorded as ML, has high charging priority and has an output range of-P max ≤P≤P L ；
5) Discharge out-of-limit region: 0<SOC<SOC min The energy storage unit has low electric quantity, is marked as L, has highest charging priority and has a power output range of-P max ≤P≤0。
Wherein P is the charge and discharge power of the energy storage unit, and SOC max For maximum state of charge, SOC of the energy storage unit max ＝0.9；SOC high High-order threshold value of charge state of energy storage unit, SOC high ＝0.6，SOC low As the charge state low-order threshold value of the energy storage unit, SOC low ＝0.4，SOC min Is the minimum value of the charge state of the energy storage unit, SOC min ＝0.1；P max Maximum charge and discharge power of the energy storage unit; p (P) L Is the charge state of the energy storage unit is in [ SOC ] min ，SOC low ]A smoothing power limit set at the time of the range; p (P) H Is the charge state of the energy storage unit is in [ SOC ] high ，SOC max ]The smoothed power limit set at range time is expressed as:
where a is a coefficient determined by the state of charge of the energy storage unit.
Weight distribution is then performed using a fuzzy algorithm. The fuzzy controller uses the total regulating power P of the energy storage unit in the station calculated in the step S3 bess,ref And the real-time SOC of each energy storage unit is used as an input, the charge and discharge weight of each energy storage unit is output, and the charge and discharge sequence is determined according to the weight from large to small, so that the SOC of each energy storage unit is stabilized at about 0.5, and the energy storage units are kept in a chargeable and dischargeable state.
And defining the SOC fuzzy subset of the energy storage unit as 5 parts, namely [ H, MH, M, ML and L ], and representing the SOC fuzzy subset as [ charge out-of-limit area, charge guard area, normal working area, discharge guard area and discharge out-of-limit area ]. The weight D (t) is defined in the range of [0,1], and its fuzzy subset is also divided into 5 parts, respectively [ D, MD, M, MX, X ], representing the meaning of [ big, medium, small ]. The corresponding rule is as follows: when the energy storage unit discharges, the discharge priority of the high SOC is high, namely the weight D (t) is large, and the weight D (t) is reduced along with the reduction of the SOC; when the energy storage unit is charged, the charging priority of SOC is high, and D (t) decreases as SOC increases. The charge-discharge fuzzy rules of the energy storage unit are shown in tables 1 and 2.
TABLE 1 charging fuzzy rule Table
TABLE 2 discharge fuzzy rule Table
The output priority of different energy storage units under each condition can be obtained through the fuzzy rule, so that the reasonable power distribution of the energy storage units in different states in the optical storage station is realized.
The embodiment designs an overall control method of the optical storage station based on virtual synchronous generator control aiming at the optical storage station comprising a plurality of photovoltaic units and energy storage units, realizes inertial support and primary frequency response of the optical storage station layer, and inhibits frequency dynamic fluctuation. And taking all photovoltaic units and energy storage units in the optical storage station as a whole to carry out optical storage station control design. The optical storage station can be regarded as an equivalent virtual synchronous generator from outside, and external dynamic inertia support and primary frequency adjustment are realized by acquiring the power deviation and the power change rate of the grid-connected point of the optical storage station in real time; and an active power distribution strategy of the photovoltaic unit and the energy storage unit is designed in the photovoltaic unit and the energy storage unit, so that rapid power compensation is realized.
The virtual synchronous power generation control structure is used for carrying out equivalent on inertia and damping characteristics of the synchronous generator, and the relation between frequency and active power is expressed as follows:
wherein: omega is the angular velocity of the system; j is virtual inertia; d is a damping coefficient; omega n Is an angular velocity reference value; p (P) m The mechanical power is mechanical power, and theta is an output power angle; p (P) e Is an active output; p (P) ref Is an active reference value; k (K) ω Is the angular velocity droop gain factor; t is time.
The analog virtual synchronous generator equation, taking into account reactive voltage control temporarily, the frequency control model of the ith optical storage station can be expressed as:
wherein: k (k) p,i The integral active droop coefficient of the ith optical storage station; j (J) i Virtual inertia for the ith optical storage station; omega i The angular velocity at the point of the ith optical storage station; omega n,i An i-th optical storage station angular velocity reference value; d (D) i The damping coefficient of the ith optical storage station; ΔP i The whole active adjustment quantity of the optical storage station is obtained.
Next, an optical storage station internal power distribution method is designed. Considering the active cut of photovoltaic units increases the cost of light rejection and results in limited photovoltaic active regulation capability due to light rejection limitations. But at the same time, the cost and maintenance cost of the energy storage unit are relatively high, and frequent starting of the energy storage unit will reduce the service life of the energy storage unit. Based on the above, the light storage matching method during primary frequency modulation is designed as follows:
wherein: ΔP PV,i For the total photovoltaic active adjustment quantity of the ith optical storage station, delta P BESS,i For the total energy storage regulating quantity P in the ith optical storage station prc,i For the photovoltaic active standby capacity, delta P, in the ith optical storage station at the current moment i And (5) the integral active adjustment quantity of the ith optical storage station.
According to the method, when the frequency of the grid connection point of the optical storage station exceeds the dead zone range, the sagging control of the optical storage station is calculated in real time to obtain the integral active adjustment quantity of the optical storage station. Comparing the overall active power adjustment of the optical storage station with the active photovoltaic standby capacity of the optical storage station at the current moment, such as delta P i ≤P prc,i Only the photovoltaic in the optical storage station is needed to participate in the frequency support, namely delta P PV,i ＝ΔP i ，ΔP BESS,i =0; such asThe residual power of light in the light storage station is supplemented by the energy storage unit, namely delta P PV,i ＝P prc,i ，ΔP BESS,i ＝ΔP i -P prc,i 。
In the embodiment, a secondary frequency modulation method based on robust control is established for a regional power grid comprising a plurality of optical storage stations, so that the cooperation of the plurality of optical storage stations and the secondary frequency adjustment of the regional power grid are realized, and the steady-state deviation of the regional frequency is reduced. Firstly, a frequency modulation dynamic model of a regional power grid is established. Taking a regional power grid comprising a thermal power unit and a virtual synchronous optical storage station as an example, and simultaneously taking the influence of fluctuation of photovoltaic output, load and the like into consideration, establishing a state space model of secondary frequency control of the regional power grid.
The frequency response model of the regional power grid is:
wherein: Δf is the regional power grid frequency deviation, H is the regional power grid inertia coefficient, D is the regional power grid load damping coefficient, ΔP m Is the output power variation quantity delta P of the thermal power unit PV_BESS,i For the active output variable quantity of the ith optical storage station, delta P L S is the complex frequency, which is the load deviation.
The speed regulator model of the thermal power generating unit is as follows:
wherein: ΔP g Is the valve variable quantity, T of a thermal power machine speed regulator g ΔP is the governor time constant c,g R is the secondary frequency modulation control input of the speed regulator g Is a primary frequency modulation sag factor.
The steam turbine model of the thermal power generating unit is as follows:
wherein: t (T) ch Is the time constant of the steam turbine.
The dynamic model of the virtual synchronization optical storage station is as follows:
wherein: ΔP c,PV,i Secondary tuning for the ith optical storage stationFrequency control input, T PV,i Is the ith optical storage station time constant.
Regional frequency deviation signal model:
ΔACE＝β·Δf
delta ACE is a regional frequency deviation signal, and beta is a regional frequency deviation coefficient;
thus, a state space model of regional power grid secondary frequency control of the thermal power generating unit and the optical storage station is obtained as follows:
in the method, in the process of the invention,the variable quantity of the state variable is z (t) is an output variable, u (t) is a control variable, w (t) is a disturbance variable, and the matrix x of the state variable T ＝[Δf,ΔACE,ΔP m ,ΔP g ,ΔP c,g ,ΔP PV_BESS,i ,ΔP c,PV,i ]Matrix w of disturbance variables T ＝[ΔP PV,i ,ΔP L ]Matrix u of control variables T ＝[ΔP c,g ,ΔP c,PV,i ]Where i=1, 2, …, n; a is a coefficient matrix of state variables, B u Coefficient matrix for control variable, B w The coefficient matrix is the disturbance variable, and C is the coefficient matrix of the output variable.
And designing a secondary frequency control strategy of the regional power grid on the basis of the frequency modulation dynamic model of the regional power grid. Because of uncertain power disturbance such as photovoltaic output, load and the like in the regional power grid, a control model has a bounded error. Thus consider robust H-based ∞ And the secondary frequency modulation controller is controlled and designed, so that the influence of various uncertainty disturbance on the control is reduced, and the robustness performance of the system is improved.
Design robust H ∞ The method of the controller is to solve a controller u(s) =k(s) y(s) so that the controlled closed-loop system meets the following two performance indexes:
performance index i: the closed loop system has internal stability, namely, all characteristic values of a state matrix of the closed loop system are in the left half of the open complex plane;
performance index ii: closed loop transfer function T from disturbance variable to output variable wz H of(s) ∞ The norm is less than 1, namely:
||T wz (s)|| ∞ ＜ζ
in which ζ is H ∞ Performance index of the controller. The optimal H of the regional power grid can be obtained by searching the range of the zeta value of the variable and determining the minimum value of zeta ∞ A controller, i.e., a controller that minimizes disturbance rejection of the closed loop system.
Based on the above-described derived regional power grid state space equation, the performance index ii may be further expressed as follows:
||Τ wz (s)|| ∞ ＝||(C[sI-(Α+B u K)] -1 B w )|| ∞ ＜ζ
wherein: i is an identity matrix, and K is the optimal control rate of feedback control.
If for a given constant ζ >0 there is a requirement for both performance indicators, while if and only if there is a constant and a symmetric positive definite matrix X, W such that the following matrix inequality holds, the regional power grid can be progressively stabilized:
minζ 2
s.t.
X＞0
wherein T represents the transpose. By solving the optimization problem, searching an optimal solution meeting constraint, and obtaining the optimal robust H of the regional power grid ∞ The controller feeds back the optimal control rate of the control.
The above examples are intended to be illustrative of the present invention and not limiting, and modifications may be made to the present embodiments by those skilled in the art without creative contribution to the present invention as required after reading the present specification, but are protected by patent laws within the scope of the appended claims.
Claims (7)
1. The auxiliary frequency modulation method for the regional power grid optical storage station is characterized by comprising four parts, namely power distribution of frequency response of a plurality of photovoltaic units in the optical storage station, power distribution of a plurality of energy storage units in the optical storage station, inertial support and primary frequency response of an optical storage station layer, and cooperative participation of the multi-optical storage station in secondary frequency adjustment of the regional power grid; in the frequency modulation control process, instructions are sequentially issued from an upper layer to a lower layer, secondary frequency adjustment of the multi-optical storage station cooperative participation regional power grid is firstly carried out, then inertial support and primary frequency response of the optical storage station layer are carried out, and finally power distribution of frequency response of a multi-photovoltaic unit in the optical storage station and power distribution of a multi-energy storage unit in the optical storage station are carried out;
the inertial support and primary frequency response of the optical storage station level are: for an optical storage station comprising a plurality of photovoltaic units and energy storage units, taking all the photovoltaic units and the energy storage units in the optical storage station as a whole, designing a photovoltaic station integral inertia supporting and primary frequency modulation control method based on virtual synchronous generator control, and expressing a frequency control model of an ith optical storage station as follows:
wherein: k (k) p,i The integral active droop coefficient of the ith optical storage station; j (J) i Virtual inertia for the ith optical storage station; omega i The angular velocity at the point of the ith optical storage station; omega n,i An i-th optical storage station angular velocity reference value; d (D) i The damping coefficient of the ith optical storage station; ΔP i The active power adjustment quantity is the whole active power adjustment quantity of the optical storage station, and t is time.
2. The regional power grid optical storage station auxiliary frequency modulation method considering multiple time scales as claimed in claim 1, wherein the matching method of the photovoltaic units and the energy storage units in the optical storage station during primary frequency modulation is as follows:
wherein: ΔP PV,i For the total photovoltaic active adjustment quantity of the ith optical storage station, delta P BESS,i For the total energy storage regulating quantity P in the ith optical storage station prc,i For the photovoltaic active standby capacity, delta P, in the ith optical storage station at the current moment i And (5) the integral active adjustment quantity of the ith optical storage station.
3. The regional power grid optical storage station auxiliary frequency modulation method considering the multiple time scales as claimed in claim 1, wherein a robust control-based secondary frequency modulation method is established for the regional power grid comprising the multiple optical storage stations, so that the multiple optical storage stations cooperatively participate in secondary frequency adjustment of the regional power grid; the state space model for controlling the secondary frequency of the regional power grid of the thermal power generating unit and the optical storage station is established as follows:
in the method, in the process of the invention,the variable quantity of the state variable is z (t) is an output variable, u (t) is a control variable, w (t) is a disturbance variable, and the matrix x of the state variable T ＝[Δf,ΔACE,ΔP m ,ΔP g ,ΔP c,g ,ΔP PV_BESS,i ,ΔP c,PV,i ]Matrix w of disturbance variables T ＝[ΔP PV,i ,ΔP L ]Matrix u of control variables T ＝[ΔP c,g ,ΔP c,PV,i ]Where i=1, 2, …, n;a is a coefficient matrix of state variables, B u Coefficient matrix for control variable, B w The coefficient matrix is the disturbance variable, and C is the coefficient matrix of the output variable; Δf is the regional power grid frequency deviation, ΔACE is the regional frequency deviation signal, ΔP m Is the output power variation quantity delta P of the thermal power unit g Is the valve variable quantity delta P of the thermal power machine speed regulator c,g For the secondary frequency modulation control input of the speed regulator, delta P PV_BESS,i For the active output variable quantity of the ith optical storage station, delta P c,PV,i For the second FM control input of the ith optical storage station, deltaP PV,i For the total photovoltaic active adjustment quantity of the ith optical storage station, delta P L Is the load deviation amount;
design based on robust H ∞ Controlled system secondary frequency modulation controller u(s) =k(s) y(s); by solving the following optimization problems and searching the optimal solution meeting the constraint, the optimal robust H of the regional power grid can be obtained ∞ The optimal control rate of the feedback control of the controller;
minζ 2
s.t.
X＞0
wherein: zeta is H ∞ Performance index of the controller; i is an identity matrix, K is an optimal control rate of feedback control, X, W is a symmetrical positive definite matrix in the solving process, and T represents transposition.
4. The regional power grid optical storage station auxiliary frequency modulation method considering multiple time scales as claimed in claim 1, wherein the power distribution of the frequency response of the multiple photovoltaic units in the optical storage station is as follows: aiming at the photovoltaic units participating in auxiliary frequency modulation in the photovoltaic storage station, a droop control strategy of the photovoltaic unit inverter is designed according to a direct current side control method of the photovoltaic units, so that the active frequency modulation capability of each photovoltaic unit in the photovoltaic storage station is fully exerted, the remaining adjustable capacity of each photovoltaic unit is ensured to be consistent, a power distribution method of frequency response of multiple photovoltaic units in the photovoltaic storage station is designed, and frequency tracking of a single unit level of the photovoltaic units is realized.
5. The regional power grid optical storage station auxiliary frequency modulation method considering multiple time scales as claimed in claim 4, wherein a part of photovoltaic units in the optical storage station are operated in a load shedding control mode, so that the operating points of the photovoltaic units deviate from the maximum power point, and a certain active spare capacity is reserved for participating in frequency modulation; the photovoltaic unit inverter participating in the frequency response adopts constant power control, and the primary frequency modulation target participating in the power grid is realized by tracking an external instruction; establishing an active distribution weight coefficient alpha of a photovoltaic unit l l The following are provided:
wherein: l is the number of the photovoltaic unit accessed in the optical storage station, delta P PV.i The photovoltaic active power total adjustment quantity of the ith optical storage station; alpha l The weight coefficient is distributed for the active power of the photovoltaic unit l, n is the number of the photovoltaic units, and delta P is the number of the photovoltaic units up,l Active power surplus which can be increased for the photovoltaic unit l; ΔP down,l Active power surplus capable of being reduced for the photovoltaic unit l; reference value P of active power output by photovoltaic unit l in distributed load shedding control mode prc,ref,l The method comprises the following steps:
P prc,ref,l ＝P e,l +α l ·ΔP PV.i 。
wherein: p (P) e,l The active output value of the photovoltaic unit l at the current moment.
6. The regional power grid optical storage station auxiliary frequency modulation method considering multiple time scales as claimed in claim 1, wherein the power distribution of multiple energy storage units in the optical storage station is as follows: aiming at the energy storage units participating in auxiliary frequency modulation in the optical storage station, according to the control method of the energy storage inverter of the energy storage units participating in frequency modulation, aiming at keeping the charge state of the energy storage units at 50% and reducing the action times of the energy storage units, a power distribution scheme of a plurality of energy storage units in the optical storage station is formulated, and the power tracking of the energy storage units in the optical storage station is realized.
7. The regional power grid optical storage station auxiliary frequency modulation method considering the multiple time scales as claimed in claim 6, wherein when power distribution of multiple energy storage units in the optical storage station is performed, an energy storage unit weight distribution strategy is designed based on a fuzzy algorithm: when the energy storage discharges, the energy storage unit with high charge state has high discharge priority, namely the discharge weight is heavy, and the weight of the energy storage unit is reduced along with the reduction of the charge state; when the energy storage unit is charged, the energy storage unit with a low charge state has a high charging priority, and the weight thereof decreases with the increase of the charge state.
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