CN112803487A - Power system unit combination optimization method considering wind turbine generator frequency modulation control - Google Patents

Power system unit combination optimization method considering wind turbine generator frequency modulation control Download PDF

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CN112803487A
CN112803487A CN202110317846.8A CN202110317846A CN112803487A CN 112803487 A CN112803487 A CN 112803487A CN 202110317846 A CN202110317846 A CN 202110317846A CN 112803487 A CN112803487 A CN 112803487A
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frequency
wind turbine
unit
generating unit
power generating
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李德鑫
张海锋
杨德友
王博
吕项羽
高僮
刘畅
王伟
姜栋潇
张懿夫
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STATE GRID JILINSHENG ELECTRIC POWER SUPPLY Co ELECTRIC POWER RESEARCH INSTITUTE
Northeast Electric Power University
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STATE GRID JILINSHENG ELECTRIC POWER SUPPLY Co ELECTRIC POWER RESEARCH INSTITUTE
Northeast Dianli University
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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
    • 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
    • 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
    • H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
    • 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]
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/76—Power conversion electric or electronic aspects

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Abstract

The invention relates to a combined optimization method of a power system unit considering wind turbine unit frequency modulation control, belonging to the field of power systems; the wind turbine generator system is subjected to overspeed load shedding and virtual inertia control, and the frequency modulation factor of the fan is considered in the research of the power system generator set combination strategy considering dynamic frequency constraint. When the combination mode under the conventional constraint of the thermal power generating unit does not meet the requirement of the frequency limit value, the fan is controlled within the fan load reduction constraint range, so that the wind power generating unit has the frequency modulation capability and the system inertia is improved.

Description

Power system unit combination optimization method considering wind turbine generator frequency modulation control
Technical Field
The invention belongs to the field of power systems, and particularly relates to optimization of a unit combination strategy of a power system.
Background
With the popularization of wind power generation technology, the proportion of wind power generation in a power system is increasing. According to data display, the accumulated grid-connected installed capacity of China reaches 1.98 hundred million kilowatts and accounts for 9.7 percent of the capacity of all generators by 9 months in 2019, and the accumulated grid-connected installed capacity of wind power in China reaches more than 2.1 hundred million kilowatts by the end of 2020. When the large-scale wind turbine generator system is connected to the grid to bring huge economic benefits and environmental benefits, the wind turbine is connected with the power grid through the power electronic converter, the converter separates the rotating kinetic energy of the fan from the system, the inertia of the system is reduced due to the improvement of the wind power permeability, and the system faces the challenge of safe and stable operation.
In recent years, a large amount of research is carried out by domestic and foreign scholars on how to reduce the influence of large-scale wind power integration on system inertia and system frequency, and the summary includes the following 3 solutions: 1) virtual inertia control method: a control link of the fan introduces a change signal of system frequency, and when the frequency changes suddenly, kinetic energy stored by a fan rotor is released or absorbed and converted into active power participating in frequency modulation. 2) Overspeed load shedding and variable pitch control method: the wind turbine generator rotor overspeed or variable pitch enables the fan to be separated from the maximum power output to realize load shedding operation, and active power reserve of the fan is increased, so that the wind turbine generator has primary frequency modulation capability. 3) Energy storage systems such as a battery pack and a pumped storage power station are connected to the grid to improve the frequency modulation capability of the system.
Under the large-scale wind power grid connection, the traditional unit combination strategy does not contain system frequency constraint, and the problem that the system frequency is out of limit when disturbance occurs under the traditional combination strategy is solved. In the traditional wind power grid-connected unit combination research, a wind power unit is processed according to the condition that the wind power unit does not have primary frequency modulation capability and inertia support cannot be provided for a system.
The invention adopts overspeed load shedding and virtual inertia control on the wind turbine generator, and adds frequency dynamic constraint considering fan frequency modulation on the basis of a traditional generator combination model. When the combination mode under the conventional constraint of the thermal power generating unit does not meet the requirement of the frequency limit value, the fan can be controlled within the fan load reduction constraint range, so that the fan has the frequency modulation capability and the system inertia is improved.
Disclosure of Invention
The invention aims to provide a power system unit combination optimization method considering wind turbine unit frequency modulation control, so as to solve the technical problems mentioned in the background technology.
In order to achieve the purpose, the specific technical scheme of the power system unit combination optimization method considering the wind turbine generator frequency modulation control is as follows:
a power system unit combination optimization method considering wind turbine unit frequency modulation control comprises the following steps:
step S1: acquiring unit characteristic data Pmaxi, Pmini, Rupi, Rdni and T of a thermoelectric generator set in a power systemi,on、Ti,offAnd unit characteristic data P of the wind turbinew,i,tmax、rmax、rmin(ii) a Setting a variable parameter Pg,i,t、Pw,t、Ui,t、ψt(ii) a And obtaining the load demand and the predicted maximum wind power output within 24 hours.
Step S2: solving the optimal value of the objective function by using a Lagrange relaxation algorithm to meet the requirement of a conventional constraint conditional expression in the first-layer optimization, transferring the obtained combination result to the second-layer optimization, carrying out secondary optimization calculation on the constraint of the lowest value of the dynamic frequency, and solving a penalty variable psitThe value is obtained.
Step S3: judging penalty variable psitWhether less than 0. If psitIf the combined result is less than 0, the combined result meets the requirement of the frequency limit value, and the time interval combined scheme is output; if psitIf the frequency constraint condition is more than 0, entering into benders cut solution, increasing frequency constraint conditions of benders feedback parts, returning the obtained result to a layer of optimization, and sequentially circulating until the penalty variable psitAnd outputting a combined result after the requirements are met.
In the above method for optimizing a power system unit combination in consideration of frequency modulation control of a wind turbine unit, Pmaxi and Pmini in step S1 are the upper and lower limits of the output of the ith thermal power unit; rupi and Rdni are respectively an upper limit and a lower limit of the slope climbing of the ith thermal power generating unit; t isi,on、Ti,offThe minimum starting time and the minimum stopping time of the ith thermal power generating unit are respectively. Pw,i,tmax is the upper limit of the output force of the ith wind turbine generator set; rmax and rmin are upper and lower limits of the rotating speed of the rotor of the wind turbine; pg,i,t、Pw,t、Ui,tThe output quantity is the output quantity of the ith thermal power generating unit in the t time period; the output of the wind turbine generator at t time interval is large or small; starting and stopping state, U, of ith thermal power generating unit at t time period i,t1 is open, Ui,tOff for 0.
In the above method for optimizing a power system unit combination in consideration of wind turbine unit frequency modulation control, the unit combination model optimization objective function of step S2 is divided into three parts: the power generation cost of the thermal power generating unit, the start and stop cost of the unit and the operation and maintenance cost of the fan. With the goal of minimizing the total operating cost for each time period, the objective function can be expressed as:
Figure BDA0002991925150000031
wherein T is the number of hours of a scheduling cycle; k is a radical ofiThe operation and maintenance cost coefficient is the ith wind turbine generator; pg,i,tAnd Pw,i,tThe output power of the ith thermal power generating unit and the output power of the wind power generating unit at the moment t are respectively the output power of the ith thermal power generating unit and the output power of the wind power generating unit at the moment t; SUP (super)i,t、SDni,tRespectively the start-stop cost; a isi，bi，ciAre cost function coefficients.
The conventional constraints of the unit combination in the first layer of optimization are as follows:
and power balance constraint:
Figure BDA0002991925150000032
in the formula: pL,i,tLoad is planned for node i at time t, and g is the number of nodes.
Conventional constraint of thermal power generating units:
Figure BDA0002991925150000033
Figure BDA0002991925150000034
Figure BDA0002991925150000035
Figure BDA0002991925150000036
Figure BDA0002991925150000037
the method comprises the following steps of respectively performing output restraint, climbing restraint and start-stop restraint on the thermal power generating unit. Wherein u isi,tThe starting and stopping state of the ith thermal power generating unit at the t time period is shown; pmin g, i and Pmax g, i are respectively the minimum output and the maximum output of the ith thermal power generating unit; rup i and Rdn i are respectively an upper limit and a lower limit of the slope climbing of the ith thermal power generating unit; t isi,on、Ti,offThe minimum starting time and the minimum stopping time of the ith thermal power generating unit are respectively.
Conventional constraint of a wind turbine generator:
ωrmin≤ωr≤ωrmax (8)
0≤Pw,i,t≤Pw,i,tmax (9)
rotor speed constraint and power constraint are respectively adopted. In the formula, rmax and rmin are upper and lower limits of the rotating speed of the rotor of the wind turbine generator; pw,i,tmaxAnd the output upper limit of the ith wind turbine generator set is set.
And (3) system rotation standby constraint:
Figure BDA0002991925150000041
in the formula, λ is a spare coefficient.
The method for calculating the lowest point of the dynamic frequency in step S2 is as follows:
Figure BDA0002991925150000042
wherein: f. ofnadirIs the lowest value of the dynamic frequency; f. of0Is a reference frequency; t is tnadirTime corresponding to the lowest point frequency; n is the natural vibration frequency; xi is a damping ratio; Δ P is the disturbance power; heqIs the system inertia time constant; rTIs a static adjustment coefficient; f is the fraction of the total power generated by the high pressure turbine; TR is a time constant of the speed regulator; d is a damping coefficient. Omegan、ξ、RTF and tnadirThe expression is as follows:
Figure BDA0002991925150000043
Figure BDA0002991925150000044
wherein m is the number of the wind turbine generators; RW drop (Pw) is a fan static difference adjustment coefficient function taking wind power as a variable; riIs as followsiStatic difference adjustment coefficient of the thermal power generating unit; kiThe power factor is the mechanical power gain factor of the ith thermal power generating unit; fiIs the fraction of the power produced by the ith high pressure turbine.
Because the optimization model has high nonlinear characteristics due to the multi-layer nested function in the formula (11), the invention introduces the piecewise linearization technology to process the calculation of the lowest value of the dynamic frequency. The left expression of the unequal sign in formula (11) is regarded as HeqF and RTIs a function of, and is denoted as Q (R)T,F,Heq) Introducing penalty factor psi in two-layer optimizationtThe unit combination frequency constraint is as follows:
Q(RT,F,Heq)+ψt≥fmin (14)
in the above power system unit combination optimization method considering wind turbine generator frequency modulation control, the constraints in the benders feedback in step S3 are expressed as:
[Q*(RT,F,Heq)-Q(RT,F,Heq)]-ψt≥0 (15)
in the formula Q*(RT,F,Heq) Obtained by a layer of optimization calculations.
The method for optimizing the combination of the power system units by considering the frequency modulation control of the wind turbine units has the following advantages:
1) compared with the traditional unit combination model without frequency constraint, the unit combination model provided by the invention has the advantages that the capability of resisting burst interference of the system is improved, and the frequency stability of the system is improved.
2) Compared with the unit combination model which contains system dynamic frequency constraint but does not participate in frequency modulation, the unit combination model fan provided by the invention provides certain inertial support, and reduces the frequency modulation burden of the thermal power unit under sudden disturbance. The model can reduce the number of starting thermal power generating units, achieve the purpose of economy, simultaneously improve the proportion of wind power output in the system, and improve the wind power consumption capacity of the system.
Drawings
Fig. 1 is a load curve and a maximum wind power output curve in 24 hours in example 1.
Fig. 2 is a frequency nadir distribution in example 1.
Fig. 3 is a wind power output curve in example 1.
Detailed Description
In order to better understand the purpose, structure and function of the present invention, the following describes a method for optimizing a power system unit combination considering wind turbine generator frequency modulation control in further detail with reference to the accompanying drawings.
As shown in fig. 1, the wind turbine generator system is subjected to overspeed load shedding and virtual inertia control, and the frequency modulation factor of the wind turbine is considered in the power system generator set combination strategy research considering dynamic frequency constraints. When the combination mode under the conventional constraint of the thermal power generating unit does not meet the requirement of the frequency limit value, the fan is controlled within the fan load reduction constraint range, so that the wind power generating unit has the frequency modulation capability and the system inertia is improved.
Example 1:
in order to verify that the model and the method provided by the patent can improve the dynamic frequency of the system, a Matlab software platform is used for building a 10-machine system containing wind power grid connection, and a CPLEX12.1 solver is combined for carrying out optimization calculation on a target function. The load damping coefficient D is 1, and TR is 8 s. The dispatching cycle is 24 hours, and the load curve and the maximum output curve of wind power in 24 hours are shown in figure 1. The fundamental frequency of the system is 50Hz, the safety frequency limit is 49.2Hz, and the disturbance is assumed to be the load of the system which suddenly increases by 10%.
Taking the following three unit combination schemes, and comparing the results:
scheme 1): and (3) a unit combination scheme containing constant-reduction beam formulas (2) - (10) and no system frequency constraint is adopted, and the result is recorded as R-1.
Scheme 2): a system frequency constraint formula (14) is added on the basis of the scheme 1, but the wind power generation set does not provide inertia support and primary frequency modulation, only the thermal power generation set participates in system frequency modulation, and the result is recorded as R-2.
Scheme 3): and a system frequency constraint formula (15) is added on the basis of the scheme 1, wherein the wind turbine generator participates in frequency modulation. The result was designated as R-3.
Table 1 records the maximum value of the frequency deviation when the disturbance occurs for 24 periods; and the table 2 records the load shedding condition of the wind turbine generator at each time interval under the scheme 3, and the table 3 records the starting state of the thermal power generating unit.
TABLE 1 maximum frequency deviation in 24 hours
Figure BDA0002991925150000061
Figure BDA0002991925150000071
The minimum and maximum load periods in 1h and 12h day are selected as examples. For the time interval 1h, the scheme 1 only starts the unit1 of the thermal power generating unit to provide the load demand, and the system frequency stability is poor due to the fact that the system inertia coefficient is small. When the system is suddenly loaded by 10%, the lowest value of the frequency drop of the scheme is 49.09Hz, which is lower than the frequency safety range.
And in the same time period, the unit2, 5 and 6 are selectively started in the scheme 2, and compared with the scheme 1, the standby capacity of the system is improved by increasing the starting number of the thermal power generating units, so that the frequency modulation capability of the system is improved. Under the same disturbance, the minimum value of frequency drop is 49.28Hz, and the frequency safety requirement is met.
Scheme 3 adopts fan deloading mode to make wind turbine generator system have the frequency modulation ability. The wind power generator has enough wind energy in a 1h time period, and as can be seen from table 2, the wind power generator is subjected to load shedding operation of 9.90% in the time period, participates in system inertial support and primary frequency modulation, and can be used for enabling the system to have enough frequency modulation capability by matching with a unit1 of a thermal power generator, and the lowest frequency drop value is 49.20Hz in the mode, so that the frequency safety requirement is met.
TABLE 2 wind turbine generator load shedding amount within 24 hours in case 3
Figure BDA0002991925150000072
When disturbance occurs in a period of 12h, the unit15 of the unit under the scheme 1 is in a starting state due to the increase of load, 3.56 seconds after the disturbance occurs, the lowest value of the system frequency is 49.10Hz, and the requirement of the lowest value of the frequency is not met under the scheme. Compared with scheme 1, in scheme 2, unit6 and unit 8 are added, and the spare capacity is increased to resist the influence of interference on the frequency, and under the scheme, the system frequency reaches the minimum value of 49.28Hz after the disturbance occurs for 3.32 seconds, and the requirement of the minimum value of the frequency is met. Different from the scheme 2, compared with the scheme 1, the scheme 3 has the advantages that one more electric spark generator unit6 is started, and the rest of the electric spark generator units are unloaded by 9.65% to increase the spare capacity, so that the system inertia and the primary frequency modulation capacity are increased. 3.47 seconds system frequency reaches the minimum and is 49.20Hz after the disturbance takes place under this scheme, satisfies the minimum requirement of frequency to compare in scheme 2 and start a unit less, practiced thrift the cost of electricity generation.
TABLE 3 starting-up state of thermal power generating unit
Figure BDA0002991925150000081
In the table, "1" indicates that the thermal power generating unit is turned on, and "0" indicates that the thermal power generating unit is turned off.
Fig. 2 is a frequency lowest value distribution diagram of 24 periods under three schemes, and the wind power output curve of each period in fig. 3 can be obtained by combining: although the wind power of the scheme 1 is in the maximum output state, the lowest value of the frequency of the scheme fluctuates within the range of 49.16 +/-0.11 Hz when disturbance occurs because the fan does not participate in system frequency modulation and the wind power output ratio is high. Only 5-8h time periods in 24 time periods meet the frequency requirement, the system frequency in the rest time periods is obviously lower than the frequency limit value, the stability of the system frequency is poor, and the scheme can not meet the constraint requirement of the system frequency.
According to the scheme 2, the dynamic constraint of the system frequency is considered, but the fan does not participate in frequency modulation, and the system increases the starting number of the thermal power generating units, so that the inertia and the spare capacity of the system are improved. The lowest value of the frequency fluctuates within the range of 49.30 +/-0.03 Hz under the scheme, and each time interval meets the requirement of frequency constraint, so that the system has better frequency stability. However, according to the scheme, due to the increase of the output of the thermal power generating unit, the wind power output is greatly reduced, and the wind power utilization rate is seriously reduced.
In the scheme 3, the dynamic constraint of the system frequency considering the fan frequency modulation is considered, the wind turbine generator is used for load shedding and frequency modulation under the scheme, the lowest value of the frequency in each time interval is controlled to be above 49.20Hz, and the system frequency requirement is met. In the 5-8h period, the frequency modulation capability of the thermal power generating unit meets the requirement, so that the wind power generating unit does not take a load shedding and frequency modulation action in the period, and the wind power is in the maximum output state in the 5-8h period as same as the scheme 1. Compared with the scheme 1, the scheme 3 improves the frequency stability of the system although the wind power is not in the maximum output state. Compared with the scheme 2, the scheme 3 and the scheme 2 both meet the requirement of system frequency stability, but the wind power output ratio of the scheme 3 is obviously higher than that of the scheme 2, and the wind power output can be improved by 23.29 percent to the maximum. Scheme 3 still improves system wind-powered electricity generation digestion ability when satisfying system frequency dynamic constraint.
The method is used for further verifying the superiority of the unit combination scheme of the wind turbine generator participating in frequency modulation compared with the traditional unit combination scheme. And counting the starting number of the thermal power generating units under the three schemes in 24 time periods. On the premise of meeting the dynamic constraint of system frequency, the number of the starting thermal power generating units in the scheme 3 is obviously less than that in the scheme 2, the starting of the thermal power generating units is reduced, and the coal economy is improved.
The cost of power generation for the three schemes is shown in table 4, and a comparison of the cost of the three schemes can be made: scheme 2, 3 compared with scheme 1, the power generation cost of both schemes is increased due to the increase of the system dynamic frequency constraint. But scheme 3 has a reduced cost of power generation compared to scheme 2. The economy of scheme 3 is better than that of scheme 2 in meeting the frequency dynamics constraint requirements.
TABLE 4 cost of power generation for three scenarios
Figure BDA0002991925150000101
It is to be understood that the present invention has been described with reference to certain embodiments, and that various changes in the features and embodiments, or equivalent substitutions may be made therein by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (5)

1. A combined optimization method of a power system unit considering wind turbine unit frequency modulation control is characterized by comprising the following steps which are sequentially carried out:
step S1: acquiring unit characteristic data Pmaxi, Pmini, Rupi, Rdni and T of a thermoelectric generator set in a power systemi,on、Ti,offAnd unit characteristic data P of the wind turbinew,i,tmax、rmax、rmin(ii) a Setting a variable parameter Pg,i,t、Pw,t、Ui,t、ψt(ii) a Obtaining the load demand and the predicted maximum wind power output within 24 hours;
step S2: solving the optimal value of the objective function by using a Lagrange relaxation algorithm to meet the requirement of a conventional constraint conditional expression in the first-layer optimization, transferring the obtained combination result to the second-layer optimization, carrying out secondary optimization calculation on the constraint of the lowest value of the dynamic frequency, and solving a penalty variable psitA value;
step S3: judging penalty variable psitIf it is less than 0, iftIf the combined result is less than 0, the combined result meets the requirement of the frequency limit value, and the time interval combined scheme is output; if psitIf the frequency constraint condition is more than 0, entering into benders cut solution, increasing frequency constraint conditions of benders feedback parts, returning the obtained result to a layer of optimization, and sequentially circulating until the penalty variable psitAnd outputting a combined result after the requirements are met.
2. The method for optimizing the power system unit combination in consideration of the frequency modulation control of the wind turbine generator unit as claimed in claim 1, wherein Pmaxi and Pmini in step S1 are upper and lower limits of the output of the ith thermal power unit; rupi and Rdni are respectively an upper limit and a lower limit of the slope climbing of the ith thermal power generating unit; t isi,on、Ti,offRespectively setting minimum starting time and minimum stopping time of the ith thermal power generating unit;
Pw,i,tmax is the upper limit of the output force of the ith wind turbine generator set; rmax and rmin are upper and lower limits of the rotating speed of the rotor of the wind turbine; pg,i,t、Pw,t、Ui,tThe output quantity is the output quantity of the ith thermal power generating unit in the t time period; the output of the wind turbine generator at t time interval is large or small; starting and stopping state, U, of ith thermal power generating unit at t time periodi,t1 is open, Ui,tOff for 0.
3. The method for optimizing a power system unit combination in consideration of wind turbine unit frequency modulation control according to claim 1, wherein the unit combination model optimization objective function of step S2 is divided into three parts: the method comprises the following steps of (1) generating cost of a thermal power generating unit, starting and stopping cost of the unit and operation and maintenance cost of a fan;
with the goal of minimizing the total operating cost for each time period, the objective function can be expressed as:
Figure FDA0002991925140000011
wherein T is the number of hours of a scheduling cycle; k is a radical ofiThe operation and maintenance cost coefficient is the ith wind turbine generator; pg,i,tAnd Pw,i,tThe output power of the ith thermal power generating unit and the output power of the wind power generating unit at the moment t are respectively the output power of the ith thermal power generating unit and the output power of the wind power generating unit at the moment t; SUP (super)i,t、SDni,tRespectively the start-stop cost; a isi，bi，ciIs a cost function coefficient;
the conventional constraints of the unit combination in the first layer of optimization are as follows:
and power balance constraint:
Figure FDA0002991925140000021
in the formula: pL,i,tPlanning load for a node i at the moment t, and g is the number of nodes;
conventional constraint of thermal power generating units:
Figure FDA0002991925140000022
Figure FDA0002991925140000023
Figure FDA0002991925140000024
Figure FDA0002991925140000025
Figure FDA0002991925140000026
respectively as output constraint, climbing constraint and start-stop constraint of thermal power generating uniti,tThe starting and stopping state of the ith thermal power generating unit at the t time period is shown; pmin g, i and Pmax g, i are respectively the minimum output and the maximum output of the ith thermal power generating unit; rup i and Rdn i are respectively an upper limit and a lower limit of the slope climbing of the ith thermal power generating unit; t isi,on、Ti,offRespectively setting minimum starting time and minimum stopping time of the ith thermal power generating unit;
conventional constraint of a wind turbine generator:
ωrmin≤ωr≤ωrmax (8)
0≤Pw,i,t≤Pw,i,tmax (9)
the method comprises the following steps of respectively restricting the rotating speed of a rotor and restricting the power, wherein rmax and rmin are the upper limit and the lower limit of the rotating speed of the rotor of the wind turbine generator; pw,i,tmaxThe output upper limit of the ith wind turbine generator set is set;
and (3) system rotation standby constraint:
Figure FDA0002991925140000031
in the formula, λ is a spare coefficient.
4. The method for optimizing the power system unit combination in consideration of the wind turbine frequency modulation control according to claim 1, wherein the method for calculating the lowest point of the dynamic frequency in step S2 is as follows:
Figure FDA0002991925140000032
wherein: f. ofnadirIs the lowest value of the dynamic frequency; f. of0Is a reference frequency; t is tnadirTime corresponding to the lowest point frequency; n is the natural vibration frequency; xi is a damping ratio; Δ P is the disturbance power; heqIs the system inertia time constant; rTIs a static adjustment coefficient; f is the fraction of the total power generated by the high pressure turbine; TR is a time constant of the speed regulator; d is the damping coefficient, omegan、ξ、RTF and tnadirThe expression is as follows:
Figure FDA0002991925140000033
Figure FDA0002991925140000034
wherein m is the number of the wind turbine generators; RW drop (Pw) is a fan static difference adjustment coefficient function taking wind power as a variable; riIs as followsiStatic difference adjustment coefficient of the thermal power generating unit; kiThe power factor is the mechanical power gain factor of the ith thermal power generating unit; fiIs the fraction of the power produced by the ith high pressure turbine.
5. The method for optimizing the power system unit combination in consideration of the wind turbine unit frequency modulation control according to claim 4, wherein the formula (11) introduces a piecewise linearization technique to calculate the lowest value of the dynamic frequency, and the left-end expression with the unequal sign of the formula (11) is regarded as HeqF and RTIs a function of, and is denoted as Q (R)T,F,Heq) Introducing penalty factor psi in two-layer optimizationtThe unit combination frequency constraint is as follows:
Q(RT,F,Heq)+ψt≥fmin (14)
in the above power system unit combination optimization method considering wind turbine generator frequency modulation control, the constraints in the benders feedback in step S3 are expressed as:
[Q*(RT,F,Heq)-Q(RT,F,Heq)]-ψt≥0 (15)
in the formula Q*(RT,F,Heq) Obtained by a layer of optimization calculations.
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