CN105162161B - A kind of wind power base transient state of sending outside containing different type blower fan cuts machine control method - Google Patents

Abstract

The invention relates to a method for controlling transient shutdown of wind power bases with different types of wind turbines. The cut-off amount of the thermal power unit in the case of thermal ratio cut-off; parameter initialization, the initial parameters include the reduction value of the cut-off amount of the DFIG unit in the power system when the cut-off plan is adjusted, the increase value of the cut-off amount of the SCIG unit, and the initial cut-off amount of the DFIG unit and the initial cut-off amount of SCIG units; establish a dual-objective cut-off model with the goal of maximizing the power system transient energy cut-off index and line power oscillation damping ratio; perform fuzzy calculation on the double-objective cut-off model and add weight coefficients to obtain a dual-objective cut-off model Target weighted fuzzy transient cut-off model; adjust the weight coefficient, and obtain the distribution results of DFIG unit cut-off amount and SCIG unit cut-off amount by calculating the double-objective weighted fuzzy transient cut-off model. The invention can be widely used in the transient machine cut-off control of wind power bases.

Description

A control method for transient shutdown of external wind power bases containing different types of wind turbines

technical field

The invention relates to the technical field of wind power grid connection, in particular to a control method for transient shutdown of wind power bases with different types of wind turbines.

Background technique

With the continuous construction of nine 10-million-kilowatt-level wind power bases planned by the state, on the one hand, the penetration rate of wind power installed capacity in the power system has been continuously improved, and on the other hand, a wind power base has formed a pattern of different types of wind power units. , there are many large wind power bases that mainly use Squirrel Cage Induction Generators (Squirrel Cage Induction Generators: SCIG) in the initial construction and gradually shift to large-scale use of Double Fed Induction Generators (Double Fed Induction Generators, DFIG). However, most of these wind power bases are located in a relatively remote location, and their local consumption capacity is small. Large-scale fluctuating wind power is often sent to other regional power grids for consumption by adopting the method of "wind power and thermal power bundling". The phased construction of wind power bases and the acceleration of external delivery projects not only bring economic benefits, but also affect the transient stability of the power system. As for the wind-fire bundling delivery system, not only the transmission capacity of the traditional long-distance delivery channel is weak, the acceleration energy of the conventional thermal power unit is too large, but also the voltage support capability of the wind farm is too weak to further reduce the transmission capacity of the delivery system, and The problem of acceleration instability of the wind turbine itself. Moreover, different types of wind turbines have different characteristics in the transient process, and they will affect each other at the same time, making the transient stability of the power system more complicated and serious.

After a serious fault in the power system, the shutdown control is usually adopted to improve the transient stability. However, when only conventional thermal power units are cut off, on the one hand, problems such as the weakening of the power transmission capacity of the external transmission system caused by the weak voltage support capacity of the wind farm and the acceleration instability of conventional thermal power units and wind power units themselves cannot be well resolved. On the one hand, it will also lead to a large wind power penetration rate in the remaining grid, and a significant decrease in the system damping ratio, which will seriously affect the system oscillation recovery process. It can be seen that the traditional measures of simply removing thermal power units are difficult to ensure the stable restoration of the power system including wind power, and it is necessary to study and coordinate the removal of a certain amount of wind power units. However, different types of fans are different in their own stability, damping characteristics and impact on the system. How to coordinate different types of wind turbines and thermal power units and formulate an effective cut-off plan is of great significance to ensure the stable operation of wind power connected to the power system.

At present, there are few studies on the impact of wind turbine shutdown and shutdown decision. The literature "Research on the Impact of Wind Farm Grid-connected on Isolated Grid High-frequency Shutdown" (Power Grid Technology, 2012, 36(01):58-64) studies the transient process and safety control of isolated grid systems with wind farms running after faults According to the operation situation of the device, a high-frequency cut-off strategy including wind farms is proposed in principle; the literature "Study on Measures for Cut-off of Wind Turbine Units under Large-scale Wind Power Connection" (Proceedings of the Chinese Society for Electrical Engineering, 2011, 31(19): 25-36 ) points out that the acceleration energy obtained by the conventional thermal power unit is greater than that of the wind power unit, and the cut-off capacity of the thermal power unit should be appropriately increased. At the same time, it is pointed out that in order to ensure the ability of the thermal power unit to control the system frequency and voltage after the failure, the wind turbine unit should be properly cut off; the literature " Transient Stability Shutdown Control of Wind-fired Bundling Delivery System" (Power Grid Technology, 2013, 37(02):514-519) analyzed in detail the differences in the transient characteristics of wind turbines and thermal power generators and their respective influences on the transient stability of the system. Influenced by the thermal power unit and the wind power unit cut-off optimization scheme is proposed. However, most of the above-mentioned literatures only put forward the principled scheme, and rarely involve the quantitative research on the transient stability of the removed wind turbines. The literature "Wind Power Grid-connected Transient Optimal Shutdown Control Based on Improved Branch Transient Energy Function" (Power System Protection and Control, 2014, 42(18):72-77) pointed out that in the emergency control of wind power grid-connected system Considering the coordination of wind power and thermal power units cut-off ratio, and taking the minimum bus voltage fluctuation after cut-off as the objective function, an optimal cut-off decision model considering wind turbines is proposed. But the research object is only for the same type of wind turbines, and the stability of the wind turbines is not considered. Therefore, in order to comprehensively solve the above problems, a transient shutdown control method for the external wind power base with different types of fans is needed to effectively improve the stability of the system.

Contents of the invention

In view of the above problems, the purpose of the present invention is to provide a method that fully considers the improvement effect of the current swing times of the power system and the recovery process of line power oscillation when arranging the cut-off of SCIG units and DFIG units in the wind power base, and effectively improves the safety and stability of the system operation. Transient shutdown control method for external wind power bases with different types of wind turbines.

In order to achieve the above object, the present invention adopts the following technical solutions: a control method for transient shutdown of external wind power bases containing different types of fans, which includes the following steps:

1) Calculate the total power shedding P _z required by the power system under transient stability constraints and the thermal power shedding P _h of the power system under the optimal wind-to-heat ratio shedding;

2) Parameter initialization, the initial parameters include the decrease or increase value of DFIG unit cut-off value ΔP _w1 , the increase or decrease value of SCIG unit cut-off value ΔP _w2 , the initial cut-off value of DFIG unit in the power system when the cut-off scheme is adjusted P _w1 and SCIG unit initial cutting capacity P _w2 ;

3) Establish a dual-objective shutdown model with the goal of maximizing the transient energy shutdown index of the power system and the line power oscillation damping ratio;

4) Carry out fuzzy calculation on the dual-objective cut-off model and add weight coefficients to obtain a double-objective weighted fuzzy transient cut-off model;

5) Adjust the weight coefficient in the double-objective weighted fuzzy transient cut-off model, and obtain the distribution results of the cut-off amount of DFIG unit and SCIG unit by calculating the double-objective weighted fuzzy transient cut-off model.

In the step 1), the power system under the constraints of transient stability requires a total cut-off capacity _Pz of K times the difference between the power before the accident of the AC section at the sending end of the power system and the transmission power difference of the transient stability limit, and the proportional coefficient K is The value is determined by the grid structure and its operation mode in the power system, and the value of K ranges from 5 to 10.

In the step 2), when adjusting the cut-off scheme, the reduction or increase value of the cut-off amount of the DFIG unit in the power system ΔP _w1 , the increase or decrease value of the cut-off amount of the SCIG unit ΔP _w2 , the initial cut-off amount of the DFIG unit P The relationship between _w1 and the initial cut-off amount P _w2 of the SCIG unit is as follows:

ΔP _w1 = ΔP _w2 ;

P _w1 =P _w2 =(P _z -P _h )/2.

In said step 3), the dual-objective machine-cutting model with the target of the transient energy cut-off index of the power system and the line power oscillation damping ratio as the maximum is as follows:

minf ₁ (P _w1 , P _w2 )=-I′;

minf ₂ (P _w1 , P _w2 ) = -ζ;

In the formula, minf ₁ (P _w1 , P _w2 ) is the minimum value of the negative value of the transient energy cut-off index of the power system after the wind power base cuts off; I′ is the transient energy cut-off index of the power system after the wind power base cuts off ;-I′ is the negative value of the transient energy cut-off index of the power system after the wind power base cuts off; minf ₂ (P _w1 , P _w2 ) is the minimum negative value of the line power oscillation damping ratio of the power system after the wind power base cuts off value; ζ is the line power oscillation damping ratio of the power system after the wind power base is switched off; -ζ is the negative value of the line power oscillation damping ratio of the power system after the wind power base is switched off;

Among them, the constraints of the bi-objective cutting machine model include:

① The constraint conditions of machine cutting quantity control are:

P _h +P _w1 +P _w2 =P _z ;

② The static security constraints are:

u _min ≤ u ≤ u _max ;

| _Pb | _≤Pbmax ;

In the formula, u is the voltage of all buses in the power system after the wind power base is switched off, u _min and u _max are the upper limit and lower limit of the voltage of all buses in the power system after the wind power base is switched off; |P _b | is the size value of the power flow of all lines in the power system after the wind power base is switched off, and P _bmax is the constraint value of the power flow of all lines in the power system after the wind power base is switched off.

In said step 3), the calculation of the transient energy cut-off index I' of the power system after the wind power base cuts off includes the following steps:

(1) To calculate the transient kinetic energy V _KE of the power system, the calculation formula is:

In the formula, n is a positive integer, i represents the i-th generator, M _i is the moment of inertia of the i-th generator, ω _i is the angular velocity of the i-th generator, where the moment of inertia of the i-th generator and The angular velocity of the i-th generator is the per unit value under the system inertial center coordinates;

(2) The power system triggers the cut-off control measure u at time t _ec after the fault. After that, the transient kinetic energy V _KE (u,t) of the power system at time t is:

V _KE (u,t)=V _KE (0,t)+ΔE _K (u,t); t∈(t _ec ,t _ec +Δt);

In the formula, t is a moment after triggering the cut-off control measure u; _Δt is a period of time after the cut-off control measure u is implemented; ΔE _K (u, t) is the disturbance term of the power system’s transient kinetic energy at time t by the cut-off control measure u.

(3) The calculation formula of the disturbance term ΔE _K (u, t) of the transient kinetic energy of the power system by the control measure u at time t is as follows:

In the formula, ΔE _kH (u, t) is the disturbance item of the power cut control measure u on the transient kinetic energy of the thermal power unit in the power system at time t, and ΔE _kW (u, t) is the power cut control measure u’s effect on the power system The disturbance term of the transient kinetic energy of the SCIG unit at time t, V _KEH (0, t) is the transient kinetic energy of thermal power units in the power system at time t when the control measure u is not triggered; V _KEW (0, t) is The transient kinetic energy of the SCIG units in the power system at time t when the shutdown control measure u is not triggered; V _KEH (u,t) is the transient kinetic energy of thermal power units in the power system at time t after the shutdown control measure u is triggered; V _KEW (u, t) is the transient kinetic energy of _{the SCIG} unit in the power system at time t after triggering the cut-off control measure u; and the acceleration power of the thermal power unit in the power system that triggered the shutdown control measure u; P _WACC,i and P' _WACC,i are the SCIG units that did not trigger the shutdown control measure u and triggered the shutdown control measure u in the COI coordinates, respectively Acceleration power; ΔE _kH (t _ec ) is the reduction in kinetic energy of thermal power units after shutdown; ΔE _kW (t _ec ) is the reduction in kinetic energy of SCIG units after shutdown; GH is the number of generators in thermal power units; GW is SCIG the number of generators in the unit;

(4) The calculation formula of the transient energy cut-off index I′ after power system cut-off is:

I'＝first Max or Min ΔE _K (u,t)/V _KE (u,t),t∈(t _ec ,t _ec +Δt);

Among them, first Max or Min ΔE _K (u,t) refers to the first extremum of the transient kinetic energy disturbance term ΔE _K (u,t) of the power system after the shutdown control measure u is triggered.

In described step 4), the expression of the double-objective weighted fuzzy transient shear model containing weight coefficient is as follows:

In the _formula , β1 is the weight coefficient with the smallest negative value of the transient energy cut _- off index of the power system after the wind power base is switched off, and β2 is the weight coefficient with the smallest negative value of the line power oscillation damping ratio of the power system after the wind power base is switched off, λ1 is the degree _of membership that satisfies the power system transient energy cut-off control index and its corresponding constraint conditions, that is, the maximum satisfaction degree of the transient energy cut-off control index _; The degree of membership of the constraints, that is, the maximum satisfaction of the line power oscillation damping ratio, max(β ₁ λ ₁ +β ₂ λ ₂ ) represents the maximum value of β ₁ λ ₁ +β ₂ λ ₂ ; c ₀₁ is when the wind power base cuts When the negative value of the transient energy cut-off index of the power system after the wind power system is the smallest, the negative value of the transient energy cut-off index of the power system is the smallest; when the negative value of the line power oscillation damping ratio of the power system after the wind power base is cut off, c ₀₂ is When the negative value of the line power oscillation damping ratio of the power system after the wind power base is switched off is the smallest, the line power oscillation _{damping ratio} of the power system is negative; The expansion and contraction of the negative value of the line power oscillation damping ratio of the system; u is the voltage of all buses in the power system after the wind power base is switched off, and u _min and u _max are the upper limit of the voltage of all buses in the power system after the wind power base is switched off value and lower limit; |P _b | is the size value of the power flow of all lines in the power system after the wind power base is switched off, and P _bmax is the constraint value of the power flow of all lines in the power system after the wind power base is switched off.

In said step 4), the fuzzy calculation is carried out to the dual-objective cut-off model to obtain the double-objective weighted fuzzy transient cut-off model containing weight coefficients, including the following steps:

(1) In the process of controlling the cut-off of wind power bases, reduce the cut-off capacity of DFIG units according to the decrease value of cut-off capacity of DFIG units ΔP _w1 , and increase the cut-off capacity of SCIG units according to the increase value of cut-off capacity of SCIG units ΔP _w2 After measuring, when the negative value of the transient energy cut-off index of the power system is the smallest after the wind power base cuts off, calculate the negative value of the transient energy cut-off index c ₀₁ and the negative value of the line power oscillation damping ratio c ₀₂ ′ of the power system at this time , and at this time the cut-off capacity of the DFIG unit and the cut-off capacity of the SCIG unit;

(2) Starting from the initial cut-off capacity again, increase the cut-off capacity of DFIG units according to the increase value of cut-off capacity of DFIG units ΔPw1, and reduce the cut-off capacity of SCIG units according to the decrease value of cut-off capacity of SCIG units ΔPw2, when the wind power base When the negative value of the line power oscillation damping ratio of the power system after shutdown is the smallest, calculate the transient energy shutdown index c ₀₁ ′ and the line power oscillation damping ratio negative value c ₀₂ of the power system at this time, and the DFIG unit cut-off at this time Capacity and cut-off capacity of SCIG units;

(3) According to the different requirements for the negative value of the transient energy cut-off index of the power system and the negative value of the line power oscillation damping ratio in the cut-off control, determine the expansion and contraction δ ₀₁ and the negative value of the transient energy cut-off index of the power system The stretching amount δ ₀₂ of the negative value of the line power oscillation damping ratio; among them, the stretching amount δ ₀₁ of the negative value of the transient energy cut-off index and the stretching amount δ ₀₂ of the negative value of the line power oscillation damping ratio meet the following conditions:

c ₀₁ +δ ₀₁ <c ₀₁ ′;

c ₀₂ +δ ₀₂ <c ₀₂ ′;

(4) Determine the expressions of the objective membership functions μ[f ₁ (x)] and μ[f ₂ (x)] of the dual-objective cut-off model as follows:

In the formula, x=[P _w1 , P _w2 ] ^T , T represents the transfer rank; f ₁ (x) is the negative value of the transient energy cut-off index of the power system after the wind power base cuts off; f ₂ (x) is the wind power base Negative value of line power oscillation damping ratio of power system after machine cut-off;

(5) According to the different requirements for the minimum negative value of the transient energy shutdown index and the minimum negative value of the line oscillation damping ratio of the power system after the wind power base is switched off, the weight coefficient of each target is determined to obtain the dual-objective weighting Fuzzy transient model, the expression is as follows:

Due to the adoption of the above technical scheme, the present invention has the following advantages: the present invention uses the power system transient energy cut-off control index to characterize the current swing improvement effect, and the line power oscillation damping ratio change to characterize the system oscillation recovery speed, taking into account at the same time Based on the conflict between the two objectives of transient energy cut-off control index and line power oscillation damping ratio, a dual-objective weighted fuzzy cut-off model was established by using multi-objective decision-making theory, and a weight factor was introduced. According to the requirements of different large wind power bases, each target Different weight coefficients are set so that when arranging the cut-off of SCIG units and DFIG units in the wind power base, the current swing improvement effect of the power system and the recovery speed of line power oscillation can be fully considered. Under the premise of ensuring transient stability, different The optimal cut-off ratio of different types of wind power can better solve the conflicting multi-objective optimization problem in the cut-off control of wind power bases, meet different stability requirements, and effectively improve the safety and stability of system operation. To sum up, the present invention can be widely used in the transient control of wind power base cut-off.

Description of drawings

Fig. 1 is a schematic flow chart of the present invention

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, the present invention provides a control method for transient shutdown of an external wind power base containing different types of fans, including the following steps:

1) Calculate the total power shedding P _z required by the power system under transient stability constraints and the power shedding P _h of the thermal power unit under the optimal wind-to-heat ratio shedding.

Among them, under the constraints of transient stability, the total power cut-off required by the power system P _z is K times the difference between the power before the accident of the AC section at the sending end of the power system and the transmission power of the transient stability limit, and the value of the proportional coefficient K is determined by the power system It is determined by the grid structure and its operation mode in the grid, and the value range of K is 5-10.

2) Parameter initialization, the initial parameters include the decrease or increase value of DFIG unit cut-off value ΔP _w1 , the increase or decrease value of SCIG unit cut-off value ΔP _w2 , the initial cut-off value of DFIG unit in the power system when the cut-off scheme is adjusted P _w1 and the initial cut-off amount P _w2 of the SCIG unit.

Wherein, ΔP _w1 =ΔP _w2 ; P _w1 =P _w2 =(P _z -P _h )/2.

3) Establish a dual-objective shutdown model aiming at the transient energy shutdown index of the power system and the maximum line power oscillation damping ratio as follows:

minf ₁ (P _w1 , P _w2 )=-I′ (1)

minf ₂ (P _w1 , P _w2 )=-ζ(2)

In the formula, minf ₁ (P _w1 , P _w2 ) is the minimum value of the negative value of the transient energy cut-off index of the power system after the wind power base cuts off; I′ is the transient energy cut-off index of the power system after the wind power base cuts off ;-I′ is the negative value of the transient energy cut-off index of the power system after the wind power base cuts off; minf ₂ (P _w1 , P _w2 ) is the minimum negative value of the line power oscillation damping ratio of the power system after the wind power base cuts off value; ζ is the line power oscillation damping ratio of the power system after the wind power base is switched off; -ζ is the negative value of the line power oscillation damping ratio of the power system after the wind power base is switched off.

Among them, the constraints of the bi-objective cutting machine model include:

① The constraint conditions of machine cutting quantity control are:

P _h +P _w1 +P _w2 =P _z (3)

② The static security constraints are:

u _min ≤ u ≤ u _max (4)

|P _b |≤P _bmax (5)

In the formula, u is the voltage of all buses in the power system after the wind power base is switched off, u _min and u _max are the upper limit and lower limit of the voltage of all buses in the power system after the wind power base is switched off; |P _b | is the size value of the power flow of all lines in the power system after the wind power base is switched off, and P _bmax is the constraint value of the power flow of all lines in the power system after the wind power base is switched off.

Among them, the calculation of the transient energy shutdown index I′ of the power system after the wind power base shutdown includes the following steps:

(1) To calculate the transient kinetic energy V _KE of the power system, the calculation formula is:

In the formula, n is a positive integer, i represents the i-th generator, M _i is the moment of inertia of the i-th generator, ω _i is the angular velocity of the i-th generator, where the moment of inertia of the i-th generator and The angular velocity of the i-th generator is p.u. in the coordinates of the center of inertia (COI) of the system.

(2) The power system triggers the cut-off control measure u at time t _ec after the fault. After that, the transient kinetic energy V _KE (u,t) of the power system at time t is:

V _KE (u,t)=V _KE (0,t)+ΔE _K (u,t); t∈(t _ec ,t _ec +Δt) (7)

In the formula, t is a moment after triggering the cut-off control measure u; _Δt is a period of time after the cut-off control measure u is implemented; ΔE _K (u, t) is the disturbance term of the power system’s transient kinetic energy at time t by the cut-off control measure u.

(3) The calculation formula of the disturbance term ΔE _K (u, t) of the transient kinetic energy of the power system by the control measure u at time t is as follows:

In the formula, ΔE _kH (u, t) is the disturbance item of the power cut control measure u on the transient kinetic energy of the thermal power unit in the power system at time t, and ΔE _kW (u, t) is the power cut control measure u’s effect on the power system The disturbance term of the transient kinetic energy of the SCIG unit at time t, V _KEH (0, t) is the transient kinetic energy of thermal power units in the power system at time t when the control measure u is not triggered; V _KEW (0, t) is The transient kinetic energy of the SCIG units in the power system at time t when the shutdown control measure u is not triggered; V _KEH (u,t) is the transient kinetic energy of thermal power units in the power system at time t after the shutdown control measure u is triggered; V _KEW (u, t) is the transient kinetic energy of _{the SCIG} unit in the power system at time t after triggering the cut-off control measure u; and the acceleration power of the thermal power unit in the power system that triggered the shutdown control measure u; P _WACC,i and P' _WACC,i are the SCIG units that did not trigger the shutdown control measure u and triggered the shutdown control measure u in the COI coordinates, respectively Acceleration power; ΔE _kH (t _ec ) is the reduction in kinetic energy of thermal power units after shutdown; ΔE _kW (t _ec ) is the reduction in kinetic energy of SCIG units after shutdown; GH is the number of generators in thermal power units; GW is SCIG Number of generators in the unit.

(4) The calculation formula of the transient energy cut-off index I′ after power system cut-off is:

I′＝first Max or Min ΔE _K (u,t)/V _KE (u,t),t∈(t _ec ,t _ec +Δt) (9)

Among them, first Max or Min ΔE _K (u,t) refers to the first extremum of the transient kinetic energy disturbance term ΔE _K (u,t) of the power system after the shutdown control measure u is triggered.

4) Carry out fuzzy calculation on the dual-objective cut-off model and add weight coefficients to obtain a double-objective weighted fuzzy transient cut-off model, including the following steps:

(1) In the process of controlling the cut-off of wind power bases, reduce the cut-off capacity of DFIG units according to the decrease value of cut-off capacity of DFIG units ΔP _w1 , and increase the cut-off capacity of SCIG units according to the increase value of cut-off capacity of SCIG units ΔP _w2 After measuring, when the negative value of the transient energy cut-off index of the power system is the smallest after the wind power base cuts off, calculate the negative value of the transient energy cut-off index c ₀₁ and the negative value of the line power oscillation damping ratio c ₀₂ ′ of the power system at this time , as well as the cut-off capacity of DFIG unit and the cut-off capacity of SCIG unit at this time.

(2) Starting from the initial cut-off capacity again, increase the cut-off capacity of DFIG units according to the increase value of cut-off capacity of DFIG units ΔPw1, and reduce the cut-off capacity of SCIG units according to the decrease value of cut-off capacity of SCIG units ΔPw2, when the wind power base When the negative value of the line power oscillation damping ratio of the power system after shutdown is the smallest, calculate the transient energy shutdown index c ₀₁ ′ and the line power oscillation damping ratio negative value c ₀₂ of the power system at this time, and the DFIG unit cut-off at this time Machine capacity and cut-off capacity of SCIG units.

(3) According to the different requirements for the negative value of the transient energy cut-off index of the power system and the negative value of the line power oscillation damping ratio in the cut-off control, determine the expansion and contraction δ ₀₁ and the negative value of the transient energy cut-off index of the power system The expansion and contraction δ ₀₂ of the negative value of the line power oscillation damping ratio. Among them, the stretching amount δ ₀₁ of the negative value of the transient energy cut-off index and the stretching amount δ ₀₂ of the negative value of the line power oscillation damping ratio satisfy the following conditions:

c ₀₁ +δ ₀₁ <c ₀₁ ′ (10)

c ₀₂ +δ ₀₂ <c ₀₂ ′ (11)

(4) Determine the expressions of the objective membership functions μ[f ₁ (x)] and μ[f ₂ (x)] of the dual-objective cut-off model as follows:

In the formula, x=[P _w1 , P _w2 ] ^T , T represents the transfer rank; f ₁ (x) is the negative value of the transient energy cut-off index of the power system after the wind power base cuts off; f ₂ (x) is the wind power base The line power oscillation damping ratio of the power system after the shutdown is negative.

(5) According to the different requirements for the minimum negative value of the transient energy shutdown index and the minimum negative value of the line oscillation damping ratio of the power system after the wind power base is switched off, the weight coefficient of each target is determined to obtain the dual-objective weighting Fuzzy transient model, the expression is as follows:

In the _formula , β1 is the weight coefficient with the smallest negative value of the transient energy cut _- off index of the power system after the wind power base is switched off, and β2 is the weight coefficient with the smallest negative value of the line power oscillation damping ratio of the power system after the wind power base is switched off, λ1 is the degree _of membership that satisfies the power system transient energy cut-off control index and its corresponding constraint conditions, that is, the maximum satisfaction degree of the transient energy cut-off control index _; The degree of membership of the constraints, that is, the maximum satisfaction of the line power oscillation damping ratio, max(β ₁ λ ₁ +β ₂ λ ₂ ) represents the maximum value of β ₁ λ ₁ +β ₂ λ ₂ .

5) Adjust the weight coefficient in the dual-objective weighted fuzzy transient cut-off model, and obtain the distribution results of the cut-off capacity of DFIG units and SCIG units by calculating the double-objective weighted fuzzy transient cut-off model.

Example

The CIGRE B4-39 wind farm grid-connected system is used for analysis. The generator in the system adopts a detailed model and considers the voltage regulation and speed regulation system. The wind-fire bundling ratio is 1:1.57, and the load adopts 70% constant impedance and 30% constant power static model. Assuming that a three-phase short-circuit fault occurs on one of the outgoing double-circuit lines at the 100th cycle, after 0.32s, the outgoing faulty line is disconnected and the fault is cleared. Follow the steps of the above-mentioned transient shutdown control method for the outgoing wind power base. The CIGRE B4-39 wind farm grid-connected system is calculated, and the results are shown in Table 1.

Table 1 Target values calculated under different weight coefficients

It can be seen from Table 1 that when (β ₁ , β ₂ )=(1.0,0.0), the transient energy cut-off control index I′ of the power system after the wind power base cut-off is the largest, and the effect of improving the current swing is the best at this time. When (β ₁ , β ₂ ) = (0.0, 1.0), the line power oscillation damping ratio ζ of the power system after the wind power base is switched off is the largest, and the line power oscillation recovery process is the fastest at this time.

After the wind power base is cut off, the transient energy cut-off control index I′ of the power system and the line power oscillation damping ratio ζ will increase with the increase of their corresponding weights. In practical application, the weight coefficient can be adjusted according to the importance of each goal, which is more pertinent and applicable to the problem solving. When the model focuses on the transient energy cut-off control index I′ of the power system after the wind power base cuts off, adjust the weight coefficient so that the negative value of the transient energy cut-off index of the power system after the wind power base cuts off is the weight coefficient β ₁ When the model is biased towards the line power oscillation damping ratio ζ of the power system after the wind power base is cut, adjust the weight coefficient so that the line power oscillation damping ratio of the power system after the wind power base is cut is negative The minimum weight coefficient β ₂ is too large, and the capacity of DFIG unit increases. When the method of the present invention is used to control the transient cut-off of the external wind power base, different weight coefficients can be set according to the requirements of different wind power bases, and the improvement effect of the current swing times of the power system can be considered when arranging the cut-off amount of the SCIG unit and the DFIG unit in the wind power base And the line power oscillation recovery process is faster, which fully reflects the multi-factor fairness.

The above-mentioned embodiments are only used to illustrate the present invention, wherein the structure, connection mode and manufacturing process of each component can be changed to some extent, and any equivalent transformation and improvement carried out on the basis of the technical solution of the present invention should not excluded from the protection scope of the present invention.

Claims (6)

1. a kind of wind power base transient state of sending outside containing different type blower fan cuts machine control method, and it is comprised the following steps：

1) calculating is out of order, and lower power system is required under Transient Stability Constraints always to cut machine amount P_zWith power system in optimization air-gas ratio The fired power generating unit that example is cut in the case of machine cuts machine amount P_h；

2) parameter initialization, DFIG units cut machine amount decreasing value or increasing in power system when initial parameter cuts machine scheme including adjustment Value added Δ P_w1, SCIG units cut machine amount value added or decreasing value Δ P_w2, DFIG units initially cut machine amount P_w1It is initial with SCIG units Cut machine amount P_w2；

3) set up and machine index and line power oscillation damping are cut than being the Bi-objective of target to the maximum with the transient state energy of power system Cut machine model；

The step 3) in machine index and line power oscillation damping are cut than being target to the maximum with the transient state energy of power system It is as follows that Bi-objective cuts machine model：

min f₁(P_w1, P_w2)=- I '；

min f₂(P_w1, P_w2)=- ζ；

In formula, min f₁(P_w1,P_w2) minimum value of machine index negative value is cut for the transient state energy that wind power base cuts power system after machine； I ' cuts machine index for the transient state energy that wind power base cuts power system after machine；- I ' cuts the temporary of power system after machine for wind power base State energy cuts the negative value of machine index；min f₂(P_w1,P_w2) the line power oscillation damping of power system after machine is cut for wind power base Than the minimum value of negative value；ζ cuts the line power oscillation damping ratio of power system after machine for wind power base；- ζ cuts machine for wind power base Afterwards the line power oscillation damping of power system than negative value；

Wherein, Bi-objective is cut the constraints of machine model and is included：

1. cutting machine amount control constraints condition is：

P_h+P_w1+P_w2=P_z；

2. Static Security Constraints condition is：

u_min≤u≤u_max；

|P_b|≤P_bmax；

In formula, u cuts the voltage of all buses in power system after machine, u for wind power base_minAnd u_maxRespectively wind power base cuts machine Afterwards in power system the voltage of all buses higher limit and lower limit；|P_b| cut after machine for wind power base and owned in power system The sizes values of Line Flow, P_bmaxThe binding occurrence of all Line Flows in power system after machine is cut for wind power base；

4) machine model is cut to Bi-objective to carry out obfuscation and calculates and add weight coefficient to obtain the fuzzy transient state of Two-Weighted-Objective to cut machine Model；

5) the fuzzy transient state of adjustment Two-Weighted-Objective cuts the weight coefficient in machine model, and machine is cut by the fuzzy transient state of Two-Weighted-Objective Model calculate and obtains DFIG units and cut machine amount and SCIG units cut the allocation result of machine amount.

2. a kind of wind power base transient state of sending outside containing different type blower fan as claimed in claim 1 cuts machine control method, its It is characterised by：The step 1) in, power system is required under Transient Stability Constraints always to cut machine amount P_zFor power system sending end is handed over K times of power and transient stability limit transimission power difference before flow section accident, the value of Proportional coefficient K is by power system Electric network composition and its method for operation determine that the span of K is 5~10.

3. a kind of wind power base transient state of sending outside containing different type blower fan as claimed in claim 1 cuts machine control method, its It is characterised by：The step 2) in, DFIG units cut machine amount decreasing value or value added Δ in power system when machine scheme is cut in adjustment P_w1, SCIG units cut machine amount value added or decreasing value Δ P_w2, DFIG units initially cut machine amount P_w1Machine amount is initially cut with SCIG units P_w2Relation it is as follows：

ΔP_w1=Δ P_w2；

P_w1=P_w2=(P_z-P_h)/2。

4. a kind of wind power base transient state of sending outside containing different type blower fan as claimed in claim 1 cuts machine control method, its It is characterised by：The step 3) in, the transient state energy that wind power base cuts power system after machine is cut the calculating of machine index I ' and is included such as Lower step：

(1) the transient state kinetic energy V of power system is calculated_KE, computing formula is：

In formula, n is positive integer, and i represents i-th generator, M_iIt is i-th rotary inertia of generator, ω_iIt is i-th generator Angular speed, wherein, the rotary inertia of i-th generator and the angular speed of i-th generator are and are sat at system inertia center Perunit value under mark；

(2) power system t after a failure_ecTime trigger cuts machine control measure u, and hereafter, power system is moved in the transient state of t Can V_KE(u, t) is：

V_KE(u, t)=V_KE(0,t)+ΔE_K(u,t)；t∈(t_ec,t_ec+Δt)；

In formula, t is that the moment after machine control measure u is cut in triggering；Δ t is to cut a period of time after machine control measure u is implemented；V_KE (0, it is t) not trigger transient state kinetic energy of the power system in t when cutting machine control measure u；ΔE_K(u, t) is to cut machine control measure U to power system the transient state kinetic energy of t disturbance term,

(3) cut machine control measure u to power system the transient state kinetic energy of t disturbance term Δ E_KThe computing formula of (u, t) is such as Under：

In formula, Δ E_kH(u, t) be cut machine control measure u to fired power generating unit in power system the transient state kinetic energy of t disturbance , Δ E_kW(u, t) be cut machine control measure u to SCIG units in power system the transient state kinetic energy of t disturbance term, V_KEH (0, it is t) not trigger when cutting machine control measure u transient state kinetic energy of the fired power generating unit in t in power system；V_KEW(0, t) for not Transient state kinetic energy of the SCIG units in t in power system when machine control measure u is cut in triggering；V_KEH(u, t) cuts machine control for triggering Transient state kinetic energy of the fired power generating unit in t in power system after measure u；V_KEW(u, t) cuts electric power after machine control measure u for triggering Transient state kinetic energy of the SCIG units in t in system；P_ACC,iAnd P'_ACC,iMachine of cutting is not triggered under COI coordinates respectively to control to arrange Apply u and trigger the accelerating power of the power system fired power generating unit for cutting machine control measure u；P_WACC,iAnd P'_WACC,iRespectively sat in COI The accelerating power cut machine control measure u and trigger the SCIG units for cutting machine control measure u is not triggered under mark；ΔE_kH(t_ec) it is fire Group of motors cuts the decrement of kinetic energy after machine；ΔE_kW(t_ec) decrement of kinetic energy after machine is cut for SCIG units；GH is in fired power generating unit The number of generator；GW is the number of generator in SCIG units；

(4) computing formula that the transient state energy after Shedding In Power System cuts machine index I ' is：

I '=first Max or Min Δs E_K(u,t)/V_KE(u,t),t∈(t_ec,t_ec+Δt)；

Wherein, first Max or Min Δs E_K(u, t) refers to that triggering is cut the transient state kinetic energy of power system after machine control measure u and disturbed Dynamic item Δ E_KFirst extreme value of (u, t).

5. a kind of wind power base transient state of sending outside containing different type blower fan as claimed in claim 1 cuts machine control method, its It is characterised by：The step 4) in, the expression formula that the fuzzy transient state of the Two-Weighted-Objective containing weight coefficient cuts machine model is as follows：

In formula, β₁For the transient state energy that wind power base cuts power system after machine cuts the minimum weight coefficient of machine index negative value, β₂It is wind Cut the weight coefficient of the line power oscillation damping than negative value minimum of power system after machine, λ in electric base₁It is temporary to meet power system State energy cuts the maximum satisfaction that the degree of membership of machine Con trolling index and its corresponding constraints, i.e. transient state energy cut machine Con trolling index Degree；λ₂To meet circuit on power system damping of power oscillation than target and its degree of membership of corresponding constraints, i.e. line power Oscillation damping than maximum satisfaction, max (β₁λ₁+β₂λ₂) represent β₁λ₁+β₂λ₂Maximum；c₀₁It is after wind power base cuts machine The transient state energy of power system cuts machine index negative value when the transient state energy of power system cuts machine index negative value minimum；Work as wind power base Cut power system after machine line power oscillation damping it is more minimum than negative value when, c₀₂It is the line of power system after wind power base cuts machine The line power oscillation damping of power system compares negative value when road damping of power oscillation is than negative value minimum；δ₀₁It is the transient state of power system Energy cuts the stroke of machine index negative value；δ₀₂It is the stroke of the line power oscillation damping than negative value of power system；U is wind-powered electricity generation Cut the voltage of all buses in power system after machine, u in base_minAnd u_maxRespectively wind power base is cut after machine and is owned in power system The higher limit and lower limit of the voltage of bus；|P_b| the size of all Line Flows in power system after machine is cut for wind power base Value, P_bmaxThe binding occurrence of all Line Flows in power system after machine is cut for wind power base.

6. a kind of wind power base transient state of sending outside containing different type blower fan as claimed in claim 5 cuts machine control method, its It is characterised by：The step 4) in, machine model is cut to Bi-objective carries out obfuscation calculating Bi-objective of the acquisition containing weight coefficient Weighted Fuzzy transient state cuts machine model, comprises the following steps：

(1) during carrying out cutting machine control to wind power base, machine amount decreasing value Δ P is cut by DFIG units_w1Reduce DFIG machines Group cuts machine amount, while cutting machine amount value added Δ P by SCIG units_w2After increase SCIG units cut machine amount, after wind power base cuts machine When the transient state energy of power system cuts machine index negative value minimum, the transient state energy for calculating now power system cuts machine index negative value c₀₁ With line power oscillation damping than negative value c₀₂', and now DFIG units cut machine amount and SCIG units cut machine amount；

(2) again since initially machine amount is cut, machine amount value added Δ Pw1 increase DFIG units are cut by DFIG units and cuts machine amount, together When cut machine amount decreasing value Δ Pw2 by SCIG units and reduce after SCIG units cut machine amount, power system after wind power base cuts machine When line power oscillation damping is more minimum than negative value, the transient state energy for calculating now power system cuts machine index negative value c₀₁' and circuit Damping of power oscillation is than negative value c₀₂, and now DFIG units cut machine amount and SCIG units cut machine amount；

(3) cut machine index negative value to the transient state energy of power system and line power oscillation damping compares negative value according to cutting in machine control It is required that difference, determine that the transient state energy of power system cuts the stroke δ of machine index negative value₀₁With line power oscillation damping than negative The stroke δ of value₀₂；Wherein, transient state energy cuts the stroke δ of machine index negative value₀₁With line power oscillation damping stretching than negative value Contracting amount δ₀₂Meet following condition：

c₀₁+δ₀₁＜ c₀₁′；

c₀₂+δ₀₂＜ c₀₂′；

(4) determine that Bi-objective cuts the target membership function mui [f of machine model₁(x)] and μ [f₂(x)] expression formula it is as follows：

In formula, x=[P_w1,P_w2]^T, T represents transposed matrix；f₁X () cuts for the transient state energy that wind power base cuts power system after machine Machine index negative value；f₂X () compares negative value for the line power oscillation damping that wind power base cuts power system after machine；

(5) cut that machine index negative value is minimum and line oscillation damping ratio according to the transient state energy that power system after machine is cut to wind power base The different requirement of negative value two targets of minimum, determines the weight coefficient of each target, so as to obtain the fuzzy transient state of Two-Weighted-Objective Machine model is cut, expression formula is as follows：