CN104362666B - A kind of wind farm low voltage cuts machine emergency control method - Google Patents

Abstract

The invention discloses a kind of wind farm low voltage and cut machine emergency control method, belong to power system safety and stability and control technical field, the method includes: according to wind farm grid-connected some short circuit current, estimate from and the equivalent reactance of the site thevenin equivalent circuit of power system depending on entering；Monitor wind farm grid-connected point voltage and the active power of wind energy turbine set injection power system, estimate equivalent source voltage；According to equivalent source voltage and equivalent reactance, calculate the voltage stability limit power of wind farm grid-connected some injected system；Calculate current power and the ratio of power limit, and compare with the threshold value being previously set, represent that system voltage maintenance level is relatively low more than threshold value, take to excise the measure of Wind turbines.The present invention estimates the voltage stability limit of wind farm grid-connected some injecting power in real time, and compares with current power, it is judged that the Voltage Stability Level of system, takes to cut machine measure, improve reasonability and the effectiveness of low crush-cutting machine emergent control during close to Voltage Instability.

Description

A kind of wind farm low voltage cuts machine emergency control method

Technical field

The invention belongs to power system safety and stability and control technical field, cut machine emergent control particularly to a kind of wind farm low voltage Method.

Background technology

The characteristic of wind-powered electricity generation is different from traditional synchronous generator.Synchronous generator is due to the existence of internal magnetic linkage, in transient process Conventional electromotive force represents, the ability controlling voltage is strong.Comparing with synchronous generator, the ability that wind-powered electricity generation controls voltage is weak, but controls The ability of power is strong, can be by the regulation power of power electronic equipment fast and flexible.Voltage stabilization is that large-scale wind power is grid-connected After need issues that need special attention.When electrical network generation disturbance causes wind farm grid-connected point voltage to fall, not there is voltage support The Wind turbines of ability continues the injecting power that is incorporated into the power networks, it will the recovery having influence on line voltage even causes Voltage Instability, It is thus desirable to take to excise the measure of Wind turbines, maintain system voltage stable.

Existing wind energy turbine set is cut machine control major part and is all based on what voltage was carried out, and the most wind farm grid-connected point voltage is less than setting Value, then cut-out Wind turbines.This method implements simple and convenient, but from principle for, voltage levels is not Can accurately reflect the Voltage Stability Level of system, wind energy turbine set accesses electrical network electrical distance distance, wind energy turbine set sends watt level etc. It is all the key factor affecting voltage stabilization, only implements to cut machine by voltage levels and be difficulty with accurately controlling.

Summary of the invention

In place of it is an object of the invention to as overcoming the deficiencies in the prior art, propose a kind of wind farm low voltage and cut machine emergency methods, logical Cross judgement system voltage maintenance level and implement corresponding control strategy, safeguards system safety.

The wind farm low voltage that the present invention proposes cuts machine emergency control method, comprises the following steps:

A: ask for the thevenin equivalent circuit from the power system depending on entering of the wind farm grid-connected point, first according to wind farm grid-connected point Short circuit current I_SCEstimation equivalent reactance X_E, formula is

B: monitor wind farm grid-connected point voltage U and the active-power P of wind energy turbine set injection power system, estimation equivalent source electricity Pressure U_E, formula is $U_E=\sqrt{U^2+{\left(\frac{{\mathrm{PX}}_E}{U}\right)}^2};$

C: according to equivalent source voltage U_EWith equivalent reactance X_E, calculate the voltage stabilization pole of wind farm grid-connected some injected system Limit power P_max, formula is

$P_{\max }=\frac{{U_E}^2}{{2X}_E}=\frac{U^2}{{2X}_E}+\frac{P^2{X}_E}{{2U}^2};$

D: current power P and power limit P_maxRatio reflection system Voltage Stability Level, ratio be 1 expression voltage lose Steady critical point, ratio more small voltage stability is the best, calculates current power P and power limit P_maxRatio And and threshold value k that is previously set_th(0<k_th< 1) compare, as k ＞ k_thTime, excise Wind turbines, and use excision The gross output of blower fan reaches P-k_thP_maxDetermine the quantity of excision blower fan.

The wind farm low voltage that the present invention proposes cuts machine emergency control method, and its feature and effect are that the inventive method is according to wind-powered electricity generation Field the equivalent reactance of site short circuit current estimation thevenin equivalent circuit, and according to the wind farm grid-connected point voltage surveyed and note Enter power, the supply voltage of estimation thevenin equivalent circuit, calculate the voltage stability limit of wind farm grid-connected some injecting power, By comparing current power and power limit judges the Voltage Stability Level of system, decide whether to take to cut machine measure determining and cut Machine amount.Compared to traditional method, the inventive method can take action when systems face Voltage Instability threatens more accurately, Avoid cutting less or crossing cutting, control more rationally effectively.

Accompanying drawing explanation

Fig. 1 is the flow chart that wind farm low voltage of the present invention cuts machine emergency control method.

Detailed description of the invention

Below the detailed description of the invention of the present invention is described in further detail.Following example are used for illustrating the present invention, but not It is used for limiting the scope of the present invention.

Wind farm low voltage of the present invention cuts the principle of machine emergency control method: first estimate from wind farm grid-connected point depending on entering The thevenin equivalent circuit of power system, its equivalent reactance is basically unchanged in system dynamic course, can with and site short The approximation reciprocal of road electric current, change in dynamic process is equivalent source voltage, enters according to the electric parameters of also site actual measurement Row estimation；After estimating thevenin equivalent circuit, go out the voltage stabilization of injecting power according to the first principles computations of voltage stabilization The limit, and compare with current power, to take when system is close to the limit to cut machine control measure, the machine amount of cutting can be according to working as The difference of front power and power limit determines.

The present invention provides a kind of wind farm low voltage to cut machine emergency control method embodiment, specifically includes following steps:

A: ask for the thevenin equivalent circuit from the power system depending on entering of the wind farm grid-connected point, first according to wind farm grid-connected point Short circuit current I_SCEstimation equivalent reactance X_E, the estimation equation used in the present embodiment is

In above-mentioned steps, the calculating of wind farm grid-connected some short circuit current is a part for power system conventionally calculation, can be direct Use existing result of calculation, it is possible to use calculation of short-circuit current computed in software, then estimate equivalent reactance according to short circuit current. Equivalent reactance is a parameter of low crush-cutting machine, is not to be calculated in real time, after setting, it is only necessary to time certain Between the cycle (typical: 1 year) update this parameter.

B: monitor wind farm grid-connected point voltage U and the active-power P of wind energy turbine set injection power system, estimation equivalent source electricity Pressure U_E, the estimation equation that the present embodiment uses is

In above-mentioned steps, U and P passes through to measure in real time to obtain, the U that estimation obtains_EAlso it is real-time change.

C: according to equivalent source voltage U_EWith equivalent reactance X_E, calculate the voltage stabilization pole of wind farm grid-connected some injected system Limit power P_max, the computing formula that the present embodiment uses is:

$P_{\max }=\frac{{U_E}^2}{{2X}_E}=\frac{U^2}{{2X}_E}+\frac{P^2{X}_E}{{2U}^2};$

D: current power P and power limit P_maxRatio reflection system Voltage Stability Level, ratio be 1 expression voltage lose Steady critical point, ratio more small voltage stability is the best, ratio calculatedAnd and threshold value k that is previously set_th (0<k_th< 1) compare, as k ＞ k_thTime take excise Wind turbines measure, the gross output of institute's excision blower fan Reach P-k_thP_max, determine the quantity of excision blower fan with this.

In above-mentioned steps, threshold value k_thMargin of safety as required determines, k_thThe least, margin of safety is the biggest, but controls more Conservative, typically, k_thIt is taken as 0.8；The quantity of excision blower fan is determined by following principle: the gross output of institute's wind cutting machine reaches To P-k_thP_maxSo that after excision blower fan, wind energy turbine set injected system power is less than secure threshold k_thP_max。

The wind farm low voltage of the present invention cuts machine emergency control method, estimates the voltage stabilization of wind farm grid-connected some injecting power in real time The limit, and compare with current power, it is judged that the Voltage Stability Level of system, take during close to Voltage Instability to cut machine measure, Ensure electric network security, it is possible to ensure reasonability and the effectiveness of emergent control.

Embodiment of above is merely to illustrate the present invention, and not limitation of the present invention, about the ordinary skill of technical field Personnel, without departing from the spirit and scope of the present invention, it is also possible to make a variety of changes and modification, the most all etc. Same technical scheme falls within scope of the invention, and the scope of patent protection of the present invention should be defined by the claims.

Claims (1)

1. a wind farm low voltage cuts machine emergency control method, it is characterised in that include step:

A: ask for the thevenin equivalent circuit from the power system depending on entering of the wind farm grid-connected point, first according to wind farm grid-connected point Short circuit current I_SCEstimation equivalent reactance X_E,

B: monitor wind farm grid-connected point voltage U and the active-power P of wind energy turbine set injection power system, estimation equivalent source electricity Pressure U_E,

C: according to equivalent source voltage U_EWith equivalent reactance X_E, calculate the voltage stabilization pole of wind farm grid-connected some injected system Limit power P_max,

$P_{max}=\frac{{U_E}^2}{2X_E}=\frac{U^2}{2X_E}+\frac{P^2{X}_E}{2U^2};$

D: calculate current power P and power limit P_maxRatioAnd and threshold value k that is previously set_thCompare Relatively, 0 < k_th<1, work as k>k_thTime, excise Wind turbines, and use the gross output of excision blower fan to reach P-k_thP_max Determine the quantity of excision blower fan.