WO2014183421A1

WO2014183421A1 - Control method for outputting active power through grid-connected electricity generation of wind power plant

Info

Publication number: WO2014183421A1
Application number: PCT/CN2013/088460
Authority: WO
Inventors: 吴晓明; 王欣星; 王多; 汪宁渤; 薛云飞
Original assignee: 许继集团有限公司; 甘肃省电力公司; 北京许继电气有限公司; 国家电网公司
Priority date: 2013-05-14
Filing date: 2013-12-03
Publication date: 2014-11-20

Abstract

A control method for outputting active power through grid-connected electricity generation of a wind power plant, belonging to the technical field of grid-connected control of wind power plants. The present invention comprises: firstly, establishing a relationship between a power P_W which may be currently generated by a wind power plant and a fluctuating power P_RES which needs to be abandoned to suppress fluctuation, so as to obtain the fluctuating value required to suppress an active power; in accordance with the requirement of a power grid for the fluctuating amplitude of different wind power plants in different time periods, determining a time constant T of a first-order low-pass filter, determining a sampling interval t, and further discretizing same in a time domain to obtain a stabilization parameter α; concluding the single-machine control of the wind power plant as a target-adjustable integral control policy; and obtaining an adjustable active power target value adapted to the power grid. The load can be rationally distributed in accordance with the target value through the coordinated control of the wind power plant. The self-protection of a draught fan is also changed from passive adjustment of an oar or a splitting type to an active preventing type, thereby not only effectively improving the operation efficiency of the draught fan, but also reducing the impact on the power grid and protecting the operation of the draught fan.

Description

TECHNICAL FIELD The present invention relates to a wind farm grid-connected power generation output active power control method, and belongs to the field of wind farm grid-connected control technology. BACKGROUND OF THE INVENTION The influence of wind farm grid-connected capacity on system stability depends on the wind farm short-circuit capacity ratio, that is, the ratio of the wind farm output capacity to the short-circuit capacity of the wind farm and the current power system operating mode. When the short circuit ratio is large, the random fluctuation of the output power of the wind farm will have a significant impact on the grid frequency. At present, the grid-connected power generation of domestic wind farms is in an "empirical human intervention" state, lacking reasonable control for grid-connected power generation in different state wind farms. The control principle is that the wind power grid-connected power is equivalent to the passive reserve capacity of the grid. Scheduling method. There is no reasonable scheduling for the effective mechanism of time and space complementation of wind farms in the region to maximize the utilization of wind power. It lacks the fairness of wind farms and reduces the benefits of different types of power generation enterprises. SUMMARY OF THE INVENTION The object of the present invention is to provide a wind power grid-connected power generation output active power control method, which is used for rationally dispatching wind farm grid-connected power generation output stable active power, and reducing wind farm grid-connected power generation due to wind power fluctuation to the power grid. interference.

In order to solve the above technical problem, the present invention provides a control method for outputting active power of a wind farm connected to the grid, and the steps of the control method are as follows:

1) According to the wind turbine's own equipment measurement superposition or wind power prediction system, the active power p _{w that} can be generated by the wind farm is obtained _;

2) Determine the active power P injected into the grid by the wind farm according to the current grid rotation reserve capacity, stability requirements and load requirements. _Ut ,

Where P _res is the abandoned wind power active power; 3) Determine the time constant τ of the first-order low-pass filter according to the requirements of the grid for the fluctuation amplitude of different wind farms at different time periods, so that it satisfies:

1 + zs

Where _Κι = ^^ is the first-order high-pass filter, = is the first-order low-pass filter, _τ is the time constant, τ = 2nf _c , and f _c is the cutoff frequency of the equivalent filter;

4) After the time domain analysis and discrete finishing of the active power 1\^ injected into the grid by the wind farm:

p. ( _u ? = < + a- «) P. ( _U "

Among them, Ρ. For the active power injected into the grid at the Nth moment of the wind farm, P _W ^N is the predicted power of the Λ/time wind field, which is the active power injected into the grid at the previous moment, a is the smoothing parameter, “=—^,

t + r t is the sampling interval;

5) According to the active power target value of the injection grid obtained in step 4), the wind farm coordinates and controls the reasonable distribution of the load.

The active power injected into the grid by the wind farm obtained in the step 4) can be adjusted as follows, and the benchmark power P _REF is set, that is, the grid dispatching power generation plan value is given to the wind farm at a certain interval, which is compared with the power grid injection. Active power P and benchmark power P _REF , which gives the allowable active fluctuation value,

Set the fluctuation threshold. If the absolute value of the deviation of the active fluctuation value is allowed to be greater than f, ie δ- ^ > ε, return to the adjustment period again until the result converges. If the absolute value of the deviation of the active fluctuation value is allowed to be less than or equal to ^ - | ≤ ^, then end this adjustment, where f is small enough. The discarded wind power active power corresponding to the adjustment can be reasonably quantified.

The active power that can be generated by the wind farm is applied to the wind farm coordination control device to apply the first-order low-pass filtering principle. The active power injected into the grid, and the wind power active power that is reasonably discarded, is the integration of the wind farm coordination control device in time. The expression in the S domain is as follows:

The expression transformed into the time domain is

Where: P _dis is the variable of the wind power active power abandoned in the wind field in the S domain; the variable of the wind power active power discarded in the wind farm wind farm in the time domain.

The discarded wind power active power P _res can be used for heating and replaced with electric power of the same power. The discarded wind power active power P _res can be used for power station battery charging, for power storage and self-use of the power station.

The beneficial effects of the present invention are as follows: The present invention obtains the need to suppress the active power fluctuation value by establishing the relationship between the power that the wind farm may currently emit and the fluctuation power that needs to be abandoned to suppress the fluctuation; and the fluctuation amplitude according to different grids of different wind farms according to the grid The value requirement determines the time constant of the first-order low-pass filter, determines the sampling interval, and further obtains the smoothing parameter in the time domain, thereby providing an overall control strategy for classifying the wind farm single-machine control into a target adjustable; Due to the adjustable active power target value adapted to the power grid, the coordinated control of the wind farm can distribute the load according to the target value, and the self-protection of the fan is changed from passive paddle or de-column to active prevention, which not only increases effectively. The efficiency of the fan operation also plays a positive role in reducing the impact on the grid and on the operation of the fan.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic block diagram of a control method for outputting active power of grid-connected power generation of a wind farm according to the present invention; and FIG. 2 is a logic block diagram of a method for controlling output power of grid-connected power generation of the present invention. detailed description

The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. The block diagram of the control system of the present invention is shown in Figure 1. The wind farm remote-moving device receives the load finger from the dispatch. Therefore, the load command is dispatched according to the wind power reporting power plan by the dispatching and combined with the wind power power that the power grid can absorb in the current time period. The remote control device sends the command to the wind power coordination control system. The wind farm coordinated control system issues the adjustment command according to the modulatable wind power to the wind turbines at different positions (the fan position refers to the range defined by the wind energy line). Wind power is generated in the transient buffer, and the transient buffer is a wind power storage device composed of capacitors.

A coordinated control method for active power of a wind farm according to the present invention will be described with reference to FIG. 1 and FIG. 2, and the steps are as follows:

1. wind farm or wind power equipment superimposed predicted wind farm can be made active power P _w, P _w is placed can be made active in the transient buffer wind turbine according to measurement apparatus itself;

2. The transient buffer consists of an AC-DC-AC power inverter, in which the capacitance of the DC section can act as a buffer for sudden power changes. When the DC capacitor voltage is detected to rise, the excess is modulated as follows. ;

3. Grid dispatching According to the current grid reserve capacity and stability requirements, the load determines the active power Pout injected into the grid by the wind farm, and the active power injected into the grid by the (1) type wind farm:

Among them, P _res is the abandoned wind power active power: = Ι ^ Ί ( 2)

Where _{= 7} ^^ is the first-order high-pass filter, =; ^ is the first-order low-pass filter. τ is time

1 + rs constant, ^ = 2πΐ , is the equivalent filter cutoff frequency.

The design of τ must be able to effectively suppress wind power fluctuations. Therefore, the larger the value of τ is, the more significant the effect is, and the lower the frequency component that is allowed to conduct, the smaller the rate of change of active power injected into the grid, resulting in the entire power output. Smoother.

4. According to the principle of first-order low-pass filtering, the time domain analysis of equation (3) is obtained: P =τΡ' +P

(4) where: p. ' _ut p. _Ut differential, set the pseudo control sampling interval, then discretize

Finished: i + 士^; (6)

Let the formula (6) be expressed as:

(N-i)

(7) The active power P injected into the grid at the Nth moment of the wind farm. _{Ut is} related to the current wind field predicted power P _w , the injection power at the front Λ /-1 time, and the smoothing parameter α.

5 pairs of active power injected into the grid from step 4! ^Adjustment, the specific adjustment process is as follows: Set a benchmark power P _ref (set value), that is, the grid dispatching will give the wind farm a power generation plan value every time interval, and compare the active power P injected into the grid. _Ut and benchmark power P _ref (given), the allowable active fluctuation value is obtained:

P„ _f -P„,

^ = (1-Κ ₂ )χ100% _: :100% (8) p _rei

The active power injected into the grid still contains low-frequency components. Under the standard of wind power access to the power system, that is, the allowable active fluctuation value is satisfied. These low-frequency fluctuation components can be stabilized by the corresponding peak-shaping machine, that is, the current grid rotation reserve. Capacity, set the fluctuation threshold, if the absolute value of the deviation of the allowable active fluctuation value is greater than f, ie

0\> ε, return to the adjustment cycle again until the result converges; if the absolute value of the deviation of the allowable active fluctuation value is less than or equal to ^ ie - | ≤ s, the current adjustment is ended, where f is sufficiently small. simple Said that the process is a loop to ^P. So adjust until it approaches ¹ ^.

6. The abandoned wind power corresponding to the adjustment can be reasonably quantified to obtain the active power that can be generated by the wind farm. The low-pass filter principle is adopted by the wind farm coordination control device to control the active power injected into the Internet, and the wind power active power is reasonably discarded. Then for the wind farm to coordinate the control unit's integration over time, its expression in 51: or is as follows: = = ^ = (9) The expression transformed into the time domain is

P _di∑ ( ) = X _.3⁄4 (f) = j^ e " ^i/T P _w (t - £}d ( 10) Discarded wind power active power can be used for heating, heating due to thermal inertia For power supply stability requirements are not high, can replace the same power of electric heating power, discarded wind power active power can also be used for power station battery charging, for power station energy storage and self-use.

The design of τ must be able to effectively suppress wind power fluctuations. Therefore, the larger the value of τ is, the more significant the effect is, and the lower the frequency component that is allowed to conduct, the smaller the rate of power change injected into the grid, so that the overall power output is more For smoothing.

Claims

Claim

A control method for outputting active power by grid-connected power generation of a wind farm, characterized in that: the steps of the control method are as follows:

2) According to the current grid rotation reserve capacity, stability requirements and load requirements, determine the active power P _ut P _res injected into the grid by the wind farm as the abandoned wind power active power,

3) Determine the time constant τ of the first-order low-pass filter according to the requirements of the grid for the fluctuation amplitude of different wind farms at different time periods, so that it satisfies:

1 + zs

Where _Kl = - is the first-order high-pass filter, = is the first-order low-pass filter, and τ is the time

1 + rs constant, τ = 2nf _c f _c is the equivalent filter cutoff frequency;

p _u ? = < + a- «)P _U "

t + r t is the sampling interval;

2 . The control method for outputting active power of a wind farm connected to a power generation according to claim 1 , wherein: the active power injected into the power grid of the wind farm obtained in the step 4) can be adjusted as follows to set the benchmark power. P _ref means that the power grid dispatching power generation plan value will be given to the wind farm every time interval. Comparing the active power P and the benchmark power P _ref injected into the grid, the allowable active fluctuation value is obtained.

Set the fluctuation threshold. If the absolute value of the deviation of the active fluctuation value is allowed to be greater than f, that is, δ - ^ ε, return to the adjustment period again until the result converges. If the absolute value of the deviation of the active fluctuation value is allowed to be less than or equal to ^ ie|^ - | ≤ s, then this adjustment is ended, where f is small enough.

The method for controlling output power of a wind farm connected to a power generation according to claim 2, wherein: the discarded active power of the wind power corresponding to the adjustment is reasonably quantifiable,

The active power that can be generated by the wind farm is applied to the wind farm coordination control device to apply the first-order low-pass filtering principle to control the active power injected into the grid, and the wind power active power that is reasonably discarded is the time integral of the wind farm coordination control device. , its expression in the S field is as follows:

^ s ' s i^ s - 1-5- The expression transformed into the time domain is

P _dt t) = XP _w {t) = ζ β ^{→ /τ} P^ (t - u),d where: P _dls is the variable of wind power active power in the S domain discarded by the wind farm; wind power for wind farm The variable of the wind power active power abandoned in the field.

The control method for outputting active power of a wind farm connected to a power grid according to claim 3, wherein: the discarded wind power active power Pres can be used for heating and replaced with electric power of the same power.

5 . The control method for outputting active power of a wind farm connected to a wind farm according to claim 3 , wherein: the discarded wind power active power I s can be used for charging the power station battery, and is used for power storage and self-use of the power station. .