CN101813059A - Power control method of low-rated wind speed wind driven generating system - Google Patents

Abstract

The invention discloses a power control method of a low-rated wind speed wind driven generating system, having the following four characteristics: (1) a fan is in a stop state and the output power is zero when the wind speed is lower than a cut-in wind speed; (2) the fan is in a maximum wind energy tracking state and the output power and the wind speed are in a cubic function relation when the wind speed is higher than the cut-in wind speed and lower than a rated wind speed; (3) the fan is in a limit-rated power operation state, and the generation power fluctuates below the rated power when the wind speed is higher than the rated wind speed and lower than the cut-in wind speed; and (4) the fan is in the stop state and the output power is zero when the wind speed is larger than the cut-in wind speed. The invention can realize the safe, reliable and high-efficiency operation of the low-rated wind speed wind driven generating system and avoids overspeed, overload and galloping accidents.

Description

The Poewr control method of low-rated wind speed wind driven generating system

Technical field

The present invention relates to a kind of control system of wind-power generating system, especially relate to a kind of low-rated wind speed wind driven generating control system.

Background technique

Wind energy is a kind of transition form of solar energy, be inexhaustible, nexhaustible, be converted in the process of electric energy at it, do not produce any harmful gas and waste material, free from environmental pollution, having gathers materials on the spot does not need characteristics such as transportation, therefore be subjected to the extensive attention of countries in the world government, nearly all developed country all lists the development and use of wind energy in most important task of this country's 21 century.Except that financially supporting energetically, the development and use that corresponding laws and rules is helped wind energy have also been formulated.China has abundant wind energy resources, and the area that can develop accounts for 76% of national total area, reaches from aspect the application of net type wind power generating set significant progress being arranged at the development and use of wind energy turbine set, the commercial development of grid type wind power generating set.Particularly walk the prostatitis in the world outside solving conventional electrical network aspect the areas without electricity agriculture and animal husbandry fisherman electricity consumption, throughput, recoverable amount and Annual output all rank first in the world.

The current abundant area of wind energy resources that still sight is mainly concentrated on high wind speed both at home and abroad for the exploitation of wind energy.By setting up large-scale wind power plant, development MW level wind-powered electricity generation unit, the generating of being incorporated into the power networks, realize that the wind-powered electricity generation of high efficiency, low cost can be changed.But above-mentioned area only accounts for 8% of China's gross area, and mainly is distributed in the more underdeveloped hinterland of economy.And huge wind energy resources is being contained in other low wind speed area of China equally, but and be not suitable for continuing to adopt the large-scale wind-powered electricity generation development mode of setting up wind energy turbine set, and be applicable to that the ripe advanced wind power technology in high wind speed district also is difficult to the parallel low wind speed area that extends to.And the design difficulty of the control system of low-rated wind speed wind driven generating system is:

1) the wind energy specific power in low wind speed area is low, need catch the not too abundant wind energy of conversion with higher efficient.This has just proposed more strict requirement to the performance of each constituent element of wind-powered electricity generation unit, cooperation between them and the optimization control of machine system.

2) low-rated wind speed wind driven generating system focus on most of low wind speed period inner blower more can efficiency operation, therefore adopt large-scale blades to cooperate the global design thought (for high rated wind speed wind driven generating system) of small capacity electrical equipment.This make the time and under the high wind speed condition that occurs, the danger situation of " low load with strong power " appears in blower fan easily, promptly the transformation of electrical energy capacity can not mate the mechanical output input.

3) consider the cost cost of unit capacity, low-rated wind speed wind driven generating system does not generally adopt Stall Type blade or feather blade.This makes blower fan be difficult to the input of minimizing impeller wind energy rapidly under greater than the rated wind speed condition, causes blower fan hypervelocity, overpower operation easily, even the windmill accident.

4) owing to adopt the design philosophy of large-scale blades, the cabin of low-rated wind speed wind driven generating system is heavier, can only adopt electronic yawing mode, and is difficult to adopt the tail vane yawing mode.In addition, owing to do not adopt advanced feather technology, the control that also needs to go off course is by the input of the inclined to one side side of impeller to wind inhibition impeller wind energy.This has proposed higher requirement again to driftage control.

In sum, the key issue of low-rated wind speed wind driven generating Control System Design is, under precondition not by pulp distance varying mechanism or stalled blade, should guarantee that blower fan can high efficiency conversion wind energy in being lower than the rated wind speed interval, guarantee again can be safe and reliable when being higher than rated wind speed run without interruption, do not exceed the speed limit, runaway accident does not appear in nonoverload.

Summary of the invention

Technical problem to be solved by this invention provides a kind of Poewr control method of low-rated wind speed wind driven generating system, can realize the operation that low-rated wind speed wind driven generating system is safe, reliable, efficient.

For solving the problems of the technologies described above, the invention provides a kind of Poewr control method of low-rated wind speed wind driven generating system, it is characterized in that, comprise following 4 aspects:

1) at wind speed less than incision during wind speed, blower fan is in halted state, output power is zero;

2) when wind speed is higher than the incision wind speed and is lower than rated wind speed, blower fan is in maximal wind-energy and follows the trail of state, and output power becomes the cube function relation with wind speed, promptly

P(ω)＝k ₁ω ³， $k_1=0.5\mathrm{\ρA}{C}_p^{\max }{(R/{\mathrm{\λ}}_{\mathrm{opt}})}^3$

Wherein, P is an output power, and ω is a generator speed, and ρ is an air density, C _pBe power coefficient, λ is a tip speed ratio, and A is the impeller wind sweeping area, and R is an impeller radius,

Be the optimal wind energy utilization factor;

3) when wind speed is higher than rated wind speed and is lower than cut-out wind speed, blower fan is in limit and decides the power running state, and generated output remains on the following fluctuation of rated power;

4) at wind speed during greater than cut-out wind speed, blower fan is in halted state, and output power is zero.

The beneficial effect that the present invention reached: the power control of low-rated wind speed wind driven generating system of the present invention, can realize the operation that low-rated wind speed wind driven generating system is safe, reliable, efficient, do not exceed the speed limit, runaway accident does not appear in nonoverload.

Description of drawings

Design wind speed-the power curve of Fig. 1 low-rated wind speed wind driven generating system;

The theory diagram of Fig. 2 power control;

Fig. 3 λ-C _pProfile;

Fig. 4 optimum speed-power curve schematic representation;

The big slope power curve of Fig. 5 suppresses the schematic representation of power;

The schematic representation of Fig. 6 predeterminated voltage-power curve;

Fig. 7 permanent magnet generator load experimental principle figure;

VDC under Fig. 8 different rotating speeds condition-mechanical output set of curves;

Fig. 9 is mapped as VDC-power points by rotating speed-power points.

Embodiment

The design of power control

Power control unit changes the rotating speed and the power coefficient of impeller by adjusting the inverter power of combining inverter, realizes the control to the blower fan output power.

Fig. 2 has provided the theory diagram of power control, at first according to the VDC V that measures _DCAnd predeterminated voltage-power curve, calculate current VDC corresponding reference inverter power P _E.RAgain by the inverter power P of PID controller with inverter _eBe adjusted to expected value P _E.RIt should be noted that blower fan passes through predeterminated voltage-power curve and realizes power control, rather than common speed power curve.For the permanent magnet generator that band carries, rotating speed and VDC have the relation of approximately linear, and it is feasible fully to utilize VDC to substitute rotating speed.

Power control focus on default power curve, in order to realize diverse control strategy under different running statees, the reasonable setting of voltage-power curve is very crucial.The setting of this curve is divided into following 3 steps:

1) speed power curve under the maximal wind-energy tracking state

Under maximal wind-energy tracking state, power control needs to realize MPPT maximum power point tracking (MPPT) control, realizes the capturing wind energy of maximal efficiency.At this moment, need the rotating speed of impeller can follow the trail of fluctuations in wind speed, guarantee that impeller runs on best tip speed ratio λ as far as possible _OptAnd near.According to the Bates theory, the mechanical output that impeller transforms is

$P=\frac{1}{8}\mathrm{\π\ρ}{D}^2{v}^3{C}_p\left(\mathrm{\λ}\right)$

Wherein, ρ is an air density, and D is an impeller diameter, and v is a wind speed, C _pBe power coefficient, λ is a tip speed ratio.C _pWith the function relation schematic representation of λ as shown in figure 10.

As seen from Figure 3, λ-C _pCurve presents parabolic.Wherein, C _pThe λ of maximum value correspondence is best λ, is designated as λ _OptAccording to λ-C _pCurve can obtain the wheel speed-mechanical output relation curve of cluster corresponding to different wind speed, as shown in Figure 4.Further, on each bar curve corresponding to λ _OptMaximum power point be linked to be curve, can obtain optimum speed-power curve P _Opt(ω),

P _opt(ω)＝k ₁ω ³， $k_1=0.5\mathrm{\ρA}{C}_p^{\max }{(R/{\mathrm{\λ}}_{\mathrm{opt}})}^3$

Wherein, A is the impeller wind sweeping area, and R is an impeller radius, The optimal wind energy utilization factor.

2) limit is decided the speed power curve setting under the power rating

Limit is decided under the power rating, and power control needs to suppress the raising of wheel speed with wind speed, by reducing the tip speed ratio λ and the power coefficient C of impeller _p, make the output power of blower fan maintain near the fluctuation of rated power, can be because of the operation of strong wind overpower.In order to suppress the raising of wheel speed with wind speed, the generator electromagnetic torque that limit is decided under the power rating is violent in the time of should following the trail of state than maximal wind-energy with wind speed, change in rotational speed, and the slope of corresponding speed power curve should be enough big.

As shown in Figure 5, if continue to use optimum speed-power curve in being higher than the rated wind speed interval, then blower fan will bear the mechanical output input of 22.0KW under the 9m/s wind speed, far surpass 10KW rated power; If the steeper speed power curve in the application drawing shown in the solid line, then under same big wind speed, the input mechanical output of blower fan is suppressed near the power limit 13KW.

3) experiment of voltage-power curve is obtained

VDC is convenient to measure, and the sensitivity and the validity that measure all are higher than tach signal.So, should adopt VDC to replace rotating speed to determine the inverter power of blower fan in real time in the practical application.For this reason, need to obtain the function relation of generator speed and VDC, and speed power curve is mapped as voltage-power curve P (V by permanent magnet generator load experiment _DC).

By above-mentioned 3 steps, can obtain predeterminated voltage-power curve, its schematic representation is as shown in Figure 6.This power curve is divided into two sections, follows the trail of state, approximate satisfied 3 function relations of power and VDC corresponding to maximum wind speed for first section; Decide power rating corresponding to limit for second section, be the very big straightway of slope.

The enforcement of power control

In the low-rated wind speed wind driven generating system that has put into operation, the hardware of power control unit is realized being finished by the blower fan combining inverter of buying.The WG**K3 series blower fan inverter of being produced by Hefei Sunlight Power Supply Co., Ltd. provides initial inverter voltage, maximum inverter voltage setting, and 10 power settings of dividing equally electrical voltage point in this voltage range.By the setting of these 10 voltage-power points, can make the voltage-power roadability piecewise approximation predeterminated voltage-power curve of inverter.

The groundwork that power control unit is implemented is that voltage-power curve rationally is set.Follow the trail of the speed power curve that state and limit decide power rating under about maximal wind-energy and set middle description in the design part, do not repeat them here.To introduce below and how to determine the function relation of rotating speed and VDC, thereby finally determine voltage-power curve by permanent magnet generator load experiment.

Permanent magnet generator load experiment principle constitutes as shown in Figure 7.In the experimental system, frequency variator and three phase induction motor are formed prime mover part of rotating speed adjustable.Simultaneously, need carry out real-time measurements and calculations to voltage, electric current, the electromotive power output of rotating speed, torque, input mechanical output and the electric direct current component of mechanical part.Experimental procedure is as follows:

Step 1: the initial rotating speed of determining initial inverter voltage correspondence.Regulate prime mover rotating speed till the unloaded VDC of generator reaches initial inverter voltage, note initial rotating speed;

Step 2: initial rotating speed to 125% rated speed and zero power in the two-dimentional interval of 125% rated power, be incremental steps with 10% rated speed and 10% rated power.Under each rotating speed and inverter power condition, measure VDC V _DC, direct current (d.c.) I _DC, generator input torque T _mWith generator speed ω, calculating generator electromotive power output P _e, generator imports mechanical power P _m, and insert table 1;

Permanent magnet generator laboratory data under table 1 different rotating speeds and the power condition

Step 3: according to table 1 data, utilize the method for least squares linearity, linear fit goes out the linear relationship of VDC-mechanical output under the different rotating speeds ω i condition,

$P_m^{{\mathrm{\ω}}_i}\left(V_{\mathrm{DC}}\right)=a{V}_{\mathrm{DC}}+b,$ ω＝ω _i，

As shown in Figure 8.Wherein, a and b are fitting parameter;

Step 4: according to

Set of curves, the some discrete point (ω in the speed power curve that theoretical calculation is obtained _i, P _m(ω _i)) be mapped as (V _DC ⁱ, P _m(ω _i)), shown in Δ among Fig. 9;

Step 5: utilize method of least squares, to some discrete point (V _DC ⁱ, P _m(ω _i)) carry out the cubic function curve fitting, promptly

$P_m\left(V_{\mathrm{DC}}\right)=\mathrm{<figure-callout\; id="3"\; label="a\; V\; DC"\; filenames="HSA00000047826700021.png,HSA00000047826700042.png"\; state="\{\{state\}\}">a</figure-callout>}{V}_{\mathrm{DC}}^{}{}_3^{}+\mathrm{<figure-callout\; id="2"\; label="b\; V\; DC"\; filenames="HSA00000047826700011.png,HSA00000047826700021.png"\; state="\{\{state\}\}">b</figure-callout>}{V}_{\mathrm{DC}}^{}{}_2^{}+c{V}_{\mathrm{DC}}+d$

P _m(V _DC) be predeterminated voltage-power curve.

By permanent magnet generator load experiment, we can obtain under definite rotating speed and definite mechanical output condition, the machine end VDC of permanent magnet generator.Thereby find the function relation V of generator speed and VDC _DC=f (P _m, ω), and the voltage-power curve P (V of acquisition match _DC).

In addition to the implementation, all employings are equal to the technological scheme that form obtained of replacement or equivalent transformation, all drop within protection scope of the present invention.

Claims (1)

1. the Poewr control method of a low rated power wind-power generating system is characterized in that, comprises following 4 parts:

1) at wind speed less than incision during wind speed, blower fan is in halted state, output power is zero;

2) when wind speed is higher than the incision wind speed and is lower than rated wind speed, blower fan is in maximal wind-energy and follows the trail of state, and output power becomes the cube function relation with wind speed, promptly

P(ω)＝k ₁ω ³， $k_1=0.5\mathrm{\&rho;}{\mathrm{AC}}_p^{\max }{(R/{\mathrm{\&lambda;}}_{\mathrm{opt}})}^3$

Wherein, P is an output power, and ω is a wheel speed, and ρ is an air density, C _pBe power coefficient, λ is a tip speed ratio, and A is the impeller wind sweeping area, and R is an impeller radius, Be the optimal wind energy utilization factor;

3) when wind speed is higher than rated wind speed and is lower than cut-out wind speed, blower fan is in limit and decides the power running state, and generated output remains on the following fluctuation of rated power;

4) at wind speed during greater than cut-out wind speed, blower fan is in halted state, and output power is zero.

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