CN101895249A - Maximum wind energy tracking control method for variable-speed constant-frequency wind power generation - Google Patents

Abstract

The invention relates to a maximum wind energy tracking control method for variable-speed constant-frequency wind power generation, which belongs to the field of wind power generator set control. The method does not need to previously know the optimal performance curve of a wind power generator set, uses the improved perturbation and observation process and the power signal feedback process based on different power-rotating speed curves to carry out on-line searching, and records the information of the ratio of power to cubic rotating speed at the maximum power point. When switching to the power signal feedback process from the perturbation and observation process, the power-rotating speed curve on which the power signal feedback process is based can be obtained according to the recorded information; and after finishing recording the information, an optimal power-rotating speed curve can be obtained, and at this time, only the power signal feedback process is adopted. The method can obtain the optimal power-rotating speed curve of the wind power generator set on line according to the actual operating environment of the wind power generator set, and effectively realizes the maximum wind energy tracking. The invention is suitable for variable-speed constant-frequency wind power generation systems.

Description

A kind of maximum wind energy tracking control method of variable-speed constant-frequency wind power generation

Technical field

The present invention relates to a kind of maximum wind energy tracking control method of variable-speed constant-frequency wind power generation, belong to wind turbine generator control field.

Background technology

Wind energy is a kind of regenerative resource of cleaning, increasingly mature along with the exhaustion day by day of the aggravation of Global Greenhouse Effect, fossil energy and wind generating technology, and each state of the whole world has all accelerated the paces of development and use wind energies.Wind generating technology develops into variable speed constant frequency from constant-speed and constant-frequency, and the latter is by the rotating speed control to the wind-powered electricity generation unit with respect to the former one of advantage, can realize that the maximal wind-energy of wind generator system is followed the tracks of, and improves wind energy utilization.

Kazmi Syed Muhammad Raza etc. were " Proceeding of the 2008International Conference Electrical Machines " (the 18th international motor proceeding) (2008, the 1-6 page or leaf) " A Novel Algorithm forFast and Efficient Maximum Power Point Tracking of Wind EnergyConversion Systems " (a kind of novel maximum power tracking method of wind generator system fast and effectively) delivered on studied a kind of follow-on climbing method method, its utilization climbing method is realized the maximal wind-energy tracking and is write down a power-rotating speed cube ratio, this power-rotating speed cube ratio is a variable of the size and Orientation of decision climbing method step-length, do not write down a plurality of power-rotating speeds cube ratio or it is revised, it is not applied to the power signal FEEDBACK CONTROL, do not utilize the advantage of power signal feedback transmitter.CH.Patsios etc. were " 39th IEEE annual powerelectronics specialists conference " (the 39th International Power electronic technology specialists meeting) (2008, the 1749-1754 page or leaf) studied a kind of maximum wind energy tracking control method that the dtc signal feedback transmitter is combined with the disturbance observation in " A Hybrid Maximum PowerPoint Tracking System for Grid-Connected Variable SpeedWind-Generators " (a kind of maximal power tracing system of grid type speed-changing wind power generator of mixing) literary composition of delivering, it is earlier by original best torque-speed curves control wind-powered electricity generation unit, when given torque and wind-powered electricity generation unit actual torque difference are sought maximum power point based on the actual motion environment with the disturbance observation again after certain limit, though this method can realize following the tracks of based on the maximal wind-energy of actual motion environment, but this method needs known best torque-speed curves, the maximum power point that searches is not carried out online record and the primary characteristic curve is revised.

Zhang Xing etc. disclosed " control method for tracking maximum power point of wind electric power generation " (China, open day: on May 9th, 2007, publication number: CN1960159A) studied a kind of setting two closed loop control methods of rotating speed and power independently each other in the patent, this method is at first carried out the power signal FEEDBACK CONTROL according to the original maximum power curve of wind turbine to blower fan; Wind speed changes hour employing climbing method power optimizing control, obtains maximum power and corresponding generator speed, and the new data point of adding obtains revised maximum power curve on original maximum power curve basis; When changing greatly, wind speed implements the power signal FEEDBACK CONTROL according to revised up-to-date power curve.But this method still needs the original best power-speed curves of wind turbine, does not utilize climbing method to need not to know advantages such as wind turbine power characterisitic parameter and wind speed parameter fully.

Summary of the invention

The invention provides a kind of best power-speed curves that need not to know in advance the wind-powered electricity generation unit, in the actual moving process of wind-powered electricity generation unit by the online maximum wind energy tracking control method that obtains based on the variable-speed constant-frequency wind power generation of the best power-speed curves of actual motion environment of utilization disturbance observation and power signal feedback transmitter.

The present invention is adopted following technical scheme by its technical problem of solution:

A kind of maximum wind energy tracking control method of variable-speed constant-frequency wind power generation, the concrete steps of this method are as follows:

A) be k from coming into effect maximal wind-energy tracking Control record wind-powered electricity generation unit power output P to the process that searches first maximum power point with a rotational speed omega cube ratio, disturbance makes wind-powered electricity generation unit power output increase and k value when increasing, renewal k value;

B) when wind speed changes, from disturbance observation, i.e. Perturb﹠amp; Observe--P﹠amp; O switches to the power signal feedback transmitter, i.e. Power Signal Feedback---PSF, after the operation of PSF control wind-powered electricity generation set steady, if power-rotating speed cube than record sheet for empty or record finish, then switch to P﹠amp; O searches for maximum power point; If record is finished, then think online acquisition best power-speed curves no longer to switch to P﹠amp; O;

When c) switching to PSF, before power-rotating speed was cube than record sheet opening entry, the coefficient k that utilization a) is write down in the step was according to P=k* ω ³Implement PSF; After power-rotating speed is cube than record sheet opening entry, according to P=k _e* ω ³Implement PSF, k _eFor power-rotating speed cube than k in the record sheet _Opt1, k _Opt2, k _Opt3K _OptnMedian average filter value.

Beneficial effect of the present invention is as follows: effective fusion P﹠amp; O need not wind-powered electricity generation power of the assembling unit characterisitic parameter and PSF controls the advantage simple, reliable, that rapidity is good.In the actual moving process of wind-powered electricity generation unit, adopt P﹠amp; Online best power-the speed curves that obtains based on the actual motion environment of O and PSF finally uses PSF to realize the maximal wind-energy tracking Control fully, the actual power coefficient that effectively improves.

Description of drawings

Fig. 1 is P _Out-ω characteristic curve and different operating point place slope schematic diagram.

Fig. 2 is the control procedure schematic diagram of maximum wind energy tracking control method.

Fig. 3 is control stage 1 control flow chart.

Fig. 4 is control stages 2 control flow chart.

Fig. 5 is the variable-speed constant-frequency wind power generation system block diagram based on electric excitation biconvex pole wind power generator.

Embodiment:

Below in conjunction with accompanying drawing technical scheme of the present invention is described in further detail:

The improvement of disturbance observation: the method for 1, judging the operation of wind-powered electricity generation set steady

For guaranteeing P﹠amp; O works reliably, and it must just can implement new disturbance after the waiting system stable operation.Formula (1) has been described the relation (disregarding friction horsepower) of wind turbine output mechanical power and system's power output

$P_m=\frac{1}{\mathrm{\η}}{P}_{\mathrm{out}}+\mathrm{J\ω}\frac{\mathrm{d\ω}}{\mathrm{dt}}---\left(1\right)$

P in the formula _mBe the wind turbine power output, η is the efficient from generator to output power measurement, P _OutBe system's power output, J is the wind-powered electricity generation turbine generator inertia, and ω is a rotating speed,

Be the mechanical energy storage rate of change.When

Absolute value during less than a certain smaller value, can think the operation of wind-powered electricity generation set steady.

Can be expressed as again

Its discretization is got

The sampling time interval t (k) of J and rotating speed-t (k-1) is a constant.Therefore, when:

[ω(k)+ω(k-1)][ω(k)-ω(k-1)]≤σ (2)

When satisfying, think that the wind-powered electricity generation set steady moves, but the measuring system power output, thus implement new disturbance, the smaller value of σ for judging that stable operation is set.

The selection of 2, disturbance step-length

Q among Fig. 1 ₁, Q ₂, Q ₃, Q ₄, Q ₅The absolute value of some place slope diminishes gradually; Wind speed is big more, the P that it is corresponding _Out-ω slope of a curve absolute value excursion is big more.Therefore, can adopt different disturbance step-lengths according to the order of magnitude of place, wind-powered electricity generation unit working point slope.When absolute value is big (as Q ₁, Q ₂), adopt big step-length disturbance, improve the rapidity of disturbance observation control; Absolute value is hour (as Q ₄, Q ₅), adopt the long disturbance of small step, improve the accuracy of search maximum power point.According to above analysis, the present invention selects to improve to the step-length of disturbance observation, is provided with n disturbance step-length, and the corresponding variable power thresholding of each disturbance step-length makes n=5 that this step-length is selected to describe temporarily.

Disturbance step-length step ₁＞step ₂＞step ₃＞step ₄＞step ₅＞0, corresponding variable power threshold delta P _B1＞Δ P _B2＞Δ P _B3＞Δ P _B4＞Δ P _B5＞0, and satisfy

Suppose Q in these five slope value difference corresponding diagram 1 ₁, Q ₂, Q ₃, Q ₄, Q ₅The absolute value of place's slope.The a certain moment, used step sizes was step _i, power output is changed to Δ P _i, then the absolute value of wind-powered electricity generation unit present operating point place slope is about

Select step sizes according to following rule:

1) when

The time, promptly present operating point is positioned at Q ₁The right side more away from maximum power point, is made as step to step-length ₁

2) when

In the time of between above-mentioned 5 certain 2, as

Think that present operating point is positioned at Q ₂With Q ₃Between the point, step-length is made as step ₃

3) when

The time, promptly the slope at present operating point place is very little, can think to have run to maximum power point, then stops disturbance, thereby suppresses near the oscillatory occurences the maximum power point.

By the suitable number that step-length is set is n, and the size and the pairing power threshold of each step-length of step-length can improve rapidity, accuracy that the disturbance observation is searched for maximum power point, suppresses near the vibration of maximum power point simultaneously.

The improvement of power signal feedback transmitter:

Conventional PSF obtains system's output reference power according to known best power-speed curves by tach signal, and the wind-powered electricity generation unit is carried out power control.This control method is simple, reliable, rapidity is good, is subjected to the wind speed variable effect little, is applicable to big inertia wind-powered electricity generation unit.If these advantage effective fusion are arrived P﹠amp; In the process of O search maximum power point, will improve its maximal wind-energy tracking Control effect.Therefore, the present invention improves the PSF of routine:

P _out＝k _eω ³ (3)

In the formula: k _eBe power-rotating speed cube ratio.Work as k _eNot not simultaneously, PSF is based on different power-speed curves, and best power-speed curves is wherein special one.

Maximum wind energy tracking control method explanation of the present invention:

PSF in the maximum wind energy tracking control method of the present invention and the difference of conventional PSF are: need not to know in advance PSF based on power-speed curves, need the online proportionality coefficient k that obtains in the formula (3) _eKnow k by formula (3) _eBe power-rotating speed cube ratio, after the wind-powered electricity generation set steady operation, can obtain the power output and the rotary speed information of wind-powered electricity generation unit, and then onlinely try to achieve and write down the pairing power-rotating speed of stable operating point cube ratio.Therefore, cube to liken to power-rotating speed be contact P﹠amp in the present invention; The tie of O and PSF both can onlinely have been tried to achieve and implemented the required proportionality coefficient k of PSF _e, can improve P﹠amp by PSF again; The maximal wind-energy tracking Control effect of O, two kinds of methods of effective fusion.

Maximum wind energy tracking control method is divided into three control stages: 1, from coming into effect the maximal wind-energy tracking Control to utilization P﹠amp; O and PSF search maximum power point first, and the wind energy capture rate in this stage group of motors working point with the wind increases gradually near maximum power point gradually.2, this stage searches for and writes down power power-rotating speed cube ratio of maximum power point correspondence fast, and the wind-powered electricity generation unit is the operation of maximum power point near zone under each wind speed, has higher wind energy capture rate.3, obtain best power-rotating speed according to power-rotating speed cube ratio of control stage 2 record and cube compare k _Opt, promptly obtained best power-speed curves, only use PSF afterwards, do not re-use P﹠amp; O.

In conjunction with Fig. 2 each is controlled being described as follows of stage:

The control stage 1:

The wind-powered electricity generation unit is not implemented the preceding stable operation A point in Fig. 2 of maximal wind-energy tracking Control, at first uses P﹠amp; O searches for maximum power point, and the power-rotating speed cube ratio the during operation of record wind-powered electricity generation set steady is k, and as the A among Fig. 2, B point, the k value of their correspondences is respectively k ₁, k ₂If wind speed changes (judging that the method that wind speed changes sees below), then switch to PSF, according to P _Out=k ω ³Implement the power signal FEEDBACK CONTROL, as wind speed among Fig. 2 by v ₃Become v ₅The time, according to P _Out=k ₂ω ³Implement the power signal FEEDBACK CONTROL.Behind the PSF control wind-powered electricity generation set steady, then switch to P﹠amp; O searches for maximum power point, as among Fig. 2 according to P _Out=k ₂ω ³Implement to be stable at the C point after the power signal FEEDBACK CONTROL, switch to P﹠amp; O.

As shown in Figure 2, because k ₄Compare k ₂More near power-rotating speed cube ratio of maximum power point correspondence, when wind speed changes, according to P _Out=k ₄ω ³Will be than according to P _Out=k ₂ω ³Working point stable after the enforcement power signal FEEDBACK CONTROL is more near maximum power point.Therefore, when disturbance increases wind-powered electricity generation unit power output and k value when increasing, renewal k value, as k value among Fig. 2 from k ₁Be updated to k ₄Process.

Fig. 3 is this stage control flow chart, when searching first maximum power point, then finishes this stage control, and changes the control stage 2 over to.

The control stage 2:

Can search first maximum power point by the control stage 1, calculate power-rotating speed cube ratio of this point, and the current wind speed v that provides according to anemobiagraph, power-rotating speed cube ratio is deposited under the wind speed that (hereinafter to be referred as record sheet) is the most close with wind speed v in the table 1, ask for the median average filter value (appendix is seen in its definition) of power-rotating speed cube ratio under this wind speed afterwards, as shown in table 1.v ₁Be the incision wind speed; v _nFor implementing the maximum wind velocity of maximal wind-energy tracking Control.

Table 1 power-rotating speed cube compares record sheet

Median average filter value defined: one group of data x ₁, x ₂X _n, its median average filter value is x, if n=0, if x=0 then is n=1, then x=x ₁If, n=2, then x=min (x ₁, x ₂), if n＞=3, x is for removing the mean value of remaining data after maximum and the minimum value in these group data.

In theory, best power-rotating speed cube compares k _OptPower-the rotating speed corresponding with maximum power point cube ratio equates.But because P﹠amp; There is certain error in O search maximum power point, and the down different maximum power points of constantly obtaining of same wind speed can be different, and corresponding power-rotating speed cube ratio is also just different; Power-the rotating speed of the maximum power point correspondence of obtaining under the different wind speed cube ratio also can be different, as shown in Figure 2.If the maximum power point that searches of control stage 1 is the E point, its corresponding power-rotating speed cube ratio directly cube is compared k as best power-rotating speed _Opt, obtain best power-speed curves L ₁, enter the control stage 3 afterwards, implement the power signal FEEDBACK CONTROL, the wind energy capture rate of wind-powered electricity generation unit is not very high, as shown in Figure 2.Therefore, need take suitable method to improve and ask for k _OptAccuracy.At first, power-rotating speed cube ratio that same wind speed is obtained is down asked median average filter value, determine under this wind speed power-rotating speed cube ratio more accurately, as wind speed v in the table 1 ₁Corresponding power-rotating speed cube ratio is k _Opt1Secondly, all wind speed that can implement the maximal wind-energy tracking Control are all asked its corresponding power-rotating speed cube ratio, as in the table 1 from wind speed v ₁To wind speed v _nAll ask power-rotating speed cube ratio.

If all have at least 3 power-rotating speeds cube ratio to obtain under each wind speed, then can obtain k more accurately _Opt1, k _Opt2, k _Opt3..., k _Optn, ask median average filter value as k to them _OptHave higher accuracy, can think that record sheet record finishes this moment.

Fig. 4 described should the stage control procedure, after the record sheet record is finished, then finish the control in this stage, and change the control stage 3 over to.Control modes 1: when wind speed is constant, then stop disturbance, the wind-powered electricity generation set steady runs on maximum power point.Control modes 2: when wind speed changes, then switch to PSF, the proportionality coefficient in its required formula (3) is k _Opt1, k _Opt2, k _Opt3K _OptnMedian average filter value.Behind the PSF control wind-powered electricity generation set steady, then switch to P﹠amp; O searches for the maximum power point under the new wind speed.

What this stage used all is power-rotating speed cube ratios of maximum power point correspondence, thus near the operation area operation maximum power point under each wind speed of wind-powered electricity generation unit, as L among Fig. 2 ₁With L ₂Between shown in the zone, have higher wind energy capture rate.Along with the increase of the power-rotating speed that is write down cube ratio, k _Opt1, k _Opt2, k _Opt3..., k _OptnMedian average filter value more and more near k _Opt, the operation area of wind-powered electricity generation unit dwindles gradually, gradually near best power-speed curves.

The control stage 3:

After the record sheet record is finished, ask k _Opt1, k _Opt2, k _Opt3K _OptnMedian average filter value as k _Opt, promptly obtained best power-speed curves P _{Out_opt}=k _Optω _Opt ³, P _{Out_opt}Be system's Maximum Power Output, as shown in Figure 3.Implement the power signal FEEDBACK CONTROL according to best power-speed curves afterwards, do not re-use P﹠amp; O.

As shown in Figure 5, wind energy is converted to electric energy by wind turbine and electric excitation biconvex pole wind power generator, again by three-phase not control rectifier be transformed to direct current, for the grid type wind generator system, direct current by combining inverter feeding electric energy into electrical network; For non-grid type wind generator system, direct current can use or be transformed to alternating current through inverter for DC load and use for AC load through conversion.

The disturbance variable of disturbance observation is the exciting current of DSEG, and observed quantity changes for system's power output.

When wind speed changes, from P﹠amp; O switches to PSF.After the operation of PSF control wind-powered electricity generation set steady, if record sheet for empty or record finish, then switch to P﹠amp; O searches for maximum power point; If record is finished, then think online acquisition best power-speed curves no longer to switch to P﹠amp; O.

For described electric excitation biconvex pole wind power generator system, implementing P﹠amp; In the process of O, can judge wind speed by following any one method and change:

1) twice continuous disturbance all causes power output to reduce, by former P﹠amp; O manages as can be known, and when last time, disturbance made that power output reduces, this should apply rightabout disturbance, according to P _OutThe unimodal characteristic of-ω curve, this power should increase;

2) exciting current increases, and the generator resistive torque increases, and rotating speed reduces, if rotating speed rises, then wind speed changes, and in like manner, exciting current reduces, if rotating speed descends, then wind speed changes;

3) exciting current is constant, and the operation of wind-powered electricity generation set steady is if rotation speed change can judge that wind speed changes;

4) at a rotating speed in the sampling time, the rotation speed change amount has surpassed because the rotation speed change thresholding that the exciting current disturbance can cause;

5) in the fixed long period in sight, the wind-powered electricity generation unit does not reach steady operational status.

Claims (1)

1. the maximum wind energy tracking control method of a variable-speed constant-frequency wind power generation is characterized in that:

A) be k from coming into effect maximal wind-energy tracking Control record wind-powered electricity generation unit power output P to the process that searches first maximum power point with a rotational speed omega cube ratio, disturbance makes wind-powered electricity generation unit power output increase and k value when increasing, renewal k value;

B) when wind speed changes, switch to the power signal feedback transmitter from the disturbance observation, after the operation of PSF control wind-powered electricity generation set steady, if power-rotating speed cube than record sheet for empty or record finish, then switch to P﹠amp; O searches for maximum power point; If record is finished, then think online acquisition best power-speed curves no longer to switch to P﹠amp; O;

When c) switching to PSF, before power-rotating speed was cube than record sheet opening entry, the coefficient k that utilization a) is write down in the step was according to P=k* ω ³Implement PSF; After power-rotating speed is cube than record sheet opening entry, according to P=k _e* ω ³Implement PSF, k _eFor power-rotating speed cube than k in the record sheet _Opt1, k _Opt2, k _Opt3K _OptnMedian average filter value.

Images