CN102355192B - Control method of reactive power of doubly fed wind power generator - Google Patents

Abstract

The invention relates to a control method of reactive power of a doubly fed wind power generator. The doubly fed wind power generator comprises a doubly fed motor, wherein the motor comprises a stator and a driving rotor, and the stator supplies power to a grid; the grid has rated voltage, and the driving rotor is coupled with the stator; one end of the rotor is connected to a wind turbine through a transmission gear, and a rotor winding is a three-phase wound rotor winding; and the grid supplies power to the rotor through a converter, and stator voltage and stator flux are decomposed onto a synchronously rotary dq coordinate axis to control the reactive power output by the generator stator by adjusting the current of the rotor. In the method, no complex transformation and calculation of vector rotation change and the like are needed, the control sensitivity of a current control module is lower, the circuit parameters and the measurement delay of a converter system have smaller impacton current control, and the control technology is simple, and thereby the cost of a controller is also reduced. The control method is suitable for application of a low-power wind power generator.

Description

The control method of double-fed wind power generator reactive power

Technical field

The present invention relates to a kind of wind-driven generator, particularly be connected to the control method of electrical network double-fed wind power generator reactive power.

Background technology

, environmental pollution growing in energy resource consumption be serious today day by day, is subject to the generally attention of countries in the world as the wind energy of renewable green energy resource, and wind generating technology also becomes the focus that various countries scholar in recent years competitively studies.Wind energy is the frequently random energy of a kind of variation, the variable-speed constant-frequency wind power generation technology can guarantee that the wind energy under most wind speed is caught to greatest extent and utilized, and has an incomparable superiority of traditional constant-speed and constant-frequency wind generating technology, and double-fed wind power generator can satisfy the specification requirement of variable-speed constant-frequency wind power generation well, becomes a kind of control strategy of relatively optimizing at present.It is to apply three-phase alternating current by two PWM current transformers in the rotor-side of double-fed generator to carry out excitation, by regulating effective value, phase place and the frequency of exciting current, realizes the control of the meritorious and reactive power of stator side output.

Double-fed wind power generator the basic hardware topology as shown in Figure 1, the stator of generator is directly connected to electrical network, the rotor winding links to each other with electrical network through current transformer by collector ring, by frequency, the effective value of control rotor current, phase place and phase sequence are utilized two PWM current transformers, by the SPWM control technology, can obtain sinusoidal wave rotor current, to reduce the harmonic torque in the generator, realize that stator side output is gained merit and the control of reactive power.

Because there is the coupling on the magnetic circuit in the circuit of double-fed generator, and the Mathematical Modeling under its three phase coordinate system be non-linear, the time high order system that becomes.For realize gaining merit, idle decoupling zero control, usually adopt vector control method, vector control is theoretical according to vector, adopt and press stator field direction orientation, be the rotor current resolution of vectors two mutually perpendicular current components in synchronous rotating frame, realize the decoupling zero of generator active power and reactive power is regulated.But realize decoupling zero for making motor, need to simplify motor model, also to carry out complicated conversion and the calculating such as Vector Rotation variation, and current control module control susceptibility is higher, the circuit parameter of converter system, measurement time-delay and phase-locked loop performance all have larger impact to Current Control, and these factors have caused the robustness of vector control method on the low side.Work as circuit parameter, when measurement time-delay and other system factor changed, the obvious change can occur in controller stability, strengthened the debugging difficulty of controller parameter.

Summary of the invention

The object of the invention is to overcome the deficiency of existing double-fed wind power generator Reactive Power Control method, a kind of do not need the to carry out complicated conversion such as Vector Rotation variation and the double-fed wind power generator Reactive Power Control method of calculating are provided.

If the stator voltage of generator, electric current, flux linkage vector are

With

Rotor voltage, electric current, flux linkage vector are With Then when steady operation, the electric moter voltage equation is:

${\stackrel{\·}{U}}_s=R_s{\stackrel{\·}{I}}_s+j{\mathrm{\ω}}_s{\stackrel{\·}{\mathrm{\ψ}}}_s---\left(1\right)$

${\stackrel{\·}{U}}_r=R_r{\stackrel{\·}{I}}_r+j({\mathrm{\ω}}_s-{\mathrm{\ω}}_r){\stackrel{\·}{\mathrm{\ψ}}}_s---\left(2\right)$

R wherein _s, R _r, ω _s, ω _rBe respectively motor stator, the every phase resistance of rotor, the angular velocity of rotation in stator synchronous rotary magnetic field, rotor magnetic field, vector is relatively static in the space in the formula, all with the synchronizing speed rotation, under synchronously rotating reference frame dq axle system

U _sd＝R _sI _sd+ω _sψ _sq (3)

U _sq＝R _sI _sq-ω _sψ _sd (4)

ψ wherein _Sd, ψ _SqFor

Component on d, q axle, its value is:

ψ _sd＝L _sI _sd+L _MI _rd (5)

ψ _sq＝L _sI _sq+L _MI _rq (6)

Wherein, I _Sd, I _SqBe respectively

Component on d, q axle, I _Rd, I _RqBe respectively

Component on d, q axle.L _sBe stator winding self-induction, L _MBe the rotor winding mutual inductance, can be got by formula (3), (4):

$I_{\mathrm{sd}}=\frac{U_{\mathrm{sd}}-{\mathrm{\ω}}_s{\mathrm{\ψ}}_{\mathrm{sq}}}{R_s}---\left(7\right)$

$I_{\mathrm{sq}}=\frac{U_{\mathrm{sq}}+{\mathrm{\ω}}_s{\mathrm{\ψ}}_{\mathrm{sd}}}{R_s}---\left(8\right)$

(7), (8) substitution (5), (6) can be got

$U_{\mathrm{sd}}=\frac{R_s{\mathrm{\ψ}}_{\mathrm{sd}}-R_s{L}_M{I}_{\mathrm{rd}}}{L_s}+{\mathrm{\ω}}_s{\mathrm{\ψ}}_{\mathrm{sq}}---\left(9\right)$

$U_{\mathrm{sq}}=\frac{R_s{\mathrm{\ψ}}_{\mathrm{sq}}-R_s{L}_M{I}_{\mathrm{rq}}}{L_s}-{\mathrm{\ω}}_s{\mathrm{\ψ}}_{\mathrm{sd}}---\left(10\right)$

And the reactive power Q of stator side is:

Q＝U _sqI _sd-U _sdI _sq (11)

Formula (9), (10) substitution (11) are got:

$Q=\frac{{\mathrm{\ω}}_s}{L_s}({\mathrm{\ψ}}_s^2-{\mathrm{\ψ}}_{\mathrm{sd}}{I}_{\mathrm{rd}}-{\mathrm{\ψ}}_{\mathrm{sq}}{I}_{\mathrm{rq}})---\left(12\right)$

If X ₁=ψ _SdI _Rd+ ψ _SqI _Rq

Then

$Q=\frac{{\text{\ω}}_s}{L_s}({\mathrm{\ψ}}_s^2-X_1)---\left(13\right)$

When motor parallel arrived infinitely great electrical network, Us was constant, ψ _sCan be approximately constant, Ls, ω _sAlso be constant, so the reactive power of generator unit stator output only and X ₁Relevant, control X ₁Just can realize that Fig. 2 is stator magnetic linkage to the idle control of stator output, the distribution of rotor current vector on the dq synchronization rotational coordinate ax, as shown in Figure 2,

Wherein A, B are respectively With the angle of d axle,

Be the angle between stator magnetic linkage and rotor current vector, then double-fed wind power generator Reactive Power Control method such as Fig. 3.

A generator rotor excitation current given in advance

Under wind turbine drags, be connected to the grid, then can measure voltage, electric current U, the I of stator output, and calculate the reactive power Q of stator output, according to flux linkage model, can calculate stator magnetic linkage.

Given stator output reactive power is Q*, and relatively the reactive power Q of Q* and stator output obtains the two difference, utilizes PI to regulate the set-point that algorithm can obtain rotor excitation current Ir

Controller is according to set-point Regulate the current transformer control impuls, obtain the output of rotor excitation current.

Because the present invention adopts technique scheme, in the wind power generation steady operation, need not to carry out complicated conversion and the calculating such as Vector Rotation variation, current control module control susceptibility is lower, the circuit parameter of converter system, to measure time-delay less on the impact that Current Control all has, although real-time and the precision of control decrease, control technology is very simple, therefore the cost of controller also reduces, and is fit to the application of low power wind driven generator.

Description of drawings

Fig. 1 be double-fed wind power generator the basic hardware topological structure;

Fig. 2 is according to double-fed aerogenerator stator magnetic linkage of the present invention, rotor current vector correlation figure;

Fig. 3 is according to double-fed wind power generator Reactive Power Control block diagram of the present invention.

Embodiment

The present invention is described in further detail below in conjunction with specific embodiment.

The basic hardware topological structure of double-fed wind power generator as shown in Figure 1, electrical network is the rotor power supply of double-fed wind power generator by current transformer, generator is under blower fan drives, its stator is meritorious and idle to electrical network output.It is to utilize zero load and locked rotor test to measure the parameter of electric machine that generator parameter mensuration has a lot of known methods, the most frequently used method.Utilize the method in the document 1, also can obtain the parameter of this generator, for example stator resistance R _s, stator winding inductance L s, rotor winding mutual inductance L _MEtc. parameter.

Document 1: " estimation of asynchronous motor parameter and measurement in the vector control system ", Ma Xiaoliang, electric drive, the 7th phase of the 40th volume in 2010.

Can detect generator rotor position by photoelectric coded disk, and then can obtain rotor speed by differential, thereby obtain motor slip frequency ω ₂And the observation stator magnetic linkage Three class methods are arranged: direct Detection Method, indirect calculation method, based on the method for high-frequency signal injection.Direct Detection Method is to embed magneto sensor at the air gap place of stator α axle and β axle, and direct-detection goes out stator magnetic linkage at the component ψ of stator α axle and β axle _{α s}And ψ _{β s}Can try to achieve accordingly the effective value ψ of stator magnetic linkage _sAnd with the angle of α axle.The indirect calculation method is set up Flux Observation Model by physical quantitys such as stator voltage, electric currents, calculates in real time effective value and the phase place of stator magnetic linkage in control.Traditional method is to adopt voltage model to observe stator magnetic linkage, and obtains stator magnetic linkage by the integral and calculating to back-emf signal.To have a parameter of electric machine that needs few and do not need the advantage of rotary speed information to be widely applied owing to this method, and its expression formula is:

ψ _s＝∫(U _s-i _sR _s)dt

Need to inject high-frequency signal at the stator winding of asynchronous machine based on the method that high-frequency signal injects, the non-ideal characteristic by motor such as magnetic saturation effect etc. obtain effective value and the direction of motor magnetic linkage.

To the double-fed wind power generator Reactive Power Control time, at first utilize zero load and locked rotor test to measure the motor stator resistance R _s, stator winding inductance L s, rotor winding mutual inductance L _MEtc. parameter, a generator rotor excitation current I given in advance _r, under wind turbine drags, be connected to the grid, then can measure voltage, electric current U, the I of stator output, and calculate the reactive power Q of stator output, according to flux linkage model, can calculate the effective value ψ of stator magnetic linkage _sWith in α β reference axis phase place, it is transformed on the dq rotating shaft, with rotor excitation current I given in advance _rAlso be mapped on the dq rotating shaft, then on this reference axis, the angle of stator magnetic linkage and rotor excitation current is Order

Given stator output reactive power is Q ^*, compare Q ^*With the reactive power Q of stator output, obtain the poor Δ Q=Q of the reactive power of given stator output reactive power and the actual output of stator ^*-Q utilizes PI incremental adjustments algorithm can obtain X ₁Increment Delta X _KValue,

$\mathrm{\Δ}{X}_K=K_Q(\mathrm{\Δ}{Q}_K-\mathrm{\Δ}{Q}_{k-1}+\frac{T}{T_Q}\mathrm{\Δ}{Q}_K)$

Wherein, K _QBe proportionality coefficient, T _QBe integration time constant, can determine by conventional parameter tuning method.And Δ Q _K, Δ Q _K-1Be reactive power poor of given stator output reactive power and the actual output of stator in the K time and the K-1 time sampling period, T is the time in a sampling period.The controlled quentity controlled variable that then should input is X _K=X ₁+ Δ X _K, order

At X _KDuring for certain value, unlikely too large for making the rotor current effective value, can be given

Be unspecified angle between 0 to 60 degree

Because the phase place of stator magnetic linkage draws according to flux linkage model, making the d axle clamp angle of itself and synchronous rotary axle is A,

Be the angle between stator magnetic linkage on the dq axle and rotor current vector, therefore can obtain the phase place of rotor current on the dq axle, according to Fig. 2, as can be known, it and d axle clamp angle are

And rotor current vector effective value is

Thereby, under the control action of current-variable controller, to the output of rotor winding with d axle clamp angle be

Effective value is

The rotor current of slip frequency, the i.e. reactive power of exportable needs.

Claims (4)

1. the control method of a double-fed wind power generator reactive power, described double-fed wind power generator has double feedback electric engine, and this motor has the stator to mains supply, and described electrical network has the voltage of rated value; Driving rotor with described stator coupling, described rotor one end is connected to wind turbine by change-speed gearing, described rotor winding is the three-phase wound rotor winding, electrical network is the rotor power supply by current transformer, described current transformer is connected with the rotor winding with collector ring by brush, and described method comprises the steps:

(a) utilize zero load and locked rotor test to measure the motor stator resistance R _s, stator winding inductance L s, rotor winding mutual inductance L _M, turn step (b);

(b) rotor excitation current given in advance

Under wind turbine drags, be connected to the grid, turn step (c);

(c) given stator output reactive power is Q ^*, turn step (d);

(d) given sampling period T detects generator rotor position by photoelectric coded disk, and then can obtain rotor speed by differential, thereby obtains motor slip frequency ω ₂, measure voltage, the current phasor U of the K time output of stator _K, I _K, and calculate the reactive power Q that stator is exported for the K time _K, wherein, K=1,2 ..., compare Q ^*With Q _K, obtain Q ^*With Q _KPoor Δ Q _K=Q ^*-Q _K, and with Δ Q _KStore in the memory cell of controller, measure or according to flux linkage model, calculate the effective value ψ of stator magnetic linkage _sAnd the phase place on static α β reference axis, its conversion to the dq synchronization rotational coordinate ax, is obtained the stator magnetic linkage vector and d axle clamp angle is A, with rotor excitation current

Also be mapped on the dq synchronization rotational coordinate ax, on the dq synchronization rotational coordinate ax, can obtain the angle of stator magnetic linkage and rotor excitation current

Order

Turn step (e);

(e) at Δ Q _KThe basis on, utilize PI incremental adjustments algorithm can obtain X ₁Increment Delta X _K, turn step (f);

(f) obtain X _K=X ₁+ Δ X _K, turn step (g);

(g) given For unspecified angle between 0 to 60 degree, under the control action of current-variable controller, upper and d axle clamp angle is to rotor winding output transform to synchronization rotational coordinate ax dq

Effective value is

Frequency is slip frequency ω ₂Rotor current; Turn step (h);

(h) make K=K+1, dq makes at synchronization rotational coordinate ax

Effective value be

Itself and d axle clamp angle are

Turn step (c).

2. the control method of double-fed wind power generator reactive power as claimed in claim 1, wherein in the step (e), PI incremental adjustments algorithm obtains X ₁Increment Delta X _KMethod be:

$\mathrm{\Δ}{X}_K=K_Q(\mathrm{\Δ}{Q}_K-{\mathrm{\ΔQ}}_{K-1}+\frac{T}{T_Q}\mathrm{\Δ}{Q}_K)$

Wherein, K _QBe proportionality coefficient, T _QBe integration time constant, can determine by conventional parameter tuning method, and Δ Q _K, Δ Q _K-1Be reactive power poor of given stator output reactive power and the actual output of stator in the K time and the K-1 time sampling period, T is the time in a sampling period.

3. the control method of double-fed wind power generator reactive power as claimed in claim 1, wherein in the step (C), flux linkage model is the u-i Voltage-Current model.

4. the control method of double-fed wind power generator reactive power as claimed in claim 1 wherein in the step (d), embeds magneto sensor at the air gap place of stator α axle and β axle, and direct-detection goes out stator magnetic linkage at the component ψ of stator α axle and β axle _{α s}And ψ _{β s}, can try to achieve accordingly the effective value ψ of stator magnetic linkage _sAnd with the angle of α axle.

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