CN102355192A - 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 impact on 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

Receive the generally attention of countries in the world as the wind energy of renewable green energy resource growing in energy resource consumption, that environmental pollution is day by day serious today, and wind generating technology also becomes the focus that various countries scholar in recent years competitively studies.Wind energy is a kind of frequent energy at random that changes; 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 have traditional constant-speed and constant-frequency wind generating technology incomparable superiority; 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 through two PWM current transformers in the rotor-side of double-fed generator to carry out excitation, through regulating effective value, phase place and the frequency of exciting current, realizes the meritorious control with 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 through collector ring; Through frequency, the effective value of control rotor current, phase place and phase sequence are utilized two PWM current transformers; Through the SPWM control technology; Can obtain sinusoidal wave rotor current,, realize that stator side output is gained merit and the control of reactive power to reduce the harmonic torque in the generator.

Because there is the coupling on the magnetic circuit in the circuit of double-fed generator, and the Mathematical Modeling its three phase coordinate system under be non-linear, the time change high order system.For realize gaining merit, idle decoupling zero control; Usually adopt vector control method; Vector control is theoretical according to transform vector; Adopt and press stator field direction orientation; Is the rotor current resolution of vectors two mutually perpendicular current components in synchronous rotating frame, realizes 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 calculating such as vector rotation change; And current control module control susceptibility is higher; The circuit parameter of converter system, measurement time-delay and phase-locked loop performance all have bigger influence 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 take place in controller stability, strengthened the debugging difficulty of controller parameter.

Summary of the invention

The objective of the invention is to overcome the deficiency of existing double-fed wind power generator Reactive Power Control method, a kind of conversion of complicacies such as vector rotation change and double-fed wind power generator Reactive Power Control method of calculating of need not carrying out is provided.

Let the generator stator voltage, current, flux vector

and

rotor voltage, current, flux vector

and

in the steady-state operation, the motor 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 of the synchronous rotating magnetic field of stator, rotor rotating magnetic field, vector is static relatively 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 get 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 a stator magnetic linkage to the idle control of stator output, the distribution of rotor current vector on the dq synchronization rotational coordinate ax can be known by Fig. 2,

Where A, B, respectively

and the d-axis angle,

for the stator flux and the rotor current vector angle between the double-fed wind generator reactive power control method shown in Figure 3.

Given in advance a generator rotor excitation current

drag the wind turbine under the grid, the stator can be measured output voltage, current U, I, and calculate the output of the stator reactive power Q, according to the magnetic chain model, calculate the stator flux.

Given the stator output reactive power is Q *, Q * compared with the stator output reactive power Q, get the difference between the two, can be obtained using the PI controller algorithm rotor excitation current Ir setpoint

controller based on the given value

regulation converter control pulses to obtain an output current of the rotor excitation.

Because the present invention adopts technique scheme; In the wind power generation steady operation; Need not to carry out complicated conversion and calculating such as vector rotation change; Current control module control susceptibility is lower; The circuit parameter of converter system, to measure time-delay less to the influence that Current Control all has, though the 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

Below in conjunction with specific embodiment the present invention is done further detailed description.

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 through current transformer, generator drives down at blower fan, 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 method, 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, 2010 the 40th the 7th phases of volume.

Can detect generator rotor position through photoelectric coded disk, and then can obtain rotor speed, thereby obtain motor slip frequency ω through differential ₂While observing the stator flux

There are three ways: direct detection method, indirect calculation method, based on high frequency signal injection method.Direct Detection Method is to embed magneto sensor at the air gap place of stator α axle and β axle, directly detects the component ψ of stator magnetic linkage at stator α axle and β axle _{α s}And ψ _{β s}Can try to achieve the effective value ψ of stator magnetic linkage in view of the above _sAnd with the angle of α axle.The indirect calculation method is set up the flux observation model through physical quantitys such as stator voltage, electric currents, in control, calculates the effective value and the phase place of stator magnetic linkage in real time.Traditional method is to adopt voltage model to observe stator magnetic linkage, and obtains stator magnetic linkage through the integral and calculating to back-emf signal.Owing to this method have the parameter of electric machine that needs few with do not need the advantage of rotary speed information to obtain extensive use, its expression formula is:

ψ _s＝∫(U _s-i _sR _s)dt

Method based on high-frequency signal injects need be injected high-frequency signal at the stator winding of asynchronous machine, and non-ideal characteristic through motor such as magnetic saturation effect etc. obtain the 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, the given in advance rotor excitation current I of generator _r, drag down at wind turbine, 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 the magnetic 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 given in advance rotor excitation current I _rAlso be mapped on the dq rotating shaft, then on this reference axis, the angle of stator magnetic linkage and rotor excitation current does

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 confirm through 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.Then the controlled quentity controlled variable that should import is X _K=X ₁+ Δ X _K, order

At X _KDuring for certain value, unlikely too big 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 the magnetic linkage model, making its d axle clamp angle with synchronous rotating shaft 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,, can know that it and d axle clamp angle do according to Fig. 2

And rotor current vector effective value does Thereby, under the control action of current-variable controller, with d axle clamp angle do to the output of rotor winding

Effective value does

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, said double-fed wind power generator has double feedback electric engine, and this motor has the stator to mains supply, and said electrical network has the voltage of rated value; Driving rotor with said stator coupling; Said rotor one end is connected to wind turbine through change-speed gearing; Said rotor winding is a three-phase phase-wound rotor winding; Electrical network is the rotor power supply through current transformer; Said current transformer is connected with the rotor winding with collector ring through brush, and said 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 _MEtc. parameter, change step (b);

(B) given in advance a rotor excitation current

drag in a wind turbine under the grid, go to step (c);

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

(d) given sampling period T detects generator rotor position through photoelectric coded disk, and then can obtain rotor speed through 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(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, calculate the effective value ψ of stator magnetic linkage according to the magnetic linkage model _sAnd the phase place on static α β reference axis, it is converted on the dq synchronization rotational coordinate ax, obtain the stator magnetic linkage vector and d axle clamp angle is A, with rotor excitation current

Also be mapped on the dq rotating shaft, on this reference axis, can obtain the angle of stator magnetic linkage and rotor excitation current

Order

Change step (e);

(e) at Δ Q _KThe basis on, utilize PI incremental adjustments algorithm can obtain the increment Delta X of X1 _K, change step (f);

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

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

Effective value does Frequency is slip frequency ω ₂Rotor current; Change step (h);

(h) to make K = K +1, in the synchronous rotating dq axes on orders

valid values

with the d-axis angle go to 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:

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

Wherein, K _QBe proportionality coefficient, T _QBe integration time constant, can confirm through 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), the magnetic linkage model is a u-i electric current and voltage model.

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

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