CN102723727B - Grid connection control method of double-fed wind-driven generator - Google Patents

Abstract

The invention discloses a grid connection control method of a double-fed wind-driven generator. The method comprises the steps of: acquiring values of grid voltage Ug, stator three-phase voltage Us, rotor three-phase current Ir and rotor position angle thetam, transforming to a synchronous rotating coordinate system, carrying out grid voltage phase outer loop control, carrying out grid voltage amplitude outer loop control, carrying out rotor current inner loop control, and determining whether amplitude error epsilonv of stator voltage and grid voltage, phase error epsilontheta of stator voltage and grid voltage and sustainable cycles are in a set range or not. If yes, grid connection is realized through grid connection cocontactor closing. According to an embodiment provided by the invention, the control method is easy, stable and reliable. As the controller structure is simplified, grid connection is easy to be realized. Simultaneously, rotor current decoupling control is further realized, thereby convenience is provided to active and reactive power decoupling control mode switching after grid connection. Power mode smooth switching is realized by adopting a state parameter transfer way when mode switching is carried out after grid connection.

Description

Double-fed wind power generator grid-connected control method

Technical field

The present invention relates to technical field of wind power generation, be specifically related to a kind of double-fed wind power generator grid-connected control method.

Background technology

The variable speed constant frequency doubly-fed induction wind driven generator of grid type is a kind of wind turbine generator being most widely used, and it is to be also applied at present one of technology the most ripe in wind turbine generator that the two PWM of the back-to-back formula supporting with it hand over orthogonal rotor-exciting technology.

The efficient utilization of wind energy has become the focus of current research, at wind speed, reach while cutting people's wind speed, how fast and reliable realize the synchronously grid-connected of wind turbine generator, how to reduce grid-connected impulse current, also existing many research.For the variable speed constant frequency doubly-fed induction wind driven generator of grid type, application at present has two kinds of interconnection technologies more widely, and a kind of is stator interconnection technology, and a kind of is the soft interconnection technology of rotor.Stator interconnection technology is applied to the wind-powered electricity generation set grid-connection under desirable electrical network condition conventionally; And the soft interconnection technology of rotor is applied to occur Low Dropout conventionally in running, wind driven generator set converter is realized in the process of restarting.

And about stator interconnection technology, owing to being most widely used, also detailed introduction has been made in existing many patent applications, a kind of grid-connected control method of double-fed wind power generator for example, is disclosed in the patent document that publication number is CN102005782A, this application provides a kind of double circle controling mode by electrical network outer shroud and current inner loop to realize the tracking of stator voltage amplitude to line voltage amplitude, but this application is to realize in the situation that hypothesis initial position of rotor is known, in addition voltage magnitude outer shroud has adopted proportional and integral controller (pi regulator) to add the control mode of feedforward term, to cause that given value of current impacts in the step of starting stage like this, in addition, in the process of following the tracks of, existence due to Proportional coefficient K p in pi regulator, the adjustment process of following the tracks of will be increased, be unfavorable for flexible grid-connected.Equally, the patent document that publication number is CN101499665A is also in the situation that initial position of rotor is known, to realize grid-connectedly, all reckons without the sight of initial position of rotor the unknown.

Again for example, publication number is to disclose a kind of speed-varying frequency constant dual feedback wind power generation system and grid-connected control method thereof in the Chinese patent document of CN101267117A, and this application provides a kind of interconnection technology based on voltage magnitude compensator and rotor position angle compensator to realize the synchronously grid-connected of wind turbine generator.Its voltage magnitude compensator is usingd line voltage and stator voltage amplitude and as reference value and the value of feedback of pi regulator, is regulated control respectively, and output is as the amplitude of exciting current; And rotor position angle compensator is usingd torque current as control object, by pi regulator, torque current being controlled is 0, correct to guarantee rotor position angle.Adopted the control strategy of two outer shrouds, two interior rings, realized the tracking to line voltage amplitude and phase place, but, because it is when carrying out electric network voltage phase tracking by rotor-position angle compensation,, there is certain risk, especially in stator phase sequence mistake in the contrast feedback that does not have stator voltage phase place and electric network voltage phase, likely and network process in, because impulse current is excessive, cause grid-connected failure.

Because grid-connected wind-powered electricity generation unit utilization ratio failed or that grid-connected overlong time causes is low, become the problem that wind energy turbine set more and more can not be ignored.Shorten grid-connected lock in time, reduce grid-connected impulse current, improve grid-connected reliability, guarantee that the safe operation of wind turbine generator has become the important issue of interconnection technology.

Summary of the invention

The invention provides a kind of double-fed wind power generator grid-connected control method, can solve the interior ring of realizing line voltage amplitude, the control of phase place outer shroud and realize rotor current in the situation that of initial position of rotor the unknown and control.

The invention provides a kind of double-fed wind power generator grid-connected control method, comprise step:

A: obtain line voltage U _g, stator three-phase voltage U _s, rotor three-phase electric current I _rand rotor position angle θ _m;

B: by line voltage U _g, stator three-phase voltage U _s, rotor three-phase electric current I _rtransform to respectively synchronous rotating frame;

C: with line voltage U _gwith stator three-phase voltage U _sphase theta with respect to rest frame α axle ₁with phase theta _srespectively as reference set-point and value of feedback on pure integrator input, using the output of this pure integrator as initial position angle of rotor θ ₀and with electrical network phase angle θ ₁with rotor position angle θ _mthrough adder stack, obtain rotor three-phase electric current I _rbe transformed into the coordinate transform phase angle θ of synchronous rotating frame _slip, form electric network voltage phase outer shroud and control;

D: by line voltage d axle component U _gdwith stator three-phase voltage d axle component U _sdrespectively as reference set-point and the value of feedback of pure integrator input, the reference set-point I using the output of this pure integrator as rotor current q axle component ^* _rq, the reference set-point I of setting rotor current d axle component ^* _rdbe 0, form line voltage amplitude outer shroud and control;

E: by the reference set-point I of rotor current q axle component ^* _rqwith rotor current q axle component value of feedback I _rqthrough adder, export the set-point U that proportional and integral controller obtains rotor voltage q axle component to ^* _rq, by the reference set-point I of rotor current d axle component ^* _rdwith rotor current d axle component value of feedback I _rdthrough adder, export the set-point U that proportional and integral controller obtains rotor voltage d axle component to ^* _rd, form ring in rotor current and control;

F: the amplitude error ε of judgement stator voltage and line voltage _v, phase error _θand whether lasting cycle in setting range, if so, grid-connected contactor close a floodgate realize grid-connected.

Preferably, in described step F, grid-connected contactor closes a floodgate to realize and also comprises step after grid-connected:

System is switched to power decoupled control model.

Preferably, amplitude error ε in described step F _vbe less than 10V, phase error _θbe less than 5 °, lasting cycle is greater than 5 weeks.

Technique scheme can be found out, because the embodiment of the present invention adopts the control mode of encircling in two outer shroud lists, realize the outer shroud of line voltage amplitude and phase place is controlled, so the control method of the embodiment of the present invention is compared with traditional control method, simple, reliable and stable.On ring controller, adopted pure integral controller outside, simplified the structure of controller, be easy to realize.Realize synchronous grid-connected in, also realized the decoupling zero of rotor current and controlled, the providing convenience property of decoupling zero control model of, reactive power meritorious for switching to after grid-connected.When grid-connected rear pattern is switched, the mode that has adopted state parameter to transmit, has realized taking over seamlessly of power mode.

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, to the accompanying drawing of required use in embodiment or description of the Prior Art be briefly described below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skills, do not paying under the prerequisite of creative work, can also obtain according to these accompanying drawings other accompanying drawing.

Fig. 1 is the flow chart of double-fed wind power generator grid-connected control method in the embodiment of the present invention;

Fig. 2 is the theory diagram of the grid-connected control of double-fed wind power generator in the embodiment of the present invention;

Fig. 3 is the control principle block diagram of line voltage amplitude tracking outer shroud in the embodiment of the present invention;

Fig. 4 is the control principle block diagram that in the embodiment of the present invention, electric network voltage phase is followed the tracks of outer shroud;

Fig. 5 is stator α in the embodiment of the present invention _sβ _scoordinate system, rotor α _rβ _rthe graph of a relation of coordinate system and synchronous rotary dq coordinate system;

Fig. 6 is that the grid-connected rear system of the embodiment of the present invention switches to theory diagram meritorious, that reactive power decoupling zero is controlled by the synchronous tracing mode of line voltage.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is only the present invention's part embodiment, rather than whole embodiment.Embodiment based in the present invention, those of ordinary skills, not making all other embodiment that obtain under creative work prerequisite, belong to the scope of protection of the invention.

The embodiment of the present invention provides a kind of double-fed wind power generator grid-connected control method, and as shown in Figure 1, the method comprises:

Step 11: obtain line voltage U _g, stator three-phase voltage U _s, rotor three-phase electric current I _rand rotor position angle θ _m.

In this step, utilize two groups of two current sensors to gather two-phase rotor current signal I _ra, I _rbwith two-phase stator current signal I _sa, I _sb, and obtain third phase rotor current signal I by calculating _rcwith third phase stator current signal I _sc, two groups of 4 voltage sensors gather grid line voltage signal U _gab, U _gbcwith stator line voltage signal U _sab, U _sbc, and obtain three phase network voltage signal U by calculating _ga, U _gb, U _gcwith stator voltage signal U _sa, U _sb, U _sc; Utilize an increment photoelectric code disk to obtain rotor position angle θ _msignal.

Step 12: by line voltage U _g, stator three-phase voltage U _s, rotor three-phase electric current I _rtransform to respectively synchronous rotating frame.

In this step, line voltage U under two-dimentional three-axis reference _g, stator three-phase voltage U _s, rotor three-phase electric current I _rthrough clarke, conversion obtains each voltage, the current value under rest frame (α β coordinate system); Under rest frame, line voltage U _g, stator voltage U _s, rotor current I _rthrough park, conversion obtains each voltage, the current value under synchronous rotating frame (dq coordinate system).

Step 13: with line voltage U _gwith stator three-phase voltage U _sphase theta with respect to rest frame α axle ₁with phase theta _srespectively as reference set-point and value of feedback on pure integrator input, using the output of this pure integrator as initial position angle of rotor θ ₀and with electrical network phase angle θ ₁with rotor position angle θ _mthrough adder stack, obtain rotor three-phase electric current I _rbe transformed into the coordinate transform phase angle θ of synchronous rotating frame _slip, form electric network voltage phase outer shroud and control.It is 0 integrator that so-called pure integrator is proportionality coefficient.

As shown in Figure 2, Figure 4 shows, in this step, mains voltage signal U _gthrough phase-locked loop computing, obtain line voltage vector phase theta with respect to α axle under its static α β coordinate system ₁, according to line voltage directional vector control principle, the d axle of synchronous rotating frame is oriented on line voltage vector, and with its synchronous rotary; Meanwhile, by stator voltage signal U _sby phase-locked loop computing, obtain stator voltage vector angular position theta with respect to α axle under its static α β coordinate system _s; Photoelectric code disk signal is through the angular position theta of DSP (∫ dt module in Fig. 2) acquisition rotor _m, and rotor is θ with respect to the actual bit angle setting of line voltage α axle _r=θ ₀+ θ _m; Thereby can be for the slippage angle θ of coordinate transform _slip=θ ₁-θ _r.Slippage phase angle is herein coordinate transform phase angle.In Fig. 2, slippage angle computing module is shown in the structure in Fig. 4.

Step 14: by line voltage d axle component U _gdwith stator three-phase voltage d axle component U _sdrespectively as reference set-point and the value of feedback of pure integrator input, the reference set-point I using the output of this pure integrator as rotor current q axle component ^* _rq, the reference set-point I of setting rotor current d axle component ^* _rdbe 0, form line voltage amplitude outer shroud and control;

Shown in Fig. 2 and Fig. 3, three phase network voltage, stator voltage, rotor current, by Parker's coordinate transform, are converted under synchronous rotating frame, so there is dq axle line voltage U _gdq, dq axle stator voltage U _sdq, dq axle rotor current I _rdq; By line voltage d axle component U _gdsignal is as with reference to set-point, stator three-phase voltage d axle component U _sdsignal is as value of feedback, by pure integral controller, adjuster output is as the reference set-point of rotor current q axle component, the stream of setting rotor current d component is made as 0 with reference to set-point, and realize the control to rotor excitation current amplitude by the pi regulator of current inner loop, thereby realize the synchronous tracking of stator voltage to line voltage amplitude.

Step 15: by the reference set-point I of rotor current q axle component ^* _rqwith rotor current q axle component value of feedback I _rqthrough adder, export the set-point U that proportional and integral controller obtains rotor voltage q axle component to ^* _rq, by the reference set-point I of rotor current d axle component ^* _rdwith rotor current d axle component value of feedback I _rdthrough adder, export the set-point U that proportional and integral controller obtains rotor voltage d axle component to ^* _rd, form ring in rotor current and control;

As shown in Figure 2, in this step, interior ring is rotor dq current inner loop, has adopted traditional proportional and integral controller.The output of line voltage amplitude tracking outer shroud is as the reference set-point of interior ring q shaft current, and for controlling the amplitude of exciting current, and rotor d shaft current remains 0 with reference to set-point, guarantees that torque current is 0; Electric network voltage phase is followed the tracks of the output of outer shroud as initial position angle of rotor signal, one side is as Parker's coordinate transform phase angle of interior circular current feedback signal, on the other hand as anti-Parker's coordinate transform phase angle of interior ring output voltage, thereby realize the adjustment of stator voltage phase place.

Step 16: the amplitude error ε of judgement stator voltage and line voltage _v, phase error _θand whether lasting cycle in setting range, described amplitude error ε _vbe less than 10V, phase error _θbe less than 5 °, lasting cycle is greater than 5 weeks.If so, perform step 17: grid-connected contactor combined floodgate is realized grid-connected.If not, rejudge.

Step 18: system is switched to power decoupled control model.

Below in conjunction with formula, the control method in the embodiment of the present invention is made to concrete introduction.

As shown in Figure 2, the present invention be take line voltage directional vector and is controlled the Mathematical Modeling of introducing rotor-side field power supply as example, adopt Motor convention, so, suc as formula 1, formula 2 is depicted as stator, rotor flux and stator, the rotor voltage Mathematical Modeling of DFIG under synchronous rotating frame:

$\left\{\begin{array}{c}{\mathrm{\ψ}}_{\mathrm{sdq}}=I_{\mathrm{sdq}}{L}_s+I_{\mathrm{rdq}}{L}_m\\ {\mathrm{\ψ}}_{\mathrm{rdq}}=I_{\mathrm{sdq}}{L}_m+I_{\mathrm{rdq}}{L}_r\end{array}\right.$ Formula 1

$\left\{\begin{array}{c}{V}_{\mathrm{sdq}}=I_{\mathrm{sdq}}{R}_s+\frac{d}{\mathrm{dt}}{\mathrm{\ψ}}_{\mathrm{sdq}}+j{\mathrm{\ω}}_1{\mathrm{\ψ}}_{\mathrm{sdq}}\\ V_{\mathrm{rdq}}=I_{\mathrm{rdq}}{R}_r+\frac{d}{\mathrm{dt}}{\mathrm{\ψ}}_{\mathrm{rdq}}+j{\mathrm{\ω}}_{\mathrm{slip}}{\mathrm{\ψ}}_{\mathrm{rdq}}\end{array}\right.$ Formula 2

Can be for the rotor voltage equation of vector control, as shown in Equation 3 by formula 1 and formula 2:

$\left\{\begin{array}{c}{V}_{\mathrm{rd}}=I_{\mathrm{rd}}{R}_r+{\mathrm{\σL}}_r\frac{d}{\mathrm{dt}}{I}_{\mathrm{rd}}+\frac{L_m}{L_s}\frac{d}{\mathrm{dt}}{\mathrm{\ψ}}_{\mathrm{sd}}-{\mathrm{\ω}}_{\mathrm{slip}}{\mathrm{\σL}}_r{I}_{\mathrm{rq}}-{\mathrm{\ω}}_{\mathrm{slip}}\frac{L_m}{L_s}{\mathrm{\ψ}}_{\mathrm{sq}}\\ V_{\mathrm{rq}}=I_{\mathrm{rq}}{R}_r+{\mathrm{\σL}}_r\frac{d}{\mathrm{dt}}{I}_{\mathrm{rq}}+\frac{L_m}{L_s}\frac{d}{\mathrm{dt}}{\mathrm{\ψ}}_{\mathrm{sq}}+{\mathrm{\ω}}_{\mathrm{slip}}{\mathrm{\σL}}_r{I}_{\mathrm{rd}}+{\mathrm{\ω}}_{\mathrm{slip}}\frac{L_m}{L_s}{\mathrm{\ψ}}_{\mathrm{sd}}\end{array}\right.$ Formula 3

When systematic steady state moves:

$\frac{d}{\mathrm{dt}}{\mathrm{\ψ}}_{\mathrm{sd}}=0,$ $\frac{d}{\mathrm{dt}}{\mathrm{\ψ}}_{\mathrm{sq}}=0$ Formula 4

So formula 3 can be reduced to:

$\left\{\begin{array}{c}{V}_{\mathrm{rd}}=I_{\mathrm{rd}}{R}_r+{\mathrm{\σL}}_r\frac{d}{\mathrm{dt}}{I}_{\mathrm{rd}}-{\mathrm{\ω}}_{\mathrm{slip}}{\mathrm{\σL}}_r{I}_{\mathrm{rq}}-{\mathrm{\ω}}_{\mathrm{slip}}\frac{L_m}{L_s}{\mathrm{\ψ}}_{\mathrm{sq}}\\ V_{\mathrm{rq}}=I_{\mathrm{rq}}{R}_r+{\mathrm{\σL}}_r\frac{d}{\mathrm{dt}}{I}_{\mathrm{rq}}+{\mathrm{\ω}}_{\mathrm{slip}}{\mathrm{\σL}}_r{I}_{\mathrm{rd}}+{\mathrm{\ω}}_{\mathrm{slip}}\frac{L_m}{L_s}{\mathrm{\ψ}}_{\mathrm{sd}}\end{array}\right.$ Formula 5

When generator connecting in parallel with system steady operation, stator resistance can be ignored, stator magnetic linkage constant amplitude, therefore:

$V_{\mathrm{sdq}}=I_{\mathrm{sdq}}{R}_s+\frac{d}{\mathrm{dt}}{\mathrm{\ψ}}_{\mathrm{sdq}}+j{\mathrm{\ω}}_1{\mathrm{\ψ}}_{\mathrm{sdq}}\≈j{\mathrm{\ω}}_1{\mathrm{\ψ}}_{\mathrm{sdq}}$ Formula 6

Meanwhile, according to the principle of vector control based on line voltage d axle orientation, obtain V _sq=0, therefore can obtain:

$\left\{\begin{array}{c}{\mathrm{\ψ}}_{\mathrm{sd}}=\frac{V_{\mathrm{sq}}}{{\mathrm{\ω}}_1}=0\\ {\mathrm{\ψ}}_{\mathrm{sq}}=-\frac{V_{\mathrm{sd}}}{{\mathrm{\ω}}_1}\end{array}\right.$ Formula 7

By formula 7, formula 5 further can be reduced to:

$\left\{\begin{array}{c}{V}_{\mathrm{rd}}=R_r{I}_{\mathrm{rd}}+{\mathrm{\σL}}_r\frac{{\mathrm{dI}}_{\mathrm{rd}}}{\mathrm{dt}}+\frac{{\mathrm{\ω}}_{\mathrm{slip}}{L}_m}{{\mathrm{\ω}}_1{L}_s}{V}_{\mathrm{sd}}-{\mathrm{\ω}}_{\mathrm{slip}}{\mathrm{\σL}}_r{I}_{\mathrm{rq}}\\ V_{\mathrm{rq}}=R_r{I}_{\mathrm{rq}}+{\mathrm{\σL}}_r\frac{{\mathrm{dI}}_{\mathrm{rq}}}{\mathrm{dt}}+{\mathrm{\ω}}_{\mathrm{slip}}{\mathrm{\σL}}_r{I}_{\mathrm{rd}}\end{array}\right.$ Formula 8

Wherein: $\mathrm{\σ}=1-\frac{L_m^2}{L_s{L}_r},$ ω _slip＝ω ₁-ω _r；

V _sd, V _sq, V _rd, V _rqbe respectively d, the q axle component of stator voltage, rotor voltage d, q axle component;

Ψ _sd, Ψ _sq, Ψ _rd, Ψ _rqbe respectively d, the q axle component of stator magnetic linkage, rotor flux d, q axle component;

I _sd, I _sq, I _rd, I _rqbe respectively stator current d, q axle component, rotor current d, q axle component;

R _s, R _rfor stator and rotor resistance parameters;

L _s, L _rbe respectively stator and rotor equivalence two phase winding self-inductions under synchronous rotary dq coordinate system;

L _mfor the mutual inductance between stator and rotor coaxial equivalent winding under synchronous rotary dq coordinate system;

ω ₁, ω _rfor the synchronous rotary angular frequency of line voltage vector, the electric angle frequency of generator amature.

The apparent power S of DFIG stator output _sfor:

$S_s=P_s+{\mathrm{jQ}}_s=\frac{3}{2}{V}_{\mathrm{sdq}}{\hat{I}}_{\mathrm{sdq}}=\frac{3}{2}{V}_{\mathrm{sdq}}\frac{1}{L_s}({\widehat{\mathrm{\ψ}}}_{\mathrm{sdq}}-L_m{\hat{I}}_{\mathrm{rdq}})$ Formula 9

Under d axle stator voltage vector oriented, DFIG stator active power of output P _s, reactive power Q _sbe respectively:

$\left\{\begin{array}{c}{P}_s=\frac{{3L}_m}{{2L}_s}{V}_{\mathrm{sd}}{I}_{\mathrm{rd}}\\ Q_s=-\frac{{3V}_{\mathrm{sd}}}{{2L}_s}(\frac{V_{\mathrm{sd}}}{{\mathrm{\ω}}_1}+L_m{I}_{\mathrm{rq}})\end{array}\right.$ Formula 10

From formula 10, when adopting d axle stator voltage vector oriented control strategy, rotor current d, q axle component become respectively meritorious (torque), idle (excitation) current component, can export decoupling zero control meritorious, reactive power by the independent regulation of rotor current d axle component (torque current component), rotor current q axle component (excitation current component) being controlled to realize DFIG stator.For avoiding grid-connected impulse current, the present invention has adopted idle grid connection mode, and this meritorious, reactive power that just must guarantee stator is 0, namely in rotor current, in ring, must guarantee with reference to set-point I _rd=0, I _rq=V _sd/ (ω ₁* L _m).Yet, excitation current component I _rqreference set-point responsive to generator parameter, easily the error due to calculation of parameter causes that stator voltage amplitude and line voltage amplitude differ larger, and then causes that grid-connected impulse current is excessive, causes grid-connected failure.Therefore, the present invention has adopted the close-loop control mode of line voltage amplitude tracking outer shroud, close with line voltage amplitude to guarantee grid-connected moment stator voltage amplitude, thereby realizes idle grid connection.

As shown in Figure 3, owing to having adopted line voltage directional vector control mode, so the d axle component of line voltage is the phase voltage amplitude of line voltage.One of necessary condition of idle grid connection is that stator voltage amplitude is identical with line voltage amplitude, and the present invention, by the mode of line voltage amplitude tracking closed-loop control, realizes this necessary condition.For guaranteeing idle grid connection, in rotor current, the torque current of ring is with reference to set-point I ^* _rdmust remain 0.The output of following the tracks of outer shroud due to stator voltage amplitude is encircle in q shaft current given, and from formula 10, exciting current is with reference to set-point I ^* _rqwith stator voltage d axle component V _sdbetween be zeroth order transfer function relation, therefore, only need a pure integral controller can realize closed loop compensation and control.

Figure 5 shows that stator α _sβ _scoordinate system, rotor α _rβ _rthe graph of a relation of coordinate system and synchronous rotary dq coordinate system.

As seen from the figure, to be converted to the relation of stator coordinate as follows for the vector under rotor coordinate:

$F_{\mathrm{r\α\β}}{e}^{j({\mathrm{\θ}}_m+{\mathrm{\θ}}_0)}=F_{\mathrm{s\α\β}}$ Formula 11

Control block diagram is known as shown in Figure 2, and system exports the rotor voltage vector of rotor winding to amplitude and phase place by control realize the control to rotor current, and then realizes decoupling zero meritorious, reactive power and control.Due to what control, be the voltage vector that exports rotor winding to, therefore, the locus of the dominant vector under rotor coordinate directly affects the phase place of the stator voltage space vector inducing under stator coordinate.

As shown in Figure 4, line voltage calculates the line voltage space vector angular position theta of output through phase-locked loop ₁as with reference to set-point, the stator voltage that stator voltage phase-locked loop calculates is controlled vector position angle θ _sas feedback signal, by a pure integral adjustment compensator, control, be output as the initial position angle θ of rotor ₀.By initial position angle of rotor θ ₀compensation control, the position angle of rotor voltage dominant vector is changed thereupon, thereby the space bit angle setting of the stator voltage vector of responding in stator side also changes thereupon, and then realize the tracking to line voltage space vector position angle, realize electric network voltage phase and follow the tracks of control.

As long as the error in stator voltage and line voltage amplitude is less than ε _v(common ε _vbelow getting 10 volts), stator voltage and electric network voltage phase error are less than ε simultaneously _θ(conventionally getting in 5 degree), and a lasting n cycle is when above (conventionally getting 5 more than cycle), controller can send grid-connected reclosing command, completes generating set grid-connected.

After being illustrated in figure 6 generator connecting in parallel with system, system switches to theory diagram meritorious, that reactive power decoupling zero is controlled by the synchronous tracing mode of line voltage.When controller receives grid-connected "on" position feedback signal, by the final output state of line voltage amplitude tracking outer shroud, as initial condition meritorious, reactive power outer shroud, and operational mode is synchronously followed the tracks of to outer shroud by line voltage take over seamlessly to meritorious, reactive power outer shroud; In the synchronizing process of double-fed induction wind driven generator, the final output state Y of line voltage amplitude tracking outer shroud _finalas initial condition X meritorious, reactive power outer shroud _pQinit, as shown in Equation 12:

$X_{\mathrm{PQinit}}=Y_{\mathrm{final}}=\left[\begin{array}{c}{I}_{\mathrm{rd}}\\ I_{\mathrm{rq}}\end{array}\right]=\left[\begin{array}{c}0\\ I_{\mathrm{rq}}^{*}\end{array}\right]$ Formula 12

Thereby avoided in handoff procedure, because the interior circular current of line voltage amplitude tracking outer shroud output causes the rush of current in handoff procedure with reference to the output of set-point and power outer shroud with reference to the difference of set-point; The flexibility that finally realizes double-fed induction wind driven generator is grid-connected.

Adopt after such scheme, the present invention adopts the synchronous tracking strategy of cascade vector control of two outer shrouds, single interior ring; And the smoothness run pattern switchover policy after grid-connected.Two outer shrouds are that line voltage amplitude tracking is controlled outer shroud and electric network voltage phase is followed the tracks of control outer shroud, and two loops have all adopted pure integral controller, have reduced like this concussion in stator voltage synchronizing process; Interior ring is rotor dq current inner loop, has adopted traditional PI adjuster.The output of line voltage amplitude tracking outer shroud is as the reference set-point of interior ring q shaft current, and for controlling the amplitude of exciting current, and rotor d shaft current remains 0 with reference to set-point, guarantees that torque current is 0; The output of electric network voltage phase tracking outer shroud, as initial position angle of rotor signal, adds in the coordinate transform of interior ring feedback signal and output rotor dominant vector, thereby realizes the adjustment of stator voltage phase place.It is the final output state by the line voltage amplitude tracking outer shroud before switching that smoothness run pattern is switched, be that dq shaft current is with reference to set-point, initial value as power outer shroud integrator, to prevent after the incision of power outer shroud, because the difference of reference value causes given step, thereby cause the rush of current in handoff procedure.Whole flexible synchronous network process have been avoided the detection of initial position angle of rotor, have shortened the time of flexible and network process, have improved flexible grid-connected stability, have reduced the impulse current of grid-connected moment.

Control method of the present invention is compared with traditional control method, simple, reliable and stable.On ring controller, adopted pure integral controller outside, simplified the structure of controller, be easy to realize.Realize synchronous grid-connected in, also realized the decoupling zero of rotor current and controlled, the providing convenience property of decoupling zero control model of, reactive power meritorious for switching to after grid-connected.When grid-connected rear pattern is switched, the mode that has adopted state parameter to transmit, has realized taking over seamlessly of power mode.

The inventive method the variable speed constant frequency doubly-fed induction wind driven generator system of grid type, can also be applicable to various three-phase grid inverters, as the parallel network reverse device of solar energy, battery energy storage electricity generation system except being applicable to.It should be noted that, the contents such as the information interaction between said apparatus and intrasystem each unit, implementation, due to the inventive method embodiment based on same design, particular content can, referring to the narration in the inventive method embodiment, repeat no more herein.

One of ordinary skill in the art will appreciate that all or part of step in the whole bag of tricks of above-described embodiment is to come the hardware that instruction is relevant to complete by program, this program can be stored in a computer-readable recording medium, storage medium can comprise: flash memory (Flash Memory), read-only memory (ROM, ReadOnly Memory), random access memory (RAM, Random Access Memory), disk or CD etc.

The double-fed wind power generator the grid-connected control method above embodiment of the present invention being provided, be described in detail, applied specific case herein principle of the present invention and execution mode are set forth, the explanation of above embodiment is just for helping to understand method of the present invention and core concept thereof; , for one of ordinary skill in the art, according to thought of the present invention, all will change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention meanwhile.

Claims (2)

1. double-fed wind power generator grid-connected control method, is characterized in that, comprises step:

A: obtain line voltage u _g , stator three-phase voltage u _s , rotor three-phase electric current i _r and rotor position angle θ _m ;

B: by line voltage u _g , stator three-phase voltage u _s , rotor three-phase electric current i _r transform to respectively synchronous rotating frame;

C: with line voltage u _g with stator three-phase voltage U s with respect to rest frame αthe phase place of axle θ ₁ with phase place θ _s respectively as reference set-point and value of feedback on pure integrator input, using the output of this pure integrator as initial position angle of rotor θ ₀ and with electrical network phase angle θ ₁ and rotor position angle θ _m through adder stack, obtain rotor three-phase electric current i _r be transformed into the coordinate transform phase angle of synchronous rotating frame θ _slip , form electric network voltage phase outer shroud and control;

D: by line voltage daxle component u _gd with stator three-phase voltage daxle component u _sd respectively as reference set-point and the value of feedback of pure integrator input, using the output of this pure integrator as rotor current qthe reference set-point of axle component i ^* _rq , the reference set-point of setting rotor current d axle component i ^* _rd be 0, form line voltage amplitude outer shroud and control; Three phase network voltage, stator voltage, rotor current, by Parker's coordinate transform, are converted under synchronous rotating frame, so have dqaxle line voltage u _gdq , dqaxle stator voltage u _sdq , dqaxle rotor current i _rdq ; By line voltage daxle component u _gd signal is as with reference to set-point, stator three-phase voltage daxle component u _sd signal is as value of feedback, and by pure integral controller, adjuster is exported as rotor current qthe reference set-point of axle component, sets rotor current dthe reference set-point of component is made as 0, and realizes the control to rotor excitation current amplitude by the pi regulator of current inner loop, thereby realizes the synchronous tracking of stator voltage to line voltage amplitude;

E: by rotor current qthe reference set-point of axle component i ^* _rq with rotor current qaxle component value of feedback i _rq through adder, export proportional and integral controller to and obtain rotor voltage qthe set-point of axle component u ^* _rq , by rotor current dthe reference set-point of axle component i ^* _rd with rotor current daxle component value of feedback i _rd through adder, export proportional and integral controller to and obtain rotor voltage dthe set-point of axle component u ^* _rd , form ring in rotor current and control; In this step, interior ring is rotor dqcurrent inner loop, has adopted traditional proportional and integral controller, and the output of line voltage amplitude tracking outer shroud is as interior ring qthe reference set-point of shaft current, for controlling the amplitude of exciting current, and rotor dshaft current remains 0 with reference to set-point, guarantees that torque current is 0; Electric network voltage phase is followed the tracks of the output of outer shroud as initial position angle of rotor signal, one side is as Parker's coordinate transform phase angle of interior circular current feedback signal, on the other hand as anti-Parker's coordinate transform phase angle of interior ring output voltage, thereby realize the adjustment of stator voltage phase place;

F: the amplitude error of judgement stator voltage and line voltage ε _v , phase error ε _θ and whether lasting cycle in setting range, if so, grid-connected contactor close a floodgate realize grid-connected;

Amplitude error in described step F ε _v be less than 10V _, phase error ε _θ be less than 5 °, lasting cycle is greater than 5 weeks.

2. double-fed wind power generator grid-connected control method as claimed in claim 1, is characterized in that, in described step F, grid-connected contactor closes a floodgate to realize and also comprises step after grid-connected:

System is switched to power decoupled control model.