CN102005782A - 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, which comprises the following steps: (1) inputting a difference between an oriented grid voltage and a q-axis component of a stator magnetic flux linkage into a proportional integral (PI) regulator; (2) using the output signal of the PI regulator as a voltage error compensation component, introducing a d-axis no-load exciting current, and using the sum of the d-axis no-load exciting current and the PI regulator output of a voltage difference as a total d-axis no-load exciting current; and (3) substituting the d-axis exciting current and q-axis exciting current into a rotor voltage equation for the no-load grid connection of the double-fed wind-driven generator to obtain on and off control signals of a three-phase power device to regulate an exciting current transformer in order to control the voltage magnitude, frequency and phase of the generator, and thus, realizing the grid connection control of the double-fed wind-driven generator. In the invention, the adopted closed-circuit control mode can eliminate dynamic and static voltage errors in a no-load grid connection process and the phenomenon of low stator voltage control accuracy caused by the reactive power consumption of the double-fed wind-driven generator.

Description

The grid-connected control method of double-fed wind power generator

Technical field

The invention belongs to the control field of being incorporated into the power networks of wind generator system, be meant especially in the double-fed wind-driven power generation system by adding be incorporated into the power networks method that voltage deviation regulates suppress double feed wind power generator and network process in the method for the rush of current that causes.

Background technology

The AC excitation variable speed constant frequency is a widely used class technology in the wind power generation field, it is to carry out AC excitation by the rotor to double-fed asynchronous generator to control the variable speed constant frequency that is implemented in the stator side output current, it can realize the decoupling zero control of power and the tracking Control of maximal wind-energy, and its current transformer has the little advantage of capacity.In the wind-powered electricity generation unit of MW class, common and net mode is to adopt the idle grid connection technology, purpose be to reduce and network process in rush of current, thereby reduce in the wind power-generating grid-connected process impact to electrical network, simultaneously can realize that also system safely and steadily runs more, to the impact shock that reduces motor and prolong aspect such as service life very big benefit is all arranged.Because the double-fed blower fan needs to consume a part of reactive power and sets up magnetic field in the no-load running process, therefore traditional open-loop control method can cause stator voltage control precision deficiency, the direct influence that brings thus be exactly the double-fed blower fan and network process in the impulse current that causes bigger, all be disadvantageous obviously to double-fed blower fan and electric power system.

Double-fed wind power generator is incorporated into the power networks and controls technology such as relating to the parameter of electric machine, current transformer control and rotor position detection, in order to reduce the also impulse current of network process, the present direct idle grid connection method of domestic general employing, be that the power instruction of double-fed blower fan before being incorporated into the power networks is changed to zero, accept the power instruction of blower fan control system after the success of waiting to be incorporated into the power networks again.

Idle grid connection model for the double-fed wind power generator of deriving, we introduce the vector control technology in the Electric Machine Control in the variable-speed constant-frequency wind power generation control system, set up two-phase rotation dq coordinate system, cooperate shown in Figure 1, take stator magnetic linkage oriented in the synchronous rotating frame, in the d axle, the d axle is rotated counterclockwise 90 degree and is the q direction of principal axis with stator magnetic linkage oriented.

In Fig. 1, α ₁, β ₁Be two-phase rest frame, α ₁Axle is a stator A phase winding axis positive direction, α ₂, β ₂For with rotor angular velocity of rotation ω ₂Be the two-phase rotating coordinate system of reference, α ₂Axle is a rotor a phase winding axis positive direction.θ _rBe α ₂Axle and α ₁The angle of axle, its angle is provided by photoelectric encoder.The dq axle is the two-phase synchronous rotating frame, d axle and α ₁The angle of axle is θ _s, its angle is obtained by the phase-locked location of control system software to the line voltage magnetic linkage.Under the motor convention, the rotor voltage equation formula of double-fed asynchronous generator idle grid connection:

$\left\{\begin{array}{c}{u}_{\mathrm{dr}}=R_r{i}_{\mathrm{dr}}+p{L}_r{i}_{\mathrm{dr}}-{\mathrm{\ω}}_{\mathrm{sl}}{L}_r{i}_{\mathrm{qr}}\\ u_{\mathrm{qr}}=R_r{i}_{\mathrm{qr}}+p{L}_r{i}_{\mathrm{qr}}+{\mathrm{\ω}}_{\mathrm{sl}}{L}_r{i}_{\mathrm{dr}}\end{array}\right.$ Formula 1

P wherein _rBe the rotor winding resistance; L _rEquivalent self-induction for dq coordinate system lower rotor part; u _Dr, u _QrDq axle component for rotor voltage; i _Dr, i _QrDq axle component for rotor current; ω _SlBe slip, p is a differential operator.

As can be seen, the key of idle grid connection process is by the control exciter converter, make rotor-exciting voltage satisfy equation 1, and its restriction of current condition is provided by equation 2:

$\left\{\begin{array}{c}{i}_{\mathrm{dr}}=u_{\mathrm{qs}}/{\mathrm{\ω}}_1{L}_M\\ i_{\mathrm{qr}}=0\end{array}\right.$ Formula 2

Wherein, u _QsQ axle component for stator voltage; ω ₁Be the electrical network angular frequency; L _mEquivalent mutual inductance for stator and rotor under the dq coordinate system.And formula 1 is that no any power consumption and the parameter of electric machine are accurately in the motor excitation process, motor rotor position detects under the errorless prerequisite and could satisfy.In fact address before, the reactive power consumption that setting up magnetic field needs will directly cause according to the motor stator voltage of open loop control mode excitation less than normal, thus cause and network process in the significantly mechanical oscillation of impulse current and motor.

Summary of the invention

The technical problem to be solved in the present invention is at defective in the aforementioned background art and deficiency, a kind of grid-connected control method of double-fed wind power generator is provided, its can eliminate in the idle grid connection process dynamically and the quiescent voltage error, the stator voltage control precision that improvement causes because of double-fed wind power generator self reactive power consumption is foot phenomenon not.

The present invention is for solving the problems of the technologies described above, and the technical scheme that is adopted is:

A kind of grid-connected control method of double-fed wind power generator comprises the steps:

(1) gathers stator magnetic linkage oriented d, the q axle component of d, q axle component and the stator voltage of line voltage down respectively, calculate stator voltage u on the q axle _QgWith line voltage u _QsDeviation delta u (t), and it is sent into pi regulator;

(2) with the output signal of pi regulator as the compensation of voltage error component, introduce d axle open-circuit excitation electric current, with d axle open-circuit excitation electric current u _Qs/ ω ₁/ L _MWith the pi regulator output variable sum of voltage deviation as total d axle exciting current, and q axle reference component still is 0;

(3) the rotor voltage equation with aforementioned d, q axle exciting current substitution double-fed wind power generator idle grid connection calculates, obtain the control signal of cut-offfing of three phase power device, regulate voltage magnitude, frequency and the phase place of exciter converter control generator, realize being incorporated into the power networks of double-fed wind power generator controlled.

In the above-mentioned steps (3), rotor voltage equation with aforementioned d, q axle exciting current substitution double-fed wind power generator idle grid connection, utilize space vector modulation method control rotor current transformer, obtain voltage magnitude, frequency and the phase place that control signal is controlled generator of cut-offfing of three phase power device; Gather stator voltage amplitude, frequency and the phase place of generator, and formulate sub-switch with the double-fed wind power generator electrical network that is incorporated into the power networks in the synchronous consistent time control of itself and line voltage.

In the above-mentioned steps (1), gather be incorporated into the power networks point voltage and stator voltage, and under the line voltage flux linkage orientation to amplitude coordinate transforms such as the three-phase voltage of aforementioned collection carry out, obtain line voltage at the component of d, q axle and stator voltage component at d, q axle.

After adopting such scheme, the present invention utilizes the automatic correction principle of regulating based on PI of stator voltage deviation, the deviation of stator voltage and line voltage is compensated component through behind the pi regulator, this compensate component is fed back to control system and the dynamic adjustments excitation current vector, finally realize the synchronous consistent of the stator voltage of double-fed wind power generator and line voltage and then realize soft incision control.

Description of drawings

Fig. 1 is the vector control coordinate transform schematic diagram of double-fed wind power generator;

Fig. 2 is the control schematic diagram that adopts voltage close loop control among the present invention;

Fig. 3 is a flow chart of the present invention.

Embodiment

Below with reference to drawings and the specific embodiments implementation procedure of the present invention and operation principle are elaborated.

Cooperate shown in Figure 3ly, the invention provides a kind of grid-connected control method of double-fed wind power generator, comprise the steps:

(1) gather be incorporated into the power networks point voltage and stator voltage respectively, and under the stator voltage flux linkage orientation to amplitude coordinate transforms such as the three-phase voltage of aforementioned collection carry out, obtain the component u of line voltage at d, q axle _Ds, u _QsWith the component u of stator voltage at d, q axle _Dg, u _Qg

(2) cooperation is shown in Figure 2, calculates stator voltage u under the aforementioned q axle _QgWith line voltage u _QsDeviation delta u (t), and described deviation sent into pi regulator, the Δ i of the output of pi regulator _DrWith the voltage deviation in the compensation open-circuit excitation process, its computing formula is as follows as the compensation rate of d axle exciting current:

$\mathrm{\Δ}{i}_{\mathrm{dr}}\left(t\right)=K_P\mathrm{\Δu}\left(t\right)+\frac{K_P}{\mathrm{\τ}}\∫\mathrm{\Δu}\left(t\right)\mathrm{dt}=K_P\mathrm{\Δu}\left(t\right)+K_i\∫\mathrm{\Δu}\left(t\right)\mathrm{dt}$ Formula 3

K wherein _PBe proportional control factor, K _iBe the integration adjustment factor, τ is the time constant of pi regulator; Following formula is converted into difference equation, obtains the expression formula of digital pi regulator, its k claps and is output as:

$\mathrm{\Δ}{i}_{\mathrm{dr}}\left(k\right)=K_P\mathrm{\Δu}\left(k\right)+K_i{T}_{\mathrm{sample}}\underset{i=1}{\overset{k}{\mathrm{\Σ}}}\mathrm{\Δu}\left(i\right)$ Formula 4

T in the formula 4 _SampleBe the sampling period of digitial controller (DSP),

(3) with the output signal Δ i of pi regulator _DrAs the compensation of voltage error component, introduce unloaded d axle exciting current u _Qs/ ω ₁/ L _M, with sum of the two as total d axle exciting current reference quantity i _{Dr_ref}, and q axle reference component i _{Qr_ref}Still be 0;

(4) with aforementioned d, q axle exciting current substitution rotor voltage equation, utilize space vector modulation method control rotor-exciting current transformer, what obtain three phase power device IGBT cut-offs control signal S _a, S _b, S _c, voltage magnitude, frequency and the phase place of regulating exciter converter control generator;

(5) gather stator voltage amplitude, frequency and the phase place of generator, and formulate sub-switch with the double-fed wind power generator electrical network that is incorporated into the power networks in the synchronous consistent time control of itself and line voltage.

Show according to a large amount of research datas, double-fed wind power generator is in the open-circuit excitation process, need consume certain reactive power for setting up magnetic field, and in the idle grid connection process, the d axle component of reactive power and double-fed wind power generator open-circuit excitation electric current is closely related, therefore adopting under the open loop control mode at present, this part is used to consume idle d axle Control current can not be used to set up enough stator voltages.Just be based on aforementioned consideration, the present invention utilizes pi regulator to control this voltage deviation, and the adjusting output of PI controller is introduced exciting current as extra compensate component.By introducing the ERROR CONTROL compensation mechanism, can effectively improve not foot phenomenon of the stator voltage control precision that in the idle grid connection process, causes because of double-fed wind power generator self reactive power consumption.

Claims (3)

1. the grid-connected control method of a double-fed wind power generator is characterized in that: comprise the steps:

(1) gathers stator magnetic linkage oriented d, the q axle component of d, q axle component and the stator voltage of line voltage down respectively, calculate stator voltage u on the q axle _QgWith line voltage u _QsDeviation delta u (t), and it is sent into pi regulator;

(2) with the output signal of pi regulator as the compensation of voltage error component, introduce d axle open-circuit excitation electric current, with d axle open-circuit excitation electric current u _Qs/ ω ₁L _MWith the pi regulator output variable sum of voltage deviation as total d axle exciting current, and q axle reference component still is 0;

(3) the rotor voltage equation with aforementioned d, q axle exciting current substitution double-fed wind power generator idle grid connection calculates, obtain the control signal of cut-offfing of three phase power device, regulate voltage magnitude, frequency and the phase place of exciter converter control generator, realize being incorporated into the power networks of double-fed wind power generator controlled.

2. the grid-connected control method of a kind of double-fed wind power generator as claimed in claim 1, it is characterized in that: in the described step (3), rotor voltage equation with aforementioned d, q axle exciting current substitution double-fed wind power generator idle grid connection, utilize space vector modulation method control rotor current transformer, obtain voltage magnitude, frequency and the phase place that control signal is controlled generator of cut-offfing of three phase power device; Gather stator voltage amplitude, frequency and the phase place of generator, and formulate sub-switch with the double-fed wind power generator electrical network that is incorporated into the power networks in the synchronous consistent time control of itself and line voltage.

3. the grid-connected control method of a kind of double-fed wind power generator as claimed in claim 2, it is characterized in that: in the described step (1), collection be incorporated into the power networks point voltage and stator voltage, and under the line voltage flux linkage orientation, the three-phase voltage of aforementioned collection such as is carried out at the amplitude coordinate transform, obtain line voltage at the component of d, q axle and stator voltage component at d, q axle.

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