CN105024607B - Matrix converter excitation-based DFIG control method under unbalanced network voltage - Google Patents

Abstract

The invention discloses a matrix converter excitation-based DFIG control method under unbalanced network voltage. The method can effectively realize four control objectives of stator current balance, rotor current balance, stator power stabilization and DFIG electromagnetic torque stabilization, has no positive and negative sequence separation link in a control loop, reduces the problems of time delay, a phase angle and a detection error of an amplitude value brought by a positive and negative sequence separation process, is simple and convenient to calculate, has good dynamic characteristics, and can realize rapid and precise control. The matrix converter excitation-based DFIG control method under unbalanced network voltage further verifies feasibility and scientificity of application of a matrix converter to double-fed wind power generation technology, enables a matrix converter excitation-based DFIG system to realize a good operation effect both in an ideal power grid and under unbalance network voltage, and has very good research value and practical value.

Description

DFIG control methods based on matrix converter excitation under a kind of unbalanced electric grid voltage

Technical field

The invention belongs to wind-power electricity generation control technology field, and in particular to become based on matrix under a kind of unbalanced electric grid voltage The DFIG control methods of parallel operation excitation.

Background technology

With the increase of fossil energy usage quantity, the energy is to human economy, the restriction of social development and to resource environment Influence it is also more and more significant, therefore the mankind increasingly pay attention to the utilization of regenerative resource, wind energy as in regenerative resource most Inexpensively, most potential " green energy resource ", has obtained exploitation and development energetically.At present, dual-feed asynchronous wind power generator (DFIG) because its Converter Capacity is small, power independence uneoupled control, the more low advantage of cost, as wide variety of both at home and abroad Wind driven generators.The key component that its system is constituted is pwm converter, but the double pwm converters of existing frequently-used voltage-source type are deposited Volume is big, weight weight, and not easy care the problems such as, matrix converter is a kind of new converter of green, therefore with square Battle array converter has good researching value as the DFIG control strategies research of pwm converter.

Current most of DFIG wind generation set control strategies connect primarily directed to grid voltage amplitude and frequency-invariant, phase Continuous preferable power network condition design, but actual electric network is often and non-ideal, electric network fault through being commonly present, especially actual power train Unbalanced fault in system can cause the imbalance of stator and rotor electric current height, and stator and rotor winding produces uneven heating, electromagnetism Torque produces pulsation, and the power for transferring to power network vibrates.Therefore, for the AC excitation in the case of unbalanced source voltage Control strategy turns into recent domestic study hotspot, but current achievement in research is mainly based upon double-PWM frequency converter excitation system Control strategy under system, because matrix converter does not have intermediate energy storage link, imbalance, the large disturbances of line voltage etc. improper Operating mode can all directly influence exciting current, exacerbate control difficulty, it is therefore desirable to study base under the conditions of unbalanced electric grid voltage In the DFIG control strategies of matrix converter excitation.

Li Hui exists《Double feed wind power generator based on matrix converter excitation be incorporated into the power networks control strategy research, it is Central-South University Ph.D. dissertation, 2011》A kind of middle general principle according to asymmetrical component method, it is proposed that matrix under the conditions of Voltage unbalance Converter Excitation Control Strategy, the strategy controls rotor current and matrix converter to be input into respectively using double synchronous rotating frames Electric current, wherein:The positive sequence vector of rotor current is used to realize power decoupled control, and the negative phase-sequence vector of rotor current is then used in fact Now eliminate stator negative-sequence current, reduce the control targe, the input current of matrix converter such as active power or reactive power pulsation Negative phase-sequence vector is used to reduce the degree of unbalancedness of input voltage, so as to reduce the harmonic wave of matrix converter output current.However, the control Need to carry out the electromagnetic quantities such as rotor current positive sequence, negative phase-sequence separation in the control ring of method processed, this separation process can introduce time delay And the error of phase angle and amplitude, the dynamic property of electric current loop is have impact on, it is analyzed from last simulation result, the control strategy Influence for unbalanced electric grid voltage to DFIG units has improvement result, but control performance is not very good.Meanwhile, should Control method needs to carry out very big change to the conventional vector Control system architecture designed under equilibrium condition, limits the control The prospects for commercial application of method.

The content of the invention

For the above-mentioned technical problem existing for prior art, the invention provides being based under a kind of unbalanced electric grid voltage The DFIG control methods of matrix converter excitation, do not have positive-negative sequence to separate link in its control ring, can realize quickly and accurately Control, while the proportion integral modulus of current controller can directly using the design ginseng of pi regulator under the conditions of conventional balanced Number, with stronger adaptability.

The DFIG control methods based on matrix converter excitation, comprise the following steps under a kind of unbalanced electric grid voltage：

(1) the threephase stator voltage U of DFIG is gathered first_sabc, threephase stator electric current I_sabc, three-phase rotor current I_rabc, turn Fast ω_rAnd rotor position angle θ_r；Then to threephase stator electric current I_sabcWith three-phase rotor current I_rabcPark changes are carried out respectively Change, correspondence obtains the stator current vector I under d-q rotating coordinate systems_sdqWith rotor current vector I_rdq；And then to threephase stator electricity Pressure U_sabcDq conversion is carried out, the stator voltage vector comprising positive-negative sequence vector under positive synchronous speed coordinate system is obtainedAnd it is anti- To the stator voltage vector comprising positive-negative sequence vector under synchronous speed coordinate systemFinally stator voltage arrow is extracted using trapper AmountPositive sequence vectorExtract stator voltage vectorNegative phase-sequence vector

(2) according to different control targes and positive sequence vectorWith negative phase-sequence vectorCalculate rotor current The given vector of positive sequenceVector is given with negative phase-sequenceAnd then it is calculated the given vector I of rotor current_rdq ^*；

(3) the given vector I of described rotor current is made_rdq ^*Subtract rotor current vector I_rdq, obtain rotor current error arrow Amount Δ I_rdq；Then to described rotor current error vector Δ I_rdqCarry out PIR (proportional, integral-resonance) regulations and decoupling is mended Repay, obtain the given vector U of rotor voltage of DFIG_rdq ^*, and then vector U given to rotor voltage_rdq ^*Park inverse transformations are carried out, is obtained To three-phase rotor voltage Setting signal U_rabc ^*；

(4) to stator voltage vectorPositive sequence vectorPark inverse transformations are carried out, threephase stator positive sequence is obtained Voltage signal

(5) described three-phase rotor voltage Setting signal U is made_rabc ^*Referred to as the output line voltage of matrix converter, made Described threephase stator positive sequence voltage signalAs the input phase-current reference of matrix converter, and then using indirectly SVPWM (space vector pulse width modulation) modulation method is modulated, and obtains one group of pwm signal and is used to in DFIG matrix converters Device for power switching is controlled.

The expression formula of transmission function F (s) of trapper is as follows in described step (1)：

Wherein：ω₀=2 π * 100rad/s, ζ are attenuation coefficient, and s is Laplace operator.

In described step (2), if control targe is that stator active power is constant, rotor electricity is calculated by below equation The given vector of the positive sequence of streamVector is given with negative phase-sequence

If control targe is rotor current sinusoidal without harmonic wave, the given arrow of positive sequence for calculating rotor current by below equation AmountVector is given with negative phase-sequence

If control targe is balanced for stator current, the given vector of positive sequence that rotor current is calculated by below equationVector is given with negative phase-sequence

If control targe is steady electromagnetic torque, the given vector of positive sequence that rotor current is calculated by below equationVector is given with negative phase-sequence

Wherein： It is positive sequence vectorD axle components,WithRespectively negative phase-sequence vectorD axles component and q axle components,WithRespectively positive sequence gives vectorD axles component and q axle components,WithRespectively negative phase-sequence gives vectorD axles component and q axles point Amount, L_sIt is the stator leakage inductance of DFIG, L_mIt is the rotor mutual inductance of DFIG, ω is threephase stator voltage U_sabcAngular frequency,WithRespectively stator active power set-point and stator reactive power set-point.

The given vector I of rotor current is calculated by below equation in described step (2)_rdq ^*：

Wherein：J is imaginary unit, and θ is threephase stator voltage U_sabcPhase.

By below equation to rotor current error vector Δ I in described step (3)_rdqCarry out PIR regulations and decoupling is mended Repay：

Wherein：G_PIRS () is the transmission function of PIR regulations, L_rAnd L_sThe respectively rotor leakage inductance of DFIG and stator leakage inductance, L_m It is the rotor mutual inductance of DFIG, σ is the magnetic leakage factor of DFIG, ψ_sdqIt is the stator magnetic linkage vector and ψ of DFIG_sdq=L_mI_rdq+ L_sI_sdq；R_rAnd R_sThe respectively rotor resistance of DFIG and stator resistance, j is imaginary unit, ω_slipIt is the slippage angular frequency of DFIG And ω_slip=ω-ω_r, ω is threephase stator voltage U_sabcAngular frequency.

The transmission function G of the PIR regulations_PIRS the expression formula of () is as follows：

Wherein：K_P、K_IAnd K_RProportionality coefficient, integral coefficient and the resonance coefficient for respectively giving, ω₀=2 π * 100rad/ S, ω_cIt is the cut-off frequency for giving, s is Laplace operator.

It is steady that DFIG control methods of the present invention can effectively realize stator current balance, rotor current balance, stator power Fixed and DFIG electromagnetic torques stablize four control targes, and do not have positive-negative sequence to separate link in control ring, reduce positive and negative sequence The problems such as detection error of time delay, phase angle and amplitude that separation process is brought, calculate easy, with good dynamic characteristic, Can realize quickly and accurately controlling.The present invention further demonstrates matrix converter and is used in double-fed wind generating skill simultaneously Feasibility and science in art so that the DFIG systems based on matrix converter excitation are in preferable power network and unbalanced power grid electricity Good operational effect is capable of achieving in pressure, with good researching value and practical value.

Brief description of the drawings

Fig. 1 is the principle process schematic diagram of DFIG control methods of the present invention.

When Fig. 2 is unbalanced source voltage degree δ=7% using control method of the present invention under the switching of different control targes The static Simulation waveform diagram of DFIG.

Fig. 3 is that when the instantaneous imbalance fault of power network occurs, the simulation waveform of DFIG is illustrated using after control method of the present invention Figure.

Specific embodiment

In order to more specifically describe the present invention, below in conjunction with the accompanying drawings and specific embodiment is to technical scheme It is described in detail.

Present embodiment by a capacity be 3MW, rated voltage for the commercial DFIG of 690V as a example by.As shown in figure 1, this hair The proportional integral resonance control method of the DFIG based on matrix converter excitation, specific steps under the conditions of bright unbalanced electric grid voltage It is as follows：

(1) the threephase stator electric current I of DFIG is gathered respectively using two groups of current Hall sensors 2_sabcWith three-phase rotor electricity Stream I_rabc, while gathering the threephase stator voltage U of DFIG using voltage hall sensor 3_sabc；Use enhanced phase-locked loop module 7 Detect the angular frequency of threephase stator voltage positive-sequence component₁And phase theta₁；The rotating speed of DFIG is detected using position sensor 5 ω_rAnd rotor position angle θ_r, it can thus be concluded that rotating forward slippage angular frequency_slip=ω₁-ω_r,；

Definition herein rotates forward synchronous speed ω₁Rotation dq⁺Coordinate system is with angular speed w¹Rotate counterclockwise, and reversal synchronization it is fast- ω₁Rotation dq^-Coordinate system is with angular velocity omega₁Turn clockwise, subscript "+" and "-" are expressed as positive and negative sequence component, subscript "+", "-" is expressed as forward and backward synchronous speed rotating coordinate system.

Using Clark conversion modules 6 and stator Park conversion modules 10 according to phase theta=θ₁To threephase stator electric current I_sabc Coordinate transform is carried out, the dq axle components I of threephase stator electric current is obtained⁺ _sdq, converted using Clark conversion modules 6 and rotor Park Module 8 is according to phase theta=θ₁-θ_rTo three-phase rotor current I_rabcCoordinate transform is carried out, the dq axle components of three-phase rotor current are obtained I⁺ _rdq。

The expression formula such as following formula of Clark conversion：

The expression formula such as following formula of Park conversion：

Then the dq axle components of stator magnetic linkage and rotor flux are tried to achieve according to following formula.

Using Clark conversion modules 6 according to phase theta₁To threephase stator voltage U_sabcCarry out coordinate transform and obtain U_sαβ, According to phase theta in Park conversion modules 10₁With phase-θ₁To U_sαβForward and backward synchronous speed rotating coordinate transformation is carried out respectively, then is passed through Cross trapper 11 and filter 2 harmonics respectively, extract positive and negative sequence component, i.e. U⁺ _sdq+、U^- _sdq-。

The continuous domain expression formula such as following formula of trapper：

Wherein, ω₀=2 ω₁=200 π rad/s, ζ are attenuation coefficient, in real system, it is contemplated that filter effect and control The stability of a system, takes ζ=0.707.

(2) using rotor current set-point generation module 12, according to different control targes, respective objects are obtained corresponding Rotor current set-point, rotor current set-point 12 Computing Principles of generation module are as follows：

DFIG stators active power under the conditions of unbalanced source voltage can be expressed as follows formula：

Wherein：P_s0, P_ssin2And P_scos2Respectively direct current (average) component, two frequencys multiplication of stator active power of output just, it is remaining String wave component, is expressed as matrix form such as following formula：

Wherein, L_mIt is the rotor mutual inductance of DFIG, L_sIt is the stator leakage inductance of DFIG, L_rIt is the rotor leakage inductance of DFIG.

Electromagnetic power and Formula of Electromagnetic such as following formula：

Wherein, Ω_r=ω_r/n_pIt is synchronization mechanism angular speed, n_pIt is number of pole-pairs.

According to the different corresponding relational expressions of control targe, above formula is substituted into respectively can obtain corresponding control targe lower rotor part electricity Flow positive and negative sequence reference value i⁺ _rdq+ ^*、i^- _rdq- ^*, in calculating process, make use of positive sequence stator voltage vector oriented control thought to enter Simplification is gone：

Target 1：Constant stator active power, that is, eliminate two times of mains frequency components of stator active power, then P_ssin2 =P_scos2=0, calculate：

Wherein：

Target 2：DFIG rotor currents are sinusoidal to be free of negative sequence component without harmonic wave, i.e. rotor current, then i^- _rd- ^*=i^- _rq- ^*=0, Calculate：

Target 3：Stator current is balanced, i.e., stator current is free of negative sequence component, thenCalculate：

Target 4：Stable electromagnetic torque, that is, eliminate two harmonics of torque, then P_esin2=P_ecos2=0, calculate：

Therefore further, according to the following formula by the positive and negative sequence reference value i of rotor current⁺ _rdq+ ^*、i^- _rdq- ^*Transform to rotating forward synchronous In fast rotating coordinate system, as the given value of current value i of PIR adjusters⁺ _rdq ^*。

(3) using PIR regulations and decoupling compensation module 13, PIR regulations and solution are carried out to three-phase rotor current according to following formula Coupling is compensated, and thus can obtain the dq axle components of rotor voltage set-point

Wherein,Wherein ω_cIt is cut-off frequency, introduces the ω of attenuation term 2_cS, Reduce sensitivity of the controller to frequency departure, cut-off frequency ω_c5~15rad/s of span；K_p、K_iAnd K_RRespectively Proportionality coefficient, integral coefficient and resonance coefficient；R_rIt is rotor resistance, L_sIt is the stator leakage inductance of DFIG, L_rFor the rotor of DFIG leaks Sense, ω_rIt is DFIG rotating speeds, ω_slip+To rotate forward slippage angular frequency, σ=1-L² _m/(L_sL_r) it is magnetic leakage factor, s is calculated for Laplce Son.In the present embodiment, ω_c=5rad/s, K_p=2.5, K_i=2, K_R=150.

Recycle rotor Park inverse transform blocks 14 and Clark inverse transform blocks 15 and according to phase theta=θ₁-θ_rTo rotor The dq axle components of voltage set-pointCoordinate transform is done, three-phase rotor voltage Setting signal U is obtained⁺ _rabc ^*, in this, as square The output line voltage vector reference of the battle array indirect means of space vector representation of converter.

(4) it is 1 to ensure matrix converter input side power factor, that is, requires input voltage and current in phase position, because This is using stator Park inverse transform blocks 16 and Clark inverse transform blocks 15 and according to phase theta₁By stator positive sequence voltage dq axles point Amount U⁺ _sdq+In transforming to three-phase static coordinate system, so as to obtain U⁺ _sabc+(power network positive sequence voltage) is indirectly empty as matrix converter Between vector method input phase current vector reference.

(5) the output line voltage vector according to obtained by step (3) and step (4) is joined with reference to method input phase current vector Examine, be modulated using indirect means of space vector representation, so as to obtain one group of PWM modulation signal S_1~99 to matrix converter 4 are double It is controlled to switch, so as to realize the control to DFIG.

Simulation analysis are carried out to present embodiment below, wherein DFIG parameters are as follows：Power network phase voltage amplitude is 690V, electricity Net rated frequency f=50Hz, double feedback electric engine rated power is 3MW, and number of pole-pairs is 3, stator resistance R_s=0.0586, rotor resistance R_r=0.00422, stator leakage inductance L_s=0.130, rotor leakage inductance L_r=0.127, mutual inductance L_m=3.78.Simulated conditions are transported for DFIG Row is in the metasynchronism state of 0.8 rotating speed, and stator is active to be given as 0.8, idle to be given as 0.(this emulation is perunit using parameter Value)

DFIG when Fig. 2 is unbalanced source voltage degree δ=7% using the inventive method under the switching of different control targes Static Simulation waveform, wherein starting in 0.8s with control method of the invention, chosen not in the different time periods successively Same control targe (0.8~1s：Control targe 1；1~1.2s：Control targe 2；1.2~1.4s：Control targe 3；1.4~ 1.6s：Control targe 4).By be can be seen that in figure, when not taking corresponding control strategy, the stator current and rotor current of DFIG are deposited In very big degree of unbalancedness, there is substantially vibration in stator active power and reactive power and electromagnetic torque.Control strategy is made With rear, DFIG reaches the control effect required by four control targes successively, i.e., successfully eliminate unbalanced source voltage and bring Influence, eliminated respectively in different time sections stator active power fluctuation, realize rotor current sine without harmonic wave, stator Two times of mains frequencies that current unbalance factor is down to 0.05% by 14%, eliminate electromagnetic torque are pulsed.So far, present embodiment Correctness and validity be verified.

Fig. 3 is DFIG in the emulation knot after using control strategy of the invention when the instantaneous imbalance fault of power network occurs Really.In this emulation, it is control targe (control targe 1) that selection eliminates stator active power fluctuation, and line voltage is in 0.4s Generation unbalanced fault, unbalanced source voltage degree is δ=7%.From the figure 3, it may be seen that when in failure generation moment, the stator of DFIG Active power fluctuation is suppressed, and the influence that unbalanced electric grid voltage is caused is eliminated immediately, further demonstrates this implementation The validity of mode.

In sum, the proportional integral of the DFIG of matrix converter excitation is based under the conditions of unbalanced electric grid voltage of the present invention Resonance control method, can effectively realize stator current balance, rotor current balance, stator power stabilization and DFIG electromagnetic torques Stablize four control targes, and there is no positive-negative sequence to separate link in control ring, reduce what positive and negative sequence separation process was brought The problems such as detection error of time delay, phase angle and amplitude, so as to improve the dynamic characteristic of control；Its proportion integral modulus can simultaneously So that directly using the design parameter of pi regulator under the conditions of conventional balanced, the method has stronger adaptability, will not be to DFIG The steady-state operation of unit and transient operation are impacted.

Claims (6)

1. the DFIG control methods based on matrix converter excitation under a kind of unbalanced electric grid voltage, comprise the following steps：

(1) the threephase stator voltage U of DFIG is gathered first_sabc, threephase stator electric current I_sabc, three-phase rotor current I_rabc, rotational speed omega_r And rotor position angle θ_r；Then to threephase stator electric current I_sabcWith three-phase rotor current I_rabcCoordinate transform is carried out respectively, correspondence Obtain the stator current vector I under d-q rotating coordinate systems_sdqWith rotor current vector I_rdq；And then to threephase stator voltage U_sabc Coordinate transform is carried out, the stator voltage vector comprising positive-negative sequence vector under positive synchronous speed coordinate system is obtainedAnd it is reversely same Stator voltage vector comprising positive-negative sequence vector under leg speed coordinate systemFinally stator voltage vector is extracted using trapperPositive sequence vectorExtract stator voltage vectorNegative phase-sequence vector

(2) according to different control targes and positive sequence vectorWith negative phase-sequence vectorCalculate rotor current just Sequence gives vectorVector is given with negative phase-sequenceAnd then it is calculated the given vector I of rotor current_rdq ^*；

(3) the given vector I of described rotor current is made_rdq ^*Subtract rotor current vector I_rdq, obtain rotor current error vector Δ I_rdq；Then to described rotor current error vector Δ I_rdqPIR regulations and decoupling compensation are carried out, the rotor voltage of DFIG is obtained Given vector U_rdq ^*, and then vector U given to rotor voltage_rdq ^*Coordinate transform is carried out, three-phase rotor voltage Setting signal is obtained U_rabc ^*；

(4) to stator voltage vectorPositive sequence vectorCoordinate transform is carried out, threephase stator positive sequence voltage signal is obtained

(5) described three-phase rotor voltage Setting signal U is made_rabc ^*Referred to as the output line voltage of matrix converter, made described Threephase stator positive sequence voltage signalAs the input phase-current reference of matrix converter, and then using indirectly SVPWM modulation methods are modulated, and obtain one group of pwm signal and are used to control the device for power switching in DFIG matrix converters System.

2. DFIG control methods according to claim 1, it is characterised in that：The transmission of trapper in described step (1) The expression formula of function F (s) is as follows：

$F\left(s\right)=\frac{s^2+{\mathrm{\ω}}_0^2}{s^2+2{\mathrm{\ζ\ω}}_{0}s+{\mathrm{\ω}}_0^2}$

Wherein：ω₀=2 π * 100rad/s, ζ are attenuation coefficient, and s is Laplace operator.

3. DFIG control methods according to claim 1, it is characterised in that：In described step (2), if control targe is Stator active power is constant, then the given vector of positive sequence for calculating rotor current by below equationVector is given with negative phase-sequence

$\left\{\begin{array}{c}{I_{rd+}^{+}}^{*}=\frac{L_s{U}_{sd+}^{+}}{L_m}-\frac{4U_{sd+}^{+}{U}_{sd-}^{-}{U}_{sq-}^{-}}{{\mathrm{\ωL}}_m{D}_4}\\ {I_{rq+}^{+}}^{*}=\frac{L_s{U}_{sd+}^{+}\left(Q_s^{*}+\frac{D_4}{{\mathrm{\ωL}}_s}\right)}{L_m{D}_3}-\frac{2U_{sd+}^{+}}{{\mathrm{\ωL}}_m{D}_3}\left({U_{sd-}^{-}}^2-{U_{sq-}^{-}}^2\right)\\ {I_{rd-}^{-}}^{*}=-\frac{2U_{sq-}^{-}}{{\mathrm{\ωL}}_m}-D_1{I_{rd+}^{+}}^{*}-D_2{I_{rq+}^{+}}^{*}\\ {I_{rq-}^{-}}^{*}=-\frac{2U_{sd-}^{-}}{{\mathrm{\ωL}}_m}-D_2{I_{rd+}^{+}}^{*}+D_1{I_{rq+}^{+}}^{*}\end{array}\right.$

If control targe is rotor current sinusoidal without harmonic wave, the given vector of positive sequence for calculating rotor current by below equationVector is given with negative phase-sequence

$\left\{\begin{array}{c}{I_{rd+}^{+}}^{*}=\frac{L_s{P}_s^{*}}{L_m{U}_{sd+}^{+}}\\ {I_{rq+}^{+}}^{*}=-\frac{L_s\left(Q_s^{*}+\frac{D_4}{{\mathrm{\ωL}}_s}\right)}{L_m{U}_{sd+}^{+}}\\ {I_{rd-}^{-}}^{*}=0\\ {I_{rq-}^{-}}^{*}=0\end{array}\right.$

If control targe is balanced for stator current, the given vector of positive sequence that rotor current is calculated by below equationWith Negative phase-sequence gives vector

$\left\{\begin{array}{c}{I_{rd+}^{+}}^{*}=\frac{L_s{P}_s^{*}}{L_m{U}_{sd+}^{+}}\\ {I_{rq+}^{+}}^{*}=-\frac{L_s\left(Q_s^{*}+\frac{D_4}{{\mathrm{\ωL}}_s}\right)}{L_m{U}_{sd+}^{+}}\\ {I_{rd-}^{-}}^{*}=-\frac{U_{sq-}^{-}}{{\mathrm{\ωL}}_m}\\ {I_{rq-}^{-}}^{*}=-\frac{U_{sd-}^{-}}{{\mathrm{\ωL}}_m}\end{array}\right.$

If control targe is steady electromagnetic torque, the given vector of positive sequence that rotor current is calculated by below equationWith Negative phase-sequence gives vector

$\left\{\begin{array}{c}{I_{rd+}^{+}}^{*}=\frac{L_s{P}_s^{*}}{L_m{U}_{sd+}^{+}}\\ {I_{rq+}^{+}}^{*}=-\frac{L_s\left(Q_s^{*}+\frac{D_4}{{\mathrm{\ωL}}_s}\right)}{L_m{U}_{sd+}^{+}}\\ {I_{rd-}^{-}}^{*}=D_1{I_{rd+}^{+}}^{*}+D_2{I_{rq+}^{+}}^{*}\\ {I_{rq-}^{-}}^{*}=D_2{I_{rd+}^{+}}^{*}-D_1{I_{rq+}^{+}}^{*}\end{array}\right.$

Wherein： It is positive sequence vectorD axle components,With Respectively negative phase-sequence vectorD axles component and q axle components,WithRespectively positive sequence gives vectorD axles Component and q axle components,WithRespectively negative phase-sequence gives vectorD axles component and q axle components, L_sIt is DFIG Stator leakage inductance, L_mIt is the rotor mutual inductance of DFIG, ω is threephase stator voltage U_sabcAngular frequency,WithRespectively stator Active power set-point and stator reactive power set-point.

4. DFIG control methods according to claim 1, it is characterised in that：Pass through below equation in described step (2) Calculate the given vector I of rotor current_rdq ^*：

${I_{rdq}}^{*}={I_{rdq+}^{+}}^{*}+{I_{rdq-}^{-}}^{*}{e}^{-j2\mathrm{\θ}}$

Wherein：J is imaginary unit, and θ is threephase stator voltage U_sabcPhase.

5. DFIG control methods according to claim 1, it is characterised in that：Pass through below equation in described step (3) To rotor current error vector Δ I_rdqCarry out PIR regulations and decoupling compensation：

$U_{rdq}^{*}=G_{PIR}\left(s\right){\mathrm{\ΔI}}_{rdq}+\left({\mathrm{j\ω}}_{slip}{\mathrm{\σL}}_r+R_r\right)I_{rdq}+\frac{L_m}{L_s}\left(U_{sdq}^{+}-R_s{I}_{sdq}-{\mathrm{j\ω}}_r{\mathrm{\ψ}}_{sdq}\right)$

Wherein：G_PIRS () is the transmission function of PIR regulations, L_rAnd L_sThe respectively rotor leakage inductance of DFIG and stator leakage inductance, L_mFor The rotor mutual inductance of DFIG, σ is the magnetic leakage factor of DFIG, ψ_sdqIt is the stator magnetic linkage vector and ψ of DFIG_sdq=L_mI_rdq+L_sI_sdq； R_rAnd R_sThe respectively rotor resistance of DFIG and stator resistance, j is imaginary unit, ω_slipFor DFIG slippage angular frequency and ω_slip=ω-ω_r, ω is threephase stator voltage U_sabcAngular frequency.

6. DFIG control methods according to claim 5, it is characterised in that：The transmission function G of the PIR regulations_PIR(s) Expression formula it is as follows：

$G_{PIR}\left(s\right)=K_P+\frac{K_I}{s}+K_R\frac{2{\mathrm{\ω}}_{c}s}{s^2+2{\mathrm{\ω}}_{c}s+{\mathrm{\ω}}_0^2}$

Wherein：K_P、K_IAnd K_RProportionality coefficient, integral coefficient and the resonance coefficient for respectively giving, ω₀=2 π * 100rad/s, ω_c It is the cut-off frequency for giving, s is Laplace operator.