CN102694394A - Method and system for controlling current of grid-side converter of wind driven generator under unbalanced power grid condition - Google Patents

Abstract

Disclosed are a method and a system for controlling current of a grid-side converter of a doubly-fed wind driven generator under an unbalanced power grid condition. The method includes combining voltage of a power grid, alternating-current-side voltage of the grid-side converter and delay signals of the power grid and the grid-side converter with given active power and given reactive power, and analyzing and computing to obtain an instruction value of alternating-current-side current of the converter; and further computing to obtain alternating-current-side instruction voltage of the grid-side converter according to a mathematic module of the grid-side converter and a principle that an actual current value of a next time interval is equal to the instruction value, and then generating a pulse signal for controlling on and off of a switching tube via SVPWM (space vector pulse width modulation). In the method, rotational coordinate transformation and positive and negative sequence decomposition are not required, grid-side current and inductance parameters are either not required, fluctuation of direct-current-side voltage of the grid-side converter can be suppressed under an unbalanced voltage condition of the power grid, grid-side harmonic current is reduced, and unity power factor is maintained.

Description

Wind-driven generator net side converter current control method and system during unbalanced power supply

Technical field

The present invention relates to the control method and the system of double-fed wind power generator net side converter, the current control method and the system of double-fed wind power generator net side converter belong to technical field of wind power generation when relating in particular to unbalanced power supply.

Background technology

Wind energy is the reliable energy of cleaning, and can Fast Installation, and it has become regenerative resource with fastest developing speed all over the world.In all kinds of wind power generation, dual-feed asynchronous wind power generator since its can variable speed constant frequency operation, meritorious and idle control flexibly, advantage such as current transformer power is less relatively, all the fashion on wind-power market.Double-fed asynchronous generator is connected with electrical network through a back-to-back current transformer; Wherein the pusher side current transformer is that double-fed generator provides field power supply; Torque component and excitation component through controlling rotor current are realized meritorious flexibly and idle control, and the net side converter then mainly is to be used for keeping the constant and assurance net side unity power factor of DC bus-bar voltage.Net side converter in the past and adopt the directed two closed-loop vector controls of line voltage, under desirable electrical network condition, can obtain the better controlling performance.Because actual electric network is normally unbalanced, if control strategy is not added change, then can on DC bus-bar voltage, produce the fluctuation of two frequencys multiplication, make current on line side produce distortion.Along with the raising of wind power-generating grid-connected scale, also increasingly high to the requirement of wind generator reliability.This just requires to design the control method that unbalanced source voltage is had adaptive ability, to suppress the dc voltage fluctuation and to reduce side harmonics.

Summary of the invention

The current control method and the system of dual-feed asynchronous wind power generator net side converter when the present invention proposes a kind of unbalanced power supply.It is constant that this method and system can effectively suppress the current on line side harmonic wave and keep VD.Technical scheme of the present invention is following:

The current control method of dual-feed asynchronous wind power generator net side converter during a kind of unbalanced power supply comprises following steps:

Steps A: according to the line voltage e on the two phase static coordinate _α, e _βWith net side converter AC side voltage u _α, u _βAnd their inhibit signal e ' _α, e ' _β, u ' _α, u ' _β, in conjunction with meritorious and the given P of reactive power ^Ref, Q ^Ref, analytical Calculation obtains the command value of AC side of converter electric current With

$\left[\begin{array}{c}{i}_{\mathrm{\α}}^{\mathrm{Ref}}\\ i_{\mathrm{\β}}^{\mathrm{Ref}}\end{array}\right]=\frac{{4P}^{\mathrm{Ref}}}{3\mathrm{\Δ}}\left[\begin{array}{c}{e}_{\mathrm{\β}}^{\′}(u_{\mathrm{\β}}^2+{u_{\mathrm{\β}}^{\′}}^2)+e_{\mathrm{\α}}(u_{\mathrm{\α}}{u}_{\mathrm{\β}}^{\′}-u_{\mathrm{\β}}{u}_{\mathrm{\α}}^{\′})+e_{\mathrm{\α}}^{\′}(u_{\mathrm{\α}}{u}_{\mathrm{\β}}+u_{\mathrm{\α}}^{\′}+u_{\mathrm{\β}}^{\′})\\ -e_{\mathrm{\α}}^{\′}(u_{\mathrm{\α}}^2+{u_{\mathrm{\α}}^{\′}}^2)+e_{\mathrm{\β}}(u_{\mathrm{\α}}{u}_{\mathrm{\β}}^{\′}-u_{\mathrm{\β}}{u}_{\mathrm{\α}}^{\′})-e_{\mathrm{\β}}^{\′}(u_{\mathrm{\α}}{u}_{\mathrm{\β}}+u_{\mathrm{\α}}^{\′}{u}_{\mathrm{\β}}^{\′})\end{array}\right],$

Wherein $\mathrm{\Δ}=({\mathrm{\μ}}_{\mathrm{\α}}{u}_{\mathrm{\β}}^{\′}-u_{\mathrm{\β}}{u}_{\mathrm{\α}}^{\′})(e_{\mathrm{\α}}^2+e_{\mathrm{\β}}^2+{e_{\mathrm{\α}}^{\′}}^2+{e_{\mathrm{\β}}^{\′}}^2)+(e_{\mathrm{\α}}{e}_{\mathrm{\β}}^{\′}-e_{\mathrm{\β}}{e}_{\mathrm{\α}}^{\′})(u_{\mathrm{\α}}^2+u_{\mathrm{\β}}^2+{u_{\mathrm{\α}}^{\′}}^2+{u_{\mathrm{\β}}^{\′}}^2);$

Step B: according to the command value of ac-side current and the Mathematical Modeling of net side converter, calculate the AC side command voltage of net side converter, produce the pulse signal of control switch pipe conducting then through SVPWM.

It specifically can be:

Step 1: grid side voltage obtains the voltage signal e on static two phase α β coordinates through 3/2 conversion _α, e _βThe AC side voltage of net side converter directly obtains being u from the voltage instruction of input SVPWM _α, u _βe _α, e _βAnd u _α, u _βObtain e ' through 1/4 cycle delay function _α, e ' _βAnd u ' _α, u ' _β

Step 2: given direct voltage gets into pi regulator with the difference of the output dc voltage of netting side converter, and the output of pi regulator is the given P of active power with the long-pending of net side converter output dc voltage ^RefThe given Q of reactive power ^RefBe made as zero;

Step 3: according to step 2 obtain meritorious given and idle given; And step 1 line voltage that obtains and the AC side voltage of netting side converter and their retardation, analytical Calculation obtains netting ac-side current set-point

and of side converter

Step 4: the given Mathematical Modeling with the net side converter of the ac-side current that obtains according to step 3, calculate the AC side command voltage of net side converter, utilize SVPWM to decompose then and obtain switching drive signal.

The current control system of double-fed wind power generator net side converter during a kind of unbalanced power supply adopts said method to control.

The present invention has following characteristics and advantage:

1) ac-side current command value analytical Calculation on static two phase coordinate systems obtains, and need not to decompose with synchronously rotating reference frame conversion in the class methods and positive-negative sequence component, and control is directly simple;

2) acquisition of ac-side current command value need not current on line side and inductance parameters, receives the inductance variable effect little;

3) the present invention can reduce the side harmonics electric current when suppressing the dc voltage fluctuation, and keeps unity power factor.

Description of drawings

The control block diagram of dual-feed asynchronous wind power generator system when Fig. 1 is unbalanced source voltage;

Fig. 2 is the hardware structure diagram of wind-driven generator net side converter;

Fig. 3 is the control principle figure of wind-driven generator net side converter.

Embodiment

Below in conjunction with accompanying drawing and embodiment the present invention is done and to further describe.

The control block diagram of dual-feed asynchronous wind power generator system when Fig. 1 is unbalanced source voltage comprises wind energy conversion system, gearbox, double-fed asynchronous generator, net side converter and pusher side current transformer etc., and what the present invention is directed to is net side converter wherein.

Fig. 2 is the hardware structure diagram of wind-driven generator net side converter, comprises three phase network voltage, filter inductance, rectifier bridge main circuit, dc bus capacitor, voltage and current transducer and sampling processing circuit, dsp controller and Drive Protecting Circuit.Voltage sensor and current sensor are measured line voltage and electric current and current transformer dc voltage respectively, are converted into digital signal through the sampling processing circuit and get into dsp controller.Dsp controller is accomplished the computing of method proposed by the invention, and output pwm signal is through obtaining the final drive signal of 6 switching tubes of current transformer after the Drive Protecting Circuit.

Fig. 3 is the control principle figure of wind-driven generator net side converter.Control method shown in Fig. 3 is carried out in the dsp controller of Fig. 2.This control method may further comprise the steps:

Step 1: detection of grid side three-phase voltage e _a, e _b, e _c, current i _a, i _b, i _cWith dc voltage U _Dc, line voltage and electric current further obtain at two voltage e on the static coordinate mutually through 3/2 conversion _α, e _βAnd current i _α, i _β, specifically be expressed as:

$\left[\begin{array}{c}{e}_{\mathrm{\α}}\\ e_{\mathrm{\β}}\end{array}\right]=\frac{2}{3}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{e}_a\\ e_b\\ e_c\end{array}\right]$

$\left[\begin{array}{c}{i}_{\mathrm{\α}}\\ i_{\mathrm{\β}}\end{array}\right]=\frac{2}{3}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right]\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]$

AC side of converter voltage u _α, u _βDirectly the input voltage instruction from SVPWM obtains; e _α, e _βAnd u _α, u _βPostponing for 1/4 cycle obtains its inhibit signal e ' _α, e ' _βAnd u ' _α, u ' _β, specifically be expressed as:

$e_{\mathrm{\α}}^{\′}\left(t\right)=e_{\mathrm{\α}}(t-\frac{T}{4})$

$e_{\mathrm{\β}}^{\′}\left(t\right)=e_{\mathrm{\β}}(t-\frac{T}{4})$

$u_{\mathrm{\α}}^{\′}\left(t\right)=u_{\mathrm{\α}}(t-\frac{T}{4})$

$u_{\mathrm{\β}}^{\′}\left(t\right)=u_{\mathrm{\β}}(t-\frac{T}{4})$

Wherein T is a power frequency period, is 0.02s. for the 50Hz electrical network

Step 2: given direct voltage

With net side converter dc voltage U _DcDifference through pi regulator and be multiplied by U _DcObtain the given P of active power ^Ref, specifically be expressed as

(k _pAnd k _iBe respectively proportional gain and storage gain in the pi regulator); Reactive power set-point Q ^RefBe made as zero to obtain unity power factor;

Step 3: according to step 1 line voltage that obtains and the AC side voltage of netting side converter and their retardation; And active power and reactive power that step 2 obtains are given, and the ac-side current set-point

and that obtain netting side converter are:

$\left[\begin{array}{c}{i}_{\mathrm{\α}}^{\mathrm{ref}}\\ i_{\mathrm{\β}}^{\mathrm{ref}}\end{array}\right]=\frac{{4P}^{\mathrm{ref}}}{3\mathrm{\Δ}}\left[\begin{array}{c}{e}_{\mathrm{\β}}^{\′}(u_{\mathrm{\β}}^2+{u_{\mathrm{\β}}^{\′}}^2)+e_{\mathrm{\α}}(u_{\mathrm{\α}}{u}_{\mathrm{\β}}^{\′}-u_{\mathrm{\β}}{u}_{\mathrm{\α}}^{\′})+e_{\mathrm{\α}}^{\′}(u_{\mathrm{\α}}+u_{\mathrm{\β}}+u_{\mathrm{\α}}^{\′}{u}_{\mathrm{\β}}^{\′})\\ -e_{\mathrm{\α}}^{\′}(u_{\mathrm{\α}}^2+{u_{\mathrm{\α}}^{\′}}^2)+e_{\mathrm{\β}}(u_{\mathrm{\α}}{u}_{\mathrm{\β}}^{\′}-u_{\mathrm{\β}}{u}_{\mathrm{\α}}^{\′})-e_{\mathrm{\β}}^{\′}(u_{\mathrm{\α}}{u}_{\mathrm{\β}}+u_{\mathrm{\α}}^{\′}{u}_{\mathrm{\β}}^{\′})\end{array}\right]$

Wherein $\mathrm{\Δ}=({\mathrm{\μ}}_{\mathrm{\α}}{u}_{\mathrm{\β}}^{\′}-u_{\mathrm{\β}}{u}_{\mathrm{\α}}^{\′})(e_{\mathrm{\α}}^2+e_{\mathrm{\β}}^2+{e_{\mathrm{\α}}^{\′}}^2+{e_{\mathrm{\β}}^{\′}}^2)+(e_{\mathrm{\α}}{e}_{\mathrm{\β}}^{\′}-e_{\mathrm{\β}}{e}_{\mathrm{\α}}^{\′})(u_{\mathrm{\α}}^2+u_{\mathrm{\β}}^2+{u_{\mathrm{\α}}^{\′}}^2+{u_{\mathrm{\β}}^{\′}}^2)\underset{\‾}{;}$

Step 4: the ac-side current set-point of the net side converter that obtains according to step 3, the Mathematical Modeling of integral mess side converter makes real the principle that the border current value equals command value according to next, can obtain netting side converter AC side command voltage value u _α, u _βFor:

$\left[\begin{array}{c}{u}_{\mathrm{\α}}\\ u_{\mathrm{\β}}\end{array}\right]=\left[\begin{array}{c}{e}_{\mathrm{\α}}\\ e_{\mathrm{\β}}\end{array}\right]-\frac{L}{T_s}\left[\begin{array}{c}{i}_{\mathrm{\α}}^{\mathrm{ref}}-i_{\mathrm{\α}}\\ i_{\mathrm{\β}}^{\mathrm{ref}}-i_{\mathrm{\β}}\end{array}\right]$

Wherein L is every phase input inductance of AC side of converter, T _sBe the sampling period.u _αAnd u _βFurther decompose the drive signal that obtains netting six switching devices in the side converter through SVPWM.

Claims (4)

1. the current control method of double-fed wind power generator net side converter during a unbalanced power supply is characterized in that comprising the steps:

Steps A: according to the line voltage e on the two phase static coordinate _α, e _βWith net side converter AC side voltage u _α, u _βAnd their inhibit signal e ' _α, e ' _β, u ' _α, u ' _β, in conjunction with meritorious and the given P of reactive power ^Ref, Q ^Ref, analytical Calculation obtains the command value of AC side of converter electric current

With

$\left[\begin{array}{c}{i}_{\mathrm{\α}}^{\mathrm{ref}}\\ i_{\mathrm{\β}}^{\mathrm{ref}}\end{array}\right]=\frac{{4P}^{\mathrm{ref}}}{3\mathrm{\Δ}}\left[\begin{array}{c}{e}_{\mathrm{\β}}^{\′}(u_{\mathrm{\β}}^2+{u_{\mathrm{\β}}^{\′}}^2)+e_{\mathrm{\α}}(u_{\mathrm{\α}}{u}_{\mathrm{\β}}^{\′}-u_{\mathrm{\β}}{u}_{\mathrm{\α}}^{\′})+e_{\mathrm{\α}}^{\′}(u_{\mathrm{\α}}{u}_{\mathrm{\β}}+u_{\mathrm{\α}}^{\′}+u_{\mathrm{\β}}^{\′})\\ -e_{\mathrm{\α}}^{\′}(u_{\mathrm{\α}}^2+{u_{\mathrm{\α}}^{\′}}^2)+e_{\mathrm{\β}}(u_{\mathrm{\α}}{u}_{\mathrm{\β}}^{\′}-u_{\mathrm{\β}}{u}_{\mathrm{\α}}^{\′})-e_{\mathrm{\β}}^{\′}(u_{\mathrm{\α}}{u}_{\mathrm{\β}}+u_{\mathrm{\α}}^{\′}{u}_{\mathrm{\β}}^{\′})\end{array}\right],$

Wherein:

$\mathrm{\Δ}=({\mathrm{\μ}}_{\mathrm{\α}}{u}_{\mathrm{\β}}^{\′}-u_{\mathrm{\β}}{u}_{\mathrm{\α}}^{\′})(e_{\mathrm{\α}}^2+e_{\mathrm{\β}}^2+{e_{\mathrm{\α}}^{\′}}^2+{e_{\mathrm{\β}}^{\′}}^2)+(e_{\mathrm{\α}}{e}_{\mathrm{\β}}^{\′}-e_{\mathrm{\β}}{e}_{\mathrm{\α}}^{\′})(u_{\mathrm{\α}}^2+u_{\mathrm{\β}}^2+{u_{\mathrm{\α}}^{\′}}^2+{u_{\mathrm{\β}}^{\′}}^2);$

Step B: according to the command value of ac-side current and the Mathematical Modeling of net side converter, calculate the AC side command voltage of net side converter, produce the pulse signal of control switch pipe conducting then through SVPWM.

2. method according to claim 1 is characterized in that said steps A comprises:

(1) utilize voltage and current sensor grid side three-phase voltage, electric current and current transformer dc voltage, line voltage and electric current obtain at two voltage e on the static coordinate mutually through 3/2 conversion _α, e _βAnd current i _α, i _β

(2) AC side of converter voltage u _α, u _βObtain from the instruction of the input voltage of SVPWM, AC side of converter voltage and line voltage postpone the inhibit signal that 1/4 all after dates obtain them and are respectively u ' _α, u ' _βAnd e ' _α, e ' _β

(3) difference of given direct voltage and current transformer dc voltage is passed through pi regulator and is multiplied by dc voltage and obtains active power set-point P ^Ref, the set-point Q of reactive power ^RefBe made as zero;

(4) utilize voltage on line side and AC side of converter voltage and inhibit signal thereof; In conjunction with meritorious given, can analytical Calculation obtain command value

and of AC side of converter electric current with reactive power

3. method according to claim 1 is characterized in that said step B comprises:

(1) based on the Mathematical Modeling of net side converter, according to the command value of ac-side current, the principle that actual current value equals command value when clapping according to next can calculate the AC side command voltage of netting side converter and be:

$\left[\begin{array}{c}{u}_{\mathrm{\α}}\\ u_{\mathrm{\β}}\end{array}\right]=\left[\begin{array}{c}{e}_{\mathrm{\α}}\\ e_{\mathrm{\β}}\end{array}\right]-\frac{L}{T_s}\left[\begin{array}{c}{i}_{\mathrm{\α}}^{\mathrm{ref}}-i_{\mathrm{\α}}\\ i_{\mathrm{\β}}^{\mathrm{ref}}-i_{\mathrm{\β}}\end{array}\right]$

Wherein L is every phase input inductance of AC side of converter, and Ts is the sampling period.

(2) the AC side command voltage of net side converter further produces the pulse signal of control switch pipe conducting through SVPWM.

4. the current control system of double-fed wind power generator net side converter during a unbalanced power supply is characterized in that adopting claim 1,2 or 3 described methods to control.

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