CN103208816B - Power collection and transmission system for wind power plant and voltage control method for alternating current generatrix of power collection and transmission system - Google Patents

Abstract

The invention discloses a power collection and transmission system for a wind power plant. The system comprises an alternating current generatrix, a wind generating set, a rectifier station and an inverter station, wherein the rectifier station comprises a rectifier and a converter transformer; the direct current side of the rectifier is connected with the direct current side of the inverter station, and the alternating current side of the rectifier is connected with one side of the converter transformer through a converter inductor; and the other side of the converter transformer is connected with the alternating current generatrix, and is grounded through a capacitor. The invention also discloses a voltage control method for the alternating current generatrix of the system. The voltage comprising the amplitude and frequency of the voltage of the alternating current generatrix of the system is integrally controlled by two control dimensions of the rectifier on a wind power plant side, so that the stability of the alternating current voltage of the power collection and transmission system of the wind power plant is ensured, and harmonic components of an alternating current system of the wind power plant are reduced.

Description

A kind of current collection transmission system of wind energy turbine set and ac bus voltage control method thereof

Technical field

The invention belongs to electric power system power transmission and distribution technical field, be specifically related to a kind of current collection transmission system and ac bus voltage control method thereof of wind energy turbine set.

Background technology

Along with energy scarcity and environmental change, wind energy receives very large concern, need to utilize science and technology to develop wind energy, wind-powered electricity generation is one of them good approach, wind power generation develops rapidly, the construction of wind turbine and wind energy turbine set is very fast, but due to instability and the uncertainty of wind energy, in order to ensure the safety and stability that national grid runs, wind energy turbine set safety and stability is grid-connected is the technical bottleneck and the difficult problem that limit Wind Power Development always, no matter be landwid electric field, or marine wind electric field, all can run into this problem.

At present both at home and abroad about wind farm grid-connected method mainly contains following several: (1) wind energy turbine set slip ring system is by alternating current circuit (cable or overhead wire) direct grid-connected; (2) wind energy turbine set slip ring system is through rectifier, DC line (cable or overhead wire), inverter, i.e. Technology of HVDC based Voltage Source Converter incoming transport electrical network.Second method, namely has following advantage by flexible DC power transmission is grid-connected than the first alternating current circuit direct grid-connected: 1. can realize long distance power transmission; 2. by rectifier and inverter control, can provide reactive power support for AC system, this has very important meaning for maintenance AC system voltage stabilization; 3. wind energy turbine set slip ring system and AC system relatively independent, AC fault such as directly can not to transmit at the advantage.

A problem can be run into, the problem that namely wind energy turbine set slip ring system busbar voltage is stable when wind energy turbine set adopts flexible DC power transmission grid-connected.Wind energy turbine set slip ring system and AC system relatively independent, wind energy turbine set slip ring system voltage is difficult to contact with external electrical network, is only associated with inner wind-driven generator and flexible direct current power transmission system rectifier.Not also very perfect by the technology of wind-driven generator domination set electric system voltage, add uncontrollability and the uncertainty of wind energy itself in addition, wind-driven generator self is exerted oneself neither be very stable with electrical characteristic, therefore, flexible direct current power transmission system rectifier is needed comparatively suitable and appropriate to control wind energy turbine set slip ring system voltage.

The people such as Huang Chuan, Wang Zhixin, Wang Guoqiang are marine wind electric field three level VSC-HVDC (HVDC Transmission Technology of voltage-source type) system emulation research (power electronic technology at title, 2011,45 (8), 89 ~ 92) a kind of method of wind energy turbine set slip ring system busbar voltage is proposed in document, it by controlling wind farm side rectifier output reactive power, thus reaches the object of domination set electric system alternating voltage.Although this method can control wind energy turbine set slip ring system alternating voltage amplitude to a certain extent, because it uses wind energy turbine set rectifier dimension to control alternating voltage, control action cannot be played to alternating current voltage frequency.Wind energy turbine set slip ring system alternating voltage and whole wind energy turbine set safe and stable operation closely related, the instability of slip ring system alternating current voltage frequency, can transmit at wind energy turbine set internal communication circuit, to increase exchanges system harmonics component, harmonic component can be delivered to blower interior further, the inner heating in winding of wind turbine, affect electric elements useful life, very large infringement is produced for wind turbine, in addition, harmonic wave also can bring more loss, and wind energy turbine set exports energy efficiency and reduces, and also can affect the stable operation of wind energy turbine set simultaneously.

Summary of the invention

For the above-mentioned technological deficiency existing for prior art, the invention provides a kind of current collection transmission system and ac bus voltage control method thereof of wind energy turbine set, can keeping system alternating current voltage frequency stable, reduce wind energy turbine set harmonic component.

A current collection transmission system for wind energy turbine set, comprising: ac bus, wind turbine generator, converting plant and Inverter Station; Wind turbine generator comprises multiple stage wind-driven generator, and described wind-driven generator is connected with ac bus, and the AC of converting plant is connected with ac bus, and the DC side of converting plant is connected with the DC side of Inverter Station, and the AC of Inverter Station is connected with AC network.

Described converting plant comprises rectifier and converter transformer; The DC side of rectifier is connected with the DC side of Inverter Station, and the AC of rectifier is connected with the side of converter transformer by change of current inductance, and the opposite side of converter transformer is connected with ac bus and passes through capacitor grounding.

Described rectifier adopts three-phase six bridge arm structure, and each brachium pontis forms by several IGBT cascades.

The ac bus voltage control method of above-mentioned current collection transmission system, comprises the steps:

(1) the three-phase input current I of converting plant is gathered _a~ I _c, flow into the three-phase branch current I of converter transformer _sa~ I _scand the three-phase bus voltage U of ac bus _a~ U _c;

(2) respectively to described three-phase branch current I _sa~ I _sc, three-phase input current I _a~ I _cwith three-phase bus voltage U _a~ U _ccarry out the d axle component I that dq conversion obtains three-phase branch current _sdwith q axle component I _sq, three-phase input current d axle component I _dwith q axle component I _q, three-phase bus voltage d axle component U _dwith q axle component U _q;

(3) given d shaft voltage controlled quentity controlled variable U is made _drefwith q shaft voltage controlled quentity controlled variable U _qrefdeduct the d axle component U of three-phase bus voltage respectively _dwith q axle component U _q, obtain d shaft voltage error signal Δ U _dwith q shaft voltage error signal Δ U _q;

(4) to d shaft voltage error signal Δ U _dwith q shaft voltage error signal Δ U _qcarry out PI respectively successively to regulate and Feedforward Decoupling compensation, obtain d shaft current controlled quentity controlled variable I _drefwith q shaft current controlled quentity controlled variable I _qref;

(5) described d shaft current controlled quentity controlled variable I is made _drefwith q shaft current controlled quentity controlled variable I _qrefdeduct the d axle component I of three-phase branch current respectively _sdwith q axle component I _sq, obtain d shaft current error signal Δ I _dwith q shaft current error signal Δ I _q;

(6) to d shaft current error signal Δ I _dwith q shaft current error signal Δ I _qcarry out PI respectively successively to regulate and Feedforward Decoupling compensation, obtain d axle modulation signal M _dwith q axle modulation signal M _q;

(7) to d axle modulation signal M _dwith q axle modulation signal M _qcarry out dq inverse transformation and obtain three-phase modulations signal M _a~ M _c, and then according to described three-phase modulations signal M _a~ M _cone group of pwm signal is generated to control rectifier by SPWM (Sine Wave Pulse Width Modulation) technology.

In described step (4), according to following formula to d shaft voltage error signal Δ U _dwith q shaft voltage error signal Δ U _qcarry out PI to regulate and Feedforward Decoupling compensation:

$I_{\mathrm{dref}}=(K_{p1}+\frac{K_{i1}}{s})\mathrm{\Δ}{U}_d+I_d-I_{\mathrm{Ld}}$

$I_{\mathrm{qref}}=(K_{p2}+\frac{K_{i2}}{s})\mathrm{\Δ}{U}_q+I_q+I_{\mathrm{Lq}}$

Wherein: s is Laplacian, K _p1and K _p2be given proportionality coefficient, K _i1and K _i2be given integral coefficient, I _ldand I _lqfor d shaft current Front Feed Compensation and q shaft current Front Feed Compensation.

Described d shaft current Front Feed Compensation I _ldwith q shaft current Front Feed Compensation I _lqtry to achieve according to following formula:

I _Ld＝ωCU _q

I _Lq＝ωCU _d

Wherein: ω is the angular frequency of ac bus voltage and ω=2 π f, and f=50Hz, C are the capacitance of capacitor.

In described step (6), according to following formula to d shaft current error signal Δ I _dwith q shaft current error signal Δ I _qcarry out PI to regulate and Feedforward Decoupling compensation:

$M_d=\frac{2[(K_{p3}+\frac{K_{i3}}{s})\mathrm{\Δ}{I}_d+U_d-U_{\mathrm{Ld}}]}{U_{\mathrm{dc}}}$

$M_q=\frac{2[(K_{p4}+\frac{K_{i4}}{s})\mathrm{\Δ}{I}_q+U_q+U_{\mathrm{Lq}}]}{U_{\mathrm{dc}}}$

Wherein: s is Laplacian, K _p3and K _p4be given proportionality coefficient, K _i3and K _i4be given integral coefficient, U _ldand U _lqfor d shaft voltage Front Feed Compensation and q shaft voltage Front Feed Compensation, U _dcfor the DC bus-bar voltage of converting plant.

Described d shaft voltage Front Feed Compensation U _ldwith q shaft voltage Front Feed Compensation U _lqtry to achieve according to following formula:

U _Ld＝ωLI _sq

U _Lq＝ωLI _sd

Wherein: ω is the angular frequency of ac bus voltage and ω=2 π f, f=50Hz, L are the total inductance value of change of current inductance and converter transformer leakage inductance.

Wind energy turbine set is when using flexible DC power transmission grid-connected, the more difficult control of its wind energy turbine set slip ring system ac bus voltage, frequency is also difficult to stablize, and system ac bus voltage has vital effect for the safe and stable operation of wind energy turbine set and even whole wind-electricity integration system.Adopt ac bus voltage control method of the present invention, two of wind farm side rectifier fully can be used to control dimension, on the whole the ac bus voltage of control system, comprise amplitude and the frequency of voltage, therefore Advantageous Effects of the present invention is:

(1) the stable of wind energy turbine set slip ring system alternating voltage is ensured, the harmonic component of wind energy turbine set AC system can be reduced, prevent the damage that harmonic component is brought to wind energy turbine set inside and even wind turbine, reduce the infringement of the wind turbine electric elements inside caused by harmonic component, comprise generator, transformer, transmission line and corresponding electric appliance element, thus ensure the life-span of electric equipment and normally run.

(2) harmonic component of wind energy turbine set AC system is reduced, can reduce the wastage further, reduce the supplementary load loss that generator and transformer and circuit produce because of harmonic component, reduce the power loss of harmonic component at electric component, make full use of place capacity, the utilance of guarantee equipment, improves wind energy turbine set and exports energy efficiency.

(3) because wind power control system needs to gather wind energy turbine set slip ring system alternating voltage as input signal amount, therefore, keep the stable of wind energy turbine set slip ring system voltage magnitude and frequency, even running for wind power control system is also very helpful, thus ensures wind energy turbine set and the stable operation of whole wind-electricity integration system safety.

Accompanying drawing explanation

Fig. 1 is the structural representation of current collection transmission system of the present invention.

Fig. 2 is the principle process schematic diagram of present system ac bus voltage control method.

Fig. 3 is the waveform schematic diagram of system ac bus voltage under employing control method of the present invention.

Fig. 4 is the comparison schematic diagram adopting system ac bus voltage harmonic component under prior art and the inventive method.

Embodiment

In order to more specifically describe the present invention, below in conjunction with the drawings and the specific embodiments, technical scheme of the present invention and control method thereof are described in detail.

As shown in Figure 1, a kind of current collection transmission system of wind energy turbine set, comprising: ac bus, wind turbine generator, converting plant and Inverter Station; Wind turbine generator comprises multiple stage wind-driven generator, and wind-driven generator is successively by total power converter, current collection inductance L _jand the mode of connection is the current collection transformer T of Δ/Y _jbe connected with ac bus;

Converting plant comprises rectifier and converter transformer T; Rectifier adopts three-phase six bridge arm structure, and each brachium pontis forms by several IGBT cascades; The DC side of rectifier is connected with the DC side of Inverter Station by power transmission line, the AC of rectifier is that the side of the converter transformer T of Y/ Δ is connected by change of current inductance L and the mode of connection, and the opposite side of converter transformer T is connected with ac bus and passes through capacitor C ground connection.

Inverter Station adopts the inverter of three-phase six bridge arm structure, and each brachium pontis forms by several IGBT cascades; The DC side of rectifier and the DC side of inverter are all parallel with dc-link capacitance, and the voltage at two ends, rectifier DC side is the DC bus-bar voltage U of converting plant _dc, the AC of inverter is by transmission of electricity inductance L _sand the mode of connection is the transmitting transformer T of Δ/Y _sbe connected with AC network.

As shown in Figure 2, the ac bus voltage control method of above-mentioned current collection transmission system, comprises the steps:

(1) electric current and voltage Hall element is utilized to gather the three-phase input current I of converting plant _a~ I _c, flow into the three-phase branch current I of converter transformer T _sa~ I _scand the three-phase bus voltage U of ac bus _a~ U _c.

(2) respectively to three-phase branch current I _sa~ I _sc, three-phase input current I _a~ I _cwith three-phase bus voltage U _a~ U _ccarry out the d axle component I that dq conversion obtains three-phase branch current _sdwith q axle component I _sq, three-phase input current d axle component I _dwith q axle component I _q, three-phase bus voltage d axle component U _dwith q axle component U _q;

Dq transformation matrix is as follows:

$T_{\mathrm{abc}/\mathrm{dq}}=\frac{2}{3}\·\left[\begin{array}{ccc}\cos \mathrm{\θ}& \cos (\mathrm{\θ}-\frac{2\mathrm{\π}}{3})& \cos (\mathrm{\θ}-\frac{4\mathrm{\π}}{3})\\ \sin \mathrm{\θ}& \sin (\mathrm{\θ}-\frac{2\mathrm{\π}}{3})& \sin (\mathrm{\θ}-\frac{4\mathrm{\π}}{3})\end{array}\right]$

Wherein: θ is the phase place of ac bus voltage and θ=ω t, ω are the angular frequency of ac bus voltage and ω=2 π f, and f=50Hz, t are the time.

(3) given d shaft voltage controlled quentity controlled variable U is made _drefwith q shaft voltage controlled quentity controlled variable U _qrefdeduct the d axle component U of three-phase bus voltage respectively _dwith q axle component U _q, obtain d shaft voltage error signal Δ U _dwith q shaft voltage error signal Δ U _q; In present embodiment, U _qref=0,

(4) according to following formula to d shaft voltage error signal Δ U _dwith q shaft voltage error signal Δ U _qcarry out PI respectively successively to regulate and Feedforward Decoupling compensation, obtain d shaft current controlled quentity controlled variable I _drefwith q shaft current controlled quentity controlled variable I _qref; $I_{\mathrm{dref}}=(K_{p1}+\frac{K_{i1}}{s})\mathrm{\Δ}{U}_d+I_d-I_{\mathrm{Ld}}$ I _Ld＝ωCU _q $I_{\mathrm{qref}}=(K_{p2}+\frac{K_{i2}}{s})\mathrm{\Δ}{U}_q+I_q+I_{\mathrm{Lq}}$ I _Lq＝ωCU _d

Wherein: s is Laplacian, K _p1and K _p2be given proportionality coefficient, K _i1and K _i2be given integral coefficient, I _ldand I _lqfor d shaft current Front Feed Compensation and q shaft current Front Feed Compensation, C is the capacitance of capacitor; In present embodiment, K _p1=K _p2=0.8, K _i1=20, K _i2=100, C=2 × 10 ^-3f.

(5) d shaft current controlled quentity controlled variable I is made _drefwith q shaft current controlled quentity controlled variable I _qrefdeduct the d axle component I of three-phase branch current respectively _sdwith q axle component I _sq, obtain d shaft current error signal Δ I _dwith q shaft current error signal Δ I _q.

(6) according to following formula to d shaft current error signal Δ I _dwith q shaft current error signal Δ I _qcarry out PI respectively successively to regulate and Feedforward Decoupling compensation, obtain d axle modulation signal M _dwith q axle modulation signal M _q; $M_d=\frac{2[(K_{p3}+\frac{K_{i3}}{s})\mathrm{\Δ}{I}_d+U_d-U_{\mathrm{Ld}}]}{U_{\mathrm{dc}}}$ U _Ld＝ωLI _sq $M_q=\frac{2[(K_{p4}+\frac{K_{i4}}{s})\mathrm{\Δ}{I}_q+U_q+U_{\mathrm{Lq}}]}{U_{\mathrm{dc}}}$ U _Lq＝ωLI _sd

Wherein: K _p3and K _p4be given proportionality coefficient, K _i3and K _i4be given integral coefficient, U _ldand U _lqfor d shaft voltage Front Feed Compensation and q shaft voltage Front Feed Compensation, L is the total inductance value of change of current inductance and converter transformer leakage inductance, U _dcfor the DC bus-bar voltage of converting plant; In present embodiment, K _p3=K _p4=5.2, K _i3=K _i4=50, C=5.2 × 10 ^-3f, U _dc=100kV.

(7) to d axle modulation signal M _dwith q axle modulation signal M _qcarry out dq inverse transformation and obtain three-phase modulations signal M _a~ M _c, and then according to three-phase modulations signal M _a~ M _cone group of pwm signal is generated to carry out switch control rule to IGBT each in rectifier by SPWM technology.

Dq reverse transform matrix is as follows:

$T_{\mathrm{dq}/\mathrm{abc}}=\left[\begin{array}{cc}\cos \mathrm{\θ}& \sin \mathrm{\θ}\\ \cos (\mathrm{\θ}-\frac{2\mathrm{\π}}{3})& \sin (\mathrm{\θ}-\frac{2\mathrm{\π}}{3})\\ \cos (\mathrm{\θ}-\frac{4\mathrm{\π}}{3})& \sin (\mathrm{\θ}-\frac{4\mathrm{\π}}{3})\end{array}\right]$

In present embodiment, wind energy turbine set is connected to the grid by flexible direct current power transmission system, and wind energy turbine set slip ring system is connected with rectifier in flexible direct current power transmission system, is connected to inverter, then incoming transport electrical network through 100km direct current transportation cable.System rectifier controls dimension by two and controls wind energy turbine set slip ring system ac bus voltage magnitude and frequency, and inverter controls dimension by two and controls flexible direct current power transmission system direct voltage and system output reactive power.Expect that obtaining ac bus line voltage effective value is 35kV, the no-load voltage ratio of converter transformer T is 35/110kV.The active power of output P=100MW of whole wind energy turbine set current collection transmission system, output reactive power Q=0Mvar.

Fig. 3 is after the flexible DC power transmission wind-electricity integration slip ring system ac bus voltage control method of employing present embodiment, the oscillogram of wind energy turbine set slip ring system three-phase alternating current busbar voltage.As can see from Figure 3, flexible DC power transmission wind-electricity integration slip ring system ac bus voltage is after use present embodiment control method, three-phase alternating voltage amplitude, frequency conform to desired value, voltage magnitude and frequency are controlled effectively, three phase sine waveform is clear, phase 120 degree, wind-electricity integration slip ring system ac bus voltage control is stablized.

Fig. 4 adopts the slip ring system ac bus voltage control method of existing control method and present embodiment for the comparison schematic diagram of slip ring system ac bus voltage harmonic component THD value.Two curves in Fig. 4 represent respectively and use existing control method and present embodiment for flexible DC power transmission wind farm grid-connected slip ring system ac bus voltage harmonic component THD value.As can see from Figure 4, the slip ring system ac bus voltage harmonic component THD value adopting existing control method to obtain is about 0.042 and fluctuation is larger, the slip ring system ac bus voltage harmonic component THD value that obtains of present embodiment is adopted to be about 0.017 and comparatively stable near mean value, harmonic component obtains to a great extent and suppresses and reduce, reduce the impact of harmonic wave for wind energy turbine set inside and whole grid-connected system, reduce supplementary load loss, improve wind-electricity integration transmitting energy efficiency, ensure that the safe and stable operation of system.

Claims (1)

1. an ac bus voltage control method for the current collection transmission system of wind energy turbine set, described current collection transmission system comprises ac bus, wind turbine generator, converting plant and Inverter Station; Wind turbine generator comprises multiple stage wind-driven generator, and described wind-driven generator is connected with ac bus, and the AC of converting plant is connected with ac bus, and the DC side of converting plant is connected with the DC side of Inverter Station, and the AC of Inverter Station is connected with AC network; Described converting plant comprises rectifier and converter transformer; The DC side of rectifier is connected with the DC side of Inverter Station, and the AC of rectifier is connected with the side of converter transformer by change of current inductance, and the opposite side of converter transformer is connected with ac bus and passes through capacitor grounding;

Described ac bus voltage control method comprises the steps:

(1) the three-phase input current I of converting plant is gathered _a~ I _c, flow into the three-phase branch current I of converter transformer _sa~ I _scand the three-phase bus voltage U of ac bus _a~ U _c;

(2) respectively to described three-phase branch current I _sa~ I _sc, three-phase input current I _a~ I _cwith three-phase bus voltage U _a~ U _ccarry out the d axle component I that dq conversion obtains three-phase branch current _sdwith q axle component I _sq, three-phase input current d axle component I _dwith q axle component I _q, three-phase bus voltage d axle component U _dwith q axle component U _q;

(3) given d shaft voltage controlled quentity controlled variable U is made _drefwith q shaft voltage controlled quentity controlled variable U _qrefdeduct the d axle component U of three-phase bus voltage respectively _dwith q axle component U _q, obtain d shaft voltage error signal Δ U _dwith q shaft voltage error signal Δ U _q;

(4) according to following formula to d shaft voltage error signal Δ U _dwith q shaft voltage error signal Δ U _qcarry out PI respectively successively to regulate and Feedforward Decoupling compensation, obtain d shaft current controlled quentity controlled variable I _drefwith q shaft current controlled quentity controlled variable I _qref;

$\begin{array}{cc}{I}_{\mathrm{dref}}=(K_{p1}+\frac{K_{i1}}{s})\mathrm{\Δ}{U}_d+I_d-I_{\mathrm{Ld}}& I_{\mathrm{Ld}}={\mathrm{\ωCU}}_q\\ I_{\mathrm{qref}}=(K_{p2}+\frac{K_{i2}}{s}){\mathrm{\ΔU}}_q+I_q+I_{\mathrm{Lq}}& I_{\mathrm{Lq}}={\mathrm{\ωCU}}_d\end{array}$

Wherein: s is Laplacian, K _p1and K _p2be given proportionality coefficient, K _i1and K _i2be given integral coefficient, I _ldand I _lqfor d shaft current Front Feed Compensation and q shaft current Front Feed Compensation; ω is the angular frequency of ac bus voltage and ω=2 π f, and f=50Hz, C are the capacitance of capacitor;

(5) described d shaft current controlled quentity controlled variable I is made _drefwith q shaft current controlled quentity controlled variable I _qrefdeduct the d axle component I of three-phase branch current respectively _sdwith q axle component I _sq, obtain d shaft current error signal Δ I _dwith q shaft current error signal Δ I _q;

(6) according to following formula to d shaft current error signal Δ I _dwith q shaft current error signal Δ I _qcarry out PI respectively successively to regulate and Feedforward Decoupling compensation, obtain d axle modulation signal M _dwith q axle modulation signal M _q;

$\begin{array}{cc}{M}_d=\frac{2[(K_{p3}+\frac{K_{i3}}{s}){\mathrm{\ΔI}}_d+U_d-U_{\mathrm{Ld}}}{U_{\mathrm{dc}}}& U_{\mathrm{Ld}}={\mathrm{\ωLI}}_{\mathrm{sq}}\\ M_q=\frac{2[(K_{p4}+\frac{K_{i4}}{s}){\mathrm{\ΔI}}_q+U_q+U_{\mathrm{Lq}}}{U_{\mathrm{dc}}}& U_{\mathrm{Lq}}={\mathrm{\ωLI}}_{\mathrm{sd}}\end{array}$

Wherein: K _p3and K _p4be given proportionality coefficient, K _i3and K _i4be given integral coefficient, U _ldand U _lqfor d shaft voltage Front Feed Compensation and q shaft voltage Front Feed Compensation, U _dcfor the DC bus-bar voltage of converting plant, L is the total inductance value of change of current inductance and converter transformer leakage inductance;

(7) to d axle modulation signal M _dwith q axle modulation signal M _qcarry out dq inverse transformation and obtain three-phase modulations signal M _a~ M _c, and then according to described three-phase modulations signal M _a~ M _cone group of pwm signal is generated to control rectifier by SPWM technology.