CN106300427A - A kind of method that THE UPFC is applied in Wind turbines is incorporated into the power networks - Google Patents

Abstract

The invention discloses a kind of method that THE UPFC is applied in Wind turbines is incorporated into the power networks, belong to electric and electronic technical field, set up the autonomous control system that UPFC series side is meritorious and idle, voltage is compensated to transmission line of electricity output, study its trend distribution capability optimizing wind-electricity integration system, and set up model in Matlab/Simulink software, simulation result shows based on reactive power compensation planning powerful for UPFC and power flowcontrol ability, and UPFC can significantly improve low voltage ride-through capability and the Optimal Power Flow distribution of wind-electricity integration.

Description

A kind of method that THE UPFC is applied in Wind turbines is incorporated into the power networks

Technical field

The invention discloses a kind of method that THE UPFC is applied in Wind turbines is incorporated into the power networks, belong to electric power Technical field.

Background technology

Wind-power electricity generation has off-network and the grid-connected two kinds of method of operation.The scale of off-network type is less, is mainly used in solving From far-off regions is independently-powered.The wind-powered electricity generation that is incorporated into the power networks is the main development direction of domestic and international wind-power electricity generation, the grid-connected fortune of Wind turbines Compensation and the support of bulk power grid can be obtained after row, wind energy can be better profited from and improve wind energy turbine set stability due to wind turbine Group is different from the Synchronous generator of routine, and large-scale wind power is grid-connected changes the trend distribution of original electrical network, line transmission merit Transient characterisitics when rate and electric network fault.Access wind energy turbine set low-voltage crossing the to be had ability of electrical network, need to be in large disturbances accident Rear grid-connected point voltage can recover as early as possible, and wind power integration point can be rapidly injected reactive power, it is ensured that wind energy turbine set not off-grid runs.Wind-powered electricity generation The grid-connected trend distribution that can change original system in field, may make the service ability of certain section of circuit exceed its capacity limit, if Wind energy turbine set scale continues to expand, and this section of circuit will become the Main Bottleneck limiting wind-powered electricity generation output.

Flexible AC transmitting system (FACTS) the solution research improving wind energy turbine set fault ride-through capacity at present is more There are SVC (SVC) and static synchronous compensating device (STATCOM), the application in electrical network of the various FACTS devices Dramatic change is brought to power system.SVC, STATCOM in comparative study FACTS controller and THE UPFC (UPFC) dynamic response and the fault ride-through capacity to double-feedback aerogenerator, result shows that FACTS device can significantly improve The combination property of wind energy turbine set.Use STATCOM to improve wind energy turbine set low voltage ride-through capability, enhance the stability of wind energy turbine set.

That in FACTS device, function is the most powerful is UPFC.UPFC can regard a STATCOM and Static Synchronous Series as Compensation device (SSSC) is in parallel to be constituted so that UPFC has the ability run with STATCOM or SSSC.In addition UPFC can be real-time It is uniformly controlled or part controls the voltage of transmission line of electricity, impedance, phase angular dimensions so that it is transmission line of electricity can be controlled the most rapidly Active power and reactive power, can with after reasonably optimizing wind power integration electrical network trend be distributed, improve transmission line of electricity safety the most abundant Degree.

Summary of the invention

The technical problem to be solved is the deficiency overcoming technology, it is provided that a kind of THE UPFC The method of application in Wind turbines is incorporated into the power networks, utilizes no-power compensation function powerful for UPFC to after improving wind energy turbine set fault The ability that low voltage ride-through capability and Line Flow control.

The present invention adopts the following technical scheme that for achieving the above object

A kind of method that THE UPFC is applied in Wind turbines is incorporated into the power networks, comprises the steps:

(1) asynchronous wind driven generator is modeled by selecting system parameter；

(2) setting up the circuit model of UPFC, Dual-loop feedback control control system and the series side of setting up UPFC parallel connection side are gained merit With idle autonomous control system；

(3) UPFC is connected on wind farm grid-connected circuit, it is achieved improve the low voltage ride-through capability after wind energy turbine set fault And Line Flow control ability.

Asynchronous wind driven generator is modeled by aforesaid step (1), comprises the following steps:

(1-1) asynchronous wind-force wind turbine mechanical output P_MWith machine torque T_M, it is respectively；

$P_M=\frac{1}{2}{C}_P{\mathrm{S\ρv}}^3---\left(1\right)$

$T_M=\frac{\frac{1}{2}{C}_P{\mathrm{S\ρv}}^3}{{\mathrm{\ω}}_r}---\left(2\right)$

Wherein: C_PFor power coefficient；S is the area that blade is inswept；V is wind speed；ρ is atmospheric density；ω_rFor wind wheel Axle rotating speed；

Wherein, power coefficient C_PIt is tip speed ratio λ and the function of paddle pitch angle β:

$C_P=0.5176{(\frac{116}{{\mathrm{\λ}}_i}-0.4\mathrm{\β}-5)}^{\frac{-21}{{\mathrm{\λ}}_i}}+0.0068\mathrm{\λ}---\left(3\right)$

Wherein, λ_iExpression formula be:

$\frac{1}{{\mathrm{\λ}}_i}=\frac{1}{\mathrm{\λ}+0.08\mathrm{\β}}-\frac{0.035}{{\mathrm{\β}}^3+1}---\left(4\right)$

Tip speed ratio λ meets:

$\mathrm{\λ}=\frac{{\mathrm{\ω}}_{r}R}{v}---\left(5\right);$

(1-2), after cage type asynchronous wind-driven generator dq coordinate system transformation, corresponding mathematical model is:

Wherein: U_ds、U_qsIt is respectively stator side d axle and the voltage of q axle, i_ds、i_qsIt is respectively stator side d axle and the electricity of q axle Stream, U '_dr、U′_qrIt is respectively rotor-side d axle and the voltage of q axle, i '_dr、i′_qrIt is respectively rotor-side d axle and the electric current of q axle, R_sWith R_r' it is respectively stator resistance and rotor resistance,It is respectively stator side d axle and the magnetic flux of q axle,It is respectively and turns Sub-side d axle and the magnetic flux of q axle, ω is synchronous rotational speed, ω_rFor rotor shaft rotating speed；

(1-3) asynchronous wind driven generator electromagnetic torque is shown below:

$J\frac{{\mathrm{d\ω}}_r}{dt}=T_M-T_E---\left(8\right)$

Wherein, T_EFor asynchronous wind driven generator electromagnetic torque, P is number of pole-pairs, and J is asynchronous wind driven generator rotary module Total rotary inertia.

Aforesaid step (2) sets up the circuit model of UPFC, particularly as follows: current transformer 1 is by transformator with transmission line of electricity also Connection, current transformer 2 passes through transformator and connects with circuit, and two current transformer DC sides are connected by public capacitance；Current transformer 1 be used for Current transformer 2 provides active power, simultaneously by sending to electrical network or absorbing reactive power maintains access point voltage stabilization in parallel； Current transformer 2 exports a series compensating voltage through series transformer to circuitIts amplitude and phase angle are the most controlled, through UPFC After compensation, transmission line of electricity receiving end active power, reactive power are respectively as follows:

$P=\frac{U_1{U}_3}{X}sin\mathrm{\δ}+\frac{U_{pq}{U}_3}{X}\sin (\mathrm{\δ}+\mathrm{\ρ})---\left(9\right)$

$Q=\frac{U_3(U_{1}cos\mathrm{\δ}-U_3)}{X}+\frac{U_{pq}{U}_3}{X}cos(\mathrm{\δ}+\mathrm{\ρ})---\left(10\right)$

Wherein, P is transmission line of electricity receiving end active power, and Q is transmission line of electricity receiving end reactive power, U_pqFor series compensating voltage Amplitude, U₁、U₃Being respectively transmission system head end, terminal voltage amplitude, X is line impedance, end supply voltage phase contrast headed by δ, ρ is UPFC series compensating voltage and head end supply voltage phase contrast.

In aforesaid step (2), the control mode of the Dual-loop feedback control control system of UPFC parallel connection side is: UPFC parallel connection side Input is shunt transformer primary side voltage U_sh1With primary side current I_sh, voltage magnitude U_mWith reference voltage U_refAfter Bi compare, logical Cross P+Resonant regulator and obtain q axle reference current I_qref；DC voltage U_dcWith DC reference value U_drefMore afterwards by direct current PI Actuator i.e. obtains d axle reference current I_dref；UPFC parallel connection side input voltage, electric current obtain dq component U through dq conversion_d1, U_q1, I_d1, I_q1, then with dq axle reference current I_dref, I_qrefThe dq component of voltage U of SPWM is i.e. obtained together by rheonome_d2, U_q2, the pulse signal of output has i.e. obtained shunt transformer secondary side voltage U through current transformer 1_sh2；It is right that UPFC parallel connection side completes Asynchronous wind driven generator reactive-load compensation and false voltage recover.

In aforesaid step (2), the meritorious control mode with idle autonomous control system of UPFC series side is: UPFC goes here and there Connection side input voltage U₂With electric current I, after dq converts, obtain dq component U_d2, U_q2, I_d1, I_q1, emulation obtains actual active power P and reactive power Q, respectively with the active-power P set_refAnd reactive power Q_refAfter Bi compare, difference is inputed to respectively d axle and Q shaft voltage component actuator, obtains the dq component of voltage of SPWM after being then passed through voltage amplitude limit；Again through selecting signal to determine The input signal of SPWM is the U of automatic power flowcontrol_dAnd U_q, or voltage-controlled with reference to dq shaft voltage component U_drefAnd U_qref； Phaselocked loop is utilized to follow the tracks of transmission system head end voltage afterwardsPhase angle theta, utilize its modulate SPWM signal；Series side completes wind Electricity sends control and the optimization of the grid-connected transmission of active power.

The present invention uses technique scheme, has the advantages that

(1) controlled by the Dual-loop feedback control of UPFC parallel connection side, wind-powered electricity generation outlet line three phase short circuit fault is set and studies UPFC improves wind energy turbine set low voltage ride-through capability；

(2), during electrical network generation catastrophe failure, parallel inverter can provide reactive power support rapidly for wind energy turbine set, contributes to wind The fast quick-recovery of group of motors set end voltage；

(3) independence using UPFC series side meritorious and idle controls to compensate voltage to transmission line of electricity output, thus changes The trend distribution of wind-electricity integration system, improves the stability of circuit and the economy of operation of power networks.

Accompanying drawing explanation

Fig. 1 is the method particular flow sheet that the THE UPFC of the present invention is applied in Wind turbines is incorporated into the power networks.

Fig. 2 is UPFC basic block diagram.

Fig. 3 is UPFC comprehensive compensation vector.

Fig. 4 is UPFC parallel connection side control block diagram.

Fig. 5 is UPFC series side control block diagram.

Fig. 6 is that UPFC accesses wind-electricity integration system construction drawing.

Fig. 7 (a) is Wind turbines machine end busbar voltage curve, and Fig. 7 (b) is Wind turbines machine end active power curves, Fig. 7 C () is Wind turbines machine end reactive capability curve.

Fig. 8 is UPFC active reactive span of control figure.

Fig. 9 (a) is that UPFC series side sends active power curves, and Fig. 9 (b) is for compensating voltage magnitude curve, and Fig. 9 (c) is Compensate voltage phase angle curve.

Detailed description of the invention

The invention will be further described below in conjunction with the accompanying drawings.Following example are only used for clearly illustrating the present invention Technical scheme, and can not limit the scope of the invention with this.

The method that THE UPFC of the present invention is applied in Wind turbines is incorporated into the power networks, as it is shown in figure 1, include as follows Step:

Step 1, asynchronous wind driven generator is modeled by selecting system parameter；

Step 2, sets up the circuit model of UPFC, and UPFC parallel connection side and series side are optimized modeling；

Step 3, is connected on UPFC on wind farm grid-connected circuit, utilizes no-power compensation function big for UPFC to improve wind-powered electricity generation Low voltage ride-through capability after the fault of field and the ability of Line Flow control.

In step 1, as follows asynchronous wind driven generator is modeled:

Step 1-1, asynchronous wind driven generator mechanical output P_MWith machine torque T_MIt is respectively as follows:

$P_M=\frac{1}{2}{C}_P{\mathrm{S\ρv}}^3---\left(1\right)$

$T_M=\frac{\frac{1}{2}{C}_P{\mathrm{S\ρv}}^3}{{\mathrm{\ω}}_r}---\left(2\right)$

Wherein: C_PFor power coefficient；S is the area that blade is inswept；V is wind speed；ρ is atmospheric density；ω_rFor wind wheel Axle rotating speed.

In the case of wind speed v is given, the power that wind-driven generator obtains will depend upon which power coefficient C_P, and C_PIt is Tip speed ratio λ and the function of paddle pitch angle β:

$C_P=0.5176{(\frac{116}{{\mathrm{\λ}}_i}-0.4\mathrm{\β}-5)}^{\frac{-21}{{\mathrm{\λ}}_i}}+0.0068\mathrm{\λ}---\left(3\right)$

In above formula, λ_iExpression formula be:

$\frac{1}{{\mathrm{\λ}}_i}=\frac{1}{\mathrm{\λ}+0.08\mathrm{\β}}-\frac{0.035}{{\mathrm{\β}}^3+1}---\left(4\right)$

Tip speed ratio λ meets:

$\mathrm{\λ}=\frac{{\mathrm{\ω}}_{r}R}{v}---\left(5\right).$

Step 1-2, the equivalent circuit after cage type asynchronous wind-driven generator dq coordinate system transformation is as shown in Figure 2.Corresponding number Model:

Wherein: U_ds、U_qs、i_ds、i_qsIt is respectively stator side d axle and the voltage of q axle, electric current；U′_dr、U′_qr、i′_dr、i′_qrPoint Wei rotor-side d axle and the voltage of q axle, electric current；R_sAnd R_r' it is respectively stator resistance and rotor resistance； It is respectively stator side and rotor-side d axle and the magnetic flux of q axle；ω is synchronous rotational speed, ω_rFor rotor shaft rotating speed.

Step 1-3, asynchronous wind driven generator electromagnetic torque is shown below:

$J\frac{{\mathrm{d\ω}}_r}{dt}=T_M-T_E---\left(8\right)$

Wherein, T_EFor asynchronous wind driven generator electromagnetic torque, P is number of pole-pairs, and J is asynchronous wind driven generator rotary module Total rotary inertia.

The asynchronous wind power generator rotor equation of motion can be obtained fom the above equation.If machine torque T_MWith electromagnetic torque T_EUnequal, different Step wind-power electricity generation chance is acceleration or deceleration under uneven torque.When the grid collapses, owing to set end voltage reduces, cause Generator electromagnetic power reduces, and causes electromotor to accelerate.When system re-establishes equilibrium point after a failure, need to absorb more Reactive power.If now electrical network is not provided that enough reactive power supports, generator terminal voltage cannot recover, it will causes wind Overspeed protection or the under-voltage protection action of group of motors and cause the machine of cutting, so wind energy turbine set should have low voltage crossing energy Power.

In step 2, UPFC circuit model is set up as follows:

The basic structure of UPFC is as in figure 2 it is shown, current transformer 1 is by transformator and power transmission line parallel-connection, and current transformer 2 is by becoming Depressor is connected with circuit, and two current transformer DC sides are connected by public capacitance.Current transformer 1 is mainly used to provide to current transformer 2 Active power, simultaneously by sending to electrical network or absorbing reactive power maintains access point voltage stabilization in parallel.Current transformer 2 passes through Series transformer exports a series compensating voltage to circuitIts amplitude and phase angle are the most controlled, thus realize the main of UPFC Function.

The phasor diagram of UPFC comprehensive compensation is as it is shown on figure 3, transmission line of electricity receiving end is meritorious, reactive power is respectively as follows:

$P=\frac{U_1{U}_3}{X}sin\mathrm{\δ}+\frac{U_{pq}{U}_3}{X}\sin (\mathrm{\δ}+\mathrm{\ρ})---\left(9\right)$

$Q=\frac{U_3(U_{1}cos\mathrm{\δ}-U_3)}{X}+\frac{U_{pq}{U}_3}{X}cos(\mathrm{\δ}+\mathrm{\ρ})---\left(10\right)$

Wherein, P is transmission line of electricity receiving end active power, and Q is transmission line of electricity receiving end reactive power, U_pqFor compensating voltage amplitude Value, U₁、U₃For transmission system head end, terminal voltage amplitude, X is line impedance, end supply voltage phase contrast headed by δ, and ρ is UPFC series compensating voltage and head end supply voltage phase contrast；Voltage magnitude U is compensated by regulation_pqJust can spirit with phase contrast ρ Control circuit of living is gained merit and reactive power size and Orientation.In Fig. 2 and Fig. 3,It is respectively transmission system head end, end electricity Pressure,Busbar voltage is exported for series side.

In step 3, being connected on wind farm grid-connected circuit by UPFC, the no-power compensation function utilizing UPFC powerful improves Low voltage ride-through capability after wind energy turbine set fault and the ability of Line Flow control.UPFC parallel connection side and series connection control block diagram divide Not as shown in Figure 4, Figure 5.

UPFC parallel connection side control mode is: the input of UPFC parallel connection side is shunt transformer primary side voltage U_sh1And primary side Electric current I_sh, voltage magnitude U_mWith reference voltage U_refAfter Bi compare, obtain q axle reference current I by P+Resonant regulator_qref；Direct current Voltage U_dcWith DC reference value U_drefD axle reference current I is i.e. obtained more afterwards by direct current pi regulator_dref；UPFC parallel connection side Input voltage, electric current obtain dq component U through dq conversion_d1, U_q1, I_d1, I_q1, then with dq axle reference current I_dref, I_qrefLead to together Overcurrent actuator i.e. obtains the dq component of voltage U of SPWM_d2, U_q2, the pulse signal of output has i.e. obtained also through current transformer 1 Connection Circuit Fault on Secondary Transformer voltage U_sh2.The major function of UPFC parallel connection side be to asynchronous wind driven generator reactive-load compensation and False voltage recovers.

UPFC series side control mode is: UPFC series side input voltage U₂With electric current I, after dq converts, obtain dq divide Amount U_d2, U_q2, I_d1, I_q1, emulation obtains actual active-power P and reactive power Q, respectively with the active-power P set_refWith idle Power Q_refAfter Bi compare, difference is inputed to respectively d axle and q shaft voltage component actuator, obtains after being then passed through voltage amplitude limit The dq component of voltage of SPWM.Through the U that input signal selection signal to determine SPWM is automatic power flowcontrol again_dAnd U_q, or Voltage-controlled with reference to dq shaft voltage component U_drefAnd U_qref.Phaselocked loop is utilized to follow the tracks of transmission system head end voltage afterwardsPhase Angle θ, utilizes it to modulate SPWM signal.The major function of series side has been that wind-powered electricity generation sends the control of the grid-connected transmission of active power With optimization.

Wind energy turbine set is equivalent to six jumbo feather Module of Asynchronous Generator grid-connected systems by following example, Matlab/Simulink sets up three machine looped network models, UPFC is connected on wind farm grid-connected circuit, set up UPFC parallel connection side Dual-loop feedback control control system and the meritorious and idle autonomous control system of series side.Simulation result shows that UPFC can improve The trend distribution capability of wind energy turbine set low voltage ride-through capability and conservative control circuit, is effectively improved stablizing of wind-electricity integration system Property.

UPFC accesses wind-electricity integration system structure as shown in Figure 6.In figure, IG is the cage type asynchronous wind power generating set of feather, It is made up of 6 3MW electromotors, comprises the transformator of no-load voltage ratio 690V/35kV, 1km power transmission line, machine end shunt capacitance and machine end female Line, then access electrical network through 35kV/110kV transformator.UPFC is connected in transmission line of electricity L4, is connected on asking of bus B2 and B3, Wind-driven generator is provided the reactive power support of voltage stabilization and improves the distribution of transmission line of electricity trend.G1 and G2 is synchronous generator, Output is 200MW.Bus B4 and B5 is connected to load LOAD 1 and LOAD2 respectively, and active power is respectively 80MW and 50MW. During Load flow calculation, G1 and G2 is PV node, and G3 is balance node, LOAD1 and LOAD2 is PQ node, and IG is write from memory by system Recognize process.The flow direction of active power during the direction of arrow represents electromotor or circuit in figure.

Emulation arranges three phase short circuit fault betide machine when 18s and bring out on mouthful power transmission line, 18.2s Failure elimination.Point Not Tou Ru UPFC and do not put into UPFC and be analyzed, machine end busbar voltage, active power, reactive power are as shown in Figure 7.From figure During can be seen that fault in 7, set end voltage falls, in the case of not putting into UPFC, due to the most organic after fault disturbance disappearance End capacitor provides reactive-load compensation, and idle deficiency causes set end voltage can only return to 0.75pu, is unsatisfactory for low voltage crossing and wants Asking, for whole grid-connected unit safety, protection device excises fault unit when 21s, and set end voltage is recovered, due to machine end Electric capacity still accesses bus and causes idle surplus, so voltage slightly raises after Hui Fuing.Put into after UPFC, quick due to UPFC Reactive-power control ability, after failure vanishes, set end voltage quickly recovers at rated value, and active power and reactive power just also return to Constant value.

The wind farm grid-connected trend distribution that can change original system, in conventional electric power system, the distribution of trend is depended on Electric power networks, does not have controllability, if the scale of wind energy turbine set constantly expands, can only improve transmission of electricity by setting up new circuit Line transmission capacity.And the appearance of UPFC, make the meritorious controllability with reactive power flow of circuit become possible to.The major function of UPFC It is exactly the trend changing system, the trend after using UPFC to change wind-electricity integration in this emulation, make Line Flow rationally divide Cloth, improves the stability of electrical network.

Although UPFC has meritorious and reactive power flow independence control ability, but can be seen that it has from formula (9) and formula (10) Merit and idle span of control are affected by compensating voltage magnitude U_pq, the restriction such as phase angle ρ and line parameter circuit value.In order to obtain in Fig. 5 The span of control of UPFC, makes compensation voltage magnitude U_pqControl from 0 ° to 360 ° of change, the selection in Fig. 4 equal to 0.1pu, phase angle ρ Mode is reference voltage control, thus obtains UPFC control area as shown in Figure 8.

It is positioned at the meritorious and reactive power value in sub-elliptical region in Fig. 8, all in UPFC span of control, can see Going out UPFC to the span of control of circuit L4 active power is 95MW to 141MW.Bypassed by UPFC in Fig. 7, i.e. UPFC does not accesses again Network system, meritorious the gaining merit with each transmission line of electricity of inflow that in whole system, electromotor sends is shown in Table 1, wherein with in Fig. 6 Arrow is the positive direction of active power.

Table 1 does not puts into the wind-electricity integration system active power of UPFC

It is connected at bus B2 due to wind energy turbine set as can be seen from Table 1, causes the trend flowing through circuit L4 bigger than normal.Wind-electricity integration Gaining merit that each circuit of system flows into is: single loop line L1, meritorious respectively 102.13MW, the 96.54MW that L2, L4 flow into, 118.88MW；Double loop L3 flows into and gains merit for 212.65MW, and averagely every circuit is 106.32MW.Circuit L2 and L4 power difference 22.34MW.Using UPFC to optimize Line Flow, circuit L4 gains merit reference value P_refStationary value when UPFC does not puts into 118.88MW changes to setting value 108MW, to alleviate circuit L4 active power, reactive power Q_refRemain original value- 5.80Mvar.After optimization, meritorious numerical value is as shown in table 2.

Table 2 puts into the wind-electricity integration system active power of UPFC

After putting into UPFC, the trend that can obtain each circuit from table 2 is: single loop line L1, and gaining merit that L2, L4 flow into is respectively 91.03MW,107.64MW,108.00MW；Double loop L3 flows into and gains merit for 218.87MW, and averagely every circuit is 110.94MW. It appeared that after UPFC power flowcontrol, flow through circuit L2 and L4 active power difference be the least, effectively alleviate circuit L4's Current-carrying capacity.Flow through the active power of UPFC and compensate voltage magnitude U_pq, phase angle ρ as shown in Figure 9.

Be can be seen that before l0s by Fig. 9 (a), the trend that circuit L4 flows through naturally is that 118.88MW, UPFC throw when l0s Entering to run, the transition through about 2s asks that circuit L4's is meritorious stable at 108MW.Fig. 9 (b) and Fig. 9 (c) shows that series connection is lateral The compensation voltage of circuit output, amplitude is 0.04pu, and phase angle is-90 °.Simulation result shows UPFC parallel connection side and series side unsteady flow Device collaborative work, series side can provide to circuit and compensate voltage, thus change the trend distribution of wind-electricity integration system, improve line The stability on road and the economy of operation of power networks.

The above is only the preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art For Yuan, on the premise of without departing from the technology of the present invention principle, it is also possible to make some improvement and deformation, these improve and deformation Also should be regarded as protection scope of the present invention.

Claims (5)

1. the method that a THE UPFC is applied in Wind turbines is incorporated into the power networks, it is characterised in that include walking as follows Rapid:

(1) asynchronous wind driven generator is modeled by selecting system parameter；

(2) set up the circuit model of UPFC, set up the Dual-loop feedback control control system of UPFC parallel connection side and series side is meritorious and nothing The autonomous control system of merit；

(3) UPFC is connected on wind farm grid-connected circuit, it is achieved improve the low voltage ride-through capability after wind energy turbine set fault and Line Flow control ability.

The method that a kind of THE UPFC the most according to claim 1 is applied in Wind turbines is incorporated into the power networks, its Being characterised by, asynchronous wind driven generator is modeled by described step (1), comprises the following steps:

(1-1) asynchronous wind-force wind turbine mechanical output P_MWith machine torque T_M, it is respectively；

$P_M=\frac{1}{2}{C}_P{\mathrm{S\ρv}}^3---\left(1\right)$

$T_M=\frac{\frac{1}{2}{C}_P{\mathrm{S\ρv}}^3}{{\mathrm{\ω}}_r}---\left(2\right)$

Wherein: C_PFor power coefficient；S is the area that blade is inswept；V is wind speed；ρ is atmospheric density；ω_rTurn for rotor shaft Speed；

Wherein, power coefficient C_PIt is tip speed ratio λ and the function of paddle pitch angle β:

$C_P=0.5176{(\frac{116}{{\mathrm{\λ}}_i}-0.4\mathrm{\β}-5)}^{\frac{-21}{{\mathrm{\λ}}_i}}+0.0068\mathrm{\λ}---\left(3\right)$

Wherein, λ_iExpression formula be:

$\frac{1}{{\mathrm{\λ}}_i}=\frac{1}{\mathrm{\λ}+0.08\mathrm{\β}}-\frac{0.035}{{\mathrm{\β}}^3+1}---\left(4\right)$

Tip speed ratio λ meets:

$\mathrm{\λ}=\frac{{\mathrm{\ω}}_{r}R}{v}---\left(5\right);$

(1-2), after cage type asynchronous wind-driven generator dq coordinate system transformation, corresponding mathematical model is:

Wherein: U_ds、U_qsIt is respectively stator side d axle and the voltage of q axle, i_ds、i_qsIt is respectively stator side d axle and the electric current of q axle, U ′_dr、U′_qrIt is respectively rotor-side d axle and the voltage of q axle, i '_dr、i′_qrIt is respectively rotor-side d axle and the electric current of q axle, R_sAnd R_r' point Not Wei stator resistance and rotor resistance,It is respectively stator side d axle and the magnetic flux of q axle,It is respectively rotor-side d Axle and the magnetic flux of q axle, ω is synchronous rotational speed, ω_rFor rotor shaft rotating speed；

(1-3) asynchronous wind driven generator electromagnetic torque is shown below:

$J\frac{{\mathrm{d\ω}}_r}{dt}=T_M-T_E---\left(8\right)$

Wherein, T_EFor asynchronous wind driven generator electromagnetic torque, P is number of pole-pairs, and J is that the total of asynchronous wind driven generator rotary module turns Dynamic inertia.

The method that a kind of THE UPFC the most according to claim 1 is applied in Wind turbines is incorporated into the power networks, its Being characterised by, described step (2) sets up the circuit model of UPFC, particularly as follows: current transformer 1 is by transformator with transmission line of electricity also Connection, current transformer 2 passes through transformator and connects with circuit, and two current transformer DC sides are connected by public capacitance；Current transformer 1 be used for Current transformer 2 provides active power, simultaneously by sending to electrical network or absorbing reactive power maintains access point voltage stabilization in parallel； Current transformer 2 exports a series compensating voltage through series transformer to circuitIts amplitude and phase angle are the most controlled, through UPFC After compensation, transmission line of electricity receiving end active power, reactive power are respectively as follows:

$P=\frac{U_1{U}_3}{X}sin\mathrm{\δ}+\frac{U_{pq}{U}_3}{X}sin(\mathrm{\δ}+\mathrm{\ρ})---\left(9\right)$

$Q=\frac{U_3(U_{1}cos\mathrm{\δ}-U_3)}{X}+\frac{U_{pq}{U}_3}{X}cos(\mathrm{\δ}+\mathrm{\ρ})---\left(10\right)$

Wherein, P is transmission line of electricity receiving end active power, and Q is transmission line of electricity receiving end reactive power, U_pqFor series compensating voltage width Value, U₁、U₃Being respectively transmission system head end, terminal voltage amplitude, X is line impedance, end supply voltage phase contrast, ρ headed by δ For UPFC series compensating voltage and head end supply voltage phase contrast.

The method that a kind of THE UPFC the most according to claim 1 is applied in Wind turbines is incorporated into the power networks, its Being characterised by, in described step (2), the control mode of the Dual-loop feedback control control system of UPFC parallel connection side is: UPFC parallel connection side Input is shunt transformer primary side voltage U_sh1With primary side current I_sh, voltage magnitude U_mWith reference voltage U_refAfter Bi compare, logical Cross P+Resonant regulator and obtain q axle reference current I_qref；DC voltage U_dcWith DC reference value U_drefMore afterwards by direct current PI Actuator i.e. obtains d axle reference current I_dref；UPFC parallel connection side input voltage, electric current obtain dq component U through dq conversion_d1, U_q1, I_d1, I_q1, then with dq axle reference current I_dref, I_qrefThe dq component of voltage U of SPWM is i.e. obtained together by rheonome_d2, U_q2, the pulse signal of output has i.e. obtained shunt transformer secondary side voltage U through current transformer 1_sh2；It is right that UPFC parallel connection side completes Asynchronous wind driven generator reactive-load compensation and false voltage recover.

The method that a kind of THE UPFC the most according to claim 1 is applied in Wind turbines is incorporated into the power networks, its Being characterised by, in described step (2), the meritorious control mode with idle autonomous control system of UPFC series side is: UPFC goes here and there Connection side input voltage U₂With electric current I, after dq converts, obtain dq component U_d2, U_q2, I_d1, I_q1, emulation obtains actual active power P and reactive power Q, respectively with the active-power P set_refAnd reactive power Q_refAfter Bi compare, difference is inputed to respectively d axle and Q shaft voltage component actuator, obtains the dq component of voltage of SPWM after being then passed through voltage amplitude limit；Again through selecting signal to determine The input signal of SPWM is the U of automatic power flowcontrol_dAnd U_q, or voltage-controlled with reference to dq shaft voltage component U_drefAnd U_qref； Phaselocked loop is utilized to follow the tracks of transmission system head end voltage afterwardsPhase angle theta, utilize its modulate SPWM signal；Series side completes wind Electricity sends control and the optimization of the grid-connected transmission of active power.