CN105048904A - Doubly-fed wind generator fault control method in two-phase stationary coordinate system - Google Patents

Abstract

The invention discloses a doubly-fed wind generator fault control method in a two-phase stationary coordinate system. A stator flux linkage and a rotor flux linkage are calculated from a stator current and a rotor current in a stator reference two-phase stationary coordinate system, a rotor voltage formula is dispersed, a rotor voltage prediction model is obtained, in the model, in order to make the rotor flux linkage to follow a given value, a value of the flux linkage of the rotor in the next moment is replaced by a given value of the rotor flux linkage at the same moment, the given value of the rotor flux linkage follows an actual value of the stator flux linkage. A rotor voltage in the predicted stator reference two-phase stationary coordinate system is subjected to coordinate transition, a rotor voltage in a two-phase rotor speed rotating coordinate system is obtained, and finally PWM modulation is carried out. Through the method, a rotor fault current can be controlled within a current being 1.5-1.6 times of the rated current, during the fault period, the electromagnetic torque ripple is small, and the ride-through operation capability under the doubly-fed wind generator fault is raised.

Description

Double-fed wind power generator fault control method under two-phase rest frame

Technical field

The invention belongs to double-fed wind power generator and run control field, double-fed wind power generator fault control method under two-phase rest frame when being specifically related to a kind of Voltage Drop, to ensure between age at failure generator not off-grid run.

Background technology

Wind-powered electricity generation more and more comes into one's own in electrical production, the interaction between jumbo Wind turbines with network system, phase coadaptation, and the various failure problems occurred thus define research and development content important in wind generating technology.The installed capacity of double-fed wind power generator proportion in electric power system increased fast in recent years, influencing each other between they and partial electric grid is also increasing, due to the stator and rotor direct grid-connected of double-fed wind power generator, electric network fault is very large on Wind turbines impact, and in case of a fault, the control ability of low capacity pwm converter to double-fed wind power generator is also restricted, and causes the failure operation ability of double-fed wind power generator to reduce.

When line voltage rapid drawdown, Study on direct torque control technology is applied in double-fed wind power generator, this strategy directly controls the torque of motor, although control method is simple, decrease the application of the parameter of electric machine, but also there is certain problem in direct torque control: the switching frequency of power inverter changes with the ring width change of hysteresis comparator, and can distort by generation current, during low speed, torque pulsation is comparatively large, thus impact exports the quality of electric energy.Some document proposes the direct Power Control of motor in addition, this control strategy employs hysteresis comparator equally, make rotor converter switching frequency along with active power and reactive power change, the switching frequency of this change needs complicated and expensive power converter and AC harmonic filter.Also have part document that space vector technique is incorporated into direct Power Control method, but the method needs comparatively complicated Coordinate Conversion, control precision is not high.When line voltage occur single-phase fall 60% or three-phase symmetrical fall 60% fault time, current most of control method is difficult to control within 2 times of its rated current to rotor current between age at failure, and electromagnetic torque fluctuation is larger, very large to the impulsive force of unit.The response speed of control system and the control precision of controller directly affect the inhibition of fault current.Therefore need to propose a kind of control method solved the problem, i.e. fault control method under two-phase rest frame.This control has fault rapid dynamic response speed, and control precision is high, effectively can avoid the saturation problem of controller under electric network fault large disturbances.Not only can control rotor fault electric current within 1.5-1.6 times of rated current, and between age at failure, electromagnetic torque pulsation is less, effectively can improves double-fed wind power generator not off-grid serviceability under line voltage fault.

Summary of the invention

The present invention is directed to the deficiencies in the prior art, double-fed wind power generator fault control method under two-phase rest frame when providing a kind of grid voltage sags, this control method has rapid dynamic response speed, control precision is high, not only can control rotor fault electric current within 1.5-1.6 times of rated current, and electromagnetic torque pulsation is less between age at failure, reduce the impact to generating set, effectively can improve double-fed wind power generator not off-grid serviceability under line voltage fault.

When line voltage normally runs, double-fed wind power generator rotor side converter adopts based on stator magnetic linkage oriented vector control, adopts fault control method during line voltage rapid drawdown.The control frequency simultaneously arranging fault control method is 2 times based on stator magnetic linkage oriented vector control, and its concrete implementation step is:

(1) the stator three-phase voltage, will detected u _{s abc} with stator three-phase current i _{s abc} stator two phase voltage under Coordinate Conversion obtains reference stator two-phase rest frame u _{s α β} with stator biphase current i _{s α β} ;

(2) stator magnetic linkage space bit angle setting, is calculated θ ₁, by the rotor three-phase electric current detected i _{r abc} reference stator two-phase rest frame lower rotor part biphase current is obtained through Coordinate Conversion i _{r α β} ;

(3) rotor speed, will recorded ω _rcarry out integral and calculating to obtain θ _r;

(4), by the stator biphase current under reference stator two-phase rest frame i _{s α} , i _{s β} , rotor biphase current i _{r α} , i _{r β} , stator self inductance l _s, rotor self-induction l _rand mutual inductance between rotor l _mcarry out stator magnetic linkage and rotor flux calculates stator magnetic linkage α , βaxle component Ψ _{s α} , Ψ _{s β} with rotor flux α , βaxle component Ψ _{r α} , Ψ _{r β} ;

(5), the set-point of rotor flux calculates, that is: Ψ _r ^*= mΨ _s, wherein , i _s ^rfor stator current rated value, Ψ _s ^rfor stator magnetic linkage actual value, subscript r represents with rotor speed ω _rtwo phase coordinate systems rotated, subscript s represents the variable of stator side, between age at failure mwith Ψ _s ^rtranslating self-adapting change, realize the real-time optimistic control to rotor flux, by obtain with rotor speed ω _rthe rotor flux reference value of rotor flux reference value under Coordinate Conversion obtains reference stator two-phase rest frame under the two-phase rotor coordinate rotated;

(6), the formula of double-fed wind power generator rotor voltage under reference stator two-phase rest frame is: , , in formula: u _{r α} with u _{r β} represent rotor voltage respectively αaxle and βaxle component, r _rfor rotor resistance;

(7), suppose that the sampling period is t _s, by double-fed wind power generator rotor voltage formula discretely to obtain: , rotor flux track with zero error target makes rotor flux reach set-point in the k+1 moment, i.e. Ψ in formula _{r α} (k+1), Ψ _{r β} (k+1) rotor flux is respectively α, βaxle is at the set-point Ψ in k+1 moment _{r α} ^*(k+1), Ψ _{r β} ^*(k+1);

(8), can be obtained through distortion by double-fed wind power generator rotor voltage dispersion formula in step (7): , obtain from formula u _{r α} (k), u _{r β} k (), will u _{r α} (k), u _{r β} k () rotor voltage under coordinate transform obtains two-phase rotor reference coordinate system, then carries out PWM.

When line voltage occur single-phase fall 60% or three-phase symmetrical fall 60% fault time, current most of control method is in its rated current about 2 times of rotor current general control between age at failure, and electromagnetic torque fluctuation is larger, very large to the impulsive force of unit.During grid collapses, parameter of the present invention mcan adaptively changing, this controller realizes real-time estimate to rotor flux and optimal control, avoids the saturation problem of controller under the extreme disturbance of electric network fault.2 times when this process middle controller raising control frequency is normal, shorten the response time to fault, all variablees are based on reference stator two-phase rest frame simultaneously, without the need to the coordinate transform of complexity, fast and effeciently can control rotor current within 1.5-1.6 times of rated current at instant of failure, electromagnetic torque fluctuation is also less.

Accompanying drawing explanation

Fig. 1 is two-phase reference stator α βrest frame, two-phase rotor speed ω _rrotate α _r β _rcoordinate system, two same pace ω _erotate dqcoordinate system;

Fig. 2 is control structure block diagram;

Fig. 3 is the operation result figure of line voltage generation three-phase symmetrical Fault Control when falling 60% fault;

Fig. 4 is the operation result figure that single-phase Fault Control when falling 60% fault occurs line voltage.

specific implementation method

Below in conjunction with accompanying drawing, the present invention will be further described.Fig. 1 is two-phase stator α βrest frame, two-phase rotor speed ω _rrotate α _r β _rcoordinate system, two same pace ω _erotate dqcoordinate system.Control method of the present invention, based on reference stator two-phase rest frame, by the stator current that collects and rotor current, through Coordinate Conversion, obtains the variable under reference stator two-phase rest frame.

The fundamental voltage equation of double-fed generator under reference stator two-phase rest frame is:

（1）

（2）

In formula: u _{r α} with u _{r β} represent rotor voltage respectively αaxle and βaxle component; i _{r α} with i _{r β} represent rotor current respectively αaxle and βaxle component; Ψ _{r α} and Ψ _{r β} represent rotor flux respectively αaxle and βaxle component; ω _rfor generator amature angular speed; r _rfor rotor resistance.

Under reference stator two-phase rest frame, rotor flux equation can be expressed as:

Ψ _{r α} = L _m i _{s α} + L _r i _{r α} （3）

Ψ _{r β} = L _m i _{s β} + L _r i _{r β} （4）

In formula: i _{s α} with i _{s β} represent stator current respectively αaxle and βaxle component; l _s, l _rwith l _mrepresent the mutual inductance between stator self inductance, rotor self-induction and rotor respectively.

Discretization is carried out to formula (1), (2), can obtain:

（5）

（6）

In formula: t _s for the sampling period.This control objectives makes rotor flux reach set-point in the k+1 moment, namely in formula, and Ψ _{r α} (k+1), Ψ _{r β} (k+1) the set-point Ψ of rotor flux α, β axle in the k+1 moment is respectively _{r α} ^*(k+1), Ψ _{r β} ^*(k+1).So can following formula be obtained:

（7）

（8）

Formula (7), (8) are double-fed wind power generator Fault Control model.

Two-phase rotor speed ω _runder the coordinate system rotated, stators and rotators flux linkage equations can be expressed as:

Ψ _s ^r= L _s I _s ^r+ L _m I _r ^r（9）

Ψ _r ^r= L _r I _r ^r+ L _m I _s ^r（10）

Wherein i _swith i _rrepresent stator current and rotor current respectively, Ψ _sand Ψ _rrepresent stator magnetic linkage and rotor flux, subscript r represents with rotor speed ω _rrotate two phase coordinate systems, subscript s and r represents variable and the rotor-side variable of stator side respectively.

Can be obtained by formula (9) and formula (10):

（11）

Rotor current can be obtained, in computational process by formula (9) and formula (10) , by the set-point Ψ of rotor flux _r ^*= mΨ _ssubstitution can obtain:

（12）

In formula l _ls, l _lrrepresent stator leakage inductance and rotor leakage inductance respectively.

By the set-point Ψ of rotor flux _r ^*= mΨ _ssubstitution formula (11) can obtain:

（13）

i _s ^rfor the rated value of stator current, Ψ _s ^rfor the actual value of stator magnetic linkage.By the relation of rotor magnetic linkage and stator and rotor current, and rotor flux field weakening control method, obtain mvalue size, between age at failure mcan with Ψ _s ^rtranslating self-adapting changes, and realizes the real-time optimistic control to rotor flux.Instant of failure Ψ _s ^rvalue maximum, now mget maximum, formula (12) can be found out, mlarger, rotor fault current value is less, and therefore can realize instant of failure and effectively control rotor current, instant of failure is particularly important to the control of rotor overcurrent.Double-fed aerogenerator stator side is directly connected with electrical network, and the distortion of stator side electric current is very large to electrical network harm, therefore between age at failure i _s ^rget rated value, to realize the adjustment to stator current between age at failure, control stator current within its maximum current allowed.Finally by obtain with rotor speed ω _rrotor flux reference value under the two-phase rotor coordinate rotated, through Coordinate Conversion, obtains the rotor flux reference value under reference stator two-phase rest frame.

Double-fed wind power generator fault control method under two-phase rest frame, compared with vector control method, it has rapid dynamic response speed, and control precision is high, and without features such as overshoots in failure process, and it is saturated to eliminate compared with controller under large disturbances.Not only can control rotor fault electric current within 1.5-1.6 times of rated current, and between age at failure, electromagnetic torque pulsation is less, reduces the impact to generating set, effectively can improves double-fed wind power generator not off-grid serviceability under line voltage fault.

Fig. 2 is Fault Control structured flowchart of the present invention.When line voltage steady operation, rotor-side converter carries out based on stator magnetic linkage oriented vector control method, the double-fed wind power generator fault control method when line voltage falls.Under two-phase rest frame, the step of fault control method is as follows: (1), the stator three-phase voltage that will detect u _{s abc} with stator three-phase current i _{s abc} stator two phase voltage under Coordinate Conversion obtains reference stator two-phase rest frame u _{s α β} with stator biphase current i _{s α β} ; (2) stator magnetic linkage space bit angle setting, is calculated θ ₁, by the rotor three-phase electric current detected i _{r abc} reference stator two-phase rest frame lower rotor part biphase current is obtained through Coordinate Conversion i _{r α β} ; (3) rotor speed, will recorded ω _rcarry out integral and calculating to obtain θ _r; (4), by the stator biphase current under reference stator two-phase rest frame i _{s α} , i _{s β} , rotor biphase current i _{r α} , i _{r β} , stator self inductance l _s, rotor self-induction l _rand mutual inductance between rotor l _mcarry out stator magnetic linkage and rotor flux calculates stator magnetic linkage α , βaxle component Ψ _{s α} , Ψ _{s β} with rotor flux α , βaxle component Ψ _{r α} , Ψ _{r β} ; (5), the set-point of rotor flux calculates, that is: Ψ _r ^*= mΨ _s, wherein , i _s ^rfor stator current rated value, Ψ _s ^rfor stator magnetic linkage actual value, subscript r represents with rotor speed ω _rtwo phase coordinate systems rotated, subscript s represents the variable of stator side, between age at failure mwith Ψ _s ^rtranslating self-adapting change, realize the real-time optimistic control to rotor flux, by obtain with rotor speed ω _rthe rotor flux reference value of rotor flux reference value under Coordinate Conversion obtains reference stator two-phase rest frame under the two-phase rotor coordinate rotated; (6), the formula of double-fed wind power generator rotor voltage under reference stator two-phase rest frame is: , , in formula: u _{r α} with u _{r β} represent rotor voltage respectively αaxle and βaxle component, r _rfor rotor resistance; (7), suppose that the sampling period is t _s, by double-fed wind power generator rotor voltage formula discretely to obtain: , rotor flux track with zero error target makes rotor flux reach set-point in the k+1 moment, i.e. Ψ in formula _{r α} (k+1), Ψ _{r β} (k+1) rotor flux is respectively α, βaxle is at the set-point Ψ in k+1 moment _{r α} ^*(k+1), Ψ _{r β} ^*(k+1); (8), can be obtained through distortion by double-fed wind power generator rotor voltage dispersion formula in step (7): , obtain from formula u _{r α} (k), u _{r β} k (), will u _{r α} (k), u _{r β} k () rotor voltage under coordinate transform obtains two-phase rotor reference coordinate system, then carries out PWM.

Fig. 3 is the operation result figure of line voltage generation three-phase symmetrical when falling 60% fault, as can be seen from the figure, electromagnetic torque is almost nil, fluctuate less, when power grid operation, rotor current is 2000A, when voltage falls, employing failure operation controls, and now rotor current is 3000A, and rotor current controls within 1.5 times of peak current ratings.

Fig. 4 is that single-phase operation result figure when falling 60% fault occurs line voltage, as can be seen from the figure, electromagnetic torque is almost nil, fluctuate less, when power grid operation, rotor current is 2000A, when grid voltage sags, employing failure operation controls, and now rotor current is 3200A, and rotor current controls within 1.6 times of peak current ratings.

Embodiment above describes general principle of the present invention, principal character and advantage; the technical staff of the industry should understand; the present invention is not restricted to the described embodiments; what describe in above-described embodiment and specification just illustrates principle of the present invention; under the scope not departing from the principle of the invention; the present invention also has various changes and modifications, and these changes and improvements all fall in the scope of protection of the invention.

Claims (1)

1. double-fed wind power generator fault control method under two-phase rest frame, it is characterized in that: when line voltage normally runs, double-fed wind power generator rotor side converter adopts based on stator magnetic linkage oriented vector control, fault control method is adopted during line voltage rapid drawdown, the control frequency simultaneously arranging fault control method is 2 times based on stator magnetic linkage oriented vector control, and its concrete implementation step is:

(1) the stator three-phase voltage, will detected u _{s abc} with stator three-phase current i _{s abc} stator two phase voltage under Coordinate Conversion obtains reference stator two-phase rest frame u _{s α β} with stator biphase current i _{s α β} ;

(2) stator magnetic linkage space bit angle setting, is calculated θ ₁, by the rotor three-phase electric current detected i _{r abc} reference stator two-phase rest frame lower rotor part biphase current is obtained through Coordinate Conversion i _{r α β} ;

(3) rotor speed, will recorded ω _rcarry out integral and calculating to obtain θ _r;

(4), by the stator biphase current under reference stator two-phase rest frame i _{s α} , i _{s β} , rotor biphase current i _{r α} , i _{r β} , stator self inductance l _s, rotor self-induction l _rand mutual inductance between rotor l _mcarry out stator magnetic linkage and rotor flux calculates stator magnetic linkage α , βaxle component Ψ _{s α} , Ψ _{s β} with rotor flux α , βaxle component Ψ _{r α} , Ψ _{r β} ;

(5), the set-point of rotor flux calculates, that is: Ψ _r ^*= mΨ _s, wherein , i _s ^rfor stator current rated value, Ψ _s ^rfor stator magnetic linkage actual value, subscript r represents with rotor speed ω _rtwo phase coordinate systems rotated, subscript s represents the variable of stator side, between age at failure mwith Ψ _s ^rtranslating self-adapting change, realize the real-time optimistic control to rotor flux, by obtain with rotor speed ω _rthe rotor flux reference value of rotor flux reference value under Coordinate Conversion obtains reference stator two-phase rest frame under the two-phase rotor coordinate rotated;

(6), the formula of double-fed wind power generator rotor voltage under reference stator two-phase rest frame is: , , in formula: u _{r α} with u _{r β} represent rotor voltage respectively αaxle and βaxle component, r _rfor rotor resistance;

(7), suppose that the sampling period is t _s, by double-fed wind power generator rotor voltage formula discretely to obtain: , rotor flux track with zero error target makes rotor flux reach set-point in the k+1 moment, i.e. Ψ in formula _{r α} (k+1), Ψ _{r β} (k+1) rotor flux is respectively α, βaxle is at the set-point Ψ in k+1 moment _{r α} ^*(k+1), Ψ _{r β} ^*(k+1);

(8), can be obtained through distortion by double-fed wind power generator rotor voltage dispersion formula in step (7): , obtain from formula u _{r α} (k), u _{r β} k (), will u _{r α} (k), u _{r β} k () rotor voltage under coordinate transform obtains two-phase rotor reference coordinate system, then carries out PWM.