CN104184168A - Method for allowing permanent magnetic direct drive wind power generation system to participate in frequency adjustment of power grid on basis of fuzzy control - Google Patents

Abstract

The invention discloses a method for allowing a permanent magnetic direct drive wind power generation system to participate in frequency adjustment of a power grid on the basis of fuzzy control. A permanent magnetic direct drive wind power unit can change frequency adjustment power output by the permanent magnetic direct drive wind power unit according to real-time frequency of the power grid through coordination control over a motor side convertor, a power grid side convertor and a flywheel energy storage unit side convertor. The method has the advantages that maximum wind power tracking control can be achieved while auxiliary frequency adjustment power is provided for the power grid; control parameters of the power grid can be flexibly changed under all working conditions according to power grid frequency conditions, equivalent inertia and damping of the system can be dynamically adjusted, and the permanent magnetic direct drive wind power unit can participate in frequency adjustment of the power grid to the maximum degree.

Description

A kind of permanent magnet direct-drive wind generator system based on fuzzy control participates in mains frequency control method

Technical field

The present invention relates to wind generating technology, particularly relate to a kind of permanent magnet direct-drive wind generator system based on fuzzy control and participate in mains frequency control method, belong to power control technology field.

Background technology

In permanent magnet direct-drive wind generator system, wind turbine rotating shaft is directly connected with multistage low speed brushless permanent magnet synchronous generator, has saved change gear box, brush and slip ring, so failure rate of machinery is lower, and operation stability and the reliability of generator significantly strengthen.Meanwhile, the permanent-magnet synchronous electricity generation system based on two pwm converters can realize variable speed constant frequency generator operation and meritorious idle independent control, and generating efficiency is high, and structure is comparatively simple, good operation stability.In addition, fuzzy control technology, with its good interference free performance, robustness and without the accurate model of controlled device, has been applied to wind generator system.Because wind energy is the unstable energy, wind speed has uncontrollability, the accurate characteristic such as expection property and random fluctuation, and wind generator system active power of output is fluctuateed with the variation of wind speed.Increase along with wind-powered electricity generation capacity proportion in electrical network, the fluctuation of extensive grid connected wind power power will make a significant impact the frequency characteristic of electrical network, cause mains frequency stability decreases, the problems such as frequency fluctuation increase and frequency fluctuation increase recovery time, this can worsen the operation characteristic of electrical network undoubtedly, the system that increases electric power operation and the difficulty of controlling.For improving the quality of power supply of wind-powered electricity generation access electrical network, wish that wind-powered electricity generation unit can participate in system frequency and regulate under full operating mode.At present, for the power system frequency regulation technology containing wind-powered electricity generation, Chinese scholars has been carried out correlative study work.As published following document:

(1) Li Licheng, Ye Lin. become permanent magnetism direct drive wind group of motors frequency-rotating speed coordination control strategy under wind speed, Automation of Electric Systems, 2011,35 (17): 26-31.

(2)Juan?M?M,Alejandro?M,Antonio?G.Frequency?regulation?contribution?through?variable?speed?wind?energy?conversion?systems.IEEE?Transaction?on?Power?Systems,2008,24(1):173-181.

(3) Sun Chunshun, Wang Yaonan, Li Xinran. the wind generator system power that flywheel is auxiliary and frequency synthesis are controlled. Proceedings of the CSEE, 2008,28 (29): 111-116.

Document (1), document (2) utilize the stored kinetic energy of wind generator system large rotating inertia as the required active power of frequency modulation source.But due to the restriction of wind-powered electricity generation generating unit speed, the method does not possess under full operating mode provides fm capacity; And because the method causes the frequent acceleration and deceleration of rotor, reduced wind energy utilization and increased unit stress.

Document (3) is applied to wind-powered electricity generation unit by flywheel energy storage system and controls with assisting wind generating unit frequency adjustment, has improved to a great extent the frequency regulation capability of wind power system.But due to the uncertainty of wind speed, the method is difficult to the frequency adjustment command signal that Obtaining Accurate calculates by wind speed, thereby limit its application in real system.

In engineering practice, consider the many factors that frequency fluctuation produces, and electrical network Mathematical Modeling is uncertain.Therefore, in the urgent need to a kind of new wind-powered electricity generation unit quenching frequency control mode, can dynamically adjust according to mains frequency state the frequency modulation power of its output, to improve the wind-powered electricity generation unit output quality of power supply, for strengthen electrical network dissolve large-scale wind power ability, improve be incorporated into the power networks characteristic and effectively utilize wind energy resources to have important practical significance of wind power system.

Summary of the invention

For prior art above shortcomings, the object of the present invention is to provide a kind of permanent magnet direct-drive wind generator system based on fuzzy control to participate in mains frequency control method.The frequency fluctuation of this method whole system can be effectively suppressed, and is accelerated the recovery time after frequency fluctuation generation, improves the fm capacity of wind power system under full operating mode.

Technical scheme of the present invention is achieved in that

A kind of permanent magnet direct-drive wind generator system based on fuzzy control participates in mains frequency control method, this method relates to the control to the control of the control of motor side converter, grid side converter and flywheel energy storage unit side converter, and the control strategy of each converter is respectively:

A) control strategy of motor side converter is:

Motor side converter using vector control strategy, it controls voltage and DC-link voltage u _dcby space vector modulation, produce motor side converter PWM and drive signal;

B) control strategy of grid side converter is:

Grid side converter using vector control strategy, it controls voltage and DC-link voltage u _dcby space vector modulation, produce grid side converter PWM and drive signal;

C) control strategy of flywheel energy storage unit side converter carries out as follows:

C1) gather the threephase stator current i of fly-wheel motor _fa, i _fb, i _fc;

C2) detect fly-wheel motor rotor mechanical angle with mechanical separator speed ω _f, according to and ω _fcalculate fly-wheel motor rotor electric angle speed p _fω _fand rotor electrical degree θ _f, p _ffor fly-wheel motor number of pole-pairs;

C3) utilize step C1) the threephase stator current i that gathers _fa, i _fb, i _fcin conjunction with rotor electrical degree θ _fcarry out the permanent power coordinate transform from the static three-phase abc system of axis to the two-phase synchronous rotary dq system of axis, obtain the current signal i under the two-phase synchronous rotary dq system of axis _fdand i _fq;

C4) gather three phase network voltage signal e _ga, e _gb, e _gc; And obtain electrical network real-time frequency f through digital phase-locked loop PLL;

C5) calculate the rate of change ec of mains frequency deviation e and mains frequency deviation, the computing formula of e and ec is as follows:

e＝f ^*-f

$\mathrm{ec}=\frac{d(f^{*}-f)}{\mathrm{dt}}$

Wherein: f ^*for mains frequency is given, China's regulation is 50Hz;

C6) e and ec are quantified as respectively to 13 grades, 6 ,-5 ,-4 ,-3 ,-2 ,-1,0,1,2,3,4,5,6};

C7) input using e and ec as fuzzy controller, its fuzzy set represents with seven vocabulary, NB, and NM, NS, ZS, PS, PM, PB}, the membership function of input variable e and ec is selected Triangleshape grade of membership function; , according to the grade of e and ec, by membership function, calculate the degree of membership that it belongs to each fuzzy set vocabulary, according to maximum subjection principle, can judge the fuzzy set vocabulary that e and ec belong to;

C8) fly-wheel motor is controlled to parameter K _pfand K _dfas the output of fuzzy controller, wherein, K _pfbe quantified as 11 grades, 5 ,-4 ,-3 ,-2 ,-1,0,1,2,3,4,5}, K _dfbe quantified as 6 grades, i.e. { 0,1,2,3,4,5}, and K _pfand K _dffuzzy set still with seven vocabulary, represent, i.e. { NB, NM, NS, ZS, PS, PM, PB}, output variable K _pfand K _dfmembership function select Gaussian membership function; According to K _pfand K _dfgrade, by membership function, calculate the degree of membership that it belongs to each fuzzy set vocabulary, according to maximum subjection principle, can judge K _pfand K _dfthe fuzzy set vocabulary belonging to;

C9) according to fuzzy rule, e and ec are judged and obtain the fuzzy set vocabulary that it belongs to, by fuzzy logic, judge the corresponding number of output K _pfand K _dfthe fuzzy set vocabulary belonging to, wherein generates number K _pffuzzy logic be:

Generate K _dffuzzy logic be:

C10) to K _pfand K _dfcarry out defuzzification, its defuzzification method is chosen as gravity model appoach, and defuzzification formula is:

$\left\{\begin{array}{c}{K}_{\mathrm{pf}}=\frac{{\∫}_S{K}_{\mathrm{pf}}{\mathrm{\μ}}_{\mathrm{Kpf}}\left(K_{\mathrm{pf}}\right)d{K}_{\mathrm{pf}}}{{\∫}_S{\mathrm{\μ}}_{\mathrm{Kpf}}\left(K_{\mathrm{pf}}\right)d{K}_{\mathrm{pf}}}\\ K_{\mathrm{df}}=\frac{{\∫}_S{K}_{\mathrm{df}}{\mathrm{\μ}}_{\mathrm{Kdf}}\left(K_{\mathrm{df}}\right)d{K}_{\mathrm{df}}}{{\∫}_S{\mathrm{\μ}}_{\mathrm{Kdf}}\left(K_{\mathrm{df}}\right)d{K}_{\mathrm{df}}}\end{array}\right.$

In formula: μ _kpfand μ _kdfbe respectively K _pfand K _dfdegree of membership;

C11) according to step C10) gained K _pfand K _dfand step C4) to calculate fly-wheel motor dq shaft current given for gained electrical network real-time frequency f, and the given computing formula of fly-wheel motor q shaft current is:

△ f=f wherein ^*-f is mains frequency deviation e; ;

The given computing formula of fly-wheel motor d shaft current is:

$i_{\mathrm{fd}}^{*}=0$

C12) adopt rotor field-oriented vector control mode, given according to d, q shaft current with step C3) d, the q axle actual current i of permanent power conversion gained _fd, i _fq, by cross-coupling control mode, obtain d, q axle control voltage u _fdand u _fq, governing equation is:

$\left\{\begin{array}{c}{u}_{\mathrm{fd}}=[K_{p5}({\mathrm{\τ}}_{i5}s+1)/{\mathrm{\τ}}_{i5}s](i_{\mathrm{fd}}^{*}-i_{\mathrm{fd}})-p_f{\mathrm{\ω}}_f{L}_{\mathrm{fq}}{i}_{\mathrm{fq}}\\ u_{\mathrm{fq}}=[K_{p6}({\mathrm{\τ}}_{i6}s+1)/{\mathrm{\τ}}_{i6}s](i_{\mathrm{fq}}^{*}-i_{\mathrm{fq}})+p_f{\mathrm{\ω}}_f{L}_{\mathrm{fd}}{i}_{\mathrm{fd}}+{\mathrm{\ω}}_f{\mathrm{\ψ}}_f\end{array}\right.$

Wherein: K _p5, τ _i5, K _p6, τ _i6be respectively the PI output of stator d, q shaft current; L _fd, L _fqbe respectively stator d, q axle inductance; ψ _ffor rotor permanent magnet magnetic linkage; S is the independent variable of complex frequency domain F (s), is called " complex frequency ";

C13) by step C12) the control voltage u of fly-wheel motor under the gained two-phase synchronous rotary dq system of axis _fd, u _fqwith current signal i _fd, i _fqcalculate fly-wheel motor active power of output P _f:

P _f＝u _fdi _fd+u _fqi _fq

C14) by controlling voltage u _fd, u _fq, and in conjunction with rotor electrical degree θ _fwith DC-link voltage u _dcthe PWM that obtains flywheel energy storage unit side converter through space vector modulation SVM drives signal to control motor;

C15) when motor accelerates to maximum speed, the outer shroud mode of operation of switch motor, switches to rotating speed/current closed-loop control model by power/current closed loop control mode, and rotational speed setup is fly-wheel motor rated speed; When this process continues to fly-wheel motor acquisition reduce-speed sign, again switch to power/current closed loop control mode;

C16) when fly-wheel motor is decelerated to zero continuously, rotating speed outer shroud set-point is set as to zero, controlling motor speed is zero, adopt the control of rotating speed/current closed-loop to realize fly-wheel motor moves under zero-speed, until require fly-wheel motor to reenter acceleration mode, switch to power/current closed loop control mode.

Compared to existing technology, the present invention has following beneficial effect:

1. the present invention, under the requirement of system frequency modulation control, has also realized maximal wind-energy and has followed the tracks of control.When wind speed and system loading variation, flywheel energy storage unit adds/runs slowly according to system frequency modulation demand.Fly-wheel motor stator current q axle component changes between driving/braking state according to the regulation output of power ring, when fly-wheel motor moves with driving condition, absorbs the surplus power of generator output; Otherwise, when drive motors moves with on-position, to grid side converter output supplemental capacity, flywheel deceleration releases energy, thereby whole system frequency fluctuation is effectively suppressed, and accelerated the recovery time after frequency fluctuation occurs, improved to a certain extent the also network electric energy quality of wind power system.

2. by fuzzy control technology, flywheel energy storage unit side converter is controlled parameter, dynamic adjusting system equivalent inertia and damping according to mains frequency situation choose reasonable.Thereby when frequency worsens, increase system equivalent inertia and damping and shorten the frequency departure time, thereby when frequency retrieval, reduce system equivalent inertia and damping and improve frequency retrieval speed, strengthen system suitability, further improve the fm capacity of wind power system under full operating mode.

In a word, this method is by controlling the coordination of motor side converter, grid side converter and flywheel energy storage unit side converter, and by rationally applying fuzzy control technology, make wind-powered electricity generation unit under full operating mode, obtain comparatively stable fm capacity, improve the grid-connected adaptability of wind power system.

Accompanying drawing explanation

Fig. 1 is the permanent magnet direct-drive wind generator system figure containing flywheel energy storage unit;

Fig. 2 is the control block diagram of total system;

Fig. 3 is that flywheel drive motors q axle is controlled calculation of parameter control chart;

Fig. 4 is the given control chart of flywheel drive motors q shaft current;

Fig. 5 is impact anticlimax load simulation waveform figure under high wind speed section.

Fig. 6 is rated wind speed impact anticlimax load simulation waveform figure when above.

Embodiment

Below in conjunction with accompanying drawing, specific embodiment of the invention scheme is described in detail.

Referring to Fig. 1 and Fig. 2, permanent magnet direct-drive wind generator system of the present invention participates in the method that mains frequency regulates, its referent mainly contains: voltage hall sensor 1, current Hall transducer 2, rotor-position sensor 3, abc/dq coordinate transformation module 4, space vector modulation device 5, abc/ α β coordinate transformation module 6, α β/dq coordinate transformation module 7, mains frequency detection module 8, synchronous permanent-magnet motor/generator 9, energy-storage units is controlled the given module 10 of parameter, the given module 11 of synchronous permanent-magnet motor/generator q shaft current, energy-storage units current inner loop control module 12, energy-storage units side converter 13.

Permanent magnet direct-drive wind generator system of the present invention participates in mains frequency control method and relates to the control to the control of the control of motor side converter, grid side converter and flywheel energy storage unit side converter, and the control strategy of each converter is respectively (can simultaneously referring to Fig. 2):

A) control strategy of motor side converter is:

Motor side converter using vector control strategy, it controls voltage and DC-link voltage u _dcby space vector modulation, produce motor side converter PWM and drive signal;

B) control strategy of grid side converter is:

Grid side converter using vector control strategy, it controls voltage and DC-link voltage u _dcby space vector modulation, produce grid side converter PWM and drive signal;

C) control of flywheel energy storage unit side converter, its control step is:

C1) utilize current Hall transducer 2 to gather the stator current signal i of permanent-magnet synchronous generator/motor 9 (fly-wheel motors) _fa, i _fb, i _fc;

C2) utilize rotor-position sensor 3 to detect the mechanical angle of permanent-magnet synchronous generator/motor 9 and mechanical separator speed ω _f, according to and ω _fcalculate permanent-magnetic synchronous motor rotor electric angle speed p _fω _fand rotor electrical degree p _ffor permanent-magnet synchronous flywheel drive motors number of pole-pairs;

C3) utilize step C1) the threephase stator current i that gathers _fa, i _fb, i _fcwith rotor electrical degree θ _f, by abc/dq coordinate transformation module 4, realize coordinate transform, realize the permanent power coordinate transform from the static three-phase abc system of axis to the two-phase synchronous rotary dq system of axis, obtain the current signal i under the two-phase synchronous rotary dq system of axis _fdand i _fq;

C4) gather three phase network voltage signal e _ga, e _gb, e _gc; And obtain electrical network real-time frequency f through digital phase-locked loop PLL; Its solution procedure is: utilize voltage hall sensor 1 to measure three phase network voltage signal e _ga, e _gb, e _gc, by abc/ α β coordinate transformation module 6, to the static two-phase α β system of axis, adopt permanent power conversion to obtain the voltage e under the α β system of axis static three-phase abc coordinate system transformation _α, e _β; By α β/dq coordinate transformation module 7, obtain the line voltage d axle component e under line voltage orientation again _gdwith electrical network electrical degree θ _g; Finally by overfrequency detection module 8, obtain electrical network real-time frequency signal f.

C5) the mains frequency f that utilizes step C4 to obtain, controls parameter calculating module 10 by energy-storage units, obtains energy-storage units and controls parameter K _pfand K _df, simultaneously can be referring to Fig. 3;

Energy-storage units of the present invention is controlled parameter calculating module 10, and concrete implementation step is as follows:

C5.1) calculate the rate of change ec of mains frequency deviation e and mains frequency deviation, the computing formula of e and ec is as follows:

e＝f ^*-f

$\mathrm{ec}=\frac{d(f^{*}-f)}{\mathrm{dt}}$

Wherein: f ^*for mains frequency is given, China's regulation is 50Hz;

C5.2) e and ec are quantified as respectively to 13 grades, 6 ,-5 ,-4 ,-3 ,-2 ,-1,0,1,2,3,4,5,6};

C5.3) input using e and ec as fuzzy controller, its fuzzy set represents with seven vocabulary, NB, and NM, NS, ZS, PS, PM, PB}, the membership function of input variable e and ec is selected Triangleshape grade of membership function; , according to the grade of e and ec, by membership function, calculate the degree of membership that it belongs to each fuzzy set vocabulary, by maximum subjection principle, can judge the fuzzy set vocabulary that e and ec belong to;

C5.4) fly-wheel motor is controlled to parameter K _pfand K _dfas fuzzy controller output, wherein, K _pfbe quantified as 11 grades, 5 ,-4 ,-3 ,-2 ,-1,0,1,2,3,4,5}, K _dfbe quantified as 6 grades, i.e. { 0,1,2,3,4,5}, and K _pfand K _dffuzzy set still with seven vocabulary, represent, i.e. { NB, NM, NS, ZS, PS, PM, PB}, output variable K _pfand K _dfmembership function select Gaussian membership function; According to K _pfand K _dfgrade, by membership function, calculate the degree of membership that it belongs to each fuzzy set vocabulary, according to maximum subjection principle, can judge K _pfand K _dfthe fuzzy set vocabulary belonging to;

C5.5) according to fuzzy rule, e and ec are judged and obtain the fuzzy set vocabulary that it belongs to, and judge the corresponding number of output K by fuzzy logic _pfand K _dfthe fuzzy set vocabulary belonging to, wherein generates number K _pffuzzy logic be:

Generate K _dffuzzy logic be:

C5.6) to K _pfand K _dfcarry out defuzzification, its defuzzification method is chosen as gravity model appoach, and defuzzification formula is:

$\left\{\begin{array}{c}{K}_{\mathrm{pf}}=\frac{{\∫}_S{K}_{\mathrm{pf}}{\mathrm{\μ}}_{\mathrm{Kpf}}\left(K_{\mathrm{pf}}\right)d{K}_{\mathrm{pf}}}{{\∫}_S{\mathrm{\μ}}_{\mathrm{Kpf}}\left(K_{\mathrm{pf}}\right)d{K}_{\mathrm{pf}}}\\ K_{\mathrm{df}}=\frac{{\∫}_S{K}_{\mathrm{df}}{\mathrm{\μ}}_{\mathrm{Kdf}}\left(K_{\mathrm{df}}\right)d{K}_{\mathrm{df}}}{{\∫}_S{\mathrm{\μ}}_{\mathrm{Kdf}}\left(K_{\mathrm{df}}\right)d{K}_{\mathrm{df}}}\end{array}\right.$

In formula: μ _kpfand μ _kdfbe respectively K _pfand K _dfdegree of membership.

C6) utilize step C5 gained K _pfand K _dfand step C4 gained f calculates fly-wheel motor d, q shaft current is given.

The given computing formula of fly-wheel motor d shaft current is:

$i_{\mathrm{fd}}^{*}=0$

With reference to Fig. 4, calculate fly-wheel motor q shaft current to regularly, according to rotating speed, choose different passages.Motor speed between rated speed time, is chosen passage 10, and the given computing formula of fly-wheel motor q shaft current is:

△ f+=f ^*-d is mains frequency deviation e;

Wherein: K _pffor the given calculating proportionality coefficient of fly-wheel motor q shaft current, K _dffor the given computing differential coefficient of fly-wheel motor q shaft current, for the q shaft current of fly-wheel motor given.

C7) adopt rotor field-oriented vector control mode, utilize energy-storage units current inner loop control module 12, by fly-wheel motor dq shaft current set-point with step C3) d, the q axle actual current i of permanent power conversion gained _fd, i _fq, adopt cross-coupling control mode to obtain d, q axle control voltage u _fdand u _fq, its governing equation is:

$\left\{\begin{array}{c}{u}_{\mathrm{fd}}=[K_{p5}({\mathrm{\τ}}_{i5}s+1)/{\mathrm{\τ}}_{i5}s](i_{\mathrm{fd}}^{*}-i_{\mathrm{fd}})-p_f{\mathrm{\ω}}_f{L}_{\mathrm{fq}}{i}_{\mathrm{fq}}\\ u_{\mathrm{fq}}=[K_{p6}({\mathrm{\τ}}_{i6}s+1)/{\mathrm{\τ}}_{i6}s](i_{\mathrm{fq}}^{*}-i_{\mathrm{fq}})+p_f{\mathrm{\ω}}_f{L}_{\mathrm{fd}}{i}_{\mathrm{fd}}+{\mathrm{\ω}}_f{\mathrm{\ψ}}_f\end{array}\right.$

Wherein: K _p5, τ _i5, K _p6, τ _i6be respectively the PI output of stator d, q shaft current; L _fd, L _fqbe respectively stator d, q axle inductance; ψ _ffor rotor permanent magnet magnetic linkage; In formula, s=σ+j ω is the independent variable of complex frequency domain F (s), is commonly referred to " complex frequency ", and wherein σ is real part, and ω is imaginary part.

C8) by controlling voltage u _fd, u _fqand current i _fd, i _fqcalculate fly-wheel motor active power of output P _f:

P _f＝u _fdi _fd+u _fqi _fq

C9) by controlling voltage u _fd, u _fq, and in conjunction with rotor electrical degree θ _fwith DC-link voltage u _dcthrough space vector modulation device 5, the PWM that obtains flywheel energy storage unit side converter 13 drives signal to control motor.

C10) according to the given module 11 of synchronous permanent-magnet motor/generator q shaft current, simultaneously referring to Fig. 4, when motor accelerates to maximum speed, the outer shroud mode of operation of switch motor, power/current closed loop control mode is switched to rotating speed/current closed-loop control model, passage 1 is switched to passage 2, and rotational speed setup is set as fly-wheel motor rated speed.When this process continues to fly-wheel motor acquisition reduce-speed sign, again switch back passage 1, i.e. power/current closed loop control mode.

C11) according to the given module 11 of synchronous permanent-magnet motor/generator q shaft current, simultaneously referring to Fig. 4, when fly-wheel motor is decelerated to zero continuously, rotating speed outer shroud set-point is set as to zero, and controlling motor speed is zero, adopts the control of rotating speed/current closed-loop to realize fly-wheel motor and moves under zero-speed, passage 1 is switched to passage 3, until require fly-wheel motor to reenter acceleration mode, switch back passage 1, i.e. power/current closed loop control mode.

The present invention is by the control to motor side converter, the coordination of the control of grid side converter and flywheel energy storage unit side converter is controlled, wind generator system is also realized maximal wind-energy and is followed the tracks of when auxiliary frequency modulation is provided to electrical network, and by rationally applying fuzzy control technology, flywheel energy storage unit converter can be controlled parameter according to mains frequency situation choose reasonable, calculating fly-wheel motor is meritorious, reactive current set-point, reach the object of regulating system equivalent inertia and damping, make wind-powered electricity generation unit under full operating mode, obtain comparatively stable fm capacity, change the grid-connected adaptability of wind power system.

Below in conjunction with Fig. 5 and Fig. 6, beneficial effect of the present invention is described:

1. the present invention can improve system response, and the resume speed after frequency fluctuation occurs is accelerated in the frequency fluctuation while reducing impact load.As shown in accompanying drawing 5 (a), (b) and accompanying drawing 6 (a), (b), under two kinds of different operating modes, adopt the system response while carrying control strategy all better.

2. according to mains frequency state, by fuzzy control technology choose reasonable energy-storage units, control parameter, send the frequency modulation power that meets system requirements, reduce frequency overshoot, as shown in Fig. 5 (b), (c) and Fig. 6 (b), (c).In frequency retrieval process, flywheel energy storage unit can be in good time from electrical network absorbability, the generation of blanketing frequency overshoot.

The above embodiment of the present invention is to be only explanation example of the present invention, and is not the restriction to embodiments of the present invention.For those of ordinary skill in the field, can also make on the basis of the above description other multi-form variation and changes.Here cannot give all execution modes exhaustive.Every still row in protection scope of the present invention of apparent variation that technical scheme of the present invention amplifies out or change that belong to.

Claims (2)

1. the permanent magnet direct-drive wind generator system based on fuzzy control participates in mains frequency control method, it is characterized in that, this method relates to the control to the control of the control of motor side converter, grid side converter and flywheel energy storage unit side converter, and the control strategy of each converter is respectively:

A) control strategy of motor side converter is:

Motor side converter using vector control strategy, it controls voltage and DC-link voltage u _dcby space vector modulation, produce motor side converter PWM and drive signal;

B) control strategy of grid side converter is:

Grid side converter using vector control strategy, it controls voltage and DC-link voltage u _dcby space vector modulation, produce grid side converter PWM and drive signal;

C) control strategy of flywheel energy storage unit side converter carries out as follows:

C1) gather the threephase stator current i of fly-wheel motor _fa, i _fb, i _fc;

C2) detect fly-wheel motor rotor mechanical angle with mechanical separator speed ω _f, according to and ω _fcalculate fly-wheel motor rotor electric angle speed p _fω _fand rotor electrical degree θ _f, p _ffor fly-wheel motor number of pole-pairs;

C3) utilize step C1) the threephase stator current i that gathers _fa, i _fb, i _fcin conjunction with rotor electrical degree θ _fcarry out the permanent power coordinate transform from the static three-phase abc system of axis to the two-phase synchronous rotary dq system of axis, obtain the current signal i under the two-phase synchronous rotary dq system of axis _fdand i _fq;

C4) gather three phase network voltage signal e _ga, e _gb, e _gc; And obtain electrical network real-time frequency f through digital phase-locked loop PLL;

C5) calculate the rate of change ec of mains frequency deviation e and mains frequency deviation, the computing formula of e and ec is as follows:

e＝f ^*-f

$\mathrm{ec}=\frac{d(f^{*}-f)}{\mathrm{dt}}$

Wherein: f ^*for mains frequency is given, China's regulation is 50Hz;

C6) e and ec are quantified as respectively to 13 grades, 6 ,-5 ,-4 ,-3 ,-2 ,-1,0,1,2,3,4,5,6};

C7) input using e and ec as fuzzy controller, its fuzzy set represents with seven vocabulary, NB, and NM, NS, ZS, PS, PM, PB}, the membership function of input variable e and ec is selected Triangleshape grade of membership function; , according to the grade of e and ec, by membership function, calculate the degree of membership that it belongs to each fuzzy set vocabulary, according to maximum subjection principle, can judge the fuzzy set vocabulary that e and ec belong to;

C8) fly-wheel motor is controlled to parameter K _pfand K _dfas the output of fuzzy controller, wherein, K _pfbe quantified as 11 grades, 5 ,-4 ,-3 ,-2 ,-1,0,1,2,3,4,5}, K _dfbe quantified as 6 grades, i.e. { 0,1,2,3,4,5}, and K _pfand K _dffuzzy set still with seven vocabulary, represent, i.e. { NB, NM, NS, ZS, PS, PM, PB}, output variable K _pfand K _dfmembership function select Gaussian membership function; According to K _pfand K _dfgrade, by membership function, calculate the degree of membership that it belongs to each fuzzy set vocabulary, according to maximum subjection principle, can judge K _pfand K _dfthe fuzzy set vocabulary belonging to;

C9) according to fuzzy rule, e and ec are judged and obtain the fuzzy set vocabulary that it belongs to, by fuzzy logic, judge the corresponding number of output K _pfand K _dfthe fuzzy set vocabulary belonging to, wherein generates number K _pffuzzy logic be:

Generate K _dffuzzy logic be:

C10) to K _pfand K _dfcarry out defuzzification, its defuzzification method is chosen as gravity model appoach, and defuzzification formula is:

$\left\{\begin{array}{c}{K}_{\mathrm{pf}}=\frac{{\∫}_S{K}_{\mathrm{pf}}{\mathrm{\μ}}_{\mathrm{Kpf}}\left(K_{\mathrm{pf}}\right)d{K}_{\mathrm{pf}}}{{\∫}_S{\mathrm{\μ}}_{\mathrm{Kpf}}\left(K_{\mathrm{pf}}\right)d{K}_{\mathrm{pf}}}\\ K_{\mathrm{df}}=\frac{{\∫}_S{K}_{\mathrm{df}}{\mathrm{\μ}}_{\mathrm{Kdf}}\left(K_{\mathrm{df}}\right)d{K}_{\mathrm{df}}}{{\∫}_S{\mathrm{\μ}}_{\mathrm{Kdf}}\left(K_{\mathrm{df}}\right)d{K}_{\mathrm{df}}}\end{array}\right.$

In formula: μ K _pfand μ _kdfbe respectively K _pfand K _dfdegree of membership;

C11) according to step C10) gained K _pfand K _dfand step C4) to calculate fly-wheel motor dq shaft current given for gained electrical network real-time frequency f, and the given computing formula of fly-wheel motor q shaft current is:

Δ f=f wherein ^*-f is mains frequency deviation e; ;

The given computing formula of fly-wheel motor d shaft current is:

$i_{\mathrm{fd}}^{*}=0$

C12) adopt rotor field-oriented vector control mode, given according to d, q shaft current with step C3) d, the q axle actual current i of permanent power conversion gained _fd, i _fq, by cross-coupling control mode, obtain d, q axle control voltage u _fdand u _fq, governing equation is:

$\left\{\begin{array}{c}{u}_{\mathrm{fd}}=[K_{p5}({\mathrm{\τ}}_{i5}s+1)/{\mathrm{\τ}}_{i5}s](i_{\mathrm{fd}}^{*}-i_{\mathrm{fd}})-p_f{\mathrm{\ω}}_f{L}_{\mathrm{fq}}{i}_{\mathrm{fq}}\\ u_{\mathrm{fq}}=[K_{p6}({\mathrm{\τ}}_{i6}s+1)/{\mathrm{\τ}}_{i6}s](i_{\mathrm{fq}}^{*}-i_{\mathrm{fq}})+p_f{\mathrm{\ω}}_f{L}_{\mathrm{fd}}{i}_{\mathrm{fd}}+{\mathrm{\ω}}_f{\mathrm{\ψ}}_f\end{array}\right.$

Wherein: K _p5, τ _i5, K _p6, τ _i6be respectively the PI output of stator d, q shaft current; L _fd, L _fqbe respectively stator d, q axle inductance; ψ _ffor rotor permanent magnet magnetic linkage; S is the independent variable of complex frequency domain F (s), is called " complex frequency ";

C13) by step C12) the control voltage u of fly-wheel motor under the gained two-phase synchronous rotary dq system of axis _fd, u _fqwith current signal i _fd, i _fqcalculate fly-wheel motor active power of output P _f:

P _f＝u _fdi _fd+u _fqi _fq

C14) by controlling voltage u _fd, u _fq, and in conjunction with rotor electrical degree θ _fwith DC-link voltage u _dcthe PWM that obtains flywheel energy storage unit side converter through space vector modulation SVM drives signal to control motor;

C15) when motor accelerates to maximum speed, the outer shroud mode of operation of switch motor, switches to rotating speed/current closed-loop control model by power/current closed loop control mode, and rotational speed setup is fly-wheel motor rated speed; When this process continues to fly-wheel motor acquisition reduce-speed sign, again switch to power/current closed loop control mode;

C16) when fly-wheel motor is decelerated to zero continuously, rotating speed outer shroud set-point is set as to zero, controlling motor speed is zero, adopt the control of rotating speed/current closed-loop to realize fly-wheel motor moves under zero-speed, until require fly-wheel motor to reenter acceleration mode, switch to power/current closed loop control mode.

2. the permanent magnet direct-drive wind generator system based on fuzzy control according to claim 1 participates in mains frequency control method, it is characterized in that described step C4) electrical network real-time frequency f solution procedure is: utilize voltage hall sensor to measure three phase network voltage signal e _ga, e _gb, e _gc, by abc/ α β coordinate transformation module, static three-phase abc coordinate system transformation is arrived to the static two-phase α β system of axis, adopt permanent power conversion to obtain the voltage e under the α β system of axis _α, e _β; By α β/dq coordinate transformation module, obtain the line voltage d axle component e under line voltage orientation again _gdwith electrical network electrical degree θ _g; Finally by overfrequency detection module, obtain electrical network real-time frequency signal f.