CN103259485A - Method of improving identification precision of speedless sensor under condition of unbalanced network voltage - Google Patents

Abstract

The invention relates to a method of improving identification precision of a speedless sensor under the condition of unbalanced network voltage. The method comprises the steps that a wind power generator controlled by a double-fed control system is adopted; when the network voltage is in a balanced state, stator voltage and stator current serve as an input of an MRAS (Model Reference Adaptive System) reference model directly; and rotating speed data is obtained after PI (Proportional-Integral) adaptive rotating speed estimation. An improvement of the method is that when the network voltage is in an unbalanced state, negative sequence components of the voltage and the current due to unbalance of the network voltage are removed from the input quantity of the MRAS reference model. The method has the technical benefits that the speedless sensor meets a control requirement that the power generator works in the slight unbalanced state of the network voltage; the identification precision of the speedless sensor on the rotating speed in the unbalanced state of the network voltage is improved; an application scope of the speedless sensor is expanded; and fault toleration control of the double-fed wind power generator during a fault of a speed sensor is achieved.

Description

Improve the method for Speedless sensor identification precision under the unbalanced source voltage condition

Technical field

The present invention relates to a kind of double-fed wind power generator control technology, relate in particular to a kind of method that under the unbalanced source voltage condition, improves the Speedless sensor identification precision.

Background technology

At present, double-fed wind power generator (DFIG) has become the mainstream model of MW class wind turbine group with the advantage of its variable speed constant frequency generator; In dual-feedback wind power generator control system, the rate signal of rotor is the important parameter of double-fed wind power generator vector control, in control system, play crucial effects, therefore, obtain accurate rotary speed data significant for double-fed wind power generator control.

In the prior art, the means that are used for obtaining generator speed generally have speed sensor such as optical code disk and tach signal are carried out two kinds of the Speedless sensors of online observation by account form; Based on high performance hardware preparation, no matter which kind of operating state generator is under the normal operation, speed sensor can both get access to rotary speed data comparatively accurately, but also just owing to the dependence of speed sensor to hardware device, cause having comprised in the generator cost cost of speed sensor, moreover, speed sensor also needs periodic maintenance, the fault of its hardware is inevitably with wearing out, so researchers have just turned one's attention to Speedless sensor; Speedless sensor has advantage simple in structure, with low cost because of it, more and more receives researchers' concern.At present, researchers just are being devoted to further to improve the accuracy of identification of Speedless sensor and the adaptability that generator is under the different running statuses, so that some day, make Speedless sensor can substitute speed sensor fully.Below just separately adopt the dual-feedback wind power generator control system of Speedless sensor to analyze;

In the actual electric power system, need the long-time running of wind power generation function under the slight non-equilibrium state of line voltage, and the energy short-time duty is under the situation that the unexpected generation of line voltage is seriously fallen; At present in the failure diagnosis and control design of transducer, all do not consider the reality (this is because unbalanced source voltage is less relatively to the influence that speed sensor causes) of unbalanced source voltage, and with respect to speed sensor, be more vulnerable to the influence of the negative sequence component in the unbalanced source voltage based on the Speed identification precision of the Speedless sensor of model reference adaptive system (MRAS).In the Speed identification based on MRAS, basic demand to reference model is exactly to want accurately, because reference model is the benchmark as MRAS control, have only this reference model accurate, Speedless sensor just can obtain more believable identifier, and in the prior art, owing to do not consider the reality of unbalanced source voltage, so the input variable of MRAS reference model is done special the processing, causes not only containing positive sequence component but also contain negative sequence component in the voltage, electric current input variable of MRAS reference model; In the actual motion, even less negative sequence voltage, current component all will cause the Speedless sensor based on MRAS that bigger error (this also is a major issue of can not ignore in the research of double-fed wind power generator Speedless sensor) is appearred in the tach signal online observation.If unbalanced source voltage, double-fed wind power generator adopts Speedless sensor to be difficult to obtain speed measured value accurately separately, the operation of whole unit will directly be influenced, when serious even can cause the instability of system, so, under unbalanced source voltage, double-fed wind power generator is in the Speed identification based on the MRAS Speedless sensor, how to avoid the Speed identification precision to be subjected to the influence of negative sequence voltage, current component even harmonic wave interference components, improve the identification precision of Speedless sensor, this is letter problem to be solved in the Speedless sensor research.

Summary of the invention

When the electric power system asymmetric operation, according to instantaneous symmetrical component theory, can be decomposed into positive sequence, negative phase-sequence and zero-sequence component sum.Consider that current double-fed wind power generator industry unit all adopts three-phase three-wire system system and big electrical network to link, namely therefore no zero-sequence component path in the Circuits System can ignore the existence of zero-sequence component.Because the negative phase-sequence air-gap rotating magnetic field that negative-sequence current produces is opposite with the rotor direction of rotation, induces two times of power currents in the magnetic pole winding of generator, i.e. so-called frequency multiplication electric current; The magnetic field that these two times of power currents produce induces three times of power currents again in stator winding, so interact, so in the rotor winding, there are a series of even-order harmonics (2,4,6 ...) electric current, in stator winding, there are a series of odd harmonics (3,5,7 ...) electric current, make the harmonic component of electric current in the electric power system, voltage increase; Mentioned effects is brought the harm of two aspects: on the one hand, generator electromotive force wave-wave shape is distorted, and make rotor surface and stator winding the local overheating phenomenon occur, can cause usually said " negative-sequence current burning machine " when serious; The 2nd, by the alternating electromagnetism torque that negative-sequence current produces 100Hz, this alternating electromagnetism torque acts on rotor shaft and the out frame simultaneously, causes that frequency is the vibration of per second 100Hz, might damage structures such as support.

According to above-mentioned analysis, and at the problem in the background technology, the present invention proposes a kind of method that under the unbalanced source voltage condition, improves the Speedless sensor identification precision, comprise: adopt the wind-driven generator of double-fed control system control, described double-fed control system is controlled the wind-driven generator rotating speed according to the rotary speed data that Speedless sensor obtains; Described Speedless sensor carries out PI self adaptation rotating speed by the MRAS reference model to stator voltage, stator current to be estimated to handle, and obtains rotary speed data; When line voltage is in poised state, directly with stator voltage and stator current as the input of MRAS reference model, estimate to handle back acquisition rotary speed data through PI self adaptation rotating speed; It is characterized in that: when unbalanced source voltage, obtain rotary speed data by the following method:

1) extract real-time generator unit stator voltage, the positive sequence component of stator current under the dq rotating coordinate system obtain the positive sequence voltage under the dq rotating coordinate system

With the forward-order current under the dq rotating coordinate system

2) will With

As the input of MRAS reference model, estimate to handle the back through PI self adaptation rotating speed and obtain rotary speed data;

In the preceding method, owing to abandoned because of the voltage that unbalanced source voltage causes, the interference of electric current negative sequence component in the reference model input variable in MRAS, make the rotary speed data of institute's identification only be subjected to the influence of positive sequence component, thereby make Speedless sensor when unbalanced source voltage, also can improve Speedless sensor to the adaptability of operation state of generator for the double-fed control system provides rotating speed Identification Data accurately.

Aforesaid PI self adaptation rotating speed is estimated to handle and is adopted the MRAS method to realize: will not contain the stator flux observer of true rotating speed and torque calculation as the reference model, with the PI adaptive rate that contains rotating speed to be identified as adjustable model, first acquisition speed adjuster output

T with stator flux observer and torque calculation gained _e, ask for both error signals

This error signal is sent into PI proportional integral adaptive law, and its output is the velocity estimation value

${\widehat{\mathrm{\ω}}}_r=(K_p+\frac{K_i}{s})({\hat{T}}_e^{*}-T_e)$

Wherein,

Be the velocity estimation value,

Be pi regulator, K _p, K _iBe respectively proportionality coefficient and integral coefficient;

Be the output signal of speed regulator, T _eObtained by stator flux observer and torque calculation.

In the content of aforementioned schemes, relate to and need whether be in the problem that non-equilibrium state is judged to line voltage, based on prior art, the inventor has proposed following preferred version and has judged whether line voltage is in non-equilibrium state, and concrete scheme is:

1] the positive and negative order component of extract real-time generator unit stator voltage under α β rest frame obtains α axle positive sequence voltage component

β axle positive sequence voltage component α axle negative sequence voltage component

With β axle negative sequence voltage component

2] calculate the positive sequence voltage amplitude according to following formula

With the negative sequence voltage amplitude

$u_{\mathrm{sm}}^{+}=\sqrt{{\left(u_{\mathrm{s\α}}^{+}\right)}^2+{\left(u_{\mathrm{s\β}}^{+}\right)}^2}$

$u_{\mathrm{sm}}^{-}=\sqrt{{\left(u_{\mathrm{s\α}}^{-}\right)}^2+{\left(u_{\mathrm{s\β}}^{-}\right)}^2}$

3] calculate unbalanced source voltage degree δ according to following formula:

$\mathrm{\δ}=\frac{u_{\mathrm{sm}}^{-}}{u_{\mathrm{sm}}^{+}}\×100\%;$

4] when δ 〉=5%, judge that line voltage is in non-equilibrium state; When δ＜5%, judge that line voltage is in poised state.

In order to guarantee the stability of double-fed generator operation, prior art can be combined with aforementioned schemes, make up following fault-tolerant control scheme:

Adopt speed sensor and Speedless sensor to obtain the generator speed data simultaneously, the rotary speed data that speed sensor gets access to is designated as speed A, and the rotary speed data that Speedless sensor gets access to is designated as speed B; During the speed sensor fault-free, the double-fed control system is controlled according to the wind-driven generator rotating speed of speed A, when speed sensor breaks down, adopts the wind-driven generator rotating speed of speed B to control.

Aforementioned fault-tolerant control scheme need be speed sensor and speed regulator of each independent configuration of Speedless sensor in the specific implementation.

In the aforementioned fault-tolerant control scheme, relate to the problem that need whether exist fault to judge to speed sensor, use for reference prior art, adopt following scheme to come method to judge whether speed sensor exists fault:

A, be calculated as follows the fault residual delta:

Δ＝|ω _A-ω _B|

Wherein, ω _ABe the current measured value of speed A, ω _BCurrent measured value for speed B;

B, be calculated as follows failure diagnosis adaptive threshold e:

e＝0.2·ω _B

C, Δ and e are compared: if Δ 〉=e judges that then speed sensor breaks down; If Δ＜e then judges the speed sensor fault-free.

Useful technique effect of the present invention is: make Speedless sensor be adapted to generator and work in control needs under the slight non-equilibrium state of line voltage, improve Speedless sensor accuracy of identification to rotating speed under the unbalanced source voltage state, the scope of application of expansion Speedless sensor has also realized the fault-tolerant control of double-fed wind power generator when the speed sensor fault simultaneously.

Description of drawings

Fig. 1, double-fed control system schematic diagram commonly used;

The double-fed control system schematic diagram of Fig. 2, the fault-tolerant control scheme of employing the present invention;

In Fig. 3, the fault-tolerant control scheme, judge whether speed sensor exists the principle schematic of fault (also being the schematic diagram of fault-tolerant control module among Fig. 2);

Fig. 4, unbalanced source voltage state are judged principle schematic;

Positive and negative order component extraction principle schematic under Fig. 5, the α β rest frame;

Fig. 6, PI self adaptation rotating speed are estimated the handling principle schematic diagram;

The flow chart of Fig. 7, the fault-tolerant control scheme of the present invention.

Embodiment

For making those skilled in the art understand the present invention better, be necessary that it is double-fed control system schematic diagram commonly used that existing double-fed control system is made a brief description: Fig. 1, can find out from this figure, the rotor-side system adopts rotor current, the two closed-loop controls of rotor speed, wherein, interior ring is the rotor current control ring, by the detection rotor phase current, through 3s/2s(three phase static coordinate/two-phase static coordinate) and 2s/2r(two-phase static coordinate/two cordic phase rotators) two step conversion, the i under the synchronous rotating frame obtained _Rd, i _RqTwo control channels, the set-point i of rotor current _Rd ^*, i _Rq ^*With i _Rd, i _RqError relatively adopts the PI mode through the current regulator ACR(of band integration and output violent change) regulate after the output voltage controlled quentity controlled variable, this voltage control quantity front feedback voltage compensation amount △ u that superposes respectively _Rd, △ u _RqObtain the rotor voltage controlled quentity controlled variable, this controlled quentity controlled variable is again through 2r/2s(two cordic phase rotators/two-phase static coordinate) conversion, SVPWM modulation back produces generator amature side actual required exciting voltage and exciting current, realizes that the decoupling zero of double-fed wind power generator vector control system rotor-side is controlled.In accompanying drawing 1, the outer shroud of vector control system is the rotor speed control ring, and is similar with current inner loop, rotary speed setting value ω _r ^*With the speed feedback value that is recorded by speed sensor (optical code disk) back gained difference relatively, adopt the PI mode through speed regulator ASR() regulate after, obtain the output torque T of generator _e ^*, the output torque is calculated through torque current again, obtains the set-point i of rotor current real component _Rq ^*And the set-point i of rotor current idle component _Rd ^*, normally calculate according to the idle requirement of electrical network to the wind-driven generator vector control system.

Fig. 2 is formed control system figure after the employing fault-tolerant control scheme of the present invention, different with existing control method is: system adopts Redundancy Design, namely adopt speed sensor and Speedless sensor mode simultaneously, obtain the wind power generator rotor rotating speed, the tachometer value that speed sensor is recorded uses as control under the normal condition, and the tachometer value that Speedless sensor observation obtains is as standby; When speed sensor breaks down, enable the Speedless sensor measured value again.In the design of this system, consider that Speedless sensor is subject to the negative sequence component influence under the unbalanced source voltage condition, therefore, used in this system in master's scheme of the present invention based on the PI self adaptation rotating speed of MRAS and estimated that processing mode obtains the Speedless sensor measured value under the Voltage unbalance condition, that is: when Speedless sensor works separately, in the wind-driven generator running, at first line voltage is just being carried out, the negative separation, and judge whether balance of line voltage, work as unbalanced source voltage, then suppress the interference of negative sequence voltage and negative-sequence current component, the signal that only contains positive sequence voltage and forward-order current is input in " estimation of PI self adaptation rotating speed " module, to obtain the Speedless sensor measured value more identical with the actual speed signal, overcoming the negative sequence component that existing Speedless sensor is subject under the unbalanced source voltage state influences, cause Speedless sensor to be difficult to the defective that rotating speed is accurately observed.

In Fig. 2, judge whether speed sensor breaks down, can be determined that referring to Fig. 3, this link output two paths of signals is used for the switching controls under the speed sensor fault respectively to transducer A and transducer B by " fault-tolerant control " link;

When " fault-tolerant control " link is judged speed sensor just often, rotary speed setting value ω _r ^*With the speed feedback value ω that is recorded by speed sensor _rRelatively the difference of back gained after speed regulator ASR1 regulates, obtains the output torque T of generator _e ^*, at this moment, " fault-tolerant control " link is connected 1 and 3 in the transducer A, and 2 and 4 connect, and will export torque T _e ^*Export torque current to and calculate link; Simultaneously, " fault-tolerant control " link is connected 1 and 3 in the transducer B, and 2 and 4 connect, the speed feedback value ω that speed sensor is recorded _rExport the voltage compensation link to.

When " fault-tolerant control " when link is judged the speed sensor fault, enable standby Speedless sensor rotating speed measured value, rotary speed setting value ω _r ^*With the speed feedback value that is observed by Speedless sensor

(subscript " ^ " is represented by the observation value of obtaining) be the difference of back gained relatively, after speed regulator ASR2 regulates, obtains the output torque of generator

This exports torque

Divide two-way output: the one tunnel exports PI self adaptation rotating speed to estimates, as the rotating speed identification; Transducer A is directly delivered on another road; At this moment, " fault-tolerant control " link is connected 1 and 4 in the transducer A, and 2 and 5 connect, and will export torque

Deliver to torque current and calculate link; Simultaneously, speed probe fault tolerance judgment controlling unit is connected 1 and 4 in the transducer B, and 2 and 5 connect, the speed feedback value that Speedless sensor is recorded

Export the voltage compensation link to.

Below in conjunction with accompanying drawing, " fault-tolerant control ", " the unbalanced source voltage degree is judged and handled ", " estimation of PI self adaptation rotating speed " this three part of addressing in the preamble is introduced respectively.

(1) " fault-tolerant control "

The speed probe fault type can be divided into hard fault and soft fault two classes usually according to fault degree; Wherein, hard fault is generally damaged or is subjected to cause than reasons such as hard pulse interference to have output amplitude variation characteristics greatly by the transducer components and parts; And soft fault general reference is owing to the fault that reasons such as part aging, null offset cause, and has that output amplitude changes not quite and characteristics more slowly.

Fig. 3 is the schematic diagram of the fault-tolerant control module among Fig. 2, obtain the fault residual error after by " calculate fault residual error " link speed sensor output valve and Speedless sensor observer value being compared among the figure, simultaneously, by " calculating the failure diagnosis adaptive threshold " link dynamic calculation failure diagnosis adaptive threshold, the pertinent literature of choosing with reference to adaptive threshold commonly used in the fault detect, get 0.2 times of observer output valve as the adaptive threshold of failure diagnosis, this threshold parameter can the adaptive change with the change of observer rotational speed output signal; By " fault judgement " link fault residual error and failure diagnosis adaptive threshold are compared then, in order to judge whether speed sensor breaks down, when the fault residual error greater than the failure diagnosis adaptive threshold, speed sensor fault then, otherwise speed sensor is normal.

(2) " the unbalanced source voltage degree is judged and is handled "

Fig. 4 is the schematic diagram of " the unbalanced source voltage degree is judged and handled " module among Fig. 2; Extract voltage signal and the positive and negative order component of current signal under α β rest frame by " the positive and negative order of voltage signal is separated " link respectively with " the positive and negative order of current signal is separated " link earlier among the figure, then by " positive sequence voltage amplitude " link and " negative sequence voltage amplitude

" link calculates positive sequence voltage amplitude and negative sequence voltage amplitude; " calculating unbalanced source voltage degree δ " link is calculated unbalanced source voltage degree δ according to positive sequence voltage amplitude and negative sequence voltage crest meter; and according to the size of Voltage unbalance degree δ the action of transducer C and transducer D is controlled; when aforementioned processing is carried out; the positive sequence voltage after will separating and not separated voltage all carry out 2s/2r(two-phase static coordinate/two cordic phase rotators) conversion, and export the two paths of signals after the conversion to transducer C; In like manner, current signal is also done to handle with the similar coordinate system transformation of voltage, export the two paths of signals after the conversion to transducer D; Consider that the wind-powered electricity generation unit can bear transient state and reach 5%(even higher) unbalance voltage and do not trip, with δ=5% as the line voltage separation of balance whether, when the δ that tries to achieve when calculating is worth less than this, can think that line voltage is balance, 1 and 3 of transducer C connects, 2 and 4 connect, the voltage u under the transducer C output dq rotating coordinate system _SdqAnd when calculating the δ try to achieve more than or equal to 5% the time, can think unbalanced source voltage, and 1 and 4 of transducer C is connected, 2 and 5 connect, the positive sequence voltage under the transducer C output dq rotating coordinate system Current signal is also done similar processing, and transducer D is the alternative current i of exporting under the line voltage balance also _SdqOr the forward-order current of line voltage under imbalance

Fig. 5 is the principle schematic of " the positive and negative order of voltage signal is separated " link among Fig. 4, the positive and negative order of voltage signal is separated existing " T/4 delays time (T is the electrical network fundamental voltage the cycle) " method of employing and realized: under α β rest frame, the positive and negative sequence voltage after the separation is shown below respectively.

$u_{\mathrm{s\α}}^{+}=\frac{1}{2}[u_{\mathrm{s\α}}\left(t\right)-u_{\mathrm{s\β}}(t-T/4)]---\left(1\right)$

$u_{\mathrm{s\α}}^{-}=\frac{1}{2}[u_{\mathrm{s\α}}\left(t\right)+u_{\mathrm{s\β}}(t-T/4)]---\left(2\right)$

$u_{\mathrm{s\β}}^{+}=\frac{1}{2}[u_{\mathrm{s\β}}\left(t\right)-u_{\mathrm{s\α}}(t-T/4)]---\left(3\right)$

$u_{\mathrm{s\β}}^{-}=\frac{1}{2}[u_{\mathrm{s\β}}\left(t\right)-u_{\mathrm{s\α}}(t-T/4)]---\left(4\right)$

Each parameter is respectively in the formula: α axle positive sequence voltage component

β axle positive sequence voltage component α axle negative sequence voltage component β axle negative sequence voltage component

α shaft voltage component u _{S α}(t), β shaft voltage component u _{S β}(t), T is the electrical network fundamental voltage cycle, t is the time.

Positive sequence voltage amplitude after the separation

Can be tried to achieve by following formula:

$u_{\mathrm{sm}}^{+}=\sqrt{{\left(u_{\mathrm{s\α}}^{+}\right)}^2+{\left(u_{\mathrm{s\β}}^{+}\right)}^2}---\left(5\right)$

Negative sequence voltage amplitude after the separation

Can be tried to achieve by following formula:

$u_{\mathrm{sm}}^{-}=\sqrt{{\left(u_{\mathrm{s\α}}^{-}\right)}^2+{\left(u_{\mathrm{s\β}}^{-}\right)}^2}---\left(6\right)$

The unbalanced source voltage degree is negative sequence voltage and the percentage value of the ratio of positive sequence voltage, namely

$\mathrm{\δ}=\frac{u_{\mathrm{sm}}^{-}}{u_{\mathrm{sm}}^{+}}\×100\%---\left(7\right)$

(3) " estimation of PI self adaptation rotating speed "

Fig. 6 is the schematic diagram of " estimation of PI self adaptation rotating speed " module among Fig. 2.PI self adaptation rotating speed estimates to have utilized self adaptation thought, adopt model reference adaptive (MRAS) mode to obtain the speed measured value, it is a kind of respond well speed estimation method, its basic thought takes full advantage of the control system existing structure exactly, with the stator flux observer that do not contain true rotating speed and torque calculation as the reference model, with the PI adaptive rate that contains rotating speed to be identified as adjustable model.Reference model wherein is for being used for stator flux observer and torque T _eCalculating, below be derivation and the explanation to its formula.

According to the Electrical Motor theory, the double-fed generator Mathematical Modeling is in the synchronous rotating frame:

$\left.\begin{array}{c}{u}_{\mathrm{sd}}=-R_s{i}_{\mathrm{sd}}+{\mathrm{\ω}}_1{\mathrm{\ψ}}_{\mathrm{sq}}-p{\mathrm{\ψ}}_{\mathrm{sd}},u_{\mathrm{sq}}=-R_s{i}_{\mathrm{sq}}-{\mathrm{\ω}}_1{\mathrm{\ψ}}_{\mathrm{sd}}-{\mathrm{p\ψ}}_{\mathrm{sq}}\\ u_{\mathrm{rd}}=R_r{i}_{\mathrm{rd}}-{\mathrm{\ω}}_s{\mathrm{\ψ}}_{\mathrm{rq}}+p{\mathrm{\ψ}}_{\mathrm{rd}},u_{\mathrm{rq}}=R_r{i}_{\mathrm{rq}}+{\mathrm{\ω}}_s{\mathrm{\ψ}}_{\mathrm{rd}}+p{\mathrm{\ψ}}_{\mathrm{rq}}\end{array}\right\}---\left(8\right)$

$\left.\begin{array}{c}{\mathrm{\ψ}}_{\mathrm{sd}}=l_s{i}_{\mathrm{sd}}-l_m{i}_{\mathrm{rd}},{\mathrm{\ψ}}_{\mathrm{sq}}=l_s{i}_{\mathrm{sq}}-l_m{i}_{\mathrm{rq}}\\ {\mathrm{\ψ}}_{\mathrm{rd}}=-l_m{i}_{\mathrm{sd}}+l_r{i}_{\mathrm{rd}},{\mathrm{\ψ}}_{\mathrm{rq}}=-l_m{i}_{\mathrm{sq}}+l_r{i}_{\mathrm{rq}}\end{array}\right\}---\left(9\right)$

$T_e=\frac{3}{2}{p}_N{l}_m(i_{\mathrm{sd}}{i}_{\mathrm{rq}}-i_{\mathrm{sq}}{i}_{\mathrm{rd}})---\left(10\right)$

In the formula, R _sBe stator resistance, R _rBe rotor resistance, l _sBe stator inductance, l _rThe rotor resistance inductance; l _mBe mutual inductance between rotor; ω ₁Be synchronous angular velocity of rotation, ω _rBe rotor velocity, ω _sBe slip angular velocity, ω _s=ω ₁-ω _rP is differential operator, p _NBe number of pole-pairs, u _Sd, u _Sq, i _Sd, i _Sq, ψ _Sd, ψ _SqBe respectively voltage, electric current and the magnetic flux of stator dq axle under the synchronous rotating frame; u _Rd, u _Rq, i _Rd, i _Rq, ψ _Rd, ψ _RqBe respectively voltage, electric current and the magnetic flux of synchronous rotating frame lower rotor part dq axle; T _eBe electromagnetic torque.

For the grid type wind generator system, can ignore the influence of stator resistance.When the d axle of selecting coordinate system along ψ ₁When directed, then have:

ψ _sd＝ψ ₁，ψ _sq＝0 （11）

u _sd＝0，u _sq＝-u ₁ （12）

In the formula, u ₁Be the line voltage effective value.

Formula (11), (12) substitution formula (8):

${\mathrm{\&psi;}}_1=\frac{{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="HDA00003344056100032.png"\; state="\{\{state\}\}">u</figure-callout>}}_1}{{\mathrm{\&omega;}}_1}---\left(13\right)$

With formula (9) substitution formula (10):

$T_e=\frac{3}{2}{p}_N{i}_{\mathrm{sq}}{\mathrm{\&psi;}}_1---\left(14\right)$

Can be found out by (13), (14) formula: in the MRAS system, calculate resulting electromagnetic torque T by reference model _ePhysical quantitys such as complete voltage by stator side, electric current determine.And when unbalanced source voltage, the three-phase alternating current system includes the electromagnetic quantities such as voltage, electric current and magnetic linkage of positive and negative order composition.In the Speed identification based on MRAS, be exactly to want accurately to the basic demand of reference model.Because reference model is as the benchmark of MRAS control, have only this reference model accurate, Speedless sensor just can obtain more believable identifier.Therefore, when the electric power system asymmetric operation, caused under the situation that the harmonic component of electric current in the electric power system, voltage increases by negative-sequence current, how obtaining comparatively accurately, stator flux observer value and electromagnetic torque Te value just seem extremely important.The present invention separates positive and negative order component in asymmetric three-phase voltage, current system exactly fast, to get rid of negative phase-sequence even harmonic component to the influence of Speedless sensor identification precision, with the input as the MRAS reference model of positive sequence voltage under the two-phase rotating coordinate system, electric current, in the hope of obtaining more stator flux observer value and the calculating torque of standard, thereby improve the Speedless sensor identification precision.

The acquisition speed adjuster ASR2 of elder generation output And with the above-mentioned electromagnetic torque T that is obtained by reference model _eValue is asked for both error signals This error signal is sent into proportional integral adaptive law (pi regulator), and its output is the velocity estimation value

That is:

${\widehat{\mathrm{\&omega;}}}_r=(K_p+\frac{K_i}{s})({\hat{T}}_e^{*}-T_e)---\left(15\right)$

Wherein,

Be the velocity estimation value,

Be pi regulator, K _p, K _iBe respectively proportionality coefficient and integral coefficient;

Be speed regulator ASR2 output signal, T _eObtained by stator flux observer and torque calculation.

The velocity estimation value of gained

Namely be used for the operation control of double-fed wind power generator.

Fig. 7 has provided the flow chart of the fault-tolerant control scheme of the present invention.

For verifying effect of the present invention, velocity transducer has broken down and the unbalanced source voltage degree is under the condition of δ=6% being set with, and emulation experiment has been carried out in the rotating speed observation of double-fed speed-variable frequency-constant wind-driven generator; It is as follows to test used wind turbine generator parameter: blower fan blade number 3, rotor diameter D=5m, best tip speed ratio λ=9.5, gear box speed increasing ratio N=7.56, generator rating power P _n=4kW, number of pole-pairs p _N=2, moment of inertia J=0.87kg.m ²

Experiment divides the given and dynamic rotating speed of steady-state speed to switch two kinds of situations to carry out, the identification error of Speedless sensor during with more original scheme (namely not with negative sequence component situation during rejecting from the input voltage of MRAS reference model and electric current) and employing the present invention program.Table 1 and table 2 are respectively under given different rotating speeds, adopt original scheme and adopt the present invention program to survey the table of comparisons of rotating speed and identification speed error; Table 3 and table 4 be respectively generator in the time of the 3rd second by metasynchronism speed

State switches to supersynchronous speed

State adopts original scheme and adopts the present invention program to survey the table of comparisons of rotating speed and identification speed error.

Actual measurement rotating speed and the identification speed error table of comparisons (original scheme) under table 1 given rotating speed

Rotational speed setup (rpm)	1290	1340	1390	1440	1490	1540	1590
								Actual measurement rotating speed (rpm)	1289.3	1338.1	1391.5	1441.8	1488.5	1539.6	1588.3
Identification rotating speed (rpm)	1244.2	1303.3	1417.9	1502.4	1546.6	1565.8	1624.8
								Identification is poor with the actual measurement rotating speed	-45.13	-34.8	26.44	60.6	58.1	26.2	36.5
Percentage error (%)	-3.5	-2.6	1.9	4.2	3.9	1.7	2.3

Actual measurement rotating speed and the identification speed error table of comparisons (the present invention program) under table 2 given rotating speed

Rotational speed setup (rpm)	1290	1340	1390	1440	1490	1540	1590
								Actual measurement rotating speed (rpm)	1289.3	1338.1	1391.5	1441.8	1488.5	1539.6	1588.3
Identification rotating speed (rpm)	1277.7	1331.4	1409.6	1466.3	1504.8	1548.8	1596.2
								Identification is poor with the actual measurement rotating speed	-11.6	-6.7	18.1	24.5	16.4	9.2	7.9
Percentage error (%)	-0.9	-0.5	1.3	1.7	1.1	0.6	0.5

Table 3 rotating speed switches actual measurement rotating speed and the identification speed error table of comparisons (original scheme) down

Table 4 rotating speed switches actual measurement rotating speed and the identification speed error table of comparisons (the present invention program) down

Contrast by above-mentioned table can be found out, adopt after the present invention program, owing to get rid of voltage, electric current negative phase-sequence even harmonic component to the interference of MRAS reference model, no matter be given or switch in the dynamic process at rotating speed at steady-state speed, all improved the identification precision of Speedless sensor, made Speedless sensor measured value and actual speed value more identical.Therefore, this method is that dual feedback wind power generation system is realized under the fault-tolerant control under the uneven electrical network condition, and more accurate Speedless sensor identification precision is provided, and can improve control performance and the stability of whole generating unit.

Claims (4)

1. improve the method for Speedless sensor identification precision under the unbalanced source voltage condition, comprise: adopt the wind-driven generator of double-fed control system control, described double-fed control system is controlled the wind-driven generator rotating speed according to the rotary speed data that Speedless sensor obtains; Described Speedless sensor carries out PI self adaptation rotating speed by the MRAS reference model to stator voltage, stator current to be estimated to handle, and obtains rotary speed data; When line voltage is in poised state, directly with stator voltage and stator current as the input of MRAS reference model, estimate to handle back acquisition rotary speed data through PI self adaptation rotating speed; It is characterized in that: when unbalanced source voltage, obtain rotary speed data by the following method:

1) extract real-time generator unit stator voltage, the positive sequence component of stator current under the dq rotating coordinate system obtain the positive sequence voltage under the dq rotating coordinate system

With the forward-order current under the dq rotating coordinate system

2) will With

As the input of MRAS reference model, estimate to handle the back through PI self adaptation rotating speed and obtain rotary speed data;

In the preceding method, owing in the input variable of MRAS reference model, abandoned because of the voltage that unbalanced source voltage causes, the interference of electric current negative sequence component, make the rotary speed data of institute's identification only be subjected to the influence of positive sequence component, thereby make Speedless sensor when unbalanced source voltage, also can provide rotating speed Identification Data accurately for the double-fed control system.

2. improve the method for Speedless sensor identification precision under the unbalanced source voltage condition according to claim 1, it is characterized in that: judge according to following method whether line voltage is in non-equilibrium state:

1] the positive and negative order component of extract real-time generator unit stator voltage under α β rest frame obtains α axle positive sequence voltage component

β axle positive sequence voltage component

α axle negative sequence voltage component

With β axle negative sequence voltage component

2] calculate the positive sequence voltage amplitude according to following formula

With the negative sequence voltage amplitude

$u_{\mathrm{sm}}^{+}=\sqrt{{\left(u_{\mathrm{s\&alpha;}}^{+}\right)}^2+{\left(u_{\mathrm{s\&beta;}}^{+}\right)}^2}$

$u_{\mathrm{sm}}^{-}=\sqrt{{\left(u_{\mathrm{s\&alpha;}}^{-}\right)}^2+{\left(u_{\mathrm{s\&beta;}}^{-}\right)}^2}$

3] calculate unbalanced source voltage degree δ according to following formula:

$\mathrm{\&delta;}=\frac{u_{\mathrm{sm}}^{-}}{u_{\mathrm{sm}}^{+}}\&times;100\%;$

4] when δ 〉=5%, judge that line voltage is in non-equilibrium state; When δ＜5%, judge that line voltage is in poised state.

3. improve the method for Speedless sensor identification precision under the unbalanced source voltage condition according to claim 1, it is characterized in that: adopt following method that wind-driven generator is carried out fault-tolerant control:

Adopt speed sensor and Speedless sensor to obtain the generator speed data simultaneously, the rotary speed data that speed sensor gets access to is designated as speed A, and the rotary speed data that Speedless sensor gets access to is designated as speed B; During the speed sensor fault-free, the double-fed control system is controlled according to the wind-driven generator rotating speed of speed A, when speed sensor breaks down, adopts the wind-driven generator rotating speed of speed B to control.

4. improve the method for Speedless sensor identification precision under the unbalanced source voltage condition according to claim 3, it is characterized in that: judge according to following method whether speed sensor exists fault:

A, be calculated as follows the fault residual delta:

Δ＝|ω _A-ω _B|

Wherein, ω _ABe the current measured value of speed A, ω _BCurrent measured value for speed B;

B, be calculated as follows failure diagnosis adaptive threshold e:

e＝0.2·ω _B

C, Δ and e are compared: if Δ 〉=e judges that then speed sensor breaks down; If Δ＜e then judges the speed sensor fault-free.

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