CN102088191B - Method and system for cooperatively controlling low voltage ride through of full-power fan converter - Google Patents

Abstract

The invention provides a method and system for cooperatively controlling a low voltage ride through of a full-power fan converter. The method comprises the following steps of: judging dropping and resilient stability of a voltage of a power grid; when the voltage of the power grid is in a dropping transient state or a rising transient state, carrying out temporary forced locking on a driving signal of a power switching tube device of a network side converter; and when the voltage of the power grid is in a dropping stable state or is recovered to the normal stable state, relieving locking of the driving signal of the power switching tube device of the network side converter. Meanwhile, the method and the system are matched with work of a crowbar circuit so as to realize the low voltage ride through of the network side converter. In the invention, different states of the voltage of the power grid are judged by a positive sequence component and a negative sequence component of the voltage of the power grid so as to carry out different controls. Moreover, only the network side converter is controlled and a machine side converter can always normally operate, so that the mechanical stress of a wind machine and a driving chain, which is caused by electromagnetic torque pulsation of a generator, is reduced.

Description

Cooperative control method and system that a kind of total power blower fan current transformer low-voltage is passed through

Technical field

The present invention relates to technical field of wind power generation, cooperative control method and system that particularly a kind of total power blower fan current transformer low-voltage is passed through.

Background technology

Along with the continuous expansion of wind power generation scale, wind generator system is to the influence of electrical network more and more significant.In the total power wind power system, the generator unit stator winding inserts electrical network through full power convertor, and is good to the adaptability of power network fluctuation; And the independent of active power and reactive power of realizing being incorporated into the power networks controlled; Therefore generating efficiency is high, and structure is comparatively simple, good operation stability.Referring to Fig. 1, this figure is the structure chart of at present typical total power wind generator system.

This electricity generation system adopts the two PWM current transformers of total power (comprising pusher side current transformer 100 and net side converter 300) to be connected generator M and electrical network.Wherein, generator M sends the electric energy that sends to pusher side current transformer 100, and pusher side current transformer 100 carries out rectification with the alternating current that generator M sends, and rectification is a direct current, and direct current is through sending net side converter 300 to behind the crowbar circuit 200 then.Net side converter 300 is given electrical network with dc inverter for the alternating current rear feed that frequency and amplitude with electrical network are complementary again, thereby realizes being incorporated into the power networks of wind power generation.

Wherein, the major function of crowbar circuit 200 is when DC bus-bar voltage rises, and consumes excess energy.

In wind generator system, electric network electric voltage drop is the modal fault of electrical network.Mainly because transmission line malfunction causes, its fault type has following several kinds to electric network electric voltage drop: single phase ground fault, double earthfault, two phase phase fault and three phase short circuit fault.Wherein according to the situation of change of electrical network phase voltage amplitude in falling process, can electric network electric voltage drop be summed up as three-phase imbalance simply again and fall with three-phase equilibrium and fall two big types.The degree of depth of electric network electric voltage drop is also inequality, minimumly can drop into zero, and the time of duration from 0.5 line voltage cycle to several seconds is not waited.

When electric network electric voltage drop, for the stability and the fail safe of the operation of assurance system, the net side converter of total power blower fan current transformer need have low-voltage and pass through (LVRT, Low-Voltage Ride Through) function.Low-voltage is passed through, and is meant at blower fan to be incorporated into the power networks when point voltage falls, and blower fan can keep being incorporated into the power networks, even to electrical network certain reactive power is provided, and supports power system restoration, and is normal up to power system restoration, thus " passing through " this low-voltage time (zone).The low-voltage crossing technology is a very crucial technology in the wind generator system, is concerning the large-scale application of wind-powered electricity generation.

In the total power wind generator system, the moment of line voltage is fallen and reduces causing netting the side converter power output, and if this moment the pusher side current transformer still real-time response always control dtc signal, not matching of energy will cause the rising of DC bus-bar voltage.To threaten the life-span of the power switch tube device of net side converter and pusher side current transformer like this.Therefore, when electric network electric voltage drop, need solve the energy matching problem of net side converter and pusher side current transformer.

At present, when electric network electric voltage drop, solve the energy matching problem and mainly contain three kinds of approach, be respectively:

The first, start with from current transformer design, selects withstand voltage with cross the higher power electronic device of flow valuve, and improve the rated voltage that direct current supports electric capacity, but withstand voltage big with the high device cost of flow valuve higher;

The second, reduce the electromagnetic torque set point of generator, thereby allow the temporary transient rising of torque to store blower fan part intake, reduce the power output of generator, the power-balance when helping electric voltage dropping.But, will cause the electromagnetic torque of generator bigger fluctuation to occur, the mechanical stress of blower fan and driving-chain is increased, influence fan life.

The 3rd, utilize crowbar circuit to consume excess energy.But, need guarantee crowbar circuit in correct moment action and disengaging, otherwise switching and stable operation before and after the system failure will be affected because the rising of the electrical network DC bus-bar voltage that electric network electric voltage drop causes is a transient process.

In sum, at present all there is certain problem in the total power blower fan current transformer low-voltage control method of passing through.

Summary of the invention

The technical problem that the present invention will solve provides cooperative control method and the system that a kind of total power blower fan current transformer low-voltage is passed through; The current transformer device can not changed; Do not change under the prerequisite of electromagnetic torque of generator, solve the energy mismatch problem that electric network electric voltage drop causes.

The cooperative control method that the present invention provides a kind of total power blower fan current transformer low-voltage to pass through may further comprise the steps:

Steps A: judge that electrical network generation three-phase equilibrium is fallen or three-phase imbalance when falling by the positive sequence component of current line voltage and negative sequence component, the drive signal of the power switch tube device in the net side converter is carried out of short duration pressure block;

Step B: judge by the positive sequence component of current line voltage and negative sequence component that electrical network falls and reach when stablize, remove blockade to the drive signal of netting the power switch tube device in the side converter;

Step C: judge that by the positive sequence component of current line voltage and negative sequence component electrical network by falling when beginning to recover, carries out of short duration blockade to the drive signal of the power switch tube device in the net side converter;

Step D: when judging power system restoration to normal and stable, remove blockade to the drive signal of netting the power switch tube device in the side converter by the positive sequence component of current line voltage and negative sequence component;

In steps A, B, C and D, control crowbar circuit through comparison DC bus-bar voltage and scheduled voltage and whether work.

Preferably, the idle criterion of said crowbar circuit is: DC bus-bar voltage is less than setting the direct voltage minimum value; The criterion of said crowbar circuit work is: DC bus-bar voltage is greater than setting the direct voltage maximum.

Preferably, the positive sequence component of said current line voltage and negative sequence component are calculated by the net side three-phase voltage of two synchronous coordinate system software phase-lock loops according to the voltage sensor collection.

Preferably, when the positive sequence component of judging current line voltage during, judge that electrical network generation three-phase equilibrium falls in the steps A less than first scheduled voltage of the line voltage in previous cycle;

When second scheduled voltage of the positive sequence component of judging current line voltage less than the line voltage in previous cycle; And when the negative sequence component of the negative sequence component of current line voltage and the line voltage in previous cycle differs predetermined amplitude, judge that electrical network generation three-phase imbalance falls.

The cooperative control system that the present invention also provides a kind of total power blower fan current transformer low-voltage to pass through comprises with lower unit:

Computing unit is used for calculating positive sequence component and the negative sequence component that obtains line voltage in real time by the three-phase voltage of current electrical network;

Fall judging unit, the positive sequence component of the current line voltage that is used for being obtained in real time by computing unit and negative sequence component judge whether electrical network takes place that three-phase equilibrium is fallen or three-phase imbalance falls;

Fall the stabilize decision unit, the positive sequence component of the current line voltage that is used for being obtained in real time by computing unit and negative sequence component are judged whether electrical network falls and are reached stable;

Fall the recovery judging unit, be used for judging by the positive sequence component and the negative sequence component of the real-time current line voltage that obtains of computing unit whether electrical network begins to recover by falling;

Recover normal judging unit, be used for judging by the positive sequence component and the negative sequence component of the real-time current line voltage that obtains of computing unit whether electrical network returns to normal and stable;

Drive signal is blocked the unit, is used for falling or three-phase imbalance when falling the drive signal of blocking the power switch pipe of netting side converter when electrical network generation three-phase equilibrium; Also be used for when electrical network by falling when beginning to recover, block the drive signal of the power switch pipe of net side converter;

Drive signal is removed the unit, is used for falling when stablize when electrical network, and releasing is to the blockade of the drive signal of the power switch tube device of netting side converter; Also be used for when power system restoration arrives normal and stable, releasing is to the blockade of the drive signal of the power switch tube device of net side converter;

The crowbar circuit control unit is used for DC bus-bar voltage and scheduled voltage are relatively controlled the work of crowbar circuit.

Preferably, said crowbar circuit control unit, when DC bus-bar voltage less than setting the direct voltage minimum value, be used to control crowbar circuit and do not work; When DC bus-bar voltage greater than setting the direct voltage maximum, be used to control crowbar circuit work.

Preferably, also comprise net side three-phase voltage transducer, be used to gather the three-phase voltage of net side, the three-phase voltage of the net side of gathering is sent to said computing unit.

Preferably, the said judging unit that falls comprises that judgment sub-unit is fallen in three-phase equilibrium and three-phase imbalance falls judgment sub-unit;

Judgment sub-unit is fallen in said three-phase equilibrium, and the positive sequence component that is used for more current line voltage is during less than first scheduled voltage of the line voltage in previous cycle, judges that electrical network generation three-phase equilibrium falls;

Said three-phase imbalance falls judgment sub-unit; Be used for second scheduled voltage of more current line voltage positive sequence component less than the line voltage in previous cycle; And when the negative sequence component of the negative sequence component of current line voltage and the line voltage in previous cycle differs predetermined amplitude, judge that electrical network generation three-phase imbalance falls.

Compared with prior art, the present invention has the following advantages:

The cooperative control method that the total power blower fan current transformer low-voltage that the embodiment of the invention provides is passed through falls and recovers stable judgement line voltage; When line voltage is in the transient state fallen or during the transient state that rises, the drive signal of the power switch tube device of net side converter is carried out temporary transient pressure block; Fall stable or when recovering normal and stable when line voltage is in, remove blockade the drive signal of the power switch tube device of net side converter.Simultaneously, cooperate the low-voltage of the work realization net side converter of crowbar circuit to pass through.The present invention judges that through the positive sequence component and the negative sequence component of line voltage the different conditions of line voltage carries out Different control; And only be that the net side converter is controlled; The pusher side current transformer can normally move always, has reduced the wind energy conversion system that the generator electromagnetic torque pulsation brings and the mechanical stress of driving-chain.

Description of drawings

Fig. 1 is the structure chart of typical directly-driving wind power generation system in the prior art;

Fig. 2 is the schematic diagram of DDSRF-SPLL of the present invention;

Fig. 3 is cooperative control method embodiment one flow chart provided by the invention;

Fig. 4 is a cooperative control method theory diagram provided by the invention;

Fig. 5 is cooperative control method embodiment two flow charts provided by the invention;

Fig. 6 is net side converter response wave shape figure when to be that line voltage provided by the invention is single-phase fall;

Fig. 7 is that line voltage two provided by the invention falls time net side converter response wave shape figure mutually;

Fig. 8 is that time net side converter response wave shape figure is fallen in line voltage three-phase equilibrium provided by the invention;

Fig. 9 is the present invention pusher side response wave shape figure when providing the line voltage three-phase equilibrium to fall;

Figure 10 is cooperative control system embodiment one structure chart provided by the invention;

Figure 11 is cooperative control system embodiment two structure charts provided by the invention.

Embodiment

For those skilled in the art understand the technical scheme with embodiment of the present invention better; At first introduce two synchronous coordinate system software phase-lock loops (DDSRF-SPLL, Decoupled Double Synchronous Reference Frame Soft Phase-locked Loop) below.

The basic principle of DDSRF-SPLL is referring to shown in Figure 2, and this figure is the schematic diagram of DDSRF-SPLL.

DDSRF comprises two rotating coordinate systems, wherein positive sequence dq ^{+ 1}Synchronous rotating frame is rotated counterclockwise with ω angular speed, and its angle is made as

And negative phase-sequence dq ^-1Synchronous rotating frame is that the angular speed with-ω turns clockwise, and its angle is made as

ω is the angular speed that SPLL calculates.u _a, u _b, u _cThree-phase voltage for the electrical network of voltage sensor senses.Abc/dqm representes that the three phase static coordinate is tied to positive sequence dq ^{+ 1}The conversion of synchronous rotating frame, abc/dqn representes that the three phase static coordinate is tied to negative phase-sequence dq ^-1The conversion of synchronous rotating frame.

Be respectively positive sequence dq ^{+ 1}The d axle in the synchronous rotating frame and the line voltage component of q axle,

Be respectively negative phase-sequence dq ^-1The d axle in the synchronous rotating frame and the line voltage component of q axle.

and are calculated using a decoupling network.Adopt a simple low-pass first order filter among Fig. 2, its transfer function is:

$\mathrm{LPF}\left(s\right)=\frac{{\mathrm{\ω}}_f}{s+{\mathrm{\ω}}_f}---\left(1\right)$

Then shown in Figure 2, the fundametal compoment of and can be represented as follows:

${{\stackrel{\‾}{U}}_q}^p\left(s\right)=\frac{{\mathrm{\ω}}_f}{s+{\mathrm{\ω}}_f}{U_q}^{*p}\left(s\right)=\frac{{\mathrm{\ω}}_f}{s+{\mathrm{\ω}}_f}({U_q}^p\left(s\right)-U_1\left(s\right)*{{\stackrel{\‾}{U}}_q}^n\left(s\right)-U_2\left(s\right)*{{\stackrel{\‾}{U}}_d}^n\left(s\right))---\left(2\right)$

${{\stackrel{\‾}{U}}_d}^p\left(s\right)=\frac{{\mathrm{\ω}}_f}{s+{\mathrm{\ω}}_f}{U_d}^{*p}\left(s\right)=\frac{{\mathrm{\ω}}_f}{s+{\mathrm{\ω}}_f}({U_d}^p\left(s\right)-U_1\left(s\right)*{{\stackrel{\‾}{U}}_d}^n\left(s\right)+U_2\left(s\right)*{{\stackrel{\‾}{U}}_q}^n\left(s\right))---\left(3\right)$

${{\stackrel{\‾}{U}}_q}^n\left(s\right)=\frac{{\mathrm{\ω}}_f}{s+{\mathrm{\ω}}_f}{U_q}^{*n}\left(s\right)=\frac{{\mathrm{\ω}}_f}{s+{\mathrm{\ω}}_f}({U_q}^n\left(s\right)-U_1\left(s\right)*{{\stackrel{\‾}{U}}_q}^p\left(s\right)+U_2\left(s\right)*{{\stackrel{\‾}{U}}_d}^p\left(s\right))---\left(4\right)$

${{\stackrel{\‾}{U}}_d}^n\left(s\right)=\frac{{\mathrm{\ω}}_f}{s+{\mathrm{\ω}}_f}{U_d}^{*n}\left(s\right)=\frac{{\mathrm{\ω}}_f}{s+{\mathrm{\ω}}_f}({U_d}^n\left(s\right)-U_1\left(s\right)*{{\stackrel{\‾}{U}}_d}^p\left(s\right)-U_2\left(s\right)*{{\stackrel{\‾}{U}}_q}^p\left(s\right))---\left(5\right)$

* in formula (2)-(5) representes the convolution algorithm in the s territory,

With

Be respectively

Laplace transform in the s territory, U1 (s) and U1 (s) are respectively u ₁(t)=and cos (2 ω t), u ₂(t)=Laplace transform of sin (2 ω t) in the s territory, wherein U ₁(s) and U ₁(s) expression formula is:

$U_1\left(s\right)=\frac{s}{{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="HDA0000039886830000041.png,HDA0000039886830000042.png"\; state="\{\{state\}\}">s</figure-callout>}}^2+{\left(2\mathrm{\&omega;}\right)}^2},$ $U_2\left(s\right)=\frac{2\mathrm{\&omega;}}{s^2+{\left(2\mathrm{\&omega;}\right)}^2}---\left(6\right)$

Among the DDSRF-SPLL; Adopt pi regulator that the positive sequence feedback voltage

of decoupling zero network output is adjusted to zero; And then the acquisition mains frequency ω consistent with speed, ω is carried out integration obtain positive sequence lock phase angle

and lock angle

mutually with negative phase-sequence

In like manner; Lock mutually angle

according to positive sequence lock phase angle

and negative phase-sequence and utilize DDSRF-SPLL that three-phase grid brachium pontis electric current is carried out decoupling zero, can obtain forward-order current

the d axle of d axle and q axle and the negative-sequence current

of q axle

This shows, be that DDSRF-SPLL utilizes three-phase brachium pontis grid-connected current and electrical network three-phase voltage to obtain the positive sequence component and the negative sequence component of current on line side and the positive sequence component of voltage and negative sequence component in the embodiment of the invention.

For make above-mentioned purpose of the present invention, feature and advantage can be more obviously understandable, does detailed explanation below in conjunction with the accompanying drawing specific embodiments of the invention.

Referring to Fig. 3, this figure is cooperative control method embodiment one flow chart provided by the invention.

The cooperative control method that the total power blower fan current transformer low-voltage that the embodiment of the invention provides is passed through may further comprise the steps:

Steps A: judge that electrical network generation three-phase equilibrium is fallen or three-phase imbalance when falling by the positive sequence component of current line voltage and negative sequence component, the drive signal of the power switch tube device in the net side converter is forced to block;

In the present invention can be obtained using the DDSRF-SPLL positive sequence voltage component

and the negative sequence component

The positive sequence component of voltage and negative sequence component compared with predetermined value respectively can judge whether electrical network falls.When judging that electrical network falls, need block the drive signal of the power switch tube device in the net side converter.

Step B: judge by the positive sequence component of current line voltage and negative sequence component that electrical network falls and reach when stablize, remove pressure blockade to the drive signal of the power switch tube device in the net side converter;

Compare by the positive sequence component of electrical network and negative sequence component and predetermined value that can to judge whether electrical network falls stable; When electrical network falls when stablizing; Releasing is to the blockade of the drive signal of power switch tube device, and net side converter operate as normal realizes the control of ring in outer voltage and the grid-connected current.

Step C: judge that by the positive sequence component of current line voltage and negative sequence component electrical network by falling when beginning to recover, forces to block to the drive signal of the power switch tube device in the net side converter.

Step C and steps A are similar, are the processes of a transient state, the temporary transient net side converter that blocks.

Step D: when judging power system restoration to normal and stable, remove pressure blockade to the drive signal of the power switch tube device in the net side converter by the positive sequence component of current line voltage and negative sequence component;

In steps A-D, detect DC bus-bar voltage simultaneously, the stagnant ring value of the direct voltage of DC bus-bar voltage and setting is compared, whether the control crowbar circuit works.

The cooperative control method that the total power blower fan current transformer low-voltage that the embodiment of the invention provides is passed through carries out falling of line voltage and recovers stable judgement through DDSRF-SPLL; When line voltage is in the transient state fallen or during the transient state that rises, the drive signal of the power switch tube device of net side converter is carried out temporary transient pressure block; Fall stable or when recovering normal and stable when line voltage is in, remove blockade the drive signal of the power switch tube device of net side converter.Simultaneously, cooperate the low-voltage of the work realization net side converter of crowbar circuit to pass through.The present invention judges that through the positive sequence component and the negative sequence component of line voltage the different conditions of line voltage carries out Different control; And only be that the net side converter is controlled; The pusher side current transformer can normally move always, has reduced the wind energy conversion system that the generator electromagnetic torque pulsation brings and the mechanical stress of driving-chain.

Introduce the concrete realization of the cooperative control method that the embodiment of the invention provides in detail below in conjunction with Fig. 4.

Referring to Fig. 4, this figure is a cooperative control method theory diagram provided by the invention.

Need to prove, in the total power blower fan system, can use gear box, also can.

Be not described in detail for the interior ring control of the left side among Fig. 4 the pusher side circuit; Because this part is a prior art; And the improvement of the pusher side current transformer not being controlled in the present embodiment; Only the net side converter is controlled, the pusher side current transformer keeps normal operating conditions, still normal torque or the power signal of following the tracks of total control.

At first introduce the control of crowbar circuit below.

The idle criterion of said crowbar circuit is for passing through to detect DC bus-bar voltage u _DcControl crowbar circuit and whether work, be specially: DC bus-bar voltage u _DcLess than setting direct voltage minimum value u _{Dc_min}The criterion of said crowbar circuit work is: direct voltage is greater than setting direct voltage maximum u _{Dc_max}

It is understandable that the control of crowbar circuit runs through whole process, mainly is in order to protect DC bus-bar voltage in preset range.

Introduce control below to the net side converter.

DDSRF-SPLL is by the three-phase voltage u of electrical network _a, u _b, u _cObtain u _d ^p, u _q ^p, u _d ⁿ, and u _q ⁿ, obtain line voltage positive-negative sequence lock phase angle simultaneously

With

DDSRF-SPLL is by the three-phase grid brachium pontis current i of electrical network _a, i _b, i _cAnd

With Obtain the forward-order current of current on line side And negative-sequence current

Control to the net side converter comprises outer voltage control 400 and current inner loop control 500, introduces respectively below.

At first introduce the operation principle of outer voltage control module 400.

The input of outer voltage control 400 is the occasion that given DC bus-bar voltage

and given positive sequence reactive current

are incorporated into the power networks at unity power factor, and

generally is set at zero.

The q axle of outer voltage control module 400 branches into:

And u _DcStack is regulated through PI and is obtained positive sequence active current set-point

Calculating shown in formula (7);

With

The result who regulate to obtain through PI after the stack again with

Stack obtains V _q ^P*

$i_q^{p*}=(K_{\mathrm{vp}}+\frac{K_{\mathrm{vi}}}{s})(u_{\mathrm{dc}}^{*}-u_{\mathrm{dc}})---\left(7\right)$

K wherein _VpAnd K _ViBe respectively proportionality coefficient and the integral coefficient during PI regulates.

The d axle of outer voltage control module 400 branches into:

With

The result who regulate to obtain through PI after the stack with

The stack back obtains V again _d ^P*

The input variable of dq-α β coordinate system is V _q ^P*And V _d ^P*, the output variable of dq-α β coordinate system is u _{α _ p}And u _{β _ p}

Introduce the operation principle of current inner loop control module 500 below.

The q axle of current inner loop control module 500 branches into: given q axle negative-sequence current

With calculate

Stack is regulated through PI again, the result that PI regulates with

Stack obtains V _q ^N*

The d axle of current inner loop control module 500 branches into: given d axle negative-sequence current

With calculate Stack is regulated through PI again, the result that PI regulates with

Stack obtains V _d ^N*

In sum, obtain positive sequence active current set-point by outer voltage control module 400

Positive-negative sequence is meritorious to obtain positive sequence voltage control command V with the reactive current set-point via current inner loop control module 500 _q ^P*And V _d ^P*, negative sequence voltage control command V _q ^N*And V _d ^N*

With

Be the positive-negative sequence feedforward component of line voltage, be used for overcoming the system disturbance that power network fluctuation causes,

With Can be by u _d ^p, u _q ^p, u _d ⁿ, and u _q ⁿRespectively with u _DcRatio obtain, specifically can be referring to the computing module among Fig. 4 600.

With

And the feedforward decoupling zero of adopting positive sequence, negative phase-sequence coordinate system is respectively controlled and is produced correspondent voltage control command V _q ^P*, V _d ^P*, V _q ^N*And V _d ^N*, concrete computing formula is following:

Feedforward decoupling zero control algolithm in the positive-sequence coordinate system is:

$\left\{\begin{array}{c}{V_q}^{p*}={V_{g\_q}}^p-(K_{\mathrm{ip}}+\frac{K_{\mathrm{ii}}}{s})(i_q^{p*}-i_q^p)\\ {V_d}^{p*}={V_{g\_d}}^p-(K_{\mathrm{ip}}+\frac{K_{\mathrm{ii}}}{s})(i_d^{p*}-i_d^p)\end{array}\right.---\left(8\right)$

Feedforward decoupling zero control algolithm in the negative phase-sequence coordinate system is:

$\left\{\begin{array}{c}{V_q}^{n*}={V_{g\_q}}^n-(K_{\mathrm{ip}}+\frac{K_{\mathrm{ii}}}{s})(i_q^{n*}-i_q^n)\\ {V_d}^{n*}={V_{g\_d}}^n-(K_{\mathrm{ip}}+\frac{K_{\mathrm{ii}}}{s})(i_d^{n*}-i_d^n)\end{array}\right.---\left(9\right)$

Wherein, K _IpAnd K _IiBe respectively proportionality coefficient and the integral coefficient during PI regulates.Usually choose according to " single order is best " principle, to obtain best step response.

Using positive sequence current, negative-sequence current dual current-loop control system truly

and four completely independent current control.In practical matter; For guaranteeing to net the normal hanging net operation of side converter and three symmetrical controls of grid-connected current; Control net side negative-sequence current

and

and be zero, so given negative-sequence current

and is zero in the embodiment of the invention.

In order to improve the utilance of direct voltage, net side converter and pusher side current transformer all adopt the SVPWM modulation system.

As shown in Figure 4; SVPWM module 700 receives the output variable and the output variable of current inner loop control module 500 of outer voltage control modules 400, and and

thus export the power switch tube device of PWM drive net side converter.

Introduce the low-voltage of net side converter of the present invention below in conjunction with Fig. 5 in detail and pass through whole process.

Referring to Fig. 5, this figure is cooperative control method embodiment two flow charts provided by the invention.

S501: calculate the positive sequence component and the negative sequence component of line voltage in real time through DDSRF-SPLL, and positive sequence lock phase angle is locked angle mutually with negative phase-sequence;

Need to prove that DDSRF-SPLL is in real time at the positive sequence component and the negative sequence component that calculate line voltage, therefore, the positive sequence component of the line voltage that uses in each determining step and negative sequence component are current time collections.

S502: judge by the positive sequence component of line voltage and negative sequence component whether electrical network takes place that imbalance is fallen or balance is fallen, if then carry out S503; If, then do not carry out S504;

Need to prove,, judge that electrical network generation three-phase equilibrium falls when the positive sequence component of judging current line voltage during (for example less than 80% previous cycle line voltage amplitude) less than first scheduled voltage of the line voltage in previous cycle;

When the positive sequence component of judging current line voltage less than second scheduled voltage of the line voltage in previous cycle (for example; Line voltage amplitude less than 80% previous cycle); And when the negative sequence component of the negative sequence component of current line voltage and the line voltage in previous cycle differs predetermined amplitude (the line voltage amplitude in 10% previous cycle), judge that electrical network generation three-phase imbalance falls.

S503: the drive signal of power switch tube device of net side converter is forced to block;

S504: ring is regulated simultaneously in net side converter direct voltage outer shroud and the grid-connected current;

S505: it is stable to judge by the positive sequence component of current line voltage and negative sequence component whether electrical network falls; If then carry out S506; If, then do not carry out S503;

S506: remove the blockade of the drive signal of power switch tube device, the net side converter carries out current inner loop control with the maximum grid-connected current of setting, and this moment, the direct voltage outer shroud was in saturation condition.Regulate the amplitude limit value of net side converter direct voltage outer shroud pi regulator output, thereby the positive sequence active current that is incorporated into the power networks is limited in the maximum amplitude limit value scope;

S507: positive sequence component and negative sequence component by current line voltage judge whether electrical network recovers by falling stable the beginning; If then carry out S503; If, then do not carry out S506;

S508: positive sequence component and negative sequence component by current line voltage judge whether electrical network recovers stable; If then carry out S509, if not, then carry out S503;

S509: judge that whether crowbar circuit is in work, if then carry out S506; If, then do not carry out S504.

When line voltage by fall recover stable after; The positive sequence lock phase angle

of the line voltage that calculates according to DDSRF-SPLL is carried out current inner loop control (carry out current inner loop control with the maximum positive sequence grid-connected current of setting, the direct voltage outer shroud is not worked) or dc voltage stability control (direct voltage outer shroud and current inner loop are all regulated).The switching of two kinds of control models is according to being: in the moment of being incorporated into the power networks control, in working order whether crow bar.Work like crowbar circuit,, need net side converter this moment and be operated in the interior ring status of grid-connected current with the anti-process of irritating of the rectification of gauze screen side energy for suppressing crowbar circuit work from the electrical network absorbed power; If instead carry out moment of Current Regulation at the net side converter, crowbar circuit is work not, then nets side converter and just get into the dc voltage stability control procedure, thereby realize the low-voltage crossing process of one-period.

The cooperative control method that the low-voltage of the net side converter that the embodiment of the invention provides is passed through; Carry out Different control through analyzing the electrical network current states; When electrical network is in the falling process; And stable begin to recover in the normal processes by falling, all control net side converter is not worked, because these two processes are transient processes.When electrical network fell stable or recovers normal and stable, control net side converter hanging net operation was because these two processes are steady-state processs.

According to oscillogram, introduce the effect that cooperative control method provided by the invention produces below.

Referring to Fig. 6, this figure is net side converter response wave shape figure when to be that line voltage provided by the invention is single-phase fall.This figure is single-phase 20% of the rated voltage that drops into.Referring to Fig. 7, this figure is that line voltage two provided by the invention falls time net side converter response wave shape figure mutually.This figure two drops into 20% mutually.Referring to Fig. 8, this figure is that time net side converter response wave shape figure is fallen in line voltage three-phase equilibrium provided by the invention.This figure is that three-phase equilibrium drops into 20%.

U among the figure _ABBe grid voltage waveform, I _ABe the A phase current waveform, down be followed successively by the waveform of the triggering signal and the PWM drive signal of crowbar circuit.

Can find out that from Fig. 6-8 no matter which kind of fault electrical network is in and falls state, pass through moment of generation in low-voltage, through net side of the present invention, pusher side Collaborative Control, the responsive state of net side converter and the action implementation process shown in Fig. 4 are consistent.

(1) at t ₀-t ₁, and t ₂-t ₃Period, promptly line voltage fall with the transient process of recovering in, damage the power switch tube device in the current transformer in order to prevent overcurrent, the drive signal of the power switch tube device of net side converter has been carried out of short duration blockade.

(2) t ₁-t ₂Period; It is the steady-state process after electrical network drops into low pressure; Releasing is to the blockade of the drive signal of the power switch tube device of net side converter; And present energy with the maximum grid-connected current of setting to electrical network, crowbar circuit whether work be according to the direct voltage of DC bus-bar voltage and setting relatively the result control.

(3) t ₃After; The steady-state process that is power system restoration behind the high pressure, beginning is not because power matches and makes the crowbar circuit conducting that still is triggered, and net side converter and be operated in ring status in the grid-connected current this moment; When dc voltage drops to less than setting direct voltage minimum value; The crowbar circuit state of deactivating, the net side converter returns to the dc voltage stability control procedure before electrical network falls again, thereby has realized the low-voltage crossing process of one-period.

Referring to Fig. 9, pusher side response wave shape figure when this figure falls for the line voltage three-phase equilibrium.

U _UVLine voltage, I between generator unit stator U phase and the V phase _U, I _VBe respectively stator U phase and V phase current, U mutually _DCBe DC bus-bar voltage.

As can be seen from Figure 9, during low-voltage was passed through, because the off-load effect of crowbar circuit, the pusher side current transformer was not regulated especially, still followed the tracks of the torque or the power instruction generator operation of total control by normal condition.

Based on the cooperative control method that above-mentioned total power blower fan current transformer low-voltage is passed through, the cooperative control system that the present invention also provides blower fan current transformer low-voltage to pass through specifies its part below in conjunction with specific embodiment.

Referring to Figure 10, this figure is cooperative control system embodiment one structure chart provided by the invention.

The cooperative control system that the total power blower fan current transformer low-voltage that present embodiment provides is passed through comprises with lower unit:

Computing unit 1001 is used for calculating positive sequence component and the negative sequence component that obtains line voltage in real time by the three-phase voltage of current electrical network;

Computing unit utilizes DDSRF-SPLL can obtain the positive sequence component and the negative sequence component of line voltage, and concrete computing formula can be referring to the description of method embodiment part.

Fall judging unit 1002, the positive sequence component of the current line voltages that are used for being obtained in real time by computing unit 1001 and negative sequence component judge whether electrical network takes place that three-phase equilibrium is fallen or three-phase imbalance falls;

Fall stabilize decision unit 1003, the positive sequence component of the current line voltages that are used for being obtained in real time by computing unit 1001 and negative sequence component are judged whether electrical network falls and are reached stable;

Fall and recover judging unit 1004, be used for judging by the positive sequence component and the negative sequence component of the computing unit 1001 real-time current line voltages that obtain whether electrical network begins to recover by falling;

Recover normal judging unit 1005, be used for judging by the positive sequence component and the negative sequence component of the computing unit 1001 real-time current line voltages that obtain whether electrical network returns to normal and stable;

Drive signal is blocked unit 1006, is used for falling or three-phase imbalance when falling the drive signal of blocking the power switch pipe of netting side converter when electrical network generation three-phase equilibrium; Also be used for when electrical network by falling when beginning to recover, block the drive signal of the power switch pipe of net side converter;

Drive signal is removed unit 1007, is used for falling when stablize when electrical network, and releasing is to the blockade of the drive signal of the power switch tube device of netting side converter; Also be used for when power system restoration arrives normal and stable, releasing is to the blockade of the drive signal of the power switch tube device of net side converter;

Crowbar circuit control unit 1008 is used for DC bus-bar voltage and scheduled voltage are relatively controlled the work of crowbar circuit.Be specially: when DC bus-bar voltage less than setting the direct voltage minimum value, be used to control crowbar circuit and do not work; When DC bus-bar voltage greater than setting the direct voltage maximum, be used to control crowbar circuit work.

The cooperative control system that the total power blower fan current transformer low-voltage that the embodiment of the invention provides is passed through carries out falling of line voltage and recovers stable judgement through DDSRF-SPLL; When line voltage is in the transient state fallen or during the transient state that rises, the drive signal of the power switch tube device of net side converter is carried out temporary transient pressure block; Fall stable or when recovering normal and stable when line voltage is in, remove blockade the drive signal of the power switch tube device of net side converter.Simultaneously, cooperate the low-voltage of the work realization net side converter of crowbar circuit to pass through.The present invention judges that through the positive sequence component and the negative sequence component of line voltage the different conditions of line voltage carries out Different control; And only be that the net side converter is controlled; The pusher side current transformer can normally move always, has reduced the wind energy conversion system that the generator electromagnetic torque pulsation brings and the mechanical stress of driving-chain.

Referring to Figure 11, this figure is cooperative control system embodiment two structure charts provided by the invention.

The cooperative control system that the embodiment of the invention provides also comprises net side three-phase voltage transducer 1101, is used to gather the three-phase voltage of net side, and the three-phase voltage of the net side of gathering is sent to said computing unit.

The said judging unit 1002 that falls comprises that judgment sub-unit 1002a is fallen in three-phase equilibrium and three-phase imbalance falls judgment sub-unit 1002b;

Judgment sub-unit 1002a is fallen in said three-phase equilibrium; When being used for the positive sequence component of more current line voltage, judge that electrical network generation three-phase equilibrium falls less than first scheduled voltage of the line voltage in previous cycle (for example less than 80% previous cycle line voltage amplitude);

Said three-phase imbalance falls judgment sub-unit 1002b; The positive sequence component that is used for more current line voltage less than second scheduled voltage of the line voltage in previous cycle (for example; Line voltage amplitude less than 80% previous cycle); And when the negative sequence component of the negative sequence component of current line voltage and the line voltage in previous cycle differs predetermined amplitude (the line voltage amplitude in 10% previous cycle), judge that electrical network generation three-phase imbalance falls.

The cooperative control system that the low-voltage of the net side converter that the embodiment of the invention provides is passed through; Carry out Different control through analyzing the electrical network current states; When electrical network is in the falling process; And stable begin to recover in the normal processes by falling, all control net side converter is not worked, because these two processes are transient processes.When electrical network fell stable or recovers normal and stable, control net side converter hanging net operation was because these two processes are steady-state processs.

The above only is preferred embodiment of the present invention, is not the present invention is done any pro forma restriction.Though the present invention discloses as above with preferred embodiment, yet be not in order to limit the present invention.Any those of ordinary skill in the art; Do not breaking away under the technical scheme scope situation of the present invention; All the method for above-mentioned announcement capable of using and technology contents are made many possible changes and modification to technical scheme of the present invention, or are revised as the equivalent embodiment of equivalent variations.Therefore, every content that does not break away from technical scheme of the present invention, all still belongs in the scope of technical scheme protection of the present invention any simple modification, equivalent variations and modification that above embodiment did according to technical spirit of the present invention.

Claims (8)

1. the cooperative control method that total power blower fan current transformer low-voltage is passed through is characterized in that, may further comprise the steps:

Steps A: judge that electrical network generation three-phase equilibrium is fallen or three-phase imbalance when falling by the positive sequence component of current line voltage and negative sequence component, the drive signal of the power switch tube device in the net side converter is carried out of short duration pressure block;

Step B: judge by the positive sequence component of current line voltage and negative sequence component that electrical network falls and reach when stablize, remove blockade to the drive signal of netting the power switch tube device in the side converter;

Step C: judge that by the positive sequence component of current line voltage and negative sequence component electrical network by falling when beginning to recover, carries out of short duration blockade to the drive signal of the power switch tube device in the net side converter;

Step D: when judging power system restoration to normal and stable, remove blockade to the drive signal of netting the power switch tube device in the side converter by the positive sequence component of current line voltage and negative sequence component;

In steps A, B, C and D, control crowbar circuit through comparison DC bus-bar voltage and scheduled voltage and whether work.

2. cooperative control method according to claim 1 is characterized in that, the idle criterion of said crowbar circuit is: DC bus-bar voltage is less than setting the direct voltage minimum value; The criterion of said crowbar circuit work is: DC bus-bar voltage is greater than setting the direct voltage maximum.

3. cooperative control method according to claim 1 is characterized in that, the positive sequence component of said current line voltage and negative sequence component are calculated by the net side three-phase voltage of two synchronous coordinate system software phase-lock loops according to the voltage sensor collection.

4. cooperative control method according to claim 1 is characterized in that, when the positive sequence component of judging current line voltage during less than first scheduled voltage of the line voltage in previous cycle, judges that electrical network generation three-phase equilibrium falls in the steps A;

When second scheduled voltage of the positive sequence component of judging current line voltage less than the line voltage in previous cycle; And when the negative sequence component of the negative sequence component of current line voltage and the line voltage in previous cycle differs predetermined amplitude, judge that electrical network generation three-phase imbalance falls.

5. the cooperative control system that total power blower fan current transformer low-voltage is passed through is characterized in that, comprises with lower unit:

Computing unit is used for calculating positive sequence component and the negative sequence component that obtains line voltage in real time by the three-phase voltage of current electrical network;

Fall judging unit, the positive sequence component of the current line voltage that is used for being obtained in real time by computing unit and negative sequence component judge whether electrical network takes place that three-phase equilibrium is fallen or three-phase imbalance falls;

Fall the stabilize decision unit, the positive sequence component of the current line voltage that is used for being obtained in real time by computing unit and negative sequence component are judged whether electrical network falls and are reached stable;

Fall the recovery judging unit, be used for judging by the positive sequence component and the negative sequence component of the real-time current line voltage that obtains of computing unit whether electrical network begins to recover by falling;

Recover normal judging unit, be used for judging by the positive sequence component and the negative sequence component of the real-time current line voltage that obtains of computing unit whether electrical network returns to normal and stable;

Drive signal is blocked the unit, is used for falling or three-phase imbalance when falling the drive signal of blocking the power switch pipe of netting side converter when electrical network generation three-phase equilibrium; Also be used for when electrical network by falling when beginning to recover, block the drive signal of the power switch pipe of net side converter;

Drive signal is removed the unit, is used for falling when stablize when electrical network, and releasing is to the blockade of the drive signal of the power switch tube device of netting side converter; Also be used for when power system restoration arrives normal and stable, releasing is to the blockade of the drive signal of the power switch tube device of net side converter;

The crowbar circuit control unit is used for DC bus-bar voltage and scheduled voltage are relatively controlled the work of crowbar circuit.

6. cooperative control system according to claim 5 is characterized in that, said crowbar circuit control unit, when DC bus-bar voltage less than setting the direct voltage minimum value, be used to control crowbar circuit and do not work; When DC bus-bar voltage greater than setting the direct voltage maximum, be used to control crowbar circuit work.

7. cooperative control system according to claim 5 is characterized in that, also comprises net side three-phase voltage transducer, is used to gather the three-phase voltage of net side, and the three-phase voltage of the net side of gathering is sent to said computing unit.

8. cooperative control system according to claim 5 is characterized in that, the said judging unit that falls comprises that judgment sub-unit is fallen in three-phase equilibrium and three-phase imbalance falls judgment sub-unit;

Judgment sub-unit is fallen in said three-phase equilibrium, and the positive sequence component that is used for more current line voltage is during less than first scheduled voltage of the line voltage in previous cycle, judges that electrical network generation three-phase equilibrium falls;

Said three-phase imbalance falls judgment sub-unit; Be used for second scheduled voltage of more current line voltage positive sequence component less than the line voltage in previous cycle; And when the negative sequence component of the negative sequence component of current line voltage and the line voltage in previous cycle differs predetermined amplitude, judge that electrical network generation three-phase imbalance falls.

Images