CN104319813B - Off-network type wind power system two electromotor cascade operation control system and method - Google Patents

Abstract

The invention belongs to off-network type permanent magnetism wind power system and run control field, be incorporated into the power networks for realizing two electromotors simultaneously, while expanding power system capacity, expand electromotor speed adjustable range.To this end, the present invention adopts the technical scheme that, off-network type wind power system two electromotor cascade operation control system and method, structure is: two permanent-magnetic wind driven generators, and every generator unit stator connects uncontrollable rectifier circuit；Often set uncontrollable rectifier circuit is followed by a set of boost chopper；Often set boost chopper includes a boost inductance, a boosting power switch pipe and a fast recovery diode.And step one, by permanent-magnetic wind driven generator principle, and analyze current commutation process, obtaining uncontrollable rectifier circuit output voltage meansigma methods is: step 2, calculate boosting power switch pipe dutycycle under boost chopper series and parallel state respectively；Step 3, hysteresis control method thereof.Present invention is mainly applied to permanent magnetism wind power system and run control.

Description

Off-network type wind power system two electromotor cascade operation control system and method

Technical field

The invention belongs to off-network type permanent magnetism wind power system and run control field, relate to the correlation technique of field of power electronics.Specifically, Relate to off-network type wind power system two electromotor cascade operation control system and method.

Technical background

China is vast in territory, with a varied topography, and outlying pastoral area, rural area, island and frontier sentry etc. exist user's dispersion, use The features such as electricity is relatively small.Off-network type wind power system has the advantages such as convenient, with low cost, the flexible form of erection, can be relatively Meet well the need for electricity in above-mentioned area, thus be used widely.Along with expanding economy, residential electricity consumption equipment is increasingly Many, power consumption increases the most year by year.Original off-network type wind power system capacity is difficult to meet the need for electricity of resident, as abandoned former system Unite and use the wind power system of novel larger capacity, bigger waste can be caused；Simple series/parallel can limit again the operation of electromotor Scope, therefore off-network type wind power system increase-volume problems demand solves.The most single set off-network type wind power system design and control method side The document in face is more, but many cover systems cascade method of being incorporated into the power networks is had no report.

Summary of the invention

For overcoming the deficiencies in the prior art, it is achieved two electromotors are incorporated into the power networks simultaneously, while expanding power system capacity, expand and send out Electric machine speed regulation scope.To this end, the present invention adopts the technical scheme that, the cascade of off-network type wind power system two electromotor runs and controls system System, structure is: two permanent-magnetic wind driven generators, and every generator unit stator connects uncontrollable rectifier circuit；Often after set uncontrollable rectifier circuit Connect a set of boost chopper；Often set boost chopper includes a boost inductance, a boosting power switch pipe and one Fast recovery diode, described boost inductance is connected on input positive pole and the boosting power switch pipe forward of this boost chopper Between conducting input, described fast recovery diode anode is connected with boosting power switch pipe forward conduction input, negative electrode It is connected with the output cathode of this boost chopper；The output cathode of the 1st set boost chopper and the 2nd set boost chopper Output negative pole be connected with storage capacitor both positive and negative polarity respectively, two set boost choppers outfans opened by a change of current power Pass pipe is connected in series, and its connected mode is, the output negative pole of the 1st set circuit and change of current power switch pipe forward conduction outfan Connecting, the output cathode of the 2nd set circuit is connected with change of current power switch pipe forward conduction input；1st set boost chopper electricity The input negative pole of the input negative pole on road and the 2nd set boost chopper is connected by a level combination diode, and this level is combined two poles The input negative pole of the negative electrode of pipe and the 1st set circuit connects, and the input negative pole of anode and the 2nd set circuit connects；1st set boosting is cut The boosting of wave circuit power switch pipe forward conduction input and the boosting power switch pipe forward of the 2nd set boost chopper Connecting also by a level combination diode between conducting input, the boosting of this grade of combination diode cathode and the 1st set circuit is used Power switch pipe forward conduction input connects, and the boosting of anode and the 2nd set circuit is with power switch pipe forward conduction input even Connect.

Off-network type wind power system two electromotor cascade progress control method, realizes by means of aforementioned means, and comprises the steps:

Step one, by permanent-magnetic wind driven generator principle, and analyze current commutation process, obtain uncontrollable rectifier circuit output voltage average Value is:

$\left\{\begin{array}{c}{U}_{1d}=\frac{3\sqrt{6}}{\mathrm{\π}}{K}_e{\mathrm{\ω}}_1-{2V}_{\mathrm{diode}}-\frac{3}{\sqrt{6}}{\mathrm{\ω}}_1{L}_s{I}_{1s}\\ U_{2d}=\frac{3\sqrt{6}}{\mathrm{\π}}{K}_e{\mathrm{\ω}}_2-{2V}_{\mathrm{diode}}-\frac{3}{\sqrt{6}}{\mathrm{\ω}}_2{L}_s{I}_{2s}\end{array}\right.$

In formula, U_1d、U_2dIt is respectively two set uncontrollable rectifier circuit output voltage meansigma methodss；ω₁、ω₂It is respectively two generator speeds； I_1s、I_2sIt is respectively two electromotor phase current virtual values；K_eFor back emf coefficient；V_diodeFor uncontrollable rectifier circuit diode pipe pressure Fall；L_sFor generator unit stator phase inductance；

Under step 2, respectively calculating boost chopper series and parallel state, power switch pipe dutycycle is used in boosting

Uncontrollable rectifier circuit output voltage meansigma methods and boost chopper output voltage average value can be obtained by boost chopper principle Between relation be

$\left\{\begin{array}{c}{U}_{1\mathrm{dc}}=\frac{1}{{1-d}_1}{U}_{1d}\\ U_{2\mathrm{dc}}\frac{1}{{1-d}_2}{U}_{2d}\end{array}\right.$

In formula, U_1dc、U_2dcIt is respectively two set boost chopper output voltage average values；d₁、d₂It is respectively two boosting power to open Close the dutycycle of pipe.

When two set boost choppers are in series connection, DC capacitor voltage is

U_dc=U_1dc+U_2dc

In formula, U_dcFor DC capacitor voltage.

When two set boost choppers are in parallel connection, DC capacitor voltage is

U_dc=U_1dc=U_2dc

I.e. approximate calculation the boosting power switch pipe dutycycle under different rotating speeds, different cascade system can be gone out by above formula；

Step 3, hysteresis control method thereof

In initialization system, by bound and calculated dutycycle, boosting power switch pipe dutycycle bound, determines that state is cut Change critical speed；Dutycycle under calculated different rotating speeds compared with upper lower limit value, under series system, when calculating When the dutycycle arrived is less than lower limit, this rotating speed i.e. for being switched to critical speed ω of parallel way by series system_max；In parallel connection Under mode, when calculated dutycycle is higher than higher limit, this rotating speed is i.e. for be switched to the critical of series system by parallel way Rotational speed omega_min；

When wind speed is relatively low, generator speed compared with slow, terminal voltage is relatively low, make change of current power switch pipe turn on, make system work In series connection, to meet the inverter requirement to DC capacitor voltage；When wind speed raises, generator speed raises, end Voltage is higher, and two generator speeds all exceed critical speed ω_maxTime, make change of current power switch pipe turn off, make system work In parallel connection, it is ensured that stablizing of DC capacitor voltage, avoid boosting power switch pipe simultaneously and limit dutycycle occurs； When wind speed reduces, two generator speeds are below critical speed ω_minTime, make change of current power switch pipe turn on, make system Come back to series connection.

Make ω_max>ω_minSo that algorithm has stagnant ring function, when wind speed the most frequently vibrates, it is to avoid frequent switched system The situation of series and parallel state.

Compared with the prior art, the technical characterstic of the present invention and effect:

The present invention proposes a kind of off-network type wind power system two electromotor cascade progress control method, with two permanent-magnetic wind driven generators, Two set uncontrollable rectifier circuit, two set boost choppers and related peripheral device are hardware foundation, use Hysteresis control algorithm to realize Two electromotors are incorporated into the power networks simultaneously, thus can be effectively increased power system capacity, and extend electromotor speed adjustable range；Can make simultaneously Boosting power switch pipe dutycycle runs in zone of reasonableness, reduces higher hamonic wave, improves systematic function.

Accompanying drawing explanation

Fig. 1 off-network of the present invention type wind power system block diagram.

Fig. 2 electromotor and uncontrollable rectifier circuit equivalent circuit diagram.

Fig. 3 electric current shifts to the process of a phase from c phase.

Detailed description of the invention

For off-network type wind power system increase-volume problem, it is proposed that a kind of off-network type wind power system two electromotor cascade progress control method, With two permanent-magnetic wind driven generators, two set uncontrollable rectifier circuit, two set boost choppers and related peripheral device as hardware foundation, Use Hysteresis control algorithm to realize two electromotors to be incorporated into the power networks simultaneously, while expanding power system capacity, expand electromotor speed governing Scope.The technical solution used in the present invention is:

Step one, approximate calculation uncontrollable rectifier circuit output voltage meansigma methods

System concrete structure is: two permanent-magnetic wind driven generators, and every generator unit stator connects uncontrollable rectifier circuit；Often overlap do not control whole Current circuit is followed by a set of boost chopper；Often set boost chopper includes a boost inductance, a boosting power switch Pipe and a fast recovery diode, described boost inductance is connected on the input positive pole of this boost chopper and opens with boosting power Closing between pipe forward conduction input, described fast recovery diode anode is with boosting power switch pipe forward conduction input even Connecing, negative electrode is connected with the output cathode of this boost chopper；The output cathode of the 1st set boost chopper and the 2nd set boosting The output negative pole of chopper circuit is connected with storage capacitor both positive and negative polarity respectively, and the outfan of two set boost choppers is by a change of current Being connected in series with power switch pipe, its connected mode is, the output negative pole of the 1st set circuit and the positive guide of change of current power switch pipe Logical outfan connects, and the output cathode of the 2nd set circuit is connected with change of current power switch pipe forward conduction input；1st set rises The input negative pole of pressure chopper circuit and the input negative pole of the 2nd set boost chopper are connected by a level combination diode, this level The negative electrode of combination diode and the input negative pole of the 1st set circuit connect, and the input negative pole of anode and the 2nd set circuit connects；1st The boosting power switch pipe forward conduction input of set boost chopper and the boosting power of the 2nd set boost chopper are opened Close and connect also by a level combination diode between pipe forward conduction input, this level combination diode cathode and the 1st set circuit Boosting with power switch pipe forward conduction input connect, anode with the 2nd overlap circuit boosting power switch pipe forward conduction Input connects.

By permanent-magnetic wind driven generator principle, and analyze current commutation process, generator speed and uncontrollable rectifier circuit output electricity can be obtained The relation flattened between average is

$\left\{\begin{array}{c}{U}_{1d}=\frac{3\sqrt{6}}{\mathrm{\π}}{K}_e{\mathrm{\ω}}_1-{2V}_{\mathrm{diode}}-\frac{3}{\sqrt{6}}{\mathrm{\ω}}_1{L}_s{I}_{1s}\\ U_{2d}=\frac{3\sqrt{6}}{\mathrm{\π}}{K}_e{\mathrm{\ω}}_2-{2V}_{\mathrm{diode}}-\frac{3}{\sqrt{6}}{\mathrm{\ω}}_2{L}_s{I}_{2s}\end{array}\right.$

In formula, U_1d、U_2dIt is respectively two set uncontrollable rectifier circuit output voltage meansigma methodss；ω₁、ω₂It is respectively two generator speeds； I_1s、I_2sIt is respectively two electromotor phase current virtual values；K_eFor back emf coefficient；V_diodeFor uncontrollable rectifier circuit diode pipe pressure Fall；L_sFor generator unit stator phase inductance.

Under step 2, respectively calculating boost chopper series and parallel state, power switch pipe dutycycle is used in boosting

Uncontrollable rectifier circuit output voltage meansigma methods and boost chopper output voltage average value can be obtained by boost chopper principle Between relation be

$\left\{\begin{array}{c}{U}_{1\mathrm{dc}}=\frac{1}{{1-d}_1}{U}_{1d}\\ U_{2\mathrm{dc}}\frac{1}{{1-d}_2}{U}_{2d}\end{array}\right.$

In formula, U_1dc、U_2dcIt is respectively two set boost chopper output voltage average values；d₁、d₂It is respectively two boosting power to open Close the dutycycle of pipe.

When two set boost choppers are in series connection, DC capacitor voltage is

U_dc=U_1dc+U_2dc

In formula, U_dcFor DC capacitor voltage.

When two set boost choppers are in parallel connection, DC capacitor voltage is

U_dc=U_1dc=U_2dc

Approximate calculation the boosting power switch pipe dutycycle under different rotating speeds, different cascade system can be gone out by above formula.

Step 3, hysteresis control method thereof

In initialization system, by bound and calculated dutycycle, boosting power switch pipe dutycycle bound, determines that state is cut Change critical speed.Dutycycle under calculated different rotating speeds compared with upper lower limit value, under series system, when calculating When the dutycycle arrived is less than lower limit, this rotating speed i.e. for being switched to critical speed ω of parallel way by series system_max；In parallel connection Under mode, when calculated dutycycle is higher than higher limit, this rotating speed is i.e. for be switched to the critical of series system by parallel way Rotational speed omega_min。

When wind speed is relatively low, generator speed compared with slow, terminal voltage is relatively low, make change of current power switch pipe turn on, make system work In series connection, to meet the inverter requirement to DC capacitor voltage；When wind speed raises, generator speed raises, end Voltage is higher, and two generator speeds all exceed critical speed ω_maxTime, make change of current power switch pipe turn off, make system work In parallel connection, it is ensured that stablizing of DC capacitor voltage, avoid boosting power switch pipe simultaneously and limit dutycycle occurs； When wind speed reduces, two generator speeds are below critical speed ω_minTime, make change of current power switch pipe turn on, make system Come back to series connection.In the algorithm, ω is made_max>ω_minSo that algorithm has stagnant ring function, when wind speed the most frequently shakes When swinging, it is to avoid the situation of frequent switched system series and parallel state.

The present invention is further described below in conjunction with the accompanying drawings with instantiation.

The present invention is applicable to outside the Pass by two permanent-magnetic wind driven generators, two set uncontrollable rectifier circuit, two set boost choppers and phase The off-network type wind power system of peripheral device composition.Below in conjunction with concrete example and accompanying drawing, the present invention is further described.Example is adopted Electromotor quantity be 2 (electromotor 1 and electromotors 2), processor uses the TMS320F28335 single of TI company Sheet is controlled.System block diagram as it is shown in figure 1, in figure, U_1d、U_2dFor uncontrollable rectifier circuit output voltage meansigma methods；U_1dc、 U_2dcFor boost chopper output voltage average value；U_dcFor DC capacitor voltage；S₁、S₂For boosting power switch pipe； S₃For change of current power switch pipe；D₁、D₂For fast recovery diode；D₃、D₄It is combined diode for level；L₁、L₂For a liter piezoelectricity Sense.

(1) when electromotor low cruise, controller gathers wind speed information, maximal wind-energy capture principle calculate electromotor reference Rotational speed omega_1refAnd ω_2ref。

(2) approximate calculation uncontrollable rectifier circuit output voltage meansigma methods, concrete calculating process is as follows:

As a example by the 1st electromotor, ignore generator unit stator resistance, using electromotor and uncontrollable rectifier circuit as an entirety, Equivalent circuit can be obtained as shown in Figure 2.In figure, u_1a、u_1b、u_1cFor generator voltage；e_1a、e_1b、e_1cContrary for electromotor Electromotive force, i_1a、i_1b、i_1cFor generator unit stator phase current；L_sFor generator unit stator inductance；U_1dFor uncontrollable rectifier circuit output voltage Meansigma methods；I_1dFor uncontrollable rectifier circuit output current meansigma methods；D₁₁～D₁₆For uncontrollable rectifier circuit diode；A point, b point, c Point is electromotor opposite potential output point；N point is generator unit stator winding neutral point.According to magneto operation logic, Electromotor opposite potential virtual value is represented by

$E_{1s}=\frac{1}{\sqrt{2}}{p}_1{\mathrm{\ω}}_1{\mathrm{\Ψ}}_{1f}=K_e{\mathrm{\ω}}_1---\left(1\right)$

In formula, E_1SFor electromotor opposite potential virtual value, p₁For power generator electrode logarithm, ω₁For generator speed, Ψ_1fFor rotor flux, K_eFor back emf coefficient.

In uncontrollable rectifier circuit work process, owing to generator unit stator exists inductance, therefore current commutation process cannot be instantaneous complete Become.In three-phase equilibrium circuit, each commutation situation is the most identical, and we study electric current by electric current as a example by c phase shifts to a phase herein Commutation process, equivalent circuit that commutation process is relevant and curent change situation are as shown in Figure 3.In figure, i_1dFor uncontrollable rectifier electricity Road output current instantaneous value；u_1commFor the voltage difference that a phase and c are alternate；i_1mFor a phase and the loop current in c phase composition loop； u_1La、u_1LcFor a, c phase stator inductance voltage；u_1an、u_1bn、u_1cnFor the voltage difference between a point, b point, c point and n point； P point, N point are respectively uncontrollable rectifier circuit output positive and negative electrode；u_1Pn、u_1NnFor the voltage difference between P point, N point and n point； T is the time；0～m is commutation process；Area A_1mIntegral result for commutation drop-off voltage.

In the process, from the beginning of the t=0 moment (initial time is optional), electric current is from D₁₅Shift to D₁₁, before this, electric current i_1dFlow through D₁₅And D₁₆。

In commutation process, do not consider that the voltage difference that uncontrollable rectifier circuit diode tube voltage drop, a phase and c are alternate is u_1comm= u_1an-u_1cn, D₁₅And D₁₁Simultaneously turn on the loop current i in composition loop_1m, circuit theory can obtain

$\left\{\begin{array}{c}{i}_{1m}=i_{1a}\\ i_{1c}=I_{1d}-i_{1m}\end{array}\right.---\left(2\right)$

As t=m, commutation process terminates, electric current i_1mI is increased to from 0_1d, as shown in Fig. 3 (b), a phase stator inductance voltage For

u_1La=L_sdi_1a/ dt=L_sdi_1m/dt (3)

In formula, d is differential operator.

If I_1dKeep constant in commutation course, then c phase stator inductance voltage is

u_1Lc=L_sdi_1c/ dt=-L_sdi_1m/dt (4)

A phase in equivalent circuit shown in Fig. 3 (a) and c phase composition loop are applied KVL law, and by formula (3) and formula (4) Can obtain

$u_{1\mathrm{comm}}=u_{1\mathrm{an}}-u_{1\mathrm{cn}}=u_{1\mathrm{La}}-u_{1\mathrm{Lc}}={2L}_s\frac{{\mathrm{di}}_{1m}}{\mathrm{dt}}---\left(5\right)$

Arrange above formula further can obtain

$L_s\frac{{\mathrm{di}}_{1m}}{\mathrm{dt}}=\frac{u_{1\mathrm{an}}-u_{1\mathrm{cn}}}{2}---\left(6\right)$

Within 0～m commutation time period, above formula both sides integration can be obtained

${\mathrm{\ω}}_1{L}_s{\∫}_0^{I_{1d}}{\mathrm{di}}_{1m}={\text{\∫}}_0^m\frac{u_{1\mathrm{an}}-u_{1\mathrm{cn}}}{2}d\left({\mathrm{\ω}}_{1}t\right)---\left(7\right)$

Generator unit stator line back-emf can be expressed as

$u_{1\mathrm{an}}=u_{1\mathrm{cn}}=\sqrt{6}{E}_{1s}\sin {\mathrm{\ω}}_{1}t---\left(8\right)$

Formula (8) is substituted into formula (7), and can be calculated

${\mathrm{\ω}}_1{L}_s{L}_{1d}=\frac{\sqrt{6}{E}_{1s}(1-\cos m)}{2}---\left(9\right)$

Arrange further and can obtain

$\cos m=1-\frac{{2\mathrm{\ω}}_1{L}_s{I}_{1d}}{\sqrt{6}{E}_{1s}}---\left(10\right)$

By Fig. 3 (c) it can be seen that have u at the initial time of current commutation_1Pn=u_1an.In commutation process, i.e. 0 < t is < during m Between in section, Fig. 3 (c) and formula (6) can obtain

$u_{1\mathrm{Pn}}=u_{1\mathrm{an}}-u_{1\mathrm{La}}=\frac{u_{1\mathrm{an}}+u_{1\mathrm{cn}}}{2}---\left(11\right)$

In formula, u_1LaEqual to voltage u during commutation_1PnFall part, as shown in Fig. 3 (c).The integral result of commutation drop-off voltage For area A_1m, formula (7) can obtain

A_1m=ω₁L_sI_1d (12)

The area A fallen_1mEvery 60 ° of electrical angles occur once, and therefore uncontrollable rectifier circuit output voltage meansigma methods will reduce, and change Phase drop-off voltage is

${\mathrm{\&Delta;u}}_{1d}=\frac{{\mathrm{\&omega;}}_1{L}_s{I}_{1d}}{\mathrm{\&pi;}/3}=\frac{3}{\mathrm{\&pi;}}{\mathrm{\&omega;}}_1{L}_s{I}_{1d}---\left(13\right)$

In formula, △ u_1dFor commutation drop-off voltage.

Therefore, the uncontrollable rectifier circuit output voltage meansigma methods during each commutation is

$U_{1d}=U_{1d0}-{\mathrm{\&Delta;u}}_{1d}=\frac{3\sqrt{6}}{\mathrm{\&pi;}}{E}_{1s}-\frac{3}{\mathrm{\&pi;}}{\mathrm{\&omega;}}_1{L}_s{I}_{1d}---\left(14\right)$

In formula, U_1d0It it is preferable uncontrollable rectifier circuit output voltage meansigma methods.

I in formula (14)_1dWith the relation of electromotor phase current virtual value it is

$I_{1s}=\frac{\sqrt{6}}{\mathrm{\&pi;}}{I}_{1d}---\left(15\right)$

In formula, I_1sFor electromotor phase current virtual value.

Formula (15) is substituted in formula (14), and considers uncontrollable rectifier circuit diode tube voltage drop V_diode, then uncontrollable rectifier circuit Output voltage average value is

$U_{1d}=\frac{3\sqrt{6}}{\mathrm{\&pi;}}{E}_{1s}-{2V}_{\mathrm{diode}}-\frac{3}{\sqrt{6}}{\mathrm{\&omega;}}_1{L}_s{I}_{1s}---\left(16\right)$

Formula (1) substitution above formula can be obtained

$U_{1d}=\frac{3\sqrt{6}}{\mathrm{\&pi;}}{K}_e{\mathrm{\&omega;}}_1{-2V}_{\mathrm{diode}}-\frac{3}{\sqrt{6}}{\mathrm{\&omega;}}_1{L}_s{I}_{1s}---\left(17\right)$

In like manner, another electromotor also has similar mathematical relationship with uncontrollable rectifier circuit.Thus approximate calculation can go out and not control Output Voltage in Rectified Circuits meansigma methods.

(3) critical speed ω is determined_maxAnd ω_min。

Uncontrollable rectifier circuit output voltage meansigma methods and boost chopper output voltage average value can be obtained by boost chopper principle Between relation be

$\left\{\begin{array}{c}{U}_{1\mathrm{dc}}=\frac{1}{{1-d}_1}{U}_{1d}\\ U_{2\mathrm{dc}}=\frac{1}{{1-d}_2}{U}_{2d}\end{array}\right.---\left(18\right)$

In formula, d₁、d₂It is respectively the dutycycle of two boosting power switch pipes.

When two set boost choppers are in series connection, DC capacitor voltage is

U_dc=U_1dc+U_2dc (19)

When two set boost choppers are in parallel connection, DC capacitor voltage is

U_dc=U_1dc=U_2dc (20)

Approximate calculation boosting power switch pipe dutycycle under different rotating speeds, different cascade system can be gone out by formula (1)～(20).

Pre-set boosting power switch pipe dutycycle bound, upper and lower with this for dutycycle under calculated different rotating speeds Limit value compares, and under series system, when calculated dutycycle is less than lower limit, this rotating speed is i.e. for be cut by series system Shift to critical speed ω of parallel way_max；Under parallel way, when calculated dutycycle is higher than higher limit, this rotating speed I.e. for being switched to critical speed ω of series system by parallel way_min。

(4) boosting power switch tube S is regulated respectively₁And S₂Dutycycle, make electromotor actual speed continuous convergence reference rotation velocity. Now change of current power switch tube S₃In the conduction state, two set boost choppers are operated in series system, DC voltage Shown in mathematical relationship such as formula (19), S₁And S₂Dutycycle is bigger.

(5) gradually rise along with two generator speeds, S₁And S₂Dutycycle constantly reduces, when generator speed rises to critical turn Speed ω_maxTime, change of current power switch tube S₃Disconnecting, two set boost choppers are operated in parallel way, the number of DC voltage Shown in relation such as formula (20), S₁And S₂Dutycycle comes back to bigger numerical value.

(6) when electromotor is by during at a high speed to low cruise, S₁And S₂Dutycycle constantly increases, when generator speed is down to critical turn Speed ω_minTime, change of current power switch tube S₃Conducting, two set boost choppers are come back to series system by parallel way, with Ensure S₁And S₂Dutycycle is always positioned at suitable numerical value, keeps system stable operation.

Although above in conjunction with figure, invention has been described, but the invention is not limited in above-mentioned detailed description of the invention, on The detailed description of the invention stated is only schematic rather than restrictive, those of ordinary skill in the art's opening in the present invention Under showing, without deviating from the spirit of the invention, it is also possible to make many variations, within these belong to the protection of the present invention.

Claims (2)

1. an off-network type wind power system two electromotor cascade progress control method, is characterized in that, realize by means of following system, and comprise the steps；

System is:

Two permanent-magnetic wind driven generators, every generator unit stator connects uncontrollable rectifier circuit；Often set uncontrollable rectifier circuit is followed by a set of boost chopper；Often set boost chopper includes a boost inductance, a boosting power switch pipe and a fast recovery diode, described boost inductance is connected between the input positive pole of this boost chopper and boosting power switch pipe forward conduction input, described fast recovery diode anode is connected with boosting power switch pipe forward conduction input, and negative electrode is connected with the output cathode of this boost chopper；The output cathode of the 1st set boost chopper and the output negative pole of the 2nd set boost chopper are connected with storage capacitor both positive and negative polarity respectively, the outfan of two set boost choppers is connected in series by a change of current power switch pipe, its connected mode is, the output negative pole of the 1st set boost chopper is connected with change of current power switch pipe forward conduction outfan, and the output cathode of the 2nd set boost chopper is connected with change of current power switch pipe forward conduction input；The input negative pole of the 1st set boost chopper and the input negative pole of the 2nd set boost chopper are by a level combination diode D₄Connect, this level combination diode D₄Negative electrode and the 1st set boost chopper input negative pole connect, anode with the 2nd set boost chopper input negative pole connection；The boosting of the 1st set boost chopper is combined diode D also by a level between the boosting power switch pipe forward conduction input with power switch pipe forward conduction input and the 2nd set boost chopper₃Connect, this level combination diode D₃The boosting of negative electrode and the 1st set boost chopper connects with power switch pipe forward conduction input, and the boosting power switch pipe forward conduction input Connection Step of anode and the 2nd set boost chopper is:

Step one, by permanent-magnetic wind driven generator principle, and analyze current commutation process, obtaining uncontrollable rectifier circuit output voltage meansigma methods is

In formula, U_1d、U_2dIt is respectively two set uncontrollable rectifier circuit output voltage meansigma methodss；ω₁、ω₂It is respectively two generator speeds；I_1s、I_2sIt is respectively two electromotor phase current virtual values；K_eFor back emf coefficient；V_diodeFor uncontrollable rectifier circuit diode tube voltage drop；L_sFor generator unit stator phase inductance；

Under step 2, respectively calculating boost chopper series and parallel state, power switch pipe dutycycle is used in boosting

The relation that can be obtained between uncontrollable rectifier circuit output voltage meansigma methods and boost chopper output voltage average value by boost chopper principle is

In formula, U_1dc、U_2dcIt is respectively two set boost chopper output voltage average values；d₁、d₂It is respectively the dutycycle of two boosting power switch pipes；

When two set boost choppers are in series connection, DC capacitor voltage is

U_dc=U_1dc+U_2dc

In formula, U_dcFor DC capacitor voltage；

When two set boost choppers are in parallel connection, DC capacitor voltage is

U_dc=U_1dc=U_2dc

I.e. approximate calculation the boosting power switch pipe dutycycle under different rotating speeds, different cascade system can be gone out by above formula；

Step 3, hysteresis control method thereof

By dutycycle bound and calculated dutycycle, boosting power switch pipe dutycycle bound in initialization system, determines that state switches critical speed；Dutycycle under calculated different rotating speeds compared with dutycycle bound, under series system, when calculated dutycycle is less than dutycycle lower limit, this rotating speed i.e. for being switched to critical speed ω of parallel way by series system_max；Under parallel way, when calculated dutycycle is higher than the dutycycle upper limit, this rotating speed i.e. for being switched to critical speed ω of series system by parallel way_min；

When wind speed is relatively low, generator speed compared with slow, terminal voltage is relatively low, make change of current power switch pipe turn on, make system work in series connection, to meet the inverter requirement to DC capacitor voltage；When wind speed raises, generator speed raises, and terminal voltage is higher, and two generator speeds all exceed critical speed ω_maxTime, make change of current power switch pipe turn off, make system work in parallel connection, it is ensured that stablizing of DC capacitor voltage, avoid boosting power switch pipe simultaneously and limit dutycycle occurs；When wind speed reduces, two generator speeds are below critical speed ω_minTime, make change of current power switch pipe turn on, make system come back to series connection.

2. off-network type wind power system two electromotor cascade progress control method as claimed in claim 1, is characterized in that, make ω_max>ω_minSo that algorithm has stagnant ring function, when wind speed the most frequently vibrates, it is to avoid the situation of frequent switched system series and parallel state.