CN102420560A - Excitation structure and alternating-current and direct-current excitation control method for frequency-variable alternating-current starting power generation system - Google Patents

Abstract

The invention discloses an excitation structure and an AC and DC excitation control method for a variable frequency AC starting power generation system. The excitation structure is composed of an open-circuit stator three-phase winding and a three-phase bridge converter connected at both ends. The method starts the initial process, coordinates and controls the output vectors of each converter, selects a suitable comprehensive voltage vector, and generates the required three-phase AC excitation voltage in the three-phase winding, so that the exciter works at the rated output state, and the main generator Sufficient excitation current is provided for starting operation; when the motor speed reaches the excitation switching point, the three-phase AC excitation mode is switched to DC excitation according to the speed feedback signal. The switching process does not need to change the structure of the exciter winding through an external switch. Two sets of The bridge arm of the converter adopts a direct control method for the winding current of each phase, and the three-phase AC winding is equivalent to a DC series structure to realize the DC excitation function.

Description

Frequency-changing AC starting-generating system's excitation structure and AC and DC excitation control method

Technical field

The present invention relates to winding construction, converter design and the control technology of exciter in the frequency-changing AC starter-generator, belong to Motor Control Field.

Background technology

Continuous development along with the airplane power source technology; Large Civil Aircraft power supply system just transits to frequency-changing AC power supply system from existing constant-speed and constant-frequency, speed change constant speed gradually; Variable frequency AC power system is directly given back level electric through brushless AC generator; Can effectively improve the capacity and the efficient of electricity generation system; And can directly adopt distribution element, accessory power supply, APU generator and emergency power supply in the power-supply system of constant frequency 400Hz, the various load in can the be compatible existing constant frequency power system, so frequency-converting power supply is just becoming the first-selection when nearly large-scale civil aircraft power-supply system.The state-of-the-art large-scale civil aircraft such as the A380 of Air Passenger company, the B787 of Boeing adopt this variable frequency AC power system just at present, have formed the high-power frequency conversion AC power series of products of separate unit capacity to 250kVA abroad.There is very large difference more abroad in China's airplane power source compared with techniques; Though domestic aircraft power system carries out the transition to the constant frequency AC source from low-voltage direct; But ripe goods shelf products quantity is few, and capacity also in 60kVA, is difficult to be applicable to the demand of large-scale civil aircraft power-supply system.Therefore the large-scale seating plane of greatly developing in current China under the new situation, novel aviation variable frequency AC power system will become the important developing direction of civil aircraft power-supply system.

Since the fifties in last century, the constant-speed and constant-frequency power-supply system was applied to Aircraft Electrical System; The aviation alternator type has only two kinds of three grades of formula synchronous machines and magnetoes, and magneto needs special tripping mechanism action owing to be applied to exist in the aviation power system intrinsic defective after the fault; Be difficult to satisfy the requirement of aviation power system high reliability; Therefore, five during the last ten years, and generator all adopts three grades of formula brushless synchronous machines in the aircraft AC power supply system.Also be to adopt three grades of formula brushless synchronous machines at present in the state-of-the-art large-scale civil aircraft variable frequency AC power system; Just three grades of formula synchronous machines are only used as generator in the frequency-converting power supply of A380; And in the more advanced B787 variable frequency AC power system; These three grades of formula brushless synchronous machines realized starting, the generating difunctional, realized the starting-generating integration operation.

In three grades of formula brushless synchronous machines because the existence of rotating rectifier; Be applied in the variable frequency AC power system as the starter time spent; Promptly operate in motoring condition, need begin starting from static, but this moment, exciter rotor remained static; Exciting current can't be provided, cause main generator excitation difficulty and have the problem that to start.Be generally and realize three grades of formula brushless synchronous machine starting operation functions, need pass to single-phase alternating current, need not to change the rotor winding construction of exciter the exciter stator excitation winding; Make exciter be operated in the form of similar transformer; Promptly utilize transformer EMF, in its armature rotor winding, induce voltage, pass through rotating rectifier again; For the main generator excitation winding provides exciting current, the main generator excitation function when realizing that brushless synchronous machine is static.This single phase alternating current (A.C.) excitation mode need not change the exciter stator winding construction; Directly the excitation winding of exciter is carried out AC excitation; But when the DC excitation winding was fed single-phase alternating current, the transformer EMF of responding in the armature rotor winding was the pulsating form, and energy transmission efficiency is lower; Make that main generator is difficult to obtain enough exciting currents, output is torque limited when causing starting operation.Therefore this single phase alternating current (A.C.) excitation mode only is applicable to three grades of formula synchronous motor starting electricity generation systems of middle low power grade usually.When three grades of formula brushless synchronous machines are applied to high-power frequency conversion interchange starting-generating system; Need adjust the structure and the control mode thereof of exciter,, on the basis of its stator DC excitation winding, increase by a cover three phase excitation winding through changing the stator winding structure of exciter; Perhaps substitute the DC excitation winding of original structure with the three phase excitation winding; It is passed to three-phase alternating current, and when rotor was static, this exciter equivalence became three-phase transformer; Induce three-phase alternating current in rotor-side, to main generator excitation is provided through rectifier bridge.

At present; External each big aviation electric corporation; As the Chinese win (Hamilton Sundstrand), Honeywell (Honeywell International), Smith's aviation (Smiths Aerospace), General Electric (GE) waits and has all early carried out three grades of formula brushless synchronous machine starting-generating integration Study on Technology, to the exciter winding construction design aspect application of single-phase, three-phase AC excitation mode and correspondence and protected number of patents.In recent years along with variable frequency power supply power supply system the applying gradually of large aircraft electrical system, be applied to variable frequency power supply starting-generating system and three-phase AC excitation control has proposed multiple design again to three grades of formula synchronous machines.The U.S. Pat 7687928B2 of Smiths Aerospace protection in 2010; Propose to adopt two cover excitation winding, a cover three phase excitation winding is applied to the operation of starting initial stage, and a cover DC excitation winding is applied to the later stage and the generating pressure regulation stage of start-up period; Two cover AC and DC excitation winding are separately positioned in the exciter; Generally after AC excitation was accomplished, the AC excitation winding no longer was used, and has greatly reduced the utilance of exciter winding.This patent with two brachium pontis in the three-phase inverter of AC excitation after excitation mode switches; Be applied to the DC excitation power supply; Though saved independently DC excitation converter; But four switches of DPDT still need be set, the AC and DC winding is switched, can realize the integrated function of AC and DC excitation.Smiths Aerospace has proposed a kind of independent three-phase AC excitation winding realization AC and DC excitation function that adopts at the U.S. Pat 2009/0174188A1 of application in 2009; The starting initial stage is adopted three-phase AC excitation; Starting later stage and power generating stage become single-phase through switch with the three-phase windings in series, utilize the three-phase inverter of AC excitation to realize DC excitation function.This scheme utilizes the switch setting to carry out the change of excitation winding structure, has realized the switching of AC and DC excitation mode, has improved the utilance of exciter winding, and this patent only needs a cover converter can realize the AC and DC excitation function.But for realizing that exciter three-phase alternating current winding is from the star-like switching that is connected to the DC series mode; Need increase by 3 bidirectional switchs at least; Wherein two switches connect the neutral point of converter the 3rd brachium pontis and winding respectively in the AC excitation stage; DC excitation stage the 3rd brachium pontis excises from field circuit, and the 3rd switch switches to the direct current winding with the three-phase AC excitation winding, utilizes two phase brachium pontis to realize DC excitation function.

In the frequency-changing AC starting-generating system that adopts three grades of formula synchronous machines; Three-phase AC excitation control is applied to preliminary stage; After motor speed acquires a certain degree, after the employing DC excitation has the AC excitation same effect, promptly can switch to the DC excitation mode.Adopt diverter switch the three-phase AC excitation windings in series to be become in the process of direct current winding in the above-mentioned patent scheme; Because the time-delay characteristics of diverter switch; Will the output of exciter stator winding be exerted an influence; Make that changing appears in the main generator excitation electric current, influence output torque causes starting to go wrong.Therefore, in frequency-changing AC starting-generating system, on the basis that the main generator armature supply is controlled, steadily realize the AC and DC excitation control of exciter, significant to the start-up function of smooth realization engine.

Summary of the invention

The object of the invention is promptly on the basis of three grades of formula synchronous machine three-phase AC excitation control principles; The neutral point of exciter three phase windings is opened; Constitute winding open ended winding construction; Propose a kind of transformer configuration and control method thereof that realizes the AC and DC excitation function, in three grades of formula electric motor startings, generating overall process, realize the integrated controlled function of AC and DC excitation.

The present invention adopts following technical scheme for realizing above-mentioned purpose:

The frequency-changing AC starting-generating system that the present invention relates to; By three grades of formula synchronous machines, exciting power converter, start main power inverter, starting-generating controller, startup power supply and the generating output loading is formed; Wherein the exciter stator of three grades of formula synchronous machines is provided with the three phase excitation winding; And this three phase winding is not provided with neutral point, adopts winding open ended structure.For realizing AC excitation function and starting high speed stage, the DC excitation function in generating pressure regulation stage of starting process from static to low-speed stage; Exciting power transformer configuration among the present invention is that two cover three-phase bridge power inverters are provided with respectively and the excitation winding two ends; By the excitation control module of starting-generating controller, coordinate control two cover converters according to the rotating speed of starter and realize the integrated of AC and DC excitation function.

Frequency-changing AC starter-generator AC and DC excitation control method is following:

The starting initial procedure; To low-speed stage, connect the transformer configuration with three phase winding both sides respectively from static, coordinate the output vector of each converter of control to two cover converters; Select suitable integrated voltage vector; Produce required three-phase AC excitation voltage at three phase windings, make exciter be operated in specified output state, for the main generator starting operation provides enough exciting currents.

After motor speed reaches the excitation switching point; According to speed feedback signal, switch the control strategy of two cover exciting power converters, switch to DC excitation from the three-phase AC excitation mode; This handoff procedure need not to change through external switch the structure of exciter winding; Utilize the brachium pontis of two cover converters respectively every phase winding electric current to be adopted direct control mode, can the equivalence of three-phase alternating current winding be become the DC series structure, realize DC excitation function.

Need not to increase outside extra diverter switch in the integrated excitation of the AC and DC of the present invention control implementation procedure, the software through controller switches the control logic of two cover power inverters, realizes the integrated of AC and DC excitation function.Described AC and DC excitation handoff procedure; Because adopting software realizes; There is not delay time in the turn-on logic handoff procedure of power device; Therefore it is constant in handoff procedure, to keep main generator excitation, guarantees that starting output torque is unaffected, satisfies the torque-demand of engine start process.

Description of drawings

Three grades of formula synchronous machines of Fig. 1 AC and DC excitation control change device structure chart;

The space vector of voltage figure of Fig. 2 three-phase bridge converter;

The synthetic synthetic vector figure of voltage of Fig. 3 two cover converters;

The improved voltage of Fig. 4 synthesizes synthetic vector figure;

The composite diagram of Fig. 5 AC excitation target voltage vector;

The DC excitation structure chart of Fig. 6 equivalence.

Embodiment

Three grades of formula synchronous machine AC and DC excitation control change device structures are as shown in Figure 1.Exciter stator three phase winding two ends connect a cover three-phase power converters respectively, and two cover converter DC sides all connect field power supply U _DcPreliminary stage, to low-speed stage, two cover power inverters adopt improved SVPWM control strategy, for three-phase stator winding provides alternating current from static; High speed and generator operation stage, through the direct control to each phase excitation winding electric current of stator, equivalence constitutes the DC excitation winding, realizes the weak magnetic speed-up and the Regulation Control in generator operation stage.

Two cover power inverters can adopt SVPWM control respectively among the present invention, and the voltage vector of every cover power inverter is as shown in Figure 2.Because two cover converters can independently be controlled; During Comprehensive Control, its voltage vector can synthesize 64 synthesized voltage vectors, on the vector basis of converter 1; Respectively with A, B, C, D, E, F benchmark (O ') as converter 2; The vector of stack converter 2 constitutes the synthetic synthetic vector figure of voltage, and is as shown in Figure 3.When conventional single cover power inverter drives power supply to the motor of Y-connection, the three-phase winding voltage balance of motor, wherein every phase winding voltage max is 2U _Dc/ 3, correspondingly the length of its space vector of voltage figure also is 2U _Dc/ 3, and the excitation electromotor two ends among the present invention connect two cover power inverters, and use same DC power supply U _DcPower supply, under some on off state, for example converter 1 is exported U ₄, converter 2 output U ₃In ' time, can make the voltage of motor A phase winding reach U _Dc, the OG voltage vector in this on off state corresponding diagram 3 is so the length of OG voltage vector is U _Dc, so this voltage vector building-up process be not simply with the cover of two among Fig. 2 converter separately vector length carry out addition.

Because there is not neutral point in motor three phase windings in this programme, can't eliminate in the winding three multiple subharmonic automatically, therefore the effect of OG, OI, OK, OM, OP and the OR in the synthesized voltage vector shown in Figure 3 will cause producing in the motor windings triple-frequency harmonics.Be example with synthesized voltage vector G, as shown in Figure 1, converter 1,2 is respectively at U ₄(100), U ₃Under the effect of ' (011), each phase winding voltage of motor does

$\left\{\begin{array}{c}{U}_{A{A}^{\′}}=U_{\mathrm{dc}}\\ U_{{\mathrm{BB}}^{\′}}=-U_{\mathrm{dc}}\\ U_{{\mathrm{CC}}^{\′}}=-U_{\mathrm{dc}}\end{array}\right.---\left(1\right)$

Three the multiple subharmonic voltage amplitude that produces does

$U_{3N}=\frac{U_{{\mathrm{AA}}^{\′}}+U_{{\mathrm{BB}}^{\′}}+U_{{\mathrm{CC}}^{\′\′}}}{3}=\frac{-U_{\mathrm{dc}}}{3}---\left(3\right)$

This third harmonic voltage amplitude is non-vanishing, makes to be applied to that voltage contains triple-frequency harmonics on the motor windings, and when the starting process AC excitation, this tertiary voltage harmonic wave will weaken the effect of three-phase AC excitation.Therefore in resultant vector, rejected the voltage vector of the multiple subharmonic of above-mentioned generation 3 among the present invention, constituted system synthesis voltage vector-diagram as shown in Figure 4, its inscribed circle is maximum synthesized voltage vector running orbit, and amplitude is 3/4U _Dc, the SVPWM control mode of the independent converter of comparing, the direct current utilance can improve 29.9% in this programme.When exciter is realized the AC excitation function; Can improve the frequency of three-phase alternating current in this control strategy effectively; The voltage utilization that improves can be offset the increase of exciter stator winding impedance, makes exciter be operated in saturated output state, improves the energy transmission efficiency of AC excitation.

Therefore on the basis of above-mentioned synthetic vector control technology; Characteristic to exciter adopts the open-loop modulation strategy; Make it work in the AC excitation state,, calculate the amplitude of two converter output voltage synthetic vector OT according to the saturated output required voltage of exciter amplitude; As shown in Figure 5, when the required amplitude of OT less than

The time, only needing a cover converter job this moment, an other cover converter works in zero vector state, promptly is similar to the single converter power supply, can realize the AC excitation function; When the reference voltage vector amplitude greater than

The time, be example with (1) sector, calculate the angle γ of the intersection point of OT and AH, BH ₁, γ ₂

(1) when the reference vector phase angle less than γ ₁The time, this moment, reference voltage vector was in the downside of straight line AH in No. 1 sector, i.e. position shown in the figure, converter 2 output resultant vector U at this moment ₄' (being voltage vector OA), converter 1 equivalence output OT ', its amplitude, phase place are identical with AT, and the employing similarity law is tried to achieve amplitude and the phase angle β of OT ', and then ensuing control mode is similar to the SVPWM modulated process;

(2) when the reference vector phase angle greater than γ ₁, and less than γ ₂The time, this moment, reference voltage vector was between straight line BH and the AH in No. 1 sector, at this moment converter 1 output U ₄(being voltage vector OA) is by the U of converter 2 ₆, U ₂, promptly O ' the H shown in the figure, O ' B synthesize O ' T, and comprehensive converter 1,2 outputs promptly obtain required vector;

(3) when the reference vector phase angle greater than γ ₂The time, this moment, reference voltage vector was in the upside of straight line BH in No. 1 sector, and its control mode is similar to (1), converter 2 output resultant vector U ₆' (being voltage vector OB), the output of converter 1 and U ₆' superimposed, synthetic required output voltage vector.

The working method of other sectors is similar; Definite interval division according to each sector; Through coordinating control, can in whole periodic regime, in the exciter stator winding, synthesize the alternating voltage of required amplitude and frequency through two cover converters, accomplish the AC excitation controlled function.

After the starter rotating speed reached the excitation switching point, need not among the present invention increased outside contactor, utilized the power circuit of two cover converters of AC excitation can make every cross streams excitation winding all can carry out the control of bidirectional current through a H brachium pontis.Therefore switching to from AC excitation the DC excitation process, respectively the electric current of every phase winding is directly controlled, wherein passed through T ₁, T ₁', T ₄, T ₄' constitute the H bridge can directly control A phase winding electric current, through T ₃, T ₃', T ₆, T ₆' constitute the H bridge can directly control B phase winding electric current, through T ₅, T ₅', T ₂, T ₂' constitute the H bridge can directly control C phase winding electric current.Owing to the electric current of this three phase winding all can independently be controlled, therefore only needing control A phase winding electric current be direct current I, and B, C phase winding electric current are-I can realize the DC excitation winding connection of equivalence as shown in Figure 6, realization DC excitation controlled function.Because DC excitation only need realize unidirectional excitation function, therefore T in the H brachium pontis of control A phase winding in this DC excitation control mode ₁, T ₄The T of ' pipe, B phase winding ₃', T ₆The T of pipe, C phase winding ₅', T ₂The pipe drive signal is identical; Be DC excitation control switch pipe; Other 6 pipes block its drive signal, and as fly-wheel diode, the duty ratio of regulating above-mentioned excitation control switch pipe can realize the control of DC excitation electric current; Need not to increase outside any hardware switch circuit, can realize the handoff functionality of excitation mode from AC-to DC through software.

Claims (2)

1. frequency-changing AC starting-generating system excitation structure; It is characterized in that the three phase excitation winding being set by three grades of formula synchronous machinery excitation machine stators; And this three phase excitation winding is not provided with neutral point; Adopt winding open ended structure, the three-phase bridge converter is set respectively, constitute the exciting power transformer configuration at the winding two ends; For realizing AC excitation function and starting high speed stage, the DC excitation function in generating pressure regulation stage of starting process from static to low-speed stage; Said exciting power converter is coordinated control two cover converters according to the rotating speed of starter and is realized the integrated of AC and DC excitation function through the excitation module control of starting-generating controller.

2. the AC and DC excitation control method of a frequency-changing AC starting-generating as claimed in claim 1 system is characterized in that said method is following:

The starting initial procedure; From static to low-speed stage; Connect the transformer configuration with three phase winding both sides respectively to two cover converters; Coordinate the output vector of each converter of control; Select suitable integrated voltage vector; Produce required three-phase AC excitation voltage at three phase windings, make exciter be operated in specified output state, for the main generator starting operation provides enough exciting currents;

After motor speed reaches the excitation switching point; According to speed feedback signal, switch the control strategy of two cover exciting power converters, switch to DC excitation from the three-phase AC excitation mode; This handoff procedure need not to change through external switch the structure of exciter winding; Utilize the brachium pontis of two cover converters respectively every phase winding electric current to be adopted direct control mode, can the equivalence of three-phase alternating current winding be become the DC series structure, realize DC excitation function.

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