CN102420560B - 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 alternating-current and direct-current excitation control method for a frequency-variable alternating-current starting power generation system. The excitation structure consists of an open circuit-type stator three-phase winding and a three-phase bridge-type converter, wherein the two ends of the three-phase bridge-type converter are connected. The method comprises the following steps of: starting an initializing process; coordinately controlling the output vector of each converter; selecting a proper comprehensive voltage vector; generating a required three-phase alternating-current excitation voltage in the three-phase winding so that a magnetizing exciter works in a rated output state to provide enough excitation current for the starting and the operation of a main power generator; when the rotating speed of a motor reaches an excitation switching point, switching from a three-phase alternating-current excitation mode to direct-current excitation according to a rotating speed feedback signal, wherein the structure of the winding of the magnetizing exciter does not need to be changed by an external switch in the switching process; and making the three-phase alternating-current winding equivalent to a direct-current serial structure by directly controlling each phase of winding current respectively by utilizing the bridge arms of two converters. Therefore, a direct-current excitation function is realized.

Description

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

Technical field

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

Background technology

Development along with airplane power source technology, Large Civil Aircraft power supply system is just from existing constant-speed and constant-frequency, speed change constant speed transits to frequency-changing AC power supply system gradually, variable frequency AC power system is directly given rear class load supplying by brushless AC generator, can effectively improve capacity and the efficiency of electricity generation system, and can directly adopt the distribution element in the power-supply system of constant frequency 400Hz, accessory power supply, APU generator and emergency power supply, various load in can compatible existing constant frequency power system, therefore frequency-converting power supply is just becoming the first-selection when nearly large-scale civil aircraft power-supply system.State-of-the-art large-scale civil aircraft, as the B787 of the A380 of Air Passenger company, Boeing adopts this variable frequency AC power system just, has formed separate unit capacity to the high-power frequency conversion AC power series of products of 250kVA abroad at present.China's airplane power source technology is compared and is had very large difference abroad, although Domestic Aircraft power-supply system is transitioned into constant frequency AC source from low-voltage direct, but ripe goods shelf products quantity is few, capacity also, in 60kVA, is difficult to be applicable to the demand of large-scale civil aircraft power-supply system.Therefore under the new situation, novel aviation variable frequency AC power system will become the important developing direction of civil aircraft power-supply system to the large-scale seating plane of greatly developing in current China.

Since the fifties in last century, constant-speed and constant-frequency power-supply system was applied to Aircraft Electrical System, aviation alternator type only has two kinds of three grades of formula synchronous machines and magnetoes, magneto is owing to being applied to there is intrinsic defect in aviation power system, after fault, need special tripping mechanism action, be difficult to meet the requirement of aviation power system high reliability, therefore, five during the last ten years, and in aircraft AC power supply system, generator all adopts three grades of formula brushless synchronous machines.In state-of-the-art large-scale civil aircraft variable frequency AC power system, be also to adopt three grades of formula brushless synchronous machines at present, just in the frequency-converting power supply of A380, three grades of formula synchronous machines are only used as generator, and in more advanced B787 variable frequency AC power system, these three grades of formula brushless synchronous machines have realized starting, it is difunctional to generate electricity, and have realized starting-generating integration operation.

In three grades of formula brushless synchronous machines due to the existence of rotating rectifier, be applied in variable frequency AC power system as the starter used time, operate in motoring condition, need to start from static beginning, but now exciter rotor remains static, exciting current cannot be provided, cause main generator excitation difficulty and have the problem that cannot start.Be generally and realize three grades of formula brushless synchronous machine starting operation functions, need to pass to single-phase alternating current to exciter stator excitation winding, without the rotor winding construction that changes exciter, make exciter be operated in the form of similar transformer, utilize transformer EMF, in its armature rotor winding, induce voltage, then pass through rotating rectifier, for main generator excitation winding provides exciting current, to realize the main generator excitation function of brushless synchronous machine when static.This single phase alternating current (A.C.) excitation mode does not need to change exciter stator winding construction, directly the excitation winding of exciter is carried out to AC excitation, but when DC excitation winding is passed into single-phase alternating current, the transformer EMF of responding in armature rotor winding is pulsating form, energy transmission efficiency is lower, make main generator be difficult to obtain enough exciting currents, while causing starting operation, export torque limited.Therefore this single phase alternating current (A.C.) excitation mode is only applicable to three grades of formula synchronous motor starting electricity generation systems of middle low power grade conventionally.When three grades of formula brushless synchronous machines are applied to high-power frequency conversion interchange starting-generating system, need to adjust the structure of exciter and control mode thereof, by changing the stator winding structure of exciter, on the basis of its stator DC excitation winding, increase a set of three phase excitation winding, or with three phase excitation winding, substitute the DC excitation winding of original structure, it is passed to three-phase alternating current, when rotor is static, this exciter equivalence becomes three-phase transformer, in rotor-side, induce three-phase alternating current, by rectifier bridge, to main generator, provide excitation.

At present; external Ge great aviation electric corporation; as Chinese victory (Hamilton Sundstrand), Honeywell (Honeywell International), Smith's aviation (Smiths Aerospace), General Electric (GE) etc. have all early carried out the research of three grades of formula brushless synchronous machine starting-generating integration technology, to single-phase, three-phase AC excitation mode and corresponding exciter winding construction design aspect application and protected a large amount of patents.In recent years along with variable frequency power supply power supply system is the applying gradually of large aircraft electrical system, for three grades of formula synchronous machines, is applied to variable frequency power supply starting-generating system and three-phase AC excitation and controls and proposed again multiple design.The US Patent No. 7687928B2 of Smiths Aerospace protection in 2010; propose to adopt two cover excitation winding; a set of three phase excitation winding is applied to the operation of starting initial stage; a set of DC excitation winding is applied to later stage and the generating pressure regulation stage of start-up period; two cover AC and DC excitation winding are separately positioned in exciter; generally, after AC excitation completes, AC excitation winding is no longer used, and has greatly reduced the utilance of exciter winding.This patent by two brachium pontis in the three-phase inverter of AC excitation after excitation mode switches, be applied to DC excitation power supply, although saved independently DC excitation converter, but still need to arrange four switches of dpdt double-pole double-throw (DPDT), AC and DC winding is switched, can realize AC and DC excitation integrated function.Smiths Aerospace has proposed a kind ofly to adopt independent three-phase AC excitation winding to realize AC and DC excitation function at the US Patent No. 2009/0174188A1 of application in 2009, the starting initial stage adopts three-phase AC excitation, starting later stage and power generating stage become single-phase by switch by three-phase windings in series, utilize the three-phase inverter of AC excitation to realize DC excitation function.This scheme utilizes 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 set of converter can realize AC and DC excitation function.But for to realize exciter three-phase alternating current winding from the star-like switching that is connected to DC series mode, need at least increase by 3 bidirectional switchs, wherein two switches connect respectively the neutral point of converter the 3rd brachium pontis and winding in the AC excitation stage, DC excitation stage the 3rd brachium pontis excises from field circuit, the 3rd switch switches to direct current winding by three-phase AC excitation winding, utilizes two-phase brachium pontis to realize DC excitation function.

In adopting the frequency-changing AC starting-generating system of three grades of formula synchronous machines, three-phase AC excitation is controlled and is applied to preliminary stage, after motor speed acquires a certain degree, adopt DC excitation to have after AC excitation same effect, can switch to DC excitation mode.In above-mentioned patent scheme, adopt diverter switch three-phase AC excitation windings in series to be become in the process of direct current winding, time-delay characteristics due to diverter switch, will exert an influence to the output of exciter stator winding, make main generator excitation electric current occur changing, impact output torque, causes starting to go wrong.Therefore, in frequency-changing AC starting-generating system, on the basis that main generator armature supply is controlled, steadily realize the AC and DC excitation of exciter and control, significant to realizing smoothly the start-up function of engine.

Summary of the invention

Object of the present invention is 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, form winding open-circuit type winding construction, a kind of transformer configuration and control method thereof that realizes AC and DC excitation function proposed, in three grades of formula electric motor startings, generating overall process, realize the integrated control function of AC and DC excitation.

The present invention for achieving the above object, adopts following technical scheme:

The frequency-changing AC starting-generating system 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 generating output loading forms, wherein the exciter stator of three grades of formula synchronous machines arranges three phase excitation winding, and this three phase winding does not arrange neutral point, adopt winding open-circuit type structure.For realizing the AC excitation function of starting process from static to low-speed stage and starting high speed stage, the DC excitation function in generating pressure regulation stage, exciting power transformer configuration in the present invention is that two cover three-phase bridge power inverters arrange respectively and excitation winding two ends, by the excitation control module of starting-generating controller, according to the rotating speed of starter, coordinate to control two cover converters and realize the integrated of AC and DC excitation function.

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

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

After motor speed reaches excitation switching point, according to speed feedback signal, switch the control strategy of two cover exciting power converters, from three-phase AC excitation mode, switch to DC excitation, this handoff procedure is without change the structure of exciter winding by external switch, utilize the brachium pontis of two cover converters respectively every phase winding electric current to be adopted to direct control mode, the equivalence of three-phase alternating current winding can be become to DC series structure, realize DC excitation function.

The integrated excitation of AC and DC of the present invention is controlled in implementation procedure without increasing outside extra diverter switch, and the software by 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, owing to adopting software, realize, in the turn-on logic handoff procedure of power device, there is no delay time, therefore main generator excitation can be maintained in handoff procedure constant, guarantee that starting output torque is unaffected, meet the torque-demand of engine start process.

Accompanying drawing explanation

Tri-grades of formula synchronous machine AC and DC excitation control change device structure charts of Fig. 1;

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

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 as shown in Figure 1.Exciter stator three phase winding two ends connect respectively a set of three-phase power converters, and two cover converter DC side all connect field power supply U _dc.Preliminary stage, from static to low-speed stage, two cover power inverters adopt improved SVPWM control strategy, for three-phase stator winding provides alternating current; High speed and generator operation stage, by the direct control to each phase excitation winding electric current of stator, equivalence forms DC excitation winding, realizes the Regulation Control in weak magnetic speed-up and generator operation stage.

In the present invention, two cover power inverters can adopt respectively SVPWM to control, and the voltage vector of every cover power inverter 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, using respectively A, B, C, D, E, the F benchmark (O ') as converter 2, the vector of stack converter 2, forms the synthetic synthetic vector figure of voltage, 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 is also 2U _dc/ 3, and excitation electromotor two ends in 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, so the length of OG voltage vector is U _dc, so this voltage vector building-up process not simply by the cover of two in Fig. 2 converter separately vector length be added.

Because three phase windings of motor in this programme do not exist neutral point, cannot automatically eliminate in winding three multiple subharmonic, so the effect of the OG in synthesized voltage vector, OI, OK, OM, OP and OR shown in Fig. 3 will cause producing triple-frequency harmonics in motor winding.Take synthesized voltage vector G as example, and 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 is

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

Three the multiple subharmonic voltage amplitude producing is

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

This third harmonic voltage amplitude is non-vanishing, makes to be applied to voltage on motor winding and contains triple-frequency harmonics, and when starting process AC excitation, this tertiary voltage harmonic wave will weaken the effect of three-phase AC excitation.Therefore in the present invention, in resultant vector, rejected the voltage vector of the multiple subharmonic of above-mentioned generation 3, formed 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, in this programme, linear modulationra can improve 29.9%.When exciter is realized to AC excitation function, in this control strategy, can effectively improve the frequency of three-phase alternating current, the voltage utilization improving 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 for exciter adopts open-loop modulation strategy, make it work in AC excitation state, according to the saturated output required voltage of exciter amplitude, calculate the amplitude of two converter output voltage synthetic vector OT, as shown in Figure 5, when the required amplitude of OT is less than

time, now only needing a set of converter work, a set of converter works in zero vector state in addition, is similar to single converter power supply, can realize AC excitation function; When reference voltage vector amplitude is greater than time, take (1) sector is example, calculates the angle γ of the intersection point of OT and AH, BH ₁, γ ₂.

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

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

(3) when reference vector phase angle is greater than γ ₂time, reference voltage vector upside in straight line BH in No. 1 sector now, 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, according to definite interval division of each sector, by two cover converters, by coordination, control, can in whole periodic regime, in exciter stator winding, synthesize the alternating voltage of required amplitude and frequency, complete AC excitation control function.

After starter rotating speed reaches excitation switching point, in the present invention, without increasing outside contactor, utilize 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 by a H brachium pontis.Therefore being switched to from AC excitation 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' form H bridge can directly control A phase winding electric current, pass through T ₃, T ₃', T ₆, T ₆' form H bridge can directly control B phase winding electric current, pass through T ₅, T ₅', T ₂, T ₂' form H bridge can directly control C phase winding electric current.Therefore only because the electric current of this three phase winding all can independently be controlled, needing to control A phase winding electric current be direct current I, and B, C phase winding electric current be-I, can realize equivalent DC excitation winding connection as shown in Figure 6, realizes DC excitation control function.Therefore because DC excitation only need realize unidirectional excitation function, in this DC excitation control mode, control T in the H brachium pontis of A phase winding ₁, T ₄the T of ' pipe, B phase winding ₃', T ₆the T of pipe, C phase winding ₅', T ₂pipe drives signal identical, be DC excitation control switch pipe, other 6 pipes block it and drive signal, as fly-wheel diode, regulate the duty ratio of above-mentioned excitation control switch pipe can realize the control of DC excitation electric current, without increasing outside any hardware switch circuit, by software, can realize excitation mode from the handoff functionality of AC-to DC.

Claims (1)

1. the AC and DC excitation control method of a frequency-changing AC starting-generating system excitation structure, described frequency-changing AC starting-generating system excitation structure arranges three phase excitation winding by three grades of formula synchronous machinery excitation machine stators and forms, and this three phase excitation winding does not arrange neutral point, adopt winding open-circuit type structure, at winding two ends, three-phase bridge inverter is set respectively, excitation power converter construction; For realizing the AC excitation function of starting process from static to low-speed stage and starting high speed stage, the DC excitation function in generating pressure regulation stage, described exciting power converter is controlled by the excitation module of starting-generating controller, coordinates to control two cover exciting power converters realize the integrated of AC and DC excitation function according to the rotating speed of starter; Two cover exciting power converter DC side all connect field power supply, it is characterized in that described method is as follows:

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

After motor speed reaches excitation switching point, according to speed feedback signal, switch the control strategy of two cover exciting power converters, from three-phase AC excitation mode, switch to DC excitation, this handoff procedure is without change the structure of exciter winding by external switch, utilize the brachium pontis of two cover exciting power converters respectively every phase winding electric current to be adopted to direct control mode, the equivalence of three-phase alternating current winding can be become to DC series structure, realize DC excitation function.

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