CN103326603B - A kind of switch periods Optimal Space Vector PWM method and modulator - Google Patents
A kind of switch periods Optimal Space Vector PWM method and modulator Download PDFInfo
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Abstract
The present invention discloses a kind of switch periods Optimal Space Vector PWM method and modulator, and the time window regulating by a width self adaptation is controlled average frequency of switching, and the switch periods in different time window is separate; Switch periods in window is interrelated at the same time, and switch periods is subject to time window, switch periods coefficientWith modulation ratioAnd phase angleBetween the control of optimization rule, can significantly reduce in SVPWM the large peak value of collection bunch harmonic wave, greatly reduce total harmonic distortion, improve the quality of output voltage; The time window regulating by width self adaptation is controlled average frequency of switching, makes full use of the frequency range of power switch pipe, has improved the cost performance of frequency conversion system; Modulator of the present invention can make full use of FPGA circuit customization flexibly feature, and other circuit of governing system and algorithm are integrated in a FPGA; Improve and controlled the speed that software is carried out, for its application in frequency conversion speed-adjusting system provides guarantee.
Description
Technical field
The invention belongs to alternating frequency conversion technique field, be specifically related to a kind ofly can reduce harmonic distortion and collection bunch harmonic wave peak valueSwitch periods Optimal Space Vector PWM method and modulator.
Background technology
Two level three-phase inverters as shown in Figure 1 and space vector PWM (SVPWM) are widely used in industrial and agricultural productionVarious aspects. SVPWM is the general principle based on " volt-second balance ", and the potential pulse constantly changing with width carrys out equivalent needsCommand voltage, therefore, harmonic wave is inevitable. Harmonic wave brings energy loss, causes that the motor feels hot; Low-frequency harmonics can also causeTorque pulsation, and then cause mechanical oscillation; Precipitous pulse also causes serious electromagnetic interference, is just affecting other electronic equipmentsNormal operation.
For above these problems, researcher and engineers and technicians have proposed randomized method and have suppressed electromagnetismDisturb, adopt optimization method to eliminate specific subharmonic, harmonic reduction distortion. Switch periods (frequency) is the main ginseng of SVPWMOne of number is also one of main object of optimization and randomization. Randomization switch periods (frequency) can greatly weakenThe peak value of collection bunch harmonic wave, and then reduce the ill effect that collection bunch harmonic wave brings; Optimizing switch periods not only can greatly weakenThe peak value of collection bunch harmonic wave, and can also greatly reduce total harmonic distortion, improve the quality of output voltage, there is great realityWith being worth and application prospect.
The conventional pulse duration modulation method of prior art is:
Every mutually upper and lower two switching tubes become complementary conducting. Different on off states can form 8 basic voltage vectors,Comprise 6 non-zero basic voltage vectorsWith 2 Zero voltage vectors, as Fig. 2 instituteShow. In Fig. 2: 1 represents upper arm conducting, and 0 represents underarm conducting. Taking the end points of 6 non-zero basic voltage vectors as positive six of summitLimit shape can be divided into 6 districts as shown in Figure 2.
Paper " optimization pulse modulation technology (the OptimalPulsewidth in AC servo and low-loss industrial drivesModulationforACServosandLow-costIndustrialDrives)》(IEEETransactionsOnIndustrialElectronics, Vol.40, No.4, pp.1039 ~ 1047,1994) provide certaintySVPWM under different command voltage magnitude, non-inphase angle the optimized switching cycle taking harmonic distortion minimum as target discrete reallyDetermine method, the method can ensure in the time that motor stable state (invariablenes turning speed) is moved in a primitive period or a sector cycleInterior total on-off times is invariable. Paper " switch periods optimization method (the Switchingperiod of random SVPWMoptimizationmethodtorandomspacevectorPWM)》(InternationalJournalofAdvancementsinComputingTechnology, Vol.5, No.4, pp.181 ~ 189,2013) provideDefinite method in the optimized switching cycle taking harmonic distortion minimum as target under random SVPWM, the method can ensure electronicIn machine stable state (invariablenes turning speed) when operation,, total average on-off times within a primitive period or a sector cycle was invariable.The optimized switching cycle (switch periods coefficient) providing in above-mentioned two sections of papers with modulate the when function of phase angle and have definite ruleRule, (switch periods coefficient) is all the function of modulation ratio and phase angle the optimized switching cycle.
But, in motor closed-loop control system, in vector control system as electrically driven (operated) in electric automobile, because order turnsSquare, along with throttle constantly changes, causes the command voltage vector of controller output constantly to change, no longer constant amplitude of command voltage vectorValue is rotation at the uniform velocity. Now, three-phase command voltage has been no longer sinusoidal wave, just causes the average switch lock of power tube (as IGBT)Rate is uncontrollable. If switching frequency is too high, may burn out power tube; If switching frequency is too low, can be used for reducing harmonic waveSwitching frequency can not be fully used.
Summary of the invention
For the shortcoming of prior art, the object of the invention is to propose one and can reduce harmonic distortion and collection bunch harmonic wavePeak value, the switch periods taking harmonic distortion minimum as target that can make full use of again power tube switching frequency are optimized SVPWM methodAnd adopt the equipment of the method, with weaken collection bunch harmonic wave peak value, reduce total harmonic distortion, improve output voltage quality,The sexual valence of power tube is the Electro Magnetic Compatibility of governing system when.
The present invention is for solving the problems of the technologies described above adopted technical scheme as described below:
A kind of switch periods Optimal Space Vector PWM method, the time window regulating by a width self adaptationControl average frequency of switching, the time window that described width self adaptation regulates is presented as timing variable。
Further, when for certainty or random space vector pulse duration modulation method, will be basic with 6 non-zeros of inverterVoltage vector () end points is summit hexagonal area is divided into two large class regions: Zone R territory and Q districtTerritory, Zone R territory comprises subregion R1, R2, R3, R4, R5, R6, Q region comprises subregion Q1, Q2, Q3, Q4, Q5, Q6, Zone RSwitch periods coefficient in territory, switch periods coefficient in Q region, zone boundary place switch periods coefficient。
Further, when for certainty or random space vector pulse duration modulation method, switch periods be subject to time window,Switch periods coefficientWith modulation ratioAnd phase angleBetween the control of optimization rule, specifically comprise the steps:
S1: modulator is started working, according to command voltage vectorDirection of rotation and currency sense command voltage vectorWhether leap Zone R territory: a. if the time window of setting the adjusting of width self adaptation starts timing, counting by Q regionVariableWith timing variableInitialize 0, execution step S2; B. if not, the switch periods to fixAs modulationCycle,, execution step S7.
S2: detect and whether meet the time window condition that makes zero: if a. meets, counting variableInitialize 0, timing becomesAmountInitialize 0, execution step S3; If b. do not met, directly perform step S3, the condition that described time window makes zero is:A. by Q region leap Zone R territory or by a R subregion another R subregion of directly leaping; B.Be more than or equal to setting value，?。
S3：, according to controller output command voltage vectorAmplitude and phase angle, table look-up and ask switch weekPhase coefficient, then in conjunction with fixing switch periods, try to achieve switch periods, execution step S4, described in table look-up and try to achieveSwitch periods coefficientMethod be: by switch periods coefficientWith modulation ratioAnd phase angleBetween be related to discretization,
The method of described discretization is: modulation ratioAnd phase angleStep-length to fix respectivelyWithCarry out discrete,Only by switch periods coefficient corresponding on discretization gridValue is stored in memory, for tabling look-up,
Described method of tabling look-up is: a. judges modulation ratioWith phase angleResiding rectangular mesh region, searches net of living inThe switch periods coefficient corresponding to four summits in lattice regionValue, obtain the current command voltage vector with interpolation methodInstituteCorresponding switch periods coefficientValue; Or the switch periods coefficient on the mesh point closing on most for b.Replace.
S4: according to command voltage vectorCurrency detects region of living in: if a. is in Zone R territory or zone boundary,Execution step S6; If b. in Q region, perform step S5.
S5: judge whether to meet the optimal period condition that employing is tabled look-up and tried to achieve: a. is if perform step S6; B. asFruit is no,, execution step S6;
The described satisfied employing optimal period condition of trying to achieve of tabling look-up is:；
S6：, execution step S7.
S7: calculate action time of basic voltage vectors, the trailing edge by the impulse hits moment in advance or rising edge prolongSlow method is set Dead Time, according to the Dead Time of setting, calculates the impulse hits moment, impulse hits time register,Period register assignment, generates 6 road pulse switch signals by modulator.
A kind of switch periods Optimal Space Vector PWM device, comprises two group pulse jumping moment registers, a weekPhase register, one counting and initial value heavy cartridges circuit, a commutation circuit and a pulse-generating circuit, wherein:
Described period register is used for depositing modulation period;
In two group pulse jumping moment registers all for depositing the moment of every phase upper arm and underarm impulse hits;
The counter of described counting and initial value heavy cartridges circuit is used for accepting count pulse and subtracts 1 according to pulseNumber, when counter reduces to 0, then subtracts 1 while overflowing, and the pulse of output spill over, at the beginning of controlling and reloading counting from period registerBe worth, start the counting in next cycle, commutation circuit is sent into again in spill over pulse, and the currency of counter send pulse to produce electricityRoad;
Described pulse-generating circuit is used for the currency of counter and the setting value in impulse hits moment to compare, ifIdentical, impulse hits, the saltus step of pulse is finally converted into the 6 road pulse switch signals that inverter needs.
Further, every group pulse jumping moment register comprises 12 registers, deposits often to go up mutually in these 24 registersIn the moment of arm and underarm impulse hits, there are 4 register control A phases in every group: control the forward position of upper arm pulse, one for oneControl upper arm pulse back edge, control the forward position of underarm pulse for one, control underarm pulse back edge for one; In every group, having 4 postsStorage control B phase, controls the forward position of upper arm pulse for one, controls upper arm pulse back edge for one, before the pulse of a control underarmEdge, controls underarm pulse back edge for one; In every group, there are 4 register control C phases, control the forward position of upper arm pulse, one for oneIndividual control upper arm pulse back edge, controls the forward position of underarm pulse for one, controls underarm pulse back edge for one.
Further again, described two group pulse jumping moment registers are used alternatingly, and in impulse hits time register, depositThe impulse hits moment comprised Dead Time, be directly used in generation pulse switch signal.
Beneficial effect of the present invention is as follows:
(1) switch periods provided by the invention is optimized SVPWM method, and the time window regulating by width self adaptation is controlledAverage frequency of switching processed, is ensureing that average frequency of switching is no more than frequency range same of the normal job requirement of power switch pipeTime, consider the situation of electric machine control system dynamic change, take full advantage of the frequency characteristic of power switch pipe, improve frequency conversionThe cost performance of system.
(2) method of the present invention ensureing fundamental voltage, in each modulation period the constant prerequisite such as average on-off timesUnder, the large peak value of collection bunch harmonic wave in SVPWM can be significantly reduced, and total harmonic distortion can be greatly reduced, improve output electricityThe quality of pressing and the Electro Magnetic Compatibility of governing system.
(3) in modulator of the present invention, the Dead Time of three-phase control impuls and producing method can independently arrange, and haveVery large flexibility, has facilitated the combination application of advanced dead area compensation algorithm.
(4) modulator of the present invention can make full use of FPGA circuit customization feature flexibly, by other of governing systemCircuit and algorithm are integrated in a FPGA; Utilize the executed in parallel characteristic of FPGA to improve the speed that software is carried out of controlling, forThe mutual fusion of advanced control algorithm and modulation algorithm more, with and application in frequency conversion speed-adjusting system guarantee is provided.
(5) switch periods in the present invention is along with rotary speed, amplitude and the phase angle of command voltage vector constantly change, originallyThe method of invention not only goes for certainty SVPWM, can also be applicable to random SVPWM.
Brief description of the drawings
Fig. 1 is two level three-phase inverters and motor method of attachment schematic diagram;
Fig. 2 is basic voltage vectors and synthetic method schematic diagram;
Fig. 3 is Q, R subregion schematic diagram;
Fig. 4 be in Fig. 2Graph of a relation in district between optimal period coefficient and phase angle and modulation ratio;
Fig. 5 is the flow chart of pulse duration modulation method provided by the invention;
Fig. 6 is an application scheme schematic diagram of the present invention;
Fig. 7 is the logical circuitry of modulator of the present invention;
Fig. 8 is the A of inverter output under the 7 sections of mode of action floatless switch cycle SVPWM methods of symmetrical expression that adopt nowPhase voltage pulse is sampled within the primitive period, carries out the amplitude spectrum that Fourier transformation obtains;
Fig. 9 is that the A phase voltage pulse of inverter output under the inventive method and equipment is sampled within the primitive period, carries out FuIn the amplitude spectrum that obtains of leaf transformation;
Figure 10 is that under the 7 sections of mode of action floatless switch cycle SVPWM methods of symmetrical expression that adopt now switch periods is at any timeBetween variation diagram;
Figure 11 be under the inventive method and equipment sometime window start switch periods temporal evolution in a period of timeFigure.
Detailed description of the invention
The object of the invention is to propose one and can reduce harmonic distortion with collection bunch harmonic wave peak value, can make full use of merit againThe switch periods taking harmonic distortion minimum as target of rate pipe switching frequency is optimized SVPWM method and is adopted the equipment of the method,With weaken collection bunch harmonic wave peak value, reduce total harmonic distortion, improve the quality, the when speed governing of sexual valence of power tube of output voltageThe Electro Magnetic Compatibility of system.
In order to achieve the above object, the invention provides a kind of switch periods that can reduce harmonic wave and optimize SVPWM method,The time window regulating by a width self adaptation is controlled average frequency of switching. Specifically control mode is, time windowsSwitch periods in mouthful is separate; Switch periods in window is interrelated at the same time, i.e. switch periods shadow aboveRing switch periods below. The time window that described width self adaptation regulates is presented as timing。
Described switch periods is optimized SVPWM method, will with 6 non-zero basic voltage vectors of inverter () end points is summit hexagonal area is divided into two large class regions: Zone R territory and Q region. Segmentation againBe 12 sub regions, Zone R territory comprises subregion R1, R2, R3, R4, R5, R6; Q region comprises subregion Q1, Q2, and Q3, Q4,Q5, Q6, as shown in Figure 3. Subregion R1, R2, R3, R4, R5, switch periods coefficient in R6, subregion Q1, Q2, Q3, Q4,Q5, switch periods coefficient in Q6, zone boundary place. It is in sectorMiddle switch periods coefficientWith modulation ratioAnd phase angleRelation as shown in Figure 4.
As shown in Figure 5, described switch periods is optimized SVPWM method, when the vector control system for closed loop motorWhen middle, average frequency of switching is subject to variable timingControl, specifically comprise the steps:
S1: modulator is started working, according to command voltage vectorDirection of rotation and currency detectWhether by Q districtTerritory leap Zone R territory: a. is if the time window of setting the adjusting of width self adaptation starts timing, counting variableWith timingVariableInitialize 0, execution step S2; B. if not, the switch periods to fixAs modulation period,, execution step S7.
S2: detect and whether meet time window (restarting) condition that makes zero, whether meet following two: a. is by Q districtTerritory leap Zone R or by a R subregion another R subregion of directly leaping; B.Be more than or equal to setting value,。If meet counting variableInitialize 0, timing variableInitialize 0, execution step S3. If do not met, directly carry outStep S3.
S3：, according to controller output command voltage vectorAmplitude and phase angle, table look-up and ask periodic coefficient, then in conjunction with fixing switch periods, try to achieve switch periods. Execution step S4.
S4: according to command voltage vectorCurrency detects region of living in: if a. is in Zone R territory or zone boundary,Execution step S6; If b. in Q region, perform step S5.
S5: judgement, a. is if perform step S6; B. if not,. Execution stepS6。
S6：, execution step S7.
S7: calculate action time of basic voltage vectors, according to the Dead Time of setting (under the impulse hits momentFall along in advance or the method for rise edge delay set Dead Time, Dead Time depends on power tube, as the manufacture craft of IGBT,The model of the IGBT selecting), calculate the impulse hits moment, impulse hits time register, period register assignment, by modulatingDevice generates 6 road pulse switch signals.
Wherein, in described step S3, table look-up and try to achieve periodic coefficientMethod be: by periodic coefficientWith modulation ratioAndPhase angleBetween be related to discretization,WithStep-length to fix respectivelyWithCarry out discrete, only by discretization netCorresponding on latticeValue is stored in memory, for tabling look-up. The method of tabling look-up is:
JudgementWithResiding rectangular mesh region, searches four weeks that summit is corresponding of net region as shown in Figure 4Phase coefficientValue, obtain the current command voltage vector by interpolation method (as, bilinear interpolation) correspondingValue; Or withPeriodic coefficient on the mesh point closing onReplace.
Switch periods provided by the invention is optimized SVPWM method, is ensureing that average frequency of switching is no more than power switch pipeWhen the frequency range of normal job requirement, consider the situation of electric machine control system dynamic change, taken full advantage of powerThe frequency characteristic of switching tube, can, in reduced harmonic peak value, greatly reduce total harmonic distortion.
Switch periods in the present invention is along with rotary speed, amplitude and the phase angle of command voltage vector constantly change, thisBright method not only goes for certainty SVPWM, can also be applicable to random SVPWM. In random SVPWM, randomizationBreak the symmetry of pulse, and the pulse that generally popular digital control chip cannot produce asymmetric waveform now. Therefore,In order to make method of the present invention can also be applicable to random SVPWM and facilitate dead band time setting and compensation, (as shown in Figure 6,7)The present invention also provides a kind of modulator based on FPGA, and its switch periods adopts above-mentioned optimization method, and it is installed on frequency conversionIn the circuit of governing system, mainly comprise:
(1) register district, it comprises two impulse hits time register groups, one-period register. One weekPhase register, is used for depositing modulation period. Two jumping moment register groups, every group has 12 registers, these 24 registersIn deposit every phase upper arm and underarm impulse hits moment. In every group, there are 4 register control A phases, control upper arm arteries and veins for oneThe forward position of punching, controls upper arm pulse back edge for one, controls the forward position of underarm pulse for one, controls underarm pulse back edge for one; OftenIn group, there are 4 register control B phases, control the forward position of upper arm pulse for one, control upper arm pulse back edge, a control for oneThe forward position of underarm pulse, controls underarm pulse back edge for one; In every group, there are 4 register control C phases, control upper arm arteries and veins for oneThe forward position of punching, controls upper arm pulse back edge for one, controls the forward position of underarm pulse for one, controls underarm pulse back edge for one. TwoGroup register is used alternatingly generation control impuls, if use first group of register a upper modulation period, this cycle is used secondGroup, the lower cycle will be used first group.
Count and initial value heavy cartridges circuit for (2) one, its Counter is accepted count pulse and is subtracted 1 according to pulseNumber. When counter reduces to 0, then subtract 1 while overflowing, the pulse of output spill over, at the beginning of controlling and reloading counting from period registerBe worth, start the counting in next cycle. Commutation circuit is sent into again in spill over pulse. The currency of counter send pulse to produce electricityRoad.
(3) commutation circuit. This circuit is accepted the spill over from counter, controls two groups of registers alternately by cuttingChange circuit, and send pulse-generating circuit.
(4) pulse-generating circuit. Its effect is: the currency of counter and the setting value in impulse hits moment are compared, if identical, impulse hits. The saltus step of pulse is finally converted into the 6 tunnel control signal outputs that inverter needs.
Aspect the hardware based on FPGA realizes, the present invention hands over by two register groups that make control impuls jumping momentFor the generation that participates in relatively realizing 6 tunnel pulses. The function of at present popular control chip is all arranged symmetrically with for pulseModulator approach, i.e. the same along participating in register assignment relatively before and after pulse, cannot realize and the invention provides asymmetric space arrowAmount pulse duration modulation method; And popular control chip Dead Time producing method is fixed at present.
Main thought of the present invention is: at current period, the jumping moment register that does not participate in comparison is carried out to assignment; ?Current period finishes (the lower cycle starts) moment, and two groups of buffer status switch, and deposit at the jumping moment of current period assignmentDevice participates in relatively, and current period participates in jumping moment register group relatively and becomes not relatively state, for assignment is prepared; AndBefore and after pulse, comprised Dead Time along participating in register institute assignment relatively, dead band time setting and dead area compensation are originallyIn matter, be all by advance or delay pulse jumping moment (trailing edge in advance or rise edge delay) realize, in each cycle 3One have 12 impulse hits moment mutually, the present invention can be combined shifting to an earlier date and delayed-action of these 12 impulse hits momentMode, the mode of action of this Dead Time is very flexible, has facilitated the algorithm of dead band time setting and advanced dead area compensationIn conjunction with application. The method thinking novelty, simple in structure, applying flexible; And the parallel characteristics of FPGA, operation speed are fully appliedDegree is fast.
Below in conjunction with the drawings and specific embodiments, present invention is described:
The invention provides a kind of switch periods and optimize SVPWM method and the modulator based on FPGA, the knot of its inverterStructure as shown in Figure 1. Modulator provided by the invention can be installed on the controller of frequency conversion speed-adjusting system and isolated drive circuit itBetween, also itself and controller can be integrated in a FPGA, as shown in Figure 6.
In the each figure of the present invention, main element symbol description is as follows: 1 is register district; 2 is counting and initial value refitting liveRoad; 3 is commutation circuit; 4 is pulse-generating circuit; 11 is register group 1; 12 is register group 2; 13 is period register; 21For counter; 22 loading circuits of attaching most importance to.
First enforcement of the present invention will be divided into 6 sectors in Fig. 2 the large class of two shown in Fig. 3 region: Zone R territory and Q districtTerritory. Be subdivided into again 12 sub regions, Zone R territory comprises subregion R1, R2, R3, R4, R5, R6; Q region comprises subregion Q1,Q2, Q3, Q4, Q5, Q6. Subregion R1, R2, R3, R4, R5, switch periods coefficient in R6, subregion Q1, Q2, Q3, Q4,Q5, in Q6, zone boundary place. For some pulsewidth modulation strategies, switch periods coefficientThe table of parsingReach formula and solve difficulty, can adopt the paper " switch periods optimization method (Switchingperiod of random SVPWMoptimizationmethodtorandomspacevectorPWM)》(InternationalJournalofAdvancementsinComputingTechnology, Vol.5, No.4, pp.181 ~ 189,2013) in provideThe method evaluation solution of numerical analysis.
Then need according to the command voltage vector of controller outputJudge whether to meet switch periods and optimize SVPWMThe condition of operation, after satisfying condition, enters switch periods and optimizes SVPWM mode of operation. CalculateAmplitude and phase angle, rootTry to achieve periodic coefficient according to amplitude and phase angleValue, and then calculate moment of impulse hits, implementation step as shown in Figure 5, toolBody is as follows:
S1: modulator is started working, according to command voltage vectorDirection of rotation and currency detectWhether by Q districtTerritory leap Zone R territory: a. is if the time window of setting the adjusting of width self adaptation starts timing, counting variableWith timingVariableInitialize 0, execution step S2; B. if not, do with the switch periods of fixingFor modulation period,, execution step S7.
S2: detect and whether meet time window (restarting) condition that makes zero, whether meet following two: a. is by Q districtTerritory leap Zone R or by a R subregion another R subregion of directly leaping; B.Be more than or equal to setting value,，If meet counting variableInitialize 0, timing variableInitialize 0, execution step S3, if do not met, directly carries outStep S3.
S3：, calculation command voltage vectorAmplitude and phase angle, table look-up and ask periodic coefficient, try to achieve switchCycle, try to achieve switch periods, execution step S4.
S4: according to command voltage vectorCurrency detects region of living in: if a. is in Zone R territory or zone boundary,Execution step S6; If b. in Q region, perform step S5.
S5: judgement, a. is if perform step S6; B. if not,. Execution stepS6。
S6：, execution step S7.
S7: calculate action time of basic voltage vectors, the trailing edge by the impulse hits moment in advance or rising edge prolongSlow method is set Dead Time, according to the Dead Time of setting, calculates the impulse hits moment, impulse hits time register,Period register assignment, generates 6 road pulse switch signals by modulator.
In described step S3, table look-up and try to achieve periodic coefficientMethod be: by periodic coefficientWith modulation ratioAnd phase angleBetween be related to discretization,WithStep-length to fix respectivelyWithCarry out discrete, only by discretization gridCorrespondingValue is stored in memory, for tabling look-up. The method of tabling look-up is:
JudgementWithResiding rectangular mesh region, searches four weeks that summit is corresponding of net region as shown in Figure 4Phase coefficientValue, obtain the current command voltage vector by interpolation method correspondingValue; Or with on the mesh point closing on mostPeriodic coefficientReplace.
In concrete implementation process, in 6 districts shown in Fig. 2, optimal period coefficientWithWithBetween passSystem is identical; And, in same district, asQu Zhong, itsScope be,, be also to closeInSymmetry, therefore only needs storageScope bePart, as shown in Figure 4.
Switch periods coefficientWith modulation ratioAnd phase angleBetween the analytical expression of relation conventionally do not exist or veryComplexity, so only need on a memory limited point, judgementWithResiding rectangular mesh region, searches as Fig. 4Shown in four periodic coefficients that summit is corresponding of net regionValue, obtain the current command voltage vector with bilinear interpolationCorrespondingValue. If the storage resources of controller has in limited time, also can be by switch periods coefficientCarry out surface fitting, pass throughMethod in line computation solves.
In conjunction with Fig. 7, the modulator based on FPGA provided by the invention, it comprises:
A register district 1, it comprises two impulse hits time register groups: register group 1, register group 2, onePeriod register 13. Period register 13 is used for depositing modulation period. Every group of register group 1 and register group 2 has 12 to postStorage, the moment of depositing every phase upper arm and underarm impulse hits in these 24 registers. In every group, there are 4 register control APhase, controls the forward position of upper arm pulse for one, controls upper arm pulse back edge for one, controls the forward position of underarm pulse, a control for oneUnderarm pulse back edge processed; In every group, there are 4 register control B phases, control the forward position of upper arm pulse for one, control upper arm for onePulse back edge, controls the forward position of underarm pulse for one, controls underarm pulse back edge for one; In every group, there are 4 register control CPhase, controls the forward position of upper arm pulse for one, controls upper arm pulse back edge for one, controls the forward position of underarm pulse, a control for oneUnderarm pulse back edge processed. Two groups of registers are used alternatingly generation control impuls, if use register group 1 a upper modulation period,This cycle is used register group 2, and the lower cycle will be used register group 1.
In conjunction with Fig. 8, the register 1 in register group 1 is controlled the forward position of A phase upper arm, register 2 control A phase upper arm afterEdge, register 3 is controlled the forward position of A phase underarm, and register 4 is controlled the rear edge of A phase underarm; Register 5 control B phase upper arm beforeEdge, register 6 is controlled the rear edge of B phase upper arm, register 7 is controlled the forward position of B phase underarm, register 8 control B phase underarm afterEdge; Register 9 is controlled the forward position of C phase upper arm, and register 10 is controlled the rear edge of C phase upper arm, register 11 control C phase underarm beforeEdge, register 12 is controlled the rear edge of C phase underarm.
Register 13 in register group 2 is controlled the forward position of A phase upper arm, and register 14 is controlled the rear edge of A phase upper arm, depositsDevice 15 is controlled the forward position of A phase underarm, and register 16 is controlled the rear edge of A phase underarm; Register 17 is controlled the forward position of B phase upper arm, postsStorage 18 is controlled the rear edge of B phase upper arm, and register 19 is controlled the forward position of B phase underarm, and register 20 is controlled the rear edge of B phase underarm;Register 21 is controlled the forward position of C phase upper arm, and register 22 is controlled the rear edge of C phase upper arm, register 23 control C phase underarm beforeEdge, register 24 is controlled the rear edge of C phase underarm.
Count and initial value heavy cartridges circuit 2 for one, its Counter 21 has an input and two outputs, and input line connects meterRapid pulse punching also subtracts 1 counting according to pulse; An output line output current count value, of connecing pulse-generating circuit 4 is defeatedLambda line; Another output line output spill over, when counter reduces to 0, then subtracts 1 while overflowing, and the pulse of output spill over, controlsHeavy cartridges circuit 22, from the period register 13 counting initial value of reloading, starts the counting in next cycle. Spill over pulse againSend into the input pin CP of commutation circuit 3. The currency of counter 21 send pulse-generating circuit 4. Heavy cartridges circuit 22 has twoInput and an output, an input line connects the spill over of counter 21, and another input connects period register 13, output lineConnect counter 21.
Commutation circuit 3 is accepted the spill over from counter 21, and control register group 1 and register group 2 are alternately logicalCross commutation circuit 3, and send pulse-generating circuit 4.
Pulse-generating circuit 4 compares the currency of counter and the setting value in impulse hits moment, if identical,Impulse hits. The saltus step of pulse is finally converted into the 6 tunnel control signal outputs that inverter needs.
The figure place of above-mentioned related register can be 16,32 or other, need to be according to modulation period, FPGAModels etc. are specifically selected.
Modulator approach provided by the invention and circuit can be realized on numerous on the market FPGA, as Altera, Xilinx,The FPGA that the companies such as Lattice produce.
Be that 30Hz(is that motor stator voltage angle frequency is in fundamental voltage frequencyRad/s), pwm switchFrequency is 10000Hz, under the condition that modulation ratio is 0.9, implements the present invention. Fig. 8 is 7 sections of works of symmetrical expression of available technology adoptingSample within the primitive period with the A phase voltage pulse of inverter output under the fixing SVPWM method of mode, carry out Fourier transformation and obtainThe amplitude spectrum arriving; Fig. 9 is that the A phase voltage pulse of inverter output under the inventive method and equipment is sampled within the primitive period,Carry out the amplitude spectrum that Fourier transformation obtains; As shown in Figure 8, very large at the peak value of switching frequency integral multiple place collection bunch harmonic wave;As shown in Figure 9, switch periods is optimized SVPWM method and can greatly be reduced the peak value that switching frequency integral multiple place collects bunch harmonic wave.
Figure 10 is that under the fixing SVPWM method of 7 sections of modes of action of symmetrical expression of available technology adopting switch periods is in timeVariation diagram; Figure 11 be under the inventive method and equipment sometime window start switch periods temporal evolution in a period of timeFigure. In Figure 11, dashed rectangle part is situation when Rule of judgment is no in Fig. 5 step S5. As shown in Figure 10 and Figure 11, fromDashed rectangle part can obviously be found out the difference between the present invention and prior art, has presented one of innovative point of the present invention,The present invention can ensure to make full use of the switching frequency of power switch pipe in unstable state situation. Switch periods provided by the inventionOptimize SVPWM method and apparatus and can reduce harmonic distortion and collection bunch harmonic wave peak value, and can make full use of power switch pipeSwitching frequency.
The feature of method of the present invention and modulator is:
(1) method of the present invention ensureing fundamental voltage, in each modulation period the constant prerequisite such as average on-off timesUnder, can significantly reduce the large peak value of SVPWM method collection bunch harmonic wave generally adopting, and it is abnormal greatly to reduce total harmonic waveBecome, improve the quality of output voltage and the Electro Magnetic Compatibility of governing system.
(2) time window that method of the present invention regulates by width self adaptation is controlled average frequency of switching, fully profitBy the frequency range of power switch pipe, improve the cost performance of frequency conversion system.
(3) in modulator of the present invention, the Dead Time of three-phase control impuls and producing method can independently arrange, and haveVery large flexibility, has facilitated the combination application of dead band time setting and advanced dead area compensation algorithm.
(4) modulator of the present invention can make full use of FPGA circuit customization feature flexibly, by other of governing systemCircuit and algorithm are integrated in a FPGA; Utilize the executed in parallel characteristic of FPGA to improve the speed that software is carried out of controlling, forThe mutual fusion of advanced control algorithm and modulation algorithm more, with and application in frequency conversion speed-adjusting system guarantee is provided.
(5) switch periods in the present invention is along with rotary speed, amplitude and the phase angle of command voltage vector constantly change, originallyThe method of invention not only goes for certainty SVPWM, can also be applicable to random SVPWM.
Application of the present invention, has solved the large spike problem of traditional SVPWM method collection bunch harmonic wave, and has greatly reducedTotal harmonic distortion, can improve Electro Magnetic Compatibility and the reliability of system, and has improved the efficiency of utilization of power. Help especiallyIn solve electric automobile because battery capacity limits the course continuation mileage problem causing, and can be applicable to the products such as wind-power electricity generationIndustry, has good society and economic benefit.
It should be noted that above-mentioned specific embodiment is only exemplary, under above-mentioned instruction of the present invention, this areaTechnical staff can on the basis of above-described embodiment, carry out various improvement and distortion (is for example fixed SVPWM by 7 sections of modes of actionMethod becomes 5 sections of discontinuous certainty SVPWM methods of the mode of action etc.), and these improvement or distortion all drop on of the present inventionIn protection domain. It will be understood by those skilled in the art that specific descriptions are above in order to explain object of the present invention, notBe used for limiting the present invention. Protection scope of the present invention is limited by claim and equivalent thereof.
Claims (4)
1. a switch periods Optimal Space Vector PWM method, is characterized in that, regulates by a width self adaptationTime window control average frequency of switching, control the mode of average frequency of switching and be: the switch week in different time windowPhase is separate; Switch periods in window is interrelated at the same time, the time window body that described width self adaptation regulatesIt is now timing variable; When for certainty or random space vector pulse duration modulation method, will be with 6 non-zero-bases of inverterThis voltage vectorEnd points is that the hexagonal area on summit is divided into two large class regions: Zone R territory andQ region, Zone R territory comprises subregion R1, R2, R3, R4, R5, R6, Q region comprises subregion Q1, Q2, Q3, Q4, Q5, Q6,Switch periods coefficient in Zone R territory, switch periods coefficient in Q region, zone boundary place switch periods coefficient; Described switch periods is subject to time window, switch periods coefficientWith modulation ratioAnd phase angleBetween the control of optimization ruleSystem, specifically comprises the steps:
S1: modulator is started working, according to command voltage vectorDirection of rotation and currency sense command voltage vectorWhether leap Zone R territory: a. if the time window of setting the adjusting of width self adaptation starts timing, counting variable by Q regionWith timing variableInitialize 0, execution step S2; B. if not, the switch periods to fixAs modulation weekPhase,, execution step S7;
S2: detect and whether meet the time window condition that makes zero: if a. meets, counting variableInitialize 0, timing variableInitialize 0, execution step S3; If b. do not met, directly perform step S3, the condition that described time window makes zero is: a. is by QRegion leap Zone R territory or by a R subregion another R subregion of directly leaping; B.Be more than or equal to setting value,；
S3：, according to controller output command voltage vectorAmplitude and phase angle, table look-up and ask switch periods coefficient, then in conjunction with fixing switch periods, try to achieve switch periods, execution step S4, described in table look-up and try to achieve switch weekPhase coefficientMethod be: by switch periods coefficientWith modulation ratioAnd phase angleBetween be related to discretization,
The method of described discretization is: modulation ratioAnd phase angleStep-length to fix respectivelyWithCarry out discretely, only willThe switch periods coefficient of correspondence on discretization gridValue is stored in memory, for tabling look-up,
Described method of tabling look-up is: a. judges modulation ratioWith phase angleResiding rectangular mesh region, searches grid regions of living inThe switch periods coefficient corresponding to four summits in territoryValue, obtain the current command voltage vector with interpolation methodInstitute is correspondingSwitch periods coefficientValue; Or the switch periods coefficient on the mesh point closing on most for b.Replace;
S4: according to command voltage vectorCurrency detects region of living in: if a., in Zone R territory or zone boundary, carries outStep S6; If b. in Q region, perform step S5;
S5: judge whether to meet the optimal period condition that employing is tabled look-up and tried to achieve: a. is if perform step S6; B. if not,?, execution step S6,
The described satisfied employing optimal period condition of trying to achieve of tabling look-up is:；
S6：, execution step S7;
S7: calculate action time of basic voltage vectors, trailing edge by the impulse hits moment in advance or rise edge delayMethod is set Dead Time, according to the Dead Time of setting, calculates the impulse hits moment, impulse hits time register, cycleRegister assignment, generates 6 road pulse switch signals by modulator.
2. a switch periods Optimal Space Vector PWM device as claimed in claim 1, is characterized in that, comprises two groupsImpulse hits time register, one-period register, counting and initial value heavy cartridges circuit, commutation circuit and onePulse-generating circuit, wherein:
Described period register is used for depositing modulation period;
In two group pulse jumping moment registers all for depositing the moment of every phase upper arm and underarm impulse hits;
The counter of described counting and initial value heavy cartridges circuit is used for accepting count pulse and subtracts 1 counting according to pulse, whenCounter reduces to 0, then subtracts 1 while overflowing, and the pulse of output spill over is controlled from the period register counting initial value of reloading, and opensThe counting in next cycle that begins, commutation circuit is sent into again in spill over pulse, and the currency of counter send pulse-generating circuit;
Described pulse-generating circuit is for comparing the currency of counter and the setting value in impulse hits moment, if phaseWith, impulse hits, the saltus step of pulse is finally converted into the 6 road pulse switch signals that inverter needs.
3. switch periods Optimal Space Vector PWM device according to claim 2, is characterized in that, every group pulse is jumpedBecome time register and comprise 12 registers, the moment of depositing every phase upper arm and underarm impulse hits in these 24 registers, everyIn group, there are 4 register control A phases: control the forward position of upper arm pulse for one, control upper arm pulse back edge, a control for oneThe forward position of underarm pulse, controls underarm pulse back edge for one; In every group, there are 4 register control B phases, control upper arm arteries and veins for oneThe forward position of punching, controls upper arm pulse back edge for one, controls the forward position of underarm pulse for one, controls underarm pulse back edge for one; OftenIn group, there are 4 register control C phases, control the forward position of upper arm pulse for one, control upper arm pulse back edge, a control for oneThe forward position of underarm pulse, controls underarm pulse back edge for one.
4. switch periods Optimal Space Vector PWM device according to claim 3, is characterized in that, described two groups of arteries and veinsRush jumping moment register and be used alternatingly, the impulse hits moment of depositing in impulse hits time register has comprised dead bandTime, be directly used in generation pulse switch signal.
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