Topic 13Main contentsLast lecture reviewRealization of SPWMBlanking (Dead) time effect
Main contents • Last lecture review • Realization of SPWM • Blanking (Dead) time effect Topic 13
1.1 BasicprincipleofSPWM1) Basis: Narrow pulses with equivalentsquare but different shape have roughlyeffect when being put on the sameinertia subsystem.+f (t)4f (t)+f (t)↑f (t)G
1.1 Basic principle of SPWM 1) Basis：Narrow pulses with equivalent square but different shape have roughly effect when being put on the same inertia subsystem. 0 t 0 t 0 t f (t) f (t) f (t) 0 t f (t)
2)every small equivaleniareascompose SinusoidaPWM,SPWM.Sinusoidalwave:equalfottimeinteryalwithsinusoidalvariableamplitudeSinusoidalPwM::equalamplitudewithsinusoidalvariable width(i.e.timeinterval).otb)
l 2 ) every small equivalent areas compose Sinusoida PWM, SPWM. Sinusoidal wave: equal time interval with sinusoidal variable amplitude Sinusoidal PWM: : equal amplitude with sinusoidal variable width ( i.e. time interval)
u,UnipolarPWM3PWMsamplingbasedonareaequivalenceapproximatelyLrWudalEquivalentsinusoidalwaveb)
3) PWM samplingbased on area equivalence approximately Unipolar PWM Equivalent sinusoidal wave
UcontrolBipolarPWM3PwMsamplingbasedonareaequivalenceapproximatelytrtVcontrolYtri(a)VAOUoVs/2-Vs/2SO2(b)tri
Bipolar PWM vtri vcontrol vAo VS/2 -VS/2 tri 3) PWM samplingbased on area equivalence approximately Vˆ Vˆ 2 V tri Ao = vcontrol VS
u4)FromAmplitudemodulationofsinusoidalwaveto Sinusoidal PulsewrtWidth Modulation(SPWM)udaled:Eguivalentsinusoidalwavecttytb)
4）From Amplitude modulation of sinusoidal wave to SinusoidalPulse Width Modulation (SPWM) Equivalent sinusoidal wave
1.2 Terms of SPWM1) CarrierfrequencyAtriangular ( Vri asshown on this page) orsaw-teeth wave at aswitching frequency fs（六）which establishes the(a)frequency with which aUinverter are switched.This frequency is usuallycalled carrier frequencytor switching frequency fs(b)
1.2 Terms of SPWM 1) Carrier frequency A triangular ( vtri as shown on this page) or saw-teeth wave at a switching frequency fs, which establishes the frequency with which a inverter are switched. This frequency is usually called carrier frequency fc or switching frequency fs
Ucontrol2) Modulating frequencyA control signal Vcontrol isused to modulate theswitch duty ratio and hasH)a frequency f1, which is(a)the desired fundamentalfrequency of outputvoltage. This frequency isusually called modulatingfrequency or fundamentalfrequency fi.(b)
2) Modulating frequency A control signal vcontrol is used to modulate the switch duty ratio and has a frequency f1, which is the desired fundamental frequency of output voltage. This frequency is usually called modulating frequency or fundamental frequency f1
Ucontrol3) Amplitude modulationratio (index) macontrolm）tri(a)Uo4)Frequency modulationratio (index) mffsmJi(b)
tri control ma Vˆ = Vˆ 4) Frequency modulation ratio (index) mf 1 f mf = fs 3) Amplitude modulation ratio (index) ma
Vcontrol5) The peak amplitude of thefundamental-frequencycomponent is m, times (Va/2)LV=m(m。≤1)Aoa2X(a)6) Sidebandsharmonics: thoseharmonics appeararound the carrierfrequency and itsmultiples(b)
5) The peak amplitude of the fundamental-frequency component is ma times (Vd /2) 2 a d (m 1) （ V Vˆ ) = m Ao 1 a 6) Sidebands harmonics: those harmonics appear around the carrier frequency and its multiples