《电子电力技术》（英文版） Chapter 6 PWM Techniques

Power electronics Chapter 6 PWM Techniques

PPoowweerr EElleeccttrroonniiccss Chapter 6 PWM Techniques

The most widely used control technique in power electronics DC/DC ACaC Pulse Width Modulation(PWM) (Chopping control) DCIAC AC/DC

Power Electron cs i 2 The most widely used control technique The most widely used control technique in power electronics in power electronics DC/DC AC/AC Pulse Width Modulation (PWM) (Chopping control) DC/AC AC/DC

PEREC Outline 6. 1 Basic principles 6.2 Some major PWm techniques in dCIAC inverters 6.3 PWM techniques with feedback control 6.4 PWM rectifiers 3

Power Electron cs i 3 Outline Outline 6.1 Basic principles Basic principles 6.2 Some major PWM techniques in DC/AC inverters 6.2 Some major PWM techniques in DC/AC inverters 6.3 PWM techniques with feedback control 6.3 PWM techniques with feedback control 6.4 PWM rectifiers 6.4 PWM rectifiers

PEREC 6.1 Basic principles of PWM Similar response to different shape of impulse inpu ( f(4 a-d b e(OD The equal-area theorem f Responses tend to be identical when input signals have same area and time durations of input impulses become very small

Power Electron cs i 4 6.1 Basic principles of PWM Basic principles of PWM Similar response to different shape of impulse input Similar response to different shape of impulse input The equal The equal -area theorem: area theorem: Responses tend to be identical when input signals Responses tend to be identical when input signals have same area and time durations of input impuls have same area and time durations of input impulses become very small. become very small

PEREC Basic principles of PWM Application of the equal-area theorem H ◆ This is sinusoidal PWM (SPWM) 争 The equal-area theorem can be applied to realize any shape of waveforms 4 5

Power Electron cs i 5 Basic principles of PWM Basic principles of PWM Application of the equal Application of the equal -area theorem area theorem This is sinusoidal This is sinusoidal PWM (SPWM) PWM (SPWM) The equal The equal -area theorem can be applied theorem can be applied to realize any shape of to realize any shape of waveforms waveforms

PEREC A list of PWM techniques 4 Triangular-wave sampling Natural sampling Uniform sampling 4 Calculation Calculation based on equal-area criterion Selective harmonics elimination 4 Hysteric control Space Vector Modulation(SVM, or SVPWM) 争 Random pwm

Power Electron cs i 6 A list of PWM techniques A list of PWM techniques Triangular Triangular-wave sampling wave sampling – Natural sampling Natural sampling – Uniform sampling Uniform sampling Calculation Calculation – Calculation based on equal Calculation based on equal -area criterion area criterion – Selective harmonic Selective harmonic s elimination elimination Hysteric control Hysteric control Space Vector Modulation (SVM, or SVPWM) Space Vector Modulation (SVM, or SVPWM) Random PWM Random PWM

PEREC 6.2 Some major PWM techniques 争 Natural sampling 命 Uniform sampling 4 Selective harmonics elimination 争 Some practical issues Synchronous modulation and asynchronous modulation Harmonics in the pwm inverter output voltages Ways to improve DC input voltage utilization and reduce switching frequency Connection of multiple pwm inverters 7

Power Electron cs i 7 6.2 Some major PWM techniques Some major PWM techniques Natural sampling Natural sampling Uniform sampling Uniform sampling Selective harmonics elimination Selective harmonics elimination Some practical issues Some practical issues – Synchronous Synchronous modulation and asynchronous modulation modulation and asynchronous modulation – Harmonics in the PWM inverter output voltages Harmonics in the PWM inverter output voltages – Ways to improve DC input voltage utilization and reduce Ways to improve DC input voltage utilization and reduce switching frequency switching frequency – Connection of multiple PWM inverters Connection of multiple PWM inverters

PEREC Triangular-wave natural sampling Uni-polar PWM in single-phase VSI R VD K本vD Control u Mudulation Carrier Carrier Uni-polar sampling is used to realize uni-polar PWm

Power Electron cs i 8 Triangular Triangular -wave natural sampling wave natural sampling Uni -polar PWM in single polar PWM in single -phase VSI phase VSI Uni -polar sampling is used to polar sampling is used to realize realize uni -polar PWM. polar PWM. Control signal Carrier Mudulatio n Carrier Ud + V1 V2 V3 V4 VD1 VD2 VD3 VD4 uo R L ur uc

PEREC Triangular-wave natural sampling Bi-polar PWM in single-phase VSI R L VD VD Control Mudulation Carrier Carrier 4 Bi-polar sampling is used to realize bi-polar PWM

Power Electron cs i 9 Triangular Triangular -wave natural sampling wave natural sampling Bi -polar PWM in single polar PWM in single -phase VSI phase VSI Control signal Carrier Mudulatio n Carrier Ud + V1 V2 V3 V4 VD1 VD2 VD3 VD4 uo R L ur uc Bi -polar sampling is used to polar sampling is used to realize bi realize bi -polar PWM. polar PWM

PEREC Triangular-wave natural sampling In 3-phase VSI ,VD VD D 2/Vv∽D VIEW SmN r, 本本本吗刻H 2 Three-phase bridge inverter can only realize bi-bolar PWM 0Um therefore should be controlled by bipolar sampling

Power Electron cs i 10 Triangular Triangular -wave natural sampling wave natural sampling In 3 -phase VSI phase VSI Three -phase bridge inverter phase bridge inverter can only realize bi can only realize bi -bolar PWM therefore should be controlled therefore should be controlled by bipolar sampling. by bipolar sampling