Transcript Slide 1
Chapter 8 Switch-Mode DC-AC Inverters • converters for ac motor drives and uninterruptible power supplies Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-1 Switch-Mode DC-AC Inverter Power flow • Block diagram of a motor drive where the power flow is unidirectional Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-2 Switch-Mode DC-AC Inverter Power flow • Block diagram of a motor drive where the power flow can be bi-directional Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-3 Switch-Mode DC-AC Inverter • Four quadrants of operation Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-4 Full-Bridge DC-DC Converter Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-5 Half-bridge DC-AC Inverter • Half-bridge inverter (One leg of full bridge converter) Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-6 Square-Wave Mode of Operation Vˆ 4 V2 ˆ V Vˆ d Ao 1 Ao 1 Ao h h • Harmonics are of the fundamental frequency Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-7 Effect of Blanking Time • Results in nonlinearity Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-8 Effect of Blanking Time • Effect on the output voltage Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-9 Synthesis of a Sinusoidal Output by PWM Vd VAo 1 vcontrol ˆ Vtri 2 vcontrol Vˆcontrol sin 1t Vˆcontrol VAo 1 ˆ sin 1t Vd 2 V tri Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-10 Synthesis of a Sinusoidal Output by PWM (2) 1 Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-11 Half-Bridge DC-AC Inverter • Capacitors provide the mid-point Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-12 Full-Bridge DC-AC Inverter Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-13 Full-Bridge DC-AC Inverter Bipolar Voltage switching Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-14 Full-Bridge DC-AC Inverter Unipolar Voltage Switching Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-15 Full-Bridge DC-AC Inverter Unipolar Voltage Switching 1 • Harmonic components around the switching frequency are absent Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-16 Sinusoidal Synthesis by Voltage Shift Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-17 Programmed Harmonic Elimination • Angles based on the desired output • IC circuit or microcontroller required Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-18 Summary of DC-AC Inverters PWM square-wave Copyright © 2008 by Jose Bastos Chapter 8 Switch-Mode DCSinusoidal AC Inverters 8-19