1. EFE1 DC-AC invertere, sinsformet AC Mohahan Kap. 8.1-2-3
J.Nybo
Rev.:

2. Switch-Mode DC-AC Inverters
Chapter 8
Switch-Mode DC-AC Inverters X
converters for ac motor drives and uninterruptible power supplies

3. Switch-Mode DC-AC Inverter
Block diagram of a motor drive where the power flow is unidirectional

4. Switch-Mode DC-AC Inverter
Block diagram of a motor drive where the power flow can be bi-directional

5. Switch-Mode DC-AC Inverter
Four quadrants of operation

6. One Leg of a Switch-Mode DC-AC Inverter
The mid-point shown is fictitious

7. Synthesis of a Sinusoidal Output by PWM

8. Details of a Switching Time Period
Control voltage can be assumed constant during a switching time-period

9. Harmonics in the DC-AC Inverter Output Voltage
Harmonics appear around the carrier frequency and its multiples

10. Eksempel

11. Valg af switch frekvens fs

12. Harmonics due to Over-modulation
Bedre udstyring, men flere harmoniske.
(sinus klippes i toppen)
Det anbefales at bruge synkron PWM.
These are harmonics of the fundamental frequency

13. Output voltage Fundamental as a Function of the Modulation Index
Shows the linear and the over-modulation regions; square-wave operation in the limit

14. Square-Wave Mode of Operation
Fordele: Bedre udnyttelse af
DC spændingen.
Square-Wave modulation
Er et specialtilfælde af PWM,
Hvor amplitude modulations
Indekset er meget større en 1
Harmonics are of the fundamental frequency

15. Single-phase: Half-Bridge Inverter
Ingen Dc komponent i vo pga C+ og C-.
Velegnet sammen med transformatorer.
Capacitors provide the mid-point

16. Single-Phase Full-Bridge DC-AC Inverter
Consists of two inverter legs

17. PWM to Synthesize Sinusoidal Output
The dotted curve is the desired output; also the fundamental frequency

18. Eksempel

19. DC-side currents id
Small fictitious filters eliminate the switching-frequency related ripple

20. DC-side currents
Bi-Polar Voltage switching