A symmetric carrier technique of CRPWM for voltage balance method of flying-capacitor multilevel inverter
Dae-Wook Kang
Byoung-Kuk Lee
Jae-Hyun Jeon
Tae-Jin Kim
Dong-Seok Hyun
Mechatronics Res. Group, Korea Electrotechnol. Res. Inst., Changwon, South Korea;
This paper appears in: Industrial Electronics, IEEE Transactions on
Publication Date: June 2005
Volume: 52,
Issue: 3
On page(s): 879- 888
ISSN: 0278-0046
INSPEC Accession Number: 8457686
Digital Object Identifier: 10.1109/TIE.2005.847574
Current Version Published: 2005-05-31
Abstract
This paper presents a simple carrier symmetric method for the voltage balance of flying capacitors in flying-capacitor multilevel inverters. The carrier-redistribution pulsewidth-modulation (CRPWM) method was reported as a solution for the voltage balance but it has a drawback at the transition of voltage level. To achieve the voltage balance of flying capacitors, the utilization of each carrier must be balanced during a half-cycle of the switching period such as phase-shifted PWM. However, the CRPWM method causes the fluctuation of flying-capacitor voltages because the balanced utilization of carriers is not achieved. Moreover, it does not consider that the load current change has an influence on flying-capacitor voltages by assuming that the current flows into the load. Therefore, the charging and discharging quantities of flying-capacitor voltages do not become zero during the switching period. To overcome the drawbacks of CRPWM, it is modified by the technique where carriers of each band are disposed of symmetrically at every fundamental period. Firstly, the CRPWM method is reviewed and the theory on voltage balance of flying capacitors is analyzed. The proposed method is introduced and is verified through simulation and experimental results.
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