Sequential switching hybrid sinusoidal modulation techniques for cascaded multilevel inverter

Abstract

Cascaded multilevel inverters synthesize a medium voltage output based on a series connection of Full Bridge Inverters (FBI) which use standard low-voltage component configurations and it is popular for many applications at high power rating due to its modular nature of modulation, control and protection requirements. The main objectives of this thesis are to propose computationally efficient Sequential Switching Hybrid Sinusoidal Modulation (SSHSM) techniques for Cascaded Multilevel Inverter (CMI), for switching loss reduction with good harmonic performance. Hybrid modulation represents the combination of Fundamental Frequency Pulse Width Modulation (FFPWM) and Multilevel Sinusoidal Pulse Width Modulation (MSPWM), which provides the integrated solutions of minimum switching frequency and high power quality. A new series of Hybrid Alternate Phase Opposition Disposition (HAPOD), Hybrid Phase Shifted Carrier (HPSC), Hybrid Carrier Based Space Vector Modulation (HCBSVM) and Hybrid Single Carrier Sinusoidal Modulations (HSCSM) has been proposed and investigated. This modulation possesses the hybrid characteristics of FFPWM and CBSVM. The proposed modulation techniques are evaluated and compared with standard MSPWM schemes. Experimental investigations on these modulations are performed on Digital Signal Processor (DSP) - Complex Programmable Logic Device (CPLD) based digital control five-level CMI. Analyses and comparison of the new modulation schemes allow to evaluate in an objective way the contributions brought by this work. These control methods make reduced switching losses, low harmonic distortion, DC capacitor voltage balancing, and balanced power distribution and equal loading in CMI operation. It is found that the newly proposed modulation schemes cover an area of single phase, three phase and multiphase CMI structures. The power loss reduction due to these modulations could help to improve the efficiency of the system, reduce the size of heat sink, thereby aiding design of compact and reliable power converte