Emphasis of modulated techniques for cascaded multilevel inverters fed drive using FPGA

Abstract

Pulse width modulated (PWM) techniques of a voltage source inverter need a reference signal and carrier signal to generate the required modulating signals for the desired output. Modifications in Modulating techniques can be considered in two ways, namely Modified reference and Modified carrier. The existing multilevel carrier-based pulse width modulation strategies have no special provisions to offer quality output, besides lower order harmonics are introduced in the spectrum, especially at low switching frequencies. This paper proposes a novel multilevel PWM strategy to corner the advantages of low frequency switching and reduced total harmonic distortion (THD). This paper also presents the most relevant control and modulation methods by a new reference/carrier based PWM scheme for Cascaded Multilevel Inverter and comparing the performance of the proposed scheme with that of the existing control schemes. A prototype is developed for a single-phase 5-level cascaded inverter fed drive using VHDL programming with FPGA.