L-C filter design implementation and comparative study with various PWM techniques for DCMLI

In recent time's multi-level inverters are widely used in industrial application, grid integration, renewable system, buildings and smart grid technology, etc. Uninterruptible power supply has become indispensable to our society. Concern with power quality and grid integration, a pure sinusoidal voltage-current waveform is necessary. For such reason a design of various filters is now emerged in research area. Filters have property to smooth current and voltage waveform. This paper proposes filter design guideline for L-C filter with IGBT based multi-level inverter. An L-C circuit used at the inverter output for filtering purposes and ensuring that the THD is lower. The L-C filter cancels all harmonics and a real pure sinusoidal output voltage and current is obtained. Variable voltage and frequency supply to A.C. drives is invariably obtained from a three-phase voltage source inverter. A various pulse width modulation (PWM) schemes are used. The most widely used PWM schemes for three-phase voltage source inverters are carrier-based sinusoidal PWM (SPWM) and space vector PWM (SVPWM). In this paper a method for an asynchronous motor with inverter and L-C output filter is presented and it is verified by simulations in Matlab-Simulink. The simulation results are presented for three-phase five-level diode clamped inverter followed by three-phase L-C filter. The simulation results are compared with sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM) for diode clamped multilevel inverter (DCMLI) in terms of THD.