Cascaded H-Bridge Multilevel Inverter Using Micro-Controller for Single Phase Induction Motor

This paper presents a micro controller based control of multilevel inverter for single phase Induction motor. IGBT is used as power element. Pulse width modulation techniques (PWM), introduced three decades ago, are the most used methods to control the voltage and frequency supplied to electrical AC machines. This work proposes a new switching scheme for the cascaded H-Bridge multilevel inverter. Unlike other schemes, the proposed method is based on the symmetric regular sampling PWM with a single carrier and multiple modulating signals. On-transcendental trigonometric equations that define the switching instants of the multilevel inverter are derived [19]. This algorithm is implemented by a low-cost fixed-point microcontroller on an experimental five level cascaded inverter test-rig. Multilevel inverter has gained attention in recent years due to its high power capability associated with lower output harmonics. Several multilevel topologies have been reported in the literature and this paper focuses on asymmetric cascaded PWM technique. This technique provides reduced harmonics in the output voltage and significantly improves the RMS value of the output voltage compared to the conventional Sinusoidal Pulse Width Modulation (SPWM). A detailed study of the proposed modulation technique is carried out five-level PWM inverter test rig has been built to implement the proposed algorithm. Gating signals are generated using PIC microcontroller. The performance of the inverter has been analyzed and compared with the result obtained from theory. A scheme based on 5-level PWM inverter, which control a high performance 8-bit standard microcontroller with gate driver circuit and additional hardware is used, which allows a flexible and economical solution. The output voltage can be varied in a large range and with a good resolution. Experimental data obtained from an induction motor drive will be presented.