A R N Rao et al Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 3, Issue 6, Nov-Dec 2013, pp.2053-2059 www.ijera.com 2053 | Page Three-Phase Nine-Level Inverter for Photovoltaic System with Induction Motor A R Neelakanteswara Rao 1 , T Nagadurga 2 1 M.TECH Scholar, Dept of EEE, GEC Gudlavalleru, AP, India 2 Assistant Professor, Dept. of EEE, GEC Gudlavalleru, AP, India Abstract Electrical power play a vital rule in 21 th century, but non-conventional sources scale down day by day. Not only that concern for the environmental pollution around the world, so now a day’s photovoltaic (PV) power systems are getting more and more widespread with the increase in the energy demand. This paper proposed a three phase nine level inverter with voltage control method using semiconductor power devices for three phase induction motor in order to achieve a smooth, continuous and low total harmonics distortion (THD) waveforms. The proposed inverter system gives better voltage regulation, smooth results and efficiency compared to multi- level inverters. The inverter is capable of producing nine levels of output voltage levels (V dc , 3V dc /4,V dc /2, V dc /4, 0, -V dc /4, -V dc /2, -3V dc /4, -V dc ) The proposed inverter was verified by using simulation of MATLAB/SIMULINK software. Index terms: Photovoltaic (PV) system, multi-level inverter, semiconductor power devices, THD, induction motor. I. Introduction As the world is concerned with the fossil fuel exhaustion and environmental problem caused by conventional power generation, particularly solar have become very popular and demanding. PV sources are used in many applications because they have advantage of being maintenance and pollution free. It is used to convert the dc power from solar module to ac power to feed into load. The proposed three phase nine level inverter is very suitable to PV module with induction motor load, because of compare to common three phase multi-level inverter have high switching, but it could also unfortunately increase switching losses, acoustic noise, and level of interference to other equipment. Improving its output waveform reduces its harmonic content and, hence, also the size of the filter used and the level of electromagnetic interference (EMI) generated by the inverter’s switching operation. This paper developed a modified H-bridge single-phase multilevel inverter that has two diode embedded bidirectional switches. Coming to three phase proposed inverter required 21 switches (IGBT’s) and six diode embedded bidirectional switches, but in common three phase multi-level inverter required 48 switches (IGBT’s). So this topology have reduces a switching loss and high efficiency. A boost converter (step-up DC-DC) used in paper for high voltage before proposed inverter; this topology was applied to three phase asynchronous machine photovoltaic system with considerations for voltage control pulse generator. II. Photovoltaic System (PV) A solar cell basically is a p-n semiconductor junction. When exposed to light, a current proportional to solar irradiance is generated. Standard simulation tools utilize the approximate diode equivalent circuit shown in Fig. 1 in order to simulate all electric circuits that contain diode. The circuit consists of R on in series with voltage source V on . PVs generate electric power when illuminated by sunlight or artificial light, the absorption of photons of energy greater than the band-gap energy of the semiconductor promotes electrons from the valence band to the conduction band, creating hole-electron pairs throughout the illuminated part of the semiconductor. These electrons and holes pairs will flow in opposite directions across the junction thereby creating DC power. Figure 1: circuit model of PV cell. 2.1 Mathematical Model: The equation [1] & [2] that are used to solve the mathematical model of the solar cell based on simple equivalent circuit shown in Fig. 1, are given below; RESEARCH ARTICLE OPEN ACCESS