A multi-phase impedance source inverter with an improved controller structure
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Impedance source inverters (ZSIs) have many advantages like the ability to work as a buck or boost inverter and work with different renewable energy sources and can be applied as a voltage source or current source inverter. The switching circuits of ZSI normally are complicated and hard to be implemented. In this paper, a modified sinusoidal pulse width modulation method for ZSI block is presented based on an optimized mathematical model in order to switch the power components of this inverter. The proposed switching structure can be extended to more than one phase, by using the combination of the step-up converter, ZSI networks with the same switching topology for per phase and a full bridge inverter block in order to present a pure sinusoidal wave in the structure's output especially for resistive and inductive loads which are the real and industrial types of the loads. The Boost converter has been applied in our proposed structure in order to enhance the level of the generated voltages by RESs. Due to the ability to increase the voltage across the wide range, good resistance to electro-magnetic interference, acceptable total harmonic distortion value of the waves and immunity through shoot, this converter can be used extensively in PV systems, cell fuel, wind power and UPS systems. One of the most important specifications of the proposed switching method is working with low and intermediate values of duty cycles for power MOSFETs that can decrease the dynamic losses of the inverter. A wide range of mathematical analysis and simulations have been done to explain the proposed method, and experimental results confirm the theoretical analysis by a 100 W laboratory prototype.