A Three Level NPC LC-Switched Voltage Source Inverter

This paper presents a three level NPC LCswitched voltage source inverter. Conventional multilevel voltage source inverter behaves like voltage step down converter. Recently multilevel buck-boost Z-source inverter (ZSI) has been developed for better efficiency and power quality in renewable energy system. The impedance network of the Z-source inverter requires equal inductors and equal capacitors for its stable operation which is difficult to realize in practice at all time. The input current of the multilevel ZSI is also discontinuous in nature .The voltage stress on the Quasi ZSI switches is comparatively less and the input current is continuous in nature. But, multilevel Quasi ZSI uses more number of reactive elements (i.e. inductors and capacitors) which increases the size and cost of the system. It also requires isolated power supplies. To address the above issues a three level NPC LCswitched voltage source inverter is proposed in this paper. It retains all the advantages of quasi Z-source inverter as well as uses non isolated power supplies and comparatively less number of reactive elements for its operation. The advantages like higher voltage gain (for the same shoot through duty ratio), continuous input current, lower passive reactive element in the impedance network and non-isolated power supply, makes the proposed multilevel buckboost inverter more suitable for photovoltaic application, fuel cell application etc. The theoretical analysis, PWM control as well as modes of operation of the proposed three level NPC LCswitched voltage source inverter are discussed and verified using MATLAB Simulink Keywords— Z-source Inverter, Single Stage boost Inverter, PWM control, multilvel Inverter