Modeling, Control and Simulation of Cascaded 3-5-9 Hybrid Inverter Topology for Grid Interface Application

Abstract

Abstract. Past research on modeling and control of Cascaded Multilevel converter has put more emphasize on conventional cascaded H-bridge inverter. In addition research has been done on realizing a five level output from one cell (i.e. 3-5) one cell topology) without cascading the cells; this fails to address the principle of realizing a general cascaded 3-5-N-level hybrid model. In this chapter, a novel phase shifted SPWM control scheme for cascaded 3-5-9 hybrid inverter topology is proposed. Superior harmonic suppression of the proposed PWM control strategy is verified using double Fourier analysis. Modeling of the hybrid inverter from first principle is described first by deriving a control law using switching techniques. Using the derived control law a standard switching model based on one cell is achieved. The switching model is expanded to realize detailed simplified average models both in abc and dqo co-ordinates. Based on the simplified models in dq0 co-ordinate, a feedback controller is designed for a cascaded 3-5-9-level hybrid inverter. The feedback controller developed is used to achieve grid voltage regulation, DC -bus voltage balance and load accommodation under varying DC sources and other load perturbations. Finally the adopted topology and the control scheme developed are verified through detailed MATLAB simulations which provide the possibility for renewable energy to be connected to the power grid without transformer.