Analysis, Modeling and Control of Cascaded NPC/H-Bridge Inverter for High Power Quality Grid Connection

T. Wanjekeche, D.V. Nicolae, and A.A. Jimoh (S. Africa)


Feedback control, NPC/H-Bridge inverter, Grid connected system, small signal model, State space technique.


The cascaded NPC/H- bridge inverter is first analyzed by establishing a new switching model based on a derived control law. From the developed switching model, a general model is obtained using state space technique. A new and accurate average model is developed using abc to dqo transformation technique. Finally small signal model is obtained by linearizing all the state variables around their quiescent operating points. The small signal model is used to study the effects of various control feedback variables on the dynamic performance of the Grid connected system. Feedback control scheme is designed to improve the dynamic response of the system. The system with the proposed control technique also achieves sinusoidal grid voltage and current output with low THD which is a preferred characteristic for any power injected to the grid. Simulation results are provided to validate the analytical models.

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