Abstract
Abstract:
The output voltage and current of renewable energy
sources such as Photo- voltaic are not controlled. Consequently
PV- Grid interface system is employed condition output voltage
and current into the grid. This call for efficient and well designed
control strategies to ensure reliability, stability and quality power
output. This paper proposes nine- level cascaded NPC/H-bridge
inverter as the PV- Grid interface. Cascaded NPC/H-Bridge
inverter is modeled and a control law for realizing nine- level
output with reduced harmonic content is developed. Modeling is
easily achieved by considering the whole inverter as having four
cascaded three level legs, two positive and two negative. Then a
mathematical model is formulated for LCL filters assuming that
the resistances associated with the inductances have negligible
effect on the system steady state variables. Finally a control
technique is developed for the whole system and its robustness
tested by carrying out several simulations tests in MATLAB
under different operating conditions.