Grid integration of renewables using dual DC bus neutral point clamped inverter with improved power quality

Power electronic converters interfacing renewable power sources to the utility must comply with a series of standards imposed by grid operators. Power Quality is one such parameter that has to meet these standards. The injected grid current may have lower order harmonics due to various non idealities like grid voltage harmonics, ripple in dc link voltages and deadtime in PWM. Normally grid-side filters are not designed to attenuate these harmonics. Hence, these harmonics have to be actively attenuated through grid converter. In this paper, lower order harmonic elimination techniques are applied to a three level Neutral Point Clamped (NPC) converter that integrates a dual dc renewable bus to utility grid. The three level NPC offers certain advantages which are especially very attractive for high power applications such as central inverters. And also the Dual Renewable bus topology allows interfacing the renewable sources at a lower dc voltage i.e. half of the central inverter dc link voltage. The present topology along with proposed control scheme is an efficient way of interfacing renewable sources to utility grid while maintain high power quality. The simulation results are presented and experimental validation is done on a 3 kWp solar installation.