Analysis and design of an integrated (LCR) trap -LCL-RC filter circuit for grid connected photovoltaic inverters

This paper presents a new (LCR) trap -LCL-RC passive filter for five level inverters utilised in grid connected PV applications. The novel filter is synthesized using the traditional LCL and LC trap-LCR configurations. A capacitor is connected across the R-C branch of the conventional LCR filter and an additional resistance is connected across the LC trap filter capacitor to improve high frequency harmonic attenuation and to decrease damping power loss. The paper brings out a comprehensive component design methodology for the developed filter which takes into account the impact of switching frequency and selection of reactive filter elements. A novel procedure for the selection of minimum inductance for the filter using particle swarm optimization technique is suggested. Further, the same technique is utilized to ensure minimum resonant peaking considering increased high frequency harmonic attenuation. A 110 V, 1 kW SPARTAN 6-XC6SLX25 processor based grid connected five level inverter connected to the developed filter is implemented. Simulation and experimental results are included to evaluate the performance of the proposed filter against various passive filter topologies that includes total harmonic distortion (THD), damping loss and switching harmonic current ripple reduction.