A Supercapacitor Assisted Technique for Reducing Losses in the Input Loop of an Inverter System for Solar PV Applications

This paper presents a method of using supercapacitor modules in the input loop, to reduce the input losses of a typical inverter system used in solar applications. It is an extension of the supercapacitor-assisted loss management principle (SCALoM), where supercapacitors act as lossless droppers and energy buffers at the input end with a very low frequency switching scheme with reduced dynamic losses in switches compared to switched capacitor-inverter systems. The technique uses a set of micro-inverters, with the same total power capability as a single inverter, combined with a set of supercapacitor banks switching at a low frequency to reduce the voltage stress and rms current through the H-bridge input stages of the inverters, enhancing the end-to-end efficiency of the overall system. The proposed technique does not require a re-design of the commercially available inverters and adds DC-UPS capability to the system. Preliminary experimental results of the SCA(super capacitor assisted) two-inverter arrangement show stable transient and steady state operations, and the system is up to 2.2% efficient compared to a single central inverter arrangement. With the proposed SCA four-inverter configuration, inverter's overall power load can be further partitioned, and according to the analytical study further improvements in the overall efficiency can be achieved over the SCA two-inverter arrangement .