Active Ripple Compensation Port for Single Phase Transformerless Photovoltaic Inverter

Transformerless topologies for grid feeding solar photovoltaic (PV) inverter have several advantages including low cost, low weight and high efficiency. The instantaneous power to the grid pulsates at double the grid frequency. An energy storage element is needed to supply oscillatory component of power such that the PV power can be decoupled from the grid power. This is usually done using Aluminium Electrolytic Capacitors (AECs) of large value. Though AECs are appealing due to their high volumetric efficiency and low cost, they have low reliability and limited current ripple capability. This limits the life expectancy of PV inverter and reduces its reliability. This paper explores active power decoupling technique for transformerless PV inverter topology with leakage current suppression. The reduction in capacitance requirement enables use of high reliability ceramic or film capacitors. The proposed ripple compensation port achieves dual function of decoupling pulsating power and boosting dc-Iink voltage, in case of low solar PV voltage. The working principle of the circuit is discussed and validated with help of simulations in MATLAB/Simulink software package.