An LCL-based interface connecting photovoltaic back-up inverter to load and grid

This paper presents a new interface and filter structure for grid-connected (GC) photovoltaic inverters capable of operating in stand-alone (SA) mode as well. This type of inverter, named as `photovoltaic back-up system', is recently introduced and developed in industry. During GC operation, the structure places an LCL filter between the inverter and grid and the load is fed directly by the grid. In SA mode, the structure changes the LCL filter into an LC topology to enhance system stability and reduce the power dissipation. Moreover, the effect of the position of the current sensor on stability of the current control loop is discussed.