Control of a three-port DC-DC converter for grid connected PV-battery applications

A control strategy for an energy management system (EMS) of a household nanogrid is presented in this paper. The proposed EMS is based on a state diagram. A three port converter (TPC) with direct storage capability is chosen and the states together with the state transitions are defined. The state diagram signals to two algorithms of which one calculates the battery current reference and the other allows the photovoltaic (PV) system to operate at the maximum power point (MPP) at all times. An extensive model has been implemented in MATLAB/Simulink using generic models to test the proposed control method. Results show a system which at all times follows a specified power exchange with the grid with a overshoot in power of 500W and worst case settling time of 500ms.