A Direct Perturbation based Sensor-free MPPT with DC Bus Voltage Control for a Standalone DC Microgrid

A direct perturbation based sensor-free maximum power point tracking (MPPT) algorithm with DC bus voltage control is proposed in this paper for a standalone low voltage DC microgrid. The dual loop PI based single control algorithm not only presents simple and low cost MPPT but also provides ancillary service - DC grid voltage control. Emphasis is also laid in modeling of the solar photovoltaic (PV) based standalone DC microgrid. Maximum power is extracted by direct perturbations of duty ratio decided by a set of logic conditions which are computed by any voltage change that is sensed at grid side. For controlling the DC bus voltage, the duty ratios of a bi-directional converter (BDC) are updated by checking the direction of inductor current associated with battery energy storage system (BESS), which eventually helps in seamless transition of buck to boost mode of operation and vice-versa avoiding unnecessary outages in system. Modeling the system and implementation of the control algorithm is done by Simulink and MATLAB environment respectively.