Series-Cascaded Islanded Microgrids Comprising Storage: Sensorless Control Under PV Partial Shading and Load Variation

This article extends the use of voltage and current estimators, typically used in conventional systems, to a master–slave distributed generator (DG) configuration. The proposed method eliminates the need for expensive dc-side voltage and current sensors necessary to maximum power point tracking of the connected photovoltaic (PV) modules. Moreover, in medium- and high-power applications, this method can provide a valuable substitute to one or more faulty current or voltage sensors, which ensures system continuous operation while locating the faulty sensor(s). The introduced method does not affect the PV normal operation even in the presence of partial shading, battery charging/discharging, and fluctuating loads. The introduced method utilizes voltage and current estimators that rely on the ac-side measurements and a proposed switching function to isolate and calculate the voltage and current of each connected DG. The structure and the design details of these estimators are discussed in detail. The simulation and practical results conducted using the series-connected converter configured by the master (battery)–slave (PV) DG proved the validity of the proposed method in maintaining normal operation below 2% estimation error.