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In this study, conventional dc/dc converters are integrated with a battery for renewable energy applications. The proposed battery-integrated dc/dc converters (BICs) can be compact size because these converters comprise just two switches and two diodes. Smaller size and desirable efficiency of the proposed BICs make it possible to use BICs in grid-connected (ongrid) distributed photovoltaic (PV) systems. The proposed BICs provide constant output power (less fluctuation) in different irradiance levels in distributed PV systems resulting in a constant output voltage at the connection point of BICs to the DC link. Besides extracting maximum power from the renewable source, output voltage is properly regulated on reference voltage in the proposed BICs. Depending on the utilisation states of the battery in grid-connected distributed PV systems, the operation of BICs is described in three scenarios. A linear quadratic regulator (LQR) control is applied to regulate output voltage and power of renewable source on references for three scenarios. Finally, the performance of the proposed BICs with LQR controller is verified by simulation (in PSCAD) and experimental results.

This paper presents a battery-integrated multi-input step-up DC-DC converter (BI-MISUC) as a unified interface for multiple energy sources in the frame of a sustainable hybrid energy supply. The proposed converter comprises one bidirectional port for a battery and several unidirectional input power ports. Battery can be charged by input sources, discharged into load or bypassed while charging/discharging durations are independent of switching duty ratios for input sources. In the presented BI-MISUC, higher voltage gains with lower duty ratios are achieved not only by increasing the number of inputs but also using the switched inductor (SI) modules. It therefore enables BI-MISUC to be used for a wide range of applications from low to high voltage/power. Furthermore, input sources can be operated individually or simultaneously to supply load energy at the desired output voltage. The converter operation is described for three scenarios (i.e. no battery, battery charging and discharging). A linear quadratic regulator (LQR) control is also used to regulate the output voltage and output power of input sources at the desired references for different scenarios. Finally, the performance of the BI-MISUC is validated by simulations and experimental results.