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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.

This study investigates the energy transmission process of the Sepic converter in each of its operating modes. In this converter, the continuous conduction mode (CCM) is classified into two complete inductor supply mode (CISM) and incomplete inductor supply mode (IISM). The discontinuous CM (DCM) of the converter just contains an interval of IISM. The equivalent critical inductances between CISM-IISM and CCM-DCM are calculated in this study. In addition, for a specific range of input voltage and load resistance, the minimum and maximum values of the equivalent critical inductances are obtained. The minimum and maximum values of the equivalent critical inductances are calculated in such a manner that the converter operates in one of CISM-CCM, IISM-CCM and IISM-DCM in whole of the operational area. The experimental results are used to prove the validity of the presented theoretical subjects.

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This paper investigates the operational modes of buck dc-dc converters and their energy transmission methods. The operational modes of such converters are classified in two types, discontinuous conduction mode (DCM) and continuous conduction mode (CCM). In this paper, the critical inductance relation of DCM and CCM is determined. The equations of the output voltage ripple (OVR) for each mode are obtained for a specific input voltage and load resistance range. The maximum output voltage ripple (MOVR) is also obtained for each mode. The filter size is decreased and the minimum required inductance value is calculated to guarantee the minimization of the MOVR. The experimental and simulation results in PSCAD/EMTDC prove the correctness of the presented theoretical concepts.