This paper studies the need to include equalizing circuits in energy storage systems (ESSs), particularly in supercapacitor arrays. It evaluates the advantages and disadvantages of introducing these circuits in the system, and it presents a probabilistic study in order to show how much more energy can be stored by using an equalizing system. In addition, it evaluates several equalizing systems and presents a fast charging circuit that allows ESSs to charge at the same power as in the discharge process. The objective of the paper is to provide a guide for properly selecting an equalizing system when one is needed, for example, in electric vehicle or microgrid applications.

This study reviews the causes of power losses in a DC/DC converter, relates those losses with efficiency profiles, and details different strategies for maximising efficiency when several converters are placed in parallel. The research is focused on electric bus applications, where several converters are usually connected in parallel in order to fulfil the power requirements of the bus models. In a bus, the low‐voltage DC link (28 V) resembles a microgrid that has some generators (DC/DC converters), an energy storage system (lead–acid batteries) and certain loads. To share the converters’ output power, a droop control is proposed. Furthermore, traditional droop control is improved by adding a master–slave control. The proposed master–slave droop control improves efficiency by more than 3% at low power with no additional hardware. Experimental results show how two 5 kW converters work in parallel using the proposed control.

This paper presents a new structure of a multilevel inverter with fewer components, which is suitable for renewable energy sources and industrial loads applications. The structure has three unequal input sources and ten switches that can generate a 15-level output voltage. Furthermore, it can be connected in cascade for increasing, even more, the number of levels and output voltage. The main feature of the proposed inverter is its very low harmonic distortion at the output voltage and current due to the control method, which is based on the nearest level control method for generating a high-quality output voltage. A typical application of this inverter is in solar cells and wind turbines. Both simulations in Matlab/Simulink and experimental results in a scaled-down prototype validate the proposed theoretical analysis.

This paper presents a novel bidirectional series resonant converter for energy storage systems (ESS). Conversion between a DC energy storage device and an AC grid has grown in importance because of the renewable energy generators and ESS used in microgrids, which usually use batteries or supercapacitors as storage devices in order to provide different services and improve the quality and reliability of the grid. This novel converter avoids the need to have two converting stages: one for converting the energy from the storage device to a regulated DC value, and the other for converting the regulated DC to the AC output. Conversion occurs via a modified DC/DC dual-bridge series resonant converter. The output bridge of the converter is attached to the input bridge through a resonant branch and a high frequency transformer, and it is also attached to the AC link through an output filter. Therefore, two AC power signals are mixed in the output bridge: a high frequency signal, which maintains the DC link capacitor voltage, and a low frequency power signal, which transfers energy to the grid. This paper details the different working modes of the converter and presents a 3000W prototype that validates the design.

This paper presents a dual input-port bidirectional DC/DC converter for a Hybrid Energy Storage System (HESS). The converter is non-coupled, non-isolated and it has high-gain. Thus, it does not have transformer or coupling inductances, so voltage spikes or circulating currents are not present which is reflected in its high efficiency. In addition, the DC/DC converter is totally bidirectional, so the sources can transfer the energy between them and to the load. The converter has six switches but only three of them work in each mode, so the control is relatively simple. The main applications of the proposed converter are HESS for DC microgrid applications or small electric vehicles, particularly in which the storage system is small, hence the voltage is low, but the “load” works at a much higher voltage. The article analyses the converter in steady-state and presents the small-signal model, based on that, the control loop is designed. Simulations and experimental results validate the converter.