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The electric powered wheelchair (EPW) is an essential assistive tool for people with serious injuries or disability. This manuscript describes the validation of applied research for reducing the charging time of an electric wheelchair using a hybrid electric system (HES) composed of a supercapacitor (SC) bank and a lithium-ion battery with a fuzzy logic controller (FLC)-based fast charging system for Li-ion batteries and a fuzzy logic-based intelligent energy management system (FLIEMS) for controlling the power flow within the HES. The fast charging FLC was designed to drive the voltage difference (V d) among the different cells of a multi-cell battery and the cell voltage (V c) of an individual cell. These parameters (voltage difference and cell voltage) were used as input voltages to reduce the charge time and activate a bypass equalization (BPE) scheme. BPE was introduced in this paper so that the battery operates within the safe voltage range. For SC/Li-ion HES, the FLIEMS presented in this paper controls the bi-directional power flow to smooth the power extracted from Li-ion batteries. Moreover, a dual active bridge isolated bidirectional DC converter (DAB-IBDC) was used for power conversion. The DAB-IBDC presented in this paper has the characteristics of galvanic isolation, and high power conversion efficiency compared to the conventional converter circuits due to the reduced reverse power flow and current stresses.

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Abstract:The research significance of various scientific aspects of photovoltaic (PV) systems has increased over the past decade. Grid-tied inverters the vital elements for the effective interface of Renewable Energy Resources (RER) and utility in the distributed generation system. Currently, Single-Phase Transformerless Grid-Connected Photovoltaic (SPTG-CPV) inverters (1-10 kW) are undergoing further developments, with new designs, and interest of the solar market. In comparison to the transformer (TR) Galvanic Isolation (GI)-based inverters, its advantageous features are lower cost, lighter weight, smaller volume, higher efficiency, and less complexity. In this paper, a review of SPTG-CPV inverters has been carried out. The basic operational principles of all SPTG-CPV inverters are presented in details for positive, negative, and zero cycles. A comprehensive analysis of each topology has been deliberated. A comparative assessment is also performed based on weaknesses, strengths, component ratings, efficiency, total harmonic distortion (THD), semiconductor device losses, and leakage current of various SPTG-CPV inverters schemes. Typical PV inverter structures and control schemes for grid connected three-phase system and single-phase systems are also discussed, described, and reviewed. Comparison of various industrial grids-connected PV inverters is also performed. Loss analysis is also performed for various topologies at 1 kW. Selection of appropriate topologies for their particular application is thoroughly presented. Then, discussion and forthcoming progress are emphasized. Lastly, the conclusions are presented. More than 100 research publications on the topic of SPTG-CPV inverter topologies, configurations, and control schematics along with the recent developments are thoroughly reviewed and classified for quick reference.

Abstract:The dual active bridge isolated bidirectional DC-DC converter (DAB-IBDC) is one of the prime converters used in dual active bridge renewable energy storage system (RESS) applications, particularly where a high-power density is required. The digital DSP (Digital Signal Processer) control technique also provides intelligence to applications and achieves a super compact elegant system by reducing the complicated control hardware. All power converters, including the DAB-IBDC converter, often draw an inrush current, which is many times higher than their steady state current. The inrush current is the maximum current drawn by a converter for a very few milliseconds while being freshly energized. Although it appears for only a very few milliseconds, it can cause severe damage to the entire energy storage system, including the sources and loads. To save the RESS system from the starting inrush current and peak overshoot voltages, this paper proposes a five-phase digital soft-start control algorithm for a high-power DAB-IBDC converter that was implemented at a renewable energy storage system aimed at developing an intelligent self-powered energy zone. The proposed five phase digital soft-start algorithm can alone solve the startup transients without the use of any additional hardware. First, it prevents the output current and voltages from transients, such as the inrush current and peak overshoot voltages, by ensuring that the output current does not increase too rapidly while starting up. Second, it also eliminates the large backflow inrush current released by a partially discharged energy storage device at the starting period. Third, it helps achieve a simple super compact size DAB-IBDC converter with a simple elegant design by ensuring the control and soft-start in digital technology.