With the rapid growth of electrified transportation, the design of charging infrastructure and station-level energy management has become increasingly important for meeting growing power and energy demands efficiently and cost-effectively. To address this challenge, this study presents an optimal sizing framework for photovoltaic (PV) and battery energy storage system (BESS) integrated EV charging stations, using an actual battery electric bus (BEB) charging station as the case study. This work formulates the load support fraction as a planning parameter, where different load support fractions (10 to 100)% are evaluated using an annualized-cost-based NPV metric, defined as the present value of annualized net savings to quantify the economic benefits and achieve optimal PV-BESS sizing design that is most profitable over the lifetime, considering seasonal variability. A hybrid bi-level optimization approach is proposed, where the outer Genetic Algorithm (GA) searches for the best PV-BESS size combinations and the inner Linear Programming (LP) model achieves optimal hourly dispatch for each GA candidate, enabling effective energy management. The case study results from a real-world battery electric bus (BEB) charging station operated by Utah Transit Authority (UTA) in Ogden, UT, USA, demonstrate that a 40% load support fraction is optimal and robust to seasonal variations, providing the best balance between the capital costs and long-term savings, and yielding 21.2% lower annual cost compared to a charging station design without PV-BESS and 42.5% higher NPV compared to a fully PV-BESS powered design.
Arifa Sultana, Jackson Morgan, Abdullah Al Mehadi et al.· IEEE Access· 0 citations
This paper presents a modular, highly efficient, fully soft-switched, quasi-single-stage, isolated three-phase AC-DC conversion system, intended for applications demanding an ultra-wide output voltage range, such as dc current distribution systems. The proposed topology comprises a three-phase Unfolder, a third-harmonic current injection (CI) circuit, and a dual active bridge (DAB) converter utilizing an $LCL$ resonant tank. The low-frequency-switched Unfolder significantly reduces the size of dc-link capacitors and eliminates the need for external grid-side inductive filters; however, it introduces fundamental design and control complexities due to time-varying dc-link voltages. To overcome these challenges, this paper introduces a novel zero-voltage/zero-current-switching (ZVS/ZCS) assisting circuit for soft-switching of the CI leg throughout the grid cycle, establishes wide-range soft-switching-oriented design guidelines for the DAB–$LCL$ converter over 200 V–800 V output voltage range, and develops a phasor transformation-based small-signal modeling framework that enables robust controller design and stability evaluation under time-varying dc-link voltage conditions. Hardware validation results demonstrate that the system achieves a peak efficiency of 97.4% at the rated output power of 5 kW with 2.1% grid current total harmonic distortion, and an input power factor of 0.99. Moreover, high efficiencies ranging from 94.3%-97.4% are achieved over a 200 V-800 V output voltage range. Furthermore, modular configuration is validated with a centralized Unfolder and two dc-dc converters in input-parallel, output-series (IPOS) configuration at 10 kW output power and a total output voltage of 1.6 kV, achieving a rated power ac-dc efficiency of 97.24%.
Shubhangi Gurudiwan, Aditya Zade, Hongjie Wang et al.· IEEE Open Journal of Power E...· 0 citations
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