Cost-Effective and High-Power-Density Nonisolated Bidirectional On-Board Charger

of PhD Thesis on

Battery charger/discharger for bipolar microgrids with synchronous bus voltage regulation

Design and Control of a High-Voltage-Gain Four-Port DC–DC Converter With Efficient Bidirectional Energy Storage for Renewable Energy Applications

This paper introduces a novel four-port, non-isolated, multi-input single-output (MISO) DC-DC converter designed explicitly for integrating renewable energy. The proposed topology greatly enhances traditional multi-port converters by allowing two renewable sources and a bidirectional energy storage unit to connect simultaneously within a compact, integrated design. Its main advantages include a simplified circuit that reduces complexity and features common-grounded two-input ports for improved system compatibility. It achieves high voltage gain and continuous input current without requiring auxiliary voltage-boosting cells or complex magnetic structures. Additionally, it has a dedicated bidirectional port that enables efficient charging and discharging, thereby improving system resilience. A simple switching strategy ensures seamless transitions between operational modes. A comparative analysis shows that the proposed converter effectively addresses the main limitations of existing multi-port converter (MPC) topologies, including excessive voltage stress, high input current ripple, and control complexity. Included are detailed theoretical analysis and circuit modeling to demonstrate the new structure’s superior performance and reliability. Additionally, the small-signal model for each operating mode is developed to build the converter control system. Decoupling networks are used to establish independent closed-loop controllers due to interactions among converter control loops. To validate the feasibility and effectiveness of the proposed MPC, an experimental prototype with a nominal power of 150 W has been built. The findings emphasize the converter’s substantial potential for use in hybrid energy systems, establishing a new benchmark for high-efficiency, multi-port DC-DC conversion in energy platforms.

A novel isolated three-port converter with ZVS range extension and power decoupling

This paper proposes a fixed-frequency isolated three-port converter (ITPC)that simultaneously realizes topology-level power decoupling, RMS-current minimization, and wide-range zero-voltage-switching (ZVS) extension. The main novelty is the coordinated use of an LC-resonant decoupling network, a switch-controlled-capacitor (SCC)-based equivalent-impedance regulator, and auxiliary-current injection. In contrast to existing three-port converters in which decoupling and ZVS extension are usually treated separately, the proposed ZVSRE-ITPC uses the SCC not only for power regulation but also to shift the ZVS boundary under the optimized modulation strategy. By matching the resonant frequency of each LC tank to the switching frequency, the direct power-transfer path between ports 2 and 3 is eliminated. An root-mean-square-current-minimized optimized modulation strategy (RMS-OMS) is further derived using the Karush–Kuhn–Tucker framework. Under the prototype parameters, the SCC reduces the critical ZVS power-transfer boundary of port 3%–14.63% of the original boundary, and the auxiliary inductor enables port 1 ZVS over the investigated operating range. A laboratory prototype verifies the power decoupling, RMS-OMS, dynamic transient response, efficiency improvement, and ZVS range extension.

A Cost-Effective Advanced High-Gain High-Efficiency DC–DC Converter for Photovoltaic Applications

This paper proposes a cost-effective, ripple-free input current, single-switch, non-isolated DC–DC converter based on a coupled-inductor (CI) and passive-clamp integrated topology for photovoltaic applications, which achieves high voltage gain and high-efficiency operation. The main contribution of this work is the development of a new integrated structure that combines a CI boost converter with an passive clamp circuit and an LC input filter to realize ripple-free input current while maintaining a low-cost and simple configuration. The primary objective of the design is to realize these features while achieving ripple-free input current at the lowest possible cost and preserving the simplicity of the conventional boost converter (CBC). This is accomplished without the use of additional power or auxiliary switches, resonant circuits, or other complexity-increasing elements. The proposed converter operates with a minimal number of operating modes, which simplifies both mathematical modeling and control implementation. In addition, the design ensures acceptable voltage and current stresses on the power electronic switches. A comprehensive steady-state analysis and a detailed design procedure are presented, along with the derivation of the AC small-signal model. The proposed converter is also compared with similar topologies reported in the literature. A 550-W experimental prototype is implemented, and its performance is evaluated and compared with that of the CBC. Experimental results validate the proposed design, demonstrating a voltage boost from 40 V to 400 V at a duty cycle of 65% and achieving a peak efficiency of 94.27% at a rated power of 550 W.

A new ultra-high gain CI-based DC/DC converter with low voltage and current stresses.

By integrating a three-winding coupled inductor (TWCI) with voltage multiplier cells, this study proposes a quadratic DC-DC converter that achieves ultra-high voltage gain while maintaining continuous input current and a common ground. The proposed coupled-inductor topology is specifically engineered to minimize both voltage and current stresses across all circuit components, thereby enhancing overall performance and enabling potential cost reductions. Enhanced design flexibility is a key feature of the proposed configuration, particularly because the secondary winding of the TWCI operates in a semi-trans-inverse manner, allowing high voltage gains to be realized even with a very low turns ratio. Regenerative passive clamp circuits are incorporated to recover the leakage energy of the TWCI and to limit voltage stresses on the active switches, which are driven with simultaneous switching patterns. The converter's vertical structure further alleviates semiconductor voltage stress, while intrinsic current sharing between the TWCI and the input inductor substantially reduces power dissipation in the main power components. Additionally, turn-off switching losses of both active switches are minimized via a quasi-resonant cell. The paper presents a comprehensive steady-state analysis, detailed power loss evaluation, a comparative study with existing topologies, and key design guidelines. All theoretical contributions are conclusively validated through experimental results obtained from a 200 W hardware prototype, converting a 25 V input to a 400 V output.