This paper presents an innovative technique for synchronous rectification in the bidirectional CLLC converter with the integrated transformer for plug-in electric vehicle (EV) applications. To improve the efficiency and power density, the integrated transformer is introduced and simulated using Finite Element Analysis (FEA) method. In addition, synchronous rectification method is implemented by controlling the turn-on and turn-off timings based on the phase difference between resonant currents of primary and secondary sides. Furthermore, a simplified closed loop design is discussed and implemented on a digital signal processor (TMS320F28335). The effectiveness of the control loop is verified through the experimental results. A 3.3kW proof-of-concept prototype is built with power density of 1kW/L, a gravimetric power density of 0.9kW/kg and peak efficiency of 97.5%.

This paper proposes a unique integrated and isolated dual-output dc-dc resonant converter, which can interface both HV traction batteries and LV loads. In addition, the proposed topology is bidirectional, capable of delivering power from HV traction batteries to the grid for vehicle-to-grid (V2G) applications. To increase the power density of the converter, the dual-output dc-dc resonant converter combines magnetic components of resonant networks into a single three-winding electromagnetically integrated transformer. The resonant converter uses a half-bridge topology with split capacitors as the resonant network components to further reduce the size of a converter. The variable dc-link voltage strategy is utilized to enhance the efficiency over the entire output voltage range. A 3.3-kW converter is designed and developed for validation of various operation modes, including grid-to-vehicle, V2G, and HV-to-LV charging.

This paper proposes a systematic approach to model and optimize an integrated transformer for on-board chargers in electric vehicles. The proposed approach includes a comprehensive transformer loss model with accurate electromagnetic description of leakage inductance and optimization process. The multi-objective optimization using genetic algorithm is presented to optimize the performancespace variables i.e. volume, weight and losses by appropriate selections of design-space parameters i.e. winding specifications and core candidacies. Four sets of integrated transformers are optimally designed and compared in terms of the theoretical analyses; finite element analyses (FEA) and experimental performance. As verification to the proof-ofconcept, the integrated transformers are implemented and tested on a 3.3kW on-board charger prototype. It has been shown that the measured losses agree with the theoretical computation. The peak efficiency of CLLC stage with the optimal selection of transformer reaches 98.2%, achieving efficiency enhancement and temperature improvement in comparison to other feasible candidates.

This study proposes a systematic approach to model and control a triple‐active‐bridge (TAB) converter for electric vehicle on‐board charger applications. An innovative generalised‐harmonic‐approximation (GHA) modelling method is proposed to accurately predict the instantaneous current and voltage waveforms. Based on the GHA modelling, a control strategy for a TAB converter is proposed, which enables the power flow from grid to two batteries with high conversion efficiency while achieving zero‐voltage switching operation. Compared to the conventional phase‐shift modulation, the proposed control method achieves an extended operating range of simultaneous charging operation mode, especially under the unbalanced load conditions. As a proof‐of‐concept, a 600 W prototype is built and tested. The experimental results are presented including waveforms of different operation modes and efficiency measurements. The peak efficiency of the TAB converter under the G2B mode is measured as 97.6%. The experimental waveforms exhibit good agreement with the waveforms obtained through GHA modelling.

In this paper, a comprehensive sliding mode control (SMC) loop design for a CLLC resonant converter is proposed. The major objectives of the proposed SMC are to improve the converter dynamics and to achieve a tight output voltage regulation with respect to any parameter variations and external disturbances. The sliding surface coefficients are selected to ensure both large- and small-signal stability for the robustness of the converter under different operating conditions. Furthermore, system dynamic performances considering the error dynamics and overshoots are investigated. To validate the proposed algorithm, a hardware prototype of a bi-directional CLLC resonant converter for plug-in electric vehicle applications is developed and tested up to 1 kW, and the effectiveness of the proposed control solution is verified by the load transients and start-up tests. At a 100% step-change in load power, the SMC achieves 1 ms settling time, which is approximately 0.9 ms faster than the conventional proportional integral control strategy.

This paper presents an innovative technique of synthesizing variable DC-link voltage control loop for a two-stage integrated AC-DC converter, which is a cascaded combination of a single-phase CCM interleaved totem-pole power factor correction (PFC) and a half-bridge CLLC resonant converter. Although the variable DC-link control exhibits a better overall efficiency than the fixed DC-link control, it faces issues of (i) loss of output voltage regulation and (ii) low frequency oscillations in the DC voltages and inductor current. In order to address and analyze these issues, both time-domain and frequency-domain studies of the control loop are performed, which led to two different voltage loop controller configurations, resolving the oscillation and regulation issues. As verification to the proof-of-concept, a hardware prototype of an integrated AC-DC converter is developed and tested up to 2kW. The experimental results exhibit a power factor of 0.992, peak efficiency of > 94% and a total harmonic distortion (THD) of < 5%, with the elimination of low frequency oscillation of the DC voltage waveforms.