This work develops an isolated bidirectional CLLC converter that achieves a wide output-voltage range for residential energy storage systems (ESS), while maintaining high efficiency and achieving high power density. The circuit is a two-stage architecture, where the first stage is an isolated CLLC converter with open-loop fixed-frequency control and the second stage is a buck converter used for output voltage regulation. The influence of the bus voltage on the efficiency of the system in both forward and reverse operation modes is analyzed. Then, an asymmetric resonant tank design is developed such that different voltage gains are achieved in each mode with high switching frequency operation at the resonance point to optimize efficiency. For high power density, an improved integrated transformer structure with controllable leakage is designed for the high step-down ratio specification of the ESS application. The core design is optimized based on core loss, copper loss, and core volume. A 1-kW experimental prototype using GaN switches was implemented with an input voltage of 380 V, output voltage of 35–50 V, highest efficiency of 94.55%, and power density of 5.56 W/cm3. The front-end stage CLLC converter operates at 700 kHz with a maximum efficiency of 97.02%.

This article proposes a high-performance, high-switching-frequency triangular-conduction-mode (TCM) bidirectional-interleaved buck converter for battery charging using digital control. Accurate conditions for achieving zero-voltage switching (ZVS) without zero-crossing detection (ZCD) are derived while considering the nonlinear parasitic capacitance of the switch components. This article also optimizes the method of calculating the switching frequency to reduce the delay time of pulsewidth modulation, thereby enhancing system stability. The conventional control method has inadequate resolution in the phase shift register of the digital controller under high switching frequency, hindering perfect interleaving of the two phases at 180°, which affects the characteristics of current ripple offset. The proposed control method effectively reduces the phase error between the two phases in an interleaving structure under high-frequency operation. In this way, full-range ZVS can be achieved when the circuit operates at the correct switching frequency. ANSYS Q3D Extractor software is employed to simulate the impedances of the power loops and investigate parasitic parameters, enabling optimization of the layout and modification of the switching frequency. An experimental prototype of a bidirectional buck converter using GaN switches was implemented with an output power of 1 kW, an input voltage of 66 V, an output voltage of 35-50 V, a switching frequency of 350 kHz-1 MHz, a highest efficiency of 97.52%, and a power density of 10 W/cm ³ .

The prospect of using robots in warehouses or supply chain processes is increasing due to the growth of the online retail market. This logistic robot is available in the market and uses a battery as energy storage device. However, this battery is large and heavy. Therefore, it needs a long recharging time. Dynamic Wireless Power Transfer (DWPT) can be an alternative to the conventional charging system because of its safety and flexibility that enables in motion charging. DWPT reduces the battery requirement size and capacity. Hence the stored energy can be used effectively for load transportation. A compensation with an inductor and two capacitors in the transmitter side, and a series connected capacitor in the receiver side which is named LCC-S compensation type has the capability to maintain the transmitter current with a fixed frequency operation. It provides less variation of the output voltage in response to the load variation. Moreover, the compensation of the receiver side uses only a single series capacitor which is low-cost. The analysis, modeling, and design procedures are discussed in this paper as well as the hardware implementation and verification of a 1.5 kW maximum power DWPT. The experiment shows the capability of the proposed system and shows maximum efficiency can reach 91.02%.