An AC/DC + Dual-active-bridge (DAB) circuit was found as one solution for the high-efficiency and high-power-density electric vehicle charger. One control option is to let the AC/DC part only convert the grid voltage to a double-line-frequency folded sine wave and let the DAB stage handle both the power factor and power delivery. While conventional single-phase-shift (SPS) tends to lose zero voltage switching (ZVS) at light load and the variable-switching-frequency dual-phase-shift (DPS) sacrifices the light-load performance, this paper proposes a multiple-phase-shift (MPS) control, which allows for a fixed-switching-frequency triple-phase-shift (TPS) control at the light load to enhance the grid power quality. At medium- and heavy-load conditions, a phase-shift jump from TPS to DPS is performed to reduce the circulating current and improve efficiency. The proposed control strategy secures ZVS, realizes unity PF accurately and minimizes the control complexity. Experimental results on a SiC-based 7.2 kW charger validated its effectiveness and the smooth transition between the heavy load and light load.

An indirect matrix converter is employed directly converting the grid ac to the battery voltage, with the dual-active-bridge taking care of the power factor correction and power delivery simultaneously. Such circuit is regarded as one candidate of the high-efficiency and high-power-density electric vehicle on-board chargers, if the double-frequency current ripple to the battery is tolerated. Instead of optimizing the overall charger, this paper is focused on adopting variable switching frequency with multiple phase shifts to accommodate the wide input range (80–260 $V_{\mathrm{ ac}}$ ) and output range (200 V–450 $V_{\mathrm{ dc}}$ ). In addition to the phase shift between the transformer primary-side and secondary-side voltage, one extra phase shift is added to the primary-side H-bridge when the instantaneous input voltage is higher than the reflected output, otherwise, to the secondary side. The goal is to secure zero-voltage-switching for all switches at all voltage range. Such control strategy is further optimized incorporating with the switch parasitic capacitance and dead-band settings. To further enhance the charger performance, GaN HEMTs are equipped to the on-board charger aiming at higher efficiency and higher power density than Si devices. Experimental results indicated that such charger with proposed control strategy embraces the peak efficiency of >97% at 7.2 kW and a power density of ~4 kW/L.

This study proposes a design and development of a wireless power transfer system to charge the battery in electric vehicles. A parallel–parallel topology is adopted to realise 10–15 cm‐distance power transfer using the resonance theory. Finite‐element method is used to extract the coil parameters. The advantages of the proposed design compared with the previous similar research are (i) low operational frequency (42 kHz) which avoids the electromagnetic interference to the on‐board automotive electronics equipment and (ii) low electric stress to the semi‐conductor switches through using zero‐voltage‐switching technique. A 2 kW prototype to charge 200 V battery was built to experimentally verify the theoretical analysis. The overall system efficiency is ∼ 86%.

As a new application area of electric vehicles, V2H (Vehicle to Home) recently becomes one of the most attractive research areas. In this paper, a three-phase four-wire inverter using four half-bridge legs is adopted to realize the V2H functionality. Such three-phase inverter acts as the grid-side AC/DC part of the battery charger. In order to deal with the imbalanced load, an independently controlled neutral module has been adopted to form the neutral line and provide the path for the zero-sequence current, together with split DC-bus capacitors. Each phase employs the independent SPWM control with the virtual resistor paralleled with the load, namely, notch-filter-incorporated capacitor voltage feedback control, which damps harmonics around the resonant frequency at various load conditions. In addition, this paper quantifies the load imbalance vs the DC-link voltage oscillation and provides the guidance for the selection of the DC-link capacitance. Finally, a 10kW three-phase four-wire inverter working at the V2H mode is built and tested, with the three-phase imbalanced load imposed to validate the proposed design and control strategy.

A high-frequency injection (HFI) sensorless control for interior permanent magnet synchronous motors with enhanced precision and widened speed range is proposed in this paper. The injection frequency reaches up to 2 kHz under a 50~100 kHz silicon carbide (SiC)-based three-phase inverter. In addition to the high switching frequency, the field-programmable gate array (FPGA) is utilized to achieve high control bandwidth (>200 kHz) when implementing the field-oriented control algorithm. The benefits of high switching frequency and high control bandwidth in senseless controls are explained theoretically, i.e., leaving enough room for the injection frequency by using SiC while tuning down the noise-to-signal ratio by using the FPGA. Experimental results verified that such manners improved the position estimation and lifted the injection frequency effectively, which further allows us to widen the motor speed range under the HFI sensorless control from 0 to 500 r/min with the conventional Si+DSP design to 0~1200 r/min with the proposed SiC+FPGA.

For any voltage above 600 V DC, it is usually recommended to use 900 V~1200 V SiC MOSFETs instead of GaN HEMTs, given presently commercial GaN HEMTs have the maximum voltage rating up to 650 V. This paper is an attempt of employing 650 V E-mode GaN HEMTs to build a three-level bidirectional DC/DC converter, with the input as an 800V battery, the output as the ~400 V DC grid and half of switches working at the hard-switching mode. The active balancing control instead of using clamping diodes in the conventional neutral point clamping (NPC) topology is adopted, aiming at higher efficiency. Simulation based on the double-pulse-test results shows that such design strategy with GaN has a better efficiency over the conventional 1200-V SiC MOSFET based Buck/Boost converter. Two bottom-cooled GaN HEMTs are in parallel to enhance the power capability and efficiency, which requires the special focus on the parasitic parameters. The effects of parasitics especially the stray inductance in the current commutating loop and the gate-drive loop during switching transitions have been comprehensively analyzed in this paper. Experimental results under 800V bus voltage are presented to verify the proposed solution.