Ching-Ming Lai

Wireless motor drive (WMD) systems have been developed to address the problems of wire twists and motion limitations. Among various techniques, inductive power transfer (IPT)-based WMD systems have been widely adopted due to their high efficiency and power capacity. This review focuses on the circuit topologies and operating principles of IPT-based WMD systems. Existing WMD systems are categorized into two main architectures: cascaded and integrated structures. In cascaded structures, the IPT converter and the motor drive are implemented as separate stages. In contrast, integrated structures combine IPT and motor drive functions, typically through the use of multiple coils or matrix converters. The paper first examines various cascaded configurations, classified according to the voltage and current characteristics of the IPT output and the motor drive input. A comparative analysis between these topologies is then provided. Subsequently, the paper explores integrated structures, summarizing feasible multi-coil configurations and explaining the multiple frequency operation principle which is essential to such designs. Moreover, the application of matrix converters in WMD systems is reviewed, with a detailed discussion of their modulation strategies. Finally, based on the current state of research, the paper outlines existing challenges and proposes prospective directions for future development in the field.

This paper presents a novel current-fed multiport DC–DC converter (MP-DC) featuring a switched capacitor assisted three-phase interleaved architecture at the low-voltage port to mitigate current and voltage ripples in both inductors and capacitors. By integrating the nonisolated boost and isolated LLC units into a single-stage architecture, the proposed converter enables galvanic isolation for the EV battery, while achieving high efficiency and a high voltage conversion ratio between the ESS and the DC bus. The interleaved boost and LLC resonant stages share primary-side components, reducing the number of active switches and improving system compactness. By jointly applying pulse-width modulation (PWM) and pulse-frequency modulation (PFM), the isolated LLC unit yields a high step-up ratio, while the voltage conversion ratio of the nonisolated stage is effectively decoupled from the switching frequency, enhancing control flexibility. Moreover, an asymmetric duty-cycle limit control (A-DLC) scheme is further proposed to regulate the LLC input voltage under two- or three-level waveform modes and maintain balanced low-voltage side inductor currents. Accordingly, the operating principles, current ripple and power distribution characteristics, and design guidelines are analyzed in detail. Finally, a 2 kW prototype with 48 V /400 V /800 V ports validates the analysis, achieving peak efficiencies of 98.1% and 98.5% in forward and backward operations, respectively. These results confirm that the proposed MP-DC provides a compact and efficient solution for ESS – DC bus – EV integration in DC microgrid (DCMG) applications, offering advantages over conventional two-stage multiport converters.

Battery energy storage systems (BESSs) and dynamic line rating (DLR) can effectively mitigate key challenges in wind power systems. This article develops an integrated assessment framework to evaluate the impacts of BESS and DLR in wind-integrated power systems. The framework incorporates BESS active and reactive power support into optimal power flow (OPF), enabling a joint assessment of economic, operational, and reliability performance. In addition, the multidimensional impacts of BESS sizing are investigated under different DLR levels, and reliability is evaluated by modeling variations in BESS availability. Case studies are conducted on a modified IEEE-24 reliability test system (IEEE-24 RTS), and the scalability of the proposed framework is further validated on a larger IEEE-96 reliability test system (IEEE-96 RTS). The results show that coordinated deployment of BESS and DLR, with BESS reactive power support considered, achieves greater cost savings than standalone measures, while improving voltage profiles and reducing both energy and power losses. Moreover, increasing BESS energy capacity and rated power enhances system performance; however, the marginal benefits gradually diminish. Finally, system reliability deteriorates as BESS availability decreases, highlighting the importance of coordinated grid enhancement planning for wind power systems.

Wireless in-wheel motor drive systems have been used to reduce the disconnection risk of power cables. A series/capacitor-parallel (S/CP) compensation topology is proposed for the system. Despite the structural similarity with the series/series-parallel (S/SP) compensation, the S/CP compensation adopts a different design concept to enhance the voltage gain flexibility. Soft switching is first considered in the design given its importance for resonant converters. Based on the derived soft switching boundaries, design points can be readily determined. Meanwhile, virtual parameters are introduced to eliminate the terminal effect on soft switching. Furthermore, noting the motor load’s substantial tolerance of bus voltage variations, an optimization design method is proposed. The proposed design method can facilitate soft switching, ensure bus voltage requirements, and maintain high efficiency over a broad range of loads and misalignments. Finally, a 600 W prototype is built to verify the theoretical analysis, and a maximum efficiency of 96.81% is achieved.

This paper introduces a dual matrix converter (MC) based wireless power transfer (WPT) system for three-phase loads. The proposed system enables direct AC-AC power conversion, eliminating the need for bulky and short-lifetime electrolytic capacitors, thereby enhancing power density and reliability. Additionally, the paper explores modulation strategies for the proposed structure. Various modulation waveforms are compared and analyzed, revealing that antisymmetric and periodic flip modulations can mitigate phase shift effects on the system's total harmonic distortion (THD) performance, maintaining stable THD levels over a wide load range. Through Fourier analysis, it is observed that the fundamental components of antisymmetric and periodic flip waveforms are symmetric during a switching period. Leveraging this symmetry, an improved dwell time calculation method is proposed to reduce THD values for both grid-side and load-side currents. Finally, a prototype is constructed to validate the theoretical analysis, achieving a maximum efficiency of 93.3% and a minimum THD of 1.11%.

This article proposes an electrolytic capacitor-less wireless motor drive system. The primary-side electrolytic capacitors are removed through using a three-phase to single-phase matrix converter. The secondary-side electrolytic capacitors are eliminated based on the filter property of the parallel compensation. Moreover, a delta-sigma modulation is used in the proposed system to reduce the grid current harmonics and control the motor speed. Compared to conventional space vector pulse width modulation, delta-sigma modulation can help reduce the device stresses and switching times, allowing the system to operate at a higher switching frequency. To validate the analysis, a prototype operating at 200 kHz is constructed, and a total harmonic distortion of 3.12% is achieved.

Induction heating (IH) has been widely applied in both industrial and domestic environments as a clean, efficient, energy-saving, and high safety electric heating technology. This paper proposes a new pulse modulation for single-phase direct ac–ac converters in fluid water IH systems, which is defined as constant off-time pulse coding modulation (COT-PCM). The proposed pulse modulation is suitable for fixed-frequency power control in a direct ac–ac converter, featuring high performances of skin effect, reduction of input (utility line) current fluctuations, and minimization of the size and capacity of the filtering components. Furthermore, this approach can overcome the technical issues of conventional pulse modulations such as pulse frequency modulation (PFM) and pulse density modulation (PDM) such as audible noises with respect to power controller. The essential performances of the proposed pulse modulation are demonstrated by an experiment based on a 2 kW-40 kHz prototype for a fluid water IH appliances in home and consumer appliances. The high-frequency load power regulation, power control range & resolution, power conversion efficiency, and soft-switching of a bidirectional switch are revealed, after which the validity is evaluated from a practical point of view.

This paper presents a single-stage wireless motor driver (WMD) based on a modified Class-E resonant topology for DC motor control. An active clamping circuit and a high-order harmonic suppression circuit are implemented to enhance switch reliability and optimize power transfer efficiency. Additionally, a variable inductor module, along with a stepped-core transmitter (Tx)/receiver (Rx) coupler set, is integrated into the resonant tank to enable fixed-frequency switching while maintaining high efficiency during coil misalignment. The paper covers system descriptions, circuit operating modes, steady-state analysis, and the design process of the magnetic components. A 180-W power rating WMD prototype was constructed to validate the theoretical analysis. The resonant tank demonstrated an efficiency improvement of up to 4.79%, and the system achieved a maximum efficiency of 89.72%, offering practical validation of the proposed concepts.