Wireless power transfer (WPT) for portable electronic applications has been gaining a lot of interest over the past few decades. This study provides a comprehensive review of the recent advancements in WPT technology, along with the challenges faced in its practical implementation. The modeling and design of WPT systems, including the effect of cross-coupling in multiple receivers, have been discussed and the techniques for efficiency improvement have been highlighted. The challenges of coil design, EMI shielding, and foreign object detection have been pointed out and various cutting-edge solutions have been presented. With improvements in wide bandgap technology, there is a push to operate WPT systems at mega-hertz frequencies. The reason for this is twofold: the miniaturization of the system and the ability to achieve a better magnetic link efficiency. However, with higher frequency comes the challenge of operating the power electronic components efficiently by using soft-switching techniques. Hence, an in-depth discussion on soft-switched topologies such as the Class D and Class E converters and their variations has been provided. Finally, the effects of magnetic field exposure on humans along with safety standards have been discussed.

This paper proposes a novel Lie group controller for speed sensorless control of a surface-mounted Permanent Magnet Synchronous Motor (SPMSM) fed by a solar microinverter. Solar-fed motor drive poses significant challenges due to the inherent solar power fluctuations and small storage capability of solar microinverters. Thus, the reliable operation of a solar-powered motor drive requires a control methodology that delivers optimal performance for the fluctuating solar power along with fast dynamic behavior to handle source/load transients. The proposed control strategy quickly modulates the drive frequency based on Lie theory in response to any transients, maximizing the motor's torque output. The proposed control method has better dynamic performance, ease of start-up, and is simpler to implement compared to existing observer-based vector control methods. Theoretical analysis as well as simulation and experimental results prove the effectiveness of the proposed control method.

This paper presents a novel Lie group-based control scheme for off-grid operation of single-phase microinverters. The off-grid operation of solar microinverters poses several challenges due to their small energy storage capacity, impacting their ability to handle sudden load transients. This paper shows that the rotation groups, particularly the special orthogonal group SO (2), is the natural framework to design the control system for off-grid operation. The proposed controller offers a fast transient response and reliable operation against severe load fluctuations. In the proposed methodology, SO (2) group and its Lie Algebra so (2) are used to generate the appropriate current reference and in turn control the voltage at the point of common coupling (PCC) for parallel microinverters. The control system is robust against variations in the output impedance, eliminating the need for virtual impedance compensation to maintain system stability. By avoiding the voltage reference drop caused by impedance compensation, the proposed controller can effectively regulate the output voltage with smaller deviations from the nominal voltage. Unlike conventional droop methods, the proposed controller can effectively handle any type of linear and nonlinear loads without requiring structural changes. Experimental results demonstrate the superior performance of the Lie group-based control technique compared to conventional droop control.

As reliance on sustainable energy grows, the demand for efficient, high-performance energy storage systems becomes increasingly critical, especially in uninterruptible power supplies (UPS), where reliability and fast transitions are essential. Supercapacitors, with their high power density and rapid charging capabilities, are emerging as strong alternatives to lithium-ion batteries in UPS systems. This paper presents a novel real-time estimation technique for monitoring supercapacitor parameters within a UPS, focusing on the dynamic behavior of these parameters and their evolution over the system’s lifecycle. The proposed estimator demonstrates exceptional accuracy, achieving less than 1% error within 120 ms of startup and nearly zero error thereafter. The estimator’s performance remains robust even as supercapacitor parameters change due to aging effects over the lifespan. The UPS system features a modular design, enabling scalability to accommodate higher power requirements or longer backup durations and adaptability to various supercapacitor types. Experimental results highlight the system’s robustness in both charging and backup modes, emphasizing the potential of supercapacitors as key components in future UPS systems.

This article proposes a real-time dynamic maximum efficiency tracking algorithm for wireless power transfer (WPT) systems with multiple receivers. The algorithm sequentially varies the net reactance of each of the receivers using switched capacitor circuits (SCCs) to reach the maximum efficiency point (MEP). The MEP in multiple-receiver systems varies in the presence of cross-coupling. This article provides an in-depth analysis of the effects of cross-coupling and proves that cross-coupling could be beneficial or detrimental to efficiency, depending on circuit conditions such as the load resistances and coupling factors among the coils. Hence, unlike previous research, this article emphasizes the improvement of the link efficiency in the presence of cross-coupling rather than the complete elimination of its effects. Experimental results have been included for a single-transmitter and two-receiver system to validate the feasibility of the proposed algorithm.

In this paper, a soft-switched three-phase resonant converter with a low quality factor (Q) design is proposed for Photovoltaic (PV) energy harvesting systems with a very wide range of operating conditions. Due to the low quality factor (Q ≤ 1), the voltage stress across the capacitors is drastically reduced. However, a major challenge of using a low Q design is the wide switching frequency range required for operation over a wide range of load and input conditions. In order to reduce the switching frequency range, this paper introduces a hybrid modulation technique employing asymmetric pulse width modulation (APWM) along with variable frequency modulation. The proposed modulation scheme also substantially extends the soft-switching range of the converter from full-load upto 10–35% load condition over a wide range of line voltages. To sustain soft-switching in the entire operating region of the converter, the converter is operated in a hybrid structure with single-phase and burst modes at light load conditions. A comprehensive time-domain analysis of the proposed converter is presented, which greatly improves accuracy over conventional frequency-domain modeling. Experimental results from a 1 kW prototype are presented to verify the performance of the converter and validate the theoretical analysis.