This paper presents a domino wireless power transfer system designed to provide flexible constant-voltage (CV) output in each relay unit. Importantly, the voltage level of each CV output can be independently and flexibly preconfigured, establishing a reconfigurable output paradigm. The core innovation lies in the use of an inductor-capacitor-capacitor-series (LCC-S) compensation network in each relay unit, allowing for the intentional design of compensated inductance and mutual inductance to achieve various CV lift ratios. Additionally, four typical CV scenarios are thoroughly analyzed: constant, monotonically increasing, monotonically decreasing, and high-low jumps. Finally, an experimental prototype has been developed, and additional measured waveforms will be presented to demonstrate the effectiveness of the proposed system.

This study introduces an power-boosted wireless power transfer (PBWPT) system by concurrently utilizing both the 1stand 3rdharmonics of the square voltage generated from the inverter. The key is to integrate a bipolar coil inside the unipolar coil to establish two decoupled power transfer channels in the same space. Specifically, both sides adopt symmetric coil structures while the unipolar and bipolar coils resonant at the 1st and 3rd harmonics, respectively. Under the same input DC voltage and transfer distance, compared with the traditional fundamental-harmonic single-channel WPT system, this approach can improve the average output power by 66.03% and the average system efficiency by 12.43% in the load range of 1-100Ω, respectively. Finally, the theoretical analysis and simulation results are given to validate the effectiveness of the proposed PBWPT system.

The modular multilevel converter (MMC) has become a promising topology in long-distance and large-capacity HVDC areas. Though the traditional hybrid MMC can block the DC short-circuit current to ensure safe operation, it suffers from the control complexity caused by the capacitor voltage balancing. This paper presents a novel hybrid MMC composed of a self-balancing submodule (SBSM) and a self-blocking SBSM (SB2SM). The SBSM and SB2SM have similar structures and the same operation principle, and their capacitor voltages can be self-balanced through additional balancing branches. These features make the control strategy of the hybrid MMC very simpler and there are no longer the computing and communication burdens. Moreover, the SB2SM can generate a negative level of twice the capacitor voltage when a DC short-circuit fault happens. Hence, the hybrid MMC is capable of blocking the DC short-circuit fault. In addition to the circuit configuration and operation, the features of the DC fault blocking and capacitor voltage balancing are analyzed in detail. Finally, the feasibility of the hybrid MMC is verified by simulation.

This paper introduces a novel approach for simultaneously achieving receiver resonant frequency tracking and mutual inductance identification in a wireless power transfer (WPT) system. This method relies solely on the primary-side controller and a switch-controlled capacitor (SCC). The proposed technique utilizes a dual-loop structure, where a gradient descent (GD) controller functions as the outer loop, and zero-phase angle (ZPA) control by the SCC serves as the inner loop. This control-based identification method can accommodate parameter fluctuations on the primary side and act as an auxiliary detection circuit for SAE J2954-compatible devices prior to high-power charging. Both simulations and experiments have been conducted to validate the proposed method. Compared to the slow identification speeds of traditional optimization algorithms, this approach can complete the identification process within 200 milliseconds, achieving maximal identification errors of 1.21 µH for mutual inductance and 1.47% for receiver resonant frequency.

Inductive power transfer (IPT) systems conventionally operate at the natural resonant frequency for efficient power transmission, but their output power is sensitive to mutual inductance changes. Recent studies have shown that parity-time-symmetric IPT systems have two splitting frequencies in the strongly coupled range, enabling robust wireless power transfer with constant output power and high efficiency. Self-excited oscillation circuits can automatically track these optimal frequencies without measuring circuit parameters. However, practical self-oscillating systems contain voltage harmonics and feedback delays, which are often ignored in the analysis of steady-state performance. In this paper, the effects of high-order harmonics and time delay on steady-state frequencies are systematically analyzed. First, the formula of ideal bifurcation frequency is derived based on the zero-phase-angle condition. Then, steady-state conditions under square wave voltage and feedback delays are obtained using the Fourier series and superposition theorem. Finally, numerical examples demonstrate that exceptional points shift towards stronger coupling due to harmonics, whereas time delay could eliminate frequency bifurcation.

In this paper, a robust closed-loop speed control for wireless motor systems is proposed with the consideration of maximum efficiency point tracking (MEPT). Firstly, the optimal load condition for maximum efficiency point tracking of wireless motor systems is derived, a buck converter with an optimal duty cycle is adopted to achieve impedance match of the wireless power transfer system such that maximum efficiency can be guaranteed. Then, an integral fixed-time sliding mode (FTSM) control strategy is designed to achieve robust speed tracking control for wireless motors in the presence of parameter variation and external disturbance. The simulation results illustrated superior tracking performance with 15.90% speed tracking overshoot reduction, 26.90% speed tracking error RMS reduction compared with the conventional PID control. And the efficiency of the WPT systems is well maintained at 85.55% simultaneously.

In a wireless power transfer (WPT) system, maximum efficiency can be achieved at specific load conditions by employing impedance matching (IM). Some researchers employ DC-DC converters or additional inductors and capacitors; however, this inevitably leads to an increase in both system cost and complexity. In this paper, we propose a receiver-side variable capacitor system, which comprises a series-connected switch-controlled capacitor (SCC) and a parallel-connected relay-controlled capacitor (RCC). This system aims to achieve maximum efficiency tracking (MET) for WPT across a wide range of load variations. The proposed system autonomously detects variations in the load and adjusts the equivalent capacitor value to achieve MET. Experimental results demonstrate that the proposed system can enhance system efficiency by approximately 5% to 20% when the load varies from 60 Ω to 180 Ω. Finally, we validate the feasibility of the proposed system through experimental verification.

In this paper, a novel kind of wireless motors, namely, the LCC-compensated wireless switched reluctance motor, is proposed and implemented. The definite advantages are that there is no power converter at the motor side and particularly no switched-capacitor array at the transmitter side to realize the multiple-frequency operation. The key is to develop an LCC compensation involving an inductor and two capacitors (the so-called LCC) for a multiple-frequency wireless power transfer system. As a result, only one transmitter is needed to targetedly feed three receivers, which directly energize the three phase windings of the motor. Particularly, there is no need to control switched capacitors to change the resonant frequency of the transmitter. Meanwhile, the burst firing control method is employed to realize the speed control. Both calculation and experimental results are presented to validate the feasibility of the proposed system. In the system prototype, the transmission distance can reach up to 150 mm and the transmission efficiency can be achieved up to 80%.