Dynamic wireless power transfer (DWPT) can solve the limitation of battery capacity of electric vehicles, and has a good application prospect. In order to solve the problem of weak coupling power supply in a DWPT system with segmented coil mode, an improved real-time strong coupling coil arrangement mode is proposed in this paper. First, the characteristics of the typical coil arrangement mode is analyzed by establishing a DWPT model, in which the mutual inductance decreases sharply in a certain range. In order to ensure the stability of mutual inductance, an improved long receiving coil arrangement mode is proposed, and its advantage of the low coil cost is analyzed theoretically. Further, the optimal process of the improved coil mode is designed based on the genetic algorithm, and an application case of the electric bus is given. Finally, the feasibility of the coil design process is verified by simulation, and the performance advantages of the proposed scheme are verified by a 30 kW WPT platform.

Owing to manufacturing defects and aging, compensation capacitors are inevitably prone to errors, leading to the performance deprecation in a wireless power transfer (WPT) system. This article focuses on the sensitivity analysis of system characteristics to capacitor errors and design methods to improve detuning tolerance. First, the output voltage, power factor, transfer efficiency, and capacitor voltages are derived for LCC -S compensated WPT systems. The worst-case scenarios (i.e., the maximum and minimum values of these indicators) are used to evaluate the effect of capacitor errors. They are calculated under detuned conditions with different inverter quality factors, load quality factors, and the ratios of the primary coil's self-inductance to the compensation inductance. Then, the design constraints are summarized to meet the system requirements considering ±10% capacitor errors. A simplified and easy-to-follow system design process is proposed and a 22-kW wireless charger for an electric bus is designed. Experimental results show that, compared with the traditional design, the change ratio of the output voltage of the proposed design is reduced from between −40.9% and 13.1% to between −21.5% and 12.4%. The lowest power factor is increased from 0.64 to 0.78, and the maximum drop in transfer efficiency is reduced from 9.9 to 5.9%.

Compensation capacitors are naturally susceptible to manufacturing defects and aging effects, leading to the degraded performance of a wireless power transfer (WPT) system. This article focuses on the compensation parameters optimization during the design stage and control strategy during the operation phase to improve the inherent capacitor error tolerance of the WPT system. The Sobol sensitivity method is applied to rank the importance of deviations of three capacitors on the transfer characteristics, and then the method of tracking the secondary resonance frequency is proposed. The numerical method is applied to find the optimal compensation parameters, with the constraint that the output voltage change caused by the shift of the designed compensation condition is limited to be less than ±5%. Experimental results show that with the proposed frequency tracking method and compensation parameter optimization, the deviation tolerance index is decreased from 0.485 to 0.363, showing an improvement of 25.2%, and the minimum power factor is increased from 0.78 to 0.89. Besides, the characteristics of constant primary coil current and voltage gain are almost not affected.

In this study, in order to determine the reasonable accuracy of the compensation capacitances satisfying the requirements on the output characteristics for a wireless power transfer (WPT) system, taking the series-series (SS) compensation structure as an example, the calculation formulas of the output characteristics, such as the power factor, output power, coil transfer efficiency, and capacitors’ voltage stress, are given under the condition of incomplete compensation according to circuit theory. The influence of compensation capacitance errors on the output characteristics of the system is then analyzed. The Taylor expansions of the theoretical formulas are carried out to simplify the formulas. The influence degrees of compensation capacitance errors on the output characteristics are calculated according to the simplified formulas. The reasonable error ranges of the compensation capacitances are then determined according to the requirements of the output characteristics of the system in the system design. Finally, the validity of the theoretical analysis and the simplified processing is verified through experiments. The proposed method has a certain guiding role for practical engineering design, especially in mass production.

Accurate online parameter estimation is crucial for effective system control, monitoring, and maintenance for wireless power transfer (WPT) systems. However, unavoidable and unpredictable deviations in compensation capacitances, caused by factors such as tolerance, environmental conditions, and aging, complicate the parameter estimation process. To address this issue, this article proposes a simple and fast online parameter estimation method based on a frequency adjustment strategy. This method alternates between secondary resonance and nonresonance states, allowing simultaneous estimation of mutual inductance, load resistance, and compensation capacitances using only additional two voltage sensors and three current sensors. Only dc and rms values are utilized, without the need for high-bandwidth communication, switches, or complex algorithms. Experiments demonstrated that the method could simultaneously estimate multiple parameters over a wide power range, with errors below 10% in 7.0 ms. The maximum average errors were 7.0% for mutual inductance, 6.7% for load resistance, and 2.8% for compensation capacitances when combined with efficiency optimization strategies. Furthermore, the frequency adjustment selection principles were outlined. Both analysis and experiments confirmed that the brief detuning duration and a 2% frequency deviation had minimal impacts on WPT systems, thus enabling a cost-effective and fast solution for practical applications.

In this paper, we propose a novel switching strategy for maintaining constant output voltage in dynamic wireless power transfer (DWPT) systems, leveraging a positioning scheme based on mutual inductance estimation. First, we enhance the secondary coil positioning method by improving mutual inductance estimation to support various load types. Furthermore, a practical secondary coil positioning scheme is introduced to address real-world challenges in DWPT systems, factoring in parameter fluctuations and time delays. Following this, steady-state and transient models of the primary coil switching process are derived to thoroughly assess the switching dynamics and identify potential safety risks. Based on these insights, we develop a primary coil switching strategy that guarantees both system safety and consistent output voltage while facilitating practical implementation. Simulation and experimental results validate the design objectives of the secondary coil positioning scheme and primary coil switching strategy. Furthermore, we analyze the mutual interactions between the positioning scheme and switching strategy, confirming their compatibility and effectiveness under simultaneous operation.