Ekkachai Mujjalinvimut

To address the need for a reproducible design process for an efficient wireless electric vehicle (EV) charging system that guarantees compliance with the SAE J2954 standard, this paper proposes a systematic, flowchart-based optimization technique. Unlike methods that focus solely on coil performance, the proposed approach integrates standard-specific constraints, such as inductance and geometric limits, from the outset to ensure the final design meets stringent performance benchmarks for efficiency and misalignment tolerance. A circular flat spiral coil structure has been adopted for both the transmitter and receiver coils to enhance manufacturability and achieve uniform magnetic field distribution. A flowchart-based design technique has been developed to optimize key coil parameters, including the number of turns and coil diameters, subject to constraints of 200 µH inductance and a maximum outer diameter of 700 mm. Finite element analysis (FEA) simulations verify that the proposed design approach achieves maximum magnetic coupling under various air gap distances and misalignment conditions. An experimental validation of a 2-kW prototype demonstrates close agreement with simulations, achieving coil-to-coil efficiencies between 92.61% and 96.67%, and overall system efficiency exceeds 80% under all tested conditions. These results confirm that the proposed design method effectively meets performance requirements set by the SAE J2954 standard.

This paper proposes a novel filter-free recursive gain controller (RGC) for frequency regulation in nonlinear hydraulic turbine regulating systems (HTRS). The controller systematically constructs a nonlinear feedback law that ensures all closed-loop signals converge exponentially to user-defined bounded regions. Stability is rigorously proven using Lyapunov analysis, avoiding the ‘‘complexity explosion’’ problem inherent in conventional backstepping methods. Unlike dynamic surface control (DSC) or command-filtered backstepping control (CFBC), the proposed approach does not require any filtering mechanisms, simplifying implementation. Instead, it uses fictitious signals to estimate virtual controls, resulting in a simple structure governed solely by tunable gains. Comprehensive simulations under severe fault conditions demonstrate that the filter-free RGC achieves robust frequency stability with superior transient performance—faster settling times, reduced overshoot, and enhanced damping—compared to standard backstepping, DSC, CFBC, and synergetic control.

Despite the increasing popularity, unmanned aerial vehicles (UAVs) are often hindered by limited battery endurance and complexities of in-flight recharging. This paper presents an extended-range wireless power transfer (WPT) system designed for simultaneous in-flight charging of dual drones. By employing a bifurcation approach, the system uses bifurcation-induced zero-phase angle (ZPA) frequencies to achieve coupling-independent current gain. This allows the system to maintain a constant battery charging current across dynamically varying coupling conditions, without the need for sensors or communication modules on the receiver drones. Finite element simulation study confirms the magnetic flux density characteristics, desired for practical operation constraints. An experimental study on a 500 W prototype demonstrates the proposed system’s effectiveness. The dual-receiver configuration successfully maintains a constant 5 A charging current of each drone while extending the operational air gap range by 16.7% (from 150 mm to 175 mm) compared to single-receiver scenarios. This work presents a practical solution that mitigates misalignment and air gap variation issues to enhance UAV flight endurance, an important step for drone operations during prolonged missions.

The output voltage of capacitive power transfer (CPT) system will change if the load resistance is varied. This paper presents a method to regulate the output voltage using a controller that is located on the primary side, known as the primary side control technique. It does not require any additional components and wireless feedback, which lowers the cost and complexity of CPT system compared to the conventional control technique. Instead of directly measuring the output voltage on secondary side, it is estimated through the measured capacitor voltage on primary side. Modified sine wave control of the full-bridge inverter is adopted to regulate the output voltage. The proposed control technique is validated by the simulation via PSIM software using the practical parameters of capacitive coupler presented in the literature. Simulation results of the output voltage control against the step change in desired output voltage and load resistance indicate the performance of proposed control technique.

In a dynamic inductive power transfer (D-IPT) system, significant variations in magnetic coupling occur as the secondary coil moves along the roadway above the primary coils. These variations significantly impact the output power pulsation and result in low power efficiency. This article introduces the concept of a D-IPT system operating under the bifurcation phenomenon that achieves coupling-independent and load-independent output characteristics by tracking the new zero phase angle (ZPA) frequency. The series-series (SS) topology was chosen as the IPT system can control the secondary current via the input current under the bifurcation phenomenon. Furthermore, the proposed circuit configuration on the primary side eliminates the high-power loss associated with SS topology within non-coupling primary coils—the primary coils are not synchronized with the vehicle—at the new ZPA frequency under the bifurcation phenomenon. The experimental results from the hardware prototype illustrated that the output power at the secondary side remained relatively constant, around 200 W. This was achieved by regulating the secondary current via the input current throughout the experimental distance.

Power transfer capability of the capacitive power transfer (CPT) system is dependent on the dimensions of capacitive coupler, which should be correctly designed to meet the required amount of output power. This paper presents a guideline to design the conductive plates used in CPT system to achieve a targeted output power. For a given operating frequency, resonant inductance, DC input voltage, load resistance, and the air gap between plates, the required cross-sectional area of conductive plates is obtained using this guideline. It has been guided through the design procedure which is explained in detail. A step-by-step guide to design a 5-watts CPT system is demonstrated as a design example. The proposed design guideline is verified by the experiment which shows the closeness between measured and targeted output power. Design error is obtained as low as 3.6 percent.

To achieve a free-positioning wireless power transfer (WPT) system, the output power must be regulated throughout the operation. This paper presents a novel output power control of a WPT system, based on the model predictive control (MPC). The output power is predicted by utilizing the system’s mathematical model. The optimal duty cycle for a desired output power is obtained through the minimization of the objective function, which is simple and easy to implement, with no need for gain tuning. The proposed controller is implemented on the primary side, without any measurement or communication devices on the secondary side. This reduces the cost, size, and complexity of the WPT system. The load resistance and mutual inductance identification method is also introduced. It is based on the reflected impedance knowledge, where only the information of primary current is required. Experimental results of the output power step response show better performance compared with conventional Proportional-Integral (PI) control. The proposed controller is experimentally validated on a 200 W kettle. The output power can be kept constant at 200 W while the kettle is laterally moved. With the proposed controller, the kettle can be placed freely up to 7 cm from the align position, which is 63.64% of the primary coil’s outer radius.

This paper presents a technique to control the output voltage of a series-parallel (SP) topology inductive power transfer (IPT) system using only a controller, located on the primary side. This reduces the cost, size, complexity and loss of the system compared to conventional IPT dual-side controllers. An asymmetrical duty cycle control (ADC) of full-bridge inverters was used to control the DC output voltage to its designed value. Additionally, a zero voltage switching (ZVS) operation can be obtained at all power levels by varying the switching frequency of the inverter. Theoretical analysis was performed through a mutual inductance coupling model and verified by computer simulation. Experimental results of the circular magnetic structure IPT system with an adjustable air-gap confirm the validity of the proposed controller. The system efficiency was improved throughout the operation and the improvement became obvious as the output power was decreased.