Demand for supplying contactless or wireless power for various applications, ranging from low-power biomedical implants to high-power battery charging systems, is on the rise. Inductive power transfer (IPT) is a well recognized technique through which power can be transferred from one system to another with no physical contacts. This paper presents a novel bidirectional IPT system, which is particularly suitable for applications such as plug-in electric vehicles (EVs) and vehicle-to-grid (V2G) systems, where two-way power transfer is advantageous. The proposed IPT system facilitates simultaneous and controlled charging or discharging of multiple EVs through loose magnetic coupling and without any physical connections. A mathematical model is presented to show that both the amount and direction of power flow between EVs or multiple systems can be controlled through either phase or/and magnitude modulation of voltages generated by converters of each system. The validity of the concept is verified by theoretical analysis, simulations, and experimental results of a 1.5-kW prototype bidirectional IPT system with a 4-cm air gap. Results indicate that the proposed system is an ideal power interface for efficient and contactless integration of multiple hybrid or EVs into typical power networks.

A Bidirectional Inductive Power Interface for Electric Vehicles in V2G Systems

The progress in the field of wireless power transfer in the last few years is remarkable. With recent research, transferring power across large air gaps has been achieved. Both small and large electric equipment have been proposed, e.g., wireless power transfer for small equipment (mobile phones and laptops) and for large equipment (electric vehicles). Furthermore, replacing every cord with wireless power transfer is proposed. The coupled mode theory was proposed in 2006 and proven in 2007. Magnetic and electric resonant couplings allow power to traverse large air gaps with high efficiency. This technology is closely related to electromagnetic induction and has been applied to antennas and resonators used for filters in communication technology. We have studied these phenomena and technologies using equivalent circuits, which is a more familiar format for electrical engineers than the coupled mode theory. In this paper, we analyzed the relationship between maximum efficiency air gap using equivalent circuits and the Neumann formula and proposed equations for the conditions required to achieve maximum efficiency for a given air gap. The results of these equations match well with the results of electromagnetic field analysis and experiments.

Maximizing Air Gap and Efficiency of Magnetic Resonant Coupling for Wireless Power Transfer Using Equivalent Circuit and Neumann Formula

In this paper, we present a brief overview of historical developments of wireless power and an analysis on the use of Tesla's resonators in domino forms for wireless power transfer. Relay resonators are spaced between the transmitter and receiver coils with the objectives of maximizing energy efficiency and increasing the overall transmission distance between the power source and the load. Analytical expressions for the optimal load and maximum efficiency at resonance frequency are derived. These equations are verified with practical measurements obtained from both coaxial and noncoaxial domino resonator systems. To avoid the use of high operating frequency for wireless power transfer in previous related research, the technique presented here can be used at submegahertz operation so as to minimize the power loss in both the power supply and the output stage. We demonstrated both theoretically and practically that unequal spacing for the coaxial straight domino systems has better efficiency performance than the equal-spacing method. Also, the flexibility of using resonators in various domino forms is demonstrated.

General Analysis on the Use of Tesla's Resonators in Domino Forms for Wireless Power Transfer

In this paper, the effects of the magnetic coupling of nonadjacent resonators on the optimal frequency of wireless power transfer are addressed. A power analysis has been carried out to identify the adjacent and nonadjacent power flow components. It is found that such cross-coupling effects of nonadjacent resonators would cause the maximum efficiency operation to slightly shift away from the resonance frequency of the resonators. Theoretical reasons for such phenomena are provided and experimentally confirmed with practical measurements in a wireless power transfer system comprising several magnetically coupled resonators arranged in a straight domino form.

Effects of Magnetic Coupling of Nonadjacent Resonators on Wireless Power Domino-Resonator Systems

Bidirectional inductive power transfer (IPT) systems are suitable for applications that require wireless and two-way power transfer. However, these systems are high-order resonant networks in nature and, hence, design and implementation of an optimum proportional-integral-derivative (PID) controller using various conventional methods is an onerous exercise. Further, the design of a PID controller, meeting various and demanding specifications, is a multiobjective problem and direct optimization of the PID gains often lead to a nonconvex problem. To overcome the difficulties associated with the traditional PID tuning methods, this paper, therefore, proposes a derivative-free optimization technique, based on genetic algorithm (GA), to determine the optimal parameters of PID controllers used in bidirectional IPT systems. The GA determines the optimal gains at a reasonable computational cost and often does not get trapped in a local optimum. The performance of the GA-tuned controller is investigated using several objective functions and under various operating conditions in comparison to other traditional tuning methods. It was observed that the performance of the GA-based PID controller is dependent on the nature of the objective function and therefore an objective function, which is a weighted combination of rise time, settling time, and peak overshoot, is used in determining the parameters of the PID controller using multiobjective GA. Simulated and experimental results of a 1-kW prototype bidirectional IPT system are presented to demonstrate the effectiveness of the GA-tuned controller as well as to show that gain selection through multiobjective GA using the weighted objective function yields the best performance of the PID controller.

An Optimal PID Controller for a Bidirectional Inductive Power Transfer System Using Multiobjective Genetic Algorithm

Contactless electrical energy transmission becomes more and more attractive for different applications. In this system, the design of the separable transformer is very important. The paper uses the mutual inductance model to analyze the coupling ability of the primary coil and the secondary coil. The investigations are carried out by means of ANSYS simulation and measurements. Through analysis, four factors affecting the output power of the system are presented. So this paper proposes a new method of high coupling coefficient to circle the coil. And simulations on the transformer model based on the new method have been performed. The results indicate the output power of the system is increased by 5% and achieved 87.2%

Contactless electrical energy transmission system using separable transformer

TMs paper presents a design method of multipolar line-start permanent magnet synchronous motor (PMSM) for gearless drive systems. The structures of stator lamination, rotor lamination and stator windings are designed. And how temperature influences the performance of the motor is analyzed. Moreover, how to calculate the air-gap length and the size of permanent magnet are also discussed. The MATLAB program is used to design the prototype. Finally, the starting process of the motor is simulated by ANSOFT according to its model. By simulation, and the distribution and change of magnetic field and the starting performance of motor are presented.

Design and starting process analysis of multipolar line-start PMSM

This paper attempts to present the structures and characteristics of multipolar permanent magnet synchronous submersible motor (MPMSSM) for screw pump. The structures of stator lamination, rotor lamination and stator winding are analyzed. And how temperature influences the performance of the motor is presented. Moreover, how to calculate air-gap length and the size of permanent magnet of MPMSSM are discussed. The MATLAB is used to design the prototype. And, the computer simulation results of magnetic field of the motor are shown by ANSOFT according to its model. The structure and design method of this motor can be used on common MPMSSM.

Research of Multipolar Permanent Magnet Synchronous Submersible Motor for Screw Pump

According to the technical requirement of 11 kW permanent magnet synchronous motor (PMSM) which is used for elevator, this paper presents a position sensorless vector-control system based on model reference adaptive system (MRAS). The inverter-motor drive models are substituted for the decelerator-motor drive models in this drive system based on the digital signal processor (DSP) and using the TMS320LF2407 DSP controller. It fully utilizes the wealthy peripherals and high-speed calculation function of DSP, and uses the vector control method and MRAS strategy. The simulation and experimental results show that the whole control system is simple, feasible and effective

A Position Sensorless Vector-control System Based on MRAS for Low Speed and High Torque PMSM Drive

This paper attempts to present a unified treatment of the single-phase permanent magnet motor that permit the calculation of transient and average asynchronous performance using a combination of symmetrical components and d-q axes theory. The torque simulation results of single-phase capacitor-run PM line-start motor are given by using MATLAB according to its mathematical model. Through simulation, rotor resistance and permanent-magnet how to affect starting performance are presented.

Zhang Bingyi

Papers

Contactless electrical energy transmission system using separable transformer

Design and starting process analysis of multipolar line-start PMSM

Research of Multipolar Permanent Magnet Synchronous Submersible Motor for Screw Pump

A Position Sensorless Vector-control System Based on MRAS for Low Speed and High Torque PMSM Drive

Starting Performance Analysis of Single-Phase Line-Start Permanent Magnet Motor