Andrew Ong

An Efficiency Optimization Scheme for Bidirectional Inductive Power Transfer Systems

Unidirectional inductive power transfer systems allow loads to consume power, while bidirectional inductive power transfer (BIPT) systems are more suitable for loads requiring two-way power flow such as vehicle to grid applications with electric vehicles. Many attempts have been made to improve the performance of BIPT systems. In a typical BIPT system, the output power is controlled using the pickup converter phase shift angle, while the primary converter regulates the input current. This paper proposes an optimized phase-shift modulation strategy to minimize the coil losses of a series-series compensated BIPT system. In addition, a comprehensive study on the impact of power converters on the overall efficiency of the system is also presented. A closed-loop controller is proposed to optimize the overall efficiency of the BIPT system. Theoretical results are presented in comparison to both simulations and measurements of a 0.5 kW prototype to show the benefits of the proposed concept. Results convincingly demonstrate the applicability of the proposed system offering high efficiency over a wide range of output power.

Cascaded multilevel converter based bidirectional inductive power transfer (BIPT) system

A typical low power IPT system employs an H-Bridge converter with a simple control strategy to generate a high frequency current from DC power supply. This paper proposes a cascaded multilevel converter for bidirectional IPT (BIPT) systems, which is suitable for low to medium power applications as well as for situations such as PV cells where several individual DC sources are to be utilized. A novel modulation strategy is proposed for the multilevel converter with the aim of minimizing switching losses. Series - Series (SS) compensation circuit is adopted for the IPT system and a mathematical model is presented to minimize the coil losses of the system under varying output power. Theoretical results presented in comparison to the simulations to demonstrate the applicability of the proposed concept and the validity of the developed model. The experimental results show the feasibility of the proposed phase shift modulation.

Coil enhancements for high efficiency wireless power transfer applications

Achieving high efficiency with improved power transfer range and misalignment tolerance is the major design challenge in realizing Wireless Power Transfer (WPT) systems for industrial applications. Resonant coils must be carefully designed to achieve highest possible system performance by fully utilizing the available space. High quality factor and enhanced electromagnetic coupling are key indices which determine the system performance. In this paper, design parameter extraction and quality factor optimization of multi layered helical coils are presented using finite element analysis (FEA) simulations. In addition, a novel Toroidal Shaped Spiral (TSS) coil is proposed to increase power transfer range and misalignment tolerance. The proposed shapes and recommendations can be used to design high efficiency WPT resonator in a limited space.

Efficiency optimization for bidirectional IPT system

Compared with unidirectional inductive power transfer (UIPT) systems which are suitable for passive loads, bidirectional IPT (BIPT) systems can be used for active loads with power regenerative capability. There are numerous BIPT systems that have been proposed previously to achieve improved performance. However, typical BIPT systems are controlled through modulation of phase-shift of each converter while keeping the relative phase angle between voltages produced by two converters at ± 90 degrees. This paper presents theoretical analysis to show that there is a unique phase shift for each converter at which the inductive coils losses of the system is minimized for a given load. Simulated results of a BIPT system, compensated by CLCL resonant networks, are presented to demonstrate the applicability of the proposed concept and the validity of the mathematical model.

A modified cascaded multilevel converter topology for high power bidirectional inductive power transfer systems with the reduction of switching devices and power losses

Several power converters have been proposed for Inductive Power Transfer (IPT) systems to generate high frequency current to excite the primary side inductive coils/tracks. This paper proposes a modified cascaded multilevel converter (MC) topology based bidirectional IPT (BIPT) system with reduced number of power electronic components and low converter losses. The proposed topology is suitable for high power - low to medium voltage IPT applications. The simulation results are presented to demonstrate the feasibility of the proposed system.

A multilevel converter topology based bidirectional inductive power transfer system with improved characteristics

LCL network is one of the best choices for compensating bidirectional inductive power transfer (BIPT) systems. However, H-Bridge power converter of the conventional BIPT systems generates highly distorted AC current which results in reduced overall system efficiency particularly in high power BIPT systems. In order to overcome this drawback, a multilevel converter (MC) with selective harmonic distortion (SHE) modulation method is presented in this paper to eliminate high order harmonic components in converter voltages at both sides of BIPT systems. The proposed MC topology is constructed using a modified H-Bridge converter with minimum number of power switches. The proposed topology is suitable for low to medium power applications. The simulation results demonstrate the feasibility of the proposed scheme.

Transmitter Pulsation Control for Dynamic Wireless Power Transfer Systems

Wireless power transfer (WPT) is a convenient, flexible, and safe alternative to its wired counterpart. Due to these benefits, WPT has seen rapid growth in recent years. Typical WPT systems are usually used for static applications, where the load operates within a predefined area. On the other hand, dynamic WPT (D-WPT) is usually used to power loads which dynamically change their positions, and one of the ways to achieve this is by increasing the overall charging area via multiple transmitters (Txs). Multiple Txs require communication and control, which increases the overall complexity of the system. This paper proposes a control algorithm which aims to maintain the overall efficiency of the D-WPT system by turning on and off the Tx when the mobile receiver (Rx) approaches and departs, respectively. Transient analysis of the D-WPT system is used to derive its control variables. In addition, energy and power loss of this proposed control algorithm are also investigated. The feasibility of the proposed control algorithm is demonstrated with 1-Tx and 3-Tx experimental setups. The experimental results validate the theoretical analysis model and the proposed control algorithm, and the standby (when not charging) input power forms 7.6% of the charging input power.