In this paper, we introduce the basic principles of wireless power transfer using magnetic field resonance and describe techniques for the design of a resonant magnetic coil, the formation of a magnetic field distribution, and electromagnetic field (EMF) noise suppression methods. The experimental results of wireless power transfer systems in consumer electronics applications are discussed in terms of issues related to their efficiency and EMF noise. Furthermore, we present a passive shielding method and a magnetic field cancellation method using a reactive resonant current loop and the utilization of these methods in an online electric vehicle (OLEV) system, in which an OLEV green transportation bus system absorbs wireless power from power cables underneath the road surface with only a minimal battery capacity.

Coil Design and Shielding Methods for a Magnetic Resonant Wireless Power Transfer System

High power wireless resonant energy transfer system

An inductively coupled power distribution system for moving vehicles, in which resonating primary circuits distribute power for resonating secondary circuits to collect and use in an optimised manner. In order to have all circuits resonating at substantially the same frequency, means to detect and adjust resonating components are used, for example the circuit (700) illustrates a frequency drift compensator applicable to several embodiments wherein elements (702-709) compare the present frequency to a reference voltage and cause the driver (711) to be ON or OFF accordingly. Switches (712 and 713) are thereby driven CLOSED or OPEN respectively and when CLOSED, the supplementary capacitors (714 and 715) are included with the main capacitor (716) in the primary resonant circuit. Dithering or pulsed control provides a continuous control of resonance as the system takes some milliseconds to respond.

A non-contact power distribution system

A roadway-powered electric vehicle (RPEV) system includes: (1) an all-electric vehicle; and (2) a roadway network over which the vehicle travels. The all-electric vehicle has one or more onboard energy storage elements or devices that can be rapidly charged or energized with energy obtained from an electrical current, such as a network of electromechanical batteries. The electric vehicle further includes an on-board controller that extracts energy from the energy storage elements, as needed, and converts such extracted energy to electrical power used to propel the electric vehicle. The energy storage elements may be charged while the vehicle is in operation. The charging occurs through a network of power coupling elements, e.g., coils, embedded in the roadway. The RPEV system also includes: (1) an onboard power meter; (2) a wide bandwidth communications channel to allow information signals to be sent to, and received from, the RPEV while it is in use; (3) automated garaging that couples power to the RPEV for both replenishing the onboard energy source and to bring the interior climate of the vehicle to a comfortable level before the driver and/or passengers get in; (4) electronic coupling between “master” and “salve” RPEV's in order to increase passenger capacity and electronic actuators for quick-response control of the “slave” RPEV; (5) inductive heating coils at passenger loading/unloading zones in order to increase passenger safety; (6) an ergonomically designed passenger compartment; (7) a locating system for determining the precise location of the RPEV; and (8) a scheduling and dispatch computer for controlling the scheduling of RPEV's around a route and dispatch of RPEV's based on demand.

Roadway-powered electric vehicle system having automatic guidance and demand-based dispatch features

A power pick-up for an Inductively Coupled Power Transfer (ICPT) system is provided having a resonant pick up circuit. The natural frequency of the pick-up circuit may be varied by controlling the conductance or capacitance of a variable reactive in the resonant circuit. The load being supplied by the pick-up circuit is sensed, and the effective capacitance or inductance of the variable reactive component is controlled to vary the natural resonant frequency of the pick-up circuit to thereby control the power flow into the pick-up to satisfy the power required by the load.

Methods and apparatus for control of inductively coupled power transfer systems

An inductive energization system for moving vehicles includes wayside inductors under the roadway and pickup inductor circuits in electrically powered vehicles. A pickup power controller has a switching circuit, including a zero-crossing trigger circuit, a current limiting inductor, and a bleed resistor. The controller provides for fast switching, desirable for closed loop control of the inductive energy transfer system, as well as low harmonic distortion of waveforms, low acoustic noise, and low maintenance requirements. The pickup inductor of the preferred embodiment has rigid metal conductors bonded together into a single member, allowing this element to serve as both a current carrying element as well as a primary structural member of the pickup inductor. The roadway inductor is split into many segments. Sensors in the roadway detect when vehicles requiring power are present, and a wayside inductor segment controller responds to the sensory signals by energizing only those wayside inductor segments needed to transfer power to such vehicles. This control methodology improves the energy efficiency of the system. In addition, the roadway sensors can be designed to detect identification signals broadcast by vehicle identification transmitters, thereby enabling the system to charge for energy usage by each vehicle.

Khosrow Lashkari

Papers

Inductive energization system and method for vehicles