Three DC/DC converter topologies suitable for high-power-density high-power applications are presented. All three circuits operate in a soft-switched manner, making possible a reduction in device switching losses and an increase in switching frequency. The three-phase dual-bridge converter proposed is shown to have the most favorable characteristics. This converter consists of two three-phase inverter stages operating in a high-frequency six-step mode. In contrast to existing single-phase AC-link DC/DC converters, lower turn-off peak currents in the power devices and lower RMS current ratings for both the input and output filter capacitors are obtained. This is in addition to smaller filter element values due to the higher-frequency content of the input and output waveforms. Furthermore, the use of a three-phase symmetrical transformer instead of single-phase transformers and a better utilization of the available apparent power of the transformer (as a consequence of the controlled output inverter) significantly increase the power density attainable. >

A three-phase soft-switched high power density DC/DC converter for high power applications

The performance of a high-power, high-power-density DC-to-DC converter based on the single-phase dual active bridge (DAB) topology is described. The dual active bridge converter has been shown to have very attractive features in terms of low device and component stresses, small filter components, low switching losses, high power density and high efficiency, bidirectional power flow, buck-boost operation, and low sensitivity to system parasitics. For high output voltages, on the order of kilovolts, a cascaded output structure is considered. The effects of snubber capacitance and magnetizing inductance on the soft switching region of control are discussed. Various control schemes are outlined. Coaxial transformer design techniques have been utilized to carefully control leakage inductance. The layout and experimental performance of a prototype 50 kW 50 kHz unit operating with an input voltage of 200 V DC and an output voltage of 1600 V DC are presented. >

Performance characterization of a high-power dual active bridge DC-to-DC converter

A DC/DC power converter suitable for high power applications has an input converter which converts the DC input voltage to an AC voltage and supplies this voltage to a transformer. The output of the transformer is provided to an output converter which converts the AC to a DC output voltage at a controlled level to a load. Both the input and output converters are composed of active gate controlled switching devices and are switched in a soft-switched manner to minimize switching losses and increase switching frequency. The converters can be implemented in single phase or polyphase configurations and can be controlled to closely maintain the output voltage provided to the load at a desired level.

Power conversion apparatus for DC/DC conversion using dual active bridges

A rechargeable battery which may be used with most presently available hearing aids (or other appliances) with no modification to the existing hearing aid is needed in order to use the described wireless charging system. The battery may be known a “Dynamic battery” as the battery is actively charged by means of an inductor circuit built into the battery housing itself or added onto the battery. The hearing aid may simply be placed within the charger housing (or cradle) to charge the battery. No electrical connection by either wires or electrical contacts is needed to recharge the battery, which is located inside the hearing aid housing. Moreover, the battery need not be removed from the hearing aid (or other appliance).

Wireless battery charging system for existing hearing aids using a dynamic battery and a charging processor unit

An inverse dual converter circuit (20) provides continuous voltage step-up or step-down control over a wide range and without the need of a transformer. The converter comprises an input DC voltage source (22) for generating an input DC voltage. An inverse dual converter bridge receives the input DC voltage and comprises a network of source voltage converters (26), an AC link circuit (28), and a network of load voltage converters (32). The source voltage converters (26) and load voltage converters (32) operate at the same frequency, but at a different phase. The AC link circuit (28) stores energy to be transferred from the source voltage converters (26) to the load voltage converters (32) and supplies reverse voltage bias for commutation. The inverse dual DC-DC (20) converter may include circuitry (180) for controlling the output DC voltage and for regulating output current continuity. Topological variations of the basic circuit include transformer coupled (140), multi-phase (80) and multi-pulse derivations. The single-phase inverse dual converter circuit (20) offers a buck-boost operation over a wide range without a transformer, bi-directional power flow, and complimentary commutation of converters. The commutation mechanism provided in the inverse dual converter circuit (20), when combined with gate turn-off switch thyristors provides zero current switching. This allows operation at high frequencies in high-power applications, with high efficiency.

Inverse dual converter for high-power applications

A power supply capable of transferring power at high current and voltage levels to a load which may be highly inductive. The power supply includes an inverter for receiving DC power and inverting it to an AC intermediate signal. The intermediate signal is rectified by a converter to provide a DC output voltage to a load. Commutation of the controlled rectifying devices within the inverter and converter are provided by capacitors connected across the output terminals of the inverter. The DC output voltage provided to the load is controlled by the frequency of the firing signals provided to the controlled rectifying devices within the inverter. A large energy storage inductor, which may be superconductive, is connected to the inverter and may be utilized to provided the pulses of power required by the load. A converter connected to an AC power system is provided to supply external power and to recharge the current flowing in the energy storage inductor. Power may be transferred reversibly, from the energy storage inductor to a load inductor and back again.

Power supply for high power loads

An inductor device having a superconducting coil winding capable of maintaining a relatively large current flowing therethrough, and a normal conducting shield winding surrounding the superconducting coil. The superconducting coil and the shield are electrically connected in parallel with the shield functioning to maintain the current and the magnetic field in the superconducting coil substantially constant. The superconducting inductor device can be used to store energy and to return the stored energy to an energy consuming load over a relatively short period without incurring large losses in the superconducting material. This result is obtained by making the self inductance of the shield substantially equal to the mutual inductance between the shield and the superconducting coil, or by inserting a controlled compensating voltage source in series with the shield, so that pulse currents are conducted by the shield. Proper spacing of the shield windings around the superconducting coil will result in substantially no magnetic field present in the coil due to current in the shield.

Shielded superconducting inductor device

An electrical magnet having at least one turn of electrical conductor which is continuously rippled in small radius arcs around is larger circumference. Each ripple in the conductor is formed to lie in a plane normal to the net magnetic field experienced by that ripple. For the special case of a planar turn of conductor, the ripples lie in substantially the same plane as the conductor turn itself. When current is flowing in the rippled conductor, the conductor will experience a magnetically induced force directed outward normal to the conductor. To oppose this outwardly directed force, the conductor is provided support by means which engage the conductor at the inner portions of the conductor between the ripples therein. The support means may consist of members or columns extending to a solid circular wall as, for example, a wall formed in bedrock. The tensile load in the rippled conductor is much less than in an unsupported large radius circular conductor, and, in addition, the rippled conductor is capable of undergoing expansions and contractions without building up damaging strain levels in the conductor. A superconducting rippled conductor magnet may be thermally insulated from warm support structure by thermal shields and vacuum dewars which are also rippled.

Support structure for rippled superconducting magnet

An electrical magnet having a support structure which comprises a flat plate of structural material and abutment means engaging the conductor of the electrical magnet to the plate. The abutment means may comprise a groove in a face of the plate which receives and restrains the conductor, a raised flange on a face of the plate which forms such a groove, or a flange which extends around and is affixed to the periphery of the plate and which is formed to fit tightly over a coiled conductor. When current is flowing in the conductor of the magnet, all points on the conductor will experience a magnetically induced force, one component of which is in an outward direction parallel to the plane of the plate. The abutment means opposes this component of the force and transmits it to the plate, which is consequently stressed in tension in two dimensions. Several individual magnets supported by the support structure may be combined to form large magnets having solenoidal, toroidal or other configurations. The magnets may be built with a normal or a superconducting electrical conductor.

Harold A. Peterson

Papers

Power supply for high power loads

Shielded superconducting inductor device

Support structure for rippled superconducting magnet

Support structure for a superconducting magnet