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This article proposes a planar magnetic integration technique that combines the grid inductors and transformer in the single-stage E-capless electric vehicle charger into one core. The proposed integration technique reduces the number of magnetic components; therefore, the cost, total magnetic core loss, and volume can be significantly reduced. Using the integrated structure, the overall converter power density increases up to 11.1% compared to the nonintegrated one. This article also presents a detailed analysis of the optimal printed circuit board (PCB) winding arrangement considering both ac resistance and winding stray capacitance. Due to the high dc resistance of PCB winding, Litz wire was also considered for the proposed integrated structure. The effectiveness of the proposed structure was validated by implementing it on a 3.7-kW prototype of a single-stage ac–dc converter. Results show that the prototype with the proposed integrated structure achieved higher efficiency with both PCB winding and Litz wire. Peak efficiency of 97.17% and 6.55-kW/L power density were achieved. [ABSTRACT FROM AUTHOR]

In this article, a three-phase single-stage bidirectional ac–dc converter with low component count is proposed. The single-stage structure is configured by integrating a three-phase ac–dc converter and a three-phase dual active bridge converter. The power factor correction and bidirectional power control are performed by adjusting the modulation index of sinusoidal pulse width modulation (SPWM) and phase-shift angle between the primary and secondary bridges. The low-frequency components generated by SPWM are absorbed by fundamental blocking capacitors connected in series with transformer windings, resulting in true high-frequency isolation. The proposed converter can achieve soft-switching of all switching devices even in continuous conduction mode. A 110 Vac, 3 kW, 100 kHz prototype is implemented to validate the proposed concept and demonstrated 95.34% peak efficiency. [ABSTRACT FROM AUTHOR]

Distributed generation (DG) systems should go into intentional islanding operation to back up private emergency loads when the main grid is out of electric power. Conventional utility interactive inverters which are normally operated in current mode must change their operation into voltage mode to ensure stable supply voltage for emergency loads when intentional islanding operation occurs in DG systems. During the transition between current mode and voltage mode, a serious transient problem may occur on the output terminal voltage of utility interactive inverters. This paper proposes a new inverter system and its control algorithm for seamless transfer during intentional islanding operation in DG systems. Filter design guidelines and data for LCL filters that is appropriate for the proposed control algorithm are also presented. Index Terras--Distributed generation (DG) systems, indirect current control, line interactive inverters, seamless transfer.

This paper presents the development of a single-phase utility-interactive inverter for residential power generation to meet the specifications laid down for the 2005 Future Energy Challenge Competition sponsored by U.S. DOE and IEEE. The proposed inverter system is capable of working in both stand-alone and grid-connected mode. A control scheme for implementing both modes of operation is presented, which has simple structure with smaller number of sensors. The proposed control algorithm including the whole system control is implemented on a low cost, fixed-point DSP TMS320F2812. The experimental results from a 1 kW prototype show that the proposed inverter system exhibits not only low THD grid current during the grid-connected mode and well regulated inverter voltage during the stand-alone mode, but also smooth and automatic transfer between the two modes of operation. Index Terms--Fuel cell, Future Energy Challence Competition, grid-connected, LCL filter, P+ resonant, stand-alone, utility-interactive inverter.

This paper presents analysis and control of a hybrid filter that can suppress neutral harmonic currents in three-phase four-wire systems not only with harmonic voltage-source loads but also with harmonic current-source loads. The filter voltampere rating is significantly reduced compared to the conventional neutral-current-suppressing methods. The rectifier part of the neutral harmonic suppressor has been removed by controlling the dc capacitor voltage. The experimental results on a 50-kVA prototype validate the proposed control approach. Index Terms--Active filter, neutral current, three-phase four-wire, zero-sequence, zigzag transformer.

This paper proposes a 10-kW power conditioning system for a 5-kW solid oxide fuel cells (SOFCs) low-voltage battery hybrid power generation that has been developed for participation in the 2003 Future Energy Challenge Competition organized by the U.S. Department of Energy and the IEEE. The objective of the competition was to develop a fuel cell inverter with minimum requirement for cost of $40/kW and efficiency of 90%. The proposed power conditioning system consists of the front-end dc-dc converter, the dc-ac inverter and the bidirectional dc-dc converter. Practical issues such as component rating calculation, high-frequency transformer design, heat sink design, and protection are detailed aiming at the cost and efficiency targets. A low-cost implementation of controllers is discussed along with current-mode control, output voltage regulation with capacitor balancing and an SOC control for battery management. A 10-kW hardware prototype was successfully built and tested in the steady-state as well as in the transient-state. Experimental performances are compared to minimum target requirements of the fuel cell inverter. The cost analysis is done based on the spreadsheets evaluation forms provided in the competition. Index Terms--Fuel cell inverter, future energy challenge, power conditioning system (PCS), solid oxide fuel cell (SOFC)-battery hybrid.

This paper proposes a new three-phase diode rectifier that actively shapes the input current by means of two direct current dc-dc converters operating at continuous conduction mode. The proposed approach draws sinusoidal input current at unity power factor and has output voltage regulation capability. The size and weight of the magnetic devices is reduced since a low-kilovolt-ampere three-phase autotransformer is incorporated and dc outputs of two bridges are directly connected without using low-frequency interphase transformers (IPTs). Index Terms--Active waveshaping, autotransformer, diode rectifier, harmonic mitigation, three-phase power-factor correction.

This paper proposes a new three-phase harmonic-free rectification scheme based on a zero-sequence injection technique. The proposed scheme incorporates two half-bridge inverters and two single-phase transformers to actively and individually shape the positive and negative dc rail currents of the rectifier. The shaped zero-sequence harmonic currents are then circulated through the ac side of the rectifier via a zigzag transformer, resulting in pure sinusoidal input currents in the three-phase diode rectifier. A design example along with component ratings calculation are detailed. Experimental results on a 1.5-kVA prototype are provided to validate the proposed technique. Index Terms--Current injection, harmonic reduction, three-phase diode rectifier, zero sequence.

This letter proposes a reduced-rating hybrid filter to suppress neutral current harmonics in three-phase four-wire systems. Under unbalanced loading, the proposed filter eliminates only harmonics in the neutral current while it does not affect the fundamental. The VA rating of the inverter is significantly reduced compared to the conventional one since only fundamental current due to unbalanced loading could flow through the inverter switch. Index Terms--Harmonic suppressor, neutral current, three-phase four-wire, unbalanced.