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In this paper, the development of a low cost fuel cell inverter system is detailed. The approach consists of a three-terminal push-pull dc-dc converter to boost the fuel cell voltage (48 V) to [+ or -]200 VDC. A four switch [insulated gate bipolar transistor (IGBT)] inverter is employed to produce 120-V/240-V, 60-Hz ac outputs. High performance, easy manufacturability, lower component count, safety and cost are addressed. Protection and diagnostic features form an important part of the design. Another highlight of the proposed design is the control strategy, which allows the inverter to adapt to the requirements of the load as well as the power source (fuel cell). A unique aspect of the design is the use of the TMS320LF2407 DSP to control the inverter. Two sets of lead-acid batteries are provided on the high voltage dc bus to supply sudden load demands. Efficient and smooth control of the power drawn from the fuel cell and the high voltage battery is achieved by controlling the front end dc-dc converter in current mode. The paper details extensive experimental results of the proposed design on Department of Energy (DoE) National Energy Technology Laboratory (NETL) fuel cell. Index Terms--Current mode, dc-dc converter, fuel cell.

In this paper, an integrated single-switch approach to improve harmonic performance of standard pulsewidth modulation adjustable-speed drives (ASD's) is presented. The approach is essentially an add-on solution to a standard ASD topology. The approach is based on circulating a third harmonic current to reduce the harmonics of the line current. The dynamic braking chopper available in standard ASD's is used to control the amplitude of the third harmonic circulating current. Analysis, design, and simulations are presented to determine the performance of the proposed scheme with different line impedance and with and without dc-link inductance in the ASD. Utility input current distortion well below 15% is obtained. This paper also presents how this new approach is capable of reducing the harmonic distortion in multiple drives. The paper includes experimental results using a 480-V 10-kW commercial ASD retrofitted with the proposed approach. Index Terms--Adjustable-speed drive, harmonic distortion, power quality, rectifiers, third harmonic injection.