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In this paper, a new three-phase power-factor correction (PFC) scheme is proposed using two single-phase PFC modules. In this approach, the 'three' phase input is first transformed to 'two' phase by means of a 0.14-pu-rated autotransformer. Two standard single-phase PFC modules are then employed to process the 'two' phase power to dc output. Split inductors and diodes are employed to limit interaction between the two PFC stages. Due to cascade operation of two PFC stages, low-frequency (120 Hz) ripple in the dc-link capacitor is cancelled. Detailed analysis and simulation results are presented. A 220-V 1.5-kVA design example along with experimental results is shown. Index Terms--Harmonics, power-factor correction, power quality.

In this paper, a new method is proposed to avoid acoustic-resonance-related instabilities in metal halide lamps when operated with a high-frequency electronic ballast. Angle modulation of the inverter switching pattern has been used as a vehicle to randomize lamp driving frequency and to limit lamp power spectrum below the instability threshold. The optimal modulating pattern is obtained by studying the angle-modulated spectra by periodic and random signals. Analysis is supported by simulations and verified experimentally with the ballasting of 250-W lamps. Index Terms - Acoustic resonance, ballast, high-intensity discharge lamp, metal halide lamp, white-noise modulation.

In this paper, a new active interphase reactor for twelve-pulse diode rectifiers is proposed. The proposed system draws near sinusoidal currents from the utility. In this scheme, a low kVA [0.02 [P.sub.o] (PU)] active current source injects a triangular current into an interphase reactor of a twelve-pulse diode rectifier. This modification results in near sinusoidal utility line currents with less than 1% THD. It is further shown that a low kVA, 12-pulse system with an autotransformer arrangement [kVA rating of 0.18 [P.sub.o] (PU)] can be implemented with the proposed active interphase reactor. The resulting system draws clean power from the utility and is suitable for powering larger kVA ac motor drive systems. Detailed analysis of the proposed scheme along with design equations is illustrated. Simulation results verify the concept. Experimental results are provided from a 208 V, 10 kVA rectifier system.

In this paper polyphase transformer arrangements with reduced kVA capacities are presented for harmonic current reduction in high power diode rectifier-type utility interface systems. Based on the concept of an autotransformer, a 12-pulse rectifier system is realized with a resultant transformer kVA rating of 0.18[P.sub.o] (pu). In this arrangement the 5, 7, 17, 19, etc. harmonics are absent from the utility input line current. In the second scheme an 18-pulse rectifier is realized with the kVA rating of 0.16[P.sub.o] (pu) and the 5, 7, 11, 13, etc. harmonics are canceled in the utility line currents. Analytical design equations are presented to facilitate the design of system components. Simulation results verify the proposed concept, and experimental results are provided from a 208 V, 10 kVA 12-pulse rectifier system. The advantage of employing the proposed system for utility interface of rectifier/PWM-inverter motor drive systems is also explained.

In this paper methods of design and application of integrated inductor-capacitor-transformer (LCT) are presented. A generalized modeling approach is also described. On the basis of this model and by using practical data, a CAD software is developed for LCT. Several integrated LC and LCT samples were designed, built, and tested. Finally, a resonant converter, using integrated LCT, was built and tested.

Recent surveys of 208/120 V three-phase four-wire electric systems, buildings, and industrial plants with computers and nonlinear loads show excessive currents in the neutral. These neutral currents are fundamentally third harmonic, and their presence is tied to wiring failures, elevating of neutral potentials, transformer overheating, etc. In response to these concerns, this paper proposes a new active power filter scheme to cancel neutral current harmonics. The proposed approach employs a star/delta transformer along with a two-switch PWM-controlled active filter. The closed loop control of the active power filter guarantees cancellation of neutral current harmonics under varying load conditions. The proposed system drastically improves the overall system performance and virtually eliminates transformer overheating due to harmonics. Experimental results from a prototype active power filter confirm the suitability of the proposed approach.

In this paper, a new approach to improve power factor and reduce harmonics generated by a three-phase diode rectifier type utility interface is proposed. The proposed approach is passive and consists of a novel interconnection of a star/delta transformer between the ac and dc sides of the diode rectifier topology. This novel interconnection, in combination with the 120 [degrees] conduction intervals of each diode, is shown to generate a circulating third harmonic current between the ac and dc side of the rectifier bridge. The circulating third harmonic current between the ac and dc side of the rectifier bridge. The circulating third harmonic current is then shown to drastically improve the performance of the diode rectifier type interface. The resulting input current is near sinusoidal in shape with significant reduction in line current harmonics. The proposed system can be viewed as a cost-effective retrofit to the existing diode rectifier utility interface applications. Analysis and design of the proposed approach are examined in per-unit quantities. A suitable design example illustrates the sizing of the necessary passive components. Selected results are verified experimentally on a laboratory prototype system.

Methods of integrating capacitive and inductive components into new compact devices are presented. Configurations for integrating various combinations of L-C networks are shown. A practical example of constructing an integrated L-C for a series resonant converter is evaluated both practically and experimentally.

A transformer performs many functions such as voltage transformation, isolation, and noise decoupling, and it is an indispensable component in electric power distribution systems. However, at low frequencies (60/50 Hz), it is a bulky and expensive component. In this paper, the concept of electronic transformers is further extended and explored for its suitability in power distribution systems. It should be noted that from the input/output behavior, the electronic transformer and the conventional transformer are identical. Possible topologies employing static converters connected on the primary and secondary sides are explored to realize high-frequency operation of the magnetic core. To assist the commutation process, a four-step switching has been developed which does not require the use of snubbers. Reduced size, losses, higher efficiency, and better voltage regulation are some of the advantages of this approach. A 10-kVA design example along with experiment results are discussed. It is shown that a transformer designed with a conventional grain-oriented silicon--steel core can process three times the power at 1-kHz operating frequency as compared to 60 Hz. The proposed method is scalable in voltage/current with the currently available insulated gate bipolar transistor (IGBT) devices connected in series without special snubbers. Index Terms--Electronic transformers, four-step switching, high-frequency switching.

This paper proposes a robust three-phase active power-factor-correction (PFC) and harmonic reduction scheme suitable for higher power applications. The proposed system is a unique combination of a low-kilovoltampere 12-pulse rectifier system with a single-phase boost PFC scheme to shape the input current to near sinusoidal waveshape. The voltampere rating of the active PFC converter is 0.05 pu and is not exposed to line transients under varying load conditions. The proposed system is suitable for utility interface of higher power rectifiers employed in power supplies and adjustable-speed drive systems which demand clean input power characteristics in the range of 1-500 kW. The proposed system is rugged and, in the event the active control were to fail, the system reverts to 12-pulse operation with fifth and seventh harmonic cancellation. Analysis and design of the system is examined in detail, and simulation and experimental results on a 10-kVA prototype are shown. Index Terms - Clean power, harmonic reduction, three-phase rectifier.

In this paper, an autoconnected electronic transformer (ACET) for 12- and 24-pulse rectifier systems is proposed. Considerable reduction in size and weight is achieved by operating the transformer core at a higher frequency. The rating of the autotransformer is a fraction of the output power. Utility line currents are multipulse in nature with the cancellation of several lower order harmonic currents. Furthermore, the magnetic components on the rectifier dc side are also exposed to higher frequency and can be reduced in size and weight. With an operating frequency of 990 Hz and utilizing conventional grain-oriented steel, a size reduction of 1/3 is achieved compared to a conventional 60-Hz design. Finer grades of steel or alternatives, such as amorphous material, would increase the performance advantage even further. Another unique feature of the proposed concept is that the switching frequency components are neutralized at the input side of the rectifier system. A second configuration using an open delta ACET is also presented. The proposed concept is suitable for higher power rectifier systems, which demand clean input power characteristics. This paper presents analysis, simulations, design example, and experimental results for a 208-V 10-kVA prototype system. Index Terms - Autoconnected transformer, electronic transformer, high-frequency conversion, multipulse rectifier.