The ability of the PWM converter schemes to operate as a linear amplifier, in both regenerative and rectifier applications, is an important issue. The PWM voltage converters are increasingly called upon to fulfill the duties of filtering, stabilization and dynamic performance enhancement. However, the straightforward power angle control (PWM pattern position) of the converter is characterized by a slow response and stability problems. This paper describes, analyzes and verifies a stand-alone, constant power factor, controlled unit converter. The proposed scheme employs a PWM voltage type converter and has important characteristic, that is, the operation with variable power angle and modulation index (PWM pattern weight). By realizing this property, the converter can provide sinusoidal input current with constant power factor (e.g. unity p.f.) and exhibits fast transients response. This paper presents a comprehensive approach to the quastion of the design criteria and closed form equations for PWM converter that demands sinusoidal current with constant unity power factor and at the same time provides high quality output d.c. current. The principles of operation along with the design criteria of the power circuit components are discussed in detail. Most features of teh converter are clearly interpreted for resistive and dynamic loads. On the basis of the given analysis, the paper provides the design guidelines for the PWM converter. Also, a novel control strategy is proposed, which allows to fulfill all the specifications; in particular zero reactive power demand and very low current ripples for rectifier and regenerative operations. The proposed method in this paper utilizes simultaneously the control variables: modulation index D and power angle delta. The instantaneous control for both achieves high-dynamic response, power factor adjustment capability and insensitiviness to parameter variations and disturbances. Also, the proposed scheme provides a low cost solution for d.c. and a.c. drive applications. This paper provides a complete analysis of the converter, interesting design criteria and equations, and design example. Finally, SPICE simulation and experimental time domain results are investigated.
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