This paper presents an universal active filter for harmonic and reactive power compensation for singlephase systems applications. The proposed system is a combination of parallel and series active filters without transformer. It is suitable for applications where size and weight are critical factors. The model of the system is derived and it is shown that the circulating current observed in the proposed active filter is an important quantity that must be controlled. A complete control system, including pulse-width modulation (PWM) techniques, is developed. Comparisons between the structures are made from weighted total harmonic distortion (WTHD). Steadystate analysis are also presented in order to demonstrate the possibility to obtain an optimum voltage angle reducing the current amplitude of both series and parallel converters and, consequently, the total losses of the system. Simulated and experimental results validate the theoretical considerations.

This paper presents an universal active power filter for harmonic and reactive power compensation with UPS (Uninterrupted Power Supplies) features. The configurations does not use transformer in the series part. Transformerless modern UPS systems have been rapidly replacing the old technology due to their performance and size attributes. Reducing the numbers of passive elements and/or switches in active power filters and UPS topologies not only reduces the cost of the whole system but also provides some advantages, such as great compactness, smaller weight, and higher reliability. However, the cost reduction requires the use of more complex control strategies. The model of the proposed system is derived and it is observed that the system can be reconfigurable to operate with four or three-leg depending on the issue. A complete control system, including the PWM (Pulse-Width Modulation) techniques, is developed and a comparison between the proposed filter and the standard one is done, as well. Simulated and experimental results validate the theoretical considerations.Keywords -universal active power filter, single-phase structure, uninterrupted power supplies and P W M techniques. 0885-8993 (c)

This paper proposes a speed sensorless control for PMSM motor drive system. The sensorless strategy is based on back-emf estimation of the motor, suited for applications at high speed. The drive system uses a four-switches three-phase inverter. This topology is attractive specially in fault conditions in one leg of the conventional three-phase converter. The speed sensorless vector control based on the proposed converter provides a motor drive system with reduction of cost and volume. Relevant characteristics of the converter is presented, such as: voltage capability, capacitor currents, PWM modulation. Details of the vector control implemented is addressed. Simulation results are shown and validates the proposed system. The proposed method are under implementation in an industrial converter.

In this paper we propose two three-phase series active power filters (SAPF) for voltage harmonic compensation and voltage regulation. The power filters are conceived to operate without isolation transformer and auxiliary active dc source. The topologies are adequate for applications in which the load or grid terminals are accessible. The model of the systems are derived to analyze their behavior for general grid voltages and load conditions. Such analysis shows that it is possible to operate with a load active voltage amplitude regulated at the rated reference value for some grid voltages and load conditions. Based on the system analysis, a control strategy is proposed to adequately control the system. Experimental results for the system operating with very distorted input grid voltages are presented.

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