Showing papers by "Luiz A. C. Lopes published in 1996"
TL;DR: In this article, a static phase-shifter based on a parallel connection of modules of a nonconventional PWM AC-AC converter is presented, where the average number of switches through which the current flows is small.
Abstract: This paper presents a static phase-shifter based on a parallel connection of modules of a nonconventional PWM AC-AC converter. Conduction losses are kept low by using only one active power conversion stage where the average number of switches through which the current flows is small. Filtering losses are also expected to be low because of the high order and small magnitude of the harmonics generated by switching. This is obtained by operating the modules with symmetrically phase shifted carriers to provide harmonic cancellation. Thus, even with the switches operating at low frequencies to keep the switching losses low, a high equivalent switching frequency is achieved. The performance of the phase-shifter for damping power oscillations in open loop is also evaluated.
12 citations
23 Jun 1996
TL;DR: In this paper, a variable reactance-type static VAr compensator (SVC) was proposed, which employs force-commutated switches as well as thyristors.
Abstract: This paper presents a variable reactance-type static VAr compensator (SVC) which employs force-commutated switches as well as thyristors. The proposed compensator employs thyristor switched capacitors (TSC) and a fixed capacitor bank to control, in steps, the amount of reactive power generated. Fine adjustment of the reactive power generated and also the reactive power absorbed by the SVC are obtained with N modules of a new four-switch (force-commutated) PWM controllable reactor. These are controlled with phase shifted carriers in order to achieve harmonic cancellation. The features of this multi-module PWM SVC are analyzed using switching functions and confirmed with simulation results.
8 citations
26 May 1996
TL;DR: In this article, the use of a practical force-commutated AC controller in PWM phase-shifters is discussed for a basic structure, which is then modified to allow implementation with the currently available GTOs.
Abstract: This paper discusses the use of a practical force-commutated AC controller in PWM phase-shifters. The operating principles are presented for a basic structure, which is then modified to allow implementation with the currently available GTOs. This high power version of the PWM phase-shifter employs a multi-module AC controller to attain the high voltage levels required for operation at transmission system levels. Moreover, the individual modules are controlled with phase shifted carriers in order to achieve harmonic cancellation. Low distortion waveforms are thus obtained with GTOs switching at low frequencies, resulting in reduced switching losses. A design procedure to calculate the required number of PWM AC controller modules so as to meet given harmonic constraints without filters is presented. The proposed concept is verified with EMTDC-based simulation results.