Conversores estáticos CA-CC-CA obtidos a partir da conexão de módulos monofásicos.

Abstract

Static converters are a valuable tool when seeking to improve the power quality of power systems. This work presents conventional and proposed converters, all composed by AC-DC-AC modules with four and/or three legs without isolation transformer. We studied two types of converters: five single-phase converters, derived from series connection of AC-DC-AC moduleswith three and / or four legs, and one three-phase converter obtained from AC-DC-AC modules with three legs. The following aspects are discussed for each topology: (i) dynamic modelling; (ii) PWMstrategy; (iii) control of several variables of the system, i.e., input grid current (waveform and power factor), DC-link voltage, load voltage and low frequency of the circulating current (when it exist); (iv) characterization of the converters based on harmonic distortion of voltages and currents, losses of the DC-link capacitors, and conduction and switching losses of the semiconductor switches. The series connection is advantageous because it allows the reduction of the DC-link voltage, the harmonics generated by the converters, witch reduce the rating of the semiconductors witches. All proposed single-phase converters were derived from serial connection. The converters are suitable for applications that operate with the same frequency in the input and output (e.g., uninterruptible power supply (UPS), voltage regulated sources, harmonic compensators, etc). In order to validate the results, curves of simulation and experimental are presented.