Proposta de retificadores híbridos com suportabilidade a afundamentos de tensão utilizando técnica de compensação série de tensão no barramento CC

Abstract

This work presents the analysis and experimental development of a topological structure of hybrid rectifier able to maintain a regulated output DC link for the occurrence of balanced and unbalanced voltage sags in the AC mains supply. Moreover, under normal conditions of the supply voltage, the structure operates draining currents with low harmonic content and high power factor. It is noteworthy that these operational characteristics are achieved with the switched converters that comprises the structure processing only a portion of total power output, making the most efficient and robust set. The new topology is denominated Three Phase Hybrid Rectifier with Series Compensation DC Bus and has as main characteristic an innovative voltage regulation technique based on insertion of a DC-DC converter with output capacitor connected in series with the capacitor available in the DC bus of the main converter. This additional converter is responsible for regulating the DC link voltage according to a specific reference value, operating only in the voltage sag condition and processing only a portion of the total output power drained by the load in this operating condition. To analyze the behavior of the proposed topology has been implemented in a computer model PSIM® platform, it was possible to verify the efficiency of the control strategy for sinusoidal current imposition based on the real-time calculation of DHTI during normal conditions of supply voltage. In addition, It was evaluated the behavior of the structure regulating the DC link voltage on the occurrence of voltage sags. In order to corroborate the exposed theory a 5 kW prototype was constructed and evaluated in the laboratory. This was tested in the regular voltage supply condition and during the occurrence of sag conditions types A, B, C, D, E, F and G. It was observed that in normal conditions the proposed solution is effective in mitigating harmonic content of the AC input current. During the occurrence of voltage sags the output DC link was set at the preset value in the control strategy. In both cases the switched converters processed only a fraction of the total power output, which makes the structure very attractive for applications with high power levels.