Uma contribuição ao estudo dos conversores comutados a capacitores (CCC)

Abstract

The aim of this thesis is to present the option of application of the capacitor commutated converter CCC in HVDC transmission systems, which present same advantages comparatively with the conventional HVDC systems that don’t use the series compensation employing capacitors in the converter alternating current, AC side. The capacitors propitiate the supply of reactive power to the converter and also are favorable to minimize the inverter commutation failures due to the increasing of the commutation margin and also due to the voltage compensation, when a system voltage drop occurs. These aspects result favorable with respect to the increasing of the stability of the system which uses this proposed arrangement of series compensation system, using capacitors. Experimental relevant current and voltage waveforms for the six pulse conventional converter was obtained for the comparison with the results obtained when the case of using the CCC converter. Simulated results are also presented for the 12 pulse converter, which is obtained by associating in series two six pulse ones. Digital simulation programs have also been developed for obtaining the relevant conventional and CCC converter waveforms, as well as for obtaining the iterative calculation of the commutation angle. On this way a comparison of simulated and experimental results will be possible for validation of the developed digital programs for obtaining the relevant converter current and voltage waveforms and also for the calculation of the commutation angle. The main advantages and disadvantages of the CCC HVDC systems, compared with the conventional ones, are presented.