Phasor analisys of Transformer Series Voltage Source Converter

This paper presents a phasor modeling of a Transformer Series Voltage Source Converter (TSVSC) for voltage control. It is shown that the voltage in the system can be controlled in a simple way. The VSC is connected in series with the secondary of the transformer of the system imposing a voltage, which has controlled magnitude and phase in quadrature with the current on it. The voltage control at the transformer terminals (secondary side) is done changing the VSC voltage magnitude for two conditions for its phase: +90° or -90° from line current. The analysis has shown that the Transformer Series VSC can control the voltage in an effective way as in the case of using a conventional STATCOM or can control the power flow as an SSSC. The operation as a voltage controller or a power flow controller depends on the relative size of the impedance in series with the TSVSC and the current phase. The system studied was implemented in the Matlab simulator.