Abstract
Voltage unbalance in a three-phase system introduces oscillations to the DC Link voltage and power. Moreover, it causes performance deterioration of a pulsewidth modulation (PWM) of the back-to back voltage source converter systems (BTB-VSC) by producing the double-line-frequency ripples in the dc link voltage and power. This paper proposes a new control strategy by developing the conventional vector current controller relying on the DC and AC components of voltages and currents. The proposed controller utilized for the three-level voltage-source converters as a building block of the Convertible Static Transmission controller (CSTC) system in shunt-shunt mode. The proposed control strategy aims to suppress the oscillations in DC Link voltage and converters power under system disturbances and faults. The simulation tests is realized by PSCAD-EMTDC environment software. The simulation result shows the feasibility of the proposed controller under normal and unbalanced AC conditions with the CSTC application system.