Self-commutated SVC with compensation of harmonic and negative-phase-sequence currents using digital control system

To improve the operating ability of future transmission systems and to prevent the inflow of harmonic currents and negative-phase-sequence current, the authors have developed a self-commutated static VAr compensator (SVC) with a digital control. For the control system to realize superior accuracy, high performance functions and easy maintenance, a direct digital control system (DDC system) is used. The DDC system is composed of multiple CPUs and DSPs. In a preliminary verification before installing the proposed SVC in the power system, the authors verified the compensating function of the proposed SVC with a mini-model and an analog-simulator. The results of the tests and simulations with the mini-model and the analog-simulator confirmed that the proposed SVC could sufficiently compensate for voltage fluctuation and the inflow of harmonic currents and negative-phase-sequence current. Therefore, the effectiveness of compensation with the DDC system was confirmed.