DSP based control of high power static VAr compensator using novel vector product phase locked loop

This paper presents a new dual loop control using novel vector product phase locked loop (VP-PLL) for a high power static VAr compensator (SVC) with three-level GTO voltage source inverter (VSl). Through circuit DQ-transformation method, a simple DQ-axis equivalent circuit is obtained. From this, DC analysis is carried out to obtain maximum controllable phase angle α_max per unit current between the three phase source and the switching function of the inverter, and AC open-loop transfer function is given. Because α _max becomes small in high power SVC, this paper proposes VP-PLL for more accurate a control. As a result, the overall control loop has dual loop structure, which consists of inner VP-PLL for synchronizing the phase angle with source and outer Q-loop for compensating reactive power of load. Finally, the validity of the proposed control method is verified through the experimental results