THE IMPACT OF A FUZZY SELF-TUNING PI CONTROLLER SUPPORTED BY STATCOM ON LCC-HVDC SYSTEM CONNECTED TO WEAK AC GRID IN BOTH SIDE

The AC/DC interaction between an HVDC system and the adjacent weak AC system is very sensitive to disturbances. For this reason, this paper presents an effective control system integrated in HVDC system, based on the use of different values of proportional and integral gains varied online by fuzzy self-tuning PI controller (FSTPIC) according to necessity, supported by a static synchronous compensator (STATCOM) to compensate the reactive power and achieve improved performance of the HVDC system. The fuzzy logic device has selfadaptive input gains to ensure normalization between -1 and +1 of the input signals. To evaluate the effectiveness of the proposed a control strategy, a comparison is made on four cases of CIGRÉ HVDC benchmark model, the first is conventional system (PI controller only), the second HVDC system with fuzzy Self-Tuning PI Controller, the third is HVDC system with the STATCOM only and finally HVDC system with fuzzy self-tuning PI controller and the STATCOM. This comparison is done for different types of defaults like the single-phase short circuit to ground and three-phase short circuit to ground inverter side of LCC-HVDC transmission link system