Impact of phase-locked loop on system dynamics of a CCGT incorporated diverse source system employed with AC/DC interconnection

Nowadays, research on renewable generation penetration in a power system has facilitated the use of power electronics with improved grid-support functionalities. This article addresses the automatic generation control of a three-area interconnected system with combined cycle gas turbine and two thermal generating units in area1 and a wind and two thermal units in other areas. All areas are employed with delayed communication channels, and appropriate generation rate constraints and governor deadband are provided in thermal systems. A recent metaheuristic algorithm, namely stochastic fractal search (SFS), is applied for optimization of secondary controller gains and other system parameters. The performance of various two-degrees-of-freedom proportional-integral-derivative (2DOF PID) controller structures are compared with single-degree-of-freedom proportional-integral-derivative controllers, and results explore the superiority of 2DOF PID controllers. An attempt to explore the impact of AC/DC links considering delayed phase-locked loop (PLL) dynamics during coordination with diverse source interconnected AC systems is presented and discussed. Results clearly outline overshoots and settling time of frequency, tie-power, and temperature deviation increases owing to the inclusion of PLL. A detailed numerical analysis is presented to understand the system dynamic responses due to parametric changes in PLL function. However, with optimum parametric selection, the deviations and settling time decrease. Last, sensitivity analysis implies that SFS optimized controller parameters need not be reset for ±25% changes in loading condition; inertia constant; and ±10%, ±20%, and –25% changes in tie-power synchronizing co-efficient. But system responses deteriorate during +25% changes in the latter owing to very strong ties between the areas, which are not recommended.