An Adaptive Tuning Mechanism for Phase-Locked Loop Algorithms for Faster Time Performance of Interconnected Renewable Energy Sources

Interconnected renewable energy sources (RES) require fast and accurate fault ride through (FRT) operation, in order to support the power grid, when faults occur. This paper proposes an adaptive phase-locked loop (adaptive d alpha beta PLL) algorithm, which can be used for a faster and more accurate response of the grid-side converter (GSC) control of a RES, particularly under FRT operation. The adaptive d alpha beta PLL is based on modifying the tuning parameters of the d alpha beta PLL, according to the type and voltage characteristics of the grid fault, with the purpose of accelerating the performance of the PLL algorithm. The proposed adaptive tuning mechanism adjusts the PLL parameters in real time, according to the proposed fault classification unit, in order to accelerate the synchronization performance. The beneficial effect of the proposed adaptive tuning mechanism on the performance of d alpha beta PLL is verified through simulation and experimental results. Furthermore, the benefits of using a faster synchronization method on the control of the GSC of RES are also demonstrated in this paper. Additionally, a new synchronization technique named frequency-phase decoupling (FPD)-d alpha beta PLL is presented, which applies an FPD technique from the literature in the structure of d alpha beta PLL, with the purpose of improving the performance of d alpha beta PLL. Finally, the adaptive tuning mechanism proposed in this paper is combined with the FPD-d alpha beta PLL in order to introduce the adaptive FPD-d alpha beta PLL, which presents an even faster time performance and is an ideal solution for the synchronization of RES under grid faults.