New trends and future directions in load frequency control and flexible power system: A comprehensive review

In recent years, the conventional power system is becoming a hybrid power system with increments in the interconnection of Renewable Energy (RE) sources, High Voltage Direct Current (HVDC), and Energy Storage (ES). At the same time, the power system network is also becoming more flexible in managing demand and supply variability. These factors posed a challenge in achieving frequency stability when there are abrupt changes in the power system such as load increment/decrement, loss of generators, and faults. Due to this, load frequency control (LFC) has shifted from traditional controllers to hybrid controllers and from traditional optimization methods to hybrid metaheuristic optimization to achieve better stability in hybrid power systems. This paper provides a comprehensive review of load frequency control (LFC) and power system flexibility. Other frequency stability mechanisms that support further LFC i.e. application of frequency nadir and rate of change of frequency (RoCoF), control in wind turbines, and demand response are also presented. This review also highlights the research gaps and potential future research direction of LFC for multi-area hybrid power systems.