Design of sampled data and event-triggered load frequency controller for isolated hybrid power system

Abstract

Load frequency control is quite important for power system having wind generation, as wind speed is intermittent. Discrete controllers, implemented with high sampling rate, consume more network bandwidth. Hence, this paper presents discrete frequency regulation schemes for isolated hybrid power system containing wind, diesel and battery storage with a focus on minimizing the utilization of network resources. Two methods for utilizing the network resources more efficiently are given and applied on the hybrid wind-diesel-battery power system. In first, the periodic sampling is implemented, sampling time of states measured and sent through network for stabilizing the system is maximized. Secondly, an event based sampling is performed to further reduce the communication burden. Along with the sampling time, time delay introduced by network is also considered and maximum allowable delay bound is obtained in both the methods. The results show that channel bandwidth utilization can be reduced by increasing the sampling time while keeping the system stable. The event-triggered controller implemented can further reduce the required bandwidth. The robustness of the designed controller is verified for the above hybrid power system for different load disturbances, change in wind power, parameter variations and through eigenvalue sensitivity analysis. Finally, the approach is extended to interconnected two-area hybrid power system.