Sampled-data based discrete and fast load frequency control for power systems with wind power

Load frequency control employs communication networks to transmit measurements and control signals. The controller is usually designed in continuous-mode and discretized in implementation with a large sampling period, which may result in a degraded dynamic performance or even cause system instability. On the other hand, high penetration of wind power reduces the inertia of the power system, leading to a faster frequency response and larger frequency deviation after a contingency, and desires a fast load frequency control. Therefore, this paper presents a discrete-mode load frequency control scheme considering a large sampling period of control/measurement signals via sampled-data control, and introduces an exponential decay rate as a new performance index to guide a design of load frequency control scheme with desired faster frequency response. The proposed scheme is evaluated on a one-area power system, a traditional two-area power system with wind power and a deregulated three-area power system with wind power. Using the proposed scheme and the state-of-the-art schemes, the frequency response performance and the tolerance to sampling period of power systems are analyzed. The results demonstrate that the proposed control scheme can ensure the stable operation of the system under a larger sampling period so as to reduce the communication network burden. Also, the results show that the controller designed by a large exponential decay rate can provide a fast frequency response to alleviate the impact of the system's frequency response due to the high penetration of wind power.