Enhanced load frequency control using predictive reduced order generalized active disturbance rejection control under communication delay and cyber-attack

Abstract

Load frequency control (LFC) is necessary to maintain the power system frequency and tie line power to its nominal value. In modern power system, importance of LFC is increased due to inevitable use of communication channel, intermittent nature of renewable sources, computer-based control strategies, model uncertainties and cyber-attack. An effective LFC is required to mitigate various uncertainties and disturbances including the delay for which active disturbance rejection control (ADRC) control schemes have been explored in this work. An ADRC consists of an extended state observer and a state feedback controller. In the present work, predictive structure like Smith predictor has been proposed for different variants of ADRCs. Additionally, a new variant of ADRC, namely, reduced order generalized active disturbance rejection control (RGADRC) has been proposed along with the predictive structure. These controllers are designed considering system uncertainties and with or without non-minimum phase. To show the efficacy of the proposed schemes examples of single-area non-reheat, reheat, and two-area thermal and photovoltaic-wind micro-grid system are demonstrated. The robustness of the proposed approach is examined while taking system parameter variation, random fluctuation of solar power (0–0.001 p.u.), wind power (0–0.0012 p.u.), and load disturbance (0–0.01 p.u.), and cyber-attack (2 p.u.). The predictive RGADRC shows superior performances compared with other predictive ADRCs as well as some methods prevalent in the literature for LFC systems with nonlinearities like generation rate constraint of 0.1 p.u./min, governor dead band of 0.05%, and communication delay of 2.28 s. The predictive RGADRC maintains stability of the LFC system with satisfactory transient for + 50% change in gain and time constant of the generator and load, along with random fluctuations as mentioned above.