This article addresses the problem of estimating the state of a multimachine power system (MPS). To work with power networks with lossy transmission lines, a variation of the classical third-order MPS is proposed by considering generators’ electrical power injected into the grid as a state variable. Based on a linear decentralized estimation model (tailored for a specific purpose), the state variables of generators (load angle, relative speed, and electrical power) together with terminal voltage magnitudes are estimated in a decentralized fashion through two new robustly convergent linear Luenberger estimators, one based on load angle measurement and the other based on relative speed measurement. The new MPS estimation model includes a set of robustly quick observable states, one per machine, which allows capturing the interaction with other generators, transmission line losses, unknown disturbances, and model errors. The result is a design superior to other related estimation techniques such as the extended Kalman filter (EKF) or Sliding Modes Perturbation Observer (SMPO) in terms of (i) a conventional-like simple pole placement-based tuning, (ii) low online computational load and disturbance rejection capability, and (iii) small gain-based convergence assessment. The performance of the proposed state estimation scheme is illustrated in a 3-machine power system under different operational conditions.
The Islanded Microgrids (IMGs) arise as a solution to the integral expansion of Electric Power Systems (EPS). The IMGs can be considered as islanded subsystems that usually include renewable energy sources (RESs) in order to satisfy the consumers' demand. The inclusion of these sources is reflected in grid frequency and voltage variations, particularly, due to their intermittent nature, which depends, among other conditions, on weather changes. To mitigate the intermittence effects associated with the generation, in the present study, a backup based on an Energy Storage System (ESS) is evaluated, and it shows that quality, reliability and security of an isolated power grid are improved. Numerical evaluation, based in a three-buses IMG benchmark, is done and it corroborates the teoretical results.
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