In this paper, we extend a previous study on a totally enclosed thermal model of a synchronous generator, with temperature state estimation using experimental data. The extension includes a new formulation of the system model, with four different model variations with and without temperature dependence in the metal, air, and water heat capacities and the copper resistances, where temperature variation in water and/or air requires a non-standard heat exchanger model. In the former study, the Unscented Kalman Filter (UKF) was used for state estimation. Here, we include both the UKF as well as the Ensemble Kalman Filter (EnKF) in the comparison. UKF and EnKF are compared based on estimation accuracy and computational speed. Results show that EnKF exhibits lower RMSE for the innovation process and thus is more accurate than the UKF even with a "minimum" of 50 particles, but the UKF with 6 sigma points (3 states) is faster. It is too early to conclude which of 4 models is more accurate, as they need to be tuned individually wrt. parameter fitting.

In a microgrid connected with both intermittent and dispatchable sources, intermittency caused by sources such as solar and wind power plants can be balanced by dispatching hydro power into the grid. Both intermittent generation and consumption are stochastic in nature, not known perfectly, and require future prediction. The stochastic generation and consumption will cause the grid frequency to drift away from a required range. To improve performance, operation should be optimized over some horizon, with the added problem that intermittent power varies randomly into the future. Optimal management of dynamic system over a future horizon with disturbances is often posed as a Model Predictive Control (MPC) problem. In this paper, we have employed an MPC scheme for generating a hydro-turbine valve signal for dispatching necessary hydro power to the intermittent grid and maintaining grid frequency. Parameter sensitivity analysis shows that grid frequency is mostly sensitive to the turbine valve signal. We have found that controller discretization time, grid frequency, and power injection into the grid are interrelated, and play an important role in maintaining the grid frequency within the thresholds. Results also indicate that the fluctuations in grid frequency are insignificant on the turbine valve position during power injection into the grid.

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