Formulation of Stochastic MPC to Balance Intermittent Solar Power with Hydro Power in Microgrid

Abstract

In a microgrid with both intermittent and dispatchable generation, the intermittency caused by sources such as solar power and wind power can be balanced using dispatchable sources like hydro power. Both generation and consumption are stochastic in nature and require future prediction. The stochasticity of both generation and consumption will drift the grid frequency. Improved performance of the grid can be achieved if the operation of the microgrid is optimized over some horizon, for instance formulating Model Predictive Control (MPC), with the added problem that intermittent sources vary randomly into the future. In this paper, first, we have formulated a deterministic MPC and compared it with a PI controller. Second, a stochastic MPC (SMPC) based on a multiobjective optimization (MOO) scheme is presented. Results from deterministic MPC show that the overall performance of MPC is better than the PI controller for dispatching the required amount of hydro power into the grid and simultaneously constraining the grid frequency. Results from SMPC indicate that there exists a trade-off between the amount of water flow through the turbine and the rate of change of the turbine’s valve while constraining the grid frequency.