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UBC Theses and Dissertations

Methods for improving the optimal operation control of combustion engine-based micro-CHP systems in small residences Robertson, Brandon


The research presented in this thesis contributes to the body of literature surrounding the optimal operation of micro-CHP (combined heat and power) systems particularly within small residences. A method is discussed that allows for the use of more complicated constraints and increased resolution compared to standard model predictive control (MPC) strategies. This method uses two progressively more detailed optimizations where the first optimization applying boundary constraints to the second optimizations. Such a technique results in more freedom in the choice of constraints and resolution for the MPC optimization. This method is tested with micro-CHP formulations containing solar power, an auxiliary heater, thermal energy storage (TES), and electrical energy storage (EES). Many variants of the proposed method and formulations are tested using a novel HLM for comparison. Computational complexity resulting from the proposed method and the formulation are discussed. The effects of forecasting inaccuracies and the selling price of electricity are investigated for the proposed formulations. The time-step size and horizon length of the optimization are changed, and the effects of these changes are explored. The behavior of the controller is also discussed in relation to a heat-led method (HLM). The proposed methods can be generalized to problems with different constraints resulting in a transferable solution to similar problems. The methods are also tested using low-performance hardware and open-source software to be generalizable and competitive in cost to conventional methods. The proposed formulations and MPC strategies were able to outperform an HLM in the majority of test scenario, particularly when the selling price of electricity is lower than the purchasing price. However, when the selling and purchasing price of electricity are the same, the performance of the proposed MPC strategy is much closer to that of the HLM with no guarantee of better performance with the current formulation. The formulation was also able to deal with relatively complex constraints while achieving sufficiently low computation times.

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