Abstract:
Existing energy management problems for a multi-microgrid (MMG) system only minimise the operational cost. This study proposes a multi-objective operational cost and emissions minimisation (OCEM) problem for a grid-tied MMG system. The energy management strategy provided by the OCEM problem takes into account the power sharing among all the microgrids (MGs) as well as a price-based demand response programme. The benefits of the OCEM problem are demonstrated by comparing its results with those of a single-objective operational cost minimisation (OCM) problem reported in the literature. These results are obtained by applying both problems to the same MMG case study, which consists of three interconnected MGs and solving these two optimisation problems with a hybrid optimisation algorithm between the genetic algorithm and sequential quadratic programming in MATLAB. When compared to the best solution provided by the OCM problem, the optimal trade-off solution (OTS) provided by the OCEM problem decreases the emissions by 73.07% with a 18.86% increase in the operational cost. The OCEM problem does provide a decision maker with the flexibility to choose the best solution according to the trade-off between the emissions and operational costs, which are competing objectives.
The OTS provided by the OCEM problem has several advantages in comparison to the best solution provided by the OCM problem, namely:
1. Increase in the utilisation of the distributed energy resources in particular, the energy generated by the micro-turbines increased by 80.94%.
2. The energy imported from and exported to the main grid decreased by 52.52% and increased by 7.64%, respectively. As a result, the net energy imported from the main grid is negative, which contributes towards emission reduction and main grid support in terms of energy generation.
3. Reduction in the maximum demand of the MMG system from the main grid as the maximum power flow from the main grid to the MMG system decreased by 32.31%.
The MMG case study demonstrates the capability of the OCEM problem in designing an energy management strategy, which is cost-effective and minimises the emissions.
