۱- Introduction

۲- Preliminaries

۳- DC microgrid model

۴- Battery scheduling by optimization-based control

۵- Simulation results

۶- Comparison with other models and control strategies

۷- Conclusion

References

Abstract

This paper considers a discrete-time scheduling method for the power balancing of a continuous-time DC microgrid system. A high-order dynamics and a resistor network are used for modelling the electrical storage unit and the DC bus of the centralized microgrid system, respectively. A PH (Port-Hamiltonian) formulation on graphs is employed to explicitly describe the microgrid topology. This modelling approach allows us to derive a discrete-time model which preserves the power and energy balance of the physical system. Next, a constrained economic MPC (Model Predictive Control) using the proposed control model is formulated for efficiently managing the microgrid operation. The systematic combination of the network modelling method and optimization-based control allows us to generate the appropriate power profiles. Finally, the benefits of the proposed approach are validated through simulation and comparison results over a particular DC microgrid elevator system under different scenarios and using real numerical data.

Introduction

Nowadays, industrial and research communities are concentrating their attention to microgrid systems and their development for improving the energy reliability of the classical power grid. A microgrid is represented by a group of interconnected customer loads and Distributed Energy Resources (DER) within clearly defined electrical boundaries which acts as a single controllable entity that can connect and disconnect from the grid (known as “islanding”) [۱]. DERs are small power sources that can be aggregated to provide the power necessary to meet (part of) a regular demand. It includes the distributed energy storage and generation systems. The distributed energy generation systems are integrated to the local system to reduce the impact on the environment of the fossil fuel resources. However, the electricity price of the external grid varies during a day. It may be expensive when the energy demand is high. Moreover, the power supplied by the distributed energy generation system is unstable [2,3]. Consequently, the distributed energy storage system is used to store energy when it is available and cheap. Then, it is reused in the contrary case. In microgrids, DERs are connected to the load systems through converters to satisfy the energy demand [4,5].