Optimal Power Flow Scheduling Strategy for Multi-Microgrids with Multi-Time Scale Method

This paper proposes an optimal power flow scheduling strategy for the energy management of multi-MG systems. At the multi-MG level, the global central controller (GCC) is responsible for managing the MGs. The GCC calculates the amount of power exchanged within the MGs by using a novel optimal energy allocation policy. Based on the energy supply and demand mismatch, MGs are classified as providers and consumers. The GCC collects information, then distributes energy among the consumers and divides benefits to the providers. Each consumer determines the price of the purchased energy from other MGs based on a priority parameter, in which the local load demand and renewable energy penetration rate are considered as important factors. At the MG level, with the goal of minimizing the operating cost of the MG, the energy is controlled from two time scales, namely day-ahead and intraday, to optimize the output power of generators and energy storage devices. Finally, a simulation of a multi-MG system with three MGs demonstrate the effectiveness of the proposed optimal method.

I. Introduction

As the energy demand and environmental issues increase worldwide, a large amount of renewable energy is flooding into the electricity market. To meet the challenges brought by the random and intermittent renewable energy generations (RGs) to the main grid, multi-microgrids (MGs) emerge as one of the promising solutions to integrate the REGs effectively [1 – 6]. MGs usually consist of distributed generations, loads, energy storage systems, etc. They can solve the connection problem between the RGs and the main grid by integrating coordinated control and energy management systems [7]. Generally, a single MG has a limited capability to maintain a stable and economic operation, while a combination of MGs, i.e. a multi-MG system, guarantees an improved ability. Compared with a single MG, multi-MG systems can ensure normal operation of the internal single MGs and can simultaneously balance the energy flows among the MGs in the system to improve the power quality and reliability, and reduce the distribution power losses [8 – 12]. Therefore, the coordinated operation control of multi-MGs is essential to realize an autonomous operation of the system.