Multi-time-scale energy management of renewable microgrids considering grid-friendly interaction

Low-carbon operation of renewable microgrids (MGs) is challenging because of the large share of distributed renewable energy sources (RESs) and increasingly complex loads. Therefore, a favorable energy management system (EMS) should be developed. In this paper, in order to promote the grid-friendly and economic interaction with the main grid, an improved multi-time-scale EMS is proposed for the renewable MGs composed of distributed RESs, battery energy storage (BES) units and flexible loads. Firstly, flexible resources, such as BES units and flexible loads, are integrated to deeply participate in the low-carbon operation of renewable MGs. A dynamic and precise operating reserve scheme based on the probabilistic interval is formulated to ensure that BES units can operate in a coordinated manner between economic scheduling and operating reserve. Then, the demand respond based on the expected kilowatt-hour power curve variance and power fluctuation cost model is constructed for jointly regulating the distribution of the tie-line power. Last, the improved multi-time-scale EMS consists of day-ahead scheduling plan and intraday rolling correction. The intraday rolling scale with a varying rolling window performs optimal rescheduling for remaining periods. The deviation between the day-ahead scheduling plan and actual operation is corrected in real time. Simulations on a park-scale MG revealed the effectiveness of the proposed multi-time-scale EMS. In particular, when the fluctuation coefficient was set to 0.1, compared with the existing day-ahead scheduling plan scenario, the peak-to-valley difference in the proposed method decreased by 62.262%, and this method requires a 2.072% increase in the grid energy cost. Moreover, in terms of actual operation results of two EMS cases, the total operating cost reduction in the proposed multi-time-scale EMS is 2.474% compared with the single-time-scale EMS case. The proposed multi-time-scale EMS case has superior fluctuation metrics, which shows that the interactive operation of in the proposed multi-time-scale EMS is more grid-friendly.