Multi-timescale Hierarchical Scheduling of an Integrated Energy System Considering System Inertia

The multi-energy complementary property enables an integrated energy system with great potential to consume more renewable energy efficiently. However, due to the system complexity, its coordinated scheduling remains a challenge. Inertia of key inertial components must be carefully described to avoid overestimating or underestimating system flexibility, and coordinated system scheduling should be executed on multiple timescales. This paper aims to achieve coordinated scheduling of an integrated energy system, and improve its flexibility description accuracy by considering the inertia of the heat network, the combined heat and power (CHP) unit, and other key inertial components in the proposed multi-timescale scheduling method. Specifically, heat network inertia is considered to explore its heat storage ability and enlarge the operation range of an integrated energy system. To avoid overestimating CHP unit flexibility, the CHP unit ramp process is described to identify gaps between power supply and demand caused by CHP unit inertia. Besides, different temporal resolutions for inertia description are selected to match component features, whilst multiple scheduling periods are chosen to fit component regulation rates. Optimization results show that, by utilizing heat network inertia for heat storage, the daily cost and renewable energy curtailment can be reduced by 3 and 20%. Neglecting CHP unit inertia would underestimate the power output of flexible units, and the daily cost would be underestimated by 0.9%. Additionally, the proposed method can coordinate the system to handle the fluctuation and randomness of renewable energy, reducing the daily cost by 4%.