• Energy Research

Steady-state energy flow calculation (EFC) is the cornerstone of the long-term operation assessment of integrated energy systems (IES). The conventional EFC methods mainly focus on calculation speed and efficiency. However, the robustness is often ignored, which may result in a failure in finding the solutions under ill-conditioned and unsolvable situations. To address this issue, this paper proposes a robust EFC method for integrated electricity-gas-heat system. First, a novel robust EFC method based on Levenberg–Marquardt (L–M) method is proposed for a comprehensive formulation of the energy flow model combining the electricity, natural gas, district heating system and detailed interdependence. Further, a consecutive adaptive damping factor updating approach is proposed. It enables a secure search step to avoid the flutter in iteration process, thus enhancing computational efficiency and convergence for EFC. In addition, the influence of the direction and the size of search step are jointly considered. It is helpful to guarantee solutions for both ill-conditioned and unsolvable situations. Numerical simulation results demonstrate the strong robustness, convergence and universality of the proposed EFC method that works under diversified operation modes, e.g., well-conditioned mode, inappropriate initial values, heavy load mode, and ill-conditioned operation mode.