Multi-rate Co-simulation Framework with Taylor-series-based Variable-step Solver for Grid-connected Power Converters*

Grid-connected converters (GPC) are playing an increasingly important role in distribution networks. Performing electromagnetic transient (EMT) simulations on power electronics and distribution networks can significantly improve the analysis accuracy. However, the existing simulation software struggles to handle distribution networks with a large number of power electronic switches, leading to unacceptable simulation times. To address this issue, a system-hierarchical multi-rate co-simulation framework is proposed. The system is hierarchically divided into different rate subsystems based on timescales, and solvers with different simulation rates are used to solve them separately. A Taylor-series-based variable-step solver is proposed for power electronic systems, and numerical compensation algorithms are designed for multi-rate interfaces to improve the system stability and accuracy. Compared with commercial software, the proposed framework increased the simulation speed by more than 200 times in the studied case, involving 576 switching devices and 14 bus distribution networks, while contributing less than 1% to the relative error.