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Abstract The real‐time simulation of active distribution networks (ADNs) can provide an accurate insight into transient behaviours, but faces challenges in simulation efficiency and flexibility brought by larger system scales and wider time‐scale ranges. This paper presents an asynchronous multi‐rate (AMR) method and design for the real‐time simulation of large‐scale ADNs. In the proposed method, the entire ADN was decoupled into different subsystems according to accuracy requirements, and optimized time‐steps were allocated to each subsystem to realize a fully distributed simulation. This not only alleviated the time‐step coordination problem existing in multi‐rate real‐time simulations, but also enhanced the flexible expansion capabilities of the real‐time simulator. To realize the AMR real‐time simulation, a multi‐rate interfacing method, synchronization mechanism, and data communication strategy are proposed in this paper, and their hardware design is also presented in detail. A modified IEEE 123‐node system with photovoltaics and wind turbine generators was simulated on a 3 field‐programmable gate arrays (FPGAs)‐based AMR real‐time simulator. The real‐time results were captured by the oscilloscope and verified with PSCAD/EMTDC, which demonstrated the superiority in simulation flexibility and accuracy compared with the synchronous multi‐rate (SMR) method.

Abstract Field‐programmable gate array (FPGA)‐based real‐time simulators are often applied in simulations of active distribution networks (ADNs) because of their parallel architectures and low cost. The overall performance of an FPGA‐based real‐time simulator is mainly determined by its kernel solver, which solves the nodal equation at each simulation time step. With the increasing scale of ADNs, real‐time simulations of fast switching dynamics, along with limited computation hardware, have increased the requirements of the solver in terms of both time and resource consumption. In this study, a highly parallel kernel solver is proposed to improve the simulation efficiency of the FPGA‐based real‐time simulator. The multi‐level parallel design and its implementation, including the parallelism at the system and module and element levels, are presented in detail. A modified IEEE 123‐node system with distributed photovoltaics (PVs) is then simulated using a three‐FPGA‐based real‐time simulator. Simulation results are compared with the commercial simulation tool PSCAD/EMTDC to validate the proposed kernel solver.