This paper proposes an analytical method for simulation of the steady and transient response of the HVDC system in order to simulate the electromagnetic process of HVDC system in the simulation of hybrid AC/DC system. First, the boundaries of AC and DC systems as well as some assumptions are introduced. Then, the HVDC system is considered as a combination of primary equipment sub-systems (PES) and control sub-systems (CS). According to the assumptions, the PES can be represented by different

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... ogeneous linear differential equations within different time intervals that are determined by the status of converters. These equations can be solved in analytical method. The CS is expressed by nonlinear differential and algebraic equations and simulated in numerical integration method. The interface parameters of each module are also introduced. The accuracy and efficiency of the proposed model are verified by comparing the simulation results computed by the proposed model with that simulated in PSCAD. INDEX TERMS AC/DC hybrid system simulation, HVDC, electromagnetic transient process, commutation failure.