Semi-implicit Delay Decoupling Method for Efficient Processing of Switching Actions

Traditional electromagnetic transient simulations typically rely on detailed models of voltage source converters and employ the double interpolation method (DIM) to manage switching events within a time step. However, the complexity of the DIM algorithm and the time-varying conductor array in detailed models significantly hinder computational efficiency in large grid simulations. To address this, we apply a semi-implicit delay decoupling principle to model the VSC, proposing to replace DIM by equating the duty cycle of the switching function within a time step. First, we derive the decoupling model of the VSC from its state equation, enabling parallel computation of the converter and enhancing computational efficiency. Next, we analyze the mechanisms that lead to accumulated errors when switching events are not processed, providing the computational time scale and the calculation of the equivalent duty cycle to ensure simulation accuracy. Finally, we validate the accuracy and effectiveness of our method through comparison with PSCAD benchmark simulation waveforms and discuss the methodological advantages of our approach.