A fractional time‐step simulation method suitable for the associated discrete circuit model of power electronic system

Abstract

The associated discrete circuit (ADC) model for switches is widely used in electromagnetic transient simulation of power electronic system. When using ADC model, the problem of virtual power loss caused by L/C switching cannot be ignored and small time-step (≤2 μs) is usually required to guarantee accuracy, both of which will limit the application of ADC model. To cope with this, a fractional time-step simulation method (FTSSM) suitable for the ADC model of power electronic system is proposed. The method is derived from the compact form of electro-magnetic transient program (EMTP) algorithm, and the simulation iteration is implemented by small-step synthesis calculation with different fractional time-steps, which are designed to locate the accurate switching actions. In this way, the simulation can be conducted under larger time-step (to tens of μs) while the accuracy is still acceptable. Further analysis on time domain error and numerical stability of the FTSSM are discussed. Simulations of grid-connected inverter system and permanent magnet synchronous motor (PMSM) driving system are done, using FTSSM and on PSCAD respectively for comparison. The results verify the accuracy of proposed FTSSM, and indicate that the FTSSM is helpful to accelerate the offline simulation and improve the real-time simulation performance.