A Simplified Model and Parameterization Method for Variable Frequency Drive Loads in Phasor-Level Power System Studies

The proportion of variable frequency drives (VFDs) is increasing in power loads, gradually replacing conventional motors. While extensive research has been conducted on VFDs in electromagnetic timescale, there is a lack of VFD model in electromechanical timescale, posing challenges to large-scale power system simulation. Addressing this issue, the paper focuses on a simplified VFD modeling method in phasor-level. A unified reduced-order model is proposed to represent the electromechanical behavior of heterogeneous VFDs with diverse architectures. Further, a component-based method is designed to determine the model parameters for any given VFD. The dominant parameters associated with fundamental-frequency dynamics are derived analytically using energy-based principles, while the influence of higher-frequency effects is approximated through nonlinear fitting techniques. Results of this paper are verified through laboratory tests on real electrical appliances equipped with VFDs.