A Generic VFD-CLM Equivalent Model for Distribution Network With Multiple VFD Loads

In recent years, with the growing integration of variable frequency drives (VFDs) into the distribution network (DN), the dynamic characteristics of power loads have changed substantially. Typical DNs have hundreds of VFDs spread over a much larger area, it is impractical to represent each of the VFD explicitly. To find a reasonable representation that can reproduce the important behavior of different VFDs, a low-order generic model for different types of VFDs is developed. Then, we propose a new method for aggregating the generic VFD models, which provides detailed equivalence for the linear and nonlinear components and therefore has high accuracy. Finally, the aggregated VFD model is paralleled with the traditional composite load model (CLM), named variable frequency drives-composite load model (VFD-CLM), which is used to describe the overall dynamics of the DNs containing a high share of VFDs. Based on a practical DN with multiple types of VFDs, both the feasibility and applicability of the proposed VFD-CLM model are verified under different voltage dip faults. The proposed VFD model is low-order and generic, which can be easily implemented into the existing simulation platforms. In addition, the developed VFD-CLM model is much more accurate, which is beneficial for power system analysis and control.