Inverter Model Reconstruction from Terminal Measurements for Electromagnetic Transient Studies

Electromagnetic transient (EMT) inverter modeling for the study of converter/grid interactions is crucial for modern systems integrating distributed generation, electric vehicles, and microgrids. However, detailed inverter topologies are unavailable in many practical cases, precluding the implementation of analytical models. This paper presents a method for inverter model reconstruction from EMT terminal measurements. Previous use of the method - in conjunction with the numerical Laplace transform and two-port admittance modeling - successfully reconstructed wideband models of DC-DC converters and power transmission lines. An extension of the method to switched inverter modeling is described and evaluated here. A two-port model of an inverter is mathematically reconstructed using emulated EMT terminal measurements obtained from MATLAB/Simulink. The responses of reconstructed and simulated models to arbitrary voltage inputs under varying load conditions are compared to determine the accuracy of the estimated model. The results obtained indicate that the proposed method successfully reconstructs transient inverter models for both resistive and inductive loads.

I. Introduction

The world is experiencing an exponential growth in the use of electric vehicles [1] and demand for batteries and technology related to renewable energy. As the amount of energy generated from renewable sources continues to grow [2], their integration with existing power grids becomes increasingly important. Microgrids comprised of renewable energy sources are becoming increasingly popular as alternatives and complements to existing power grids [3]. Given the growth of electric vehicle systems, charging points, and multiple proprietary technologies [4], the ability to accurately model power converters has become imperative for their performance evaluation and analysis, as well as to study their interaction with other grid elements.