Harmonic Impedance Analysis of a Grid-Connected Converter System with Various Control Methods

Abstract:
The increasing number of power electronic devices in modern grids leads to increasing harmonic disturbances. In order to measure and analyze the harmonic behavior of a grid-connected converter system, this paper proposes the measurement of the harmonic impedance in electromagnetic transient (EMT) simulations. This approach is furthermore used to analyze and compare the behavior of different control methods on a Modular Multilevel Converter (MMC) Static Compensator (STATCOM). A measurement delay is considered in the EMT model, which is typical for a real converter control system, and its influence on the harmonic stability is shown by adjusting the delay time. Based on the results, the advantages of a grid-voltage-forming control and the specific disadvantages of a grid-supporting control regarding the harmonic behavior are discussed.