Stability Improvement of Multimachine System Using Back-To-Back Converters

Abstract

As the penetration level of inverter-based generators continues to increase, it becomes crucial to reduce power oscillations between inverters and synchronous generators (SG) to improve system stability. This paper uses a multimachine system as the research platform and proposes a grid separation method employing a multi-terminal back-to-back converter. The converter is designed to be placed at the point of common coupling (PCC) in the original multimachine system and can divide the original grid into multiple microgrid regions while retaining the ability to transmit power between different regions. Each microgrid or region contains a self-regulated power source such as grid-forming (GFM) inverter or synchronous generator, which controls key power characteristics such as frequency and voltage within its region. The back-to-back converter facilitates power transmission between different regions. The AC-DC-AC conversion process ensures isolation and simplification of control over each microgrid’s power characteristics. The performance of inverters with different control strategies in each microgrid has been investigated, and the characteristics of various inverters are compared and demonstrated. Additionally, it was found that the battery storage requirements in each inverter-based microgrid are reduced using this method. The results are verified through MATLAB/SIMULINK simulations.