Influence of Rotor Side Converter on Electromagnetic Vibration in Asynchronous Hydrogenerator

The usage of multilevel voltage source converters (VSCs) for high-power applications is becoming more common as the field of power electronic converters continues to expand and progress. In the first generation, cycloconverters were employed for ac excitation in rotor circuits with high rating doubly fed induction machine (DFIM). Two-level and, more recently, three-level VSCs are utilized for ac excitation of DFIM since the introduction of VSCs. There are many decisive factors such as cost, reliability, device count, and power level for choosing converter configuration. This article presents a new factor (electromagnetic vibration (EMV) in stator) to be considered while choosing a converter configuration for DFIM rotor circuit. The impact of rotor side converter architecture on DFIM stator EMV is investigated in this article. In the rotor excitation circuit, two-level VSC and three-level converter are employed with a carrier frequency of 1 kHz. In both situations, the air-gap flux density is studied using a finite element analysis. The Maxwell stress tensor is used to investigate the radial force density distribution in air gap. Since the EMV causes stability issues and disrupts the system performance, structural and EMV analyses were performed to investigate the influence of converter topology on stator vibrations.