Challenges of Power Converter Operation and Control Under Ferroresonance Conditions.

This paper presents the challenges that the power converters with $dq$ -frame-based control confront when subjected to ferroresonance. This is mainly due to two main properties of the widely used $dq$-frame control systems. It is demonstrated in this paper that regardless of the phase-to-ground or phase-to-phase voltage measurement, the $dq$-frame control only responds to phase-to-phase voltage variations. Furthermore, the PI controllers, which are employed in conjunction with the $dq$ reference frame, can inherently only track dc references and reject dc disturbances. Consequently, a $dq$ -based PI controller can only respond to the positive-sequence phase-to-phase voltage variations, effectively. This, in turn, limits the disturbance mitigation capability of the power converter. This study investigates the impacts of the ferroresonance phenomenon on the control system response and the operating conditions of the power converters. Based on a droop-based $dq$ frame controller, the behavior of an electronically interfaced distribution generation system is studied, under various transient conditions. In spite of a promising performance under the load change and islanding scenarios, the $dq$-frame-based controller of the power converter fails to detect and respond to the voltage fluctuation and excessive overvoltages as a result of ferroresonance. [ABSTRACT FROM AUTHOR]