Coordinated Robust Supplementary Controls in Embedded VSC-HVDC Lines for Damping Electromechanical Oscillations

Abstract

Damping of weak electromechanical modes can be improved by means of supplementary controllers placed at embedded High Voltage Direct Current (HVDC) lines based on Voltage Source Converters (VSC) technology. For this purpose, some robust controllers H∞ are proposed based on local single input single output (SISO) linear models of the power system placed at the inverter station or at the rectifier station. However, when a HVDC is an embedded line, it is useful to coordinate the supplementary controllers at the inverter and rectifier stations in order to improve damping on different electromechanical modes of the AC power system. This paper proposes two strategies to achieve a system of coordinated supplementary H∞ controllers placed at each converter station (inverter and rectifier). Firstly, a MIMO H∞ mixed-sensitivity centralized control strategy of both inverters is initially proposed, then a decentralized one is proposed. In both cases, the modelling of the power system dynamic, observed at each VSC converter station, is computed by means of the identification technique N4Sid using data from simulations. The performance of these proposed controls is compared to classic control known as Power Oscillation Damping (POD). On the other hand, since each controller uses remote signals their robustness is tested taking into account signals delays.