Modified Sliding-Mode Controller for the Line-Commutated Converters of Back-To HVDC Systems

Abstract

Line-commutated converter (LCC) high-voltage direct current (HVDC) systems are currently the most attractive valve converter topology for large-scale HVDC networks due to their high efficiency, low initial installation cost, low power loss, high system stability, and high reliability. This study presents a detailed study of LCC back-to-back HVDC converter stations, identifies the major components of such systems for parameter calculations and supports them with mathematical operations, explains the control methods of the rectifier and inverter units, and proposes a new controller structure. To elucidate its advantages, the proposed controller structure for LCC-HVDC converter stations is compared with other controller structures, namely, the classical proportional-integral (PI) controller and the anti-windup PI controller. The simulation results are obtained from the PSCAD/EMTDC software package. The comparison of the system results, such as settling times and maximum and minimum values for the three controllers, indicates that the proposed modified sliding-mode-based controller (MSMBC) outperforms the two other controllers in all aspects. Therefore, the proposed MSMBC makes highly important contributions to LCC-HVDC converter systems and is superior to other controllers due to its significant advantages.