Design of a new robust controller for voltage regulation of DC link in wind‐farm‐side converter integrated with a hybrid AC and DC large‐scale power system

Abstract

The main aim of this paper is to improve dynamic performance of a multi-terminal DC (MTDC) grid in a wind-integrated AC power system through DC voltage control. The proposed approach is based on design of robust H ∞ controller and loop shaping along with mutual quality decomposition method (MQDM). For extracting transfer function of the plant, model of Master-Slave control system is converted to standard feedback control system. Then, based on the obtained difference between singular-value curves of the main open-loop system and the proposed method, the weighting functions of robust H ∞ controller are selected. In the next step, by using the MQDM technique, the transfer function ofthe system in state-space form is evaluated to extract gain of the robust controller. For practicality of the conducted approach, singular-value order reduction Hankel algorithm along with frequency response analysis have been used for designing the gain of the robust controller. The developed method has been implemented on the MTDC converter in the wind farm side to control the voltage of DC grid. The simulations are accomplished in MATLAB, where by considering different uncertainties in the DC grid, wind unit, and the AC grid, robustness of the proposed approach has been clearly demonstrated.