Design of DC Voltage Controller for Master Station Based on System-Level Modeling in MTDC System

Maintaining a constant DC voltage is essential for coordinating the control of these interconnected systems as fluctuations in the DC side can lead to nonlinear effects between the converter stations and instability in the power network. This study aims to overcome this challenge by proposing an system-level small signal modeling method based on harmonic linearization. This method allows for the analysis and effective handling of the time-varying, nonlinear, and multi-converter station coupling equations. By focusing on the dominant harmonics that affect the DC bus, this model simplifies the nonlinear harmonic coupling within and between converter stations. Additionally, a quantitative design method for the DC voltage controller parameters is proposed based on the integrated model. The design considers the mutual influence between stations, allowing the controller to extend its reach from single converter control to the entire multi-terminal system. Finally, a simulation model is developed in PLECS software to demonstrate that the controller can quickly restore the system's dynamic balance.