Analysis and Engineering Solution of High-frequency Oscillation Caused by Integration of Islanded Renewable Energy Station into MMC-HVDC System

The problem of high-frequency oscillation in flexible DC electric power transmission is increasingly prominent in recent projectselectronic. The high-frequency oscillation phenomenon occurred many times during the system commissioning of the zhangbei flexible DC grid project. In this paper, the reasons of high frequency oscillation caused by integration of islanded renewable energy station into converter station were analyzed. Through the analysis of the impedance characteristics of the converter and the AC system, it is found that the impedance bode diagram of the converter and the AC system has the same amplitude and opposite phase at the frequency point of the high frequency oscillation. There is a risk of oscillations. The operation mode circumvention and open-closed-loop conversion strategy have been put forward which have successfully solved the problem of high-frequency oscillation in combanoer converter station. The effectiveness of the proposed measures were verified by subsequent engineering tests.