제주 전력계통 외란 시 신재생 전원 추가 정지에 대한 주파수 변화 분석

Abstract

According to the policy of renewable energy for the past few years, the penetration rate of renewable energy in Jeju Island has been steadily increasing. Because of this, the frequency of generating more than 60% of real-time renewable power sources in the Jeju power system is gradually increasing. It is expected that this trend will continue in the future to curb climate change. However, the increase in renewable power in the system adversely affects the system frequency due to the characteristics of the power source. Since renewable energy is difficult to predict and considerably variable, it is difficult for system operators to respond to it. In particular, in recent years in Korea, due to the frequency drop due to grid disturbance, a renewable power source has been dropped, causing an additional frequency drop. This occurred because the solar inverter was not set for low frequency or low voltage. The ability of the power supply to maintain grid connection when an accident occurs in the grid is called FRT (Fault Ride Through). However, the mandatory function of the renewable FRT function was established in the electricity market operation rules in October 2020. So, The FRT function is no longer compulsory for renewable generators that have entered the system before that. In the past, this problem did not come up because renewable energy did not take up a lot of weight, but recently, the supply rate of renewable power has risen sharply. As the system is operating in an exposed state, countermeasures are necessary. Therefore, in this paper, the concept of Power system frequency is presented and the effect on frequency variation according to the characteristics of renewable power sources is investigated. In addition, the current status of domestic and overseas FRT standards was investigated, and the proportion of renewable power sources lacking FRT function among the current power system in Jeju was investigated. In addition, we introduced the case of additional trip of renewable energy that occurred recently in Korea, and analyzed the frequency stability through PSS/E simulation. Three cases of disturbance were applied based on the power system situation with the highest proportion of actual renewables. Among these three disturbances, cases in which additional trip of renewable energy is expected were derived, and the frequency variation was analyzed by simulating the additional trip of renewable energy in the derived case