재생에너지의 전력계통 수용한계 설정 방법에 관한 연구

Abstract

Jeju provincial government is pushing ahead with an ambitious plan to supply a hundred percent of Jeju's power demand with renewable energy by 2030 under the catch phrase of Carbon Free Island 2030. According to Jeju CFI 2030 plan, it aims to install 3.8 GW of VRE (Variable Resource Energy) comprising PV Solar 1.4 GW, On Shore Wind 0.5 GW, and Off Shore Wind 1.9 GW by 2030. South Korean government also announced a plan to supply 20 percent of power demand with renewable energy by 2030 through the 8th Basic Plan for Long-term Power Supply and Demand. The government is actively promoting support and systematic improvement for renewable energy projects through active energy transition policies. As a result, Jeju Island, which is rich in wind resources, has seen its wind farms steadily increase since 2007. And PV have been increasing rapidly owing to the government's active support policy for renewable energy since 2016. Jeju Island is an independent power system separated from Korea's Main Land and is connected by two HVDC (High Voltage Direct Current) lines. As of 2019, the average power demand of Jeju power system is 650 ㎿ and peak power demand is 960 ㎿. The traditional generators consist of nine thermal and combined cycle generators in three generation farms, with a total capacity of 777 ㎿. Variable renewable energy (VRE) resources totaling 501 ㎿ , including 265 ㎿ of wind power and 236 ㎿ of PV, are also connected to the power system. With the recent increase of VRE, wind power curtailment has occurred because the power generation exceeds the power demand. Starting with three times in 2015, the number of wind power curtailment is increasing every year. It has occurred 23 times so far in 2019 up to September and accounted for 1.2% of the total wind power generation as 4.4 GWh. In particular, during low power demand period of spring and autumn season, the Duck Curve phenomenon became noticeable and wind power curtailment occurs mostly during the daytime around noon with increase of PV. Even in this situation, additional PV projects are being rapidly connected to power system, and the Jeju provincial government is also actively promoting the proliferation of renewable energy. This dissertation studied the setting method of acceptable VRE limit in the Jeju power system, which is operated independently and has transmission from the Main Land power system constrained. Mid-to long-term demand should be forecasted while maintaining the pattern of seasonal, daily, special low demand period such as holiday season for simulation of VRE marginal capacity. This paper described the proper judgment and setting method for the capacity factor of wind power and PV. To predict exact excess power generation, this paper prepared data that properly maintained the seasonal, monthly, and hourly generation characteristics of VRE and described the forecasting method according to the expected installed renewable energy capacity in the future. This dissertation found that the ratio of installation capacity of wind power and PV should be 50:50 in order to minimize excess power generation and gain the highest profit in the Jeju power system. In accordance with the above method, this paper determined the yearly operational VRE capacity by repeatedly evaluating which renewable projects gain proper profit by not significantly exceeding the forecasted excess generation. Sensitivity of marginal capacity was analyzed as method of increasing acceptable and proper renewable energy marginal capacity. As a result, Jeju power system, which is expected to have an average power demand of 981 ㎿ in 2030, excess power generation will not occur with the installed VRE capacity of 1,125 ㎿. There will be 0.5 % excess power generation with the installed VRE capacity of 1,325 ㎿ (+200 ㎿), and 1.8 % excess with 1,525 ㎿ (+400 ㎿). For the last case, if ESS (Energy Storage System) of 200 ㎿ is installed and operated, excess power generation can be reduced from 1.8 % to 0.5 %. This dissertation concludes that 3.8 GW of VRE aimed by the Jeju provincial government cannot be acceptably installed under the current Jeju power system's operational environment. Instead, up to 1.5 GW of VRE can be installed, with an ESS of over 200 ㎿ being installed and operated to mitigate excess power generation.