An Optimal Load-Frequency Control Method for Inverter-Based Renewable Energy Transmission

The frequency droop response of conventional turbine driven synchronous generators with respect to load increases is normally used in order to have stable operating characteristics for multiple generators operating in parallel over large geographical regions. This presents a challenge for renewable energy sources that interface to the transmission grid through static inverters that do not exhibit an intrinsic frequency droop characteristic. This paper provides a technique for designing optimal load frequency controllers as transmission line inverters fed from renewable energy sources that allows for fast dynamic response due to variable solar and wind conditions while maintain stability to interconnected synchronous generators. A control technique based on LQG optimization theory is presented. Detailed analysis of a three-area system in a region of mixed wind and solar photovoltaic sources is modeled in a manner that confirms the effectiveness of the disclosed load-frequency control method.