The impact of inverter based systems on power grid stability

Abstract

Driven by urgent concerns about the impact of greenhouse gas emissions and associated global warming, electric power systems around the world are currently undergoing a rapid transformation away from traditional carbon based energy sources and toward less polluting energy sources including renewables such as wind and solar. This transition is more challenging than is often realized and a number of complex issues must be overcome in diverse areas such as politics, economics, social equity, and technology. Among the great many technical challenges is the question of maintaining supply reliability and grid stability as increasing amounts of renewable energy sources are injected into the existing synchronous generator based grid via grid-tied power electronic inverter systems. This thesis explores this important grid transition stability question when solar energy is injected into the existing grid via photovoltaic cells and grid-tied inverters with certain control strategies. It is shown that serious grid instability leading to grid failure will occur under certain levels of inverter injected power, It is also shown that the level of grid-tied inverter injected power can be increased for certain inverter control loop designs such as virtual synchronous machine loops and also when additional technology such as synchronous condensers are employed.