Reevaluating Converter Control Functionality through a Unified Integral Control Framework

This paper introduces the Unified Integral Control (UIC) framework, as a generalization of fundamental converter control functionality. The UIC is used to systematically attribute synchronization, dispatch, and either droop or perfect tracking behavior to specific control mechanisms. We investigate similarities and differences in grid-forming schemes such as dispatchable Virtual Oscillator Control and Droop Control, as well as grid-following control. When the controllers are expressed as complex differential equations in a constant frequency frame, they equate to the UIC. The equivalence is confirmed through simulations in PSCAD. The framework yields complementary insights on the choice of filtering, point of dispatch, and time-domain operation. This is used to showcase PLL-less GFL operation and Droop control without the need for power filtering. These findings show how the UIC provides a framework to unify apparent differences in control implementations and facilitates a functionality-based perspective.