Microgrid Primary Controller Performance Characterization

Abstract

This chapter reviews the main types of primary controllers for grid-forming converters found in microgrids with multiple distributed converter-based energy resource units. The main type of primary controllers are droop, virtual synchronous generator and dispatchable virtual oscillator, and some variations are described aiming to reveal their dynamic behavior and select their control parameters. This establishes the foundations for a fair comparison among the primary control alternatives considered. The large and small signal models for the primary controllers are derived, and it is demonstrated how the primary controller parameters impact the steady-state and transient behaviors; in addition, time domain simulation on Hardware-in-the-Loop (HIL) illustrates their performance. Since the microgrid controller presents different scenarios of operation, an automated Test-Driven Design (TDD) reveals from extensive simulations in the time domain the strong and weak points of each primary controller. Initially, metrics for both steady-state and transient performances are defined. Then, the key scenarios based on each operating mode such as grid-connected, islanded and unplanned islanding are selected to carry out the tests. Finally, an automated report is given, revealing the strengths and weaknesses of each considered a primary controller.