Sensorless Active Damping in Switching Frequency Constrained Medium Voltage Multi-Megawatt Grid Forming Converters

Abstract

A key limitation of existing state of the art for grid forming (GFM) control in switching frequency constrained medium voltage (MV) multi-megawatt (MMW) scale applications is analyzed and a potential solution is subsequently proposed. To facilitate over-current limiting and fault ride-through, GFM applications mandate fast current regulation and resonance damping, which should be achieved through active control using minimal hardware components and/or sensors. A comparative analysis of control performance is presented between a low voltage and a MV system, which demonstrates that lack of sufficient time-scale separation among the cascaded compensator loops in the latter may lead to substantial performance degradation or even instability. A state-estimator based control structure is proposed for such systems. The proposed analysis and controller is validated through real-time control-hardware-in-the-loop (CHIL) experiments.