Observer-Based Grid-Forming Converters Using Only the Converter-Side Current Sensors

Grid-forming (GFM) converters are regarded as the enabler of more-electronics power systems. However, existing GFM converters typically require a plenty of sensors, which lead to a sizable increase in system cost and complexity. To address this problem, this article proposes an observer-based GFM converter that only uses the converter-side current sensors. Specifically, we construct an internal model-based extended state observer (IM-ESO), which takes converter-side currents as the inputs, to achieve precise observation of ac capacitor voltages, grid-side currents, and the voltages of the point of common coupling (PCC). This enables the removal of the corresponding sensors. Subsequently, we design a multiloop controller on the basis of IM-ESO to realize power and voltage control of GFM converters. Through careful analyses, the stability and robustness of the proposed GFM converter are verified. Compared with conventional GFM converters, the proposed GFM converter achieves up to a 75% reduction in the number of sensors while still maintaining satisfactory control performances. The effectiveness of the proposed GFM converters is validated by experimental results.