Multitimescale Three-Tiered Voltage Control Framework for Dispersed Smart Inverters at the Grid Edge

Voltage control schemes are being employed to guarantee that the voltage across the grid stays within the predefined boundaries. Growing number of smart PV-based inverters (SPVIs) necessitates cutting-edge control schemes to ensure addressing voltage fluctuations suitably aligned with the existing grid codes. Designing such control schemes for grid clusters with high penetration of SPVIs is complex and depends on various agencies, such as configuration of the clusters and physical limitations of the SPVIs, themselves. This article proposes a multitimescale three-tiered voltage control framework for dispersed SPVIs at the grid edge. The uppermost tier called the long-term supervisory tier oversees the entire grid cluster to make sure that total generation and consumption on the cluster are balanced while power delivery losses are minimized and voltage across the grid is within the permissible boundaries. In short term, the middle tier of the proposed framework called short-term distributed tier ensures cooperative operation of the SPVIs for establishing short-term voltage stability across the cluster in a subsecond timeframe. The undermost tier, called the model-predictive-based local tier, fulfills the operational commands dictated by the upper layers with fast dynamics. By implementing the proposed control framework, the SPVIs will participate in voltage regulation across the grid in occurrence of rapid voltage fluctuations while keeping the entire distribution grid at the optimal operating condition for a long term. The proposed multitimescale three-tiered control framework is verified by simulation.