Large-scale adoption of grid-forming inverter controls to enable ancillary services modeling and evaluation for microgrids

High penetration of renewable energy sources (RES) operating as part of large interconnected systems can positively and negatively impact the security of the supply of electrical power systems. It is because there is no rule to determine the safe penetration level. Advanced power electronic technology protects the network from voltage instability and fluctuation, poor power factor, harmonics, DC bias, AC bus voltage magnitudes variation, and transient stability issues. Grid-forming (GFM) inverter control algorithms are applied in an interconnected system (IS) consisting of node regions with non-linear loads to cope with these issues. GFM inverter is a cost-effective device used to interface between the grid and RES, such as solar panels, wind turbines, and energy storage. It works autonomously to convert power in DC to AC form at the required frequency and voltage output by always-on universal droop control without external communication or phase-locked loops. This device needs a robust control strategy to face disturbances (e.g., grid voltage and frequency issues, blackouts). This research used a systematic methodology for characterizing the performance of the GFM power inverter control algorithms. This process was accomplished using an advanced real-time simulator tool called HYPERSIM developed by OPAL-RT for high penetration of renewable energy resources in the grid. These controllers are adopted, developed, and simulated step by step, scaling a test feeder with 120-inverters and 1200-node system. The newest and most mature controller consists of re-synchronization with the grid in 2 s and short circuits at specific times. The applicability of the developed control technology to other DERs is essential for commercialization. The GFM power inverter performance was validated in different feeders through extensive simulations in a real-time simulator tool. Simulation results show the scalable characteristic of the proposed adoption and keep voltage and frequency variation within specific ranges to protect the grid against voltage instability and fluctuation, an unsuitable frequency when operating in on-grid and off-grid and provide black-start capability in case of prolonged blackouts. The accuracy of the method was developed by comparing the voltages p.u. results obtained from the test utility feeders with the Open Distribution System Simulator (OpenDSS) results and with the GFM inverters was validated. The proposed approach seamlessly manages the data available from the GFM inverter control algorithm adoption through the final scalable control model verification available. The proposed approach seamlessly manages the data available from the optimization procedure through the final model evaluation.

Embargo status: Restricted until 06/2173. To request the author grant access, click on the PDF link to the left.