Controlling Grid-Forming Inverters to Meet the Negative-Sequence Current Requirements of the IEEE Standard 2800-2022

Abstract

As an integral component of power systems dominated by inverter-based resources (IBRs), grid-forming (GFM) inverters must ride through low voltages. During an asymmetrical low-voltage ride-through (LVRT) condition, the recently approved IEEE Standard 2800-2022 requires that all IBRs absorb negative-sequence reactive current as a function of the voltage at the IBR's terminal. However, existing GFM control methods either suppress the negative-sequence component of the fault current or leave it uncontrolled. To address this issue, this article develops a control scheme that makes GFM-IBRs absorb reactive current in the negative-sequence circuit while they regulate the voltage in the positive-sequence circuit. The developed control system includes a new adaptive virtual impedance-based current-limiting scheme to limit the inverter's current during both initial transients and steady-state fault conditions. To meet the maximum phase current utilization requirement of the IEEE Std. 2800-2022, the paper also develops an adaptive sequence current division scheme. PSCAD/EMTDC simulations of a CIGRE transmission network benchmark supplied primarily by IBRs verify the compliance of the proposed control system with the IEEE Std. 2800-2022.