Fault Current Limiting and Grid Code Compliance for Grid-Forming Inverters — Part II: Solution

Abstract

Part I of this paper unveiled various shortcomings of existing fault current limiting (FCL) methods for grid-forming (GFM) inverters. Part II of this paper develops a new FCL method that overcomes these drawbacks. Additionally, the FCL method proposed in this paper follows the strict requirements of recent grid codes for the low-voltage ride-through mode of inverter-based resources (IBRs). This makes the exact response of GFM inverters during faults fully predictable. Such predictability is a prerequisite for the reliable design/setting of protection systems, operation, and planning of power grids with high penetration of IBRs. The paper uses PSCAD simulations to corroborate if the proposed method meets these objectives. It also uses simulation results to compare this new method with existing FCL solutions for GFM inverters.