A Novel Inverter Based Resource Control Strategy to Facilitate Utility-Scale Renewable Integration and Retain Existing Transmission Protection Infrastructure

Abstract

Renewable generation capacity in the North American electric grid is expected to expand considerably over the next few decades. Photovoltaics and type-4 wind turbines connected to the grid via power electronic inverters have a significantly different fault response than conventional synchronous generators. The existing protection infrastructure for the North American transmission network was not designed with the behavior of these Inverter Based Resources (IBR) in mind. As IBR penetration continues to increase, the overall system behavior under faulted conditions may change to the point where protective relays may fail to accurately detect the location of a fault. This thesis proposes a novel control strategy for utility-scale inverter-based resources designed to ensure proper operation of the existing transmission-line protection infrastructure. The fault response of an IBR depends on its control logic which varies between manufacturers, but typically will resemble its pre-fault behavior of generating balanced three-phase currents. Transmission-line protective relays rely upon the unbalanced currents produced by synchronous generators to accurately determine the fault location. By controlling IBRs to emulate synchronous generator fault behavior, protective devices see the quantities they expect and require for proper operation. This will allow electric utilities to retain their existing protection infrastructure, eliminating the need for any costly equipment upgrades and operational downtime.