Negative-Sequence Current Injection of Transmission Solar Farms

Integrating solar generation brings about unique challenges in power system protection. Previous studies have found inverter-based resources featuring distinct fault responses compared to conventional generators. The reduction in fault current magnitude and lack of negative and zero sequence currents can fundamentally impact the way that the power system is protected. This letter studies the negative-sequence current injection from transmission-connected solar farms. Using field recorded data, this letter reveals the negative-sequence current injection behaviors of solar farms by analyzing how inverters respond to faults. In addition, the paper studies how the negative-sequence current can impact negative-sequence directional elements used in protective relays. The response of protective relays' is evaluated by replaying field events using actual relay settings applied on conventional systems.