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Protection of an islanded inverter‐based microgrid is challenging because of variable and small fault current contribution of inverter‐based resources (IBR) and the absence of sequence currents. This paper proposes a fast and robust nonpilot directional protection scheme to address this challenge. This scheme relies on support vector machines (SVM) and the harmonic current injection capability of IBRs. Examining the harmonic currents measured by a relay during a fault shows that harmonic currents have similar magnitudes but different orientation under forward and reverse faults. Additionally, harmonic currents have similar orientation but different magnitudes under forward faults at different locations along the protected line. Using this, six SVMs are trained for each relay, given that there are three main types of faults (three‐phase‐to‐ground, line‐to‐line, and line‐to‐ground): three as directional elements and three as zone detection elements. A fault is detected and classified by the undervoltage element of a relay. Then, the measured harmonic currents are routed to the appropriate directionality and zone detection SVMs to facilitate proper relay coordination. The performance of the proposed method is evaluated on the CIGRE North American MV distribution benchmark system under various types of contingency scenarios using PSCAD/EMTDC software.

 

Integration of wind energy resources into the grid creates several challenges for power system dynamics. More specifically, Type-3 wind turbines are susceptible to subsynchronous control interactions (SSCIs) when they become radially connected to a series-compensated transmission line. SSCIs can cause disruptions in power generation and can result in significant damage to wind farm (WF) components and equipment. This paper proposes an approach to mitigate SSCIs using an online frequency scan, with optimized phase angles of voltage harmonic injection to maintain steady-state operation, to modify the controllers or the operating conditions of the wind turbine. The proposed strategy is simulated in PSCAD/EMTDC software on the IEEE second benchmark model for subsynchronous resonance. Simulation results demonstrate the effectiveness of this strategy by ensuring oscillations do not grow. 

In recent years, penetration of renewable energy resources into the power grid has increased significantly. Wind, as a renewable, clean, and abundantly available source of energy, has an important share in the energy mix. However, increasing the penetration of wind power in the power grid can adversely affect the power quality and introduce new operational challenges. This paper discusses issues related to the integration of wind farms in the power system, such as maximum power point tracking, fault ride-through capabilities, interarea and subsynchronous oscillations, and voltage flicker, and provides a review of the existing control strategies to address these issues in Types I, II, III, and IV wind turbines. This paper also identifies challenges and opportunities ahead.