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Inverter-Based Resources (IBRs), including Wind turbine generators (WTGs), exhibit substantially different negative-sequence fault current characteristics compared to synchronous generators (SGs). These differences may cause misoperation of customary negative-sequence-based protective elements set under the assumption of a conventional SG dominated power system. The amplitude of the negative-sequence fault current of a WTG is smaller than that of an SG. This may lead to misoperation of the negative-sequence overcurrent elements 50Q/51Q. Moreover, the angular relation of the negativesequence current and voltage is different under WTGs, which may result in the misoperation of directional negative-sequence overcurrent element 67Q. This paper first studies the key differences between the WTGs and SG by comparing their equivalent negative-sequence impedances with SG's. Then, simulation case studies are presented showing the misoperation of 50Q and 67Q due to wind generation and the corresponding impact on communication-assisted protection and fault identification scheme (FID). The impact on directional element is also experimentally validated in a hardware-in-the-loop real-time simulation set up using a physical relay. Finally, the paper studies the impact of various factors such as WTG type (Type-III/Type-IV) and Type-IV WTG control scheme (coupled/decoupled sequence) to determine the key features that need to be considered in practical protection studies. The objective is to show potential protection misoperation issues, identify the cause, and propose potential solutions.

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Large-scale integration of wind generation changes the power swing characteristics of a power system and may result in the misoperation of legacy power swing protection schemes. This paper presents a qualitative study on the impact of wind generation on power swing protection. The objective is to provide an understanding of the problem through case studies and present possible solutions and adjustments in protection schemes to ensure the efficiency of protection under large-scale integration of wind generation. The misoperation of power swing protection functions, namely Power Swing Blocking (PSB) and Out-of-Step Tripping (OST), as a result of increased wind generation levels, are shown through case studies. It is also shown that the electrical center of a power system may move due to wind generation. In this case, it would be necessary to revise the optimal location of the OST protection. Finally, the impact of various factors such as wind generator type, control scheme and Fault-Ride-Through (FRT) function, and wind generation level and capacity are investigated to determine the key features that need to be accounted for in practical protection studies.

The unbalanced nature of distribution systems requires a multiphase load-flow solution capable of handling arbitrary network topologies and providing accurate results. The need for detailed analysis of secondary grid systems found in dense urban areas and the modeling of distribution networks including the subtransmission level requires using highly efficient and large-scale system-capable methods. In this paper, three different load-flow solution algorithms are presented using the modified-augmented-nodal-analysis formulation. The load-flow solution algorithms are compared for the IEEE 8500-node distribution test feeder using a proposed regulator tap control strategy.

The power system planning and protection studies are becoming more challenging due to the rapid increase in penetration levels of converter-interfaced renewables. Type-IV wind turbine generators (WTGs) and photovoltaic panels (PVs) are interfaced to the grid through a full-scale converter (FSC), and their short-circuit current contributions are mainly designated by the converter control and associated current limits. This paper proposes a new phasor domain modeling approach for the wind parks (WPs) with Type-IV WTGs using the concept of controlbased equivalent circuits. The proposed model precisely represents the detailed electromagnetic transient type (EMT-type) model in steady state and is able to account for the fault-ridethrough (FRT) function of the WTG control as well as its specific decoupled sequence control scheme in addition to the traditional coupled control scheme. Although the collector grid and WTGs inside the WP are represented with their aggregated models, the overall reactive power control structure of the WP is preserved by taking the central wind park controller (WPC) into account. The accuracy of the proposed model is validated through detailed EMT simulations.

This paper presents a new method to model induction machines (IMs) in multiphase load-flow calculations. Fast convergence of the load-flow solution is achieved using an iterative Newton method in the modified-augmented-nodalanalysis (MANA) formulation. The multiphase modeling approach allows accounting for unbalanced networks. The IM is modeled using either a constraint of electrical power input, mechanical power or mechanical torque output. The slip of the IM becomes a load flow variable computed iteratively while the reactive power is not fixed. In addition, the initialization of time domain simulations using load flow solution in the computation of electromagnetic transients is demonstrated using balanced and unbalanced network cases. It is shown that a seamless transition between load-flow and time-domain average powers is obtained when the slip of the IM is formulated as a variable in load flow and its reactive power is not fixed.