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• An innovative three-stage hybrid framework is developed for RODNP problem. • Multi-objective resource allocation is done to boost normal and emergency conditions. • The most conservative scenario is used to assess the potential hurricane's impact. • A risk-averse hardening re-plan is done in the third stage to improve system's resilience. • Different planning and operational measures are adopted for resilience enhancement. This article tackles the resilience-oriented distribution network planning (RODNP) problem utilizing a novel three-stage hybrid framework. The decision-making on the line hardening and DG placement is carried out in the first stage. In the second stage, emergency and normal operation optimization are conducted. The worst-case scenario is considered for evaluating the effect of a potential hurricane in post-event emergency operation conditions. In addition, a scenario-based stochastic approach is used to assess normal operation conditions. Finally, a risk-averse hardening re-plan is implemented in the third stage using the information gap decision theory (IGDT) notion as an effective non-deterministic optimization strategy under severe uncertainty. At this stage, distribution system planner (DSP) tries to develop a more resilient distribution network scheme against the most powerful hurricane possible while taking into account a predetermined parameter known as the resilience budget. The efficacy of the proposed approach is validated by conducting several case studies on the IEEE-33 bus test system. The results reveal that the proposed strategy may dramatically reduce the cost of both normal and emergency operations simultaneously. [ABSTRACT FROM AUTHOR]

• A weak bus identification index is derived to identify the critical bus when power flow is unsolvable. • An extended system considering new bus type is proposed to improve power flow solvability. • A weak bus identification and bus type switching based framework is established to provide adjustment measures efficiently and automatically. • The method could provide a suitable solution automatically for unsolvable power flow in a variety of scenarios, retains stable convergence and has potential in large-scale power grids. The power flow solvability is greatly challenged by the growing pressure on power grid induced by the rapid development of economy. The approaches of restoring power flow solvability should be profoundly studied. Most of adopted power flow adjustment methods are based on manual interference which require extensive human resources with inefficiency. Thus, a power flow adjustment strategy based on a weak bus identification and a new bus type conversion is proposed. A weak bus identification index is defined and expressed when power flow has no solution. We propose a novel bus type and a concept of the power shortage to restore power flow solvability. The generator action set is determined by calculating the left eigenvector of the Jacobian matrix. At last, we establish a linear programming model to determine the generator output adjustment. Numerical results are obtained in 3 test systems and an actual system in China. Compared with other methods, the proposed method is verified to have a higher success rate of restoring power flow solvability and has robustness in various scenarios. [ABSTRACT FROM AUTHOR]

• The model requires only pre-fault steady state information and the impact data at the fault occurrence period. • The method can provide multivariate STVS indices of each bus, and identify the instability patterns. • The heterogeneous graph attention network HGAT combine the zoning characteristics with the influence of bus type. • The improved multi-tasking learning (MTL) algorithm is proposed. • Excellent accuracy and robustness to topological changes. Compared with time-domain simulation (TDS), data-driven models show great advantage in time consumption of the power system security analysis. This paper proposes a novel graph neural network (GNN) based model for the short-term voltage stability (STVS) assessment. Based on mainly the steady-state information as the inputs, the model can provide multivariate stability indices for each bus and adapt to minor topological changes. Both the fast voltage collapses (FVC) and fault-induced delayed voltage recovery (FIDVR) events can be identified. A modified multi-task learning (MTL) process improves the multi-index evaluation performance of the model. As the kernel of the model, a heterogeneous graph attention deep network (HGAT) with various types of nodes works to aggregate the local information and generate new features. Then several micro-detectors scan over the network to provide the STVS indices of each bus with only the feature vector of one node as input for the prediction. Comparisons on the test system show that the proposed method can provide fine-grained STVS evaluation and show good robustness in the scenarios of different dynamic load distribution and network topology changes. [ABSTRACT FROM AUTHOR]

• Bus splitting is a powerful tool in relieving transmission network congestion. • Line switching and bus splitting are employed to minimize the operation cost. • AC feasibility and compliance with N-1 contingency requirements are considered. • A pre-screening step is proposed to select candidate substations for reconfiguration. Optimal transmission line switching and/or bus splitting is shown to contribute in relieving congestion and reducing the operation cost by rerouting power flows throughout the network. Although bus splitting may be as powerful as line switching in congestion mitigation and is typically considered a smaller disturbance compared with line switching, it has received less attention in the literature in part due to the more complicated node-breaker modeling requirement. In this paper, an optimal transmission line switching and bus splitting heuristic is presented to minimize the operation cost while respecting AC and N-1 contingency constraints. We present a two-level solution method where switching decisions are made in the upper level problem formulated as a mixed integer second order cone programming master problem, while the resulting network topology is checked against AC and N-1 contingency constraints in lower level subproblems. Line switching and bus splitting are modeled as switching actions assuming double-bus double-breaker substation arrangements where all elements at a substation, including generators, loads, lines and shunt elements, are given switches to connect to either of the busbars if the respective substation is split. We also introduce additional constraints to model a breaker-and-a-half substation scheme. Furthermore, a pre-screening step is presented to limit the search space of the problem, thus accelerating the solution process. We demonstrate the application of the proposed method on IEEE standard test systems. [ABSTRACT FROM AUTHOR]

• A new dynamic-adaptive load shedding technique is proposed. • Load buses are ranked and feeders are dynamically selected for load shedding. • Effectiveness of the proposed methodology is demonstrated via simulations. Frequency stability is one of the major concerns for secured operation of a power system. A severe disturbance causes rapid frequency decline, which may instigate power system blackout in an extreme case. In emergency situations, load shedding is applied to arrest frequency excursion. Therefore, a load shedding scheme needs to be sufficiently adaptive to tackle sudden generation loss. Note that conventional load shedding schemes may fail to provide satisfactory frequency response in certain cases. To address this challenge, a new dynamic-adaptive load shedding mechanism is proposed in this paper. The proposed methodology considers the actual contingency size, frequency sensitivity due to load damping, frequency response and ranking of load buses according to voltage stability index. The method ensures that the actual load cut is sufficiently close to the required load shedding to keep system frequency within the given acceptable limit. To do so, it ranks the load buses within a zone and dynamically selects appropriate feeders for load shedding. It also proportionally applies higher amount of load shedding to relatively weaker buses for taking care of the voltage stability. To examine the performance of the proposed scheme, it is applied to the IEEE 39 bus test system that is divided into six zones. It is found from simulations that for 600 MW, 700 MW and 900 MW generation loss events in zone-3, the required amounts of load shedding are 430 MW, 531 MW and 730 MW respectively to keep system frequency above 49.1 Hz. However, these quantities increase to 450 MW, 550 MW and 749 MW respectively to retain system frequency above 49.2 Hz. Furthermore, the impact of 400 MW generation loss in zone-1 is explored. It is found that after shedding additional loads in zone-1 and zone-2, the risk of tie line overloading is mitigated that eventually assures tie line security. In addition, performances of the proposed algorithm are compared to that of an adaptive technique and a semi-adaptive technique. It is noticed that the proposed methodology provides better results than the existing methods. Therefore, it can be articulated that the developed scheme ensures the correct amount of load shedding to maintain satisfactory frequency response and voltage stability. [ABSTRACT FROM AUTHOR]

• Method is independent of initial guess of allowable transaction for ATC calculation. • Accurate computation of ATC, even under stressed system condition. • Fast computation of ATC in comparison with NRPF based method. • Proposed method is tested and validated on IEEE 30, 118 and 300-bus test system. • Tested for bilateral and multilateral transactions at different operating points. Available Transfer Capability (ATC) is the additional power that can be securely and reliably transacted over and above the already committed transactions in a power network. In the electricity market, where every player (power producer and consumer) tries to earn higher profit, quick and accurate assessment of ATC of the power network is a prime concern. Holomorphic Embedding (HE) is a novel and non-iterative way of solving the Power Flow (PF) equations, which guarantees to find the operational High Voltage (HV) solution, in case it exists. Analytic continuation extends the domain of convergence of non-analytic functions to have voltage solutions. This paper, thus, proposes an extremely efficient and accurate approach for evaluation of ATC using the Holomorphic Embedded PF (HEPF) considering the intact system condition and N - 1 contingency situations. This approach is successfully tested on IEEE 30 bus, IEEE 118 bus, and IEEE 300 bus systems for various bilateral and multilateral transactions. The results, thus, obtained prove the efficacy of the proposed approach in comparison with those obtained from the repeated Newton-Raphson PF (NRPF), Fast Decoupled PF (FDPF) and Continuation PF (CPF) based methods. [ABSTRACT FROM AUTHOR]