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This paper presents a novel methodology for the construction of a transient stability boundary (TSB) that overcomes the lack of TSB analytical description for multiple operating states and contingencies in power systems. The proposed approach models the TSB as a nonlinear mapping between the system parameters of interest and the corresponding critical clearing time (CCT). This compact mathematical expression is built based on an efficient discriminative network, broad learning system (BLS). While keeping a high accuracy and generalization ability, the newly introduced construction method provides an efficient update strategy that does not require an entire retraining cycle. These properties make this method suitable for online transient stability assessment (TSA). The prospects of the developed method are verified via case studies by employing the IEEE 9-bus, IEEE 39-bus (New England) test systems and a real system of China Southern Power Grid. In comparison with existing methods, the newly introduced algorithm has a higher prediction accuracy and improved robustness. The demonstrated characteristics indicate that the proposed method may serve as a valuable tool in the framework of online TSA. [ABSTRACT FROM AUTHOR]

The proliferation of photovoltaics (PV) in distribution systems brings about voltage stability problems. This paper proposes an algorithm to calculate extreme bifurcation intervals considering deep PV penetration levels. The paper applies the sandglass-hyper-ellipsoid-cone model to analyze the correlations among net bus loads representing bidirectional power flows for different PV penetration levels. Using the net bus load model, three extreme bifurcation points on voltage stability limit hypersurface are formulated where two of these points represent the voltage stability bifurcation interval in the forecasted net bus loading direction. An iterative method is applied to obtain bifurcation solutions. The validity of the proposed method is verified by using the IEEE 3-bus system, the IEEE 33-bus system and the IEEE 123-node test feeder. The numerical results demonstrate that the proposed sandglass-hyper-ellipsoid-cone net bus load model and solutions are effective in managing correlated net bus load forecast errors in distribution systems with PV integration. [ABSTRACT FROM AUTHOR]

This paper proposes an algorithm for the bidirectional evaluation of voltage stability margin (VSM) with a large photovoltaic (PV) power penetration. To address the variability caused by loads and PV for bidirectional VSM, a deep ensemble model with a simultaneous point and probabilistic predictions is developed, which takes advantage of advanced metering infrastructure and weather data. The deep ensemble model consists of offline- and online-trained ensemble, which uses optimization blend and k-means, respectively. The proposed approach can also consider topology changes and environmental impacts (e.g., solar irradiance and temperature), with a major bearing on load/PV models and network parameters. The validity of the proposed approach is verified through its applications to a modified IEEE 33-bus system and IEEE 123-node test feeder, followed by VSM sensitivity analyses (Sen-ELM) and tolerance analyses with the consideration of input errors. The numerical results demonstrate that the proposed VSM approach has a strong generalization capability considering the proliferation of PV energy. [ABSTRACT FROM AUTHOR]

A decentralized control scheme based on backstepping design is proposed in this paper for the grid converters of a multi-terminal dc power integration system. With the proposed method, dc bus voltage can be accurately maintained together by several converters through appropriately adjusting their transmitted power according to the power sharing ratio. The system structure is presented and its dynamic model is formulated. The decentralized control laws of the grid converters are developed step by step by designing appropriate Lyapunov functions. The dc bus voltage control and the power sharing performance of the proposed control method are evaluated both under the system normal condition and converter fault condition. Finally, the effectiveness of the proposed scheme is validated through the real-time simulations on NI-PXI platform. [ABSTRACT FROM AUTHOR]

As a clean energy, wind power has been extensively exploited in the past few years. However, oscillations in wind turbines, particularly those from controllers, could severely affect the stability of power systems. Therefore, oscillation suppression is a recent research focus. Based on the small-signal model eigenvalues and participation factors, this paper detects the sub-synchronous interactions (SSI) mainly determined by converters’ PI parameters in a grid-connected doubly fed induction generator (DFIG). With the aim of oscillation restraint, a novel optimization model with the reference-point based non-dominated sorting genetic algorithm (NSGA-III) and the t-distributed stochastic neighbour embedding (t-SNE) is developed to explore and visualize optimal ranges of PI parameters, facilitating the selection of the appropriate PI parameters to augment the damping. Additionally, to study the adaptability of the optimal PI parameters, interactions performance of the system that uses optimal parameters is studied with different output levels of the wind turbine. Finally, a time domain simulation and a practical experiment are conducted to demonstrate the effectiveness of the proposed approach. Results illustrate that the SSI of a grid-connected DFIG is suppressed by the optimization model. This study is highly beneficial to power system operators in integrating wind power and maintaining system stability. [ABSTRACT FROM AUTHOR]

This study develops a system‐level dynamic phasor (DP) model of a hybrid AC/DC microgrid. A new definition of DP, based on the multiple frequency shift transformation, is proposed to extend the models of a variety of AC/DC and DC/DC converters. The comprehensive control system is considered in developing the DP model of microgrid. Furthermore, a computational framework for applying this DP model into system‐level simulation and small signal analysis (SSA) is given. The DP‐based simulation is tested under conditions of environmental disturbances and unbalanced supply voltages. The SSA is performed on the developed DP model to evaluate the voltage stability and harmonic modes of the microgrid. Besides, this DP model shows high potential when implemented in the real‐time simulation with larger scale system. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the evolution of the probability density function of the dynamic trajectories of a single machine infinite bus power system. The probability density function can be used to determine the impact of random (stochastic) load perturbations on system stability. The evolution of the state probability density function over time leads to several interesting observations regarding stability regions as a function of damping parameter. The Fokker-Planck equation (FPE) is used to describe the evolution of the probability density of the states. The FPE is solved numerically using PDE solvers (such as finite difference method). Based on the results, the qualitative changes of the stationary density produce peak-like, ridge-like and other complicated shapes. Lastly, the numerical FPE solution combined with SMIB equivalent techniques lay the framework extended to the multimachine system. [ABSTRACT FROM PUBLISHER]