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This paper investigates the effect of modelling of different aspects of wind farms (WF) as a first step towards development of the equivalent harmonic model initially of WF, and later of other types of converter connected generation, for studies of harmonic propagation and mitigation in power electronics (PE) rich transmission networks. The aim of the study was to establish a set of scaling factors that can be used when modelling the entire WF as a single probabilistic harmonic generator in harmonic propagation studies, considering different WF configurations, weather conditions, harmonic cancellation effects, individual wind generator availability, cable disconnection, and the influence of the non-ideal external grid. The importance of modelling resonance and individual characteristic harmonics on the equivalent modelling of WF has also been established. The results facilitate the assessment of global contribution of PE connected RES to harmonic levels in transmission networks and more generally harmonic propagation studies in large PE rich transmission networks. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of ‘quickest possible’ online transient stability assessment, by minimizing the decision time of combined event detection that might lead to a system split and unstable generator group prediction, from real-time wide area power system measurements. More importantly it does so by respecting predefined probabilistic error constraints for the prediction. The statistical theory of optimal detection is applied, firstly to choose the detection threshold and secondly to select a flexible assessment time, after using probabilistic neural networks to provide a temporal representation of the data. On simulated wide area measurements from the interconnected New England test system and New York power system this approach is between two and three times faster on average than strategies based on fixed assessment times, despite having comparable error rates. [ABSTRACT FROM AUTHOR]

This paper proposes a method for the optimal deployment of Corrective Control Measures (CCMs) for the improvement of transient stability in uncertain power systems. First, the critical oscillation patterns of the disturbed system are identified using Hierarchical Clustering (HC) with statistically defined algorithm parameters. This is followed by the identification of critical generators where the application of CCMs will have maximum impact. The results show that a significant reduction in multi-machine unstable events can be achieved by the strategic deployment of CCMs. The proposed method is demonstrated on a modified IEEE 68 bus NETS-NYPS test network with Renewable Energy Sources (RES) and realistically modelled system uncertainties. [ABSTRACT FROM AUTHOR]

This paper proposes a methodology for advanced demand side management (DSM) in the distribution network (DN), catering at the same time for the requirements of the network operator, transmission or distribution, the available flexibility of the demand side, and the preservation of network performance. The basic premise of the study is that the distribution network operator is providing flexibility to the transmission system operator through load shaping. Different, one or more, indicators can be chosen to assess preservation of network performance. In this paper, for illustrative purposes of the methodology, the steady state voltage stability index, namely the load margin, is chosen as the network performance indicator. This is evaluated before and after a DSM action, in order to analyse the possible effect of DSM on network loadability. Load at each DN bus is represented using a realistic composite load model comprising controllable and uncontrollable loads. The DSM is initially performed based on optimal power flow calculation to ensure that the distribution system load profile at the grid supply point follows the required (pre-specified) load profile during a 24 hour period. Following this, a particle swarm optimisation is used to modify DSM program in those time steps of the planning horizon where load margin is reduced. The methodology is illustrated on a number of case studies using modified IEEE 33 bus distribution network model. The results illustrate the extent to which the available flexibility of demand can be used in support of transmission network operation when the preservation of network performance and appropriate load modeling are considered. [ABSTRACT FROM AUTHOR]

This paper introduces a two-step methodology for online identification of the participation of generators in power system oscillatory modes, based on measured responses. The dominant modes in generator measured responses are initially identified using a mode identification technique and then introduced, in the next step, as input into a clustering algorithm. Critical groups of generators that exhibit poorly or negatively damped oscillations are identified, in order to enable corrective control actions and stabilize the system. The uncertainties associated with the operation of modern power systems with renewable energy sources (RESs) are investigated as well as the impact of the dynamic behavior of power electronic interfaced RESs. [ABSTRACT FROM AUTHOR]

The paper introduces a probabilistic framework for online identification of post fault dynamic behavior of power systems with renewable generation. The framework is based on decision trees and hierarchical clustering and incorporates uncertainties associated with network operating conditions, topology changes, faults, and renewable generation. In addition to identifying unstable generator groups, the developed clustering methodology also facilitates identification of the sequence in which the groups lose synchronism. The framework is illustrated on a modified version of the IEEE 68 bus test network incorporating significant portion of renewable generation. [ABSTRACT FROM PUBLISHER]

This paper introduces a probabilistic framework for transient stability assessment (TSA) of power systems with high penetration of renewable generation. The critical generators and areas of the system are identified using a method based on hierarchical clustering. Furthermore, statistical analysis of several transient stability indices is performed to assess their suitability for TSA of reduced inertia systems. The proposed framework facilitates robust assessment of transient stability of uncertain power systems with reduced inertia. [ABSTRACT FROM AUTHOR]

This paper proposes a two-stage methodology for online identification of power system dynamic signature using phasor measurement unit (PMU) measurements and data mining. Only transient stability status is usually predicted in the literature to assist with corrective control, without the dynamic behavior of generators in the event of instability. This paper uses traditional binary classification to identify transient stability in the first stage, and then develops a novel methodology to predict the nature of unstable dynamic behavior in the second stage. The method firstly applies hierarchical clustering to define patterns of unstable dynamic behavior of generators, and then applies different multiclass classification techniques, including decision tree, ensemble decision tree and multiclass support vector machine to identify characterized unstable responses. The proposed methodology is demonstrated on a multi-area transmission test system. High prediction accuracy at both stages of identification is demonstrated. [ABSTRACT FROM AUTHOR]

The paper proposes a framework for the selection of optimal configuration of line compensation devices, thyristor controlled series capacitors (TCSC) and conventional fixed series capacitors, for reducing the risk of subsynchronous resonance (SSR) in the network while maintaining required power transfer. The methodology developed in the paper is based on the robust risk evaluation of SSR that takes into consideration the severity of subsynchronous resonance and probability of its occurrence. The subsynchronous resonance risk index developed previously is used to assess the severity of subsynchronous resonance. The line outage model is employed to determine the probability of contingencies potentially leading to subsynchronous resonance. It is demonstrated that with relatively small participation of TCSC, even with the most basic control, in series compensation of lines, the risk of SSR can be successfully managed. [ABSTRACT FROM PUBLISHER]

This paper presents details of the practical implementation of a coordinated reactive power–voltage controller (CQVC) developed for a multi-machine steam power plant. The CQVC performs optimal coordination of the synchronous generators' reactive power outputs in order to maintain the total reactive power delivered by a steam power plant (SPP) or the voltage at a steam power plant HV busbar. This is required to achieve slow preventive control of generated reactive powers in order to maximize reactive power reserves along with slow high side voltage control. The CQVC is designed to act through existing automatic voltage regulator inputs, thus no modification of an existing excitation system was made. In order to increase the robustness to changes in operating conditions and to achieve the desired shape of the reactive power response, the two-step predictor corrector method is implemented. A newly developed algorithm for steady state detection ensures non-interference of reactive power voltage control with excitation system response. The paper also presents practical design solutions to overcome limitations posed by application to a real system. Acceptance and functional tests carried out during the commissioning of the CQVC are also discussed in this paper. [ABSTRACT FROM AUTHOR]

This paper proposes a methodology for evaluation of risk of subsynchronous resonance (SSR) in meshed compensated AC networks. The developed methodology takes into account the severity of SSR problem in different network configurations caused by fixed series compensation and probabilistic behavior of the power systems due to random outages of the lines. SSR risk evaluation considers severity of SSR problem, probabilities of different network configurations for different contingencies and different operating conditions of turbine generator. Probability of each contingency is determined through line outage model while the probabilities of different operating conditions are calculated from multilevel load duration curve. Using developed risk matrix, it is demonstrated that the degree of risk of SSR that the generators in the network are exposed to can be evaluated for different network configurations, different contingencies and different line compensation levels. [ABSTRACT FROM AUTHOR]

This paper presents the development of the dynamic equivalent model of an active distributed network (ADN) based on the grey-box approach. The equivalent model of an ADN comprises a converter-connected generator and a composite load model in parallel. The grey-box approach was chosen for model development as it incorporates prior knowledge about the ADN structure into the model, makes the model more physically relevant and intuitive than black-box or white-box models, and potentially improves the accuracy of the model. The dynamic equivalent model is presented in the seventh-order nonlinear state space format. It was initially loosely developed from the algebraic and differential equations describing assumed typical components of an ADN. Various static load models, dynamic load compositions, fault locations and a diverse range of distributed generation types and scenarios are considered in order to establish the generic range of model parameters for an ADN. The model is intended for the use in large power system stability studies. [ABSTRACT FROM PUBLISHER]

Paper presents an equivalent model of an active distribution network cell (ADNC) with distributed generation for transmission system stability studies. The equivalent model of ADNC comprises a converter-connected generator and a composite load model in parallel. The gray-box approach was chosen as it enables inclusion of prior knowledge about the ADNC structure into the model development, hence making the model more physically relevant and intuitive than a black-box or white-box model. The dynamic equivalent model is presented in a seventh-order nonlinear quasi state space format, developed from the algebraic and differential equations describing assumed typical components of the ADNC. The developed equivalent model of ADNC was validated through small and large disturbance studies using the modified IEEE nine-bus transmission system model. [ABSTRACT FROM PUBLISHER]

This paper presents commissioning details of a coordinated reactive power–voltage controller (CQVC) installed in a multimachine steam power plant (SPP). The CQVC regulates reactive power and voltage of a 1992MVA multimachine SPP. After briefly introducing basic control principles and relevant details about the CQVC's implementation, CQVC parameterization and tuning are thoroughly discussed. Once commissioned,the CQVC performance under various operating conditions is assessed. It is shown that the CQVC successfully maintains an HV busbar voltage and allocates reactive power to participating generators in accordance to their capability. Numerous CQVC responses recorded at the site are presented to demonstrate controller's performance under normal and extreme plant and network operating conditions. [ABSTRACT FROM PUBLISHER]

The paper proposes a new methodology for ranking synchronous generators in a power system according to their contribution to angular and voltage stability. The method is based on sensitivity analysis of electromechanical modes and takes into account the location of generators, their inertia, active and reactive power outputs, and control functions. Though uses of such a ranking may vary, its application in large-scale wind power integration is presented in this study. The Generator Ranking Index (GRI) was able to identify the group of generators which are most suitable for manipulation in order to make way for new energy source, e.g., wind generators that do not provide similar support to the system. [ABSTRACT FROM PUBLISHER]

The paper presents the digital realization of a model of reactive power flow (QFM) in a steam power plant using a programmable logic controller (PLC). The steam power plant (SPP) model is developed for pre-commissioning validation testing of the coordinated reactive power-terminal voltage (Q-V) control system. The SPP QFM includes a model for a synchronous generator, an excitation system, a step-up transformer, and the generator's droop characteristic modeled through the automatic voltage regulator (AVR). A QFM synthesis is based on a series of experiments performed on site. The parameters of the generator and AVR are estimated from recorded generator voltage and current time responses to a step change in voltage reference of the AVR. To get a complete QFM, transformers and network reactances are also included. In order to calculate reactive power (Q) flows more accurately, the generator Q output is adjusted by taking into account its real power output. Standard PLC hardware, as industrial grade equipment appropriate for on site testing, is used for practical QFM implementation after discretization of the continuous mathematical model. The developed QFM response is verified through a series of experiments performed in the laboratory. [ABSTRACT FROM PUBLISHER]