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Interconnected power systems face different contingencies which may result in instability and blackouts. Therefore, online dynamic security analysis is becoming increasingly important. A suitable online stability index shows how close or far the system is from instability; as a result would deliver on-time alarms to system operators when the system is close to instability. This paper presents a practical and efficient method to calculate online dynamic stability index for power systems. The proposed approach does not need the model of the system and uses only the data from Phasor Measurements Units (PMU)s. İn this paper, first seven different dynamic Stability indices are defined and compared to each other under diffrenet types of contingencies. Some of the defined indices require only the voltage signal from different PMUs and others require the dominant roots of the system which can be estimated using Prony analysis method. The best criterion is selected based on the simulation results. The effectiveness of the proposed stability index is tested on a complete and accurate model of the Iranian power system. Simulation results revealed that the selected index can provide a good estimation of the distance to system collapse. [ABSTRACT FROM PUBLISHER]

An efficient approach to determine the voltage collapse point greatly assists planning and operation of power system, but most of existing methods are engaged with several power flow computations and they do not provide the optimal operating condition, which is the maximum loading point of a system without exceeding the power limits of generators. This paper introduces a novel approach by particle swarm optimization, which directly determines the voltage collapse point without successive power flow computations and furnishes the optimal operating condition as well. The proposed approach has been tested with a 6-bus test system and 182-bus power system of Sri Lanka as well as it is assessed for diverse applications of voltage stability analysis by concerning about single element outage and the role of static var compensators. Further, performance of the proposed approach is evaluated with continuation power flow method and the optimality is verified by eigenvalue analysis. [ABSTRACT FROM PUBLISHER]

In some markets the current trend of increasing wind power penetration may require the connection of Wind Power Plants to long transmission lines. Such long transmission lines can be series compensated in order to improve power system operation. Therefore, the immunity of wind turbines to Subsynchronous interaction should be considered in the planning phase of corresponding projects. The objective of this paper is to demonstrate the assessment of a commercial type IV Wind Turbine against Subsynchronous interaction. This assessment is performed in time domain using a detailed Electromagnetic model for the Wind Turbine as well as in frequency domain by performing the eigenvalue analysis. The results of the time domain simulations are used to confirm that the frequency domain approach is a valid assessment method. The results demonstrate that assessment of Subsynchronous interaction in frequency domain can be considered a valuable tool to power system operators for determining integration issues in an early stage of a project. [ABSTRACT FROM AUTHOR]

This paper presents small-disturbance stability studies of the interconnected power systems of the Sultanate of Oman and the State of the United Arab Emirates. The two systems are interconnected through the existing 220 kV double circuit transmission line between Oman and Abu Dhabi leading to a rather longitudinal structure power system. The objective of the paper is to assess the inter-area oscillation damping of this interconnected system during small amplitude disturbances by using eigenvalue analysis. A detailed model of the interconnected system is obtained including representation of generators, prime movers, speed governors, exciters, automatic voltage regulators, transmission lines, transformers, compensators and loads. The system eigenvalues are calculated at various operating scenarios, including peak and minimum loading conditions with zero and maximum power exchanges in both directions and also during N and N-1 conditions. The results have shown that both systems have adequate damping before being interconnected. After interconnection, the eigenvalues profile indicates that the system will remain stable and satisfactorily damped for the considered power exchanges. [ABSTRACT FROM PUBLISHER]

This paper presents a dynamic phasor modeling approach to the small signal transient analysis of induction machines with stator inter-turn faults. An important advantage of dynamic phasor modeling is that it results in time-invariant models of unbalanced three-phase systems. The linearized dynamic phasor model facilitates the analytical studies of transients of unbalanced systems using eigenvalues. The linearized q - d model of a machine with stator inter-turn fault has a system matrix having time periodic entries, and is thus unsuitable for eigenvalue analysis. The dynamic phasor model helps in this case. In this paper, the dynamic phasor model of induction machine with stator inter-turn fault is developed, and this is further used for eigenvalue analysis. The eigenvalue comparison of healthy and faulted machines is presented. This analysis is verified by transient simulations of the dynamic phasor model and experiments. The eigenvalue analysis and the results of experiments and simulations show that the effect of stator inter-turn fault in transients of positive and negative sequence currents is very small. Also the stator inter-turn fault produces coupling between transients of positive and negative sequence currents. [ABSTRACT FROM PUBLISHER]

Application of series capacitor in long transmission line is a cost effective method to increase power transfer. But presence of series capacitor has sometimes been limited because of the concern for subsynchronous resonance phenomenon in transmission line. SSR is basically an electrical power system condition where the electrical network exchanges energy with the turbine generator at one or more of the natural frequencies of the combined system below the synchronous frequency of the system. Presence of SSR torque causes oscillation which causes shaft fatigue and possible damage or failure of shaft. Long transmission line needs series or shunt compensation for power flow control as well as for mitigating the SSR phenomenon. An idea of this paper is to damp SSR by adding static synchronous series compensator (SSSC, Series device) or Static compensator (STATCOM, Shunt device). This paper shows that damping characteristics obtained by SSSC is better than STATCOM for damping SSR phenomenon. The results are obtained by modelling a lineralized system in MATLAB and study is performed on the system adapted from the IEEE first bench mark model for Eigen value analysis. [ABSTRACT FROM PUBLISHER]

In this paper a static synchronous series compensator (SSSC) is used to improve the small signal stability of a power system. A 48-step voltage source inverter (VSI) is used for the implementation of SSSC. The PI controller is used to regulate the dc link voltage of VSI. The mathematical model is derived for complete power system including PI and damping controller. The PI and damping controller parameters are selected through eigenvalue analysis. The results obtained from eigenvalue analysis are validated through nonlinear digital simulation using PSCAD/EMTDC. [ABSTRACT FROM PUBLISHER]

Transcendental terms appear in the characteristic equation of a power system and results in an infinite number of eigenvalues, when time delays in the feedback signals of power system wide-area damping controllers are considered. This makes it very difficult to obtain system eigenvalues via direct solution of the equation. In this paper, a method for computing a reduced set of eigenvalues of a time delay power system is proposed by using Padé rational polynomials to approximate the delays. The Padé polynomials are firstly transformed into their equivalent state space representations. By interconnecting the models of the open-loop power system, wide-area damping controllers and the state space representations of time delays, the linearized model for the closed-loop power system is then established and a reduced set of eignevalues of the system can be computed. The method has been tested on the New England 10-machine 39-bus test systems and compared with the eigenvalue computation method in the software package DDE-BIFTOOL. It shows that the proposed Padé approximation-based method can accurately obtain nearly all of the eigenvalues relating to system dynamic devices. The number of eigenvalues relating to time delays that can be correctly computed and their accuracy strongly relates to the orders of the Padé rational polynomials. [ABSTRACT FROM PUBLISHER]

As the penetration of wind power is high, in power system planning, it is difficult to acquire the detailed model of wind generators to be installed because of the commercial secrets. This paper discussed the mathematical models and typical control strategies of grid-connected double-fed wind generator (DFIG), and established the electromechanical simulation model with the help of power system simulation software DIgSILENT. Furthermore, two typical vector control methods applied in DFIG-stator flux oriented control and stator voltage oriented control were compared from two aspects which were eigenvalue and dynamic response. It can be concluded that when suffered a large disturbance, the proposed two vector control methods are quite different, and it is necessary to consider more detailed model in system stability analysis. On the contrary, when small disturbance is supposed, the results of two control methods are almost identical, which illustrates strong robustness and small deviation by applying general model. [ABSTRACT FROM PUBLISHER]

The main focus of this paper is to analyse IMDU characteristics to damp subsynchronous resonance. IMDU is coupled to T-G shaft. The advantage of using IMDU to damp SSR is that we need no other controller. The IEEE First Benchmark Model for subsynchronous studies is used to study eigenvalue analysis and time domain simulations. The time domain simulation study under large disturbances condition is carried out with IMDU located at the HP turbine end of T-G shaft. The coupling coefficient between IMDU and masses were varied, and its effects on SSR mitigation and transient stability were observed. The scheme enhances the system performance considerably and torsional oscillations are damped out at all levels of series compensation [ABSTRACT FROM PUBLISHER]

The structures of distribution systems are changing due to increasing penetration of distributed generations (DG units) as well as integration of advanced controllers and communication infrastructures. As a result, emerging distribution networks have a number of generators and controllers operating in a closer proximity. Such a proximity of dynamic devices results into modal interactions, which can deteriorate small signal stability of distribution systems. In such a case, a controller must be installed to ensure stability under different operating conditions. This paper presents a robust coordinated damping controller for distribution networks. The controller receives wide area control signal from network and sends supplementary control signals to the DG units. The advantage of the controller is that it can support small signal stability even if some DG units are out of operation. The effectiveness of the controller is tested in a 43-bus industrial distribution network. [ABSTRACT FROM PUBLISHER]

This paper presents the results of an eigenvalue and robustness analysis of a multi-DER islanded microgrid voltage control scheme. The configuration, parameters, and linear timeinvariant (LTI) state-space model of the microgrid are provided. The control strategy, control parameters, and the LTI state-space model of the closed-loop system are also given. An eigenvalue analysis is performed to investigate the dynamic behavior of the study system as microgrid electrical parameters and control gains change. A robustness analysis of the control strategy using the notion of real stability radius is carried out and results are presented. A PSCAD/EMTDC simulation case study is carried out to verify the results of eigenvalue/robustness analysis. [ABSTRACT FROM PUBLISHER]

As the most environmentally friendly source of power generation, wind power turbines is expanding in the grid. It will also have a broad and deep impact on power system stability. In this paper, a comparison of characteristics is made among three mainly used wind turbines currently which are constant speed wind turbine (CSWT), doubly fed induction generator (DFIG), direct drive synchronous generator (DDSG). Then a MATLAB-based Power System Analysis Toolbox PSAT is used for investigating the dynamic behavior of three generators in a strongly coupled two regional systems. Finally, a complicated two regional test system was introduced to analyze the small signal stability of different wind turbines when wind penetration power is increasing. [ABSTRACT FROM PUBLISHER]

In this paper, behavioural aspects of two types of power system stabilizers (PSS), i.e., a slip-signal PSS and a Delta-P-Omega PSS are studied in a fixed series capacitor compensated system employing the IEEE first benchmark system for SSR study. The well-known slip-signal-torsional interaction is studied to understand its dependency on the magnitude of network compensation. From such a study it is noted that the slip-signal-interaction is prominent only at higher degree of line compensation. It is also shown that Delta-P-Omega PSS is immune to such torsional interactions. Further, using the eigenvalue-based study, the swing-mode damping performance of slip-signal PSS and Delta-P-Omega PSS are studied when a system is series compensated. This study not only demonstrated the superiority of Delta-P-Omega PSS, but also validated the poor performance of slip-signal PSS. All these observations are verified by carrying out simulations on PSCAD/EMTDC. To enhance the understanding about the SSR phenomenon, some fundamental observations made in the study are also listed. [ABSTRACT FROM PUBLISHER]

The purpose of this paper is to investigate the characteristics of the switching caused by the microgrid transitions based on the eigenvalue analysis. The factors, including control parameters, line parameters and load parameters, which have impact on the eigenvalues of the two operation modes of the microgrid are studied. In addition, the parameter sensitivity analysis for the dominant eigenvalues is carried out under different load levels in two operation modes of microgrid. The results show: the line parameters and the load parameters have less impact on the stability of the microgrid system than control parameters in either the grid-connected mode or islanded mode; the parameter sensitivity of kpi, the proportional parameter of inner-loop current controller, for the dominant eigenvalue is increased after the microgrid switches from grid-connected mode to autonomous mode. This may cause the microgrid instable in the autonomous mode even if transition from a stable grid-connected mode. Therefore, the parameter kpi should be adjusted to a suitable value to maintain the microgrid stable during the switching, once the island state of microgrid is detected. By comparing the change of the eigenvalues distribution in the modes switching of micro-grid, some smooth-switching control strategies are proposed. Finally several time-domain simulations are present to verify the above result. [ABSTRACT FROM PUBLISHER]

This paper presents a comprehensive simulation study to show the adequacy of two solar farm models for small signal stability analysis. Simulation study is carried out by considering solar farm as single-and multi -generator equivalents for both models. The simulation results are presented for a small interconnected system by considering different short circuit ratios (SCR). Both Solar farm models, single-generator and multiple-generator equivalents provide the same results for small signal stability studies for different scenarios. [ABSTRACT FROM PUBLISHER]