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This paper summarizes the work done by the Task Force on Assessing the Need to Include Higher Order Terms for Small-Signal (Modal) Analysis. This Task Force was created by the Power System Dynamic Performance Committee to investigate the need to include higher order terms for small signal (modal) analysis. The focus of the work reported here is on establishing and documenting the practical significance of these terms in stability analysis using the method of Normal Forms. Special emphasis was placed on determining and describing conditions when higher order terms need to be included to accurately describe modal interactions. Test cases were developed on a standard test system to demonstrate the application of appropriate indices to detect the occurrence of nonlinear interaction and hence the need for higher order terms in stability analyzes. The use of the higher order terms in the site selection for a damping controller is also documented.

In second-order normal form (NF) analysis, the nonlinear dynamical system being analyzed is modeled with nonlinearities up to second order. Due to the presence of nonlinearities in the model, the results of second order NF analysis are initial condition dependent , . There are two assumptions in the theory of NF analysis and in this paper it has been shown that if the initial condition chosen do not satisfy these two main assumptions, then NF analysis is inaccurate. This paper also proposes three criteria to identify whether the initial condition satisfies one of the assumptions or not. This paper proposes to use a snap shot of state variables at an instant subsequent to the clearing of disturbance in situations where the state variables immediately after clearing the disturbance is not suitable for NF analysis. The time-domain simulations are presented to support the analysis.

A hysteresis model based on the Jiles-Atherton theory is incorporated into a power transformer model in an electromagnetic transient program (EMTP)-type program. The eddy current effects are also included in the same model. Comparisons are made between recorded and simulated waveforms using a single-phase distribution transformer. A good agreement is achieved between recorded and simulated data.

This paper proposes some methods for incorporating reactive power dispatch into nodal pricing and dispatch algorithms in pool-based electricity markets. The current approach of dispatching real power using a simplified power flow model and subsequently allocating reactive power as an ancillary service has the problem of getting suboptimal and some times infeasible solutions. However the complete a.c. power flow formulation can lead problems, due to non-convexity and resource limitations. This paper proposes an improvement to the standard decoupled linear formulation approach. In the proposed method real power is dispatched first and then reactive power is dispatched allowing small changes to real power dispatch. The results of case studies show that this method gives similar results to the full non-linear solution for real and reactive power dispatch and prices.

This paper deals with modelling induction motor loads for voltage stability analysis. A simple first order induction motor load model and a detailed third order induction motor load model suitable for this purpose are derived in terms of real power, reactive power and slip. It is shown analytically that the generic dynamic load models (GDLM) proposed in the literature, in their present form, are incapable of capturing induction motor characteristics. The generic dynamic load model is modified to capture the dynamics represented by the proposed induction motor load models. The appropriateness of the proposed dynamic load models in analysing the transient and steady state stabilities of induction motor loads are evaluated. It is shown that the first or third order induction motor models can be used for studying the power system voltage stability, with different degrees of accuracy.

This paper presents a case where the design of a Power System Stabilizer (PSS) to achieve desired damping using local speed feedback signals is difficult using the conventional design technique. It is shown that synchrophasor based two input power system stabilizer can be designed without much difficulty to achieve the desired damping. Eigenanalysis is performed on the reduced equivalent of New England New York power system. One controller location was found as the best location to improve damping of three inter-area modes. Residue analysis reveals the presence of a remote signal which has better sensitivity to the same controller location. The procedure of designing a two input PSS that uses a local signal and a remote signal is presented and it is shown that the required performance is achieved.

This paper discusses the real time digital simulation of a Static VAr Compensator (SVC) with fuzzy logic based supervisory control to damp the oscillations seen in the voltage after disturbances. The main controller is a traditional PI-controller and the auxiliary control path is made using fuzzy logic controller to provide the damping action. Therefore, the resultant is a non-linear controller, which performs better than the linear PI-controller. The controller performance is tested by connecting the SVC to a multi-machine power system, which is modeled in RSCAD software. The Real Time Digital Simulator (RTDS) is used to simulate the test system and the results are presented to show the improved performance of the proposed non-linear controller.

The paper presents a novel FACTS concept to improve the dynamic stability of an ac power system. The concept of parallel ac/dc transmission between two ac systems has been exploited in the scheme presented, using one ac line for both the ac and the dc transmission. A small unit of power is extracted from the system, converted to dc and injected into the ac line through the transformer, neutrals at the two ends to enhance the dynamic stability. The objective of the paper is to introduce the new concept and prove its feasibility. To demonstrate the validity of the proposed method, computer simulated dynamic responses of an ac power system, with and without the controlled dc injection are presented. It has been shown that by using about 2% of ac power transfer, as modulated dc power, substantial system of damping could be achieved.

The hysteresis loop of the core material in a test current transformer is simulated using the Jiles-Atherton theory. Comparisons are made between recorded and simulated waveforms and it is found necessary to replace the modified Langevin function used by Jiles and Atherton. Using an alternative function described in the paper, good agreement is achieved between test and simulated waveforms.

The application of the genetic algorithm to solve the optimal power dispatch problem for a multi-node auction market is proposed in this paper. The optimal power dispatch problem is a non-linear optimisation problem with several constraints. The objective of the proposed genetic algorithm is to maximise the total participants’ benefit at all nodes in the system. The proposed algorithm is simple to implement and can easily incorporate additional constraints. The algorithm was tested on a 17-node, 26-line system. The results have shown that the proposed algorithm yields good results that are consistent with typical market behaviour.

Design of a fuzzy logic controller needs qualitative knowledge about the system under consideration. This knowledge is usually obtained from experienced human controllers, or using analytical/heuristical techniques. However, with large/complex interconnected power systems, it is extremely difficult to obtain the necessary knowledge from human controllers or using conventional analytical/heuristical techniques. An approach to ascertain the relationships among variables to generate fuzzy rules is presented in this paper. The proposed method is based on system response to pulse input signals applied at appropriate instances. Use of this approach, along with sequential decentralised control design techniques for developing DC current and generator excitation modulation controllers to improve damping of oscillations in an AC-DC interconnected power systems, is presented in this paper. Simulation results reveal the successful application of the proposed rule base derivation approach along with sequential decentralised control techniques to design fuzzy logic modulation controllers for damping improvement of power systems.

This paper presents a fuzzy logic controller for improving the frequency regulation of the rectifier side AC system of an HVDC scheme interconnecting two power systems. The controller coordinates the modulation of, the current in the DC scheme and the generator excitation of the rectifier side AC system, in response to rectifier side AC system frequency deviation. The fuzzy logic controller is designed without using any precise system model. Only the qualitative knowledge about the system is used in designing the controller. An iterative technique using steepest descent gradient search method is proposed in this paper for further tuning of the output gains of the controller to optimise a chosen objective function. Simulation results reveal that, a fuzzy logic controller can be successfully implemented to realise significant improvements in frequency regulation by coordinating the modulation of the DC current and generator excitation of the rectifier side AC system.

This paper investigates the performance of a unified power flow controller (UPFC) constructed by a back to back connection of a hysteresis current forced (HCF) converter and a pulse width modulated (PWM) inverter. The UPFC has been modelled at the component level using PSCAD/EMTDC program and the simulation results of the UPFC applications in steady state power flow control and dynamic stability enhancement are demonstrated in a test system. The performance of the proposed switching schemes and associated controllers in providing the desired UPFC internal characteristics such as constant DC bus voltage and bi-directional power transfer capability is illustrated.

A comparison of frequency measurement methods for the purpose of underfrequency load shedding is presented in this paper. Comparison is made under the assumptions of the presence of DC offset, high order harmonics and noise in the measured signal. The major constraints have been the accuracy of frequency measurement, time needed to measure the frequency and complexity of implementation in terms of computational requirements. A method for efficient, low-cost implementation of frequency relay which can be used at domestic consumer installations is proposed and its implementation is described.

Lyapunov Exponents (LEs) measure the exponential rates of divergence or convergence of nearby trajectories in state-space models. The study presented in this paper investigates the applicability of this concept to power system transient stability analysis. It is shown that the Largest Lyapunov Exponent (LLE) of the post-fault system subsequent to a given fault scenario is independent of the fault clearing time up to the Critical Clearing Time (CCT). Furthermore, the set of exponentially stable equilibrium points of the post-fault system corresponding to different load-generation combinations of the pre-fault system can also be characterized by this LLE. The study compares the LEs with the conventional Time Domain Simulation (TDS), Extended Equal Area Criterion (EEAC) and Potential Energy Boundary Surface (PEBS) methods. It is shown that LEs give reliable results. Further, the power system stability regions can be determined using the invariance of LEs within the same stability region.

This paper describes the process that has been implemented for continual improvement of the Engineering programs at the University of Manitoba. The continuous improvement process developed is founded on: (i) assessment of graduate attributes, (ii) evaluation of student success, and (iii) further improvement of the programs. Graduate attributes are assessed both directly and indirectly. The direct assessment of attributes is through course-embedded procedures, while the indirect assessment is through compilation of many activities at both the Program, Department and Faculty levels, as well as via effective feedback from the students and the external engineering community. Together these assessments provide important information for the newly- established Curriculum Management Committee (CMC) to identify/prioritize needs, make recommendations and oversee the implementation of improvements. We describe steps taken to ensure a sustainable continuous program improvement process.

This paper presents and discusses the design and implementation of an open source Python programming framework for research and education in power system modeling and simulation. The framework, named the Power System Oscillations Analyzer (PSOA), focuses particularly on providing the basic requirements to encourage rapid development of custom models and simulation software. The framework includes a custom modeling API to create power system models in an intuitive manner and a fully functional GUI for interaction with model data and the framework. Test results are also provided that demonstrate the capabilities of the framework in the analysis of the one machine infinite bus system.

This paper proposes a novel method to estimate Control Performance Standard 1 (CPS1) using the probability distribution of area load change. The proposed method predicts an estimation of the CPS1 value for the future, which could be used in deciding operating strategies to achieve a target CPS1 value. NERC standards on frequency control performance define two indices known as Control Performance Standards 1 and 2 (CPS1 and CPS2). This paper focuses on CPS1, which is used to evaluate control area performance in normal interconnected power system operation. The most straightforward method of estimating CPS1 is to perform a time domain simulation provided that the area load forecast is available. However, if only the probability distribution of load change is available, then a random load curve must be generated to use in time domain simulation. This paper proposes a simple technique to estimate CPS1 directly from the probability distribution of load change without performing a time domain simulation which significantly reduces computing time. Hence predictive evaluation of CPS1 value is a novel concept which could be very useful in practice. A two-area test system is used to demonstrate the accuracy of the proposed method against the time domain simulation method.

This paper presents a software system that generates a database for power system dynamic security assessment. The generated database is intended to be used in machine learning techniques. The development of algorithms to generate data is a very time consuming task. This software tool is aimed at facilitating faster generation of the appropriate database. Further, the system allows the user to plug-in the case specific limit checks and algorithms for system specific corrective actions depending on the type of study. The proposed system automates the Power System Simulator for Engineering (PSSE) which is an industry standard software used in many electrical power utilities. The proposed software system, ML4DSA, is based on Python which is available in the public domain with plenty of supporting communities and powerful libraries. These features enable the user to develop algorithms for system specific corrective actions. The web interface facilitates access to the authenticated users of PSSE over the web, therefore, requires no additional software installed on the client computer. ML4DSA is successfully tested on the 39 Bus New England test system and the Midwest Reliability Organization (MRO) system which has over 50,000 buses.

A novel method for the design of power system damping controllers is proposed in this paper. The problem of selecting the controller parameters is formulated as a nonlinear optimization problem and the simulated annealing algorithm is used to solve it. By using this method, design criteria for all the controllers can be considered simultaneously. The proposed method can also be used to design controllers which are robust for a given set of operating conditions.

This paper studies the application of controlled series compensator (CSC) to damp power swings in multi-machine power systems. For the design of CSC damping controllers, a necessary step is the derivation of the linear state equation for the system. In order to consider the dynamics of the CSC, it is important to present the change in the CSC reactance as one of the state variables. In this case, unlike the traditional network representation, the network admittance matrix is no longer a constant matrix. Under this situation, the conventional linearization method for obtaining the linear state equation for the system must be modified. In this paper, a linear dynamic model for a multi-machine power system equipped with controlled series compensators (CSCs) is derived. Based on this linear dynamic model, a state feedback controller is designed for CSC control. The feedback control gains are obtained by using the pole placement technique. Given that CSCs are to be installed in a meshed system, the optimum location for installing CSCs is determined by analyzing the mode controllability. The effectiveness of this controller for damping the oscillations caused by power system disturbances is verified by simulation studies.

This paper demonstrates that wind farms connected to a grid through a series compensated transmission line may exhibit sub-synchronous oscillations. It is shown that the flux in the stator winding and the currents in the transmission line are the major participants of this mode. Dynamic Phasors are used to model the small signal model of the transmission network so that the network is accurately represented at sub-synchronous frequencies. An SVC is used to introduce damping to this oscillation mode, with line current as the feedback signal. The application is demonstrated for a large practical power system.

Professors, instructors and technical staff atvarious universities often face difficult questions regarding the tools and hands-on skills taught in the curriculum during a limited laboratory time. Therefore, to complement the classroom experience, students in Electrical and Computer Engineering at the University of Manitoba have developed and delivered a number of workshops on topics that have a direct impact in the classroom and job prospects, while encouraging independent learning and experimentation to foster lifelong learning skills. This paper describes the organization and examples from organizing more than 20 workshops that reached excess of 250 undergraduate students, graduate students, high school students, high school teachers, recent graduates, industry professionals, and hobbyist.

High wind power penetration levels result in additional requirements from wind power in order to improve frequency stability. Replacement of conventional power plants with wind power plants reduces the power system inertia due to the wind turbine technology. Consequently, the rate of change of frequency and the maximum frequency deviation increase after a disturbance such as generation loss, load increase, etc. Having no inherent inertial response, wind power plants need additional control concepts in order to provide an additional active power following a disturbance. Several control concepts have been implemented in the literature, but the assessment of these control concepts with respect to power system requirements has not been specified. In this paper, a methodology to assess the inertial response from wind power plants is proposed. Accordingly, the proposed methodology is applied to one of the inertial response control concepts from the literature.

This paper describes an interdepartmental initiative which aimed at launching the establishment of a shared laboratory facility to support teaching courses related to control, instrumentation and Mechatronics offered by various engineering departments at the University of Manitoba. The paper first outlines the rationale and need for this initiation. The approaches taken so far from upgrading the existing equipment and making them available at the faculty level to purchasing modern equipment are described. Future steps towards using the facility to encourage problem based learning and teaching innovations will also be described.

The paper first shows that the transient stability status of a power system following a large disturbance such as a fault can be early predicted based on the measured post-fault values of the generator voltages, speeds, or rotor angles. Synchronously sampled values provided by phasor measurement units (PMUs) of the generator voltages, frequencies, or rotor angles collected immediately after clearing a fault are used as inputs to a support vector machines (SVM) classifier which predicts the transient stability status. Studies with the New England 39-bus test system and the Venezuelan power network indicated that faster and more accurate predictions can be made by using the post-fault recovery voltage magnitude measurements as inputs. The accuracy and robustness of the transient stability prediction algorithm with the voltage magnitude measurements was extensively tested under both balanced and unbalanced fault conditions, as well as under different operating conditions, presence of measurement errors, voltage sensitive loads, and changes in the network topology. During the various tests carried out using the New England 39-bus test system, the proposed algorithm could always predict when the power system is approaching a transient instability with over 95% success rate.

The paper discusses the dynamic behaviour of two different Flexible AC Transmission System (FACTS) devices; the Interline Power Flow Controller (IPFC) and the Unified Power Flow Controller (UPFC) in a benchmark system. The small signal model of the Interline Power Flow Controller (IPFC) is developed and validated using detailed electromagnetic transients simulation. Using this validated model, the damping capabilities of the IPFC and the UPFC are compared and rationalized. From a small signal dynamics point of view, it is shown that the series branches of these devices essentially segment the network creating a new structure. This structure change may be used to effectively improve system damping without requiring the design of a tuned feedback controller. The IPFC's two series branches in contrast to the UPFC's single series branch permit more opportunities for network segmentation. Hence the IPFC has a greater potential for improving the systems dynamic performance.

The increasing penetration of modern wind plants may cause primary frequency regulation to fall below acceptable levels, especially in isolated grids. This paper investigates the contribution of variable speed wind generators to short-term frequency support. First, the extractable inertial power from a DFIG wind turbine is quantified. Based on that, a controller is designed to transiently release part of the stored kinetic energy in the rotating masses. This can be very helpful in the critical few seconds following a load-generation mismatch. Through time-domain simulations, performance of the proposed controller is examined against earlier implementations of inertial response. Results show that the proposed controller is effective in arresting the initial frequency dip and capable of bringing together the advantages of earlier implementations for better integration of wind generators.

A linearized model of an HVDC system is presented in a control block diagram form. The converter models (rectifier and inverter), DC transmission system, phase lock oscillators (PLOs) and the HVDC controllers are included. The control block diagram model of HVDC system simplifies, in understanding and modelling, the complex operation of the HVDC system. The model can be used in small signal stability assessment to analyze subsynchronous frequency HVDC interactions such as generator-turbine torsional interactions. Furthermore, the model can be easily implemented in a software environment such as Simulink for response analysis, control tuning and other educational purposes. (5 pages)

This paper presents a novel technique for predicting transient stability status of a power system following a large disturbance. The prediction is based on the synchronously measured samples of the fundamental frequency voltage magnitudes at each generation station. The voltage samples taken immediately after clearing the faults are input to a support vector machine classifier to identify the transient stability condition. The classifier is trained using examples of the post-fault recovery voltage measurements (inputs) and the corresponding stability status (output) determined using a power angle-based stability index. Studies with the New England 39-bus system indicate that the proposed algorithm can correctly recognize when the power system is approaching to the transient instability.

This paper presents a brief review of techniques available for reducing large systems to smaller equivalents. The paper is divided into High Frequency Equivalents, Low Frequency Equivalents, and Wide-band Equivalents.

This paper presents an analysis of multi-in-feed HVDC interactions using small signal analysis techniques. The modeling details necessary to adequately represent the dynamics of the HVDC converters and the AC network are investigated and the models are validated against an Electromagnetic Transient Simulation program. The paper shows that AC network dynamics must be modeled in order to obtain meaningful results from the small signal stability study. A small test system with two HVDC in-feeds is then used to demonstrate the presence of interactions in that system. The case studies presented in the paper indicate that it is possible to have interactions between the HVDC terminals in an AC system. The paper recommends that a small signal interaction study similar to what is presented in the paper should be performed to identify these interactions.

This paper introduces the use of regression analysis in the study of small signal stability in large interconnected power systems. Results demonstrate the usefulness of this approach in better understanding the nature of dominant electromechanical modes of oscillation and in accurately predicting the damping on these modes. The usefulness of this approach in identifying strong correlations between system damping and distinct measurable and adjustable power system quantities such as generator output, line flows, bus voltages and bus angles, is presented. Results suggest that this approach may be useful in optimizing the location of traditional power system on-line recording devices, such as Dynamic Swing Recorders (DSRs) as well as real time monitoring devices such as Phasor Measurement Units (PMUs). Sensitivity studies show that power system information obtained may be useful in providing an additional tool to help system operators optimize the dispatch of generating resources. It would also be useful in providing more realistic feedback from the power system and aid in the decision making regarding dynamic stability and its effect on appropriate system topology, loading levels and allowable transfer levels, in real time.

This paper investigates the simultaneous dispatch of real power and reactive power in restructured electricity markets. In this proposed method the opportunity cost of supplying reactive power is implicitly modeled using the rating of the machine as a constraint. Fairness of reactive power supplying obligation is also ensured in the proposed model by splitting the reactive power supplied by the generator into two components with the first component being proportional to real power dispatch. The model is evaluated using the IEEE 30 bus system.

Competitive electricity markets use marginal prices to settle the transactions with generator owners and consumers. This results in charging the consumers more than the average cost of production of electricity due to the nonlinear relationship between the losses and power transmission. This difference in revenue collection, referred to as the network rental in this paper, is further increased if the dispatch is constrained due to any operating limits such as power flow limits. There are two main components that constitute the network rental, loss rental and the constraint rental. This paper presents a theoretical analysis based on Karush-Kuhn-Tucker (KKT) optimality conditions to calculate these different rental components. In this way each rental component can be quantitatively analyzed, which in turn can be used to get a better insight of the operation of the electricity market. Some case studies on the IEEE 30 bus system is presented to demonstrate the application of the proposed method.

A power system is secure against a given contingency if it operates within acceptable operating limits before and after the occurrence of the contingency. In practice, it is not possible to secure a power system against all possible contingencies. Therefore, only the most critical contingencies (imminent disturbances) are considered. The paper gives an overview of power system security and different ways of loosing stability. Then, a statistical learning based technique for determining the boundary of the secure operating region in terms of pre-contingent state of the power system is reviewed. The paper discusses possible applications of the boundary and some issues related to practical application of this method.

A two-time step approach to transient stability modeling of detailed HVDC controls and L/R line dynamics is validated against a detailed electromagnetic transients model, and compared to the response-type HVDC model typically used in transient stability studies. The two-time step method combines the ability to include the detailed fast HVDC controls while still running the transient stability simulation of the large network at a 1/2 cycle time step, minimizing the impact to the overall computation time. To reduce complexity of the model, the detailed HVDC model assumes the AC commutating bus voltages to be unchanging during the internal fast time step loop of the HVDC link. Validation results show improved accuracy and numerical stability of the detailed HVDC transient stability model when compared to the typical response-type model, both in weak and strong test systems with effective short circuit ratios (ESCR) ranging from 2.0 to 5.0.

This paper proposes the inclusion of transient stability constraints in generation dispatch algorithms used in electricity markets to ensure dynamic security. The proposed security constraint is derived by applying a non-linear surface fitting technique to a database generated off-line. The technique used has two key features that enables the derivation of an accurate transient stability constraint with a relatively short computing time compared to other comparable methods. One feature is that it uses a linear estimation technique to estimate a non-linear function by means of a non-linear transformation. The second important feature is that it employs an implicit technique to gain significant reduction in computing burden. The potential of the proposed method is demonstrated using the New England 39 bus system and a larger power system with 470 buses. The security constraint derived for the New England 39 bus system is used in an optimal power flow (OPF) program for market clearance. The locational marginal prices (LMP) obtained from the OPF are further analyzed to determine the component of LMP due to dynamic security

This Paper presents a model which facilitates the allocation of spinning reserve in a power network which includes a large HVDC infeed. The basic area control model of the power system is developed and subsequently fine-tuned using a non-linear optimization procedure. The model is then used to evaluate the frequency control performance in the face of a known load forecast considering NERC performance standards.

This paper proposes the inclusion of transient stability constraints in generation dispatch algorithms used in electricity markets to ensure dynamic security. The proposed security constraint is derived by applying a non-linear surface fitting technique to a database generated off-line. The technique used has two key features that enables very fast computation of an accurate transient stability constraint. One feature is that it uses a linear estimation technique to estimate a non-linear function by means of a non-linear transformation. The second important feature is that it employs an implicit technique to gain significant reduction in computing burden. The security constraints derived for each credible contingency can be used in an optimal power flow program for market clearance. The effectiveness and efficiency of the proposed method is demonstrated using the New England 39 bus system and a larger power system with 470 buses.

In a restructured power system, locational marginal prices (LMP) are important pricing signals to the participants. LMP at a given node of a power system is the incremental cost of supplying power at that node. In a lossless system with no active constraints, the LMPs at all the nodes are equal. However, due to the losses in the power system, the LMPs at different nodes is different. Any operating constraint such as line flow limits also contribute to the LMP at a node. This paper investigates the effect of a dynamic security constraint on the LMPs. The transient stability margin expressed as a function of nodal voltages and phase angles, is used as a constraint in an optimal power flow (OPF) program to determine the LMPs at all the nodes of a power system. The Lagrange multiplier associated with the transient stability constraint gives the marginal cost of the transient stability constraint. A case study on the New England 39 bus system is presented to demonstrate the effect of the dynamic security constraint on the LMPs. In a nodal pricing scheme, any active constraint results in an additional revenue to the system operator. This revenue, known as the network rental, is also investigated in the paper.

Manitoba Hydro has dynamic swing recorders (DRSs) located on tie-lines between the Manitoba power system and neighbouring Canadian provinces, as well as the USA. These DSRs are triggered by major system contingencies and record post contingency data. This paper shows that off-line analysis of this data can provide useful information on the behaviour of dominant electromechanical modes of oscillation in the system which can be correlated to system loading and topology. Results obtained are compared to off-line eigenvalue analysis using available small signal analysis tools. Results suggest that with the development of suitable on-line measurement and analysis techniques, this information may be used to correlate system behaviour with particular events, provide useful information to help system operators regarding appropriate system topology, allowable transfer levels and in general provide more insight regarding the state of the system.

The work reported in this paper highlights differences and similarities between conventional linear analysis and the method of normal forms. The paper is focused on the effect that second order modal interactions have in the dynamic performance of a power system and identifies dynamic characteristics not captured by conventional linear analysis.

This work presents an efficient method to determine the transient stability boundary. In terms of the power system variables, the required boundary is nonlinear. The method adopted in This work is to transform the original power system variables into a higher dimensional feature space using a nonlinear transformation. It has been shown that well established linear estimation methods can be used in the feature space to determine a linear boundary. This linear boundary is equivalent to a nonlinear boundary in the original power system variable space.

This work describes the simulation of the effects of GIC (Geomagnetically Induced Currents) in a power system using a new transformer model. The simulation studies demonstrate that it is important to accurately model the remanence effects in the core of the power transformer.

In normal form (NF) analysis, the nonlinear dynamical system being analyzed is modeled with nonlinearities. If the second order NF is used in the analysis, the nonlinearities only up to second order are modeled. Due to the presence of nonlinearities in the model, the results of second order NF analysis is dependent in the initial conditions [C.-M. Lin et al., May 1996] [S. Zhu et al., November 2001]. If the state of the power system with respect to the stable equilibrium point (SEP), /spl Delta/X/spl Delta//sub 0/, at the instant of removal of the fault is used as an initial condition, then NF analysis may fail to give correct results. It is shown in this paper that the initial condition must be chosen such that the two main assumptions made in NF analysis are met. If the system being studied is stable, the post fault system will eventually reach the SEP. We propose to select an initial condition at an instant subsequent to clearing a fault, to achieve more reliable results from the NF analysis. The time domain simulations are presented to support the analysis.

This paper investigates the steady state operation of the interline power flow controller (IPFC). A mathematical model of the IPFC is presented and the model is used to investigate the flexibility of power flow control, in the presence of operating constraints of the IPFC. Some case studies are presented to illustrate the analysis and the possibility of using improved control strategies is discussed.

This paper describes the development of an electromagnetic transient model to represent the eddy current effects in transformer magnetising current. The magnetising current of a transformer is both nonlinear and frequency dependent. The frequency dependence is due to eddy currents. The most commonly used method to represent losses in a transformer model is to add a shunt resistance across one winding. In this paper we have extended a hysteresis model based on the Jiles Atherton theory of ferromagnetic hysteresis to include the effects of eddy currents. A comparison of simulation results and test results is presented in the paper.

This paper demonstrates how the simulated annealing algorithm and genetic algorithms can be used as means to solve the power system unit commitment problem. In addition, this paper presents parallel approaches to speed up the computational requirement of the simulated annealing algorithm. The algorithms were tested with two different problems. The results have demonstrated the success of the algorithms in consistently reaching good solutions.