Search

This paper presents a novel approach to dynamic phasor-based transient stability simulation. The proposed method is based on the modified nodal analysis (MNA) approach to circuit simulation, which is used to construct continuous differential-algebraic equations (DAEs). The proposed method makes use of the stamp technique, which makes it possible to construct a general purpose MNA-based simulator. Stamp-based models for common power system components are derived in this work. A new MNA-based synchronous machine model is presented, which represents machines as nonlinear inductances instead of subtransient equivalents. The resultant continuous DAEs are numerically solved using the general purpose variable step and variable order library \texttt{IDA}. Simulation results from the IEEE 68 bus test system, a real 400 bus power system, and the IEEE 39 bus test system with an embedded HVdc transmission system demonstrate that the proposed method is suitable for large ac networks with power electronic devices. The results demonstrate good agreement between the proposed method and electromagnetic transient (EMT) simulation. The results also demonstrate that the proposed method is fast and scalable with CPU times that are up to 200 times faster than EMT simulation.

The modular multilevel converter (MMC) has become a widely used topology for voltage source converter–based high‐voltage direct current transmission projects. To calculate the power operation region of an MMC directly and efficiently, we propose a novel steady‐state phasor model of the MMC. The model is expressed as an equivalent capacitance in series with a voltage source, where parameters are independent of alternating current (AC) electrical quantity. Based on the model, we propose an open‐loop approach to determine the operation region boundary of MMC by calculating the envelopes of the P–Q curves. The effect of MMC parameters, the circulating current control, and the short‐circuit ratio of the AC grid to the power operation region can be determined by the size and position of the power operation region. The proposed approach and analysis results were verified by an MMC/AC simulation model built in PSCAD/EMTDC.

Generation of electricity using renewable sources of energy will be the only option available to us soon. This may happen within the next two decades. In the meantime, we make the transition form traditional synchronous generator driven power systems to fully renewable energy-based power systems where the energy source is integrated through power electronics converters. We must start thinking in a new way. This presentation will address the technological challenges associated with connecting renewables to the grid through converters and the options available to meet those challenges. While the ability of the converters to respond fast is an obvious advantage, unlike the synchronous generator, it does not have a rotating mass that stores kinetic energy. The short-term overcurrent rating of the converter is much less than that of a synchronous generator unless the converter is overdesigned. Addressing these engineering challenges will be discussed in the presentation.

Stability analysis in the power system is becoming more important than ever as more distributed energy resources penetrate in the system. This study presents a novel load pattern voltage stability index (LPVSI) applicable to transmission and distribution systems. By considering the nominal value of voltages, the power network is converted into a two-bus equivalent system. Then, LPVSI is derived by only the real-time measurement of the voltage and deviation of active and reactive power loads. Also, the assessment of distributed generation's penetration level on unbalanced systems, with maximum loadability and power loss reduction constraints, is performed with regard to daily load variations. The accuracy and efficiency of the proposed indicator are tested on an unbalanced 34-node radial distribution system. Obtained results in comparison with some other papers in the literature demonstrate that the proposed voltage stability index is fast and effective in identifying non-trivial instabilities in the power system networks.

This paper utilizes modern statistical and machine learning methodology to predict the oscillation mode of interest in complex power engineering systems. The damping ratio of the electromechanical oscillation mode is formulated as a function of the power of the generators and loads as well as bus voltage magnitudes in the entire power system. The celebrated Lasso algorithm is implemented to solve this high-dimension modeling problem. By the nature of the L1 design, the Lasso algorithm can automatically render a sparse solution, and by eliminating redundant features, it provides desirable prediction power. The resultant model processes a simple structure, and it is easily interpretable. The precision of our sparse modeling framework is demonstrated in the context of an IEEE 50-Generator 145-Bus power network and an online learning framework for the power system oscillation mode prediction is also provided.

The basic concepts of transient rotor angle stability are presented in this chapter. The synchronous machine model with its auxiliary controllers and load models are discussed. The procedure to combine all dynamic models with the transmission network model to perform a dynamic simulation is presented. Although the modelling in this chapter is limited to the synchronous machine and loads, the algorithm of simulation is presented in a general manner to equip the reader with the understanding of how to expand the algorithm to include any dynamic device. A case study is used to demonstrate how to interpret the results of a simulation. The conventional modelling method presented in this chapter is not suitable to simulate faster transients introduced by power electronic devices in modern power systems. The chapter concludes with a short discussion on these limitations and new developments to resolve them.

This paper applies the statistical testing theory to examine the validity of different load parametric models. Traditionally measurement-based static load modeling has been performed based on a single parametric model. Commonly utilized models include: ZIP (constant-impedance–constant-current–constant-power) model, exponential model, and frequency component adjusted ZIP/exponential models. It has been conjectured that the models making use of the frequency feature should be better compared to the ones purely based on the voltage component. However, there has not been any theoretical-based justification to confirm this claim. It is a goal of this paper to provide a formal method for verifying this claim by employing the theory of statistical testing for correct parametric model specification. In particular, a class of F-tests for checking the correctness of the specific load model is employed. Our methodology is verified on the real phasor measurement unit (PMU) data describing a radial load in the Manitoba Hydro power system. The obtained results confirm the usefulness of the frequency component based models.

The absence of complete model data of a power system hinders complete eigenvalue analysis of that system. System identification methods have been used to identify operating-point-dependent equivalent linear model of a power system. Such identified models do not allow a complete eigenvalue analysis. To resolve this, the identification problem can be formulated in such a way to utilize any a-priori knowledge of the system. Model data of a synchronous machine consists of machine data and controller parameters. Methods to determine synchronous machine parameters are well established. In this paper, knowledge of the machine data and knowledge of eigenvalues of the system at multiple distinct operating points, extracted by a system identification method, are used to determine auxiliary controller parameters of the synchronous machine. Model data that are determined by the proposed method is independent of the operating point. Therefore, it can be easily integrated into a complete small signal stability study at any operating point of the synchronous machine.

More and more system operators are interested in calculating transfer capability in real time using real-time power flow models generated from the Energy Management System (EMS). However, in comparing these models with offline study models, the EMS models usually include only a limited portion of the interconnected system. It is not practical to extend the EMS model in order to capture the impact of the external systems and as such using an equivalent network becomes necessary for this purpose. Equivalent circuits derived from the offline models for certain predetermined operating conditions would suffer from invalid results under various real-time operating conditions. Hence, it is necessary to derive an equivalent circuit model that is adaptive to the real-time system conditions. This paper presents a general method of creating an equivalent circuit model based on the measured boundary station parameters such as voltages and power flows. Simulation studies show that such derived equivalent circuit models provide solutions with adequate accuracy.

This study presents a method to interface an electromagnetic transient (EMT) simulator with a dynamic phasor (DP) simulation program. The hybrid DP-EMT simulator offers flexibility in deciding the harmonic contents to be preserved in the DP domain; additionally, it offers significant reduction in computing time of large networks compared with EMT simulation. The proposed interfacing method is based on a generic transmission line, which uses specialised numerical techniques to transfer discretised waveform samples between the two simulators. These numerical methods produce the required mapping between EMT simulation samples and their counterpart DPs. This study describes the mathematical foundations of the DP-EMT interface and demonstrates them using an illustrative example. Several large networks are then studied to assess the interface's accuracy and performance in reducing computing time.

This paper presents a study on evaluating the power transfer capability of a novel hybrid cascaded modular multilevel voltage source converter topology. The configuration utilizes third harmonic injection to enable reactive power compensation by varying the ac side converter voltage in the presence of constant dc side voltage. The maximum converter voltage is determined by the number and rating of submodules and triplen harmonic compensation whereas the maximum allowable steady current through the converter determines its MVA rating. These constraints must be considered in determining the maximum power transfer capability of this converter configuration, connected to strong and weak ac buses. Further the reactive power required to be supplied by the converter under this condition is evaluated for these different system strengths. Results obtained from a developed ElectroMagnetic Transient (EMT) simulation model are presented in this paper, for validation of the theoretical calculations.

This paper presents a design of a power system damping controller using partial right eigenstructure assignment. The eigenstructure assignment technique selects a set of closed-loop eigenvalues along with their right or left eigenvectors. The selection of eigenvectors offers extra flexibility which is exploited in this paper by designing a robust damping controller which provides the required damping under multiple operating conditions. A multi-input controller is used to increase the degrees of freedom available for the design. Remote measurements available from synchronised phasor measurements are also considered. The problem is formulated as a multi-objective nonlinear optimization problem and solved using the nonlinear simplex function in MATLAB. The proposed technique is used to design a robust power system stabilizer for the interconnected New England New York simplified power system model. Four contingencies are selected as additional operating conditions. The designed controller is validated using a nonlinear simulation.

A screening method called the compensation impact factor (CIF) is proposed in this study to identify the risk of sub-synchronous resonance (SSR) caused when generators are connected to series compensated transmission lines. First, the definition of CIF is given and the meaning behind this index is explained. Second, the electric damping is used to classify the operating scenario into high SSR risk group and low SSR risk group. Then the correlation between the value of the CIF and the risk classification is analysed and the threshold value of CIF for this classification is calculated by using conditional probability. The proposed method is validated by (a) a 3-bus system with one generator and (b) the IEEE-39-bus system with ten generators. The advantage of applying the proposed method is that only the high-risk scenarios need to be analysed in detail using electromagnetic transient simulation.

This paper introduces a screening method to determine the potential risk of interactions between a dynamic device and a generator with torsional oscillations. The proposed method introduces a factor called the radiality factor (RF) which is an indicator of the radialness of the network between the device and the generator. The RF is calculated in the sub-synchronous frequency range and plotted against the frequency (RF curves). The RF curves can then be used for screening of torsional interactions between the generator and other dynamic devices. The critical value for the RF is determined through a large number of sensitivity studies on a test system. This method surpasses the available screening method: unit interaction factor (UIF) calculations which is only applicable for inductive networks without series compensated lines.

This paper proposes a robust frequency-domain method to tune the $d$ – $q$ decoupled control system used in Modular Multilevel Converter-type Voltage Source Converter (MMC-VSC) systems. A linearized state-space model of the MMC-VSC system is developed and used to calculate the stability-related frequency-domain attributes. The controller design problem is formulated as an optimization problem. In this paper, the simulated annealing optimization technique is applied to find the proportional-integral (PI) controller parameters that give desired damping for the oscillatory modes and desired values for decaying exponential modes. The efficacy of this method is tested on the electromagnetic transient model of a two-terminal MMC-VSC system on the real-time digital simulators, and the results are provided in this paper. Finally, tuned controller parameters for different ac system strengths are discussed and it is shown that this mathematical model is suitable to tune the PI-controller parameters for MMC-VSC systems connected to strong as well as weak ac networks.

This study presents a simple approach to modify the Prony algorithm to extract dominant low-frequency modes present in ring-down oscillations in power systems. The proposed approach is based on the observation that true modes present in the ring-down oscillations appear consistently, irrespective of the order of the Prony model. It is shown that the consistently appearing modes can be extracted using a sorting method. The improved Prony algorithm which has the feature of extracting only the true modes present in the input signal is utilised to propose an oscillation monitoring algorithm in this study. The suitability of the proposed oscillation monitoring algorithm for real-time monitoring of low-frequency inter-area oscillations is demonstrated using synthetic signals and simulated signals of different test systems.

This paper presents a linearized state-space model of the hybrid cascaded modular multilevel voltage source converter. The developed model is validated against a detailed non-linear Electromagnetic Transient (EMT) simulation model. The impact of the ac system strength on the performance of the converter is investigated for moderately strong and weak systems. An eigenvalue analysis is conducted for both scenarios, with focus on the oscillatory modes present in the system in order to evaluate the stability constraints of the converter when connected to ac networks of different strengths.

This paper presents a necessary stability criterion for interfacing a transient stability model to a dynamic phasor model. A voltage behind reactance type synchronous machine model, which is used in transient stability studies, is taken as the example case and it is interfaced with a dynamic phasor simulation as an external network. Dynamic phasors can be used in electromechanical-type simulations to extend the bandwidth of the simulation. In this paper a steady state stability analysis is done on the interface between the two models to determine whether the externally connected network is stable as a current injection device or a voltage injection device. The stability criterion is demonstrated using a dynamic simulation of a single machine connected to an infinite bus system.

Operation of VSC with weak AC systems creates challenges such as ensuring stability after disturbances and proper selection of controller parameters, need to be addressed before physical implementations. This paper investigates the effect of controller parameters on the stability of a modular multilevel converter (MMC) VSC system. It was observed that d-q controller gains have greater influence on the stability compared to phase-locked loops (PLL) gains. It is demonstrated using time-domain simulation results obtained on the real-time digital simulator (RTDS) that a set of properly tuned controller gains could ensure small and large transient stabilities of the MMC-VSC system. Moreover, the negative effect of measurement delays in instantaneous currents and voltages is analyzed by performing small-signal stability assessment. The paper concludes with useful guidelines on selecting controller parameters for an MMC-VSC system connected to weak AC networks.

Forced oscillations in a power system are distin-guished from natural oscillations as a rouge oscillatory input to the system. Two examples for sources of these forced oscillations are a malfunctioning governor that has not been modeled or a cyclic load with a low frequency. Power system oscillations are analyzed either by model based methods or by measurement based methods. Several recent papers have studied the impact of forced oscillations in estimating small signal stability of a power system using measurement based methods. When the frequency of the forced oscillation is in the vicinity of natural oscillations in the system, it has been reported that estimating natural and forced oscillatory modes is a challenge. This paper proposes utilizing model data to generate a database of oscillation signatures of the system for different forced oscillations of different frequencies at different origins and, aid measurement based oscillation monitoring methods to determine frequency and damping of natural oscillations and the source of forced oscillations, including at resonant conditions.

This paper presents a novel approach to enable frequent computational cycles in online dynamic security assessment by using the terms of the transient energy function (TEF) as input features to a machine learning algorithm. The aim is to train a single classifier that is capable of classifying stable and unstable operating points independent of the contingency. The network is trained based on the current system topology and the loading conditions. The potential of the proposed approach is demonstrated with the New England 39-bus test power system model using the support vector machine as the machine learning technique. It is shown that the classifier can be trained using a small set of data when the terms of the TEF are used as input features. The prediction accuracy of the proposed scheme was tested under the balanced and unbalanced faults with the presence of voltage sensitive and dynamic loads for different operating points.

In this paper, Power-Voltage Curves obtained from quasi steady state analysis is used to demonstrate the concept of voltage stability. This method is shown to be applicable to analyze the voltage stability when the load consists of constant admittance as well as dynamic induction motor loads. The results obtained from quasi steady state analysis is compared with the results of detailed real time simulations. As expected, the paper confirms that quasi steady state analysis can be used to predict the voltage collapse point of radial power systems with reasonable accuracy even when the loads consist of dynamic loads. The simulations and analysis programs developed in the research can be used as teaching tools.

Detection and analysis of bad data is an important sector of the static state estimation. This paper addresses single and multiple bad data in the modern phasor measurement unit (PMU)-based power system static state estimations. To accomplish this objective, available approaches in the PMU-based state estimation are overviewed, and their advantages and disadvantages are briefly explained. The largest normalized residual test is used to identify bad data. Then, phasor measurements are added by post-processing step in the state estimation. The proposed algorithms of phasor measurements utilization in state estimation can detect and identify single and multiple bad data in redundant and critical measurements. To validate simulations, IEEE 30 bus system are implemented in PowerFactory and Matlab is used to solve proposed state estimation using postprocessing of PMUs and mixed methods. Bad data is generated manually and added in PMU and conventional measurements profile. Finally, the location and analyze of bad data are available by the result of largest normalized residual test.

It has become a common practice of the manufacturers to provide only black-boxed models of devices to their buyers. These black-boxed models are compatible with time domain simulations. In this paper, a black-boxed EMT simulation model of a synchronous generator was connected to a known multi-machine power system, and an improved Prony Analysis method was used to identify the modes of the system from time domain simulations. The machine characteristics of the black-boxed model are assumed to be available to the user while the auxiliary controllers remain unknown. Then, an optimization-based eigenstructure assignment method is used to design a fictitious auxiliary controller for the black-boxed device, and a linearized power system model is realized. Eigenvalue analysis of the realized linear system provides insightful information of the system i.e. participation factors, mode shapes.

Power ramp limitation (PRL) is likely to become a requirement for large-scale photovoltaic power plants (LPVPPs) in order to allow the increase of PV penetration levels. Especially in islands with reduced inertia capability, this problem is more stringent: high-power ramp can be caused by either fast irradiance changes or other participant generators for example wind power, or loads. In order to compensate for the power mismatch, LPVPPs must use active power reserve (APR), by either curtailment or auxiliary storage. The paper proposes a PRL control structure for dynamic APR sizing and deployment. The selected test case is the power system of Puerto Rico (PREPA), modeled using the modified IEEE 12 bus benchmark system, with different levels of PV penetration. It is shown that LPVPP with PRL can effectively reduce the ramping rate of the participating generators. Considering that the large area of LPVPPs acts as a filter against fast irradiance changes, the study also reveals the required plant size for which an auxiliary storage is no longer needed in order to comply with PRL requirements—an important economical aspect.

Results of a nonlinear simulation is used in this paper to identify a linear model of a black-boxed synchronous machine. Linear system identification methods such as Prony Analysis, are employed to identify linear models of power system devices when their complete mathematical models are not available to be included in small signal stability studies. While the user lacks the knowledge of the control structure and its parameters, availability of the machine model is practically possible as the models and their parameter estimation methods are well established. Rapidly decaying transients of the machine, such as amortisseur winding transients, usually tend to be missed by available system identification methods. In this work an improved expanding-data-window Prony Analysis method is complemented with an eigenstructure assignment based method to incorporate a-priori knowledge of the generator to determine the highly damped transients of an electromagnetic transient (EMT) simulation model of a synchronous machine with generator controllers.

This paper investigates the impact of different control modes of VSC HVdc to the transient stability of power systems. VSC HVdc offers fast bi-directional power control in addition to fast ac voltage control. This feature is utilized in this study to enhance the transient stability of a conventional generator in a power system. Simulations are carried-out for three scenarios: (i) the generator is connected to the VSC terminal, (ii) the generator is connected at a distance from the VSC terminal, and (iii) the VSC is connected at a distance from the generator terminal. The critical fault clearing time is used as the indicator of the stability of power system. In each scenario, effects of both ac voltage control and reactive power control are studied. This paper shows that the transient stability of power system can be improved by having a VSC with fast ac voltage control near to synchronous generators.

Transient stability of an electrical power system refers to the ability of the system to settle at the stable equilibrium point in the post-fault system subsequent to a specific fault scenario. This stability problem can be studied either as a system stability or a structural stability problem. In this paper, the concept of Lyapunov Exponents (LEs) is used to analyze the transient stability of IEEE 3-generator 9-bus and IEEE 16 generator 69 bus benchmark systems. A spectrum of LEs is calculated from the mathematical models and the Largest Lyapunov Exponent (LLE) being negative implies the exponential stability of the post-fault power system. The system stability regions for specific fault scenarios are determined using the invariance property of the LEs from the initial conditions. Furthermore, the structural stability regions in terms of parameters of the pre-fault system dynamic equations are also determined. This study demonstrates that the concept of LEs can be used as a novel method to determine if the post-fault power system is within the stability region of attraction of the new stable equilibrium point, and hence to determine the stability region. It is also proposed that the largest average exponential rate calculated over a short time window is a sound approach for early prediction of the stability.

This paper utilizes a class of modern machine learning methods for estimating a transient stability boundary that is viewed as a function of power system variables. The simultaneous variable selection and estimation approach is employed yielding a substantially reduced complexity transient stability boundary model. The model is easily interpretable and yet possesses a stronger prediction power than techniques known in the power engineering literature so far. The accuracy of our methods is demonstrated using a 470-bus system.

Summary form only given. This paper presents a comprehensive analysis of sub-synchronous interactions in a wind integrated power system to understand and mitigate them. The proposed procedure has two steps. In the first step, a frequency scan is performed to determine the presence of resonant frequencies in the sub-synchronous range. In the second step, a detailed small signal analysis is performed. Participation factors are used to identify the state variables that are involved in the interaction, and the controllability indices are used to determine the mitigation method. It is shown that the sub-synchronous interaction present in Type 3 wind turbine-generators connected to the grid through series compensated lines is an electrical resonance between the generator and the series compensated line which is highly sensitive to the rotor side converter current controller gains.

This paper presents a probabilistic approach to evaluate the reliability of a synchrophasor-based multi-input damping controller. Considering the probabilities of losing input signals to the controller, expected damping for the critical electromechanical oscillatory modes are determined. A two input power system stabilizer that uses a local and a remote signal is considered as a test system to evaluate the expected damping. Different probabilities of failures are considered for different controller inputs and the resultant expected damping values are compared. The importance of using a probabilistic index in the design stage of a controller is highlighted.

Analysis of the impact of communication network infrastructure performance on critical power system applications that rely on wide area synchrophasor measurements can be realistically achieved only through co-simulation of the power system and the synchrophasor communication network. In this paper, a single simulation platform, an electromagnetic transient (EMT) simulation program - PSCAD/EMTDC, was used to implement the detailed models of the components in a wide area synchrophasor network. Using the developed components models, a simple wide area damping control application was co-simulated to demonstrate the impact of communication latency, packet losses, and bit flip errors on the controller performance. It was shown that with the aid of co-simulations, application specific issues can be diagnosed and appropriate solutions can be investigated.

This paper presents a brief review of techniques available for reducing large systems to smaller equivalents. This paper is divided into high frequency equivalents, low frequency equivalents, and wideband equivalents. Numerical examples are presented to demonstrate selected methods of high frequency equivalencing.

For the transient simulation of large power systems, it is sometimes necessary to represent a part of the network using electromagnetic transient models and the rest of the system using RMS fundamental frequency phasor models. The interface between the two parts of the network involves converting instantaneous three phase quantities into phasor quantities. One possible option for this conversion is to use a Phase Locked Loop with a positive sequence filter. This paper compares the performance of two types of positive sequence filters that can be used with Synchronous Reference Frame Phase Locked Loop (SRF PLL) to extract the angle information of a three phase unbalanced power system. This study focuses on two methods: (i) Sinusoidal Signal Integrator Phase Locked Loop (SSI-PLL); and (ii) the Extended Phase Locked Loop (Extended PLL). It is shown that the Extended PLL has better performance in speed and has zero steady state error compared to the SSI-PLL.

RSCAD® is an Electromagnetic Transient (EMT) simulation software of the RTDS real-time digital simulator. Currently, the software is able to carry out detailed nonlinear time-domain simulations only. Small signal stability analysis (eigenvalue analysis) of a power system cannot be performed on the software itself. Exporting data of a simulation case from RSCAD®, in order to perform eigenvalue analysis on a separate commercially available software, is also not trivial. The demonstration of extracting data of an RSCAD® simulation case, to perform eigenvalue analysis, is presented. The data is extracted from the files, generated by RSCAD, which the user has access to. Therefore the data extraction and eigenvalue analysis can be done by an external software module as presented. Incorporating the software module to RSCAD® as an internal function is proposed. The software module can perform eigenvalue analysis if all the power system models in the case are generic models, as is the case with commercially available software like SSAT®. Additionally, the proposed module can extract data of user-written linear controller models, and successfully incorporate them to the state space eigenvalue analysis. For full functionality of the module, all generic models should be linearized and included in the database. A common protocol is proposed for future expansion of the module. The extracted data is written into widely accepted file formats in the industry so that RSCAD® data can be exported for interoperability between different software.

Matrix Pencil (MP) and Hankel Total Least Squares (HTLS) algorithms approximate an input signal as a sum of decaying sinusoidal oscillations. This paper presents a simple technique to improve these algorithms for extracting only the true oscillations present in the input signal. The rationale behind the improvement is the observation that the true modes present in the input signal appear consistently irrespective of the order of the linear approximation used in MP and HTLS algorithms. It is shown that the modes appearing consistently can be extracted using a sorting method. The improved MP and HTLS algorithms presented in this paper are used for monitoring the low-frequency oscillations in power system in an online environment. The performances of the proposed algorithms are demonstrated using synthetic signals and simulated signals of different test systems.

This paper presents a linearized technique to determine a risk-based index for dynamic security. The method is an extension to an existing technique in which the risk of steady state security is calculated using the mean and variance of load uncertainty. The proposed method is applied to calculate the risk indices for the IEEE New England 39-bus test system. The results obtained from the proposed method are validated against those estimated by Monte Carlo simulation. Both approaches produce virtually the same results for small load deviations.

The paper discusses the dynamic behavior of two different flexible ac transmission system 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 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 IPFCs two series branches in contrast to the UPFC's single series branch permit more opportunities for network segmentation. Hence, the IPFC has greater potential for improving the system's dynamic performance.

In this paper, an artificial neural network (ANN) based method is developed for quickly estimating the long-term voltage stability margin. The investigation presented in the paper showed that node voltage magnitudes and the phase angles are the best predictors of voltage stability margin. Further, the paper shows that the proposed ANN based method can successfully estimate the voltage stability margin not only under normal operation but also under N-1 contingency situations. If the voltage magnitudes and phase angles are obtained in real-time from phasor measurement units (PMUs) using the proposed method, the voltage stability margin can be estimated in real time and used for initiating stability control actions. Finally, a suboptimal approach to determine the best locations for PMUs is presented. Numerical examples of the proposed techniques are presented using the New England 39-bus test system and a practical power system which consists of 1844 buses, 746 load buses, and 302 generator buses.

The paper applies the method of eigenstructure assignment for the design of a controller for a wind generation scenario in Northern Scotland based on doubly-fed induction generators (DFIGs). The designed controller serves the combined purpose of a conventional power system stabilizer (PSS) and an active damping controller and provides a contribution to both network and shaft damping. This novel approach is superior because all available degrees of freedom are fully exploited by selecting not only the new eigenvalue locations but also certain elements of the left eigenvectors. These elements are obtained by solving a multiobjective nonlinear optimization problem (MONLOP). Examples are presented to demonstrate that optimizing the eigenvectors yields a better performing controller in comparison with one designed using mere eigenvalue relocation.

This paper presents an analysis of multi infeed high-voltage dc (HVDC) interactions using small-signal analysis techniques. The modeling details that are 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 infeeds is then used to demonstrate the presence of interactions in that system. The case studies presented in this paper indicate that it is possible to have interactions between the HVDC terminals in an ac system. This paper recommends that a small-signal interaction study, which is similar to what is presented in this paper, should be performed to identify these interactions.

In the competitive electricity market, Locational Marginal Prices (LMPs) are important pricing signals for the participants as the effects of transmission losses and binding constraints are embedded in LMPs. While these LMPs provide valuable information at each location, they do not provide a detailed description in terms of contributing terms. The LMP components, on the other hand, show the explicit decomposition of LMP into contributing components, and thus, can be considered as better market signals. However, the effects of transmission losses cannot be explicitly seen from the LMP components. In this paper, the components of network rental is proposed to be used as a method in analyzing market signals, by decomposing the network rental into contributing components among the consumers. Since, the network rental is the surplus paid by all the consumers, components of network rental show how each consumer has actually overpaid due to losses and each binding constraint separately. A case study is also presented to demonstrate the potential of this proposed method in market signal analysis.

Transient rotor angle stability assessment and oscillatory rotor angle stability assessment subsequent to a contingency are integral components of dynamic security assessment (DSA) in power systems. This study proposes a hybrid algorithm to determine whether the post-fault power system is secure due to both transient rotor angle stability and oscillatory rotor angle stability subsequent to a set of known contingencies. The hybrid algorithm first uses a new security measure developed based on the concept of Lyapunov exponents (LEs) to determine the transient security of the post-fault power system. Later, the transient secure power swing curves are analysed using an improved Prony algorithm which extracts the dominant oscillatory modes and estimates their damping ratios. The damping ratio is a security measure about the oscillatory security of the post-fault power system subsequent to the contingency. The suitability of the proposed hybrid algorithm for DSA in power systems is illustrated using different contingencies of a 16-generator 68-bus test system and a 50-generator 470-bus test system. The accuracy of the stability conclusions and the acceptable computational burden indicate that the proposed hybrid algorithm is suitable for real-time security assessment with respect to both transient rotor angle stability and oscillatory rotor angle stability under multiple contingencies of the power system.

This paper presents an efficient method to estimate a transient stability boundary (TSB) as a nonlinear function of power system variables. The proposed method exploits the computational efficiency of linear estimation methods to determine an accurate nonlinear function. The novelty of the proposed method is that a nonlinear transformation is applied to the original variables, voltage magnitudes, and phase angles, so that the TSB is approximately linear in terms of the transformed variables. The linear function obtained using the transformed variables is indeed nonlinear in terms of original variables. The attractiveness of this method is that the estimated function is not a linearized approximation, although a linear estimation method is used. The potential of the proposed method is demonstrated using the New England 39-bus system and a larger power system with 470 buses

This paper presents a simulation algorithm to simulate the hysteresis characteristics in the core of a power transformer. The algorithm is based on the Jiles–Atherton phenomenological model of a ferromagnetic material. The new transformer model is capable of producing a close representation of the transformer magnetizing current. Comparisons are made between recorded and simulated waveforms using a single phase distribution transformer. A good agreement is achieved between recorded and simulated data.

The paper presents a platform system for the incorporation of flexible ac transmission systems (FACTS) devices. The platform permits detailed electromagnetic transients simulation as it is of manageable size. It manifests some of the common problems for which FACTS devices are used such as congestion management, stability improvement, and voltage support. The platform can be valuable for the validation of reduced order models such as small signal or transient stability models. The paper presents details on the development and validation of a small signal based model with the inclusion of a Unified Power Flow Controller. The validated model is then used successfully for the design of a feedback controller for improved damping.