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This paper presents an adaptive wide-area control strategy based on energy function. The proposed method enhances the post-fault oscillation damping capability of Static Var Compensators (SVC) by incorporating load dynamics in the wide-area controller design that adapts to load variations. The load dynamics are obtained using Phasor Measurement Units (PMU) through load power and voltage data measurements, which are used to estimate a Moving Average (MA) dynamic load model. The obtained load model is then integrated into the wide-area controller to obtain the required SVC supplementary control action which modulates the load power in response to a disturbance based on inter-area dynamics obtained by employing a nonlinear Kalman filter and PMU measurements. The performance of the proposed strategy is evaluated on the simplified 14 generator model of the southeast Australian power system by using composite load models comprised of induction motor loads of various sizes and combinations. The obtained results show significant improvements in the system stability when the proposed control strategy is applied.

Electrical power systems continue to grow in size and complexity, resulting in new challenges to control and stabilize them. Measurement based Wide-Area Control Systems (WACS) have been extensively researched in the last decade to enhance power system stability. However, very few WACS implementations in the field have been carried out so far. To bridge this gap the LabVIEW package, Audur, presented in this paper, allows users to easily implement their custom WACS design on a National Instruments hardware platform. The hardware controller receives synchrophasor measurements compliant with the IEEE C37.118.2 protocol and generates a control signal that, in principle, can be configured as a supplementary control system to drive any active component in the power system., QC 20181106

Power systems are extremely non-linear systems which require substantial modeling and control efforts to run continuously. The movement of the power system in parameter and state space is often not well understood, thus making it difficult or impossible to determine whether the system is nearing instability. This dissertation demonstrates several ways in which the power system stability boundary can be calculated. The power system movements evaluated here address the effects of inter-area oscillations on the system which occur in the seconds to minutes time period. The first uses gain scheduling techniques through creation of a set of linear parameter varying (LPV) systems for many operating points of the non-linear system. In the case presented, load and line reactance are used as parameters. The scheduling variables are the power flows in tie lines of the system due to the useful information they provide about the power system state in addition to being available for measurement. A linear controller is developed for the LPV model using H₂/H∞ with pole placement objectives. When the control is applied to the non-linear system, the proposed algorithm predicts the response of the non-linear system to the control by determining if the current system state is located within the domain of attraction of the equilibrium. If the stability domain contains a convex combination of the two points, the control will aid the system in moving towards the equilibrium. The second contribution of this thesis is through the development and implementation of a pseudo non-linear evaluation of a power system as it moves through state space. A system linearization occurs first to compute a multi-objective state space controller. For each contingency definition, many variations of the power system example are created and assigned to the particular contingency class. The powerflow variations and contingency controls are combined to run sets of time series analysis in which the Lyapunov func

Power systems are extremely non-linear systems which require substantial modeling and control efforts to run continuously. The movement of the power system in parameter and state space is often not well understood, thus making it difficult or impossible to determine whether the system is nearing instability. This dissertation demonstrates several ways in which the power system stability boundary can be calculated. The power system movements evaluated here address the effects of inter-area oscillations on the system which occur in the seconds to minutes time period. The first uses gain scheduling techniques through creation of a set of linear parameter varying (LPV) systems for many operating points of the non-linear system. In the case presented, load and line reactance are used as parameters. The scheduling variables are the power flows in tie lines of the system due to the useful information they provide about the power system state in addition to being available for measurement. A linear controller is developed for the LPV model using H₂/H∞ with pole placement objectives. When the control is applied to the non-linear system, the proposed algorithm predicts the response of the non-linear system to the control by determining if the current system state is located within the domain of attraction of the equilibrium. If the stability domain contains a convex combination of the two points, the control will aid the system in moving towards the equilibrium. The second contribution of this thesis is through the development and implementation of a pseudo non-linear evaluation of a power system as it moves through state space. A system linearization occurs first to compute a multi-objective state space controller. For each contingency definition, many variations of the power system example are created and assigned to the particular contingency class. The powerflow variations and contingency controls are combined to run sets of time series analysis in which the Lyapunov func

This thesis proposes a new wide-area controller for enhancing the stability of power systems by damping inter-area oscillations. The obtained controller is a new nonlinear controller that accomplishes the task by using data from PMUs employed throughout the network. The controller improves the damping of inter-area oscillations by providing a supplementary control input for several controllable devices such as excitation systems of synchronous generators and Static Var Compensators. The novel nonlinear inverse filtering controller is developed and investigated in different network configurations in the thesis.

This paper presents an overview of the software implementation of a real-time mode estimator application and its testing. The application was developed to estimate inter-area modes from both ambient and ring-down synchrophasor data from multiple phasor measurement units (PMU). The software application was implemented in LabVIEW using Statnett’s synchrophasor software development kit (S3DK), to receive real-time synchrophasor measurements. The different features of the application were tested using two types of experiments presented herein. The first experiment is performed using emulated signals from a simple linear model. The second experiment was designed to use a linearized representation of the KTH-Nordic32 power system model. These experiments are used to carry out quantitative analyses of the tool’s performance., QC 20170119

This thesis proposes a new wide-area controller for enhancing the stability of power systems by damping inter-area oscillations. The obtained controller is a new nonlinear controller that accomplishes the task by using data from PMUs employed throughout the network. The controller improves the damping of inter-area oscillations by providing a supplementary control input for several controllable devices such as excitation systems of synchronous generators and Static Var Compensators. The novel nonlinear inverse filtering controller is developed and investigated in different network configurations in the thesis.

This article presents a comprehensive study of dominant inter-area oscillation path signals and their application for power system wide-area damping control (WADC). The analysis, carried out on both small and large study systems, focuses on the relationships that emerge from physical characteristics of inter-area oscillations, namely the modal observability of signals from dominant paths and their corresponding control loop system properties (i.e. stability and robustness). The aim is to be able to appropriately exploit the dominant path signals for the mitigation of inter-area oscillations. Guidelines and considerations are provided to facilitate the design of WADC using the proposed approach., QC 20160210

Spectral analysis techniques have successfully been applied for near real-time monitoring of power system small-signal electromechanical oscillations using synchronized phasor data from PMUs. The methods used for this purpose commonly assume that random load variations adopt the distribution function of Gaussian noise. Hence, careful attention has to be paid so that the preprocessing of synchronized phasor measurements is capable of providing data with the characteristics expected for these methods to work properly. This can be viewed as a conditioning step in the data handling process that has an impact on the results from spectral analysis which consume this data. This article aims to revisit the crucial step of preprocessing of PMU data in a tutorial fashion. The goal is to share the authors' experience when dealing with real PMU data originating from the Nordic Grid. This article offers a systematic and detailed methodology developed by the authors which has been successfully used in studies on estimation of electromechanical modes in the Nordic Grid., QC 20150303

The presence of inter-area oscillations has long affected stability constraints, and therefore, limited the power transfer capacity of interconnected power systems. Adequate damping of these inter-area oscillations is, thus, necessary to secure system operation and ensure system reliability while increasing power transfers. Power system stabilizers (PSS) are the most common devices used to enhance the damping of such oscillations. Many studies have demonstrated that PSSs using remote signals may perform better than using local signals. The advent of phasor measurement units (PMU) makes remote or wide-area signals become available, which enables various important applications. Of particular interest is wide-area damping control (WADC), which aims to utilize remote or wide-area measurements to damp the inter-area oscillations. However, two main challenges in WADC design are (1) feedback controller input signal selection (which PMU signal is best to use?), and (2) latency (which is inherent in the transmission of the measurements) considerations. In response to the first challenge, this thesis proposes a concept called dominant inter-area oscillation path, which serves to pinpoint a set of candidate signals that can be used as the feedback controller inputs by locating the interconnected corridors where the inter-area modal contents are the most observable. Derivation, identification, and use of the dominant inter-area oscillation paths are demonstrated throughout the thesis. Extensive analysis on the relationships between the proposed set of signals and system properties regarding stability and robustness is presented. To tackle the second challenge, the impacts of time delays on the system performance when using the dominant path signals are investigated. To date, several studies have proposed different control design methods using various oscillation dampers to design WADC. Nevertheless, neither a systematic method nor a concept that encompasses fundamental knowledg, QC 20150414

The presence of inter-area oscillations has long affected stability constraints, and therefore, limited the power transfer capacity of interconnected power systems. Adequate damping of these inter-area oscillations is, thus, necessary to secure system operation and ensure system reliability while increasing power transfers. Power system stabilizers (PSS) are the most common devices used to enhance the damping of such oscillations. Many studies have demonstrated that PSSs using remote signals may perform better than using local signals. The advent of phasor measurement units (PMU) makes remote or wide-area signals become available, which enables various important applications. Of particular interest is wide-area damping control (WADC), which aims to utilize remote or wide-area measurements to damp the inter-area oscillations. However, two main challenges in WADC design are (1) feedback controller input signal selection (which PMU signal is best to use?), and (2) latency (which is inherent in the transmission of the measurements) considerations. In response to the first challenge, this thesis proposes a concept called dominant inter-area oscillation path, which serves to pinpoint a set of candidate signals that can be used as the feedback controller inputs by locating the interconnected corridors where the inter-area modal contents are the most observable. Derivation, identification, and use of the dominant inter-area oscillation paths are demonstrated throughout the thesis. Extensive analysis on the relationships between the proposed set of signals and system properties regarding stability and robustness is presented. To tackle the second challenge, the impacts of time delays on the system performance when using the dominant path signals are investigated. To date, several studies have proposed different control design methods using various oscillation dampers to design WADC. Nevertheless, neither a systematic method nor a concept that encompasses fundamental knowledg, QC 20150414

This paper demonstrates the application of inverse filtering technique for power systems. In order to implement this method, the control objective should be based on a system variable that needs to be set on a specific value for each sampling time. A control input is calculated to generate the desired output of the plant and the relationship between the two is used design an auto-regressive model. The auto-regressive model is converted to a moving average model to calculate the control input based on the future values of the desired output. Therefore, required future values to construct the output are predicted to generate the appropriate control input for the next sampling time.

In this paper, the effect of fuzzy logic-based robust power system stabilizers on the improvement of the dynamics of a large-scale power system is investigated. The study is particularly focused on the Mexican Interconnected System and on adding damping to two critical inter-area system oscillation modes: The north-south mode and the western-peninsular mode. The fuzzy power system stabilizers (FPSSs) applied here are based on a significantly reduced rule base, small number of tuning parameters, and simple control algorithm and architecture, which makes their design and implementation easier and suitable for practical applications. Non-linear time-domain simulations for a set of test cases and results from Prony Analysis verify the robustness of the designed FPSSs, as compared to conventional PSSs., En el presente trabajo se investiga el efecto de estabilizadores de sistemas de potencia (PSSs) robustos, basados en lógica difusa, para mejorar la dinámica de sistemas de potencia complejos. En particular, el estudio se enfoca en mejorar el amortiguamiento de dos modos críticos de oscilación interárea del Sistema Interconectado Mexicano. Los PSSs difusos utilizados aquí se caracterizan por una base de reglas difusas reducida, pocos parámetros de sintonización y una arquitectura y algoritmo de control simples, lo cual facilita su diseño, implementación y aplicación práctica. Simulaciones en el dominio del tiempo con diversos escenarios de prueba y la aplicación del método de Prony comprueban la robustez de los PSSs difusos en comparación con PSSs convencionales.

In this paper, the effect of fuzzy logic-based robust power system stabilizers on the improvement of the dynamics of a large-scale power system is investigated. The study is particularly focused on the Mexican Interconnected System and on adding damping to two critical inter-area system oscillation modes: The north-south mode and the western-peninsular mode. The fuzzy power system stabilizers (FPSSs) applied here are based on a significantly reduced rule base, small number of tuning parameters, and simple control algorithm and architecture, which makes their design and implementation easier and suitable for practical applications. Non-linear time-domain simulations for a set of test cases and results from Prony Analysis verify the robustness of the designed FPSSs, as compared to conventional PSSs., En el presente trabajo se investiga el efecto de estabilizadores de sistemas de potencia (PSSs) robustos, basados en lógica difusa, para mejorar la dinámica de sistemas de potencia complejos. En particular, el estudio se enfoca en mejorar el amortiguamiento de dos modos críticos de oscilación interárea del Sistema Interconectado Mexicano. Los PSSs difusos utilizados aquí se caracterizan por una base de reglas difusas reducida, pocos parámetros de sintonización y una arquitectura y algoritmo de control simples, lo cual facilita su diseño, implementación y aplicación práctica. Simulaciones en el dominio del tiempo con diversos escenarios de prueba y la aplicación del método de Prony comprueban la robustez de los PSSs difusos en comparación con PSSs convencionales.

In this paper, the effect of fuzzy logic-based robust power system stabilizers on the improvement of the dynamics of a large-scale power system is investigated. The study is particularly focused on the Mexican Interconnected System and on adding damping to two critical inter-area system oscillation modes: The north-south mode and the western-peninsular mode. The fuzzy power system stabilizers (FPSSs) applied here are based on a significantly reduced rule base, small number of tuning parameters, and simple control algorithm and architecture, which makes their design and implementation easier and suitable for practical applications. Non-linear time-domain simulations for a set of test cases and results from Prony Analysis verify the robustness of the designed FPSSs, as compared to conventional PSSs., En el presente trabajo se investiga el efecto de estabilizadores de sistemas de potencia (PSSs) robustos, basados en lógica difusa, para mejorar la dinámica de sistemas de potencia complejos. En particular, el estudio se enfoca en mejorar el amortiguamiento de dos modos críticos de oscilación interárea del Sistema Interconectado Mexicano. Los PSSs difusos utilizados aquí se caracterizan por una base de reglas difusas reducida, pocos parámetros de sintonización y una arquitectura y algoritmo de control simples, lo cual facilita su diseño, implementación y aplicación práctica. Simulaciones en el dominio del tiempo con diversos escenarios de prueba y la aplicación del método de Prony comprueban la robustez de los PSSs difusos en comparación con PSSs convencionales.

In this paper, the effect of fuzzy logic-based robust power system stabilizers on the improvement of the dynamics of a large-scale power system is investigated. The study is particularly focused on the Mexican Interconnected System and on adding damping to two critical inter-area system oscillation modes: The north-south mode and the western-peninsular mode. The fuzzy power system stabilizers (FPSSs) applied here are based on a significantly reduced rule base, small number of tuning parameters, and simple control algorithm and architecture, which makes their design and implementation easier and suitable for practical applications. Non-linear time-domain simulations for a set of test cases and results from Prony Analysis verify the robustness of the designed FPSSs, as compared to conventional PSSs., En el presente trabajo se investiga el efecto de estabilizadores de sistemas de potencia (PSSs) robustos, basados en lógica difusa, para mejorar la dinámica de sistemas de potencia complejos. En particular, el estudio se enfoca en mejorar el amortiguamiento de dos modos críticos de oscilación interárea del Sistema Interconectado Mexicano. Los PSSs difusos utilizados aquí se caracterizan por una base de reglas difusas reducida, pocos parámetros de sintonización y una arquitectura y algoritmo de control simples, lo cual facilita su diseño, implementación y aplicación práctica. Simulaciones en el dominio del tiempo con diversos escenarios de prueba y la aplicación del método de Prony comprueban la robustez de los PSSs difusos en comparación con PSSs convencionales.

In this paper, the effect of fuzzy logic-based robust power system stabilizers on the improvement of the dynamics of a large-scale power system is investigated. The study is particularly focused on the Mexican Interconnected System and on adding damping to two critical inter-area system oscillation modes: The north-south mode and the western-peninsular mode. The fuzzy power system stabilizers (FPSSs) applied here are based on a significantly reduced rule base, small number of tuning parameters, and simple control algorithm and architecture, which makes their design and implementation easier and suitable for practical applications. Non-linear time-domain simulations for a set of test cases and results from Prony Analysis verify the robustness of the designed FPSSs, as compared to conventional PSSs., En el presente trabajo se investiga el efecto de estabilizadores de sistemas de potencia (PSSs) robustos, basados en lógica difusa, para mejorar la dinámica de sistemas de potencia complejos. En particular, el estudio se enfoca en mejorar el amortiguamiento de dos modos críticos de oscilación interárea del Sistema Interconectado Mexicano. Los PSSs difusos utilizados aquí se caracterizan por una base de reglas difusas reducida, pocos parámetros de sintonización y una arquitectura y algoritmo de control simples, lo cual facilita su diseño, implementación y aplicación práctica. Simulaciones en el dominio del tiempo con diversos escenarios de prueba y la aplicación del método de Prony comprueban la robustez de los PSSs difusos en comparación con PSSs convencionales.

The presence of inter-area oscillations has long affected stability constraints, and therefore, limited the power transfer capacity of interconnected power systems. Adequate damping of these inter-area oscillations is, thus, necessary to secure system operation and ensure system reliability while increasing power transfers. Power system stabilizers (PSS) are the most common devices used to enhance the damping of such oscillations. Many studies have demonstrated that PSSs using remote signals may perform better than using local signals. The advent of phasor measurement units (PMU) makes remote or wide-area signals become available, which enables various important applications. Of particular interest is wide-area damping control (WADC), which aims to utilize remote or wide-area measurements to damp the inter-area oscillations. However, two main challenges in WADC design are (1) feedback controller input signal selection (which PMU signal is best to use?), and (2) latency (which is inherent in the transmission of the measurements) considerations. In response to the first challenge, this thesis proposes a concept called dominant inter-area oscillation path, which serves to pinpoint a set of candidate signals that can be used as the feedback controller inputs by locating the interconnected corridors where the inter-area modal contents are the most observable. Derivation, identification, and use of the dominant inter-area oscillation paths are demonstrated throughout the thesis. Extensive analysis on the relationships between the proposed set of signals and system properties regarding stability and robustness is presented. To tackle the second challenge, the impacts of time delays on the system performance when using the dominant path signals are investigated. To date, several studies have proposed different control design methods using various oscillation dampers to design WADC. Nevertheless, neither a systematic method nor a concept that encompasses fundamental knowledg, QC 20150414

The presence of inter-area oscillations has long affected stability constraints, and therefore, limited the power transfer capacity of interconnected power systems. Adequate damping of these inter-area oscillations is, thus, necessary to secure system operation and ensure system reliability while increasing power transfers. Power system stabilizers (PSS) are the most common devices used to enhance the damping of such oscillations. Many studies have demonstrated that PSSs using remote signals may perform better than using local signals. The advent of phasor measurement units (PMU) makes remote or wide-area signals become available, which enables various important applications. Of particular interest is wide-area damping control (WADC), which aims to utilize remote or wide-area measurements to damp the inter-area oscillations. However, two main challenges in WADC design are (1) feedback controller input signal selection (which PMU signal is best to use?), and (2) latency (which is inherent in the transmission of the measurements) considerations. In response to the first challenge, this thesis proposes a concept called dominant inter-area oscillation path, which serves to pinpoint a set of candidate signals that can be used as the feedback controller inputs by locating the interconnected corridors where the inter-area modal contents are the most observable. Derivation, identification, and use of the dominant inter-area oscillation paths are demonstrated throughout the thesis. Extensive analysis on the relationships between the proposed set of signals and system properties regarding stability and robustness is presented. To tackle the second challenge, the impacts of time delays on the system performance when using the dominant path signals are investigated. To date, several studies have proposed different control design methods using various oscillation dampers to design WADC. Nevertheless, neither a systematic method nor a concept that encompasses fundamental knowledg, QC 20150414

The presence of inter-area oscillations has long affected stability constraints, and therefore, limited the power transfer capacity of interconnected power systems. Adequate damping of these inter-area oscillations is, thus, necessary to secure system operation and ensure system reliability while increasing power transfers. Power system stabilizers (PSS) are the most common devices used to enhance the damping of such oscillations. Many studies have demonstrated that PSSs using remote signals may perform better than using local signals. The advent of phasor measurement units (PMU) makes remote or wide-area signals become available, which enables various important applications. Of particular interest is wide-area damping control (WADC), which aims to utilize remote or wide-area measurements to damp the inter-area oscillations. However, two main challenges in WADC design are (1) feedback controller input signal selection (which PMU signal is best to use?), and (2) latency (which is inherent in the transmission of the measurements) considerations. In response to the first challenge, this thesis proposes a concept called dominant inter-area oscillation path, which serves to pinpoint a set of candidate signals that can be used as the feedback controller inputs by locating the interconnected corridors where the inter-area modal contents are the most observable. Derivation, identification, and use of the dominant inter-area oscillation paths are demonstrated throughout the thesis. Extensive analysis on the relationships between the proposed set of signals and system properties regarding stability and robustness is presented. To tackle the second challenge, the impacts of time delays on the system performance when using the dominant path signals are investigated. To date, several studies have proposed different control design methods using various oscillation dampers to design WADC. Nevertheless, neither a systematic method nor a concept that encompasses fundamental knowledg, QC 20150414

Spectral analysis applied to synchrophasor data can provide valuable information about lightly damped low-frequency modes in power systems. This paper demonstrates application of two non-parametric spectral estimators focusing on mode frequency estimation. The first one is the well-known Welch spectral estimator whereas the application of Multitaper method is proposed here. In addition, the paper discusses mode estimator tuning procedures and the estimators' performances in the presence of 'forced' oscillations. The validity of the proposed application of the non-parametric estimators and tuning procedures is verified through both simulated data and PMU data originating from the high-voltage grid of the Nordic power system. Special attention is given to the analysis of the behaviour of different low frequency modes present in the Nordic grid, including that of forced oscillations., QC 20140113

This paper presents three algorithms for identification of dominant inter-area oscillation paths: a series of interconnected corridors in which the highest content of the inter-area modes propagates through. The algorithms are developed to treat different sets of data: 1) known system model; 2) transient; and 3) ambient measurements from phasor measurement units (PMUs). These algorithms take feasibility into consideration by associating the network variables made available by PMUs, i.e., voltage and current phasors. All algorithms are demonstrated and implemented on a conceptualized Nordic Grid model. The results and comparison among three algorithms are provided. The applications of the algorithms not only facilitate in revealing critical corridors which are mostly stressed but also help in indicating relevant feedback input signals and inputs to mode meters which can be determined from the properties of dominant paths., QC 20130821

Spectral analysis applied to synchrophasor data can provide valuable information about lightly damped low-frequency modes in power systems. This paper demonstrates application of two non-parametric spectral estimators focusing on mode frequency estimation. The first one is the well-known Welch spectral estimator whereas the application of Multitaper method is proposed here. In addition, the paper discusses mode estimator tuning procedures and the estimators' performances in the presence of 'forced' oscillations. The validity of the proposed application of the non-parametric estimators and tuning procedures is verified through both simulated data and PMU data originating from the high-voltage grid of the Nordic power system. Special attention is given to the analysis of the behaviour of different low frequency modes present in the Nordic grid, including that of forced oscillations., QC 20140113

In the current energy exchange market it is essential to guarantee continuity and quality of supply both in steady state and during contingencies that might occur in any subsystem of interconnected systems. In this work it is shown how the geographical and topological characteristics of the subnetworks directly affect the quality and reliability in the energy exchange, especially when subsystems are interconnected without asynchronous ties that prevent power, frequency or voltage oscillations. This paper describes the problems faced by the interconnection between Mexico and the countries that define the Interconnected Electric System of the Central American Countries (SIEPAC). Different oscillations that have occurred are analyzed. Discrete control schemes to automatically trigger the 400 KV circuit that interconnects the systems of Mexico and Guatemala are proposed., QC 20140317

A contribution to CIGRE WG B5-14 “Wide Area Protection and Control Technologies”Chapter: Assess the opportunities and benefits to be gained from real -time synchrophasors as applied to protection and control and synchronized sample measurements Chapter Task: SMU (PMU) supported applications for inter-area oscillationsQC 20130830

A contribution to CIGRE WG B5-14 “Wide Area Protection and Control Technologies”Chapter: Assess the opportunities and benefits to be gained from real -time synchrophasors as applied to protection and control and synchronized sample measurements Chapter Task: SMU (PMU) supported applications for inter-area oscillationsQC 20130830

This thesis was a step forward in improving the stability of power systems by applying new control and modelling techniques. The developed methods use the data obtained from voltage angle measurement devices which are synchronized with GPS signals to stabilize the system and avoid system-wide blackouts in the event of severe faults. New approaches were developed in this research for identifying and estimating reduced dynamic system models using phasor measurement units. The main goal of this research is achieved by integrating the developed methods to obtain a feasible wide-area control system for stabilizing the power systems.

A contribution to CIGRE WG B5-14 “Wide Area Protection and Control Technologies”Chapter: Assess the opportunities and benefits to be gained from real -time synchrophasors as applied to protection and control and synchronized sample measurements Chapter Task: SMU (PMU) supported applications for inter-area oscillationsQC 20130830

Spectral analysis applied to synchrophasor data can provide valuable information about lightly damped low-frequency modes in power systems. This paper demonstrates application of two non-parametric spectral estimators focusing on mode frequency estimation. The first one is the well-known Welch spectral estimator whereas the application of Multitaper method is proposed here. In addition, the paper discusses mode estimator tuning procedures and the estimators' performances in the presence of 'forced' oscillations. The validity of the proposed application of the non-parametric estimators and tuning procedures is verified through both simulated data and PMU data originating from the high-voltage grid of the Nordic power system. Special attention is given to the analysis of the behaviour of different low frequency modes present in the Nordic grid, including that of forced oscillations., QC 20140113

Spectral analysis applied to synchrophasor data can provide valuable information about lightly damped low-frequency modes in power systems. This paper demonstrates application of two non-parametric spectral estimators focusing on mode frequency estimation. The first one is the well-known Welch spectral estimator whereas the application of Multitaper method is proposed here. In addition, the paper discusses mode estimator tuning procedures and the estimators' performances in the presence of 'forced' oscillations. The validity of the proposed application of the non-parametric estimators and tuning procedures is verified through both simulated data and PMU data originating from the high-voltage grid of the Nordic power system. Special attention is given to the analysis of the behaviour of different low frequency modes present in the Nordic grid, including that of forced oscillations., QC 20140113

A contribution to CIGRE WG B5-14 “Wide Area Protection and Control Technologies”Chapter: Assess the opportunities and benefits to be gained from real -time synchrophasors as applied to protection and control and synchronized sample measurements Chapter Task: SMU (PMU) supported applications for inter-area oscillationsQC 20130830

A contribution to CIGRE WG B5-14 “Wide Area Protection and Control Technologies”Chapter: Assess the opportunities and benefits to be gained from real -time synchrophasors as applied to protection and control and synchronized sample measurements Chapter Task: SMU (PMU) supported applications for inter-area oscillationsQC 20130830

Spectral analysis applied to synchrophasor data can provide valuable information about lightly damped low-frequency modes in power systems. This paper demonstrates application of two non-parametric spectral estimators focusing on mode frequency estimation. The first one is the well-known Welch spectral estimator whereas the application of Multitaper method is proposed here. In addition, the paper discusses mode estimator tuning procedures and the estimators' performances in the presence of 'forced' oscillations. The validity of the proposed application of the non-parametric estimators and tuning procedures is verified through both simulated data and PMU data originating from the high-voltage grid of the Nordic power system. Special attention is given to the analysis of the behaviour of different low frequency modes present in the Nordic grid, including that of forced oscillations., QC 20140113

This paper deals with optimal coordinated control of several high voltage direct current (HVDC) links based on an estimated model of large power systems. The model of the power system is estimated by using subspace system identification techniques. An optimal controller is designed based on the estimated model with the aim to improve the damping in the system. The main contribution of this paper is the development of a new method which uses global Phasor measurement units (PMUs) signals for coordinated damping control of multiple HVDC links. The input signals are the controllable set-points of the HVDC links, the output signals are the speed signals of selected generators obtained from PMU. The PMU signals are used to estimate the current state of the model, i.e., the state of the system, an appropriate control action can then be applied to dampen the system. The benefit of the method is that the used output signals, i.e., the used PMU signals, are independent of the system equilibrium and therefore makes it possible to use state-feedback control, i.e., coordinated control. The method is applied to the Cigre Nordic 32-bus system including two HVDC links. The consistent results show that the damping can be significantly increased., QC 20120503

This paper is concerned with the use of subspace system identification techniques to derive a low-order black-box state-space model of a power system with many controllable devices. This is a multi-input multi-output open system model describing the power oscillatory behavior of the power system. The input signals are the controllable set points of the controllable devices, the output signals are the speed of some generators measured by a wide-area measurement system. This paper describes how to achieve and pre-process the data to use the subspace method to estimate and validate to finally assign an accurate model. This new approach can be used directly for the design of a centrally coordinated controller coordinating all the relevant controllable devices, with the aim to increase the damping of the modes in the system. Previously presented models, using input signals from controllable devices, use local measurements or output signals dependent on the actual operational point. The benefit of the presented method is that the used output signals are independent of the system state. This makes it possible to use a state-feedback controller, i.e., coordinated control. The presented method is applied in the Cigré Nordic 32-bus system including two high-voltage direct current (HVDC) links. The case study demonstrates that accurate low-order state-space models can be estimated and validated using the described method to accurately model the system's power oscillatory behavior., QC 20240110

This article discusses the degree of persistence of dominant inter-area oscillation paths: the passageways containing the highest content of inter-area oscillations in large-scale power networks. To this aim, a number of contingency studies are carried out: faults being imposed on the lines connecting to the dominant inter-area path. The path persistence is then examined using the relationship between sensitivities of network variables (i.e. voltages and current, magnitude and angle), and mode shapes describing the contribution of the oscillations among the generators variables (e.g. speed and angle). This relationship is termed network modeshape. The larger in magnitude and the lesser the variation the network modeshape is, the more observable and the more robust the signals measured from the dominant path becomes. The outcome is a proposed signal combination to be used as inputs to the damping controller for mitigation of inter-area oscillations in large-scale power systems., QC 20131007

Dominant interaction paths are the passageways containing the highest modal content of particular oscillations in interconnected power systems. For the case of inter-area modes, pinpointing the dominant path that corresponds to each mode may allow for the extraction of signals that bear a significant modal content at a particular inter-area frequency. Strong modal content for these inter-area modes may also be spread onto secondary paths. These secondary paths bear similar properties as those shown by dominant paths. The aim of this study is thus to demonstrate the persistence of both dominant and secondary paths by employing “network modeshape” properties. The existence of the paths is verified by nonlinear time-domain simulations where modal content at each inter-area frequency is extracted. The proper selection of feedback signals from the dominating paths may increase the flexibility of WAPODs by providing a number of signal choices to be used as backup in the presence of contingencies., QC 20120927

This article presents an implementation of a Nordic grid model in Power System Analysis Toolbox (PSAT) -a free and open-source software. A newly developed hydro turbine and hydro governor (HTG) model is implemented with this grid model and compared with the currently available PSAT turbine and governor models. Small-signal and transient stability analyses of the system using the two models are carried out and compared to demonstrate the difference and necessity of accurate hydro turbine and governor model utilization. The paper ends with a validation of the linearized Nordic grid model generated by PSAT including the newly implemented HTG models. This validation is done through nonlinear time-domain simulation by applying both large and small disturbances., QC 20120927

This article analyzes the impact of forced power system oscillations on mode damping estimation. Parametric (Yule-Walker) and non-parametric (Welch) methods for mode estimation are tested in the presence of forced power system oscillations. For mode damping estimation based on non-parametric methods, an application of Half Power Point method is proposed. Performances of the mode estimators are evaluated using both simulated and real synchrophasor data from the Nordic Grid. The presence of forced oscillations poses difficulties to mode damping estimators, these difficulties are identified, illustrated and explained herein., QC 20130122

In the Nordic power network, the existence of poorly damped low-frequency inter-area oscillations (LFIOs) has long affected stability constraints, and thereby, limited power transfer capacity. Adequate damping of inter-area modes is, thus, necessary to secure system operation and ensure system reliability while increasing power transfers. Power system stabilizers (PSS) is a prevalent means to enhance the damping of such modes. With the advent of phasor measurement units (PMUs), it is expected that wide-area damping control (WADC), that is, PSS control using wide-area measurements obtained from PMUs, would effectively improve damping performance in the Nordic grid, as well as other synchronous interconnected systems. Numerous research has investigated one ``branch'' of the problem, that is, PSS design using various control schemes. Before addressing the issue of controller design, it is important to focus on developing proper understanding of the ``root'' of the problem: system-wide oscillations, their nature, behavior and consequences. This understanding must provide new insight on the use of PMUs for feedback control of LFIOs. The aim of this thesis is, therefore, to lay important concepts necessary for the study of power system small signal stability analysis that considers the availability of synchrophasors as a solid foundation for further development and implementation of ideas and related applications. Particularly in this study, the focus is on the application addressed damping controller design and implementation. After a literature review on the important elements for wide-area damping control (WADC), the thesis continues with classical small signal stability analysis of an equivalent Nordic model; namely, the KTH-NORDIC32 which is used as a test system throughout the thesis. The system's inter-area oscillations are identified and a sensitivity analysis of the network variables directly measured by synchrophasors is evaluated. The concept of network modesha

In the Nordic power network, the existence of poorly damped low-frequency inter-area oscillations (LFIOs) has long affected stability constraints, and thereby, limited power transfer capacity. Adequate damping of inter-area modes is, thus, necessary to secure system operation and ensure system reliability while increasing power transfers. Power system stabilizers (PSS) is a prevalent means to enhance the damping of such modes. With the advent of phasor measurement units (PMUs), it is expected that wide-area damping control (WADC), that is, PSS control using wide-area measurements obtained from PMUs, would effectively improve damping performance in the Nordic grid, as well as other synchronous interconnected systems. Numerous research has investigated one ``branch'' of the problem, that is, PSS design using various control schemes. Before addressing the issue of controller design, it is important to focus on developing proper understanding of the ``root'' of the problem: system-wide oscillations, their nature, behavior and consequences. This understanding must provide new insight on the use of PMUs for feedback control of LFIOs. The aim of this thesis is, therefore, to lay important concepts necessary for the study of power system small signal stability analysis that considers the availability of synchrophasors as a solid foundation for further development and implementation of ideas and related applications. Particularly in this study, the focus is on the application addressed damping controller design and implementation. After a literature review on the important elements for wide-area damping control (WADC), the thesis continues with classical small signal stability analysis of an equivalent Nordic model; namely, the KTH-NORDIC32 which is used as a test system throughout the thesis. The system's inter-area oscillations are identified and a sensitivity analysis of the network variables directly measured by synchrophasors is evaluated. The concept of network modesha

This article discusses the degree of persistence of dominant inter-area oscillation paths: the passageways containing the highest content of inter-area oscillations in large-scale power networks. To this aim, a number of contingency studies are carried out: faults being imposed on the lines connecting to the dominant inter-area path. The path persistence is then examined using the relationship between sensitivities of network variables (i.e. voltages and current, magnitude and angle), and mode shapes describing the contribution of the oscillations among the generators variables (e.g. speed and angle). This relationship is termed network modeshape. The larger in magnitude and the lesser the variation the network modeshape is, the more observable and the more robust the signals measured from the dominant path becomes. The outcome is a proposed signal combination to be used as inputs to the damping controller for mitigation of inter-area oscillations in large-scale power systems., QC 20131007

Dominant interaction paths are the passageways containing the highest modal content of particular oscillations in interconnected power systems. For the case of inter-area modes, pinpointing the dominant path that corresponds to each mode may allow for the extraction of signals that bear a significant modal content at a particular inter-area frequency. Strong modal content for these inter-area modes may also be spread onto secondary paths. These secondary paths bear similar properties as those shown by dominant paths. The aim of this study is thus to demonstrate the persistence of both dominant and secondary paths by employing “network modeshape” properties. The existence of the paths is verified by nonlinear time-domain simulations where modal content at each inter-area frequency is extracted. The proper selection of feedback signals from the dominating paths may increase the flexibility of WAPODs by providing a number of signal choices to be used as backup in the presence of contingencies., QC 20120927

This article presents an implementation of a Nordic grid model in Power System Analysis Toolbox (PSAT) -a free and open-source software. A newly developed hydro turbine and hydro governor (HTG) model is implemented with this grid model and compared with the currently available PSAT turbine and governor models. Small-signal and transient stability analyses of the system using the two models are carried out and compared to demonstrate the difference and necessity of accurate hydro turbine and governor model utilization. The paper ends with a validation of the linearized Nordic grid model generated by PSAT including the newly implemented HTG models. This validation is done through nonlinear time-domain simulation by applying both large and small disturbances., QC 20120927

The traditional approach to damp inter-area oscillations is through the installation of Power System Stabilizers (PSSs) which provide damping control action through excitation control systems of the generating units. However, study of recent blackouts has shown that the control action provided by a PSS alone is not sufficient for damping oscillations in modern power systems which operate under stressed conditions. An integrated form of control using remote measurements to coordinate the different control elements present in the system is the need of the hour. One way of implementing such a coordinated control is through the development of a Linear Matrix Inequality (LMI)-based polytopic model of the system that guarantees pole placement for a variety of operating conditions. The size of the polytopic formulation is an issue for application of LMIs to large systems. The use of Selective Modal Analysis (SMA) alleviates this problem by reducing the size of the system. The previous attempts have used a model containing all the and modes, with SMA being used to eliminate all the other states. In practical applications the resulting system was still found to be too large to use in a polytopic model. This thesis presents an algorithm to reduce the size of the system to the relevant modes of oscillations. A 16 machine, 68 bus equivalent model of the New England-New York interconnected power system is used as the test case with DC lines and SVCs acting as the control. The algorithm is then applied to a 127-bus equivalent model of the WECC System. The use of ESDs as a form of control is also demonstrated. The results indicate that the proposed control successfully damps the relevant modes of oscillations without negatively damping the other modes. The control is then transferred to a more detailed 4000+ bus model of the WECC system to realize its performance on real-world systems.

In the Nordic power network, the existence of poorly damped low-frequency inter-area oscillations (LFIOs) has long affected stability constraints, and thereby, limited power transfer capacity. Adequate damping of inter-area modes is, thus, necessary to secure system operation and ensure system reliability while increasing power transfers. Power system stabilizers (PSS) is a prevalent means to enhance the damping of such modes. With the advent of phasor measurement units (PMUs), it is expected that wide-area damping control (WADC), that is, PSS control using wide-area measurements obtained from PMUs, would effectively improve damping performance in the Nordic grid, as well as other synchronous interconnected systems. Numerous research has investigated one ``branch'' of the problem, that is, PSS design using various control schemes. Before addressing the issue of controller design, it is important to focus on developing proper understanding of the ``root'' of the problem: system-wide oscillations, their nature, behavior and consequences. This understanding must provide new insight on the use of PMUs for feedback control of LFIOs. The aim of this thesis is, therefore, to lay important concepts necessary for the study of power system small signal stability analysis that considers the availability of synchrophasors as a solid foundation for further development and implementation of ideas and related applications. Particularly in this study, the focus is on the application addressed damping controller design and implementation. After a literature review on the important elements for wide-area damping control (WADC), the thesis continues with classical small signal stability analysis of an equivalent Nordic model; namely, the KTH-NORDIC32 which is used as a test system throughout the thesis. The system's inter-area oscillations are identified and a sensitivity analysis of the network variables directly measured by synchrophasors is evaluated. The concept of network modesha

Dominant interaction paths are the passageways containing the highest modal content of particular oscillations in interconnected power systems. For the case of inter-area modes, pinpointing the dominant path that corresponds to each mode may allow for the extraction of signals that bear a significant modal content at a particular inter-area frequency. Strong modal content for these inter-area modes may also be spread onto secondary paths. These secondary paths bear similar properties as those shown by dominant paths. The aim of this study is thus to demonstrate the persistence of both dominant and secondary paths by employing “network modeshape” properties. The existence of the paths is verified by nonlinear time-domain simulations where modal content at each inter-area frequency is extracted. The proper selection of feedback signals from the dominating paths may increase the flexibility of WAPODs by providing a number of signal choices to be used as backup in the presence of contingencies., QC 20120927

Dominant interaction paths are the passageways containing the highest modal content of particular oscillations in interconnected power systems. For the case of inter-area modes, pinpointing the dominant path that corresponds to each mode may allow for the extraction of signals that bear a significant modal content at a particular inter-area frequency. Strong modal content for these inter-area modes may also be spread onto secondary paths. These secondary paths bear similar properties as those shown by dominant paths. The aim of this study is thus to demonstrate the persistence of both dominant and secondary paths by employing “network modeshape” properties. The existence of the paths is verified by nonlinear time-domain simulations where modal content at each inter-area frequency is extracted. The proper selection of feedback signals from the dominating paths may increase the flexibility of WAPODs by providing a number of signal choices to be used as backup in the presence of contingencies., QC 20120927

This article presents an implementation of a Nordic grid model in Power System Analysis Toolbox (PSAT) -a free and open-source software. A newly developed hydro turbine and hydro governor (HTG) model is implemented with this grid model and compared with the currently available PSAT turbine and governor models. Small-signal and transient stability analyses of the system using the two models are carried out and compared to demonstrate the difference and necessity of accurate hydro turbine and governor model utilization. The paper ends with a validation of the linearized Nordic grid model generated by PSAT including the newly implemented HTG models. This validation is done through nonlinear time-domain simulation by applying both large and small disturbances., QC 20120927

This article discusses the degree of persistence of dominant inter-area oscillation paths: the passageways containing the highest content of inter-area oscillations in large-scale power networks. To this aim, a number of contingency studies are carried out: faults being imposed on the lines connecting to the dominant inter-area path. The path persistence is then examined using the relationship between sensitivities of network variables (i.e. voltages and current, magnitude and angle), and mode shapes describing the contribution of the oscillations among the generators variables (e.g. speed and angle). This relationship is termed network modeshape. The larger in magnitude and the lesser the variation the network modeshape is, the more observable and the more robust the signals measured from the dominant path becomes. The outcome is a proposed signal combination to be used as inputs to the damping controller for mitigation of inter-area oscillations in large-scale power systems., QC 20131007