Anantha M Pai - Academia.edu (original) (raw)

Papers by Anantha M Pai

1986 25th IEEE Conference on Decision and Control, 1986

ABSTRACT

IEEE Transactions on Power Apparatus and Systems, 1981

Catastrophe theory is used to determine the transient stability regions of multimachine power sys... more Catastrophe theory is used to determine the transient stability regions of multimachine power systems. The stability region so obtained for a power system is valid for any fault location or system loading. The energy balance equation is first expanded in a Taylor series in terms of the clearing time and the system transient parameters. The energy function is then put in the form of a catastrophe manifold from which the boundaries of the transient stability region are extracted by bifurcation analysis. The transient stability problem is dealt with in terms of the two dimensions critical clearing time and transient stability limits. The transient stability limits are calculated from the bifurcation set and the critical clearing times are calculated from the catastrophe manifold equation. The proposed method permits more detailed modelling of the power system to include such effects as excitation response and flux decay.

IEEE Power Engineering Society General Meeting, 2004.

This work discusses the use of trajectory sensitivity analysis (TSA) in determining the stable op... more This work discusses the use of trajectory sensitivity analysis (TSA) in determining the stable operating range of a thyristor controlled series compensator (TCSC) compensated power system. The TCSC is modeled by a variable capacitor, the value of which changes with the firing angle. The trajectory sensitivity analysis is applied to two different systems - an SMIB system and a 3-machine, 9-bus system. It is shown that the lumped parameter TCSC model is sufficient to predict the operation of the systems. The predicted behavior using the TSA is validated using PSCAD/EMTDC simulation. Furthermore, it is shown that the TSA can be used in the determination of the optimal location for the placement of the TCSC in the 9-bus system.

In this paper, the traditional AGC two area system is modified to take into account the role of A... more In this paper, the traditional AGC two area system is modified to take into account the role of AGC as an ancillary service. The concept of DISCO participation matrix is introduced and reflected in the two-area diagram. Simulation studies as well as trajectory sensitivity studies are done, the latter for optimization.

Stability and Control of Dynamical Systems with Applications, 2003

Trajectory sensitivity analysis (TSA) has been applied in control system problems for a long time... more Trajectory sensitivity analysis (TSA) has been applied in control system problems for a long time in such areas as optimization and adaptive control. Applications in power systems in conjunction with Lyapunov/transient energy functions first appeared in the 1980s. More recently, TSA has found applications on its own by defining a suitable metric on the trajectory sensitivities with respect to the parameters of interest. In this chapter we present theoretical as well as practical applications of TSA for dynamic security applications in power systems. We also discuss the technique to compute critical values of any parameter that induces stability in the system using trajectory sensitivities.

2009 IEEE/PES Power Systems Conference and Exposition, 2009

... Golden, CO 80401 eduard_muljadi@nrel.gov MA Pai3 3University of Illinois 1406 W. Green Street... more ... Golden, CO 80401 eduard_muljadi@nrel.gov MA Pai3 3University of Illinois 1406 W. Green Street Urbana IL 61801 mapai@uiuc.edu TB Nguyen2 2PNNL PO Box 999, MS K1-85 Richland, WA 99354 tony.nguyen@pnl.gov 978-1-4244-3811-2/09/$25.00 ©2009 IEEE Page 2. ...

Power Electronics and Power Systems, 2014

Real-time stability evaluation and preventive scheduling in power systems offer many challenges i... more Real-time stability evaluation and preventive scheduling in power systems offer many challenges in a stressed power system. Trajectory Sensitivity Analysis (TSA) is a useful tool for this and other applications in the emerging smart grid area. In this chapter, we outline the basic approach of TSA, to extract suitable information from the data and develop reliable metrics or indices to evaluate proximity of the system to an unstable condition. Trajectory sensitivities can be used to compute critical parameters such as clearing time of circuit breakers, tie-line flow, etc. in a power system by developing suitable norms for ease of interpretation. The TSA technique has the advantage that model complexity is not a limitation, and the sensitivities can be computed numerically. Suitable metrics are developed from these sensitivities. The TSA technique can be extended to do preventive rescheduling. A brief discussion of other applications of TSA in placement of distributed generation is indicated.

International Journal of Control, 1974

... 1. Introduction The effect of flux-decay and voltage regulator action on the transient stabil... more ... 1. Introduction The effect of flux-decay and voltage regulator action on the transient stability of a synchronous generator has been investigated previously (Crary If)47, Kimbark If).56, Demello and Concordia 196fJ, Siddique 1968, Willems If)6fJ, Gupta and Davies 1fJ61, Fallside ...

Transactions of the American Institute of Electrical Engineers, Part II: Applications and Industry, 1963

radius 1/T. The damping ratio is The locus of the zeros is shown in Fig. 31. Note that with suita... more radius 1/T. The damping ratio is The locus of the zeros is shown in Fig. 31. Note that with suitable choice of T and m 2f all left-hand plane locations can be achieved. Right-hand plane locations are achievable only for a small sector, £>-1/2. The authors' Figs. 13, 17, 21, and 23 * So far as the mathematical treatment is concerned, the hold circuit and the nonlinearity can be inter changed as shown in Fig. 1(B).

IEEE International Symposium on Circuits and Systems

It is shown that the maximum loadability of a power system depends on the allocation of load and ... more It is shown that the maximum loadability of a power system depends on the allocation of load and generation. For a given load distribution by percentage and constant power factor, the maximum can be described by a scalar. The maximum value of this scalar depends on the generation scheduling. It is shown how the maximum loadability can be computed when there are no inequality constraints on the generation scheduling, line flows, or bus voltages. As in load flow, the set of nonlinear equations used does not have a unique solution. Further work is needed to see how the initial guess affects the solution

IEEE Power Engineering Review, 1983

ensure the qualification of environmentally qualified, safety-related equipment is performed Phas... more ensure the qualification of environmentally qualified, safety-related equipment is performed Phase consists of the evaluation of a selected subset of the safety-related equipment For this subset the qualification documen tation was reviewed and the maintenance activities that are required to ensure the qualification of the equipment were determined The actual maintenance being performed at the nuclear power plant on the equipment under consideration was determined Based on this information, recommendations were made for im provements and changes The recommendations included 1) Recommendations for incorporating additional maintenance that should be performed to ensure equipment qualification 2) Recommendations to consider deleting unnecessary or re dundant maintenance, or reducing the frequency of main¬ tenance as a result of qualification data 3) Recommendations to revise the maintenance procedures as a result of qualification considerations 4) Recommendations to revise the maintenance procedure to im¬ prove the overall maintenance activity Examples of each kind of recommendation are included A program to evaluate a subset of the safety-related equipment is an effective way to determine what maintenance, ofthat required for equipment qualification, is in place, and to provide the recommen dations for additional maintenance actions to ensure qualification 83 WM 023-9

ISCAS '98. Proceedings of the 1998 IEEE International Symposium on Circuits and Systems (Cat. No.98CH36187)

The development of trajectory sensitivity analysis for power systems is presented in the paper. A... more The development of trajectory sensitivity analysis for power systems is presented in the paper. A hybrid system model which has a differential-algebraic-discrete structure is proposed. Crucial to the analysis is the development of jump conditions describing the behaviour of sensitivities at discrete events, such as switching and state resetting. A power system example which involves a mix of continuous and discrete behaviour is presented to illustrate various aspects of the theory. It is shown that trajectory sensitivities provide insights into system behaviour which cannot be obtained from traditional simulations.

Lecture Notes in Computer Science, 2006

In operations, simulation and control of power systems, the presence of real-time data relating t... more In operations, simulation and control of power systems, the presence of real-time data relating to system states can yield precise forecasts and can enable robust active control. In this research we are developing efficient and robust methods to produce "data enhanced" reduced order models and filters for large-scale power systems. The application that this paper focuses on is the creation of new data-driven tools for electric power system operation and control. The applications systems include traditional SCADA systems as well as emerging PMU data concentrators. A central challenge is to provide near real-time condition assessment for "extreme events," as well as long-term assessment of the deterioration of the electrical power grid. In order to provide effective guidance for power system control, we are also developing visualization methods for integrating multiple data sets. These visualization methods provide an up-to-date view of the system state, and guide operatorinitiated power system control.

2002 IEEE Power Engineering Society Winter Meeting. Conference Proceedings (Cat. No.02CH37309)

Trajectory sensitivities complement time domain simulation in the analysis of large disturbance d... more Trajectory sensitivities complement time domain simulation in the analysis of large disturbance dynamic behaviour of power systems. They are formed by linearization around a nonlinear, and possibly non-smooth, trajectory. The influence of parameter variations on large disturbance behaviour can be estimated (to first order) from these sensitivities. Large (small) sensitivities indicate that a parameter has a significant (negligible) effect on behaviour. These insights are helpful in analysing the underlying influences on system dynamics, and for assessing the significance of parameter uncertainty. Further, trajectory sensitivities provide gradient information for applications such as parameter estimation, boundary value problems, bordercollision bifurcations, and optimal control.

Power Electronics and Power Systems, 2014

The material in this chapter focuses on the relationship between power system dynamic equilibrium... more The material in this chapter focuses on the relationship between power system dynamic equilibrium, power flow, and operating point stability. It addresses issues relating steady-state equilibrium in electric power systems with possible implications about stability of the associated operating point. It presents various connections between dynamic models, dynamic equilibrium, power-flow analysis, and the significance of singularities of Jacobian matrices involved in various computations. It includes advances on earlier work on this subject and provides recent results on computing the equilibrium of “post-contingency” models. These post-contingency models are created to enforce the concept of “constant control inputs” in the steady-state analysis. This impacts subtle things such as post-contingency speed (frequency) and remote voltage regulation. The concepts are illustrated on small system models. Different methods of computation are presented to provide alternatives for possible practical implementation.

Energy Function Analysis for Power System Stability, 1989

An interconnected power system consists of generating units (including turbine-governor and excit... more An interconnected power system consists of generating units (including turbine-governor and excitation systems), transmission lines, loads, transformers (including off-nominal ratio and phase shifting transformers), static var compensators and HVDC lines. The size of the interconnection varies but the technical problems are the same. It is not uncommon for some utilities to study systems which have 10,000 buses. As a rule of thumb about one fourth of these buses will have generators connected. At the planning level, after examining the adequacy of transmission capacity, economy of generation etc., the planner would invariably study the stability of the system for a set of disturbances ranging from the worst, such as three phase to ground fault (whose probability of occurrence is rare) to single phase faults which constitute about 70% of the disturbances. There are good production grade programs which simulate the time behavior of the system for such disturbances. There are literally thousands of variables that can be monitored even on a moderate sized system such as a 500 bus system. The planner wants to see if a fault is properly cleared without the system losing synchronism. A system is said to be synchronously stable (i.e., retain synchronism) for a given fault if the system variables settle down to some steady state values as t → ∞. These simulation studies are called transient stability studies. A typical transient stability study with detailed modeling for a 500 bus 100 machine system might take up to an hour.

International Journal of Electrical Power & Energy Systems, 1996

This paper discusses modelling and theoretical issues associated with voltage and angle stability... more This paper discusses modelling and theoretical issues associated with voltage and angle stability of power systems. A timescale decomposition is performed to illustrate how the critical modes can be identified with reduced-order models and the bifurcation phenomena can be explained with these low order models. Examples are given for single and muhimachine systems.

IEEE Transactions on Power Systems, 1987

Page 1. IEEE Transactions on Power Systems, Vol. PWRS-2, No. 2, May 1987 REDUCED ORDER MODELING O... more Page 1. IEEE Transactions on Power Systems, Vol. PWRS-2, No. 2, May 1987 REDUCED ORDER MODELING OF INTERCONNECTED MULTIMACHINE POWER SYSTEMS USING TIME-SCALE DECOMPOSITION DJ LaGesse S. Ahmed-Zaid MA Pai ...

IEEE Transactions on Power Systems, 2001

In this paper, the traditional AGC two-area system is modified to take into account the effect of... more In this paper, the traditional AGC two-area system is modified to take into account the effect of bilateral contracts on the dynamics. The concept of DISCO participation matrix to simulate these bilateral contracts is introduced and reflected in the two-area block diagram. Trajectory sensitivities are used to obtain optimal parameters of the system using a gradient Newton algorithm.

1986 25th IEEE Conference on Decision and Control, 1986

ABSTRACT

IEEE Transactions on Power Apparatus and Systems, 1981

Catastrophe theory is used to determine the transient stability regions of multimachine power sys... more Catastrophe theory is used to determine the transient stability regions of multimachine power systems. The stability region so obtained for a power system is valid for any fault location or system loading. The energy balance equation is first expanded in a Taylor series in terms of the clearing time and the system transient parameters. The energy function is then put in the form of a catastrophe manifold from which the boundaries of the transient stability region are extracted by bifurcation analysis. The transient stability problem is dealt with in terms of the two dimensions critical clearing time and transient stability limits. The transient stability limits are calculated from the bifurcation set and the critical clearing times are calculated from the catastrophe manifold equation. The proposed method permits more detailed modelling of the power system to include such effects as excitation response and flux decay.

IEEE Power Engineering Society General Meeting, 2004.

This work discusses the use of trajectory sensitivity analysis (TSA) in determining the stable op... more This work discusses the use of trajectory sensitivity analysis (TSA) in determining the stable operating range of a thyristor controlled series compensator (TCSC) compensated power system. The TCSC is modeled by a variable capacitor, the value of which changes with the firing angle. The trajectory sensitivity analysis is applied to two different systems - an SMIB system and a 3-machine, 9-bus system. It is shown that the lumped parameter TCSC model is sufficient to predict the operation of the systems. The predicted behavior using the TSA is validated using PSCAD/EMTDC simulation. Furthermore, it is shown that the TSA can be used in the determination of the optimal location for the placement of the TCSC in the 9-bus system.

In this paper, the traditional AGC two area system is modified to take into account the role of A... more In this paper, the traditional AGC two area system is modified to take into account the role of AGC as an ancillary service. The concept of DISCO participation matrix is introduced and reflected in the two-area diagram. Simulation studies as well as trajectory sensitivity studies are done, the latter for optimization.

Stability and Control of Dynamical Systems with Applications, 2003

Trajectory sensitivity analysis (TSA) has been applied in control system problems for a long time... more Trajectory sensitivity analysis (TSA) has been applied in control system problems for a long time in such areas as optimization and adaptive control. Applications in power systems in conjunction with Lyapunov/transient energy functions first appeared in the 1980s. More recently, TSA has found applications on its own by defining a suitable metric on the trajectory sensitivities with respect to the parameters of interest. In this chapter we present theoretical as well as practical applications of TSA for dynamic security applications in power systems. We also discuss the technique to compute critical values of any parameter that induces stability in the system using trajectory sensitivities.

2009 IEEE/PES Power Systems Conference and Exposition, 2009

... Golden, CO 80401 eduard_muljadi@nrel.gov MA Pai3 3University of Illinois 1406 W. Green Street... more ... Golden, CO 80401 eduard_muljadi@nrel.gov MA Pai3 3University of Illinois 1406 W. Green Street Urbana IL 61801 mapai@uiuc.edu TB Nguyen2 2PNNL PO Box 999, MS K1-85 Richland, WA 99354 tony.nguyen@pnl.gov 978-1-4244-3811-2/09/$25.00 ©2009 IEEE Page 2. ...

Power Electronics and Power Systems, 2014

Real-time stability evaluation and preventive scheduling in power systems offer many challenges i... more Real-time stability evaluation and preventive scheduling in power systems offer many challenges in a stressed power system. Trajectory Sensitivity Analysis (TSA) is a useful tool for this and other applications in the emerging smart grid area. In this chapter, we outline the basic approach of TSA, to extract suitable information from the data and develop reliable metrics or indices to evaluate proximity of the system to an unstable condition. Trajectory sensitivities can be used to compute critical parameters such as clearing time of circuit breakers, tie-line flow, etc. in a power system by developing suitable norms for ease of interpretation. The TSA technique has the advantage that model complexity is not a limitation, and the sensitivities can be computed numerically. Suitable metrics are developed from these sensitivities. The TSA technique can be extended to do preventive rescheduling. A brief discussion of other applications of TSA in placement of distributed generation is indicated.

International Journal of Control, 1974

... 1. Introduction The effect of flux-decay and voltage regulator action on the transient stabil... more ... 1. Introduction The effect of flux-decay and voltage regulator action on the transient stability of a synchronous generator has been investigated previously (Crary If)47, Kimbark If).56, Demello and Concordia 196fJ, Siddique 1968, Willems If)6fJ, Gupta and Davies 1fJ61, Fallside ...

Transactions of the American Institute of Electrical Engineers, Part II: Applications and Industry, 1963

radius 1/T. The damping ratio is The locus of the zeros is shown in Fig. 31. Note that with suita... more radius 1/T. The damping ratio is The locus of the zeros is shown in Fig. 31. Note that with suitable choice of T and m 2f all left-hand plane locations can be achieved. Right-hand plane locations are achievable only for a small sector, £>-1/2. The authors' Figs. 13, 17, 21, and 23 * So far as the mathematical treatment is concerned, the hold circuit and the nonlinearity can be inter changed as shown in Fig. 1(B).

IEEE International Symposium on Circuits and Systems

It is shown that the maximum loadability of a power system depends on the allocation of load and ... more It is shown that the maximum loadability of a power system depends on the allocation of load and generation. For a given load distribution by percentage and constant power factor, the maximum can be described by a scalar. The maximum value of this scalar depends on the generation scheduling. It is shown how the maximum loadability can be computed when there are no inequality constraints on the generation scheduling, line flows, or bus voltages. As in load flow, the set of nonlinear equations used does not have a unique solution. Further work is needed to see how the initial guess affects the solution

IEEE Power Engineering Review, 1983

ensure the qualification of environmentally qualified, safety-related equipment is performed Phas... more ensure the qualification of environmentally qualified, safety-related equipment is performed Phase consists of the evaluation of a selected subset of the safety-related equipment For this subset the qualification documen tation was reviewed and the maintenance activities that are required to ensure the qualification of the equipment were determined The actual maintenance being performed at the nuclear power plant on the equipment under consideration was determined Based on this information, recommendations were made for im provements and changes The recommendations included 1) Recommendations for incorporating additional maintenance that should be performed to ensure equipment qualification 2) Recommendations to consider deleting unnecessary or re dundant maintenance, or reducing the frequency of main¬ tenance as a result of qualification data 3) Recommendations to revise the maintenance procedures as a result of qualification considerations 4) Recommendations to revise the maintenance procedure to im¬ prove the overall maintenance activity Examples of each kind of recommendation are included A program to evaluate a subset of the safety-related equipment is an effective way to determine what maintenance, ofthat required for equipment qualification, is in place, and to provide the recommen dations for additional maintenance actions to ensure qualification 83 WM 023-9

ISCAS '98. Proceedings of the 1998 IEEE International Symposium on Circuits and Systems (Cat. No.98CH36187)

The development of trajectory sensitivity analysis for power systems is presented in the paper. A... more The development of trajectory sensitivity analysis for power systems is presented in the paper. A hybrid system model which has a differential-algebraic-discrete structure is proposed. Crucial to the analysis is the development of jump conditions describing the behaviour of sensitivities at discrete events, such as switching and state resetting. A power system example which involves a mix of continuous and discrete behaviour is presented to illustrate various aspects of the theory. It is shown that trajectory sensitivities provide insights into system behaviour which cannot be obtained from traditional simulations.

Lecture Notes in Computer Science, 2006

In operations, simulation and control of power systems, the presence of real-time data relating t... more In operations, simulation and control of power systems, the presence of real-time data relating to system states can yield precise forecasts and can enable robust active control. In this research we are developing efficient and robust methods to produce "data enhanced" reduced order models and filters for large-scale power systems. The application that this paper focuses on is the creation of new data-driven tools for electric power system operation and control. The applications systems include traditional SCADA systems as well as emerging PMU data concentrators. A central challenge is to provide near real-time condition assessment for "extreme events," as well as long-term assessment of the deterioration of the electrical power grid. In order to provide effective guidance for power system control, we are also developing visualization methods for integrating multiple data sets. These visualization methods provide an up-to-date view of the system state, and guide operatorinitiated power system control.

2002 IEEE Power Engineering Society Winter Meeting. Conference Proceedings (Cat. No.02CH37309)

Trajectory sensitivities complement time domain simulation in the analysis of large disturbance d... more Trajectory sensitivities complement time domain simulation in the analysis of large disturbance dynamic behaviour of power systems. They are formed by linearization around a nonlinear, and possibly non-smooth, trajectory. The influence of parameter variations on large disturbance behaviour can be estimated (to first order) from these sensitivities. Large (small) sensitivities indicate that a parameter has a significant (negligible) effect on behaviour. These insights are helpful in analysing the underlying influences on system dynamics, and for assessing the significance of parameter uncertainty. Further, trajectory sensitivities provide gradient information for applications such as parameter estimation, boundary value problems, bordercollision bifurcations, and optimal control.

Power Electronics and Power Systems, 2014

The material in this chapter focuses on the relationship between power system dynamic equilibrium... more The material in this chapter focuses on the relationship between power system dynamic equilibrium, power flow, and operating point stability. It addresses issues relating steady-state equilibrium in electric power systems with possible implications about stability of the associated operating point. It presents various connections between dynamic models, dynamic equilibrium, power-flow analysis, and the significance of singularities of Jacobian matrices involved in various computations. It includes advances on earlier work on this subject and provides recent results on computing the equilibrium of “post-contingency” models. These post-contingency models are created to enforce the concept of “constant control inputs” in the steady-state analysis. This impacts subtle things such as post-contingency speed (frequency) and remote voltage regulation. The concepts are illustrated on small system models. Different methods of computation are presented to provide alternatives for possible practical implementation.

Energy Function Analysis for Power System Stability, 1989

An interconnected power system consists of generating units (including turbine-governor and excit... more An interconnected power system consists of generating units (including turbine-governor and excitation systems), transmission lines, loads, transformers (including off-nominal ratio and phase shifting transformers), static var compensators and HVDC lines. The size of the interconnection varies but the technical problems are the same. It is not uncommon for some utilities to study systems which have 10,000 buses. As a rule of thumb about one fourth of these buses will have generators connected. At the planning level, after examining the adequacy of transmission capacity, economy of generation etc., the planner would invariably study the stability of the system for a set of disturbances ranging from the worst, such as three phase to ground fault (whose probability of occurrence is rare) to single phase faults which constitute about 70% of the disturbances. There are good production grade programs which simulate the time behavior of the system for such disturbances. There are literally thousands of variables that can be monitored even on a moderate sized system such as a 500 bus system. The planner wants to see if a fault is properly cleared without the system losing synchronism. A system is said to be synchronously stable (i.e., retain synchronism) for a given fault if the system variables settle down to some steady state values as t → ∞. These simulation studies are called transient stability studies. A typical transient stability study with detailed modeling for a 500 bus 100 machine system might take up to an hour.

International Journal of Electrical Power & Energy Systems, 1996

This paper discusses modelling and theoretical issues associated with voltage and angle stability... more This paper discusses modelling and theoretical issues associated with voltage and angle stability of power systems. A timescale decomposition is performed to illustrate how the critical modes can be identified with reduced-order models and the bifurcation phenomena can be explained with these low order models. Examples are given for single and muhimachine systems.

IEEE Transactions on Power Systems, 1987

Page 1. IEEE Transactions on Power Systems, Vol. PWRS-2, No. 2, May 1987 REDUCED ORDER MODELING O... more Page 1. IEEE Transactions on Power Systems, Vol. PWRS-2, No. 2, May 1987 REDUCED ORDER MODELING OF INTERCONNECTED MULTIMACHINE POWER SYSTEMS USING TIME-SCALE DECOMPOSITION DJ LaGesse S. Ahmed-Zaid MA Pai ...

IEEE Transactions on Power Systems, 2001

In this paper, the traditional AGC two-area system is modified to take into account the effect of... more In this paper, the traditional AGC two-area system is modified to take into account the effect of bilateral contracts on the dynamics. The concept of DISCO participation matrix to simulate these bilateral contracts is introduced and reflected in the two-area block diagram. Trajectory sensitivities are used to obtain optimal parameters of the system using a gradient Newton algorithm.