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Papers by Rajeev Gajbhiye

We propose an integer linear programming (ILP) formulation for the minimum relay break point set ... more We propose an integer linear programming (ILP) formulation for the minimum relay break point set (BPS) computation. Subsequently, in the ILP framework, we propose an alternate maximum-independent relay BPS formulation with the intention of minimizing dependency within the BPS. We show that 1) in practice, the relaxed version of the ILP suffices to obtain an integral vertex and 2) the relaxed version of the ILP can be efficiently solved by the dual-simplex method. The performance of the proposed algorithm is compared and contrasted with existing algorithms. Case studies on various test systems show the efficacy of the proposed approach.

Linear state estimation through wide area monitoring of power systems using synchrophasors is one... more Linear state estimation through wide area monitoring of power systems using synchrophasors is one of the standard application. There are several ongoing projects throughout the world that utilize WAMS technology for performing state estimation for high voltage transmission network. Successful deployment of state estimation requires reliable PMU streaming data and transmission system network static information. A good database building is necessary to handle the mapping of PMU data with power system information. This paper discusses the development of a commissioning and diagnostic tool during deployment of linear state estimation tool. Important features of the diagnostic tool developed to aid the commissioning in a control center environment are presented. Results of error identification on a practical system and improvements in state estimation through the tool is presented.

IEEE PES Innovative Smart Grid Technologies, Europe, 2014

2005 International Conference on Future Power Systems, 2005

Coordination of relays in a meshed system is an iterative process. It involves finding a set of b... more Coordination of relays in a meshed system is an iterative process. It involves finding a set of break point relays. In this paper, we propose a new polynomial time approximation algorithm for computation of the minimum break point relay set. In turn, procedure for computation of minimum break point relays requires systematic enumeration of all possible simple loops in the system. Therefore, we also propose a simple method for enumerating all possible loops. The advantages of proposed approach are (1) simplicity and (2) reduced computational complexity. Case studies on various topologies demonstrate the utility of the proposed approach.

2009 6th International Conference on the European Energy Market, 2009

ABSTRACT

2010 7th International Conference on the European Energy Market, 2010

ABSTRACT

IEEE Transactions on Power Systems, 2000

This paper proposes an expert system approach to short-term expansion planning (STEP). The rules ... more This paper proposes an expert system approach to short-term expansion planning (STEP). The rules which drive STEP can be classified into MW, MVAR, and ampacity management rules. MW and ampacity management rules are for alleviating transmission line congestion. Reactive power management is required for voltage control at load busses, conformity to the capacity curve of the generators, and containing the MW losses within acceptable limits. Embedding reactive power management in STEP is a challenging task since ac load flow may not converge in absence of proper reactive power planning and load modeling. Therefore, we also propose enhancements to the fast decoupled load flow algorithm for on-the-fly reactive power management. The enhanced algorithm not only can detect divergent load flow scenarios but also self-correct it by restarting the whole process with greater degree of freedom in reactive power controls. The proposed approach leads to development of an automated tool for STEP which has the capability to work, even with incomplete information. A simple method for evaluating location and requirement of shunt reactor is also proposed. By analysis and comparative evaluation, we show that the proposed system can arrive at a solution which is close to optimal. Results on the Western Regional Grid of India with an approximate load of 28 000 MW and 1200 nodes are presented to demonstrate effectiveness of the proposed approach.

IEEE Transactions on Power Delivery, 2000

This paper addresses various aspects of optimal phasor measurement unit (PMU) placement problem. ... more This paper addresses various aspects of optimal phasor measurement unit (PMU) placement problem. We propose a procedure for multistaging of PMU placement in a given time horizon using an integer linear programming (ILP) framework. Hitherto, modeling of zero injection constraints had been a challenge due to the intrinsic nonlinearity associated with it. We show that zero injection constraints can also be modeled as linear constraints in an ILP framework. Minimum PMU placement problem has multiple solutions. We propose two indices, viz, BOI and SORI, to further rank these multiple solutions, where BOI is Bus Observability Index giving a measure of number of PMUs observing a given bus and SORI is System Observability Redundancy Index giving sum of all BOI for a system. Results on IEEE 118 bus system have been presented. Results indicate that: 1) optimal phasing of PMUs can be computed efficiently; 2) proposed method of modeling zero injection constraints improve computational performance; and 3) BOI and SORI help in improving the quality of PMU placement. Index Terms-Integer linear programming (ILP), optimal phasor placement (OPP), phasor measurement unit (PMU), zero injection measurement.

Analysis of faulted power systems in 3-phase coordinates is desirable when dealing with unbalance... more Analysis of faulted power systems in 3-phase coordinates is desirable when dealing with unbalanced networks and complex faults. Thevenin's model in 3-phase domain is well-known for shunt faults. However, lack of generic circuit model for series and simultaneous faults is an impediment, as it sacrifices both simplicity and computational efficiency. In this paper, we extend this approach to arbitrarily complex

IEEE Transactions on Power Systems, 2010

Power flow tracing has been suggested as an approach for evaluating 1) transmission system usage ... more Power flow tracing has been suggested as an approach for evaluating 1) transmission system usage (TSU) cost and 2) loss (MW) cost for generator and load entities in the system. Recently, optimal power flow tracing methods have been proposed to “explicitly” model fairness constraints in the tracing framework. This paper, further, strengthens the tracing-compliant min-max fair cost allocation approach. The

We propose an integer linear programming (ILP) formulation for the minimum relay break point set ... more We propose an integer linear programming (ILP) formulation for the minimum relay break point set (BPS) computation. Subsequently, in the ILP framework, we propose an alternate maximum-independent relay BPS formulation with the intention of minimizing dependency within the BPS. We show that 1) in practice, the relaxed version of the ILP suffices to obtain an integral vertex and 2) the relaxed version of the ILP can be efficiently solved by the dual-simplex method. The performance of the proposed algorithm is compared and contrasted with existing algorithms. Case studies on various test systems show the efficacy of the proposed approach.

Linear state estimation through wide area monitoring of power systems using synchrophasors is one... more Linear state estimation through wide area monitoring of power systems using synchrophasors is one of the standard application. There are several ongoing projects throughout the world that utilize WAMS technology for performing state estimation for high voltage transmission network. Successful deployment of state estimation requires reliable PMU streaming data and transmission system network static information. A good database building is necessary to handle the mapping of PMU data with power system information. This paper discusses the development of a commissioning and diagnostic tool during deployment of linear state estimation tool. Important features of the diagnostic tool developed to aid the commissioning in a control center environment are presented. Results of error identification on a practical system and improvements in state estimation through the tool is presented.

IEEE PES Innovative Smart Grid Technologies, Europe, 2014

2005 International Conference on Future Power Systems, 2005

Coordination of relays in a meshed system is an iterative process. It involves finding a set of b... more Coordination of relays in a meshed system is an iterative process. It involves finding a set of break point relays. In this paper, we propose a new polynomial time approximation algorithm for computation of the minimum break point relay set. In turn, procedure for computation of minimum break point relays requires systematic enumeration of all possible simple loops in the system. Therefore, we also propose a simple method for enumerating all possible loops. The advantages of proposed approach are (1) simplicity and (2) reduced computational complexity. Case studies on various topologies demonstrate the utility of the proposed approach.

2009 6th International Conference on the European Energy Market, 2009

ABSTRACT

2010 7th International Conference on the European Energy Market, 2010

ABSTRACT

IEEE Transactions on Power Systems, 2000

This paper proposes an expert system approach to short-term expansion planning (STEP). The rules ... more This paper proposes an expert system approach to short-term expansion planning (STEP). The rules which drive STEP can be classified into MW, MVAR, and ampacity management rules. MW and ampacity management rules are for alleviating transmission line congestion. Reactive power management is required for voltage control at load busses, conformity to the capacity curve of the generators, and containing the MW losses within acceptable limits. Embedding reactive power management in STEP is a challenging task since ac load flow may not converge in absence of proper reactive power planning and load modeling. Therefore, we also propose enhancements to the fast decoupled load flow algorithm for on-the-fly reactive power management. The enhanced algorithm not only can detect divergent load flow scenarios but also self-correct it by restarting the whole process with greater degree of freedom in reactive power controls. The proposed approach leads to development of an automated tool for STEP which has the capability to work, even with incomplete information. A simple method for evaluating location and requirement of shunt reactor is also proposed. By analysis and comparative evaluation, we show that the proposed system can arrive at a solution which is close to optimal. Results on the Western Regional Grid of India with an approximate load of 28 000 MW and 1200 nodes are presented to demonstrate effectiveness of the proposed approach.

IEEE Transactions on Power Delivery, 2000

This paper addresses various aspects of optimal phasor measurement unit (PMU) placement problem. ... more This paper addresses various aspects of optimal phasor measurement unit (PMU) placement problem. We propose a procedure for multistaging of PMU placement in a given time horizon using an integer linear programming (ILP) framework. Hitherto, modeling of zero injection constraints had been a challenge due to the intrinsic nonlinearity associated with it. We show that zero injection constraints can also be modeled as linear constraints in an ILP framework. Minimum PMU placement problem has multiple solutions. We propose two indices, viz, BOI and SORI, to further rank these multiple solutions, where BOI is Bus Observability Index giving a measure of number of PMUs observing a given bus and SORI is System Observability Redundancy Index giving sum of all BOI for a system. Results on IEEE 118 bus system have been presented. Results indicate that: 1) optimal phasing of PMUs can be computed efficiently; 2) proposed method of modeling zero injection constraints improve computational performance; and 3) BOI and SORI help in improving the quality of PMU placement. Index Terms-Integer linear programming (ILP), optimal phasor placement (OPP), phasor measurement unit (PMU), zero injection measurement.

Analysis of faulted power systems in 3-phase coordinates is desirable when dealing with unbalance... more Analysis of faulted power systems in 3-phase coordinates is desirable when dealing with unbalanced networks and complex faults. Thevenin's model in 3-phase domain is well-known for shunt faults. However, lack of generic circuit model for series and simultaneous faults is an impediment, as it sacrifices both simplicity and computational efficiency. In this paper, we extend this approach to arbitrarily complex

IEEE Transactions on Power Systems, 2010

Power flow tracing has been suggested as an approach for evaluating 1) transmission system usage ... more Power flow tracing has been suggested as an approach for evaluating 1) transmission system usage (TSU) cost and 2) loss (MW) cost for generator and load entities in the system. Recently, optimal power flow tracing methods have been proposed to “explicitly” model fairness constraints in the tracing framework. This paper, further, strengthens the tracing-compliant min-max fair cost allocation approach. The