Sunita Halder nee Dey

Development of a global voltage security indicator (VSI) and role of SVC on it in longitudinal power supply (LPS) system

Abstract In this article a concept of ‘global voltage security indicator’ of an interconnected power transmission network being introduced, a generalized algorithm has been developed on the basis of Newton–Raphson load flow method for system simulation. The indicator demonstrates that the magnitude of global stability can be ascertained on off line basis for any variation of load in an interconnected network. The developed method has been applied for a typical longitudinal power supply network taking into account the line resistance, line reactance and shunt susceptance in order to assess the global voltage security. Improvement in global voltage security has also been highlighted with the application of a static var compensator in a typical ‘weak’ load bus in that system.

Real coded chemical reaction based optimization for short-term hydrothermal scheduling

The paper solved different short term hydro thermal scheduling (STHS) problems.The paper considered both small and large size test systems.Real coded chemical reaction optimization (RCCRO) is applied to solve the problem.Performance of RCCRO has been compared with different PSO, DE, modified DE, etc.Performance of RCCRO has been found to be more encouraging to solve STHS problems. This paper presents a real coded chemical reaction based (RCCRO) algorithm to solve the short-term hydrothermal scheduling (STHS) problem. Hydrothermal system is highly complex and related with every problem variables in a nonlinear way. The objective of the hydro thermal scheduling is to determine the optimal hourly schedule of power generation for different hydrothermal power system for certain intervals of time such that cost of power generation is minimum. Chemical reaction optimization mimics the interactions of molecules in term of chemical reaction to reach a low energy stable state. A real coded version of chemical reaction optimization, known as real-coded chemical reaction optimization (RCCRO) is considered here. To check the effectiveness of the RCCRO, 3 different test systems are considered and mathematical remodeling of the algorithm is done to make it suitable for solving short-term hydrothermal scheduling problem. Simulation results confirm that the proposed approach outperforms several other existing optimization techniques in terms quality of solution obtained and computational efficiency. Results also establish the robustness of the proposed methodology to solve STHS problems.

OPF based voltage stability assessment of a multi-bus power system using network equivalencing technique

In this paper a unique methodology for assessment of voltage stability is proposed considering economic criteria using the concept of equivalencing the multi-bus system to a two bus radial system and by studying the necessary parameters of the equivalent system. Hence, a generalized global voltage stability indicator being developed, it has been applied to a typical 6-bus system and a practical 203-bus WBSEB system. Test results have proved that this new network equivalent method is promising for voltage stability study of power system in global scenario and is applicable to any multi-bus power network.

A comparative study in improvement of voltage security in a multi-bus power system using STATCOM and SVC

In this paper an effort is made to assess local and global voltage security of multi-bus power system in presence of STATCOM and SVC. A Global Voltage Security Indicator (GVSI) derived from series network equivalent of multi-bus power system has been employed to assess overall system voltage security. Thevenins equivalent of the power system with respect to a particular load bus has been used to assess the local voltage security. A comparative study on effectiveness of STATCOM and SVC in improvement of voltage security using network equivalents has also been presented and validated using the well known L-index. STATCOM found to be more effective than SVC to ensure voltage security and at the same time it is also capable to reduce reactive power line loss considerably.

Elimination of partial overloading of generators under unbalanced operating conditions of power systems

Unbalanced operating condition in a power system can cause partial overloading of the generators in the network, a condition where one or two of the three phases of the generator become overloaded even if the total 3-phase power output of the generator is within its specified limit. Partial overloading of generators beyond certain limits is undesirable and must be avoided. Distribution systems are often subjected to highly unbalanced operating conditions. Introduction of distributed generations (DGs), therefore, has rendered todays distribution systems quite susceptible to this problem. Mitigation of this problem requires the issue to be addressed properly during analysis, operation and planning of such systems. Analysis, operation and planning of power networks under unbalanced operating condition require 3-phase load flow study. The existing methods of 3-phase load flow are not equipped to take into account any limit on the loadings of the individual phases of the generators. In the present work, a methodology based on Newton-Raphson (N-R) 3-phase load flow with necessary modifications is proposed. The proposed methodology is able to determine the safe loading limits of the generators, and, can be adopted for operation and planning of power networks under unbalanced operating conditions to overcome the above difficulties. Test results on IEEE-37 bus feeder network are presented to demonstrate the effectiveness of the proposed method.

Reactive power tracing of a multibus power system in presence of SVC

The main objective of this paper is to allocate the reactive power load and loss of any power system network in presence of SVC with consideration of all reactive power resources present in the system. The contribution of each reactive power resources to cater a particular load has been calculated using proportional sharing technique. In addition to that an effort has been made to allocate the reactive loss among the reactive power resources. In this paper, FC-TCR type SVC has been considered to observe its effect on reactive load as well as loss sharing. Proposed technique has been simulated using a 203 bus multi-machine practical power system (WBSEB system). This study can be of great benefit for generating agencies to know the exact reactive loss sharing of a particular generator and therefore to modify the charges applicable for reactive power pricing.

Chemical reaction optimization applied in economic dispatch problems

This paper proposes an effective algorithm called chemical reaction optimization (CRO) in the field of power system to solve economic load dispatch (ELD) problems involving different equality and inequality constraints. Complex constraints like prohibited operating zone and ramp rate limit are also considered. System transmission loss has also been considered in the test system. Chemical Reaction Optimization (CRO) imitates the interaction of molecules in a chemical reaction to reach from a higher energy unstable state to a low energy stable state. Simulation results reveal that the proposed approach does better than modern existing optimization techniques in terms quality of solution obtained and computational efficiency. Results also establish the robustness of the proposed methodology to solve ELD problems.

Emission dispatch solution using biogeography-based optimization with availability of wind power

In this paper a emission dispatch problem is solved to minimize the emission of oxides of nitrogen (NOx), considering both thermal generators and wind power source. Total overall cost of generation is taken as inequality constraint during the time of minimization of emission during optimization process. The effects of wind power to control overall NOx emission from thermal power plants are also investigated here. To find the optimum emission dispatch schedule, authors have applied Biogeography based optimization. Biogeography deals with the geographical distribution of biological species. Mathematical models of biogeography describe how a species arises, migrates from one habitat to another and gets wiped out. The results obtained using BBO show the efficiency of BBO algorithm to solve complex emission dispatch problems.

A novel method to assess global voltage stability of a multi-bus power system

This paper presents a methodology to obtain an equivalent two bus network from a multi-bus network to assess critical loadability in terms of voltage stability. The weakest bus of the system being diagnosed, maximum loadability of the system is obtained for different operating condition. The methodology has also been applied to a six bus power system to assess global voltage stability of the system. The participation of a particular bus in global voltage instability in assesses in terms of global bus voltage collapse coefficient (GVCC) and a global voltage stability indicator (GVSI) has also been developed to assess the global voltage stable state of the total network.