Subrata Paul

Design of robust Power System Stabilizer using H∞ mixed sensitivity technique

The use of Power System Stabilizers (PSS) to improve the dynamic stability of power system is not a new idea. Present day complexity in power system demands PSS must be robust enough to ensure adequate system performance over a wide range of system operating conditions to come out from the problem of oscillatory instability. H2 and H∞ Norm based robust control techniques have now been developed and are being used for the controller design in power system. This paper deals with design of PSS using weighted mixed sensitivity H∞ robust control theory. The effectiveness of the power system stabilizer designed through this method is demonstrated by simulation of a sample power system for various load conditions using MATALB.

A simple algorithm for distribution system load flow with distributed generation

With increasing penetration of distributed generators (DG) in power distribution system, the distribution system load flow methods also need to be modified. Hence, the selection of suitable model of DG is important for the accurate load flow. In this paper, a simple algorithm for distribution system load flow with DG is proposed considering DGs as constant negative loads. The results for three test distribution systems are presented.

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.

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.

Active Loss Allocation Systems in Radial Distribution Systems

ABSTRACT In the restructured power system under deregulation, proper pricing of electricity has emerged as a key issue. The cost of transmission and distribution activities needs to be allocated to the users of these networks. Among others, power losses are one of the costs to be allocated. The main difficulty faced in allocating losses is the nonlinearity between the losses and delivered power which complicates the impact of each user on network losses. The purpose of this article is to review the various loss allocation schemes as applicable to the distribution systems. These schemes have been compared considering a simple radial distribution system. Since cogeneration and distributed generation (DG) plants often generate power for on-site consumption, and a fraction of the output is for export to the grid, developers of cogeneration and DG with substantial on-site consumption can realize significant savings in transmission and distribution losses. Thus, the schemes discussed herein can help a cogenerat...

Impact analysis of wind power integration in existing power systems for study of voltage stability conditions

Voltage stability conditions during normal operation of existing grids is primarily governed by conventional reactive power management. However, during wind power integration, the integrated system behaves erratically causing lots of concern to the grid operators in evacuating the available power from the wind farms. The major thrust in this paper is to study the impact of voltage stability conditions in existing grid arising out of additional wind power integration. This has been performed by monitoring voltage deviation and L-index at critical buses in the pre-integration and post-integration stages. It is observed that consistency of critical bus bars in terms of location and criticality is largely affected due to the combined actions of load variation and degree of wind power penetration. This has been justified through simulation results of IEEE 30-bus test system and Indian 28-bus system. Further, the results emphasize the need for a rigorous reactive power planning for safe and reliable evacuation of wind power through the existing grid.

Optimal size and location of Distributed Generation and KVAR support in unbalanced 3-Φ distribution system using PSO

This paper proposes a Particle Swarm Optimization based methodology for finding Optimal size and location of Distributed Generation and unbalanced Reactive power support for unbalanced three phase distribution network. The improvement in voltage profile and loss saving are presented. The proposed technique is tested on IEEE 37 node radial test feeder which is an actual feeder in California. The program is developed using MATLAB programming software. The results obtained show the effectiveness of the method for unbalanced network.

On-line voltage stability assessment in the presence of TCSC with economic consideration

In modern power system operation the optimization problem and voltage stability problem are two interrelated issues. This paper presents a new methodology to assess system voltage stability status combined with optimal power flow technique using instantaneous two-bus π-equivalent model of a power system at different operating conditions. Thyristor controlled series compensator (TCSC), one of the popularly used FACTS controllers has also been modelled and included in the analysis to simulate a power system in more practical way. The developed methodology has an essence of on-line application which has been illustrated here with a standard IEEE 57-bus power system.

Robust power system stabilizer design using PSO based DK iteration

Power system stabilizer (PSS) is used to enhance damping to the generators electromechanical oscillations. Here in a μ-optimum controller has been constructed using PSO based DK-iteration. The controller designed using this method represents the combination of μ-analysis which ensures parametric uncertainties and H∞ synthesis which takes care of robustness. This robust control technique has been applied for determine a controller which reduces the peak value over frequency of the upper bound, namely μ. A μ-optimum controller has been designed where the parametric uncertainty is less than one. A robust power system stabilizer (RPSS)has been designed by simulation of a simple single machine associated with infinite bus system at different loading conditions using MATLAB. The proposed controller shows good damping performance for all conditions.

PSO based robust power system stabilizer design using H ∞ loop shaping technique

Power system stabilizer (PSS) is used to provide damping to the generators oscillations. The damping is achieved through modulation of generators excitation so as to provide adequate electrical torque to the rotor speed deviations. In this paper a particle swarm optimization (PSO) based robust power system stabilizer design using H∞, loop shaping technique is reported. Weighting function selection and the lead lag compensator based controller parameters has been designed using PSO algorithm. This design is based upon normalized coprime factorization H∞ loop shaping technique by McFarlane-Glover. The efficacy of robust power system stabilizer (RPSS), designed through this method has been demonstrated by simulation of a simple single machine infinite bus (SMIB) system for various loading conditions using MATLAB.