Subir Sen

Optimal thermal generating unit commitment: a review

Abstract The purpose of economic thermal unit commitment scheduling is to minimize the cost of operation subject to attainment of a certain level of security and reliability. However, in recent years, owing to environmental considerations, operation at absolute minimum cost cannot be the only objective/basis of optimal thermal unit commitment. The environmental effect of thermal power generation is also becoming a major concern in most countries. This paper first introduces the general unit commitment scheduling problem and then discusses various considerations, objective functions and different techniques to solve the problem. A brief critical representative survey of the existing literature available on this topic is presented. Finally, recent trends in research on unit commitment are also discussed.

EHV transmission line capacity enhancement through increase in surge impedance loading level

The quantum of power that a given EHVAC transmission line can safely carry depends on various limits. These limits can be categorized into two types viz. thermal and stability/SIL limits. In case of long lines the capacity is limited by its SIL level only which is much below its thermal capacity due to large inductance. Decrease in line inductance and surge impedance shall increase the SIL and transmission capacity. This paper presents a mathematical model of increasing the SIL level towards thermal limit. Sensitivity of SIL on various configuration of sub-conductors in a bundle, bundle spacing, tower structure, spacing of phase conductors etc. is analyzed and presented. Various issues that need attention for application of high surge impedance loading (HSIL) line are also deliberated

Optimization of neutral grounding reactor parameters-an analysis for a double circuit EHV line

In order to maintain power transmission reliability, application of single-phase switching (SPS) and auto-reclosing on EHV line is a common practice. However, in some cases, it is necessary to apply special means like neutral grounding reactor (NGR) to improve the conditions for secondary arc extinction for successful auto-reclosing. This paper presents importance of various parameters in optimization of NGR in a double circuit (D/c) EHV line. In case of SPS on D/c line, the secondary arc is maintained not only by the inter-phase coupling of the faulted circuit but also by the mutual coupling of the other healthy circuit. An empirical formula for NGR value of a double circuit line along with the methodology for its optimization is presented. Magnitude of secondary arc current also depends on the line length, power flow, source strength etc. Sensitivity of various parameters on secondary arc current has been demonstrated through EMTP study

Control strategy for Frequency Regulation using Battery Energy Storage with optimal utilization

Increasing penetration levels of Renewable Energy Sources (RES) into the grid has raised several concerns due to the intermittency, variability and uncertainty in power outputs. Technological advancements are required to tackle the issues of reliability, stability and power quality. Battery Energy Storage Systems (BESS) are widely being tested and have been found useful to address these challenges. This paper discusses the Frequency Regulation (FR) application of BESS. Several control strategies suggested in literature have been simulated for the frequency variations in the Indian scenario and the constraints limiting the utilization have been identified. A new control strategy has been proposed to enhance the usability of BESS for FR in Indian grid. Simulations have been carried out on MATLAB/Simulink platform and the results validate the advantages of the new control strategy over the existing ones.

An Equivalencing Technique for Solving the Large-Scale Thermal Unit Commitment Problem

This chapter presents a new efficient solution approach for solving the unit commitment schedule of thermal generation units of a realistic large scale power system. We base the approach on cardinality reduction by the generator equiva-lencing concept. This concept reduces the number of units in the large-scale power system to the lowest possible number based on the units’ fuel/generation cost and other physical characteristics, such as minimum up and down time, etc. with units having similar (almost the same) characteristics form one group. The reduced system consists of only each group of representative units and is first solved by the modified dynamic programming technique (one of the new solution methods developed by the authors). Another option is to use any of the standard unit commitment solution techniques. We obtain the overall solution to the original unit commitment problem of the entire system by un-crunching the solved reduced system based on certain rules. This chapter also presents test results for real-life systems of up to 79 units and comparisons with results obtained using Lagrangian relaxation and truncated dynamic programming (DP-TC).

Solar photovoltaic output smoothing: Using battery energy storage system

Battery Energy Storage System (BESS) is widely being implemented along with Solar PV to mitigate the inherent intermittencies of solar power. Solar smoothing is one such application of BESS. In this paper, different techniques for solar power smoothing is compared. An energy compensation based smoothing technique is proposed in this paper. The smoothing method not only ensures an optimal sizing of the battery but also keeps the state of charge of the battery same at the beginning and end of any random day. The different techniques are simulated on a typical moving cloud day output of a 5 MWp solar power-plant.

Energy Efficiency — Potential solution for bridging demand supply gap

India has witnessed phenomenal growth in power sector. Installed capacity stands today is about 250GW resulting in per capita energy consumption more than 900 units. However, high GDP growth is coupled with increasing demand for electricity. There is an energy shortage of about 4.3% and peak of 5.4%. Several initiatives have been made to bridge the demand supply gap by Government of India in the past. Increasing capacity addition and renewable energy has helped in large way. It is estimated by Ministry of Power, GoI that about 23% of energy can be saved by adopting energy efficiency across all energy users. This necessitates identification of areas for energy conservation through energy audits as well as implementation of energy efficiency measures. Power Grid Corporation has surveyed the potential in various areas and combined with the experience in audit of energy intensive industries as well as other commercial establishments brings out the practical view point to adopt energy efficiency that are discussed in this paper.

Advanced metering infrastructure analytics — A Case Study

Advanced Metering Infrastructure (AMI) is the basic building block for development of Smart Grid in Distribution System. The main purpose of AMI is to enable two way communication between consumer and Smart Grid Control Center of Utility which involves remote monitoring & control of energy consumption as well as other parameters in real time. Meter data analytics play a vital role in AMI system which helps utility to manage their resources and business process efficiently. Indigenously developed meter data analytics such as meter data validation, energy audit & accounting of distribution transformer, missing information, peak demand identification, consumer profile analysis, load forecasting, abnormal energy pattern analysis etc. which helps utilities through improved visualization and enhanced situational awareness. These would also help in providing better QoS to consumers as well as empower them for better energy management. This paper presents several analytics developed on smart meter data as part of AMI implemented in Puducherry Smart Grid Pilot Project.

Smart grid development in India — A case study

Consistent high growth of Indian economy has resulted in a surging demand for energy. Since, independence Indian power system has grown from 1362 MW to 250GW. In the past decade, installation of renewable sources of energy for electricity has grown at an annual rate of 25%, which has reached 29,500 MW as on March 2014. Despite this, presently 400 million people in the country have no access to electricity and hundreds of millions get electricity for only a few hours. Distribution system is suffering from frequent and long duration outages. To supplement capacity addition as well as electrification of remote areas, development of micro-grid also needs attention. Standalone/decentralized micro grid can provide basic energy access to all. Presently, high AT&C losses of utilities are resulting into poor financial health of distribution utilities across the country. To address these issues and bring efficiency, seamless integration of emerging technologies in the field of monitoring, automation, control, communication and IT systems with active participation of all stakeholders are inevitable. It is expected that the far-reaching goals of modern Indian power system can be achieved by deployment of smart grids which can help to improve efficiency of Indian power sector. In this direction, several initiatives have been taken to implement smart grid in entire supply value chain - generation, transmission distribution and consumer participation in power sector. This paper presents initiatives taken by Power Grid Corporation of India Ltd. (POWERGRID) to implement Smart Grid in Indian Power System as a case study on Puducherry Smart Grid Pilot Project.

Environment Friendly Thermal Power Dispatch: An Approach

This article describes an approach for optimal emission power dispatch from thermal power plants with optimal operating cost. The proposed approach, called economic-emission dispatch, is based on a λ-iteration technique including penalty on emissions. Sample case studies with a system of three generating units are discussed.