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Greater Noida, India

Vidyanandan K.V.,NTPC Ltd. | Senroy N.,Indian Institute of Technology Delhi
IET Generation, Transmission and Distribution

This study presents a control strategy for the frequency regulation in a wind-diesel powered microgrid. With wind as a major energy resource, ensuring reliability and quality of power supplied in the system is a great challenge. To reduce the adverse effects caused by wind's variability, intermittency and uncertainty on the system frequency and improve the performance of diesel generator (DG), a solution is explored that involves the use of two different energy storage technologies. A test system is proposed consisting of a wind farm and a DG, supplemented by hydrogen storage with fuel cell (FC) as a long-term and a flywheel (FW) as a short-term energy storage. During low demand or high wind periods, the surplus energy generated is stored as kinetic energy in the FW and as hydrogen gas after water electrolysis. During periods of low wind speed or increased demand, the FW supplies energy by shedding its rotor speed and hydrogen is converted into electricity through the FC. The effectiveness of adding a short-term and a long-term energy storage in enhancing the robustness of wind-diesel system is demonstrated in this study. © The Institution of Engineering and Technology. Source

Kundu G.K.,NTPC Ltd. | Mishra B.B.,Utkal University
Energy Policy

Orissa is the first state in India to have undergone reform in the power sector, with the government withdrawing its control. The model of this reform is known as the WB-Orissa model. The goal of this paper is to examine the impact of this reform on consumers of electricity, which has been measured using multiple regression models. The variables represent the parameters that consumers are most interested in, and the regression coefficients represent the weights of the corresponding variables. The data were collected using a survey methodology. The impact of reform was found to be mixed. Some groups of consumers saw benefits, while others felt a negative impact. A focus group study was conducted to identify the variables of interest to consumers of electricity. The model was used to estimate consumer benefit and was validated using primary data and structural equation modeling. The study revealed beneficial aspects of reform and areas with no benefits. © 2011 Elsevier Ltd. Source

A new topology for the single-stage grid connection of Photovoltaic (PV) system is proposed in this paper. PV inverters of various types have been proposed previously. Modular multilevel inverter, MMI(HB) using half-bridge submodules is recent and a potential candidate for PV application. Conventionally, the DC link of MMI has a centralized large DC source e.g. PV system connected across it. In the proposed topology, distributed PV system e.g. PV strings/arrays are connected directly across dc link of MMI(HB) submodules (SMs). This allows easy expansion, independent monitoring of each PV string voltage and maximum power point optimization. The dynamics of PV generator is different from the conventional power generator, hence, a new combination of MPPT and decoupled dq controller is proposed to maximize the real power output from the PV strings and limit reactive power exchange with the grid as per the system requirements. In order to validate the proposed concept of new single-stage grid connected PV topology and its controller, simulations were conducted. A detailed model of the proposed 1800W, PV system consisting of 36 PV modules connected across a 13 level three phase MMI (HB) was established. The simulation results of new PV system during fast changes in solar irradiation and reactive power exchange has confirmed the feasibility of proposed MMI(HB) interface for single-stage grid connected high voltage, high power PV system and has verified the validity of the control strategy adopted. Source

Ray T.K.,NTPC Ltd. | Ganguly R.,Jadavpur University | Gupta A.,Jadavpur University
Energy Conversion and Management

Steam temperatures in large capacity boilers of modern electric power stations are maintained closely around the design specification by spraying water in the superheater (SH) attemperator to ensure safe and efficient operation and long plant life. Although the process of attemperation involves exergy destruction, and optimal controllers have previously been proposed for steam temperature control, prior studies on such controllers have not considered exergy as an important parameter. Exergy analysis of a two-stage SH attemperator with real time operation parameters in a 500 MWe pulverized fuel fired power plant pinpoints the avenues for optimization that is beyond the scope of the traditional First-Law based analysis. Strategies to minimize exergy destruction by suitably varying the proportions of stage I and stage II spray flows are established. Further, a MATLAB-SIMULINK-based model is developed and optimal control strategies are devised for SH steam temperature control following a Linear Quadratic Regulator (LQR) approach. Variation of the process parameters and the exergy destructions during the transient operations of the attemperator under stipulated disturbances have been analyzed using the model, with different values of the controller parameters. Guidelines are formulated for the spray flow controller tuning so that the total exergy destructions during the system transients are minimized. © 2012 Elsevier Ltd. All rights reserved. Source

Vidyanandan K.V.,NTPC Ltd. | Senroy N.,Indian Institute of Technology Delhi
IEEE Transactions on Power Systems

This paper introduces a method to improve the primary frequency contribution of grid connected variable speed wind turbine generators (WTGs). Using their energy reserve margins, deloaded WTGs are controlled to provide relief to the grid during depressed frequency conditions. The frequency support from individual WTGs is regulated based on the available reserve, which depends on the prevailing wind velocities. By continuously adjusting the droop of the WTG in response to wind velocities, its primary frequency response is significantly improved in terms of reduced stresses on WTGs during low wind speeds. The impact of variable droop operation on two aspects of WTG operation is investigated-primary frequency contribution and smoothening power fluctuations caused due to changes in wind speed. Also highlighted is the usefulness of this control when adopted by wind farms. © 2012 IEEE. Source

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