Qualification: 
M.Tech
d_mahalakshmi@blr.amrita.edu

R. Mahalakshmi currently serves as Assistant Professor (Sr.Gr) the department of Electrical & Electronics, Amrita School of Engineering, Bengaluru campus. She is pursing her Ph.D. in the area of grid connected renewable energy sources. Mahalakshmi  has over seven years of teaching experience. She joined Amrita Vishwa Vidyapeetham in July 2012.

Qualification

YEAR DEGREE UNIVERSITY
2012  M.Tech. Dayananda Sagar college of engineering
2003  B.E. (EEE)   Government college of Engineering,Salem

Publications

Publication Type: Conference Paper

Year of Publication Publication Type Title

2017

Conference Paper

R. Mahalakshmi and Dr. Sindhu Thampatty K.C., “A fuzzy based adaptive controller for grid connected DFIG based windfarm for damping SSR oscillations”, in TENCON 2017 - 2017 IEEE Region 10 Conference, Penang, Malaysia, 2017.[Abstract]


Grid integrated wind energy conversion system is highly known among all renewable energy sources. Grid integrated wind farm undergoes many technical challenges. Wind farms need long transmission line for the grid integration. As long transmission line exhibits high inductive reactance, capacitive series compensation is required to improve the transmission capacity. Insertion of capacitive compensation in a line causes Sub Synchronous Resonance (SSR) Oscillations in the system. These oscillations may lead to a permanent damage in the turbine-shaft system. This paper proposes a novel fuzzy based adaptive controller for Rotor Side Converter (RSC) and Grid Side Converter (GSC) for damping SSR oscillations in a grid connected DFIG based wind farm. The paper describes the development of a mathematical model of the proposed system in detail and small signal stability for SSR oscillations is analyzed using Eigen value approach. Oscillation. Performance of the proposed controller is tested under varying operating conditions and it has been observed that the fuzzy based controller adopts the changes in the system operating conditions and gives satisfactory performance compared with conventional PI controller.

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2017

Conference Paper

R. Mahalakshmi and Dr. Sindhu Thampatty K.C., “Sub-Synchronous Resonance analysis on DFIG based windfarm”, in IEEE Region 10 Annual International Conference, Proceedings/TENCON, 2017, pp. 930-935.[Abstract]


The rapidly growing level of wind energy injection into the grid is insisting the modifications in power system. In order to improve power transfer capability, series capacitive compensation in the transmission line is adopted which leads to Sub Synchronous Resonance (SSR) oscillations. The main objective of this paper is to develop a dynamic model of Doubly Fed Induction Generator (DFIG) based wind farm connected into grid through series compensated transmission line for SSR studies. The small signal stability studies are carried out through Eigen value approach. State space representation of the whole system is developed. Different modes of the systems are identified for different wind speeds and for various series compensation levels.

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2016

Conference Paper

R. Mahalakshmi and Dr. Sindhu Thampatty K.C., “Damping of Sub-Synchronous Oscillations in DFIG Based Wind farms”, in IEEE International Conference TENCON 2016, Singapore, 2016.

2016

Conference Paper

R. Mahalakshmi, Viknesh, J., and,, and Dr. Sindhu Thampatty K.C., “Fuzzy Logic based Rotor Side Converter for constant power control of grid connected DFIG”, in 2016 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES), Trivandrum, India, 2016.[Abstract]


Technological advancements has made production of electrical energy more efficient and minimized the consumption of non-renewable sources of energy. Wind energy has been harvested for more than a decade and has been considered to be one of the cleaner methods of producing electricity. This paper focuses on wind electric system connected to the grid. There are different types of wind electric generators such as fixed speed generators (synchronous generators) and variable speed generators which are squirrel cage and slip ring induction generators. Variable speed induction generators are widely chosen in wind electric system. In variable speed induction generators, doubly fed induction generators are mostly used because its rotor transfers the slip power when there is high wind speed velocity, and voltage is injected if the wind velocity is less. This paper proposes a method for controlling the stator power output of DFIG at speeds below synchronous speed using a novel fuzzy logic controller for Rotor Side Converter(RSC). The fuzzy logic rule base is formulated based on wind turbine speed and it controls the amount of rotor/slip power to be injected at appropriate slip frequency by varying the reference signal of the PWM generator, hence maintains the constant power flow from stator to grid. The fuzzy based RSC controller is designed and implemented in the laboratory.

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2016

Conference Paper

R. Mahalakshmi, Viknesh, J., and Dr. Sindhu Thampatty K.C., “Mathematical modelling of grid connected Doubly Fed Induction Generator based wind farm”, in 2016 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES), Trivandrum, India, 2016.[Abstract]


The day by day increase in electricity demand and depletion of fossil fuels has made the world to think about the renewable energy sources such as solar, wind etc., This paper focuses on the configuration of large Doubly Fed Induction Generator (DFIG) based wind farm connected into the grid. Nowadays DFIGs are more focused in the wind energy conversion systems due to its own advantages. This paper explains the development of a mathematical model of DFIG driven by wind turbine. The turbine generator set is considered as a two mass model and development of the same is discussed. Mathematical modelling of wind turbine, two mass drive train and grid connected DFIG machines are developed by using the dynamic equations. Dynamics of DFIG Rotor Side Converter (RSC) and Grid Side Converter (GSC) are analyzed for further studies with control. The MATLAB simulation results for a 3730W wind farm is explained in this paper, and analyses of various unbalanced conditions on wind farm has been discussed such as rotor short circuit, grid voltage dip and sudden drop in wind speed. Similarly, different rated DFIG machines can be modeled using different machine specifications with the help of developed model.

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2015

Conference Paper

R. Nair, Mahalakshmi, R., and Dr. Sindhu Thampatty K.C., “Performance of three phase 11-level inverter with reduced number of switches using different PWM techniques”, in International Conference on Advancements in Power and Energy (TAP Energy), 2015 , Kollam, 2015.[Abstract]


As compared to conventional inverter topologies like diode clamped and capacitor clamped inverters, the cascaded multilevel inverter has lesser harmonics as well as lower switching stress. The cascaded topology has more number of power switches leading to greater heat losses, larger size, higher cost and more gate drive circuitry. The proposed configuration contains less number of switches and produces lesser harmonics in the output voltage than the cascaded topology. A comparison between four different types of pulse width modulation (PWM) techniques, namely, In-phase disposition (IPD), Anti-phase disposition (APD), Carrier Overlap (CO) and Variable Frequency (VF) PWM methods, has been done. The results have been verified through simulation study in MATLAB/Simulink in order to select the best PWM method that provides minimum THD in the output voltage. An LC filter has been designed to improve the harmonic profile.

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2014

Conference Paper

R. Mahalakshmi, Aswin, K. A., and Kumar, A., “Design of Fuzzy Logic based Maximum Power Point Tracking controller for solar array for cloudy weather conditions”, in 2014 Power and Energy Systems Conference: Towards Sustainable Energy, PESTSE 2014, Bangalore, 2014.[Abstract]


<p>This paper proposes Maximum Power Point Tracking (MPPT) of a photovoltaic system under variable temperature and solar radiation conditions using Fuzzy Logic Algorithm. The cost of electricity from the PV array is more expensive than the electricity from the other non- renewable sources. So, it is necessary to operate the PV system at maximum efficiency by tracking its maximum power point at any weather conditions [1]. Boost converter increases output voltage of the solar panel and converter output voltage depends upon the duty cycle of the MOSFET present in the boost converter. The change in the duty cycle is done by Fuzzy logic controller by sensing the power output of the solar panel. The proposed controller is aimed at adjusting the duty cycle of the DC-DC converter switch to track the maximum power of a solar cell array. MATLAB/Simulink is used to develop and design the PV array system equipped with the proposed MPPT controller using fuzzy logic [2][3]. The results show that the proposed controller is able to track the MPP in a shorter time with less fluctuation. The complete hardware setup with fuzzy logic controller is implemented and the results are observed and compared with the system without MPPT (Fuzzy logic controller). © 2014 IEEE.</p>

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Publication Type: Journal Article

Year of Publication Publication Type Title

2015

Journal Article

R. Mahalakshmi and Dr. Sindhu Thampatty K.C., “Implementation of Grid Connected PV array using Quadratic DC-DC Converter and Single Phase Multi Level Inverter”, Indian Journal of Science and Technology, vol. 8, 2015.[Abstract]


Electrical energy generation from solar and wind is increasing day by day and the extraction of good quality electrical energy effectively as well as efficiently is really challenging. This paper focuses on the extraction of electrical energy from solar cells and interconnecting it to the single phase grid through a Quadratic Buck-Boost Converter (QBBC) and Multi Level Inverter (MLI). MLI uses three DC sources, one of which is derived from the solar array through QBBC with Maximum Power Point Tracking (MPPT) controller. In this paper, a new converter topology which accepts wide variations in input voltage has been designed to produce minimum distortion in MLI output with reduced number of switches. The proposed system is designed and implemented in the laboratory and the output is analyzed in different operating conditions

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2015

Journal Article

R. Mahalakshmi and Dr. Sindhu Thampatty K.C., “ Grid Connected Multilevel Inverter for Renewable Energy Applications”, Procedia Technology, vol. 21, pp. 636 - 642, 2015.[Abstract]


Electrical energy generation from renewable energy sources such as sun, wind etc., are widely adopted due to the increase in electricity consumption. The integration of renewable energy sources with the grid plays an important role in energy utilization. It is difficult to utilize electricity from renewable energy sources directly for the injection of power into the grid. Hence the system needs power electronic converters as an interface between renewable energy sources and grid/load. This paper discusses about the integration of three phase six level voltage source inverter into the grid. Three phase 2000 VA inverter is designed by using three, single phase eight switch six level inverters (in quarter cycle) and each single phase inverter uses three DC voltage sources which can be derived from renewable energy sources such as solar, wind and fuel cell. The pure sinusoidal 415V three phase voltage is obtained from inverter to inject the power into grid and to the three phase resistive load. The proposed three phase Multi Level Inverter (MLI) is compared with the conventional three phase inverter and the observed THD of the conventional MLI is 31%. THD of the proposed MLI output voltage is analyzed which is 0.13% and found to be very less compared to six and 12 pulse conventional converter topologies. The simulation on the proposed inverter topology is done in MATLAB/Simulink and the results are verified. More »»

2015

Journal Article

R. Mahalakshmi, Manjunath, H. V., and Thampatty, K. C. S., “Design and implementation of quadratic buck-boost converter for PV array”, International Journal of Applied Engineering Research, vol. 10, pp. 1023-1034, 2015.[Abstract]


<p>Due to increase in electric energy demand, energy extraction from solar and wind are much concentrated in power electronic systems. There is a wide variation in the output of solar array and it needs efficient DC-DC converter. This paper discusses about the design and implementation of closed loop control of Quadratic buck boost converter for the variable DC input voltage whose voltage ratio is -D2/(1-D)2.This converter uses a single switch to control output voltage unlike cascaded buck and buck boost converters. Cascaded conventional converter uses two switches for the same voltage ratio of -D2/(1-D)2. They also suffer from duty cycle and switching frequency limitations during wide input voltage variations. These problems can be reduced with the help of quadratic converter. In this paper quadratic closed loop control of buck boost converter is proposed for the variable solar panel output. Simulation of the circuit is done using MATLAB simulink and hardware implementation results are discussed. © Research India Publications.</p>

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2012

Journal Article

R. Mahalakshmi and Usha, P., “Simulation Of Vsc Based HVDC Transmission System For The Integration Of Windfarm Into Grid”, International Journal of Electrical and Electronics Engineering (IJEEE), vol. 1, no. 4, pp. 2231 – 5284 , 2012.[Abstract]


Wind energy has huge potential to become major source of renewable energy for the modern world. For integrating wind farms to the AC grid, HVDC transmission systems have several advantages over AC transmission systems. This paper presents the design and control of voltage source converter based HVDC system for integration of wind farms in to AC grid. The designed VSC-HVDC system performance under steady state conditions and various transient conditions are presented. The PSCAD/EMTDC software package is used for the simulation studies.

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