BITS Faculty Publications

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Author: search.filters.author.Bhanot, Surekha

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    A Simple Approach to Improvement in Performance of UPQCDG in presence of Unbalanced Load
    (IEEE, 2017) Bhanot, Surekha; Mathur, Hitesh Datt; Patel, Ashish
    In this paper, an improved Power Angle Control (PAC) method for UPQC-DG has been proposed for effective compensation of unbalanced loads. UPQC-DG provides a simultaneous solution to power quality and renewable integration. PAC methods have been developed for UPQC-DG to enhance VA utilization of series and shunt APFs of UPQC-DG. In case of unbalanced loads, existing PAC methods result in circulation of reactive power and increased VA loading of UPQC-DG. PAC method proposed in this work, is designed to tackle above-mentioned issues. Also, proposed PAC method is based on Synchronous Reference Frame (SRF) theory, which makes it robust to non-ideal voltages. Performance of proposed PAC method has been tested using real time simulation performed in Opal-RT. Simulation results show superior performance of UPQC-DG in presence of unbalanced and non-linear loads using proposed PAC method.
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    A new and simple SRF based power angle control for UPQCdg to integrate solar PV into grid
    (IEEE, 2017) Mathur, Hitesh Datt; Bhanot, Surekha; Patel, Ashish
    In this paper, a new Power Angle Control (PAC) method for Unified Power Quality Conditioner with Distributed Generation (UPQC DG ) is proposed for effective grid integration of solar PV. In UPQC DG shunt Active Power Filter (APF) feeds power from solar PV to load, apart from supplying reactive power demand, leading to increased rating of shunt APF. PAC method aims at effective utilization of series and shunt APFs of UPQC DG to reduce their ratings. In this work a new power angle estimation method based on instantaneous power calculation is proposed. Proposed estimation technique is simple, robust and utilizes already available measurements of UPQC DG . Performance of proposed system is tested in the presence of non-linear and reactive loads with detailed model of solar PV generation system. Dynamic performance of system is studied during grid disturbances such as voltage sag and swell, solar irradiation variation, and change in load. MATLAB/Simulink based simulations validate effectiveness of proposed method.
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    Robust Controller Synthesis for Frequency Regulation in Islanded Microgrid
    (IEEE, 2017) Mathur, Hitesh Datt; Bhanot, Surekha
    Frequency regulation in MG using conventional PID controllers becomes more challenging in the presence of stochastic load and uncertainty in system parameters caused by dynamic perturbation. So, there is a need for a robust controller with acceptable performance and stability for regulating the frequency in MG. The dynamic perturbations include changes in inertia constant and damping coefficient of the power system, which directly affect the frequency of the MG. In this paper, structured H∞ synthesis has been done for robust frequency control in islanded MG. The sources used in MG for compensating the load demand are fuel cell, diesel engine generator and micro-turbine. The robustness and performance of H∞ based controller is validated in the presence of parametric uncertainty and load disturbance caused by stochastic nature of load. The synthesized H∞ based controller is tested for robust stability and performance against ± 50% perturbation of inertia constant and damping coefficient of power system. Simulation results of complete system is also validated with hardware using dSPACE 1104 and control desk
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    Improving Performance of UPQC-DG for Compensation of Unbalanced Loads
    (IEEE, 2018) Mathur, Hitesh Datt; Bhanot, Surekha
    In this paper, an improved Power Angle Control (PAC) method for UPQC-DG has been proposed for effective compensation of unbalanced loads. UPQC-DG provides a simultaneous solution to power quality and renewable integration. PAC methods have been developed for UPQC-DG to enhance VA utilization of series and shunt APFs of UPQC-DG. In case of unbalanced loads, existing PAC methods result in circulation of reactive power and increased VA loading of UPQC-DG. PAC method proposed in this work, is designed to tackle above-mentioned issues. Also, proposed PAC method is based on Synchronous Reference Frame (SRF) theory, which makes it robust to non-ideal voltages. Performance of proposed PAC method has been tested using real time simulation performed in Opal-RT. Simulation results show superior performance of UPQC-DG in presence of unbalanced and non-linear loads using proposed PAC method.
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    Forecast-based modeling and robust frequency control of standalone microgrids considering high penetration of renewable sources
    (Wiley, 2020-12) Bhanot, Surekha; Mathur, Hitesh Datt; Mukherjee, Bijoy Krishna
    This article proposes forecast-based modeling and robust frequency control strat-egy in isolated microgrids (MGs) to improve its stability. The intermittency andvariability in renewable generation is problem for its smooth integration to MGsconsidering frequency stability. Continuous rise in penetration levels of renew-able energy sources (RESs) is the main motivation behind forecast-based model-ing and controller design for MGs. The disturbances that affect the frequency inthe MG may come from the load side and/or the generation sides. In MGs, atthe generation side, the forecast of power from RESs is usually obtained to get arough estimate of available renewable power. The forecasted power always dif-fers from the actual one, so the secondary frequency controller may get over-burdened due to forecast error resulting in abnormal frequency deviation thatmay lead to unstable power system. The proposedH∞based robust controldesign considers the forecast error which improves the system stability and per-formance against disturbances coming from load/generation side.
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    Modified Deloading Strategy of Wind Turbine Generators for Primary Frequency Regulation in Micro-Grid
    (Springer, 2020-04) Bhanot, Surekha; Mathur, Hitesh Datt
    In this work, the contribution of wind turbine generator (WTG) to support micro-grid (MG) during depressed frequency condition has been studied with a modified strategy for improving the primary load frequency response of MG. The majority of existing deloading techniques to estimate the reference power are based on the linear relationship. Hence they are not so accurate to mimic the actual speed versus power dynamics of turbine rotor during deloading operation which is inherently nonlinear in nature. In this work, the existing methods have been analyzed in detail with an aim to improve the performance. Based on the analysis a modified deloading method assuming non-linear relation between rotor speed and power of WTG system has been proposed which shows the improved load frequency response in MG. The proposed deloading technique is simulated and validated using real-time digital simulator (OP4510) for the variation in load and generation inside an islanded MG. The results obtained using modified deloading method are compared with existing deloading method and it is found that proposed deloading method handles the non-linearity of the system during deloading operation and also it contributes more power to MG in response to load demand at the cost of slight increase in the speed of turbine rotor.
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    Enhancing VA sharing between the shunt and series APFs of UPQC with a modified SRF-PAC method
    (Wiley, 2020-02) Mathur, Hitesh Datt; Bhanot, Surekha; Patel, Ashish
    This study proposes a synchronous reference frame (SRF) theory-based modified power angle control (PAC) method for unified power quality conditioner (UPQC). In the steady state of conventional UPQC, shunt active power filter (APF) supplies total reactive power demand, and series APF sits idle, leading to unbalanced VA loading of the two APFs and increase in overall VA rating of UPQC. PAC methods of UPQC have been devised for reducing the unbalance in VA loading of series and shunt APFs of UPQC by sharing reactive load power between the two APFs. SRF-based PAC methods are robust, but existing ones support only small values of power angle, and thereby limit the improvement in unbalance of VA loading of series and shunt APFs. In this work, a modified SRF-PAC method is proposed to support larger values of power angle, to load the two APFs in proportion to their VA ratings and thus yield smaller unbalance in VA loading of the two APFs of UPQC. Also, a modified power angle estimation is proposed to ensure that voltage and VA load on series converter does not go beyond the rated values. Controller hardware in loop simulations and hardware experiments validate the proposed control method.
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    Modeling and frequency control of community micro-grids under stochastic solar and wind sources
    (Elsevier, 2020-10) Bhanot, Surekha; Mathur, Hitesh Datt
    The Community Micro-Grid (CMG) is a coordinated local grid area served by one or more distribution substations supported by local renewable and other distributed energy resources (DER). In an islanded mode, the CMG stability reduces due to low inertia of the equivalent system and stochastic nature of renewable energy sources (RESs). To study the frequency stability of the islanded CMG system, this paper explores the mathematical modeling aspects of different sources in the CMG and the robust control design for the community microgrid model. The robust design using a fixed structure synthesis method has been presented to compensate for the effect of modeling uncertainty. The uncertainty in the CMG model results in parametric perturbation which degrades its performance and stability. This paper explores the existing mathematical models of CMG’s and different control techniques applied for frequency regulation. Robust controller design for CMG is proposed that can handle the stochastic input disturbances like a sudden change in power coming from solar and wind sources and also the model uncertainty that results in the parametric perturbations. The complete model is simulated using MATLAB Simulink platform and results of frequency deviation obtained by robust and PID controller are compared. The controller hardware in loop (C-HIL) validation of the robust control method for CMG has been done using a real-time controller board (DS1104). This CHIL system also implements the CMG plant-controller model and analyzes the frequency deviation against load and renewable power fluctuations. The oscillations in frequency deviation are analyzed for sudden rise or fall in the renewable power coming from the solar and wind sources. A reduction of 30% is achieved in frequency overshoot and settling time using a robust controller than the PID controller. The controller developed and implemented using synthesis has robust stability and performance for the perturbed CMG model and also shows a better time response, unlike the PID controller.
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    Optimum sizing of PV based UPQC-DG with improved power angle control
    (Elsevier, 2020-05) Bhanot, Surekha; Mathur, Hitesh Datt; Patel, Ashish; Yadav, Sisir K.
    Unified power quality conditioner with distributed generation (UPQC-DG) is a solution to the problems of power quality and integration of distributed renewable sources. UPQC, being a combination of series and shunt converters, can compensate for most power quality issues, but the use of two power converters increases the cost, and hence optimal sizing methods have been proposed in the literature. Sizing of UPQC-DG components, however, requires special consideration of power injected by DG. This paper proposes an optimum sizing method for UPQC-DG based on an improved power angle control (PAC) technique, which shares reactive power burden between series and shunt converters. Apart from optimal-sizing, this paper incorporates Volt-Ampere (VA) limits in the PAC method to ensure the operation of converters within designed ratings under all conditions. The performance of the proposed power angle control method has been tested for a case study system using Controller Hardware in Loop (CHIL), implemented with Opal-RT and Dspace/micro-labbox, and has been found superior to existing methods.
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    Frequency regulation in islanded microgrid considering stochastic model of wind and PV
    (Wiley, 2019-05) Bhanot, Surekha; Mathur, Hitesh Datt
    This paper addresses the method of forecasting the wind and solar power and its application to an islanded microgrid (MG) model for load frequency control. Due to high penetration of renewable energy sources, the islanded MG suffers from lower equivalent inertia. The islanded MG faces several challenges in order to ensure the stable operation by maintaining the frequency and voltage at nominal value. The supply and demand power mismatch is mainly due to continuously changing solar irradiance, fluctuating wind speed, variable inertia, and load fluctuations. The intermittent nature of RESs can significantly affect the system stability; hence, the challenge lies in accurate forecasting of power from the renewable energy sources (RESs) so that a proactive arrangement is made available for compensation of active power or frequency variations. The forecasting will determine the correct estimate of power availability so that the power reserves can be activated prior to large variations in active power affecting the stability of the MGs. To address these challenges, a stochastic model of wind and solar has been developed using “Time series modeling” of the data obtained from Charanka Solar Park under Gujarat Energy Development Agency, India. Wind and solar power availability are forecasted using autoregressive integrated moving average (ARIMA) method including the seasonality factor. The proportional and integral (PI) controller is used for regulating the frequency fluctuations caused due to intermittency in the output of RESs and load power. Various load patterns are applied to the MG model to analyze its load frequency behavior along with variations in secondary sources.