@article{mukherjee_chakrabortty_babaei_2021, title={Modeling and Quantifying the Impact of Wind Penetration on Slow Coherency of Power Systems}, volume={36}, ISSN={["1558-0679"]}, DOI={10.1109/TPWRS.2020.3022832}, abstractNote={This paper presents a mathematical analysis of how wind generation impacts the slow coherency property of power systems. Slow coherency arises from time-scale separation in the dynamics of synchronous generators, where generator states inside a coherent area synchronize over a fast time-scale due to stronger coupling, while the areas themselves synchronize over a slower time-scale due to weaker coupling. This time-scale separation is reflected in the form of a spectral separation in the weighted Laplacian matrix describing the swing dynamics of the generators. However, when wind farms with doubly-fed induction generators (DFIG) are integrated into the system then this Laplacian matrix changes based on both the level of wind penetration and the location of the wind farms. The modified Laplacian changes the effective slow eigenspace of the generators. Depending on the penetration level, this change may result in changing the identities of the coherent areas. We develop a theoretical framework to quantify this modification, and propose an equivalent Laplacian matrix to compute the modified coherent areas. Results are validated using the IEEE 68-bus test system with one and multiple wind farms. The model-based slow coherency results are compared with measurement-based principal component analysis to substantiate our derivations.}, number={2}, journal={IEEE TRANSACTIONS ON POWER SYSTEMS}, author={Mukherjee, Sayak and Chakrabortty, Aranya and Babaei, Saman}, year={2021}, month={Mar}, pages={1002–1012} }
 @article{mukherjee_babaei_chakrabortty_fardanesh_2020, title={Measurement-driven optimal control of utility-scale power systems: A New York State grid perspective}, volume={115}, ISSN={["1879-3517"]}, DOI={10.1016/j.ijepes.2019.105470}, abstractNote={This paper focuses on designing and testing a supplementary controller for an ultra-large, utility-scale power system, namely the New York State (NYS) Power Grid from a completely measurement-based perspective. We present the control design using the Flexible AC Transmission System (FACTS) facility at the NYS grid. We use the utility-scale Eastern Interconnection (EI) model consisting of over 70,000 buses in the PSS/E platform for this research. The coherency structure of the NYS grid is analyzed by performing Principal Component Analysis (PCA) on frequency measurements obtained from multiple contingency simulations. Thereafter, we use the frequency measurements from PMU-enabled buses to identify a reduced-order state space model of the grid such that it matches the input-output characteristics along with identifying the inter-area modes. This model is then used to design the Linear Quadratic Gaussian (LQG) based optimal FACTS controller. Then the controller is implemented in the PSS/E model of the Eastern Interconnection (EI) as a PSS/E-FORTRAN based user defined module. The effectiveness of the control performance is shown using the non-linear simulations under different contingencies provided by the New York Independent System Operator (NYISO).}, journal={INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS}, author={Mukherjee, Sayak and Babaei, Saman and Chakrabortty, Aranya and Fardanesh, Bruce}, year={2020}, month={Feb} }
 @article{babaei_bhattacharya_2015, title={A control structure for PWM-controlled static synchronous compensators under unbalanced conditions and grid faults}, volume={71}, ISSN={["1879-3517"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84925149499&partnerID=MN8TOARS}, DOI={10.1016/j.ijepes.2015.02.035}, abstractNote={Grid connected Voltage Source Converters (VSCs) are the heart of many applications with power quality concerns due to their reactive power controllability. Among the widely used grid-connected applications of the VSCs, the Static Synchronous Compensators (STATCOMs) are commonly used for compensating the voltage quality problems that come from voltage sag and swell. In spite of superior feature of fast voltage regulation and reactive power support functionality, VSC-based STATCOMs have the major drawback of being sensitive to the grid disturbances, especially the unbalanced condition and faults. Moreover, when the STATCOMs are used in the Distributed Generation (DG) applications or reactive power support of the sensitive industrial load, the unbalanced condition becomes even more intolerable. Protection system usually trips due to over current or highly distorted current caused by negative sequence current flow under unbalanced conditions and system faults. This paper propose an alternative control structure to keep the VSC-based STATCOM online during the unbalanced condition and system faults by limiting the negative sequence current. This eliminates the need to redesign/overdesign of the STACOM power components and over rating of the semiconductor switches to operate under fault current. Converter MVA rating reduction will decrease the cost significantly. Proposed controller performance has been verified by simulation and Hardware-In-the-Loop test.}, journal={INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS}, author={Babaei, Saman and Bhattacharya, Subhashish}, year={2015}, month={Oct}, pages={160–173} }
 @article{babaei_parkhideh_chandorkar_fardanesh_bhattacharya_2014, title={Dual Angle Control for Line-Frequency-Switched Static Synchronous Compensators Under System Faults}, volume={29}, ISSN={["1941-0107"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84893954434&partnerID=MN8TOARS}, DOI={10.1109/tpel.2013.2273799}, abstractNote={Voltage-sourced converter (VSC)-based static synchronous compensators (STATCOMs) are used for voltage regulation in transmission and distribution systems. Unlike PWM-controlled STATCOMs, angle-controlled STATCOMs are switched at line frequency to limit the system losses. In recent years, angle-controlled STATCOMs have been deployed by utilities for the purpose of transmission system voltage regulation, voltage stability improvement, and increasing operational functionality. Despite the superior feature on voltage waveform quality and efficiency, the practical angle-controlled STATCOMs suffer from the over-current (and trips) and possible saturation of the interfacing transformers caused by negative sequence current during unbalanced conditions and faults in the utility. This paper specifically proposes a control structure to improve the angle-controlled STATCOMs performance under unbalanced conditions and faults. The main improvement is a substantial decrease in the negative sequence current and dc-link voltage oscillations under power system faults by the proposed control. This eliminates the need to redesign the STACOM power components to operate under fault current and dc-link voltage oscillations. The proposed control structure is designed based on adding appropriate oscillations to the conventional angle-controller output that is the control angle by which the VSC voltage vector leads/lags the line voltage vector. Since this control structure uses two angles for controlling the VSC output voltage, it is called dual angle control (DAC). PSCAD/EMTDC and experimental results verify the validity of the proposed control structure under unbalanced system conditions and faults. The experiments were conducted on a transient network analyzer, a unique hardware-based flexible ac transmission system simulator which was designed to study system faults and transients for a 2 × 100 MVA STATCOM field installation.}, number={6}, journal={IEEE TRANSACTIONS ON POWER ELECTRONICS}, author={Babaei, Saman and Parkhideh, Babak and Chandorkar, Mukul C. and Fardanesh, Bruce and Bhattacharya, Subhashish}, year={2014}, month={Jun}, pages={2723–2736} }
 @article{babaei_fardanesh_bhattacharya_2014, title={High-Power VSC-Based Simultaneous Positive- and Negative-Sequence Voltage Regulator}, volume={29}, ISSN={["1937-4208"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84907481310&partnerID=MN8TOARS}, DOI={10.1109/tpwrd.2014.2325773}, abstractNote={A voltage-source converter-based static synchronous compensator (STATCOM) is used in transmission and distribution systems for the purpose of voltage regulation and reactive power compensation. In the transmission level, angle-controlled STATCOMs are of primary interest due to their high efficiency and excellent waveform quality. There is a considerable number of angle-controlled STATCOMs installed in the different utilities in the U.S. Despite the high efficiency and good voltage quality, this type of STATCOM shows poor performance under ac system faults. They are usually tripped under severe unbalanced condition and system faults to protect the switches from huge negative-sequence current flow. This paper provides a solution to improve the transmission-level STATCOM performance under power system faults. The proposed solution is based on adding a single-phase inverter in series with the converter dc bus. One specific controller is designed which provides the capability of simultaneously controlling positive- and negative-sequence voltages. The results are supported by detailed simulation studies on the New York Power Authority STATCOM model using PSCAD/EMTDC.}, number={5}, journal={IEEE TRANSACTIONS ON POWER DELIVERY}, author={Babaei, Saman and Fardanesh, Bruce and Bhattacharya, Subhashish}, year={2014}, month={Oct}, pages={2124–2135} }
 @inproceedings{babaei_kashani_bhattacharya_2014, title={Instantaneous fault current limiter for PWM-controlled Voltage Source Converters}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84900430903&partnerID=MN8TOARS}, DOI={10.1109/apec.2014.6803622}, abstractNote={The PWM-controlled Voltage Source Converters (VSCs) are commonly used in industrial and utility applications. In spite of superior features of fast voltage regulation and stable DC-link voltage, PWM-controlled VSCs have the major drawback of being sensitive to the grid disturbances especially the unbalanced conditions and system faults. Unbalanced input voltage generates large negative sequence current flow into the converter which results in oscillations with twice the line frequency on the DC-link voltage. This negative sequence current flow might damage the semiconductor switches. Beside the negative sequence voltage, the input voltage distorted with other harmonics also causes converter performance deterioration by producing harmonics on the DC-link voltage. This paper presents an alternative solution to improve the PWM-controlled VSC performance under unbalanced conditions and system faults and also under distorted input voltage condition caused by other harmonics rather than the negative sequence voltage. This solution is based on direct calculation of the negative sequence (or other harmonics) reference voltage without using any current regulator. This elimination of the current regulator makes the proposed controller very fast and robust. The effectiveness of this solution has been validated by simulation and Hardware-In-the-Loop test.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Babaei, S. and Kashani, M.G. and Bhattacharya, Subhashish}, year={2014}, pages={2286–2292} }
 @inproceedings{babaei_parkhideh_bhattacharya_fardanesh_2013, title={A control method for angle-controlled STATCOMs under system faults}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84893199035&partnerID=MN8TOARS}, DOI={10.1109/pesmg.2013.6672943}, abstractNote={Voltage-Sourced Converter (VSC) based Synchronous Static Compensator (STATCOM) is used for voltage regulation in transmission and distribution systems. Comparing with PWM STATCOMs, angle-controlled STATCOMs are fired once with the line frequency to lower the system losses. In recent years, angle-controlled STATCOMs have been deployed by utility owners for the purpose of voltage regulation, voltage stability improvement and increasing operational functionality. Despite the superior feature on voltage waveform quality and efficiency, the practical angle-controlled STATCOMs suffer from the over-current (and trips) and possible saturation of the interfacing transformers caused by negative sequence current during unbalanced conditions and faults. This paper specifically proposes a control structure to improve the angle-controlled STATCOMs performance under unbalanced conditions and faults. The main improvement is to decrease the negative sequence current and DC-link voltage oscillations substantially under power line faults through the control and not the component design. PSCAD/EMTDC and Real Time Digital Simulation (RTDS) results verify the validity of the proposed control structure under fault conditions.}, booktitle={IEEE Power and Energy Society General Meeting}, author={Babaei, S. and Parkhideh, B. and Bhattacharya, Subhashish and Fardanesh, B.}, year={2013} }
 @inproceedings{babaei_bhattacharya_2013, title={A control structure for line-frequency-switched STATCOMs under system faults}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84891087871&partnerID=MN8TOARS}, DOI={10.1109/ecce.2013.6647037}, abstractNote={Voltage-Sourced Converter (VSC) based Static Synchronous Compensator (STATCOM) is used for voltage regulation in transmission and distribution systems. Comparing with PWM STATCOMs, Angle-controlled STATCOMs are fired at line frequency to lower the system losses. In recent years, angle-controlled STATCOMs have been deployed by utility owners for the purpose of voltage regulation, voltage stability improvement and increasing operational functionality. Despite the superior feature on voltage waveform quality and efficiency, the practical angle-controlled STATCOMs suffer from the over-current (and trips) and possible saturation of the interfacing transformers caused by negative sequence current during unbalanced conditions and system faults. This paper specifically proposes a control structure to improve the angle-controlled STATCOMs performance under unbalanced conditions and system faults. The main improvement is to decrease the negative sequence current and DC-link voltage oscillations substantially under power line faults through the control and not the components design. PSCAD/EMTDC and experimental results verify the validity of the proposed control structure under unbalanced conditions and system faults.}, booktitle={2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013}, author={Babaei, S. and Bhattacharya, Subhashish}, year={2013}, pages={2605–2612} }
 @inproceedings{babaei_bhattacharya_2013, title={DC-side series active power filter for STATCOM performance under system faults}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84891093461&partnerID=MN8TOARS}, DOI={10.1109/ecce.2013.6647405}, abstractNote={Voltage-Sourced Converter (VSC) based Static Synchronous Compensator (STATCOM) is used in transmission and distribution systems for the purpose of voltage regulation and reactive power compensation. In the transmission level, angle-controlled STATCOMs are of primary interest due to their high efficiency and excellent waveform quality. This type of the STATCOM is fired at line frequency to lower the switching losses. There are considerable numbers of angle-controlled STATCOMs installed in the different utilities in the United States. Despite the high efficiency and good voltage quality, this type of the STATCOM is showing poor performance under AC-system faults. They are usually tripped under severe unbalanced condition and system faults to protect the switches from huge negative sequence current flow. This paper provides a solution to improve the transmission level STATCOM performance under power system faults. Proposed solution is based on adding a single phase inverter in series with converter DC-bus. This single phase inverter generates controllable oscillations with twice the line frequency on the DC-link voltage which will be reflected as negative sequence voltage at VSC output terminals. Generated negative sequence voltage limits the fault negative sequence current flow on the STATCOM tie line. Based on the proposed Solution one specific controller is designed which provides the capability of simultaneous controlling of the both positive and negative sequence voltages. The results are supported by detailed simulation studies on the New York Power Authority (NYPA) STATCOM model using the PSCAD/EMTDC.}, booktitle={2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013}, author={Babaei, S. and Bhattacharya, Subhashish}, year={2013}, pages={5207–5214} }
 @inproceedings{babaei_bhattacharya_2013, title={Oscillatory angle control scheme for PWM static synchronous compensators under unbalanced conditions and system faults}, booktitle={2013 ieee energy conversion congress and exposition (ecce)}, author={Babaei, S. and Bhattacharya, S.}, year={2013}, pages={1976–1983} }
 @inproceedings{kashani_babaei_bhattacharya_2013, title={SVC and STATCOM application in Electric Arc Furnace efficiency improvement}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84899437744&partnerID=MN8TOARS}, DOI={10.1109/pedg.2013.6785641}, abstractNote={Electric Arc Furnaces (EAF) are high power industrial loads which cause power quality problems at all voltage levels due to their unbalanced and nonlinear characteristics. The rapid, stochastic large swings in real and reactive power required by the arc furnace causes voltage drops, rapid voltage variation and distortion across the ac supply network. These voltage drops and fluctuations not only have negative impact on the power system quality and other loads, but also have an effect on the arc furnace operation, power output and efficiency. Hence, some sort of reactive compensation is required to limit the voltage disturbances injected by arc furnace into the electric power system. In this paper, an accurate electric arc furnace model, whose parameters have been set according to a 80 MVA actual arc furnace, is studied. A Static VAR Compensator (SVC) is simulated in PSCad and Real Time Digital Simulation (RTDS)/RSCAD platform for the purpose of comparison of voltage regulation at EAF bus. It is shown that the SVC mitigates the reactive power fluctuations in addition to providing the fundamental reactive power, and regulates the Point of Common Coupling (PCC) bus voltage precisely during the arc furnace operation. To verify the PSCad simulation results and make a comparison, a real time simulation study based on Real Time Digital Simulation (RTDS)/RSCAD platform has been performed in this case. On the other hand, a 80 MVA static synchronous compensator (STATCOM) is simulated in PSCad. It is illustrated that the SVC is inherently limited in its ability to respond rapidly to the fluctuating arc furnace load. It is found that the transient performance of the EAF voltage in case which equipped with the STATCOM is better than the case equipped with SVC. It is also demonstrated that although the voltage regulation by the SVC compensates a portion of the reactive power fluctuation, it is completely unable to supply any portion of the fluctuating real power drawn by the arc furnace, while the STATCOM can supply those components of active and reactive power fluctuation. The STATCOM will not normally have a source of real power connected to its DC terminals. It is therefore unable to supply sustained real power or real power fluctuations. With suitable choice of DC capacitor, however, it is capable of supplying in large part the fluctuating real power requirement of the furnace.}, booktitle={2013 4th IEEE International Symposium on Power Electronics for Distributed Generation Systems, PEDG 2013 - Conference Proceedings}, author={Kashani, M.G. and Babaei, S. and Bhattacharya, Subhashish}, year={2013} }
 @inproceedings{yousefpoor_parkhideh_babaei_bhattacharya_2012, title={Control of cascaded multi-level STATCOM using line voltage total harmonic distortion minimization technique}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84870890532&partnerID=MN8TOARS}, DOI={10.1109/ecce.2012.6342596}, abstractNote={In this paper, a new switching strategy is proposed for a multi-level STATCOM system. An efficient approach in reducing the harmonic contents of the inverter's output voltage is total harmonic distortion (THD) minimization. In multilevel inverters with fundamental frequency switching strategy (each switch turning on and off once per output cycle), the switching angles can be selected such that the output THD is minimized. In three phase multilevel inverters, the optimization algorithm is commonly applied to the phase voltage of the inverter. This results in the minimum THD in phase voltage, but not necessarily in the line to line minimum THD. In this paper, THD minimization process is directly applied to the line to line voltage of the inverter, and a new control strategy of multilevel STATCOM is proposed. The proposed method will be implemented, in RTDS and the closed loop operation of multi-level STATCOM will be explored.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012}, author={Yousefpoor, N. and Parkhideh, B. and Babaei, S. and Bhattacharya, Subhashish}, year={2012}, pages={1782–1787} }
 @inproceedings{babaei_parkhideh_fardanesh_bhattacharya_2012, title={Convertible static compensator (CSC) performance under system fault}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84870604089&partnerID=MN8TOARS}, DOI={10.1109/pesgm.2012.6345705}, abstractNote={Convertible Static Compensator (CSC) which is a versatile FACTS technology has been installed on Marcy 345 kV substation and increases power transfer capability, operational functionality, and power flow controllability of the New York Power Authority (NYPA) transmission system. This paper presents a detailed description of CSC inverter operation and PSCAD simulation results of the CSC when it is operating as a STATCOM. The STATCOM steady state and dynamic operation simulation results under different conditions including unbalanced condition and faults is discussed. For fault condition analysis, attention is focused to Double L-G (LLG) fault at three different locations, one very close and two others electrically far from STATCOM terminals. This paper also demonstrates the effectiveness of the emergency PWM (EPWM) strategy a solution for limiting the poles current and preventing STATCOM over current tripping during fault conditions.}, booktitle={IEEE Power and Energy Society General Meeting}, author={Babaei, S. and Parkhideh, B. and Fardanesh, B. and Bhattacharya, Subhashish}, year={2012} }
 @inproceedings{parkhideh_yousefpoor_babaei_bhattacharya_2012, title={Design considerations in development of Active Mobile Substations}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84870944060&partnerID=MN8TOARS}, DOI={10.1109/ecce.2012.6342767}, abstractNote={While conventional mobile substations are used to bypass the whole substation in case of loss or maintenance of power transformers, Active Mobile Substations (AMS) can be used in normal conditions as a power router and contingencies as a recovery transformer. The AMS is a mobile substation with integrated power electronics and by controlling its throughput power can be connected across different transformers of the grid. The AMS is expected to be at least 20MVA with 230kV and 69kV outputs. This paper proposes transmission-level active mobile substations that provide back-up in case of power transformer failure or forced reduced operation scenarios in addition to power flow control for seasonal renewable energy transmission. These functions altogether have been aggregated not only because of the technical merits but also to address the economic concerns regarding the cost of the power electronics for transmission applications. In this paper, design considerations in development of the AMS will be provided in terms of power electronics building blocks, converter system control and its effects, and required supervisory control. Throughout the paper, theoretical analyses and relevant results are presented.}, booktitle={2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012}, author={Parkhideh, B. and Yousefpoor, N. and Babaei, S. and Bhattacharya, Subhashish}, year={2012}, pages={595–602} }
 @inproceedings{bhattacharya_babaei_2011, title={Series connected IGCT based three-level neutral point clamped voltage source inverter pole for high power converters}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-81855177074&partnerID=MN8TOARS}, DOI={10.1109/ecce.2011.6064349}, abstractNote={This paper reports design and experimental verification of series connected 4.5kV, 4kA IGCT based high power three-level Neutral Point Clamped (NPC) inverter pole. A simplified EMTDC model of a three level NPC inverter pole for different switching transitions based on experimental results is presented which is used for designing of RC snubber circuit for the IGCT switches. Dynamic voltage sharing issues and advantages of series connected 4.5kV, 4kA IGCT for high power 12 MVA three-level NPC inverter pole are investigated. Experimental results are presented for two three level NPC inverter poles operated as H-bridge with three series connected 4.5kV, 4kA IGCT per switch.}, booktitle={IEEE Energy Conversion Congress and Exposition: Energy Conversion Innovation for a Clean Energy Future, ECCE 2011, Proceedings}, author={Bhattacharya, Subhashish and Babaei, S.}, year={2011}, pages={4248–4255} }