@inproceedings{cho_mobarrez_bhattacharya_2017, title={A multi-loop controller for LCL-filtered grid-connected converters integrated with a hybrid harmonic compensation and a novel virtual impedance}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85020026025&partnerID=MN8TOARS}, DOI={10.1109/apec.2017.7931074}, abstractNote={The LCL-filtered converter is widely adapted to interface renewable energy sources and energy storage devices to the grid. While the LCL filter is capable of eliminating current harmonics caused by the high-frequency PWM of the converter, low-order current harmonics are reduced selectively by the stationary-frame resonant harmonic compensators (HCs). There are two types of the harmonic compensator, namely, harmonic current compensator (HCC) and harmonic voltage compensator (HVC). HCCs are in general embedded in parallel with conventional grid current controllers by which the active and reactive power are regulated. If autonomous islanding operation is required, the active and reactive power are controlled by a V-f droop method and a filter capacitor voltage controller with which HCCs or HVCs are added in parallel. In this paper, a multi-loop controller is proposed as one possible alternative to the conventional grid current controller to improve the harmonic compensation performance by using both HCCs and HVCs, which is a hybrid harmonic compensation (HHC). In addition, a novel virtual impedance implementation technique which fits to the multi-loop frame is presented to maintain stability of the controller in case of large grid impedance.}, booktitle={Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC}, author={Cho, Y. and Mobarrez, M. and Bhattacharya, Subhashish}, year={2017}, pages={2658–2663} }
 @inproceedings{kashani_cho_bhattacharya_2016, title={Design consideration of volt-VAR controllers in distribution systems with multiple PV inverters}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85015376247&partnerID=MN8TOARS}, DOI={10.1109/ecce.2016.7855012}, abstractNote={Advanced control techniques such as Volt-VAR Control (VVC) are required for integration of multiple distributed renewable energy, such as Photovoltaic (PV) resources, on an electric distribution system. However, undesired interactions have been observed among these Volt-VAR controlled PV inverters which leads to oscillation and instability of the system. In this paper, an analytical approach to study the stability of local voltage control in high PV penetrated distribution systems with advanced Volt-VAR control functions is employed. The transient of inverter Volt-VAR Control interactions and dynamics of the interconnected feed-back loops in the distribution circuits are investigated. It is shown analytically that the Grid impedances, droop slope, PI controller parameters, response time and delay time in the VVC are the main factors affecting the dynamic response of the system, and the absence of a standard selection criteria for inverter and controller parameters under different Grid impedances results in undesired potential interactions among the PV inverters and distribution power system.}, booktitle={ECCE 2016 - IEEE Energy Conversion Congress and Exposition, Proceedings}, author={Kashani, M.G. and Cho, Y. and Bhattacharya, Subhashish}, year={2016} }
 @inproceedings{cho_han_beddingfield_ha_bhattacharya_2016, title={Seamless black start and reconnection of LCL-filtered solid state transformer based on droop control}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85015434753&partnerID=MN8TOARS}, DOI={10.1109/ecce.2016.7855416}, abstractNote={The solid state transformer (SST) is an emerging technology that can replace conventional passive transformers and actively manage renewable energy resources, energy storage devices, and loads. In this paper, a seamless black start control strategy is proposed for an SST-based smart grid system that has fault ride-through capability when it is islanded from the grid. Also, a method is developed to achieve smooth reconnection to the grid after a fault is cleared. The main component of the proposed control strategy is control of the high-voltage side converter of the SST (HV SST), which is based on a combination of droop control and an LCL filter. A single-loop controller for the capacitor voltage of the LCL filter is proposed, and simple criteria for setting compensator gains are provided. A low-voltage scaled SST system is introduced, and the controllers of the converters within the system are described. The proposed control strategy has been tested in simulation and experimentally on a low-voltage scaled testbed.}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Cho, Y. and Han, Y. and Beddingfield, R. B. and Ha, J. I. and Bhattacharya, S.}, year={2016} }
 @inproceedings{cho_han_madhusoodhanan_ha_bhattacharya_2016, title={Synchronous frame full-order observer design for three-phase buck-type PWM rectifier}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85010078135&partnerID=MN8TOARS}, DOI={10.1109/iecon.2016.7794059}, abstractNote={This paper presents a synchronous reference frame full-order observer for a three-phase buck-type PWM rectifier that estimates both the currents of the input filter inductors and the voltages of the input filter capacitors. Either the currents or the voltages are needed in most cases to control the input grid power factor and the output dc voltage or current. For example, multiloop control strategies, which have been widely used for power rectifiers that are equipped with higher order LC or LCL input filters, require input filter currents or voltages. Using the proposed observer, the number of actual sensors needed for a buck-type rectifier control system can be reduced while maintaining fast dynamic performance and steady-state accuracy. The feasibility of the proposed technique is verified through MATLAB/PLECS simulations and experiments.}, booktitle={IECON Proceedings (Industrial Electronics Conference)}, author={Cho, Y. and Han, Y. and Madhusoodhanan, S. and Ha, J.-I. and Bhattacharya, Subhashish}, year={2016}, pages={3618–3622} }
 @inproceedings{madhusoodhanan_cho_kadavelugu_bhattacharya_grider_ryu_agarwal_leslie_2013, title={Comparative evaluation of SiC devices for PWM buck rectifier based active front end converter for MV grid interface}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84891099153&partnerID=MN8TOARS}, DOI={10.1109/ecce.2013.6647097}, abstractNote={In this paper a new method for implementation of a 3-phase medium voltage rectifier is presented for Active Front End grid interface applications. A current source based PWM buck rectifier with Silicon Carbide (SiC) devices, different from the traditional GTO based current source rectifier, is used to grid tie with 3-phase, 4.16 kV grid. The power level considered is 100 kVA. Simplicity of construction, very high efficiency, better input line current control and small volume are the main advantages of this system. Due to low switching losses compared with traditional GTOs, PWM operation of the rectifier at higher switching frequencies is possible. A detailed simulation shows the validity of the proposed method. Efficiency comparison of the PWM Buck rectifier with 10 kV/10 A SiC MOSFET and 15 kV/20 A SiC IGBT as the active devices is also presented. Low voltage hardware prototype based high frequency switching validation is also carried out.}, booktitle={2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013}, author={Madhusoodhanan, S. and Cho, Y. and Kadavelugu, A. and Bhattacharya, Subhashish and Grider, D. and Ryu, S.-H. and Agarwal, A. and Leslie, S.}, year={2013}, pages={3034–3041} }