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With the increasing penetration of Photovoltaic (PV) systems there is an increase in the variability of power generation. Grid operators tackle this problem by implementing advanced control functions such as frequency regulation. The focus of this paper is to develop a new control strategy that provides frequency regulation in a modular single-phase string configured two-stage grid-connected PV inverter. The control strategy is implemented for the PV systems without the use of energy storage. This frequency control is performed by regulating grid current based on droop curve control for PV
Shilpa Marti; Hariharan Krishnaswami. Frequency Regulation Strategy for Modular Two-Stage Grid-Connected Photovoltaic Systems. IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society 2018, 5303 -5307.
AMA StyleShilpa Marti, Hariharan Krishnaswami. Frequency Regulation Strategy for Modular Two-Stage Grid-Connected Photovoltaic Systems. IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society. 2018; ():5303-5307.
Chicago/Turabian StyleShilpa Marti; Hariharan Krishnaswami. 2018. "Frequency Regulation Strategy for Modular Two-Stage Grid-Connected Photovoltaic Systems." IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society , no. : 5303-5307.
Increasing penetration of photovoltaics (PV) into the electric grid necessitates accurate intra-hour solar irra-diance forecasting. The authors have previously developed a low cost all-sky imaging system at the University of Texas at San Antonio. The SkyImager hardware is designed around a Raspberry Pi single board computer (SBC) with a fully programmable, high resolution Pi Camera, housed in an all-weather enclosure. The software to process the images and to make minutes-ahead forecasts is written in Python 2.7 and utilizes the open source computer vision package OpenCV. A two-step approach for the forecasts uses optical flow to track low-level cumulus clouds and ray-tracing to predict the location of cloud shadows. This paper proposes to replace the ray-tracing approach which is traditionally known to be an ill-posed inverse problem with a machine learning strategy that utilizes a novel multi-layer perceptron (MLP) to classify cloud-cover in sub-images of the circumsolar region. The developed SkyImager was deployed at the National Renewable Energy Laboratory (NREL) in 2015, where it successfully collected months of all-sky image data. In 2016 a second SkyImager was integrated into a microgrid management system at Joint Base San Antonio. Results are presented to validate the proposed methodology.
Walter Richardson; Hariharan Krishnaswami; Les Shephard; Rolando Vega. Machine learning versus ray-tracing to forecast irradiance for an edge-computing SkyImager. 2017 19th International Conference on Intelligent System Application to Power Systems (ISAP) 2017, 1 -6.
AMA StyleWalter Richardson, Hariharan Krishnaswami, Les Shephard, Rolando Vega. Machine learning versus ray-tracing to forecast irradiance for an edge-computing SkyImager. 2017 19th International Conference on Intelligent System Application to Power Systems (ISAP). 2017; ():1-6.
Chicago/Turabian StyleWalter Richardson; Hariharan Krishnaswami; Les Shephard; Rolando Vega. 2017. "Machine learning versus ray-tracing to forecast irradiance for an edge-computing SkyImager." 2017 19th International Conference on Intelligent System Application to Power Systems (ISAP) , no. : 1-6.
To enable high penetration of PV systems into grid, it is imperative for the existing PV converters to perform load-following functions to be more dispatchable. Contrary to implementing energy storage systems or load shedding options for active power control, this paper focuses on implementing simple, inexpensive yet effective active power control strategy for two-stage multi-level dual-active bridge converter (ML-DAB), interfacing each PV string. Modified perturb and observe (P&O) MPPT algorithm is proposed to perform active power control. NI myRIO generates the desired phase shift in ML-DAB to extract either maximum power or reduced power.
Shilpa Marti; Hariharan Krishnaswami; Thomas Dalibor; Patrick Eraerds; Matthias Grave; Michael Algasinger; Sven Visbeck; Thomas Niesen; Jörg Palm. Novel MPPT Algorithm for Active Power Control of Multi-Level Dual-Active Bridge PV Converter Implemented in NI myRIO. 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC) 2017, 2936 -2940.
AMA StyleShilpa Marti, Hariharan Krishnaswami, Thomas Dalibor, Patrick Eraerds, Matthias Grave, Michael Algasinger, Sven Visbeck, Thomas Niesen, Jörg Palm. Novel MPPT Algorithm for Active Power Control of Multi-Level Dual-Active Bridge PV Converter Implemented in NI myRIO. 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC). 2017; ():2936-2940.
Chicago/Turabian StyleShilpa Marti; Hariharan Krishnaswami; Thomas Dalibor; Patrick Eraerds; Matthias Grave; Michael Algasinger; Sven Visbeck; Thomas Niesen; Jörg Palm. 2017. "Novel MPPT Algorithm for Active Power Control of Multi-Level Dual-Active Bridge PV Converter Implemented in NI myRIO." 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC) , no. : 2936-2940.
A modular multilevel power converter configuration for grid connected photovoltaic (PV) systems is proposed. The converter configuration replaces the conventional bulky line frequency transformer with several high frequency transformers, potentially reducing the balance of systems cost of PV systems. The front-end converter for each port is a neutral-point diode clamped (NPC) multi-level dc-dc dual-active bridge (ML-DAB) which allows maximum power point tracking (MPPT). The integrated high frequency transformer provides the galvanic isolation between the PV and grid side and also steps up the low dc voltage from PV source. Following the ML-DAB stage, in each port, is a NPC inverter. N number of NPC inverters’ outputs are cascaded to attain the per-phase line-to-neutral voltage to connect directly to the distribution grid (i.e., 13.8 kV). The cascaded NPC (CNPC) inverters have the inherent advantage of using lower rated devices, smaller filters and low total harmonic distortion required for PV grid interconnection. The proposed converter system is modular, scalable, and serviceable with zero downtime with lower foot print and lower overall cost. A novel voltage balance control at each module based on power mismatch among N-ports, have been presented and verified in simulation. Analysis and simulation results are presented for the N-port converter. The converter performance has also been verified on a hardware prototype.
Turgay Duman; Shilpa Marti; M. A. Moonem; Azas Ahmed Rifath Abdul Kader; Hariharan Krishnaswami. A Modular Multilevel Converter with Power Mismatch Control for Grid-Connected Photovoltaic Systems. Energies 2017, 10, 698 .
AMA StyleTurgay Duman, Shilpa Marti, M. A. Moonem, Azas Ahmed Rifath Abdul Kader, Hariharan Krishnaswami. A Modular Multilevel Converter with Power Mismatch Control for Grid-Connected Photovoltaic Systems. Energies. 2017; 10 (5):698.
Chicago/Turabian StyleTurgay Duman; Shilpa Marti; M. A. Moonem; Azas Ahmed Rifath Abdul Kader; Hariharan Krishnaswami. 2017. "A Modular Multilevel Converter with Power Mismatch Control for Grid-Connected Photovoltaic Systems." Energies 10, no. 5: 698.
Neutral point clamped (NPC) multilevel inverter is being used for medium and high power applications since it can synthesize more voltage levels with smaller output voltage steps compared to two level full-bridge inverters. An NPC based multi-level dual-active bridge (ML-DAB) dc-dc converter has been proposed where the low voltage side consists a full-bridge producing a two-level voltage and the high voltage side has two three-level neutral point diode clamped (NPC) switching poles which produce a five-level voltage waveform across the high frequency transformer. Capacitor voltage unbalance has been an important concern for NPC topology. A neutral-point current control scheme has been proposed to control the imbalance between the capacitor voltages in the NPC side. Experimental results for steady-state operation and the capacitor voltage balancing control have been shown in simulation.
M A Moonem; Turgay Duman; Hariharan Krishnaswami. Capacitor voltage balancing in a neutral-point clamped multilevel dc-dc dual active bridge converter. 2017 IEEE 8th International Symposium on Power Electronics for Distributed Generation Systems (PEDG) 2017, 1 -7.
AMA StyleM A Moonem, Turgay Duman, Hariharan Krishnaswami. Capacitor voltage balancing in a neutral-point clamped multilevel dc-dc dual active bridge converter. 2017 IEEE 8th International Symposium on Power Electronics for Distributed Generation Systems (PEDG). 2017; ():1-7.
Chicago/Turabian StyleM A Moonem; Turgay Duman; Hariharan Krishnaswami. 2017. "Capacitor voltage balancing in a neutral-point clamped multilevel dc-dc dual active bridge converter." 2017 IEEE 8th International Symposium on Power Electronics for Distributed Generation Systems (PEDG) , no. : 1-7.
With increasing use of photovoltaic (PV) power generation by utilities and their residential customers, the need for accurate intra-hour and day-ahead solar irradiance forecasting has become critical. This paper details the development of a low cost all-sky imaging system and an intra-hour cloud motion prediction methodology that produces minutes-ahead irradiance forecasts. The SkyImager is designed around a Raspberry Pi single board computer (SBC) with a fully programmable, high resolution Pi Camera, housed in a durable all-weather enclosure. Our software is written in Python 2.7 and utilizes the open source computer vision package OpenCV. The SkyImager can be configured for different operational environments and network designs, from a standalone edge computing model to a fully integrated node in a distributed, cloud-computing based micro-grid. Preliminary results are presented using the imager on site at the National Renewable Energy Laboratory (NREL) in Golden, CO, USA during the fall of 2015 under a variety of cloud conditions.
Walter Richardson; Hariharan Krishnaswami; Rolando Vega; Michael Cervantes. A Low Cost, Edge Computing, All-Sky Imager for Cloud Tracking and Intra-Hour Irradiance Forecasting. Sustainability 2017, 9, 482 .
AMA StyleWalter Richardson, Hariharan Krishnaswami, Rolando Vega, Michael Cervantes. A Low Cost, Edge Computing, All-Sky Imager for Cloud Tracking and Intra-Hour Irradiance Forecasting. Sustainability. 2017; 9 (4):482.
Chicago/Turabian StyleWalter Richardson; Hariharan Krishnaswami; Rolando Vega; Michael Cervantes. 2017. "A Low Cost, Edge Computing, All-Sky Imager for Cloud Tracking and Intra-Hour Irradiance Forecasting." Sustainability 9, no. 4: 482.
With the increasing demand for PV technology, low cost, highly efficient, modular PV inverter system has become a pertinent issue. As a solution, modular two-stage power conversion with isolation and string-level power conversion has become an attractive choice recently. However, the complexity of the control algorithm in addressing power imbalance between modular power conversion units becomes a disadvantage to these type of configurations. This paper proposes a new control scheme for the two stage, N-port, string-connected modular multilevel cascaded inverters. Control algorithm ensures the maximum extraction of solar power along with the per port power balancing of the PV systems. Simulation of N-port multilevel dual active bridge stage along with the cascaded H-bridge stage for one phase is presented to verify the feasibility of the proposed algorithm.
S. Marti; Hariharan Krishnaswami. Control algorithm for port power imbalance in two-stage, N-port modular multilevel cascaded photovoltaic inverters. 2017 IEEE Texas Power and Energy Conference (TPEC) 2017, 1 -6.
AMA StyleS. Marti, Hariharan Krishnaswami. Control algorithm for port power imbalance in two-stage, N-port modular multilevel cascaded photovoltaic inverters. 2017 IEEE Texas Power and Energy Conference (TPEC). 2017; ():1-6.
Chicago/Turabian StyleS. Marti; Hariharan Krishnaswami. 2017. "Control algorithm for port power imbalance in two-stage, N-port modular multilevel cascaded photovoltaic inverters." 2017 IEEE Texas Power and Energy Conference (TPEC) , no. : 1-6.
A multi-port converter configuration which achieves a high-power DC-AC conversion for a large-scale grid-connected photovoltaic system is utilized. A novel multi-port nonlinear control is proposed to realize a voltage and current control strategy among cascaded ports. Each port consists of solar panels, a multilevel dual-active bridge DC-DC converter utilizing a secondary step-up high-frequency transformer, and a high-voltage DC-AC sinusoidal pulse-width modulated inverter. This control is modelled and verified in Matlab/Simulink; detailed analysis and simulation results are provided.
Thilo Janssen; Hariharan Krishnaswami. Voltage and current control of a multi-port NPC inverter configuration for a grid-connected photovoltaic system. 2016 IEEE 17th Workshop on Control and Modeling for Power Electronics (COMPEL) 2016, 1 -7.
AMA StyleThilo Janssen, Hariharan Krishnaswami. Voltage and current control of a multi-port NPC inverter configuration for a grid-connected photovoltaic system. 2016 IEEE 17th Workshop on Control and Modeling for Power Electronics (COMPEL). 2016; ():1-7.
Chicago/Turabian StyleThilo Janssen; Hariharan Krishnaswami. 2016. "Voltage and current control of a multi-port NPC inverter configuration for a grid-connected photovoltaic system." 2016 IEEE 17th Workshop on Control and Modeling for Power Electronics (COMPEL) , no. : 1-7.
A modular, multi-port converter configuration realizes DC-AC conversion for a high-power grid-connected photovoltaic system; but one or more faults can occur in any of the highly numerous components. In this paper, a reconfigurable multi-port control is proposed to achieve fault detection and resolution among cascaded ports. A series of switching algorithms are applied, thus enabling a continued operation under faulty conditions. A detailed analysis and simulation results are presented for the control to detect the fault, localize it, and reconfigure the system for robust operation. The projected strategy is demonstrated using MATLAB/SIMULINK.
Thilo Janssen; Hariharan Krishnaswami. Fault-tolerant control for a modular cascaded NPC inverter configuration. 2016 IEEE 17th Workshop on Control and Modeling for Power Electronics (COMPEL) 2016, 1 -7.
AMA StyleThilo Janssen, Hariharan Krishnaswami. Fault-tolerant control for a modular cascaded NPC inverter configuration. 2016 IEEE 17th Workshop on Control and Modeling for Power Electronics (COMPEL). 2016; ():1-7.
Chicago/Turabian StyleThilo Janssen; Hariharan Krishnaswami. 2016. "Fault-tolerant control for a modular cascaded NPC inverter configuration." 2016 IEEE 17th Workshop on Control and Modeling for Power Electronics (COMPEL) , no. : 1-7.
This paper presents an intra-hour cloud forecasting methodology for distributed solar generation by predicting irradiance changes in five minute intervals throughout the day. This approach is designed to assist in the creation of a low-cost, sky imaging system for experimental field-testing. The image processing techniques are presented in the following sections: Forecasting Inputs Required, Masking, Segmentation, Filtering & Binary Conversion, True North Orientation, Optical Flow & Cloud Motion, and Ray Tracing & Irradiance Predictions. Sky/Cloud images were acquired on site at the National Renewable Energy Laboratory (NREL) and were processed by the above procedure for five individual days under a variety of cloud conditions. Lastly, the irradiance change predictions were validated using NREL's direct solar irradiance measurements* for comparison.
M. Cervantes; Hariharan Krishnaswami; W. Richardson; R. Vega. Utilization of Low Cost, Sky-Imaging Technology for Irradiance Forecasting of Distributed Solar Generation. 2016 IEEE Green Technologies Conference (GreenTech) 2016, 142 -146.
AMA StyleM. Cervantes, Hariharan Krishnaswami, W. Richardson, R. Vega. Utilization of Low Cost, Sky-Imaging Technology for Irradiance Forecasting of Distributed Solar Generation. 2016 IEEE Green Technologies Conference (GreenTech). 2016; ():142-146.
Chicago/Turabian StyleM. Cervantes; Hariharan Krishnaswami; W. Richardson; R. Vega. 2016. "Utilization of Low Cost, Sky-Imaging Technology for Irradiance Forecasting of Distributed Solar Generation." 2016 IEEE Green Technologies Conference (GreenTech) , no. : 142-146.
With the increase in demand for clean and green power, several energy utilities are increasing renewable energy in their generation portfolio. The high penetration of PV can create problems of voltage fluctuation and frequency variation. The two major smart functionalities that address high PV penetration include dynamic Volt/VAR control for voltage fluctuations and active power control and curtailment to achieve frequency regulation. Quasi-static time series simulation of the power grid that includes the two smart functionalities of the Photovoltaic (PV) generator is needed. In this paper, the modeling and analysis of the power grid with PV generators is presented using the open source simulation tool OpenDSS. Specifically, the COM interface capability of OpenDSS is used to interface with Matlab to simulate the advanced functionalities of Volt/VAR and active power control and at the same time observe the effect of these controls in the power grid. The IEEE 13 bus feeder is used to demonstrate the usefulness of the proposed simulation methodology interfacing both Matlab and OpenDSS.
Meghasai; S. Monger; R. Vega; Hariharan Krishnaswami. Simulation of smart functionalities of photovoltaic inverters by interfacing OpenDSS and Matlab. 2015 IEEE 16th Workshop on Control and Modeling for Power Electronics (COMPEL) 2015, 1 -6.
AMA StyleMeghasai, S. Monger, R. Vega, Hariharan Krishnaswami. Simulation of smart functionalities of photovoltaic inverters by interfacing OpenDSS and Matlab. 2015 IEEE 16th Workshop on Control and Modeling for Power Electronics (COMPEL). 2015; ():1-6.
Chicago/Turabian StyleMeghasai; S. Monger; R. Vega; Hariharan Krishnaswami. 2015. "Simulation of smart functionalities of photovoltaic inverters by interfacing OpenDSS and Matlab." 2015 IEEE 16th Workshop on Control and Modeling for Power Electronics (COMPEL) , no. : 1-6.
Dual active bridge (DAB) converters have been popular in high voltage, low and medium power DC-DC applications, as well as an intermediate high frequency link in solid state transformers. In this paper, a multilevel DAB (ML-DAB) has been proposed in which two active bridges produce two-level (2L)-5L, 5L-2L and 3L-5L voltage waveforms across the high frequency transformer. The proposed ML-DAB has the advantage of being used in high step-up/down converters, which deal with higher voltages, as compared to conventional two-level DABs. A three-level neutral point diode clamped (NPC) topology has been used in the high voltage bridge, which enables the semiconductor switches to be operated within a higher voltage range without the need for cascaded bridges or multiple two-level DAB converters. A symmetric modulation scheme, based on the least number of angular parameters rather than the duty-ratio, has been proposed for a different combination of bridge voltages. This ML-DAB is also suitable for maximum power point tracking (MPPT) control in photovoltaic applications. Steady-state analysis of the converter with symmetric phase-shift modulation is presented and verified using simulation and hardware experiments.
M. A. Moonem; C. L. Pechacek; R. Hernandez; Hariharan Krishnaswami. Analysis of a Multilevel Dual Active Bridge (ML-DAB) DC-DC Converter Using Symmetric Modulation. Electronics 2015, 4, 239 -260.
AMA StyleM. A. Moonem, C. L. Pechacek, R. Hernandez, Hariharan Krishnaswami. Analysis of a Multilevel Dual Active Bridge (ML-DAB) DC-DC Converter Using Symmetric Modulation. Electronics. 2015; 4 (2):239-260.
Chicago/Turabian StyleM. A. Moonem; C. L. Pechacek; R. Hernandez; Hariharan Krishnaswami. 2015. "Analysis of a Multilevel Dual Active Bridge (ML-DAB) DC-DC Converter Using Symmetric Modulation." Electronics 4, no. 2: 239-260.
A novel converter configuration that allows for high frequency transformer integration and high voltage distribution is proposed for large scale grid-connected photovoltaic (PV) system. The proposed configuration has in the front-end of the solar panel, dual-active bridge dc-dc converter with three-level neutral-point clamped secondary and a high-step-up ratio high frequency transformer. The output of the dual-active bridge converter may be connected to a high voltage inverter to achieve high ac voltage to allow for direct interconnection with the utility ac grid at distribution voltage level. The proposed configuration has advantages of high frequency transformer, high efficiency and high voltage operation. Phase-shift modulation technique along with Maximum Power Point Tracking is proposed for the three-level dual-active bridge converter and the overall converter performance is verified in simulation.
M. A. Moonem; Hariharan Krishnaswami. Control and configuration of three-level dual-active bridge DC-DC converter as a front-end interface for photovoltaic system. 2014 IEEE Applied Power Electronics Conference and Exposition - APEC 2014 2014, 3017 -3020.
AMA StyleM. A. Moonem, Hariharan Krishnaswami. Control and configuration of three-level dual-active bridge DC-DC converter as a front-end interface for photovoltaic system. 2014 IEEE Applied Power Electronics Conference and Exposition - APEC 2014. 2014; ():3017-3020.
Chicago/Turabian StyleM. A. Moonem; Hariharan Krishnaswami. 2014. "Control and configuration of three-level dual-active bridge DC-DC converter as a front-end interface for photovoltaic system." 2014 IEEE Applied Power Electronics Conference and Exposition - APEC 2014 , no. : 3017-3020.
This paper covers the development of an adaptive, interactive rule generation interface applied to the full scope of solar forecasting techniques, both current and forthcoming. The interface provides a user-friendly platform for detecting patterns and correlations between elements in a database of solar irradiance, weather and photovoltaic generation information. The database consists of 10 years of data obtained from the National Renewable Energy Laboratory (NREL) data acquisition systems and the Automated Surface Observing System (ASOS). This report discusses how such an interface can be used to improve existing forecasting algorithms and also be used to create new forecasting techniques.
J. Nummikoski; Y. S. Manjili; R. Vega; Hariharan Krishnaswami. Adaptive rule generation for solar forecasting: Interfacing with a knowledge-base library. 2013 IEEE 39th Photovoltaic Specialists Conference (PVSC) 2013, 0980 -0984.
AMA StyleJ. Nummikoski, Y. S. Manjili, R. Vega, Hariharan Krishnaswami. Adaptive rule generation for solar forecasting: Interfacing with a knowledge-base library. 2013 IEEE 39th Photovoltaic Specialists Conference (PVSC). 2013; ():0980-0984.
Chicago/Turabian StyleJ. Nummikoski; Y. S. Manjili; R. Vega; Hariharan Krishnaswami. 2013. "Adaptive rule generation for solar forecasting: Interfacing with a knowledge-base library." 2013 IEEE 39th Photovoltaic Specialists Conference (PVSC) , no. : 0980-0984.
Dual Active Bridge (DAB) dc-dc converter finds applications in the intermediate high frequency link power conversion stage of a high-power solid state transformer. In this paper, a multilevel DAB dc-dc converter is proposed. A three-level neutral point clamped (NPC) inverter topology has been used in the high voltage bridge which enables semiconductor switches to be operated in higher voltage range without using cascaded bridges and multiple DAB converters. Modulation strategy to control power flow between the active bridges with one of the bridges switching at multi-level is proposed in this paper. Steady-state analysis of the converter with the proposed modulation scheme is presented along with simulation results to augment the analysis.
M.A. Moonem; Hariharan Krishnaswami. Analysis and control of multi-level dual active bridge DC-DC converter. 2012 IEEE Energy Conversion Congress and Exposition (ECCE) 2012, 1556 -1561.
AMA StyleM.A. Moonem, Hariharan Krishnaswami. Analysis and control of multi-level dual active bridge DC-DC converter. 2012 IEEE Energy Conversion Congress and Exposition (ECCE). 2012; ():1556-1561.
Chicago/Turabian StyleM.A. Moonem; Hariharan Krishnaswami. 2012. "Analysis and control of multi-level dual active bridge DC-DC converter." 2012 IEEE Energy Conversion Congress and Exposition (ECCE) , no. : 1556-1561.
In this paper, an isolated bi-directional ac/dc converter with a single power conversion stage is proposed for both charging and Vehicle-to-Grid (V2G) applications of PHEV. The converter consists of two active bridges connected through a series resonant tank and a high-frequency transformer. Steady-state analysis is presented for the proposed phase-shift modulation technique between active bridges, to control the bi-directional power flow in the converter. Simulation results are presented to augment the analysis. The proposed converter has the advantages of minimal power conversion stages, high switching frequency operation and low switching losses.
Shesh Narayan Vaishnav; Hariharan Krishnaswami. Single-stage isolated bi-directional converter topology using high frequency AC link for charging and V2G applications of PHEV. 2011 IEEE Vehicle Power and Propulsion Conference 2011, 1 -4.
AMA StyleShesh Narayan Vaishnav, Hariharan Krishnaswami. Single-stage isolated bi-directional converter topology using high frequency AC link for charging and V2G applications of PHEV. 2011 IEEE Vehicle Power and Propulsion Conference. 2011; ():1-4.
Chicago/Turabian StyleShesh Narayan Vaishnav; Hariharan Krishnaswami. 2011. "Single-stage isolated bi-directional converter topology using high frequency AC link for charging and V2G applications of PHEV." 2011 IEEE Vehicle Power and Propulsion Conference , no. : 1-4.
In this paper, PhotoVoltaic (PV) microinverter using a single-stage high-frequency ac link series resonant topology is proposed. The inverter has two active bridges, one at the front-end of PV module and the other at the output or utility side. The active bridges are interfaced through a series resonant tank and a high frequency transformer. A novel phase-shift modulation technique to regulate the current into utility is proposed. Steady-state analysis using sinusoidal approximation is presented to determine the magnitude of output current into utility. Soft-switching operation is ensured in all switches in the converter due to resonant nature of the circuit. The inverter has advantages of minimal power conversion stages, high-switching frequency operation and low switching losses and hence ideally suited for low power module integrated applications.
Hariharan Krishnaswami. Photovoltaic microinverter using single-stage isolated high-frequency link series resonant topology. 2011 IEEE Energy Conversion Congress and Exposition 2011, 495 -500.
AMA StyleHariharan Krishnaswami. Photovoltaic microinverter using single-stage isolated high-frequency link series resonant topology. 2011 IEEE Energy Conversion Congress and Exposition. 2011; ():495-500.
Chicago/Turabian StyleHariharan Krishnaswami. 2011. "Photovoltaic microinverter using single-stage isolated high-frequency link series resonant topology." 2011 IEEE Energy Conversion Congress and Exposition , no. : 495-500.
In this paper, a three-port converter with three active full bridges, two series-resonant tanks, and a three-winding transformer is proposed. It uses a single power conversion stage with high-frequency link to control power flow between batteries, load, and a renewable source such as fuel cell. The converter has capabilities of bidirectional power flow in the battery and the load port. Use of series-resonance aids in high switching frequency operation with realizable component values when compared to existing three-port converter with only inductors. The converter has high efficiency due to soft-switching operation in all three bridges. Steady-state analysis of the converter is presented to determine the power flow equations, tank currents, and soft-switching region. Dynamic analysis is performed to design a closed-loop controller that will regulate the load-side port voltage and source-side port current. Design procedure for the three-port converter is explained and experimental results of a laboratory prototype are presented.
Hariharan Krishnaswami; Ned Mohan. Three-Port Series-Resonant DC–DC Converter to Interface Renewable Energy Sources With Bidirectional Load and Energy Storage Ports. IEEE Transactions on Power Electronics 2009, 24, 2289 -2297.
AMA StyleHariharan Krishnaswami, Ned Mohan. Three-Port Series-Resonant DC–DC Converter to Interface Renewable Energy Sources With Bidirectional Load and Energy Storage Ports. IEEE Transactions on Power Electronics. 2009; 24 (10):2289-2297.
Chicago/Turabian StyleHariharan Krishnaswami; Ned Mohan. 2009. "Three-Port Series-Resonant DC–DC Converter to Interface Renewable Energy Sources With Bidirectional Load and Energy Storage Ports." IEEE Transactions on Power Electronics 24, no. 10: 2289-2297.
Multi-port converters have attracted special interest in applications such as self sustaining residential homes and buildings with multiple energy sources and energy storage. In this paper a constant switching frequency series resonant three-port bi-directional DC-DC converter is proposed. The converter uses a three-winding transformer with two of its windings connected to H-bridges through series resonant circuits. To control the output voltage and to share the power between the two sources, two control variables are proposed. One of them is the phase shift between the fundamental of the outputs of the H-bridges and the other between two legs in one of the bridges. Sinusoidal analysis is presented and equations for output voltage and input port power are derived as a function of the phase shifts. It is observed from the analysis that the power can be made bi-directional in either of the source ports by varying the phase shifts. Switching frequency is chosen such that the converter operates above resonant frequency and hence aid in zero voltage switching (ZVS). A design procedure to select converter parameters is explained. Simulation and experimental results of a prototype converter are presented.
Hariharan Krishnaswami; N. Mohan. Constant switching frequency series resonant three-port bi-directional DC-DC converter. 2008 IEEE Power Electronics Specialists Conference 2008, 1640 -1645.
AMA StyleHariharan Krishnaswami, N. Mohan. Constant switching frequency series resonant three-port bi-directional DC-DC converter. 2008 IEEE Power Electronics Specialists Conference. 2008; ():1640-1645.
Chicago/Turabian StyleHariharan Krishnaswami; N. Mohan. 2008. "Constant switching frequency series resonant three-port bi-directional DC-DC converter." 2008 IEEE Power Electronics Specialists Conference , no. : 1640-1645.
Multi-port DC-DC converters have attracted special interest in applications where multiple energy sources are used. In this paper, a current-fed bi-directional three-port converter is proposed. Steady state and dynamic analysis of the converter is presented along with simulation results. The converter has the advantages of reduced current ripple at the input due to the presence of input inductor, high voltage step up ratios and no bulk input capacitors. One of the applications of such a converter is in fuel-cell hybrid systems with energy storage for use in telecommunication sub-stations.
Hariharan Krishnaswami; N. Mohan. A current-fed three-port bi-directional DC-DC converter. INTELEC 07 - 29th International Telecommunications Energy Conference 2007, 523 -526.
AMA StyleHariharan Krishnaswami, N. Mohan. A current-fed three-port bi-directional DC-DC converter. INTELEC 07 - 29th International Telecommunications Energy Conference. 2007; ():523-526.
Chicago/Turabian StyleHariharan Krishnaswami; N. Mohan. 2007. "A current-fed three-port bi-directional DC-DC converter." INTELEC 07 - 29th International Telecommunications Energy Conference , no. : 523-526.