William E. Stanchina

Maximum Power Point Tracking Using Model Reference Adaptive Control

This paper proposes an adaptive control architecture for maximum power point tracking (MPPT) in photovoltaic systems. MPPT technologies have been used in photovoltaic systems to deliver the maximum available power to the load under changes of the solar insolation and ambient temperature. To improve the performance of MPPT, this paper develops a two-level adaptive control architecture that can reduce complexity in system control and effectively handle the uncertainties and perturbations in the photovoltaic systems and the environment. The first level of control is ripple correlation control (RCC), and the second level is model reference adaptive control (MRAC). By decoupling these two control algorithms, the system achieves MPPT with overall system stability. This paper focuses mostly on the design of the MRAC algorithm, which compensates the underdamped characteristics of the power conversion system. The original transfer function of the power conversion system has time-varying parameters, and its step response contains oscillatory transients that vanish slowly. Using the Lyapunov approach, an adaption law of the controller is derived for the MRAC system to eliminate the underdamped modes in power conversion. It is shown that the proposed control algorithm enables the system to converge to the maximum power point in milliseconds.

Effects of semiconducting and metallic single-walled carbon nanotubes on performance of bulk heterojunction organic solar cells

This letter reports that the performance of organic solar cells made from blended films of regioregular poly 3-hexylthiophene and methanofullerene can be boosted by introducing single-walled carbon nanotubes (SWCNTs) into the active layer at low concentration. However, the performance degrades at higher SWCNTs concentration. The intensity dependent photocurrent measurement shows that the decreased performance at higher concentration of SWCNTs is attributed to bimolecular recombination in the presence of metallic SWCNTs. Meanwhile, it has been found that the increased performance at low concentration of SWCNTs is due to the increased carrier mobility as semiconducting SWCNTs provide lower resistance pathways.

An analytical model for evaluating the influence of device parasitics on Cdv/dt induced false turn-on in SiC MOSFETs

Reported here is an analytical methodology for modeling the Cdv/dt induced false turn-on in SiC MOSFETs. A Cdv/dt test circuit is utilized to assess the influence of the parasitic device parameters on the magnitude of the induced gate-source voltage during false turn-on. The effect that each parasitic parameter has on the damping of the SiC MOSFETs drain-source voltage is also evaluated. Experimental results are provided to validate the analytical model. The methods presented here will enable design engineers to project the performance of next generation SiC MOSFETs in high dv/dt circuits like the synchronous buck converter.

Smart grid education models for modern electric power system engineering curriculum

The emerging clean-energy smart grid environment in the electric power sector has necessitated that related educational programs evolve to meet the needs of students, faculty, and employers alike. In order to prepare the next generation of power engineering professionals to meet the challenges ahead in the electric power sector, a new curriculum must be developed that includes core power engineering principals coupled with emerging aspects of smart grid technologies and clean energy integration. Such curriculum also needs to consider not only the end-use side of the power system within the smart grid definition, such as smart metering, communications and demand response aspects, but also other key enabling technologies throughout the whole transmission and distribution system and the entire energy supply chain. These include areas such as energy storage technologies, advanced power electronics at the transmission and distribution levels, networked control systems, automation, renewable and alternative energy systems integration, system optimization, real-time control, and other related topics. In addition, the evolution of power programs and curriculum in this emerging area must take into account significant input from industry constituents engaged in the manufacturing, implementation, operation, and maintenance of the new smart grid technologies and systems. By working collaboratively with industry to meet future employer needs, programs with newly developed course offerings will be able to better prepare students and existing professionals alike for the rapidly growing clean-energy, smart grid environment. This paper will provide an overview of a potential model for program structures and course developments in this critical area, including examples of initiatives already being developed and deployed.

Effects of parasitic capacitances on gallium nitride heterostructure power transistors

The parasitic capacitances of GaN have been evaluated in order to assess the impact that each capacitance has on the switching losses of GaN devices. This required developing and validating equivalent GaN HFET device models in SaberRD and implementing the models in a switching test circuit under variable parasitic capacitance conditions. The data presented here can facilitate optimizing the area and hence capacitance of GaN devices for future generation power electronics.

The Power and Energy Initiative at the University of Pittsburgh: Addressing the aging workforce issue through innovative education, collaborative research, and industry partnerships

The Power & Energy Initiative in the Swanson School of Engineering at the University of Pittsburgh (Pitt) is partnering with regional industry to provide innovative education and collaborative research programs in the areas of electric power, nuclear, and mining engineering. Working together with industry, along with strong government sponsorship and other constituency support, Pitt is contributing to solutions that address the aging workforce issue in the power and energy sector, as well as to advances in technology development, research transition, and outreach. Industry champions include Eaton Corporation, Westinghouse Electric Co., and CONSOL Energy. In addition, Pitt is playing an active role nationally through leadership involvement in the IEEE PES Power & Energy Engineering Workforce Collaborative, and is establishing a model program for the resurgence and sustainability of university based electric power and energy programs.

A renewed power and energy initiative development at the University of Pittsburgh Swanson School of Engineering

The University of Pittsburgh, Swanson School of Engineering has embarked on a proactive approach to the issues faced by the power and energy industries of an aging workforce, infrastructure degradation, and technology development deficiencies that have evolved somewhat unabated over the past several decades. A renewed power and energy program initiative has been developed with inclusive components to academic and research programs in three key areas: electric power, nuclear, and mining engineering. This inter-disciplinary program, entitled the Power and Energy Initiative, has been developed in close collaboration with industry partners and also supports strong synergies with the Schools Mascaro Sustainability Initiative, establishing a foundation for a comprehensive approach to energy and the environment. The Power & Energy Initiative includes renewed program options for undergraduate and graduate students and opportunities for faculty research activities across the Schools six departments (i.e., Chemical, Civil and Environmental, Electrical and Computer Engineering, Industrial, and Mechanical Engineering and Materials Science). The Power & Energy Initiative being implemented at the University of Pittsburgh is unique in its combination of electric power, nuclear, and mining engineering, in conjunction with sustainability; and thus provides a strong cross-disciplined level of diversity for student opportunities, faculty research areas, and industry and government participation. A description will be provided of the modernized educational curriculum and research programs that are being developed and implemented for the initiative. An overview will also be given on the unique opportunity that the Pittsburgh region provides for developing a strong industry-academia collaboration that can address the needs of the power and energy industries, and the role that industry has played in the initiatives development.

Modeling and characterization of a 300 V GaN based boost converter with 96% efficiency at 1 MHz

Presented here is experimental and simulated demonstration of a 96% efficient GaN based synchronous boost converter switching at 1 MHz. First, experimental implementation of the GaN based boost converter with 96% efficiency is established. A behavioral model of the GaN transistor is then developed in Saber, by reproducing five experimentally measured DC characteristics. The GaN device model is subsequently implemented in the same synchronous boost converter topology as in experimentation. It will be shown that the simulated converter topology, which consists of the GaN device models, is also capable of delivering power at an efficiency of at least 96%. Thus, the validated device model presented here will be utilized in the future to project the performance of the GaN transistors in larger more complex power conversion circuits, such as those often implemented in automotive and renewable energy applications.

Enhanced Performance of Bulk Heterojunction Solar Cells Fabricated by Polymer:Fullerene:Carbon-Nanotube Composites

By introducing single-walled carbon nanotubes (SWNTs) into bulk heterojunction (BHJ) organic solar cells made from blended films of regioregular poly (3-hexylthiophene) (P3HT) and methanofullerene (PCBM), the short circuit current of these devices has been increased up to 14% compared with the device without SWNTs. It is surmised that the increased short circuit current in P3HT:PCBM:SWNT devices is attributed to the increased carrier mobility of the active layer as the semiconducting SWNTs provide lower resistance pathways for carriers directly to the electrodes in contrast to the normal hopping conduction in P3HT:PCBM devices. We also observed the open circuit voltage has increased from 0.69 V in P3HT: PCBM devices up to 0.74 V in P3HT:PCBM: SWNT devices. The increased open circuit voltage might be attributed to the lower effective high occupied molecular orbital (HOMO) by introducing SWNTs. In this study, SWNTs have been shown to be excellent additives to enhance the performance of plastic bulk-heterojunction solar cells. However, we also observe the detrimental effect of the presence of metallic CNTs that causes hole-electron recombination, and as a result degrades the device performance. This calls for a critical need to enrich the semiconducting ones in bulk CNTs either from fabrication or from post-fabrication process.

Analytical and experimental optimization of external gate resistance for safe rapid turn on of normally off GaN HFETs

This paper presents an analytical framework, supplemented with experimental validation, for optimizing the value of the external gate resistance employed in power conversion circuits using EPC enhancement-mode GaN transistors. A second order analytical model of the GaN device is utilized to determine a function that relates the external gate resistance to the peak gate voltage during turn-on. The results obtained from the analytical model were experimentally validated in a double pulse-test. The derived model allows for optimal selection of gate resistances such that GaN HFETs can be switched as rapidly as possible while keeping them in their safe operating region.