Patrick L. Chapman

Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques

The many different techniques for maximum power point tracking of photovoltaic (PV) arrays are discussed. The techniques are taken from the literature dating back to the earliest methods. It is shown that at least 19 distinct methods have been introduced in the literature, with many variations on implementation. This paper should serve as a convenient reference for future work in PV power generation.

A multiple-input DC-DC converter topology

A new topology for multiple energy source conversion is presented. The topology is capable of interfacing sources of different voltage-current characteristics to a common load, while achieving a low part count. A fixed frequency switching strategy is investigated and the resulting operating modes are analyzed. The analysis is verified by experimentation. The results show that the converter is an enabling technology for power diversification and optimization.

Power budgeting of a multiple-input buck-boost converter

The use of a multiple-input buck-boost converter for budgeting power between different energy sources is discussed. It is shown mathematically that the idealized converter can accommodate arbitrary power commands for each input source while maintaining a prescribed output voltage. Power budgeting is demonstrated experimentally for a real converter under various circumstances, including a two-input (solar and line-powered) system. A closed-loop control example involving simultaneous tracking of output voltage and set-point tracking of the solar array shows that an autonomous system is realizable.

Modulation-Based Harmonic Elimination

A modulation-based method for generating pulse waveforms with selective harmonic elimination is proposed. Harmonic elimination, traditionally digital, is shown to be achievable by comparison of a sine wave with modified triangle carrier. The method can be used to calculate easily and quickly the desired waveform without solution of coupled transcendental equations

Selective harmonic control: a general problem formulation and selected solutions

Selective harmonic elimination/control has been a widely researched alternative to traditional pulse-width modulation techniques. Previous and current work has made fundamental assumptions that enforce output waveform quarter-wave symmetry, presumably in order to reduce the complexity of the resulting equations. However, the quarter-wave symmetric assumption is not strictly necessary. It restricts the solution space, which can result in sub-optimal solutions with regards to the uncontrolled harmonic distribution. A more general formulation is proposed, removing the quarter-wave symmetry constraint for two classes of the m-level, n-harmonic harmonic control problem. The special cases of two- and three-level harmonic elimination are presented in detail along with representative solutions for each harmonic control problem. New solutions previously unattainable based on quarter-wave symmetric techniques are identified.

Modeling the Effect of Voltage Ripple on the Power Output of Photovoltaic Modules

This paper proposes a model for the static power loss in photovoltaic (PV) panels due to switching-frequency ripple. Small-signal modeling is used to determine the amplitude of the voltage ripple that is imposed on the PV panel, and a closed-form expression is developed for the output power. The expression is shown to be more accurate than the power loss that was predicted by small-signal modeling alone, resulting in a median error of 0.8%. The model presented allows dc-dc converter designers to more precisely choose the input filter components that are critical during times of low insolation.

Development of three-dimensional inductors using plastic deformation magnetic assembly (PDMA)

On-chip inductors are critical for enabling portable power-efficient wireless communication systems. Existing on-chip spiral inductors based on conventional planar integrated-circuit fabrication technology suffer from substrate loss and parasitics, and have relatively large footprints. In this paper, we discuss the development of two types of on-chip three-dimensional (3-D) inductors-a vertical spiral inductor and a solenoid inductor-by using a 3-D assembly process called plastic deformation magnetic assembly. Prototype vertical spiral inductors and solenoid inductors have been fabricated and tested. Experimental results show that the vertical spiral inductors can achieve better performance and a smaller footprint than the in-plane ones.

A Unified Approach to Reliability Assessment of Multiphase DC–DC Converters in Photovoltaic Energy Conversion Systems

A systematic framework for reliability assessment and fault-tolerant design of multiphase dc-dc converters deployed in photovoltaic applications is presented. System-level steady-state models allow a detailed specification of component failure rates, and in turn establish the effects of ambient conditions and converter design on reliability. Markov reliability models are derived to estimate the mean time to system failure. Case studies applied to two- and three-phase, 250-W converters demonstrate that topological redundancy does not necessarily translate to improved reliability for all choices of switching frequency and capacitance. Capacitor voltage rating is found to be the dominant factor that affects system reliability.

Evaluation of motions and actuation methods for biomechanical energy harvesting

This paper addresses energy harvesting from biomechanical motions. Such a technique is useful for powering small portable devices, such as wireless phones, music players, and digital assistants. For very low power devices, biomechanical energy may be enough to provide baseload power. In others, such as cell phones (which typically requires up to 3 W), biomechanical energy would recharge batteries for extended use between line charges, or allow for peak just-in-time power. In this paper, we consider several biomechanical motions for power generation. We evaluate actuation methods, including magnetic, piezoelectric, electrostatic, and electrical polymers for various motions in terms of energy, power, mass, and cost. We also discuss the practical issues associated with each, especially in terms of the power electronics required to connect the biomechanical sources to useful loads.

Telecommunications Power Plant Damage Assessment for Hurricane Katrina– Site Survey and Follow-Up Results

This paper extends knowledge of disaster impact on the telecommunications power infrastructure by discussing the effects of Hurricane Katrina based on an on-site survey conducted in October 2005 and on public sources. It includes observations about power infrastructure damage in wire-line and wireless networks. In general, the impact on centralized network elements was more severe than on the distributed portion of the grids. The main cause of outage was lack of power due to fuel supply disruptions, flooding and security issues. This work also describes the means used to restore telecommunications services and proposes ways to improve logistics, such as coordinating portable generator set deployment among different network operators and reducing genset fuel consumption by installing permanent photovoltaic systems at sites where long electric outages are likely. One long term solution is to use of distributed generation. It also discusses the consequences on telecom power technology and practices since the storm.