This paper discusses the principle of operation, dynamic modeling, and control design for light-to-light (LtL) systems, whose aim is to directly convert the sun irradiation into artificial light. The system discussed in this paper is composed by a photovoltaic (PV) panel, an LED array, a dc-dc converter dedicated to the maximum power point tracking of the PV panel and a dc-dc converter dedicated to drive the LEDs array. A system controller is also included, whose goal is to ensure the matching between the maximum available PV power and the LED power by means of a low-frequency LEDs dimming. An experimental design example is discussed to illustrate the functionalities of the LtL system.

Light-to-Light: PV-Fed LED Lighting Systems

Among various photovoltaic (PV) maximum power point tracking (MPPT) techniques, variable-step incremental conductance (Inc.Cond.) method is widely employed with the merits of high tracking accuracy and fast convergence speed. Yet, mathematical division computations are mandatory for the algorithm's structure which in turn adds more complexity to its implementation. Moreover, conventional variable step, depending on the change of the array power with respect to the array voltage, encounters steady-state oscillations and dynamic problems especially under sudden irradiance changes. This paper proposes a modified variable-step Inc.Cond. MPPT technique featuring division-free algorithm, simplified implementation, and enhanced transient performance with minimal steady-state power oscillations around the MPP. Simulation and experimental results are presented for concept realization and performance evaluation.

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Modified variable-step incremental conductance maximum power point tracking technique for photovoltaic systems

What factors are most significant in understanding adoption behavior for energy efficiency technologies by commercial, residential, and industrial customers? The case of energy efficient lighting technologies is specifically examined. Several types of lighting technologies are compared to indoor LED lighting to determine how the technology meets the needs the various user types. What factors are most significant in motivating technology adoption for such technologies, and preventing subsequent technology disadoption? This is particularly important for energy efficient lighting technologies, as both technology adoption and technology disadoption can be extremely rapid, and ongoing user involvement is often required to recognize full benefits from these technologies. The Unified Theory of Acceptance and Use of Technology (UTAUT) is useful in explaining adoption behavior related to stakeholder expectation and buy-in for the new technologies. UTAUT contains four elements that can be adapted to fit this research: (1) Performance Expectancy; (2) Effort Expectancy; (3) Social Influences; and (4) Facilitating Conditions. In the case of energy efficient lighting adoption, and LED adoption in particular, performance expectancy and effort expectancy can be related to factors such as future energy price expectancies, actual savings results, and ease of energy savings. Factors involving social influences include perceptions of environmental friendliness among different user groups, and facilitating conditions include policies, incentives, and educational programs to encourage adoption. Some conclusions are then drawn regarding adoption factors for emerging energy efficient lighting technologies.

http://ieeexplore.ieee.org/iel5/6008221/6017605/06017904.pdf

Understanding adoption of energy efficiency technologies: Applying behavioral theories of technology acceptance & use to understand the case of led lighting for commercial, residential, and industrial end-users

This paper deals with the design of a PhotoVoltaic (PV)-fed Light Emitting Diode (LED) lighting system including an energy storage unit. The system is aimed at exploiting the generated energy in the absence of sunshine, provided that the power absorbed by the LED load can be varied within a power range corresponding to a sufficient lighting brightness. The main focus of this work is to discuss issues related to the sizing of the main components of the lighting system, i.e., the PV panel and the battery, for a dimmable LED load. The paper proposes a battery State Of Charge (SOC)-based LED dimming allowing to minimize the components' size. The discussion is based on the minimization of the following two quantities: 1) the excess of energy produced by the PV source, which the battery cannot store, and 2) the missing energy that the battery cannot deliver to the load. The application of the proposed methodology to a PV-fed LED-based street lighting system with dimmable LED load are presented and discussed.

Photovoltaic-fed LED lighting system with SOC-based dimmable LED load

Analysis and implementation of soft-switched bidirectional buck-boost DC-DC converter for solar PV–fed LED street lighting systems

This paper presents a novel high-performance standalone photovoltaic (PV) lighting system which can provide functional illumination based on high power White LEDs. An improved incremental conductance Maximum Power Point Tracking (MPPT) method is proposed in PV system to maximize the photovoltaic array output power, irrespective of the temperature and irradiation conditions and of the load electrical characteristics. A novel strategy to charge the battery is designed from the analyses and comparison results. In order to provide a steady-state operating environment for high power White LEDs, a specially designed LED drive module is implemented. Further more, a self-adapting dimming control is designed to maintain a stable indoor illuminance. Experimental results show the performance of the proposed photovoltaic lighting system.

Design and Implementation of a Novel High-performance Stand-alone Photovoltaic LED Lighting System

-High power LED (Light Emitting Diode) has a wide application in lighting for its good features. In this paper, the electrical properties of LED are first introduced, and then a series-parallel connection of LEDs with more stability and reliability is adopted on the basis of the features of parallel connection and series connection. After that, a flyback circuit for driving high power LED group with a constant-output-current is investigated, and the parameters are designed. According to the driving method, a circuit prototype with an output of 10.0V/1.10A is fabricated and tested in rated load and overload conditions to verify its current stability. Experimental results show that the LED drive circuit has a high accuracy, good stability and high efficiency, suggesting that the proposed method might be practical for driving high power LEDs. Keywords--LED lighting; flyback; constant current; drive circuit

Ye Ai

Papers

Design and Implementation of a Novel High-performance Stand-alone Photovoltaic LED Lighting System

Research on High-Efficiency Driving Technology for High Power LED Lighting