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.

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Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques

This paper describes a complete digital PWM controller IC for high-frequency switching converters. Novel architecture and configurations of the key building blocks are A/D converter, compensator, and digital pulse-width modulator, are introduced to meet the requirements of tight output voltage regulation, high-speed dynamic response, and programmability without external passive components. The implementation techniques are experimentally verified on a prototype chip that takes less than 1 mm/sup 2/ of silicon area in a standard 0.5 /spl mu/ digital complementary metal oxide semiconductor (CMOS) process and operates at the switching frequency of 1 MHz.

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High-frequency digital PWM controller IC for DC-DC converters

Maximum power point (MPP) tracking (MPPT) techniques are widely applied in photovoltaic (PV) systems to make PV array generate peak power which depends on solar irradiation. Among all the MPPT strategies, the incremental-conductance (INC) algorithm is widely employed due to easy implementation and high tracking accuracy. In this paper, a novel variable step-size incremental-resistance MPPT algorithm is introduced, which not only has the merits of INC but also automatically adjusts the step size to track the PV array MPP. Compared with the variable step-size INC method, the proposed scheme can greatly improve the MPPT response speed and accuracy at steady state simultaneously. Moreover, it is more suitable for practical operating conditions due to a wider operating range. This paper provides the theoretical analysis and the design principle of the proposed MPPT strategy. Simulation and experimental results verify its feasibility.

A Novel Improved Variable Step-Size Incremental-Resistance MPPT Method for PV Systems

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.

/pdf/a-multiple-input-dc-dc-converter-topology-1fuytwf042.pdf

A multiple-input DC-DC converter topology

The photovoltaic (PV) system is one of the renewable energies that attract the attention of researchers in the recent decades. The PV generators exhibit nonlinear I–V and P–V characteristics. The maximum power produced varies with both irradiance and temperature. Since the conversion efficiency of PV arrays is very low, it requires maximum power point tracking (MPPT) control techniques. The maximum power point tracking (MPPT) is the automatic control algorithm to adjust the power interfaces and achieve the greatest possible power harvest, during moment to moment variations of light level, shading, temperature, and photovoltaic module characteristics. The purpose of the MPPT is to adjust the solar operating voltage close to the MPP under changing atmospheric conditions. It has become an essential component to evaluate the design performance of PV power systems. This investigation aims to assess different MPPT techniques, provide background knowledge, implementation topology, grid interconnection of PV and solar microinverter requirements presented in the literature, doing depth comparisons between them with a brief discussion. The MPPT merits, demerits and classification, which can be used as a reference for future research related to optimizing the solar power generation, are also discussed. Conventional methods are easy to implement but they suffer from oscillations at MPP and tracking speed is less due to fixed perturb step. Intelligent methods are efficient; oscillations are lesser at MPP in steady state and tracked quickly in comparison to conventional methods.

MPPT techniques for photovoltaic applications

Recently, clean electric power generation systems have attracted a great deal of social attention to exploit clean energy resources such as solar arrays, wind generators, fuel cells, etc. In this case, the multiple-input DC-DC power converter is useful to combine the several input power sources and to supply the regulated output voltage for the load. The novel solar cell power supply system using the buck-boost type two-input DC-DC converter is proposed, in which the solar array and the commercial AC line are exploited as power sources and they are combined by the two input windings of the energy-storage reactor. Also, its operation principle and performance characteristics are discussed. Furthermore, the solar cell optimum operating point tracker is proposed and examined. It is confirmed by the experiment that the proposed solar cell power supply system has the excellent performance characteristics.

Novel solar cell power supply system using the multiple-input DC-DC converter

When the solar array is used as an input power source, the optimum operating point tracker is often employed to exploit more effectively the solar array as an electric power source and to obtain the maximum electric power at all times even when the light intensity and environmental temperature of the solar array are varied. Usually, the optimum operating point is determined by computing the electric power from the solar array power supply with a microcomputer, DSP and so forth. However, such a method has the problems of the complex control circuit configuration, high cost and low control speed. From this viewpoint, this paper proposes a new optimum operating point tracker of the solar cell power supply system, in which inexpensive pn-junction diodes are used to generate the reference voltage of the operating point of the solar array. Using the proposed method, the high degree of the solar array optimum point tracking performance can be obtained, even when the light intensity and environmental temperature of the solar array are varied. Furthermore, the proceeding paper provides the operation principle, design-oriented analysis and so forth, of the proposed solar cell power supply system.

A novel optimum operating point tracker of the solar cell power supply system

This paper presents a new combined voltage-resonant inverter for electronic ballasts of fluorescent lamps, in which the voltage-resonant active filter and inverter are combined, and a switch of the active filter is used simultaneously with that of the inverter. The performance characteristics of this combined inverter is analysed. As a result, it is clarified that there exists a useful operation mode in the discontinuous reactor current region, and that the high power factor of 99% and the low input current distortion factor of 2% can be achieved by using this operation mode. >

A new combined voltage-resonant inverter with high power factor and low distortion factor

The digitally controlled DC-DC power converter has an advantage of high reliability, high controllability and high flexibility. A new digital controller for PWM and/or PFM controlled switching DC-DC power converters is presented, which is versatile in general use such as switching frequency from 20 kHz to 500 kHz, hard-switching and soft-switching.

Novel digital controller for the PWM and/or PFM controlled switching DC-DC converters

In the conventional digitally controlled DC-DC power converter with current-injected control, the overcurrent cannot be suppressed because of the intrinsic characteristics of the voltage-controlled oscillator (VCO) as an analog-to-digital signal converter. This paper presents a new digital current-injected control circuit to realize the overcurrent limiting characteristics and the design-oriented analysis of the overcurrent limiting characteristics of the proposed digitally controlled DC-DC power converter.

H. Matsuo

Papers

Novel solar cell power supply system using the multiple-input DC-DC converter

A novel optimum operating point tracker of the solar cell power supply system

A new combined voltage-resonant inverter with high power factor and low distortion factor

Novel digital controller for the PWM and/or PFM controlled switching DC-DC converters

Overcurrent limiting characteristics of the DC-DC converter with a new digital current-injected control circuit