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 presents a detailed analysis of the two most well-known hill-climbing maximum power point tracking (MPPT) algorithms: the perturb-and-observe (P&O) and incremental conductance (INC). The purpose of the analysis is to clarify some common misconceptions in the literature regarding these two trackers, therefore helping the selection process for a suitable MPPT for both researchers and industry. The two methods are thoroughly analyzed both from a mathematical and practical implementation point of view. Their mathematical analysis reveals that there is no difference between the two. This has been confirmed by experimental tests according to the EN 50530 standard, resulting in a deviation between their efficiencies of 0.13% in dynamic and as low as 0.02% under static conditions. The results show that despite the common opinion in the literature, the P&O and INC are equivalent.

On the Perturb-and-Observe and Incremental Conductance MPPT Methods for PV Systems

A dynamically rapid method used for tracking the maximum power point of photovoltaic arrays, known as ripple correlation control, is presented and verified against experiment The technique takes advantage of the signal ripple, which is automatically present in power converters The ripple is interpreted as a perturbation from which a gradient ascent optimization can be realized The technique converges asymptotically at maximum speed to the maximum power point without the benefit of any array parameters or measurements The technique has simple circuit implementations

/pdf/dynamic-maximum-power-point-tracking-of-photovoltaic-arrays-1wf6q56i9a.pdf

Dynamic Maximum Power Point Tracking of Photovoltaic Arrays Using Ripple Correlation Control

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

In this paper, the concept of power tracking for PV systems is highlighted and an overview on 40 old and recent Maximum Power Point Tracking (MPPT) methods, available in the literature, is presented and classified. These methods are mathematically modeled and presented in such a way the reader can select the most appropriate method for his own application. A comparative table is presented at the end of the paper to simplify the classification of the different methods.

General review and classification of different MPPT Techniques

In this paper, the authors proposed a novel maximum power point controller, which not only can track the maximum power of an array quickly without perturbation and observation process but also can be implemented easily. The main idea is based on the graphical interpretation of the maximum power point as the intersecting point of two curves on the phase plane corresponding to the solution of two algebraic equations. In other words, the operating point is the intersecting point of the PV-array characteristic curve and the maximum power line. A circuit is constructed based on a boost circuit and a three phase full bridge inverter.

A fast maximum power point tracker for photovoltaic power systems

In this paper, analytic duty cycle control laws for a three-phase step up/ down converter containing seven active switches are first derived to achieve a clean sinusoidal input current, adjustable power factor, bidirectional power flow capability and clean output DC voltage. Then a DC model and a small signal model are derived by means of coordinate transformation, perturbation and linearization. Finally, some simulation results are also presented to verify the validity of the theoretical results.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1934-6093.1999.tb00007.x

Modeling of a three‐phase step up/down ac/dc converter

In this study top emission organic light-emitting diodes (TE-OLED) were successfully fabricated on flexible PET/multilayer disordered silver nanonetwork (MDSN) substrate with conventional LiF/Al as a semitransparent cathode and Ag as a reflective anode. The effects of the hole injection layer, anode buffer layer, and an electron injection layer on the luminescence characteristics of TE-OLEDs were investigated. At first, the thickness of cathode Al is adjusted based upon the overall transmittance of the top-emission cathode and its conductivity. There is a high energy barrier for the hole between the work function of the anode Ag (4.2 eV) and the NPB highest occupied molecular orbital (HOMO) energy level (5.5 eV), which is not favorable for hole injection. This study tested four types of hole injection layer (HIL) materials. Finally, MoO3 was selected as an optimal HIL material, and the optimum thickness was adjusted, enabling the hole to be injected smoothly from the anode to the NPB and then to an emitting layer. The TE-OLED luminance reached 268 cd/m2. There is a high energy barrier between the work function of Ag and MoO3 HOMO (5.3 eV)—about 1.1 eV—which is still not conducive to the hole injection, so a thin layer of high work function metal Au (work function 5.1 eV) was added to the top of the anode silver, which more matches with the MoO3 energy level. It can make the hole easier to inject from the anode to MoO3 (HIL) and protect the silver from oxidation. At 8 V, the luminance is increased to 413.7 cd/m2, and the current efficiency is 0.81 cd/A. The luminance is significantly improved. An electron transport/hole blocking layer TPBi (10 nm) was added to enhance the electron transport capability and effectively block the holes with higher electron mobility and a higher HOMO energy level of TPBi. So that more holes can remain in the emitting layer and increase the chance of the electron-hole recombination to improve the luminance and current efficiency of TE-OLED. At 8 V, the luminance and current efficiency can reach 611.4 cd/m2 and 0.95 cd/A, respectively.

The Selection of Anode and Cathode Materials for Top Emission Organic Light-Emitting Diodes

Reversible hybrid control resonant converter for electric vehicle battery charging and discharging system

In this paper, a blue fluorescent organic light-emitting diode (OLED) with a 1 cm2 emitting area was fabricated by a solution process. The ITO/spin MADN:13% UBD-07/TPBi/Al was used as the basic structure in which to add a hole-injection layer PEDOT:PSS and an electron-injection layer LiF, respectively. The device structure was optimized to obtain a longer lifetime. Firstly, the TPBi, which is an electron transport layer and a hole-blocking layer, was added to the structure to increase the electron transport rate. When the TPBi thickness was increased to 20 nm, the luminance was 221 cd/m2, and the efficiency was 0.52 cd/A at a voltage of 8 V. Since the addition of the hole-injection layer (HIL) increased the hole current but did not increase the electron current, the electron transport layer (ETL) Alq3 with the lowest unoccupied molecular orbital (LUMO) was added as stepped ETL to help the TPBi transport more electron current into the emitting layer. When the thickness of the TPBi/Alq3 was 10 nm/15 nm, the luminance reached 862 cd/m2, the efficiency was 1.29 cd/A, and the lifetime increased to 252 min. Subsequently, a hole-injection layer PEDOT:PSS with a thickness of 55 nm was added to make the ITO surface flatter and to reduce the probability of a short circuit caused by the spike effect. At this time, the luminance of 311 cd/m2, the efficiency of 0.64 cd/A, and the lifetime of 121 min were obtained. Following this, the thickness of the emitting layer was doubled to increase the recombination probability of the electrons and the holes. When the thickness of the emitting layer was 90 nm, and the thermal evaporation method was used, the efficiency was 3.23 cd/A at a voltage of 8V, and the lifetime was improved to 482 min. Furthermore, when the thickness of the hole-injection layer PEDOT:PSS was increased to 220 nm, the efficiency increased to 3.86 cd/A, and the lifetime was increased to 529 min. An infrared thermal image camera was employed to detect the temperature variation of the blue OLEDs. After the current was gradually increased, it was found that the heat accumulation of the device became more and more significant. When the driving current reached 50 mA, the device burnt out. It was found that the maximum temperature that the OLED device could withstand was approximately 58.83 degrees C at a current of 36.36 mA.

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Jeng-Yue Chen

Papers

A fast maximum power point tracker for photovoltaic power systems

Modeling of a three‐phase step up/down ac/dc converter

The Selection of Anode and Cathode Materials for Top Emission Organic Light-Emitting Diodes

Reversible hybrid control resonant converter for electric vehicle battery charging and discharging system

Lifetime Comparisons of Organic Light-Emitting Diodes Fabricated by Solution and Evaporation Processes