Noël Djongyang

Maximum power point tracking methods for photovoltaic systems operating under partially shaded or rapidly variable insolation conditions: a review paper

Abstract To increase the efficiency of photovoltaic (PV) systems, maximum power point (MPP) tracking of the solar arrays is needed. Under partially shaded conditions (PSCs), the solar arrays power–current (P–I) characteristic has multiple MPP. This paper presents various methods and approaches of tracking the MPP from a PV generator operating under PSC. Some comparisons, advantages, drawbacks and critical analysis of each method are discussed. It was found that, indirect methods use empirical data or mathematical expressions of numerical approximations to estimate the MPP from the PV generator’s voltage, current and irradiance. Direct methods offer the advantage of obtaining the actual maximum power from the PV generator’s voltage and current. Artificial intelligence methods do not need exact mathematical models. They can perform under parameter variation, load and supply voltage disturbances. Finally, novel methods require less number of iterations to converge, independent to the initial conditions. All these algorithms can be included in some of the DC/DC converters and MPP trackers for stand-alone or grid-connected systems.

An analytical-numerical approach in the calculation of photovoltaic module parameters operating under partial shaded conditions

The aim of this work is to determine the parameters and characteristics of a PV module in case of partial shading conditions. Both numerical and analytical methods are used in order to attain this objective. The iterative method namely Newton-Raphson is used to evaluate the characteristics of the PV module under partial shading conditions at its peak point. For various shading conditions, the lost power by the module is evaluated in order to show the influence of the partial shading conditions. The combined analytic method with the iterative method used allowed fairly accurate results on the behaviour of the shaded PV modules with less difficulties compared to the analytical method alone.

Operation and maintenance of back-up photovoltaic systems: An analysis based on a field study in Cameroon

This work is an analysis of the data collected from 20 photovoltaic installations all over Cameroon. The objectives are to study the causes of the breakdown of the different installations and propose maintenance strategies to solve them and to evaluate the field lifetime of the different elements of the PV systems. The data analyzed were obtained from maintenance records and measurements over a period of nine years (from 2007 to 2015). It appears from this analysis that 29% of the batteries went bad (leading to curative intervention), contributing to about 64.9% of the total breakdown registered. About 58.5% of the installed batteries were replaced during preventive visits; according to that, the estimated average life expectancy of the batteries installed in the 20 sites was six years. At the same time, considering the various failures caused by other items of the system, 50% of the systems received curative interventions within the first four years of the study, the other 50% received their first curative intervention only from the fifth year. This study also permitted us to evaluate the quantity of preventive and corrective maintenance impacts on solar PV systems.

Appraisal of geothermal resources and use in Cameroon

This paper deals with resources and opportunities of direct and indirect use of geothermal energy in Cameroon. Currently, no serious exploration and utilization of this resource exists. The primary form of utilization of geothermal energy is mainly condensation steam for drinkable water. Despite the availability and enormous potential in direct use applications, no use has been made of low enthalpy fluids. Several geothermal sites were identified using thermal methods. The results obtained from the geothermal gradient of Cameroon revealed the presence of temperatures able to produce electricity in the hottest spring of Woulndé (600°C). Other applications of geothermal energy in Cameroon are also discussed.

A proportional integral synthesis for a variable speed wind energy conversion system using a permanent magnet synchronous generator

A wind energy conversion system applied to battery charge is proposed in this paper. A permanent magnet synchronous generator (PMSG) is used as a variable speed generator in the proposed system. In order to extract the maximum power, the generator torque control is carried out by the pulse width modulation (PWM) converter, which requires controllers (PI controllers are used). A new approach is developed to settle easily and effectively the PI controller for the first order system. This approach is based on the compensation pole method. The system is simulated in the Matlab/Simpower environment and the results show that the new approach is better than the conventional method.