Analysis of perturbation step size for perturb and observe photovoltaic maximum power point tracking algorithm

Abstract

In recent years, climate change has created an enormous concern to everyone. One of the main concerns is the use of fossil fuels that have been identified as one of the main contributors to the greenhouse effect through the production of CO2 as a waste product. In addition to that, the fast developments of industries have made great inroads into the non-renewable fossil fuel. The negative environmental impacts and fossil fuels depletion remain as great challenges to energy production. Therefore, renewable energies have been brought into use. Among them, solar or photovoltaic (PV) energy is one of the most promising energy resources because it is free of fuel costs, environmental friendly and motionless. There are several significant experiences within European member countries with PV system. The ‘Campaign for Take-Off’ launched by European Commission seeks to install a total capacity of 1 GWp PV power by 2010 [1] to promote decentralised electrification in developing countries and in the EU-wide domestic market. In addition to that, the largest PV power plant in the world, which has the plant capacity of 5 MWp, went on stream in August 2004 in Germany [2]. Although the rapid development of photovoltaic materials technology and the increased demands for PV materials have led to a reduction of the PV module costs [3] the capital costs of PV systems are still very high. Thus, there is a necessity to design a power converter that is not only high in efficiency but also optimizes the energy production of the PV material. A maximum power point tracking (MPPT) algorithm is commonly applied in power converters to maximize the power drawn from PV modules under varying atmospheric conditions. This is to ensure that the best use of the PV array in producing clean electricity is made. Among the MPPT algorithms, the Perturb and Observe MPPT method is the popularly used due to the simplicity of its control structure [4]. However, there have been relatively few studies [4, 5] made on the influence of applying perturbation step-sizes in P&O algorithm. Therefore, this chapter aims to investigate and evaluate the effect of applying different perturbation step-sizes on the P&O MPPT algorithm. This chapter begins with a review of PV characteristics and proceeds with a review of available MPPT algorithms. Subsequently, the P&O MPPT algorithm and perturbation stepsizes are explained. The power converters which include a direct duty-cycle controlled boost converter and a current-mode controlled boost converter are briefly discussed. Then, the simulation results of the effect using different perturbation stepsizes are described analyzed.