This paper presents a comprehensive overview on various maximum power point tracking (MPPT) techniques, which have been recently designed, simulated and/or experimentally validated in the PV literature. The primary goal of each MPPT technique is to optimize the output of shaded/unshaded photovoltaic (PV) array under static and dynamic weather conditions. Though each MPPT technique has its own pros and cons, an optimized MPPT technique is characterized in many aspects like hardware and software simplicity, implementation, cost effectiveness, sensors required, popularity, accuracy and convergence speed. In this paper the rating of various MPPT methods has been done based on the benchmark P&O method. The rating criteria is separately calculated for the techniques that are capable to work in full-sun and partial shading conditions. A rule based table is set to evaluate the MPPT against the algorithm's complexity, hardware implementation, tracking speed, and steady state accuracy or detection of global maximum. Moreover, special consideration has been given to bio-inspired MPPT algorithms. The bio-inspired algorithms are compared side by side with their specific application in PV system. A tree diagram is also designed to see the emergence of partial shading algorithms over a period of time. The traits presented in this paper are novel and provide bottom-line for the researchers to select and implement an appropriate MPPT technique.
The worldwide energy demand is increasing on a faster pace than the energy generation because of enhanced industrialization, growing population and improved living standards. According to international energy agency (IEA) reports, the energy consumption of world will increase by 44% from 2006 to 2030 . In the present scenario, the fossil fuels such as oil, gas and coal are depleting with every passing day, which are the primary energy drivers and pollution contributors [2–4]. Therefore, the world is moving to new energy resources, which are promising, socially compatible, renewable, and sustainable. These sources are solar, wind, biomass, small hydro, geothermal, and ocean tidal/thermal. Photovoltaic (PV) is a prominent renewable energy source due to its sustainability, local availability, environmental friendly nature, simple technology, increasing cost effectiveness and less balance of systems. In photovoltaic, the sunlight is converted into direct current using semiconductor materials without any moving parts and carbon emissions. For the past decades, the power generation from PV systems have showed extensive penetration in commercial and domestic facilities. PV has now turned into the third most essential renewable energy source after hydro and wind. At present, more than 100 nations are utilizing ground mounted or building integrated PV systems for domestic, commercial and grid applications. According to IEA-PVPS (international energy agency for photovoltaic power systems), the worldwide installed PV capacity has expanded to 227 GW in March 2015 and is expected to reach up to 500 GW by the end of 2020 [5,6]. The current-voltage (I-V) curve of PV array relies on irradiance and temperature conditions. When the irradiance increases with constant temperature, the photovoltaic current also increases in direct proportion with negligible effect on PV voltage. Similarly, if the temperature increases with constant irradiance, the PV voltage decreases substantially while the PV current increases slightly. Under uniform condition, PV array exhibits unique maximum power point (MPP) on its I-V curve. The tracking mechanism in PV system, known as maximum power point tracking (MPPT) technique, is inevitable to search the MPP as innate characteristic of PV varies non-linearly with irradiance, temperature, and load.