PV Energy Harvesting Under Extremely Fast Changing Irradiance: State-Plane Direct MPPT

Abstract

Photovoltaic cells require maximum power point tracking (MPPT) algorithms to ensure that the amount of power extracted is maximized. True seeking, direct duty cycle control MPPT algorithms are a simple and straightforward solution that can provide high tracking efficiency. In these algorithms the duty cycle is traditionally modified to reach a new steady state prior performing a new MPPT iteration. Therefore, the MPPT update period must be larger than the converter's settling time to reach a new steady state, which limits the dynamic tracking performance. This paper proposes a novel direct duty cycle control method that does not require the converter to achieve steady state in between MPPT updates. The proposed method benefits from the natural oscillations occurring in the converter to obtain extreme dynamic tracking improvements while maintaining simple implementation with no need of employing temperature or irradiance sensors. The scheme being introduced combines MPPT concepts with large-signal geometric control to achieve a reliable, high-performance solution very suitable for applications with rapidly changing irradiance, such as wearable technology and rooftop electric vehicle (EV). The theoretical analysis is supported by detailed mathematical procedures and validated by simulations and experimental results.