A Parameter Estimation Based MPPT Method for a PV System Using Lyapunov Control Scheme

There are two types of external variations that change the operating point of a photovoltaic (PV) system: one is environmental change caused by variation in temperature and/or irradiance and the other is load change. The variation in environmental condition changes the PV array characteristic itself, whereas the load variation changes the operating point within the same curve. Each type of change can be uniquely identified using history of PV voltage and current measurements. Using the above fact, this paper proposes a fast maximum power point tracking (MPPT) technique for a PV array coupled with boost converter. The proposed method determines MPP in a single step by finding out temperature and irradiance at which the PV array is operating. Furthermore, based on the measured values of PV voltage and current, inductor current and load voltage are also calculated, eliminating the need for additional sensors. Lyapunov-based controller is implemented to track inductor current to its desired value and find the desired duty cycle to reach MPP. The proposed method is validated by both simulation and experimental results under varying temperature, irradiance, and load condition. A comparison with the existing MPPT method is also presented in order to show the efficacy of the proposed method.