Analytical MPPT for PV water heating system based on inverter input impedance

Carrying out maximum power point tracking (MPPT) is of utmost importance in photovoltaic (PV) systems to ensure high-efficiency power generation. A type of PV system which has not received much attention in MPPT literature is the photovoltaic water heating system (PWHS). The few existing PWHS-specific MPPT approaches in the literature suffer either from low efficiency, complex implementation or significant sensitivity to sample time. Taking this into account, the present work has the objective of proposing a novel MPPT approach for PWHSs that avoids all aforementioned difficulties. The proposed approach is analytical and its main innovation consists in estimating the PV inverter input impedance, which enables the direct computation of duty cycle. Validation is carried via computer simulations, in which comparison to three MPPT methods for PWHSs is considered. Obtained results show that the proposed method yields MPPT energy efficiency improvements of: (a) 0.79%, 1.18% and 11.12% with respect to the other three methods; (b) 0.59% and 0.90% under dynamic irradiance and temperature, respectively, compared to the second-best method; and (c) 7.55%, in average, for varying sample time when compared to the second-best method. At last, the proposed method is seen to be robust with respect to impedance estimation error and maintains peak efficiency for a 37% error margin.