Performance Study of Photovoltaic Power-Slope-Aided Incremental-Conductance Maximum Power Point Tracking

Abstract

An approach of power-slope (PS) plus incremental-conductance (INC) maximum power point tracking (MPPT) for photovoltaic (PV) energy conversion is presented. Two kinds of tracking phases simultaneously execute the MPPT tracking according to the instant sensed current difference (ΔI) and power difference (ΔP). Reference tracking criteria, power slope Sp = ΔP/ΔV → 0 and incremental conductance mI = ΔI/ΔV →-I/V are concurrently as the tracking drives executing to fast and precisely reach the maximum power point (MPP). In the left-hand side (LHS) of the MPP and before reaching the specified INC-tracking zone (INC-TZ), PS-tracking on the P-V curve is instead of the INC-tracking since the sensed ΔI is tiny and ambiguous on the I-V curve, in contrast, in the right-hand side (RHS), both PS-tracking and INC-tracking are available due to the sensed ΔI obvious. Inside the INC-TZ around MPP, INC-tracking on the I-V curve is the dominant tracking for final approaching to the MPP while the PS-tracking is still valid to aid the tracking settle at MPP. Model predictive control (MPC) is employed to predict the future tracking trajectory as per the detected Sp and mI, which can fast and accurately perform the PS-INC MPPT in either PS-tracking or INC-tracking process toward the MPP. An experimental setup of 10 kW PV buck-mode energy storage using PS-INC MPPT is demonstrated and the results are compared with the INC MPPT and the PI-INC MPPT approaches.