A simple hybrid MPPT technique for photovoltaic systems under rapidly changing partial shading conditions

Maximum power point tracking (MPPT) is an important strategy to increase the power output from photovoltaic (PV) systems. Partial shading of PV panels is a serious problem which leads to multiple local maximum power points (MPPs) on the power versus voltage (P-V) curve. These multiple MPPs can result in conventional MPPT algorithms becoming trapped at a local MPP, resulting in a significant power loss. This paper presents a hybrid MPPT method to optimize the power output for the PV system under non-uniform conditions. It samples the operating point at locations on the I-V curve when partial shading is detected and uses these values to predict the global MPP region. After that, a conventional MPPT algorithm efficient for unimodal functions, such as P&O or extremum seeking control (ESC), is applied to the local area so that the system reaches the global MPP. Since it does not require irradiance sensors and can directly predict the MPP region, it features a relatively low cost, fast response, and simple structure. The effectiveness of the proposed MPPT method is verified with simulation results. A comparison with other popular MPPT techniques shows the advantages with respect to its fast tracking speed and high accuracy.