NEW MAXIMUM POWER POINT TRACKING MPPT ALGORITHM BASED ON RESEARCH OF A TARGET VOLTAGE RANGE AND ITS IMPLEMENTATION IN A COMMERCIAL INVERTER FOR PHOTOVOLTAIC SYSTEMS

摘要

The performance of PV systems, especially in urban environment, are effected by the partial shading of the PV modules, which can be due to the presence of obstacles like, chimneys, antennas, adjacent buildings, trees or due to non-uniform soiling and eventual damaged PV cells. The dynamic variations of the partial shading as well as of the solar irradiance on the PV strings cause a continuous shape-changing of the PV system power-voltage (P-V) characteristics. Depending on the module electrical layout, many local power peaks can appear in the P-V curves making difficult the identification of the maximum power point (Pmax) by the inverters. Under these conditions, Maximum Power Point Tracking (MPPT) algorithms can fail identifying the absolute power peak and/or have a too slow convergence rate, involving energy losses. In this contribution a new smart MPPT algorithm which can quickly identify the target voltage range that includes the absolute power point Pmax, is presented. The new MPPT has been implemented in the control logic of a commercial inverter (Inverter RSE-BDF) and by using a PV curve simulator comparative tests have been carried out with other inverters present in the market. It is shown that under the more critical scenario, where P-V curves with several peaks and frequent irradiance variations are generated by the PV simulator, the MPPT efficiency of the Inverter RSE-BDF presented a dynamic efficiency, calculated according to the IEC 6289, up to 45% higher than the tested commercial inverters.