A combined scheme for maximising the output power of a Photovoltaic array under partial shading conditions

The power generation performance of a solar array can be enhanced by using a scheme that combines various techniques, including Maximum Power Point Tracking (MPPT), a PV array reconfiguration, and DC-DC converters for current and voltage matching. This paper presents a novel combination of three techniques and a closed-loop control strategy to improve the performance of a large PV array initially in Tied-Cross-Ties (TCT) interconnection. Firstly a modified Magic Square-Enhanced Configuration (MS-EC) is used to permute the module positions in the array. The chosen example is a 6x6 TCT array. The resultant arrangement is then divided into four 3x3 TCT sub-arrays. Irradiance Equalisation (IE) is applied to each sub-array to make the irradiation levels match approximately between its rows. Finally, a Series-Parallel Differential Power Processing (SP-DPPs) converter scheme is applied to the four sub-arrays for maximum power point tracking. Experimental tests are presented to validate the transfer function models of these converters and the designed control scheme. The combined scheme performance is evaluated under static and dynamic shading patterns; it compares favourably with a TCT array using only bypass diodes by showing an average power gain of 11-48% and an efficiency of 98.95%.