Controller design for integrated PV-converter modules under partial shading conditions

Module-integrated PV and converter units have been a promising technique for achieving maximum power generation for mismatching and/or partially shaded PV modules. Control of a PV system with multiple such units is difficult as the operation of each unit is required to be regulated to generate the maximum power according to its respective light level. This paper presents a novel model-based, two-loop control scheme for a particular MIPC system, where bidirectional Cuk dc–dc converters are used as the bypass converters and a terminal Cuk boost functioning as a whole system power conditioner. Experimental tests of example systems consisting of two and three serially connected units are presented showing that the proposed system can increase power generation as much as 30%, compared to the conventional bypass diode structure. In general with n modules in series the maximum power gain is expected to be (100/n)%. The new control scheme is developed using analytical expressions for the transfer functions of the power converters. The control results showing rapid and stable responses are superior to that obtained by bypass diode structure which is conventionally controlled using Perturbation-and-Observation method.

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