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

• Published in: Solar energy 2013-06, Vol.92, p.123-138
• Main Authors: Chong, B.V.P., Zhang, L.
• Format: Article
• Language: English
• Subjects: Applied sciences; Bypasses; Control systems; Controllers; Converters; Design; Diodes; Direct energy conversion and energy accumulation; Electric power plants; Electrical engineering. Electrical power engineering; Electrical machines; Electrical power engineering; Electricity generation; Energy; Exact sciences and technology; Exact solutions; Integrated converter; Light levels; Mathematical models; Maximum power; Maximum power point tracking; Miscellaneous; Modules; Natural energy; Partial shading; Photoelectric conversion; Photovoltaic cells; Photovoltaic conversion; Photovoltaic system; Regulation and control; Solar cells. Photoelectrochemical cells; Solar energy; Ćuk converter
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2013.01.025

► The operating principles for integrated PV-Ćuk converter are fully analysed. ► Novel scheme in controlling the integrated PV-Ćuk converter is developed. ► Closed-loop controller based on converters’ transfer functions is implemented. ► The scheme is successfully applied under a wide range of shading conditions. ► Experimental work showed that this scheme increases power generation by 30%. 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 Ćuk dc–dc converters are used as the bypass converters and a terminal Ćuk 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.