Development an Efficient Photovoltaic (PV) Configuration for Low Power Applications Omar Abdel-Rahim, IEEE Student Member, Mohamed Orabi, IEEE Senior Member, and Mahrous E. Ahmed, IEEE Member APEARC, South Valley University Aswan City 81542, Egypt orabi@ieee.org Abstract— this paper proposes a new technique for connecting PV modules with the grid at high efficiency in case of partial shading. Normally many PV modules connected in series with single unit of dc-dc converter which be affected seriously to a partial shading as the controller disconnects the whole string. Here each PV module is connected with a single dc-dc with high voltage gain converter, and then converters are connected in series to provide the required dc voltage level for the H-Bridge inverter to be coincident to the grid. So the proposed system can operate in the optimum condition even if shading occurs. MPPT control will be applied to each converter individually to assure that every PV module operates at its maximum power at every condition. As a result the whole system efficiency can be increased. A prototype has been built, tested for validation. Some selected simulation and experimental results have been provided. Keywords—PV module; Partial shading; Grid connection; MPPT; High Gain; High efficiency I. INTRODUCTION The use of photovoltaic (PV) modules as a source of renewable energy is gaining a lot of attention nowadays. PV modules may be operated as isolated system (standalone system) or grid connected, in both cases it must be connected to an inverter to convert the generated dc power into ac power. H-bridge Voltage Source Inverter (VSI) is a bucking inverter which almost requires a pre- stage boost dc-dc converter to generate a higher dc input voltage than its ac peak output voltage. The rated dc output voltage that can be obtained from the PV module is approximately a few tenths of voltage. On the other hand, the H-bridge inverter requires a dc input voltage not less than 311 V input for 220V grid. Then, few tens should be boosted into few hundred which give a requirement for a gain in the range on 10x (ten) or a little higher. This requires high conversion gain which is the main challenge. One direct solution to get rid of this challenge is to connect many PV modules in series forming a string with at least one-half to one-third (around 100V) of the required output voltage. However, this solution has its limitation for both practicality and technology faces. As a practical side, the environmental conditions specially shadow effects show a high contribution over PV string system. Unfortunately string configuration is very sensitive for environmental conditions such as shading phenomena. If any partial shaded strikes any part of any module, the system acts to remove the whole chain from operation however some modules can run if they are independently works, so the system generates a lower power. Therefore, it becomes preferable to attach a dc-dc converter into each module using a high voltage gain converter topology to increase the system efficiency. PV Systems are classified according to the connection of the PV modules. Figure 1 shows classification of PV systems which may be central, string or ac module [1]. The past technology, illustrated in Fig. 1 (a) was based on centralized inverters that interfaced a large number of PV modules to the grid. The PV modules were divided into series connections (called a string), each generating a sufficiently high voltage to avoid further amplification. These series connections were then connected in parallel, through string diodes, in order to reach high power levels. This centralized inverter includes some severe limitations, such as high-voltage dc cables between the PV modules and the inverter, power losses due to a centralized MPPT, mismatch losses between the PV modules, losses in the string diodes and a nonflexible design where the benefits of mass production could not be reached. The string inverter shown in Fig. 1 (b) is a reduced version of the centralized inverter, where a single string of PV modules is connected to the inverter. The input voltage may be high enough to avoid voltage amplification. This increases the overall efficiency compared to the centralized inverter, and reduces the prices due to mass production. The multi-string inverter depicted in Fig. 1 (c) is the further development of the string inverter, where several strings are interfaced with their own dc–dc converter to a common dc–ac inverter. This is beneficial, compared with the centralized system, since every string can be controlled individually. The ac module depicted in Fig. 1 (d) is the integration of the inverter and PV module into one electrical device. It removes the mismatch losses between PV modules since there is only one PV module, as well as supports optimal adjustment between the PV module and the inverter and hence the individual MPPT. It includes the possibility of an easy enlarging of the system, due to the modular structure. On the other hand, the necessary high voltage- amplification may reduce the overall efficiency and increase the price per watt, because of more complex 2010 IEEE International Conference on Power and Energy (PECon2010), Nov 29 - Dec 1, 2010, Kuala Lumpur, Malaysia 978-1-4244-8946-6/10/$26.00 ©2010 IEEE 622