سیستم فتوولتاییک-باتری برای ساختمان سبز هوشمند توسط مبدل DC-DC همراه ترانسفورماتور

ABSTRACT PV-battery system for smart green building using transformer coupled DC-DC converter

Remote rural areas that live off the grid can benefit from a home photovoltaic cell system. A photovoltaic home system can be defined as a standalone system suitable for a wide range of residential applications such as home appliances; lightning computer and water pumping.

The system is used to supply both DC and AC for home electrical devices with help of proper DC-DC converters and DC-AC inverters. They can be used for power up to a load 300VA. These basic loads include fan; mobile phone chargers; lamps; TV; Radio; etc. Conventional standalone photo voltaic system consist of three power electronics converters.They are maximum power point (MPPT) tracker;battery charge controller and an inverter for feeding the AC loads. MPPT controller extracts maximum power from PV panel. Whereas charge controller enhances the efficiency of battery and its life time by controlling proper charging and discharging of battery under varies SOC levels. PV panel of 12 V or 24 V and a battery of usually 12V or 24 V is common in such stand-alone systems. Due to lower voltage input; these systems require additional boosting of voltage through a transformer. As the no of converters and transformer increases it will increase size and cost of the system.

Use of a system with integrated maximum power point tracking and battery charging control is advantageous for system which require low cost and higher reliability[2][3][4]. A standalone PV system is usually designed with low voltage levels for the PV and the battery in the range 12V or 24V;such systems will be requiring additional boosting up if the input voltage is low. These systems will be using low frequency step up transformer at the inverter output end. However these will increases the no of switches and more no of converter stages which will reduce the overall efficiency of the system.

To address above mentioned issue; the high-gain requirement can be provided through intermediate dc-dc converters which interface the PV and battery. This can be realized by employing three stages of dc-dc conversion. But;the use of more number of converters leads to poor efficiency. And makes the system less reliable. High-gain multilinking transformer-based converters can be used to address this issue. They also have more no of switches which lead to the poor efficiency of overall systems. Furthermore; existing stand-alone schemes employ an additional dedicated dc-dc converter to realize MPP operation. As PV power remains unavailable for more than a day; the utilization of MPPT tracker converter becomes very poor [6][7][8].

For eliminating above mentioned limitation and poor efficiency factors PV battery system can use a power converter which works both as MPPT trackers and battery charge controllers. System which make use of such converters presented have the following limitations 1) The presence of resonant elements makes the system sensitive to parameter variation,2) permissible variation in the duty ratio of the switches is limited within a certain range and 3) voltage gain is quite limited. A similar approach has also been reported in [10] and [11] for application in a grid-connected scheme.