Construction of a high efficient and low-priced low voltage inverter module for use of photovoltaic arrays integrated into structural components

This report describes the design and construction of a high efficiency and low - priced, low voltage inverter module for general use of photovoltaic arrays integrated into structural components. In the report a specification of software and hardware elements is performed, this specification is the basis for the design of the actual sub units. The project has resulted in design and construction of a prototype unit, placed on an aluminum base plate measuring 30cm x 40 cm. The prototype is tested in the laboratory using a stabilized DC voltage source as power source. The prototype is connected to the 230V grid and pictures of the voltage and current waveforms have been recorded. The overall efficiency etc. of the prototype is documented by measurements shown in the appendixes of this report. The measurements shows that the efficiency of the H bridge is higher than 96% in best case (about 20W), on both sides of this working point the efficiency decreases (95% at 10W, 93,1 % at 120W). The efficiency of the H bridge can be improved by optimizing the PCB layout and filter elements. From an economical and system modularity point of view it was decided to use a small transformer for each inverter module. The purchased standard transformer showed up to have a poor efficiency (maximum 89%). This means that the overall efficiency for the inverter module is quite low, between 41% (at 20 W) and 77,2% (at 120W). It is possible to improve the overall efficiency considerably by using a special design transformer. The functionality of the software is documented by the ability of grid connecting the inverter module and by the subsequent measurements