Development of a stand alone inverter efficiency test setup

Murdoch University's School of Engineering and Information Technology has a plan to develop the stand-alone inverter efficiency test setup for the laboratory exercise of the unit ENG421 Renewable Energy Systems Engineering. The laboratory exercise, which identified Inverters for Stand-Alone PV Systems, aims at helping students gain an understanding of the principles of operation, efficiencies and output current and voltage wave shapes at various loadings of two inverter types used in stand-alone PV systems. This report focuses on the development of the previous setup of ENG421 laboratory at Building 190 on the Murdoch University Campus. The aim of the development is to work out some issues with the existing system including an ageing battery bank which is expensive to replace and the replacement of the inverters that they are expected to meet Australian Standards: AS5603 Stand-alone Inverters - Performance requirements and AS4763:2011 Safety of Portable Inverters. Moreover, the aim is to determine the uncertainty in measurement by undertaking the uncertainty analysis of the efficiency test results. The stand-alone inverter efficiency test setup consists of power source, digital power analyzer, hall effect sensor circuit to supply isolated signals for viewing AC voltage and current, differential probe, oscilloscope, various load banks and two types of stand-alone inverters (sine wave inverter and modified square wave inverter) for comparing efficiency test results and output waveforms. The design work and implementation of the development is complete now. The Agilent DC power supply (0-60V, 0-11A, 6.6kW) is used to replace the battery bank due to its good ability to simulate the batteries and high-quality performance during long period. Moreover, the Protek multimeters of previous setup are replaced by YOKOGAWA WT2030 digital power meter to achieve more accurate measurements. Two stand-alone inverters are selected and used in the new setup so far, they are Selectronic Sine Wave Inverter 350VA and Suntron Power Inverter 350VA (modified square wave inverter). However, all of these inverters were manufactured before 2011. To meet the requirement of AS4763:2011 Safety of Portable Inverters, a new stand-alone inverter manufactured after 2011 should be purchased for the setup in the future work. In this project, several specific tasks were also carried out including the review of the previous work, redesign and implementation of the test setup, documentation and analysis of the stand-alone inverter efficiency test, and the determination of the uncertainty in measurement. Also, the background information relating to the stand-alone inverter is provided and discussed. The maximum efficiency of Selectronic 350VA sine wave inverter is 88.8% when there is 104 watts loading. The maximum conversion efficiency of Suntron 350VA modified square wave inverter is higher which is 92.9% when there is approximately 150 watts loading. The final expanded uncertainty for measurement of the peak efficiency point of Suntron 350VA modified square wave inverter is 0.072%. The work is completed now and ready to be used in the laboratory exercise of unit ENG421 Renewable Energy Systems Engineering. But the test setup requires new stand-alone inverters and improvement of measuring equipment for future work. The ultimate purpose of the test setup is to provide future students a safe, informative and reasonable experiment exercise