Development Of Single Phase Transformerless Inverter

Ahmad Fauzi, Nur Syamimi (2018) Development Of Single Phase Transformerless Inverter. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

The efficiency of the inverter can be improved when there is no transformer used in photovoltaic (PV) single-phase inverter system. One of the main problems in single-phase photovoltaic (PV) inverter is to control leakage current appearing between parasitic capacitor and ground. The main problem of ground leakage current is, its poses an electrical hazard to anyone touching the photovoltaic (PV) array’s surface. As required in VDE-0126-1-1 German standard, the ground leakage current must be below 300mArms for safety issues. To reduce the ground leakage current, the single-phase transformerless inverter is analyzed, verified and compared in this report. There are four factor that effect the ground leakage current which is the switching technique, parasitic capacitance, filter design and topology used. The effective way to control the ground leakage current is by keeping the common-mode voltage constant. H-bridge inverter topology was used to investigate the suitable switching technique, which is bipolar SPWM and unipolar SPWM is used. In order to analyze the effect of filter design to the bipolar H-bride transformerless inverter, the LC filter using one inductor and LC filter split inductor with same value is investigate. Filter design using LC filter split inductor with same value having a low leakage current. Therefore, the effect filter impedance matching was analyzed. In addition, the effect of the parasitic capacitance on the bipolar H-bridge transformerless inverter is studied. After the three factors have been analyzed, a switching frequency of single-phase transformerless inverter using bipolar SPWM is analyzed in terms of ground leakage current. Appearing leakage current is causes the safety problem and increased system losses.

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