Single Phase to Three Phase Converter

Abstract

The paper addressing the problem of increasing the energy efficiency indices and the lifetime of the mono/ three phase inverters powered from the single phase AC grid. The actuality of this problem regarding the efficiency of the use of electricity is determined by the fact that at present most of the receivers in the residential sector are of single-phase type (washing machines, air conditioners, electric pumps, refrigerators, kitchen equipment, etc As a solution to increase the efficiency of the use of electricity in the consumption phase, the use of three-phase asynchronous motors is examined, which have higher energy performance indices compared to single-phase asynchronous motors. For the control of three-phase motors when supplying them from the single-phase network, a new three-phase inverter control algorithm is proposed, which has been called frequency-pulse-width-modulation (FPWM). The simultaneous modulation of the frequency and the width of the control impulses leads to the decrease of approximately 25% of the number of the control impulses of the transistors of the three-phase inverter. This ensures quality indices of electricity supplied to the three-phase asynchronous motor and minimal pollution of single-phase grid with the higher current harmonics. The proposed frequency-pulse-width-modulation algorithm excluded the function of intermediate energy storage in the electrolytic type DC filter capacitors, which have a shorter lifetime compared to other components of the voltage inverter. As a filter capacitor of the proposed three-phase inverter, only capacitors with dielectric film are used, which have a much smaller capacity value compared to the previously used electrolytic capacitors. The substitution of the electrolytic capacitors was possible because in the proposed inverter the dielectric film capacitors filter switching harmonics of the transistors.