Novel Scheme for a Three-Phase Sinusoidal Reference Generator for Unbalance Input Operation

Three-phase PWM systems such as DVR, voltage regulators, active power filters and UPS rely on the quality of their reference signals to provide a good performance regarding their output signals. Classic approaches for this issue use reference frame transformation that is very sensitive to input voltage unbalance. In this paper, a new approach to build a reference signal generator is presented. It is based upon the monitoring of the input voltage status via zero crossing slope to control three single-phase independent digital signal synthesizers. The proposed generator shows small THD variations over a wide variation of the input voltage, ranging from 50 to 100% of their nominal value in either one, two or all voltages. The phase balance of the signals is kept within plusmn 1deg. In both parameters, the proposed generator greatly overcomes the variations of a classic DQ generator, making it an attractive alternative for PWM controls.