APPARATUS FOR INCREASING THE VOLTAGE UTILIZATION OF THREE-PHASE PWM RECTIFIER SYSTEMS WITH CONNECTION BETWEEN OUTPUT CENTER POINT AND ARTIFICIAL MAINS STAR POINT

摘要

An apparatus for increasing the voltage utilization of a three phase PWM rectifier system (1) with a star connection of filter capacitors connected to the mains phase terminals, star point (5) is connected to the output voltage center point (100). The control of the input currents is done by a current controller (31) in each phase that defines the gate signals for the bridge-leg change over switches (14, 15, 16). The phase current reference value (29) formed by a supervising output voltage controller, is extended according to the invention by adding a phase current reference component that is equal for all three phases. To form this signal, the filter capacitor voltages measured positively against the output voltage center point are added and attenuated by a gain element (36) by a factor of 3. A zero-voltage reference value function generator creates a third harmonic of the mains voltages with defined amplitude and phase position according to the mains voltage.