CLOSED LOOP PULSE WIDTH MODULATOR INVERTER WITH VOLT-SECONDS FEEDBACK CONTROL

摘要

A closed loop pulse width modulator (PWM) inverter (50) corrects for variations and distortion in the ouput AC voltage (52) waveform caused by non-linearities of the switching devices (S1-S6) or changes in the DC link voltage (3). A signal is generated that is a volt-seconds representation of the voltage error between a voltage command signal (25) and the actual AC output voltage (52) of the PWM inverter (50). The volt-seconds error signal becomes a controlling signal means in the closed loop of the PWM inverter (50) to regulate the output AC voltage (52) of the PWM inverter (50). Another signal that represents changes in the DC link voltage (3) also modifies the voltage command signal (25). The system will compensate for the non-linear behavior of the PWM inverter (50) due to deadtime, minimum on-times and off-times, and DC link voltage (3) variations and voltage drops across the switching devices (S1-S6), and will also allow the operation of the inverter (50) in a linear fashion for the region of operation when one or more of its phases are saturated, i.e., either fully on or fully off.