Inverter Asynchronous Electric Drive System with PAM and PWM Control

The paper considers the structure of a three-phase two-stage frequency converter with voltage control at the input of an inverter for frequency asynchronous electric drive systems. The disadvantages of this structure are shown when using traditional input rectifier circuits, which are designed to operate at a constant level of rectified voltage. Two innovative circuits of the controlled rectifiers are proposed, each of which operates on the principle of the Cuk converter. The innovative rectifiers with adjustable voltage for PAM (pulse amplitude modulation) control are the step-up-step-down, have high electromagnetic compatibility at the input and output and reduce the loss of active power in the rectifier-inverter frequency converter. Waveforms of the input and output voltages and currents, the control and load characteristics of the proposed circuits and the dependence of their input power factors on the degree of regulation of the rectified voltage are given. Waveforms of the output controlled phase voltage and current of the inverter are also shown for various control parameters. Some power losses figures of the proposed frequency converter with circuits of the input innovative rectifier are given.