A CURRENT SOURCE PWM INVERTER WITH INSTANTANEOUS CURRENT CONTROL CAPABILITY

In this paper, a new approach for the control of a current source PWM inverter is proposed to achieve instantaneous current control capability. The proposed scheme provides instantaneous current response in the ac motor by altering the modulation index of the current source PWM patterns. In order to achieve this task, optimum programmed PWM patterns with selective elimination of lower order harmonics in the motor line currents are employed. Output filter capacitors are provided to bypass the current harmonics in the inverter output and allow for the instantaneous changes in line currents. This method of control provides sinusoidal output voltages and sinusoidal currents in the ac motor. The proposed scheme guarantees fast response characteristics combined with high-performance steady-state behavior. A design procedure for the current source PWM and selection of programmed PWM current patterns for a variable-speed situation is illustrated. Finally, selected results are verified experimentally.