Input Harmonic Estimation and Control Methods in Active Rectifiers

Active rectifiers using pulsewidth-modulation voltage-source converters are popular choices for adjustable-speed drives to provide high input power quality. However, input current harmonics are often generated as a result of input voltage source disturbances. Since the frequencies of the fifth-, seventh-, and higher-order harmonics can easily exceed the current controller bandwidth in high-power applications, the elimination of these harmonic disturbances imposes difficult control challenges. Cost-effective observer-based harmonic estimation and mitigation methods are introduced in this paper that compensate delay effects caused by the digital signal processing. These delays can significantly limit the current controller bandwidth if not compensated. Analytical, simulation, and experimental results are developed to illustrate the effectiveness of the new harmonic estimation and control techniques.