Adaptive filtering for selective elimination of higher harmonics from line currents of a voltage source converter

The methods for adaptive noise canceling have been well developed and researched in digital signal processing. The task is typically accomplished by generating a reference signal with frequency that should be eliminated from the primary input signal. The reference is filtered to match the interfering sinusoid in primary input. The weights of the adaptive filter are adjusted to totally eliminate the component with undesired frequency from the primary input, creating a tunable notch filter with an infinite null at selected frequency. The above concept was used as a basis for the development of an adaptive selective harmonic canceling (ASHC) algorithm. With ASHC added to the "regular" control of the VSC, the whole VSC becomes an active adaptive infinite null power notch filter at selected frequencies. The algorithm was used for elimination of higher harmonics 5, 7, 11, 13, 17, 19 from the input utility currents.