Second Harmonic Current Suppressing Method Based on Negative-Order Capacitor lot of undesired low-order harmonics when converters are em- ployed, especially the second harmonic current (SHC). To address the issue, this article proposes a method based on fractional-order capacitor (FOC) to suppress the SHC.
In the proposed method, only two 150-μF capacitors, one 120-μH inductor, and two switches are employed to suppress the SHC at dc bus. The secondary harmonic amplitude is reduced to 2.04% of dc component, while the 13th-order harmonic is increased to 4.10%. IV. CONCLUSION
The low frequency harmonic current and its resonance suppression characteristics are analyzed based on the multi-reference vector control strategy in this paper.
In addition, with the increase of the control factor K, the control strategy is more effective in managing the load harmonic currents, but there is no obvious effect in resisting the background harmonic voltage of the grid, and it can also cause system instability in the low frequency resonance suppressor.
In addition, the NOC circuit can adjust zero impedance to specific harmonics; so it can be expanded to suppress harmonic current at other frequencies in the system. The simulation and experimental results are presented to validate the feasibility of the proposed method.
It can be seen from Fig. 6 (d), when low frequency harmonic current is controlled, η 4 is almost a plane close to zero, indicating that the suppression capability of 100 Hz harmonic current by the LFRS is not affected by the impedance fluctuations of the power grid, and the control parameter K has a wide range of values.