Development Of A New Type Of Zero Sequence Filters In Distribution Network

Zero sequence harmonic current’s appearance in the low-voltage distribution network, will cause the system neutral line’s overload, resulting a hidden trouble as line broken, unbalanced load and nonlinear load is the culprit of this series of problems. Due to the zero sequence harmonic currents in electric power line, it will produce strong skin effect, reduces the power supply efficiency of system; Heat, noise generation and other problems will appear because of the existence of zero sequence harmonic currents in transformers. So, zero sequence harmonic currents will influence and threat power system’s safe, stable and reliable operation. Absorption, restrain and management of zero sequence harmonic currents is imminent.This paper researches the characteristics of the zero sequence harmonic currents in the power system, investigates detailed analysis of the typical user’s power arrangement and harmonic condition and compares the main methods in harmonic current governance and inhibition.Detailed introduction and analysis of existing power filters is given in this paper, a new way of zero sequence filter without capacitors is also proposed. It reserves several advantages of passive power filters, and overcomes a series of problems of it, such as sensitive to parameters’ change in the grid, only effective to the specific frequency harmonics, the threat of mismatch, and so on; Provides a low resistance channel to fundamental zero-sequence harmonic currents, at the same time, it overcomes some defects of active power filters, and play an important role in balancing the stability of system operation.