Study on harmonic limit correction and harmonic suppression measures of electrified railway traction system under weak current network connection

During the operation of electrified railway, electric locomotive will inject harmonics into the power grid and degrade the power quality. For the weak current network system powered by long-distance transmission lines, due to the harmonic amplification characteristics of long-distance transmission lines, the injected harmonics at the line traction station side may be within the national standard limit due to harmonic amplification, but the output harmonics at the line grid side exceed the standard. Therefore, the harmonic amplification mechanism of long transmission line is studied, and the existing harmonic national standard limit is corrected, so that under the condition of harmonic amplification, each harmonic inj ected into the power grid by the traction power supply system still meets the requirements of the existing national standard. Simulation and practical engineering cases show that after the corrected harmonic limit is used to restrict the harmonic current injected into the public line by the electric locomotive, the output harmonic current at the power grid side of the public line is still within the allowable range of the existing national standard.