Technical Research On Harmonic Mitigation In Marine Die- Sel-electric Propulsion System

The large use of nonlinear electrical components in marine diesel-electric propulsion application produces significant harmonics in marine electric power network. Among different sorts of nonlinear loads in marine electric power net-work, the growing capacity of frequency convertors are becoming one of the main sources of harmonics.As marine electric power network has limited capacity, power quality is re-quired at high standard to ensure good operation of all marine equipment due to the of the network. China Classification Societies make rules on percentage of total harmonic distortion less than 10% in marine electric power network.The paper describes the main reasons of harmonics arise in the marine elec-tric power systems and the harmful consequence. From the point-view of reduc-ing harmonics in the harmonic sources, the analysis is made on rectification technologies and harmonic mitigation effects in marine diesel-electric propul-sion system. Analyzing the theories of 6-pulse,12-pulse,24-pulse rectifier technology and PWM rectifier technology, I design, calculate, simulate and an-alyze several diesel-electric propulsion power systems for XX cruise liner, adopting 12-pulse rectifier,24-pulse rectifier and AFE rectifier with L filter or LCL filter. The AC bus voltage is analyzed for THD) in typical operational con-ditions, getting the harmonic mitigation effects under different rectification plans.Finally, comparing the harmonic mitigation effects, the conclusion is made concerning the performance, dimensions, weight, noise, cost and cooling meth-od of different harmonic mitigation technologies. The multi-pulse rectifier pro-gram can meet the rules for harmonic mitigation, but the harmonic mitigation effect is influenced by the operating status. The AFE rectifier with LCL filter program can well mitigate harmonics and the harmonic mitigation effect isn’t influenced by the operating status. The AFE rectifier with LCL filter program is the ideal program for harmonic mitigation. AFE drive is supposed to be the most effective way to reduce the harmonic pollution in marine power system.