| In recent years, with the extensive use of power electronic equipment, arc equipment andmany other non-linear devices, the voltage and current waveform distortions are caused,resulting in an increasing number of harmonic pollution. The effects of harmonic to powersystem inner including: due to harmonic resonance harmonic emissions are amplified,resulting in the damage of capacitors; make the efficiency of power generation, transmissionand use decreased; insulation aging of power equipment shortens the service life; cause thesystem or equipment misoperation. The effects of harmonics to power system external may bethe deterioration of communication system performance, excessive noise and harmonicsinduced current and voltage. Because of the production of harmonic, the power quality declineday by day. In order to improve the power quality, we need to monitor and analyze harmonic.One of important harmonic harms is harmonic resonance. The capacitors in system cancause local resonance. Resonance in return generates over current to the capacitor. The parallelresonance or series resonance of power system will cause excessive voltage and current,forming local overheating, which make the capacitors local current and voltage amplified, andthe insulation aging accelerated and electrical equipment damaged. Therefore, we need toavoid or reduce the power system harmonic resonance. So we should know the power systemimpedance frequency characteristics and the frequency of harmonic resonance. Further weneed discuss the affected regional of harmonic resonance. To take measures to avoid theharmonic resonance. This is very important to make sure power system operate safely. Theparallel resonance often occurs in the power system, the paper main study issues of powersystem parallel harmonics resonance.The main work of this paper is to study the harmonic power flow algorithm and resonanceovervoltage. Online monitoring system in this paper is based on the industrial computertechnology to design. It includes client, presentation layer, processing layer, the informationlayer. The processing layer consists of harmonic emission level calculation, harmonic powerflow calculation, harmonic source location, network loss calculation algorithm. The advantagesof the system mainly includes: between local on-line monitoring devices are independent ofeach other, so increasing and reduction of arbitrary unit does not affect the normal operation of the whole system; multifunctional monitoring terminal; data recording completely; datacollected by GPS synchronous stations, can get accurate harmonic power flow and display theresults, therefore, can detect resonance more accurately. At the same time it can monitor theentire harmonic power flow level of substation network timely, so we can carry on thereal-time monitor to the resonant point. The analysis method that uses the modal andharmonic power flow calculation to verify the accuracy of harmonic distribution, can providepowerful guarantee for a "double insurance" to the harmonic resonance condition analysisresults. |
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