Improvement of the Power Quality Indicators in Functioning of Nonlinear Loads Using LabVIEW

摘要

Power electronic converters represent one of the most important components that cause harmonic distortion in the power distribution. Distortion regime produces negative effects in functioning of other electric energy consumers. Distorting consumers absorb from the power system active and reactive powers on the 1st order component more then necessity, the difference being returned to the power supply system as distorted power. In linear power supply system the power loss are determined by the active and reactive powers circulation produced by system generators and also by the distorting powers circulation produced by the nonlinear loads. For compensating this negative impact, there must be connected power conditioning devices at the interface with the power supply system in order to obtain improvements in power quality indicators. This paper describes the LabVIEW implementation for a three phase active filter command system. The main purpose of this active filter is compensation of the current harmonics in power supply system generated by an electro thermal installation with electromagnetic induction. Filtering system acquires distorted current and voltage signals from the power supply system using a signal acquisition interface and a data acquisition board connected to a computer. The main function of the interface is to realize the compatibility between voltage levels of the acquired signals and also the data acquisition board requirements. Another condition that must be accomplished is the galvanic isolation between power supply system and data acquisition board. Using an application designed in LabVIEW, the ddistorted signals are acquired and saved into text documents in order to be processed. The application also realizes the pulse width modulation operation of the distorted signals. The resulting pulses command the active filter switching devices using the pin outs of same data acquisition board. The paper also presents the variation of the generated command pulses during the functioning of the electro thermal installation.