Alexandru Băloi

By Alexandru Băloi and Adrian Pană

The importance of the subject is given by the fact that harmonics are making their presence felt in electrical distribution networks, and the cheapest and most widespread solution for power factor correction is the capacitor banks. This chapter proves that the harmonic impedance is an efficient tool for assessing the state of distribution networks containing harmonics. The unfavorable operating conditions are anticipated based on the network harmonic impedance values, and the means of intervention are selected. Harmonic impedance monitoring and using it in expert systems for operating condition optimization will increase in the future. Power factor correction by shunt capacitor switching in electrical networks containing harmonics can lead to harmonics amplifications by harmonic voltage increasing and capacitors thermal overstressing by great values of the currents flowing through them. This chapter proposes a method for practical determination of harmonic impedance. Based on its values, a quick method is developed to anticipate the harmonic voltages and current amplifications that can occur when a shunt capacitor is installed for power factor correction. Amplification factors are calculated depending on the equivalent harmonic impedance of the network seen in the compensation bus. A distribution network containing harmonics is modeled using MatLab Simulink, and harmonic impedance is determined by simulation in different operating conditions. Using the values of the harmonic impedance and the capacitive reactance of the capacitor bank that is connected for power factor correction, the amplification of the harmonic voltages and currents is estimated by calculus. The results obtained by calculus are then compared with the values obtained by simulation after the connection of the capacitor bank to the network. In conclusion, the chapter proves that the network harmonic impedance is a useful tool to estimate the harmonics amplification caused by power factor correction using shunt capacitor banks.

Part of the book: MATLAB

By Alexandru Băloi, Florin Molnar-Matei and Felicia Băloi

This chapter proposes the use of LabVIEW in a very common application both in the field of power engineering technical education and in the industrial environment. It is about compensating the reactive power with the aim of increasing the power factor. Capacitive reactive power compensators for this purpose are provided with compensation steps. The connection and disconnection of these steps according to the load curve of the consumer and the power factor at which it operates are done by means of programmable controllers. Most capacitive compensators are designed to be connected balanced to the three-phase network, in delta connection. In the situation when the reactive capacitive compensators are designed for both power factor improvement and load balancing, single-phase connection of capacitor steps is needed. The chapter proposes a LabVIEW virtual instrument that, by means of National Instruments equipment, is designed for operating condition monitoring and single-phase command. The virtual instrument was tested in the laboratory on a model consisting of a RL consumer with step-adjustable inductive component and a step-adjustable capacitive compensator. The National Instruments hardware equipment used, the modeled consumer, and its related capacitive compensator are presented. Special attention, with details of realization, is given to the virtual instrument architecture.

Part of the book: LabVIEW