Impact of charging of backup batteries by residential consumers on the low voltage distribution network
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Battery-charging units are appreciably being used in residential application as power back-up in the face of power shortages. The study investigated the effects of backup battery-charging units on the low voltage distribution network. The investigation focused on examining the supply voltage drop, total harmonic distortions (THD) and dc component produced at the point of common coupling by backup battery-charging using Simulink. Fourteen performance parameters which determined the quality of low voltage distribution network were reviewed. Eight of the performance parameters (namely supply voltage, supply current, harmonics, voltage imbalance, notches, direct current mains signaling interference and noise) were found to be affected by backup battery-charging units. Three out of 8 performance parameters affected by backup battery-charging units can be investigated using Simulink. Performance parameters investigated are the voltage drop, harmonics and dc component. Supply voltage drop of 0.13 to 2.48%, supply voltage THD of 0.02 to 0.17%, current THD of 0.41 to 0.61%, dc voltage component of 0.0000318 to 0.0008757V and dc current component of 0.00002763 to 0.00017417A were obtained by simulating up to 10 backup battery-charging units. Additionally, supply voltage drop of 2.74 to 12.93%, supply voltage THD of 0.18 to 0.83%, current THD of 0.63 to 3.65%, voltage dc component of 0.0009713 to 0.0087291V and current dc component of 0.00019423 to 0.00084623A were obtained by extrapolating 11 to 50 backup battery-charging units. By extrapolation, the maximum number of backup battery-charging units required to produce maximum permissible supply voltage drop of 10% and THD of 5% were found as being 39 for supply voltage drop, 57 for current THD and 300 for voltage THD. The voltage drop above 10% and the THD above 5% require mitigation to maintain the values at the acceptable limit according to Institute of Electrical and Electronics Engineers (IEEE) 519 standard. Overall, the least number of backup battery-charging units found to violate the standard was considered as the maximum number of backup battery-charging units which can be connected simultaneously. Therefore, 39 backup battery-charging units was considered as the maximum number of backup battery-charging units to be connected on the low voltage distribution network where neither supply voltage drop nor THD limits would be violated. Keywords: Backup battery-charging unit, distribution, network, supply voltage/current, total harmonic distortion.
The University of Zambia
SubjectBackup battery--Charging unit
Electric power distribution
- Engineering