Analysis of voltage unbalance due to rooftop PV in low voltage residential distribution system

Abstract

Due to crisis shorta g e of electric p ower, g lobal warmin g issues and p ressure on chan g in g ener g y p roduction from coal-fired p ower to renewable ener g y, the solar ener g y is becomin g increasin g ly attractive. In Thailand, the g overnment has a pp roved ener g y de p artment p lan to increase its renewable ener g y tar g et, which will include three and sin g le p hase PV installations. This p a p er p resents a study on volta g e unbalance due to the increased roofto p PV installations on low-volta g e residential distribution system. The sin g lep hase roofto p PV model is develo p ed by Matlab/Simulink and is used in the study for analyzin g the volta g e unbalance under different installation ratin g s and locations. The obtainin g results can be used as g uidelines for electric distribution utilities to determine the maximum PVs installations in low-volta g e residential distribution systems without affectin g the p ower quality issues.Keywords-Low-volta g e residential distribution system;Sin g lep hase roofto p PV; Volta g e unbalance Fig.5. The voltage profiles of each phase when the rooftop PVs are installed.The following study cases are carried out:Case 1: The power demand of the load is at light load condition and % PV penetration is varied from 0 to 100% of the feeder capacity .The rooftop PV's installation is at only the phase A along of the loads of customers.

Probabilistic model for residential load profiles and power quality improvement

“…One of the most common PQ problems is Voltage Unbalance, raised due to rooftop PV systems in low voltage residential distribution system. A single phase rooftop PV model developed by MATLAB is used in the study for analyzing voltage unbalance under different installation ratings and location [3].…”

“…When the rooftop PV is operated in a low voltage distribution system, a voltage profile will depend on the power output generated by the rooftop PV and the line impedance. Fig.1 is used to evaluate the effect of rooftop PV on voltage profiles [3].…”

“…In Fig.1, V S is the source bus voltage, V L is the load bus voltage and Z = R + jX is line impedance [3]. The load bus voltage can be derived by (1).…”

“…Doing all the analysis, the final equations of current injected into the bus is calculated by (5) [3].…”

“…These are semiconductor devices, which are capable of converting incident solar energy into dc current, with efficiencies varying from 3% to 31%, depending on the technology, temperature, design and the material of the solar cell [2].Reverse power flow is a major problem affecting power quality of the voltage of electric power distribution when a growing number of large installations is large. So, we focussed on analysis of voltage unbalance at the planning stage [3].…”