On-line Estimation and Control of Voltage Profile along 6.6kV Feeders

This paper presents a new scheme for the estimation of the voltage profile along distribution feeders for the on-line voltage control. Among the control devices equipped in distribution systems, transformers with taps and static VAr compensators with small capacity are selected for the proposed voltage regulation. A simple scheme has been proposed for the estimation of the voltage profile along feeders. In the proposed scheme, the measurement of the voltages and the currents are required only at the heads of feeders. Based on the nodal equations of the distribution feeders, the voltages are estimated at all the nodes along feeders from the measured voltages and currents at the heads of feeders. Whenever the voltage profile violates the voltage restriction, the control strategy is determined to keep the voltage levels along the feeders within the pre-specified range through the modification of the transformer tap positions and/or the reactive power compensation on the static VAr compensators. To demonstrate the efficiency of the proposed scheme, several simulations have been performed for a 6.6 kV distribution feeder. The estimation of the voltage levels has been performed based on the nodal equation of the model system under a simple assumption that all the loads have the same power factor. The comparisons between the estimated and the exact levels indicate the efficiency of the proposed estimation scheme with extremely small estimation errors. In addition, after activating voltage control actions, namely after modifying the transformer tap positions and/or the compensated reactive power at the site of the static VAr compensator, the improvement of the voltage profile has been also predicted quite precisely along the feeder based on the proposed scheme. The on-line application is readily available because the required computation is quite small