Voltage regulation strategy of AC distribution network based on distributed PV grid-connected inverter

摘要

The distribution network connected with photovoltaic (PV) power generation may show high voltage under strong light and low voltage under weak light. The influence of distributed PV generation on the grid voltage profile is analysed first, and then, the sensitivity of the grid voltage to the PV inverter output power is deduced. Aiming at overhead line distribution network, the local voltage regulation strategy based on the power control of the grid-connected PV inverter is proposed. The PV inverter works under the maximum power point tracking (MPPT) mode with unity power factor when the grid voltage is at the normal level. However, when the voltage is higher than its upper limit, the grid-connected PV inverter will be co-ordinately controlled to output limited active power and necessary reactive power to restrain the line voltage. Also, when the voltage is below than the lower limit, only the reactive power of the grid-connected PV inverter was controlled to sustain the line voltage, and the reactive power is no more than the residual capacity of the grid-connected PV inverter operated in the MPPT mode. Simulation and results show that the voltage quality of the distribution network with PV generation is improved by using the voltage regulation strategy presented in this study.