Voltage/var control of unbalanced distribution systems equipped with distributed single-phase PV generators

摘要

This paper proposes a solution to voltage rise and/or sag in single-phase unbalanced distribution systems using photovoltaic (PV) arrays with reactive power capability. The PV is controlled to inject maximum power using Maximum Power Point Tracker (MPPT) to supply local loads when the solar power is available. The reactive power capability of the PV inverters regulates the bus voltages in transient conditions due to irradiance variations or load changes to be within standard limits. A combined control algorithm of dq-current control with hysteresis current control (HCC) capability regulates the inverter current at different power factors according to the voltage value. The inverter reactive power supplied/consumed to/from the grid is calculated using fuzzy logic control (FLC) function. The control algorithm dq/FLC/HCC is tested with a 10-node unbalanced distribution system under various case-studies of solar irradiance variations and step-change of system loads. The obtained results clearly justify the proposed control in maintaining the bus voltages within standard limits in both transient and steady-state conditions.