Fuzzy-supervisory control of a hybrid system to improve contractual grid support with fuzzy proportional-derivative and integral control for power quality improvement

This paper investigates on an additional active power compensation of a microgrid to a weak grid using fuzzy-supervisory control. This reduces the economic penalty of microgrid for going over-contract with the grid in terms of power demand. The objectives of this work are (a) to maximise grid support during periods of over-contract, (b) to minimise distortions and increase dynamic stability of dc link voltage and (c) to improve the total harmonic distortion (THD) of the dispatched power. The microgrid comprises of a wind energy conversion system (WECS) and Li-ion battery energy storage system (BESS). During variations in wind speed, power feed into the point of common coupling (PCC) depends upon deviations in the wind power, dc link voltage, violations in grid contract power and the state of charge (SOC) of the battery. The deviations in these inputs are utilised by the supervisory controller to compute additional power support to the grid, by discharging the battery. Performances of the fuzzy-supervisory controller are compared with a classical-supervisory controller with similar power dispatch parameters. Further, inverter currents are regulated using a fuzzy proportional-derivative and integral (FPD+I) controller to reduce distortions and improve dynamic response of the dispatched power.