Electric power quality control system and method for metro power supply system

The invention provides an electric power quality control system and method for a metro power supply system. The electric power quality control system comprises a collection device, an active filter and a monitoring device, wherein the collection device is used for collecting voltages and currents of a high-voltage side and a low-voltage side; the active filter is used for calculating a harmonic current compensation value and a reactive current compensation value according to the collected voltages and currents; the harmonic current compensation value is equal to an opposite number of the sum of a harmonic current component at the high-voltage side and the harmonic current component at the low-voltage side; the reactive current compensation value is equal to the opposite number of the sum of a reactive current component at the high-voltage side and the reactive current component at the low-voltage side; and the monitoring device is used for determining the working mode of the active filter according to the harmonic current compensation value, the reactive current compensation value and the rated capacity of the active filter, and is also used for generating a current compensation instruction according to the working mode, the harmonic current compensation value and the reactive current value of the active filter and transmitting the current compensation instruction to the active filter.