Abstract: A dynamic series voltage compensator (10) for compensating voltage dips in an ac electric power system is described. The compensator (10) has a controller (11) coupled to control a respective series injection inverter (12a, 12b, 12c). The controller (11) monitors a supply voltage with/on a respective phase. Inputs from monitoring the supply voltage are processed by the controller (11) to generate control signals. These control signals are based on comparing voltage magnitude of a present voltage cycle period with voltage magnitude of a preceding voltage cycle period of the supply voltage. When difference between the present and the preceding voltage cycle periods exceeds a predetermined value for a corresponding time period, and inverter control signal is provided to the respective series injection inverter (12a, 12b, 12c) to thereby provide a compensation voltage. The compensation voltage is injected directly to the respective conductor.