A generalized voltage compensation strategy for mitigating the impacts of voltage sags/swells

Dynamic restoration of load voltage achieved through the application of voltage-injection technique is considered. The injected voltage is generated from a voltage-source-inverter-based series compensator. It is shown that during a voltage sag, the restoration process almost inevitably requires the injection of energy from the compensator to the external system. Conversely, a voltage swell event could cause the compensator to absorb energy from the external system which would then result in a rise in the dc-link voltage of the inverter. By permitting phase adjustment in the injected voltage, a generalized compensation method is proposed. The new voltage injection technique allows the magnitude of the positive phase-sequence component of the compensated load voltage to be restored to its pre-sag/swell level. It also exercises simultaneous control on the dc-link voltage. The efficacy of the proposed technique is illustrated by numerical examples.