dc link voltage control of UPQC for better dynamic performance

The dc link voltage of the Unified Power Quality Conditioner (UPQC) can significantly deviate from its reference during a transient event, caused by load connection/disconnection or/and supply side voltage sag/swell, though in the steady state the average dc link voltage is maintained at a certain preset level. During such transients, due to considerable dc link voltage deviation, the magnitude of the series injected voltage cannot be constant and this has an effect on the load voltage magnitude, which fluctuates. An improved sinusoidal pulse width modulation (PWM) voltage controller for the series compensator is proposed which adjusts continuously the amplitude modulation ratio in response to the dc link voltage deviations. Also, an adaptive dc link voltage controller is proposed which limits the dc link voltage deviation during transients and assures a negligible steady-state error. The effectiveness of the proposed control schemes is demonstrated through simulations.

► We have proposed an adaptive dc link voltage controller for UPQC.
► During transients or load change this controller limits dc link voltage deviations.
► Simulation results show satisfactory performance.