UPS Overload Protection and Current Control Using Discrete-time Sliding Mode Technique

A. Keyhani and M.N. Marwali (USA)


Current control, discrete time systems, harmonic distortion, inverters, overcurrent protection, uninterruptible power systems, variable structure systems, voltage control.


Overload protection is an important issue for UPS systems. A dual loop control structure is proposed for a three phase UPS systems to achieve overload protection as well as output voltage tracking under load disturbance, unbalanced load, and nonlinear load conditions. A discrete-time sliding mode controller is used to control the current loop, while the voltage loop is controlled by a robust servomechanism controller for the elimination of total harmonic distortion in the output voltage. The discrete-time sliding mode current controller exhibits fast tracking and low chattering. The robust servomechanism controller for the voltage loop guarantees the overall stability and robustness. Simulation and experimental results demonstrate the effectiveness of the proposed control scheme.

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