Analysis of a Delay Compensated Deadbeat Current Controller for Inverters

ABSTRACT: Deadbeat control is one of the most attractive control techniques, as it exhibits very fast dynamic response. Deadbeat control has been widely applied in power electronics for Pulse Width Modulation (PWM) inverter. This control technique places all the system closed-loop poles at the origin of the z-plane. Hence, it can achieve fast dynamic response with low Total Harmonic Distortion (THD), even under nonlinear loads. In existing deadbeat control techniques for single-phase UPS inverters, the pulse width of the inverter output voltage is limited by the computation time of the controlling processor. With the development of power semiconductor devices that can switch at very high speeds, feedback control techniques have been considered for inverters in UPS systems. Classical open-loop techniques of obtaining sinusoidal output voltages are incapable of providing a satisfactory response with nonlinear or fast-changing loads. In this thesis current control of a single phase PWM inverter connected to the grid is studied. The main objectives of the control are that the current has minimum harmonic distortion and is in phase with the grid voltage. The control system should have fast dynamic response when distortion occurs and should be robust against drift in the system parameters. In this thesis delay problem of a dead beat current controller for inverter is investigated by applying the z-transform technique. A Simulink model is developed to investigate the performance of a control strategy proposed in the literature [1]. Keywords: PWM, THD, UPS, Deadbeat control. ……………………………………………………………………………………………………………………………………………………………………………………………………………………