Research On Current-Source PWM Rectifier And Its Nonlinear Control Strategies

With the development of power electronics devices, a lot of power electronics equipments have been widely used in different industry. However, most of these equipments need rectifiers, the traditional phase control rectifiers and diode rectifiers have disadvantages such as low line power factor, heavy line current distortion. The PWM rectifier is a"green"power electronics equipment since it offers sinusoidal input currents, unity or adjustable power factor, reversal of power flow. The PWM rectifiers can be classified into voltage-source rectifiers (VSR) and current-source rectifiers (CSR). CSR is more attractive then VSR in some high or medium power applications due to their advantages such as controlling the output current directly, fast dynamic response, high capacity of limiting the short-circuit current.This dissertation studies the CSR and its control strategies under balanced supply voltge, unbalanced operation conditions and parallel operation of multi-modulars, the main contributions include the following aspects.1. Assuming that the supply voltage is balanced, for dealing with the nonlinearity and the state variable coupling of the CSR mathematical model, the dc current nonlinear control and ac current nonlinear control are proposed, which achieve decoupling, independent control of direct and quadrature line current components and linear dynamic response. For the dc current nonlinear control scheme, the dc current controller is parallel to the quadrature line current controller, and a faster dc current transient response is obtained. For the ac current nonlinear control scheme, the dc current controller is cascade to the direct line current controller, which is convenient to design the dc controller and the ac controller independently.2. Under unbalanced operation conditions, a new control method based instantenous active power regulation is proposed, which can not only eliminate the input output harmonics of the CSR but also obtain controllable power factor and sinusoidal line currents. In addition, a ac current controller based sliding-mode control in stationary frames is designed, which simplifis the controller structure and tracking the line current accurately.3. A novel circulating current model of multi-modular CSR is established. For each parallel three phase CSR modular, a new controller structure of the CSR dc side is proposed, which includes a total dc current controller and two current equalization controllers. The proposed structure assures that currents flowing through the upper and lower bridges of each modular are equal and control of the each CSR modular is indenpent since only one signal is shared among modulars。4. A experiment system of three phase CSR is set up and basic experiments are carried on.