Small-signal averaged model and simple control of a high-power-factor three-phase/switch/level fixed-frequency PWM rectifier for high-power telecommunications

This paper presents a new small-signal model of a three-phase three-switch three-level boost-type rectifier operating with a fixed switching frequency. The proposed model is obtained by linearizing the (d,q)-averaged representation of the converter in the neighborhood of a desired unity-power-factor operating point. The linearized model is expressed both in the time domain, using the state representation, and the frequency domain by computing the corresponding transfer functions. These latter are then used into the design of linear-control-based regulators in order to ensure the convergence and stability of the system around the desired set point. The control system is implemented numerically using Matlab/Simulink, and simulation experiments are carried out in order to test and verify its tracking and regulation performance, as well as its robustness towards load or mains source disturbance.