Analysis and control of Buck-Boost Chopper type AC voltage regulator

Traditional AC voltage regulator used servo-motor position regulation or thyristor phased controlled method which had low dynamic response speed or large amount of harmonic components. However, these drawbacks can be overcome by using Pusle Width Modulation chopper techniques in AC voltage regulation. Buck-Boost Chopper type AC voltage regulator, derived from the DC chopper modulated method, is a kind of direct AC-AC voltage converter and has many advantages: such as fast response speed, low harmonics and high power factor. It adopts high switching frequency AC chopper techniques and can do wide range stepless AC voltage regulation. The steady-state equivalent circuit of the Buck-Boost chopper type AC voltage regulator, as well as the theoretical analysis method of the input power factor and the output voltage is presented in this paper. In addition, in order to solve the problems caused by the sags or swells of the input voltage, the output voltage controller is designed. The proposed voltage controller uses output peak voltage as feedback signal and adopts PI control strategy to regulate the output voltage. Digital simulation results coincide with the theoretical analysis and show that the Buck-Boost chopper type voltage regulator has a unit input power factor and that the designed voltage controller can stabilize the output voltage with fast dynamic speed when input voltage fluctuations occur.