The Feedback Adaptive Control Of PWM Rectifier Based On Inverter Output

The feedback adaptive control of PWM rectifier based on inverter output has been widely used in AC driver system. In AC-DC-AC voltage frequency speed regulating system, dual PWM rectifier and inverter adopt PWM technology to control rectifying bridge with sine PWM, making the input current nearly approach sine wave and phase controllable. So the input current only contain high order harmonics related with switching frequency. These high order harmonics can be easily filtered out while the power factor can be close to 1, reducing hazards to the power grid .This paper has analyzed the working principle of Voltage Source Rectifier (VSR) under steady-state condition and come to the conclusion that the key is the control of the AC-side current. Based on the mathematical model of the PWM rectifier under three phase steady coordinate system, the mathematical model under reference d-q is deduced by introducing the idea of rotating reference coordinate. After analyzing and comparing direct and indirect current control methods of three-phase VSR, the latter has been employed as the main control scheme by designing a double close loop control system based on current and voltage. As some parts of the system are non-linear that the relevant parameters are not easily measured, the traditional PI regulator can not regulate the system more precisely, leading to system instable in some cases. To make a more stable and better control effect, it should be improved by using Neural Network Control to get a feedback adaptive control system of PWM rectifier in order to achieve better results.Finally on the basis of theoretic analysis, two diode voltage source type AC-DC-AC rectifiers has been reconstructed to do the experiment. The test waveforms and analysis results show that the design improved the accuracy and effectiveness of the control system.