Research On The Integrated Control Of Dual PWM Converters

Speed control system based on dual PWM converter have been paid close attention to for its sinusoidal current of grid side, controlled power factor and bidirectional energy flow. In view of the existing problems of the dual PWM converter, deep researches have been done in the aspects of the theoretical analysis, computer simulation and experimental prototype in the paper.The main research contents and innovation are shown as following. The mathematical model of PWM power converter is constructed based on the function and characters of PWM converter and instantaneous power theory. The instantaneous power flow of PWM converter is analyzed. The principle of switching vector in traditional DPC control system is analyzed. The reactive power is out of control near the fundamental voltage vector in traditional DPC system, which leads to the current distortion at AC side and the voltage fluctuation at DC side. The 18 sector division method is proposed and the corresponding switching table is obtained based on power mathematical model of PWM converter. The defects on reactive power control in traditional DPC are overcome, and the steady and dynamic effects are improved.The integrated control of dual PWM converter based on load power feed-forward method is researched. The compensation principle and dynamic response of two typical power feed-forward control models are analyzed. The prediction of load power to be fed forward is developed, from which the DC bus voltage is immune from load power command through the rational controller parameters. The influence of power estimation error on DC bus voltage is analyzed. It is pointed out that the performance of dual PWM converter is excellent when the power estimation error is small. Furthermore, the vector control of permanent magnet synchronous motor is studied, and the estimation power calculation method is obtained.In order to improve the DC bus voltage dynamic response speed, and restrain DC bus voltage fluctuations, the direct capacitance power control method is proposed. The deficiency of traditional feed-forward control method is analyzed. The small signal model of dual PWM converter is analyzed. Dual PWM converter integrated control based on the direct capacitance power control is put forward. Instead of reactive power control loop, a capacitance power control loop is used. The decoupling control of the dual PWM converter is realized by setting capacitance instantaneous power zero. In traditional load power estimation, the accuracy depends on motor parameters. A load power observer is introduced in this paper, the inputs of which are merely through measuring rectifier output current and DC bus voltage, and it can estimate the inverter input power.