The Research On Dual-PWM Converters With Power Combined Control Scheme

ABSTRACT:Double PWM AC-DC-AC voltage source frequency control system which consists of PWM rectifier, PWM inverter and AC induction motor was established using parameter estimation theory, space vector and the theories of virtual flux. The dissertation presents a new type of virtual flux estimation algorithms of estimation of low-pass filter compensation, which can solve a key issue of virtual flux estimation in control strategy without voltage sensors. The dissertation presents the voltage decoupling control programs in vector control system to achieve the dynamic decoupling completely between the current torque and excitation current, and gives a design scheme of simplified system controller. To achieve the minimum capacitor in the DC side of dual PWM converter, integration coordinated control strategy of the direct control on the capacitor current is proposed based on current feed-forward control strategy, therefore dynamic speediness of the system is accelerated. Its mathematical model was established to analyze load fluctuation characteristics of current direct feedback method. VSR control strategy under imbalance in the power network was researched; the performance of two different control strategies of inhibiting negative sequence current in the AC side and the 2nd harmonic in the DC voltage side has been attained. The dissertation presents T/3 time delay separation method, which can accurately separate the positive and negative sequence components of the imbalance power without error, to improve the control characteristics of VSR. A set of physical test platform of 5.5KW double PWM converter has been developed for four quadrant movement. The dissertation research conclusions were strongly verified accurate by the simulation and experimental results.