Direct Power Control Of Three-phase PWM Reversible Converter

Three-phase PWM reversible converter can effectively suppress the power grid pollution caused by the harmonic and reactive power because of its input sinusoidal current,adjustable power factor and doubly flow of energy.And it has been widely used in active power filtering,static var generator,renewable energy power generation and electric vehicles.The direct power control(DPC)receives much concern as an effective control strategy for three-phase PWM reversible converter due to its simple structure,excellent steady and dynamic characteristics.The DPC control strategy of three-phase PWM reversible converter is mainly studied in this thesis.Firstly,the operation principle of three-phase PWM reversible converter is analyzed,and the mathematical model of three-phase PWM reversible converter based on current control is deduced in ??coordinate and dq coordinate respectively.According to the instantaneous power theory,a mathematical model of three-phase PWM reversible converter based on power control is established in this thesis.Secondly,in order to remove the AC voltage sensor,the virtual flux(VF)is introduced into three-phase PWM reversible converter.Besides,the virtual flux observer based on the second-order filter is used to solve the integral drift and DC bias problems.The influence of space voltage vector on the instantaneous power is detailed discussed,and a virtual flux based direct power control(VF-DPC)is analyzed in this thesis.For the variable switching frequency of VF-DPC,the power predictive inner loop and space voltage vector modulation(SVM)are applied.The virtual flux based predictive direct power control(VF-P-DPC)in two coordinate is analyzed separately.what's more,the VF-P-DPC based the internal model principle in?? coordinate is improved to eliminate steady error existing in the traditional VF-P-DPC.And a simulation is built to verify the correctness of the theory.Finally,the experimental platform of three-phase PWM reversible converter is established,including hardware and software.The VF-DPC and VF-P-DPC in two coordinate control strategies are achieved and compared on the platform.The experiment results demonstrate the validity of the proposed control strategies.