Improved Deadbeat Control of Current-source PWM Rectifier under Unbalanced Grid
Three-phase current source PWM rectifier runs under the unbalanced grid voltage,which causes a large number of low-order harmonics in DC side and grid side current,which is bound to have adverse effects on the power supply stability and safety of the later converter.To address this problem,firstly,a mathematical model of rectifier is established,and the expressions of DC-side voltage and grid-side current under unbalanced power grid are derived,revealing the mechanism of low-order harmonics generated by DC-side and grid-side current of the system.Secondly,the inner-loop current reference command is designed based on the instantaneous power theory,and the deadbeat control is used to realize the tracking of the grid-side current to the reference current.However,the traditional deadbeat control has a delay problem,which will affect the following performance of grid-side current and cause the power quality to decline.In order to solve this problem,an improved deadbeat control based on inner loop of grid-side current is proposed,and the system delay is compensated by two-step prediction method.Finally,a simulation model is built based on Matlab/Simulink platform to verify the correctness and effectiveness of the proposed control strategy.The results show that the proposed method can effectively suppress the low-order harmonics of DC side and grid side current,and realize sinusoidal grid side current and stable DC side voltage output.
万方数据
维普
