三相LCL-LC型仅网侧反馈的改进时滞抑制OA北大核心CSTPCD

The active damping(AD)of LCL-LC voltage source inverter with only grid-side current feedback reduces the use of detection components in comparison with the AD with capacitor current feedback,which can effectively suppress resonance peaks generated by LCL-LC inverters.However,due to the control delay effects of digital circuits,variations of grid impedance will cause the shift of resonance frequency(fr).When fr is near 1/6 of the sampling frequency(fs),the system becomes unstable.To eliminate the impact of control delay on the inverters when LCL-LC AD inverters only have grid-side feedback,the influence of changes of grid impedance on system stability in the digital domain is studied,and a novel delay compensation method,that is,an improved delay compensation is added to the feedforward path of the control loop,is proposed.In this method,the equivalent positive resistance of AD is extended from the fs/6(the original)to 0.496 5fs.Because of the compensation of widening the equivalent positive resistance,the system remains stable around fs/6 even when fr shifts,which enhances system stability greatly.Simulation and experimental results validate the theoretical correctness of the method.