Modified Resonant Controllers with Time Delay Compensation

The resonant (R) controllers are widely applied to reduce ripple current/voltage in three-phase systems with power electronic converters. The digital signal processor (DSP) implementation of R-control implies a time delay due to online computation and discretization effects. The time delay produces an associated phase lag and causes deterioration of the transient operating performance as well as of the system stability. To overcome this drawback, the two modified schemes are considered in this paper for an R-control component, and one of them have never been presented before. The comparative analysis of proposed R-controllers is performed by using Bode diagrams in a frequency domain. As can be seen from the simulation results, while operating frequencies are less than the resonant frequency, a transfer function with the first order numerator is more suitable choice. In contrast, at operating frequencies exceed the resonant frequency, the transfer function with the second order numerator should be used to achieve appropriate transient performance because its frequency response is closer to the conventional R-controller. For this reason, it is more preferable to employ the R-controller scheme for digital implementation that combines simultaneously two transfer functions with time delay compensation.