Guidelines for Single-Parameter Multiresonant Current Controllers Design Allowing Prescribed Magnitude Tracking of Periodic References

Unlike grid-connected and motor driving converters, typically exchanging sinusoidal current with the grid/motor, inverters employed in uninterruptible power supplies and active power filters generate periodic, harmonics-rich currents. Consequently, current controller in these applications must be capable of accurate tracking of references containing high harmonic count, calling for a multiresonant structure. On the other hand, major disturbances influencing the current loop comprise output and dc link voltages, which can typically be measured/estimated and cancelled by a feed-forward action. Thus, the current regulation problem is reduced to tracking challenge only. Recently, methodology for designing single-parameter single-resonant controllers according to desired tracking behavior of ac signal amplitude was proposed by the authors. However, as shown in the article, straightforward extension of the algorithm to multiresonant case is unfeasible. Nevertheless, it is possible to obtain an accurate approximation utilizing the decoupling property of resonant terms in both frequency and time domains. As a result, simple single-parameter multiresonant controller design guidelines are derived, imposing similar transient response to each individual harmonic of periodic reference. Simulations and experimental results validate the proposed design methodology.