Efficient multiple-reference-frame controller for harmonic suppression in custom power devices

•Efficient implementation of controllers in multiple reference frames.•Voltage sags, harmonics and unbalances in the supply voltage are tackled.•The controller deals with slow grid frequency variations.•Experimental results are presented.

Tracking harmonic currents and voltages in electric power systems with custom power devices exceeds the capabilities of conventional Proportional+Integral controllers and more sophisticated algorithms are required, especially under grid-frequency variations. This paper presents a control method based on multiple reference frames for harmonic control in the context of a series active power filter. The proposed scheme allows recursive calculation when referring signals to reference frames rotating synchronously with harmonic equivalent space vectors whilst a minimum of trigonometric-function evaluations are required. Furthermore, the control of each harmonic can be dealt with using simple integral controllers applied to the transformed signals. The paper presents the closed-loop-stability analysis and experimental results of a series active power filter. A scenario with grid-frequency variations is considered to show the intrinsic adaptation capability of the proposed controller.