Design of a Voltage-Controlled Active Power Filter with non-invasive Grid-Impedance Observer for the Compensation of Distortion Reactive Power

Due to increasing numbers of renewable energy sources (RES) and power electronic devices connected to the medium- (MV) and low-voltage (LV) power supply network (PSN), non-linear currents and especially distortion reactive power become more present in electrical grids. The resulting voltage distortions at the (internal) point of common coupling (IPCC /PCC) will be a major issue in future power grids [28]. Without appropriate compensation techniques the distorted (I)PCC voltages will affect the operation of loads. To encounter this issue, the application of active power filters (APFs) is considered as one of the most promising approaches for harmonic compensation (HC). According to the state of art, APFs generally operate in current-controlled mode (CCM). Initial approaches of APFs in voltage-controlled mode (VCM) refer to the (I)PCC voltage, operate with integrated grid-impedance estimation and eliminate the need of additional current sensors. To reduce their computational effort, this paper introduces a novel control algorithm with proportional-resonant (PR) controllers and a non-invasive grid-impedance observer. To validate effectiveness and feasibility of the novel VCM-APF, a testbench evaluation has been performed. The results clarify: the novel control-approach in combination with non-invasive grid-impedance estimation fulfills all requirements of a functional VCM-APF.