Harmonic Current Compensation for LCL Filtered Shunt Active Power Filter

The harmonic compensation currents generated by the Shunt Active Power Filter (SAPF) employing inverter-side current feedback control are distorted by the LCL filter. In the case of a large-capacity SAPF with a low resonance frequency of the LCL filter, the distortion between the LCL filter's inverter-side current and grid-side current becomes more severe. Grid-side current can be used as feedback current for harmonic current control of SAPF. However, this control scheme requires additional overcurrent protection sensors and has current control stability issues. This paper proposes the inverter-side harmonic current reference compensation method to control the grid-side harmonic currents indirectly. Since the proposed method controls the inverter-side current, it can stably control the harmonic current, and at the same time, it can improve the harmonic current quality of the AC grid by accurately supplying the harmonic current required for the system.