HARMONIC DETECTION METHOD AND ACTIVE POWER FILTER

Disclosed are a harmonic detection method and an active power filter. The method comprises: an active power filter (APF) using a phase-locked loop to determine a phase angle θ of a voltage of a power grid; detecting load currents Ia, Ib and Ic of the power grid, and transforming the load currents Ia, Ib and Ic from an abc coordinate system into iα and iβ in an αβ coordinate system; determining a transformation matrix according to an Nth harmonic needing to be extracted and θ, and using the transformation matrix to transform iα and iβ from the αβ coordinate system into id and iq in a dq coordinate system, wherein id includes a direct-current component INd and an alternating-current component ĨNd, iq includes a direct-current component INq and the alternating-current component ĨNq, and N is an integer greater than or equal to 1; and filtering the alternating-current component ĨNd of id to obtain INd, filtering the alternating-current component ĨNq of iq to obtain INq, and inversely transforming INd and INq to obtain an Nth harmonic current. By means of the technical solution of the embodiments of the present invention, a harmonic current can be quickly detected, wherein same is convenient and simple.