A new control method for eliminating the 2nd harmonic at the DC link of a shunt APF under an unbalanced and nonlinear load

Under an unbalanced load 2
^nd
harmonic DC link and 3
^rd
harmonic at AC input current of a shunt APF appear due to the fundamental negative frequency load current. These low order harmonics can cause a series of high order harmonics at both of AC and DC sides. In this paper a new control method is presented to eliminate the 2
^nd
ripple of DC link voltage to alleviate the stress of the DC-link capacitor and thus to reduce the 3
^rd
harmonic of line currents.