Reference generation for harmonics cancellation, displacement power factor correction and unbalance compensation under unknown fundamental frequency

This paper proposes schemes for current reference generation for shunt active filters under unknown fundamental frequency. The schemes are based on the linear Kalman filter and provides current reference to compensate harmonics, the displacement power factor related to the load and unbalance. Since the Kalman filter uses a mathematical model that includes the value of the fundamental grid frequency and, in some applications, this value can vary, it is necessary to update the filter model with the correct frequency value. Therefore, this paper also proposes the use of on-line identification of the fundamental frequency of the power system. The identified frequency is used to update the Kalman filter model.