Acoustic feedback is a well-known problem in hearing aids, which is caused by the undesired acoustic coupling between the loudspeaker and the microphone. The goal of adaptive feedback cancellation (AFC) is to adaptively model the feedback path and estimate the feedback signal, which is then subtracted from the microphone signal. The main problem in identifying the feedback path model is the correlation between the near-end signal and the loudspeaker signal, which is caused by the closed signal loop. In this paper, a novel prediction-error-method (PEM)-based AFC is presented using a harmonic sinusoidal near-end signal model. Furthermore, the prediction error filter (PEF) is designed to incorporate a variable order and avariable amplitude next to a variable pitch. Simulation results for a hearing aid scenario indicate an improvement up to 6dB in maximum stable gain increase and up to 8dB improvement in terms of misadjustment.