Abstract: Abstract: Harmonic compensations have become increasingly important in power systems due to the rapid proliferation of nonlinear loads in industrial, commercial, and residential applications. Harmonics not only increase the losses, but also produce unwanted disturbance to the communication network, more voltage and/or current stress, and so on. Different mitigation solutions, such as passive filter, active power line conditioner, and hybrid filter, have been proposed and used to solve the problems. Due to the excellent dynamic performance, shunt-type active power filter (APF) is used to eliminate the current harmonics. The aim of the paper is to apply the feedback linearization theory in the single-phase shunt-type APF via a sliding mode control approach. The control of the active filter is performed by 2 digital control loops: a sliding control surface in the inner loop, which linearizes the system dynamics and compensates the nonlinear load current distortion, and a conventional PI (proportion integration) control in the outer loop that regulates the level of the direct current side capacitor voltage. In this paper, firstly, the modeling of a single-phase APF is presented, which uses a standard full-bridge voltage-source inverter topology and a unipolar method, and the affine nonlinear model is obtained as well. Secondly, the APF's system is linearized by means of a nonlinear coordinate transformation, deduced from the application of the differential geometry theorem to the system. The feedback linearization is achieved by the definition of an output function for the system that is based on the total energy stored in the APF. In the linearization process, any higher order nonlinear term is not ignored, and thus the linearized model can accurately reflect the real system. The feedback linearization of the system is performed without the need to transform the active filter model into a normal form, avoiding the tedious mathematical operations that are involved in this transformation, saving the computation space of the DSP (digital signal processor) and simplifying the final control configuration. Then, a sliding model controller is designed based on the linearized APF model, which guarantees the rapidity and accuracy of the compensation current and weakens the dependence on accurate mathematical mode at the same time. Finally, detailed simulation and experimental results were reported, demonstrating the validity of the proposed control scheme. In MATLAB simulations, the proposed controller was compared under the same control parameters and conditions with a conventional PI control scheme. The current total harmonic distortion (total harmonic distortion, THD) was 3.83% under conventional PI control and was 1.18% under control method proposed in this paper. This comparison showed that the proposed control approach achieved a strong harmonic attenuation all over the frequency spectrum of the supply current, leading to a signi?cant reduction of the current THD. The THD of the grid current that was compensated was 2.71% in experiments. Thus, it can be seen that the proposed method employed in the paper is much more reasonable, and has a high value in practical applications.