Sensorless Nonlinear Control Strategy of the Single Phase Active Power Filters via Two-time Scale Singular Perturbation Technique

摘要

This paper focuses on the problem of controlling single-phase shunt active power filters (APFs) operating in the presence of nonlinear and uncertain loads. The main difficulties when controlling this kind of filter are the existence of a strong non-linearity of the system and state variables inaccessible to measurements. This paper proposes a double-loop cascade controller developed on the basis of the singular perturbation technique in order to meet two main control objectives: (i) the inner-loop is designed to compensate the harmonic and reactive currents absorbed by the nonlinear load enforcing power factor correction; (ii) the outer-loop is synthesized to regulate the inverter output capacitor voltage. The controller also includes two-time scale sliding mode observer to estimate the network voltage that is not accessible to measurement. In this work, the singular perturbation technique and averaging theory are used for a complete and rigorous formal analysis to describe the control system performances. The effectiveness of this approach has been successfully verified through computer simulations using the Matlab/Simulink environment.