A simple control strategy for a three-phase shunt active power filter based on second-order sliding mode

A simple control strategy of the three-phase shunt active power filter that is connected to a non-linear load network is proposed. The filter consists of a voltage source inverter on fully controlled switches, capacitor storage, and a first-order three-phase RL filter. The decomposition of the object of study according to the rates of motion of the dynamic system was performed. The fast subsystem is a circuit of compensation current control, the slow subsystem performs stabilization of the capacitor voltage. An asymptotic double-twisting algorithm to control the DC voltage was used. For the current formation, a two-dimensional sliding surface is used, which is a linear combination of the components of two-dimensional vectors - the error of the current of the RL filter and some variable. The double-twisting algorithm to calculate the instantaneous value of this variable was also used. A simulation model is developed and the results of digital experiments are analyzed. A comparison of the proposed strategy with the traditional PI-regulation by the criteria of the duration of the transition process and the coefficient of harmonic distortions in the current consumed from the network is made.