A current control strategy for a three-phase shunt active power filter using second-order sliding mode

A combined 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. A double twisting algorithm to control the DC voltage is used. In it, to calculate the “operator variable”, in addition to the error of the capacitor storage voltage to increase the speed is also used its derivative. A two-dimensional sliding manifold to generate the compensating current is used. Each component of this surface is a linear combination of components of two-dimensional vectors. The first vector is the current error of the RL filter, the coordinates of the second are locally equivalent to the derivative of this error. The calculation of the instantaneous value of both components of the second vector by entering the second order sliding mode was forced. A simulation model is developed and the results of simulation 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.