A First Order Sliding Mode Controller for Grid Connected Shunt Active Filter with a LCL Filter

A first order sliding mode controller with appropriate parameters sliding surface (modeled in usual time domain and realized by transfer function) is considered here for LCL grid connected three phases three wires shunt active filter (SAF). If shunt active conditioners are already well known in compensation for the main types of current disturbances in the electrical power systems, it is also admitted that they generate some undesired components caused by VSI switching frequency. In order to prevent these components from spreading to the grid side, a LCL output filter is generally proposed. In this context, a VSI connected grid via a LCL filter is largely proposed for renewable energy systems, where the component to be injected into the grid is only the fundamental. Unfortunately, when the injected components include fundamental plus harmonics and for a LCL output filter associated to linear controllers, a phase shift appears, between the identified harmonics current and the injected current. This phase shift impacts negatively the current disturbances filtration and/or compensation of the SAF. Therefore, sliding mode controller with appropriate sliding surface, in both time and frequency domains, is proposed as nonlinear control method, to overcome the phase shift effects over the entire bandwidth, for the shunt active filter. Besides, a PWM-SM-Controller, with zero order hold in input of the PWM, will allow to operate in a fixed frequency, preventing a variable switching frequency effects. The rapidity, tracking and robustness of this proposed controller, within the SAF, are validated by Matlab, Simulink, Simscap-Sim_Power_System code.