Sliding Mode-Based Active Damping Control of LCL-Filtered Three-Phase PWM Rectifier

This paper presents a sliding mode control (SMC) approach for active damping to a three-phase LCL-filtered unity power factor PWM rectifier. A multi-loop framework is applied in controller design to achieve fast dynamic response, good tracking ability and damp the LCL filter's resonance. The inner loop ensures active damping by sensing filter capacitor voltage. A sliding mode controller is employed in this layer. In the mid-loop of the proposed multi-loop framework, PI controllers in the synchronous reference frame are used to continue the unity power factor easily. Thus, the efficient use of PI controllers to generate line current references in the mid-loop is enabled. Also, another sliding mode controller is used in the outer loop to control the DC voltage and achieve enhanced dynamic response. The performance of the proposed strategy has been validated with simulation and experimental studies. Besides, the proposed system is compared with the conventional synchronous reference frame PI-controlled PWM rectifier. The results demonstrate that the system's dynamic response is faster than the PI-controlled system. It is also seen that the resonance occurred by the complex conjugate poles of the LCL filter is successfully damped by the SMC-based inner controller. This controller eliminates the damping resistor use and related power loss as well. Besides, the harmonic components of the input current meet the IEEE 519 standard and unity power factor operation is ensured.