Modulated model predictive current control of HERIC AFE converter equipped with LCL filter

Abstract

This paper proposes a modulated model predictive control (MMPC) of a highly efficient and reliable inverter concept (HERIC) active front end (AFE) converter equipped with an LCL filter. The proposed method is based on the model predictive control (MPC) concept and obtains the optimized duty cycle by using three-level switching states which can be implemented in the HERIC converter. By doing so, the AFE converter achieves fast and precise current control. In addition, the obtained duty cycle is not limited to the polarity of the grid voltage, so it is possible to track the current reference more accurately near the zero-crossing points. The first-order approximation model of the LCL filter is derived to simplify the controller design process with the proposed MMPC. After that, the MMPC algorithm is adopted based on this simplified model in the single-phase system. The switching pattern of the HERIC topology is also proposed considering the MMPC under changing polarity of the duty cycle. To verify the performance of the proposed scheme, a 3 kW HERIC AFE converter was built and tested. Both simulation and experimental results demonstrate that the proposed scheme not only improves total harmonic distortion, but also achieves a fast-tracking performance.