Application of the Min-Projection and the Model Predictive Strategies for Current Control of Three-Phase Grid- Connected Converters: A Comparative Study

Abstract

This paper provides a detailed comparative study concerning the performance of Min-Projection Strategy (MPS) and Model Predictive Control (MPC) systems to control the three-phase grid connected converters. The MPS approach is already applied in synchronous reference frame by authors. However in this paper the algorithm is modified to be realized in the stationary reference frame which brings considerable simplicity and ease of implementation and then the MPS is compared with MPC. To do so, first, the converter is modeled as a switched linear system. Then, the feasibility of the MPS technique is investigated and its stability criterion is derived as a lower limit on the DC link voltage. The mathematical analysis reveals that the MPS is independent of the load, grid, filter and converter parameters. This feature is a great advantage of MPS over the MPC approach. However, the MPC is a mature model-based control technique, which has been already developed for controlling the VSC in the stationary reference frame. For comparing, both MPS and MPC approaches are simulated in the PSCAD/EMTDC environment. Simulation results illustrate that the MPS works well and is less sensitive to grid and filter inductances as well as the DC link voltage level. However, the MPC approach offers slightly a better performance in the steady state conditions.