A Novel Technique for Switching States Reduction with Capacitor Voltage Balancing for CHB Converter Based on Model Predictive Control

Model Predictive Control (MPC) has proven to be a powerful tool for power converters control. Its fast dynamic response and capability to deal with nonlinear variables has made it a choice for many applications in the power grid, including Cascaded H-Bridge (CHB) multilevel converters. However, for CHB converter application, the number of switching states to be analyzed at each sample time grows exponentially with the number of converters, significantly increasing computational cost. Also, voltage balance among DC links capacitors is a challenging issue. In this context, this work presents MPC fundamental theory, as well as a proposal for reduction in the number of control states and an improvement in capacitor voltage balance for a 7-level CHB converter. Experimental results of a STATCOM prototype implemented using the proposed algorithm are presented to validate the technique both in steady state and transient regime.