FPGA based direct model predictive power and current control of 3L NPC active front ends

Three-level neutral-point clamped (NPC) power converter is a viable candidate for high power grid-tied renewable energy generations. Direct model predictive control (DMPC) is a good alternative, in particular for multi-level converters. This work presents and experimentally evaluates two DMPC schemes for controlling a grid-tied Active-Front-End (AFE) with a fully FPGA based solution. The two methods are namely, direct model predictive power control (DMPPC) and direct model predictive current control (DMPCC). Both use a cost function based (nonlinear) control concept to regulate the control objectives and require no extra modulations. Their relationship has been analyzed. Both their steady state and transient phase performances are evaluated through experimental data, which confirm that, similar control performances are achieved by both, except that, slightly smaller current ripples are seen with DMPPC. The possible reasons are also given.