An Optimal Pole Placement State Feedback with Feedforward Digital Control Applied to a Three-Level NPC Inverter Implemented in FPGA

This paper presents an Optimal-Pole-Placement Control (OPPC) combined with Feedforward (FF) scheme to control a 1 phi-3L-NPC-Inverter. The OPPC is an optimal linear state feedback control that improves the transient response time with controlled input/output current and voltage overshoot. The inclusion of a feedforward branch between the reference signal and duty-cycle strategy ensures null steady state error and it reduces the output voltage distortion as well as the response time of the DC bus capacitor voltage balancing. To verify the performance of the NPC-Inverter, the proposed control is compared to a dual PI voltage and current control loops strategy. For both control schemes, the system uses just a voltage sensor, with the current calculated from the voltage. Simulations results using the Altera DSP Builder software in a Matlab/Simulink environment are presented to demonstrate the NPC-Inverter performance implemented in FPGA.