Decoupled Predictive Current Control With Duty-Cycle Optimization of a Grid-Tied Nine-Switch Converter Applied to an Induction Generator

The nine-switch converter (NSC) was developed aiming at the reduction in the number of power converter switches in multiport systems, such as variable-speed drives for power generation. Among the possible control techniques for the NSC, finite-control-set model-predictive control (FCS-MPC) stands out due to its fast dynamics and easy incorporation of system restrictions. However, converters with many switching possibilities and control goals increase the computational burden and the cost function complexity. Moreover, FCS-MPC can present high ripple values in the system outputs. This article proposes a decoupled predictive current control with duty-cycle optimization (PCC-DD) for the NSC, which decouples the control of an induction generator from the grid control. The separation between grid and generator controls decreases the enumeration of voltage vectors to be performed, reducing computational burden. Then, duty-cycle calculations are responsible for reducing torque and active power ripples. Experimental results show that PCC-DD provides lower ripple factors for the desired variables when compared to the approach with a concentrated cost function. The main contribution is a better steady-state performance with a lower computational burden. Therefore, PCC-DD is a suitable low-ripple technique for NSC control and for application to power generation with variable-speed generators.