Enabling Multistep Model Predictive Control for Transient Operation of Power Converters

Abstract

Recently, an efficient multistep direct model predictive control (MPC) scheme for power converters has been proposed. It relies on the Sphere Decoding Algorithm (SDA) to solve the associated longhorizon optimal control problem. Since the SDA evaluates only a small number of candidate solutions to find the optimal one, a significant reduction in the average computational burden can be achieved compared to the basic exhaustive search approach. However, this is only true during steady-state operation. In fact, the SDA still requires a large execution time during transients. This paper shows that if not properly addressed, the dynamic performance of the system may be degraded, which clearly limits its practical application. To mitigate this issue, which particularly arises during transients, an efficient preconditioning approach for the SDA is proposed. This approach ensures that only a small number of candidate solutions are evaluated during both steady-state and transients. This allows the multistep direct MPC to become a viable control alternative for power converters operating at low semiconductor switching frequencies, e.g., below 450 Hz. The proposal is validated using a grid-connected three-level converter as a case study. Both processor-in-the-loop simulations and experimental results on a scaled-down 2.24 kVA laboratory setup are presented. INDEX TERMS Model predictive control, Integer least squares problem, Sphere decoding algorithm, Convex hull, Quadratic programming solver, Power converters.

Long Prediction Horizon FCS-MPC for Power Converters and Drives

“…k is chosen, a large initial radius ρ ini will be always obtained. To overcome this problem, a computationally efficient preconditioning approach for the SDA during transient was proposed in [12], [17], and [57]. This approach consists of obtaining a new center k for SDA during transients by projecting U unc k onto the boundary of C H .…”

Latest Advances of Model Predictive Control in Electrical Drives—Part I: Basic Concepts and Advanced Strategies

“…the prediction horizon was obtained considering that transients are one of the main causes of impracticability due to the SDA initialization [73]- [75]. Thus, a selective initialization approach choose the box-constrained initialization during transients while preserving the well-known dynamic performance of FCS-MPC at minimum sub-optimality cost, without affecting the steady-state performance.…”

Hybrid Switching of Four-Voltage-Vector Model-Free Predictive Current Control for Four-Switch Three-Phase Inverter-Fed SynRM Drive Systems

“…With the recent progress in the development of control technologies, some advanced methods have been proposed for SynRM, such as slidemode control, finite-control-set model predictive control (FCS-MPC), and fuzzy control. In particular, the finitecontrol-set MPC has received significant attention as a viable alternative to motor drive controls and power converters [16], thanks to its intuitive design, quick response, and multivariable approach. The FCS-MPC uses the equivalent discrete-time model of the system to predict the future behavior of the controlled variables, such as current, flux, or torque.…”