Finite-control-set economic model predictive control for a DC/AC inverter

Finite-control-set model predictive control (FCS-MPC) is an effective approach for controlling modern power electronics. The three-level sparse neutral point clamped inverter (3L-SNPCI) fulfills the task of converting DC power into the desired three-phase AC power in high-renewable-penetration power systems. The stable and economic operation of the 3L-SNPCI is crucial to the security and reliability of renewable energy grid connection. Controlling of 3L-SNPCI is quite challenging, due to the strong nonlinearity and the discrete feasible region caused by the finite control set. In this paper, a stable economic model predictive control scheme is developed to achieve the key tasks of current tracking, neutral point voltage balance, and inverter economic performance by directly incorporating the economic indices into the controller design. The non-convex optimization problem caused by the inverter nonlinearity is transformed into a convex one with linear inequality constraints by employing the Big-M method. The bounded stability is indirectly guaranteed with the dynamic of the inverter control system approximating that of a stabilized continuous linear time-invariant system sharing the same parameters. Simulation and experiment concerning both the steady-state and transient-state conditions with different disturbance are presented to show the effectiveness and robustness of the proposed controller.