Modulated Predictive Voltage Control of a Four-Leg Inverter with Fixed Switching Frequency

In this paper, a novel modulated model predictive voltage control method is proposed for a two-level four-leg inverter with an output LC filter. To decouple the dynamics of state variables in an output LC filter and to improve the load voltage quality, the capacitor voltages and inductor currents are controlled simultaneously. The proposed controller predicts the state variables using the discrete-time model of LC-filtered four-leg inverter for 16 voltage vectors and evaluates them by a dual-objective cost function. The active and zero voltage vectors corresponding to the lowest cost value are realized by the three-dimensional space vector modulation, resulting in fast transient response, low steady-state error, and harmonic components centered around the fixed switching frequency. The proposed method's feasibility is confirmed through MATLAB simulation studies under balanced/unbalanced reference voltages and nonlinear loads. The performance comparison of proposed controller with the classical predictive voltage control is presented considering the transient and steady-state operating conditions.