Finite-control-set model predictive control scheme of three-phase four-leg back-to-back converter-fed induction motor drive

The three-phase four-leg back-to-back converter-fed induction motor drive with only eight switches has the capability of variable-frequency speed control and bidirectional power flow. It can provide the benefit of higher reliability and less cost in comparison with the full-bridge back-to-back converter. On the other hand, the four-leg back-to-back converter can be utilised in fault-tolerant control to solve open-circuit fault occurring at both rectifier and inverter leg in a full-bridge back-to-back converter. However, the deviation of the two capacitor voltages which will lead to variation of voltage vectors in both amplitude and phase angle hinders its applications. This study proposes a control scheme based on finite-control-set model predictive control to remedy this disadvantage. With the proposed scheme, capacitor voltage deviation is suppressed. Bidirectional power flows and balanced input and output currents are achieved. The effectiveness of the proposed scheme is verified by the experimental results presented.