Model Based Adaptive Direct Power Control for Three-Level NPC Converters

In this work, a Model Based Adaptive Direct Power Control (MB-ADPC) with constant switching frequency for Three-Phase Three-Level Neutral Point Clamped (3L-NPC) converters is proposed. The rectifier and inverter operation mode are used to illustrate the flexibility of the proposed MB-ADPC controller. The control design process is based on the continuous averaged model of the system. Depending on the operation mode different control objectives have to be guaranteed. The proposed controller ensures the voltage regulation of the dc-link capacitors for the rectifier operation mode and to achieve voltage balance in the dc-link capacitors and the active and reactive power tracking for the rectifier and inverter operation modes. In addition, adaptive techniques are used to avoid system parameters uncertainties as smoothing inductors and grid frequency values. This work shows that the application of advanced control strategies based on the system model allows enhancing the performance of the overall system. The details of the controllers design process and the experimental results using a 50 kVA Three-Phase Three-Level NPC prototype are presented in this paper validating the proposed controllers.