Control of Induction Motor Drive based on Nested Neutral Point Clamped Inverter using Finite Control-Set Model Predictive Method

Abstract

This paper presents a finite control set model predictive control for a four-level nested neutral point clamped converter (4L-NNPC) in electric drive application. Controlling the voltage of the flying capacitors (FCs) in this converter, especially at low output frequency, is challenging due to the lack of complete switching states to control the FCs voltages. In the proposed method, the main control objectives of the electrical motor and converter, i.e., the control of the torque, flux, and voltage of the FCs, have been formulated. A modified weighting factor for FC voltage objective in the cost function is introduced, which provides the full possibility of controlling voltage fluctuations of FCs, especially in low-frequency operation. The proposed control method, in addition to controlling the electric motor's required objectives, can control the voltage of the FCs of the converter in the entire operating frequency range. The performance of the proposed method has been simulated and verified on a 4L-NNPC converter using a 1500 HP, 4160 V electric drive in the MATLAB/Simulink software environment.

Keywords

• nested neutral point clamped converter
• electrical drive
• capacitor voltage balancing
• model predictive control