Modified LUT-based DTC of NPC 3-Level Inverter fed Sensorless IPMSM Drive with DC Link Voltage Balance

Abstract

In the proposed work, a modified look-up table-based direct torque control (DTC) scheme is reported for a neutral point-clamped three-level inverter-fed interior permanent magnet synchronous motor drive. In the classical DTC scheme, there are significant torque and flux ripples in the drive due to low number of available switching states. To reduce the oscillations in torque and flux, a three-level inverter-operated IPMSM drive is discussed. In a three-level inverter, the increased count of active voltage vectors is results in more sinusoidal output waveforms. Moreover, stator flux plane has 12 sectors in the proposed work unlike classical DTC. Besides, the higher level of flux and torque hysteresis comparators is implemented. DC link capacitor voltage balancing scheme is also instigated to minimize voltage stress on semiconductor devices, improve stator current THD and increased capacitor life. Based on the sector information, flux and torque hysteresis output and capacitor voltage balance logic, an improved LUT is established and explained for a three-level DTC scheme. Consequently, improved stator current (THD) and decrement in torque and flux ripples are observed. To make the system robust, model reference adaptive control (MRAC) based sensorless speed estimation algorithm is realized. The proposed DTC scheme is compared with a two-level inverter-fed and a three-level-inverter-fed DTC scheme without DC link voltage balance strategy. To carry out the analysis, MATLAB/Simulink environment is utilized. Moreover, to validate the simulation results, experimental analysis of the proposed technique is carried out using dSPACE1104.

KEYWORDS:

• DTC
• Look-up table (LUT)
• Multi-level inverter (MLI)
• Neutral point clamped (NPC)
• Permanent magnet motor
• Space vector

Acknowledgement

The author would like to acknowledge the Council of Scientific & Industrial Research (CSIR) for the funds under Extra Mural Research Scheme. The funds helped to purchase the required equipment and perform the task.

Additional information

Funding

This work was supported by the Council of Scientific and Industrial Research, India.

Notes on contributors

Toshi Sharma

Toshi Sharma was born and brought up in Bhopal, Madhya Pradesh. She received her BE degree in electrical and electronics engineering and ME degree in power system from RGPV, Bhopal, in 2010 and 2013, respectively. Currently, she is working toward her PhD in the area of electric drive and power electronics at the Department of Electrical Engineering, Indian Institute of Technology, Roorkee. Her research areas include electric machines, power electronics, electric drives, and electric vehicles. Email: [email protected]

Avik Bhattacharya

Avik Bhattacharya is from Kolkata, West Bengal. He received his MTech degree in machine drives and power electronics and PhD in power quality from IIT, Kharagpur, in 2005 and 2010, respectively. Currently, he is working as an assistant professor at the Department of Electrical Engineering, Indian Institute of Technology, Roorkee. He is the author of many papers published in national and international journals and conferences. His area of research includes power quality, AC-DC microgrids, solid state transformers, direct and indirect matrix converters, FACTS devices, electric machines, power electronics, electric drives, and electric vehicles. Email: [email protected]