Cascaded H-Bridge Multilevel Inverter Fed Pmsm

Abstract

Inverter is an electronic device used to convert direct current(DC) into alternative current(AC). Inverters can also be called AC drivers or variable frequency drivers(VFD). They are used in solar systems, adjustable-speed ac motor drivers, UPS(uninterrupted power supplies), power transmission industry etc.The Cascade H-bridge inverter is one of the three main types of multilevel inverters. It was mainly developed for utility applications. The permanent magnet synchronous motor(PMSM) is an AC motor with a sinusoidal EMF waveform. It is widely used in actuators, robotics, machine tools, traction, aerospace technology, automobiles and is very much considered in industrial drives, vehicular propulsion etc. As there is no stator power for magnetic field production in PMSM, the power density is higher than one of induction motors with the same ratings. PMSM has low torque ripple effect and has higher operational efficiency with no magnetising current. In this paper a cascade multilevel inverter is fed to PMSM.

Code Description & Execution

Algorithm Description

Modelling of PMSM : The diverse model of PMSM was derived using a two phase motor in d-q (direct and quadrature) axes. This model contains magnets and the rotor has no windings. These magnets concentrate all its flux linkage only on one axis as they are moulded as current source. The sum of resistive voltage drop is equal to the d and q axes stator voltage  Derivative of flux linkage with respect to windings : Vqs = Rs iqs + iqs d/dt Lqq + Lqq d/dt iqs + Lqd d/dt ids +ids d/dt Lqd + λaf d/dt sinθr.  Vds = Rs ids + iqs d/dt Lqd + Lqd d/dt diqs +Ldd d/dt ids + ids d/dt Ldd + λaf d/dt cosθr. Where  : vqs = voltage in q-axis winding                vds = voltage in d-axis winding                iqs = q-axis stator current                ids = d-axis stator current                Rs and Rd = resistance of q and d-axes. PMSM model in rotor reference :  Te=(3/2)(P/2)[λaf+(Ld-Lq)ir dr]ir qr (N.m)  : used to calculate electromagnetic torque. The above is  used to calculate mechanical speed of rotor. Block diagram of  Cascaded H-Bridge Multilevel Inverter Fed Pmsm

MODEL DESCRIPTION

There is only one file to execute : level7pdasm.slx The above simulation is the circuit diagram of PWM(pulse width modulation). The above simulation is of three stage seven level cascaded H-Bridge inverter of first phase. Note: simulink file or codes are saved in .slx format (Don’t worry if you don’t know the basics of the MATLAB Click here  to watch our video about MATLAB software basics)  (Click here  to download the zip file of the project)

Steps to Execute the Code

1. Download the zip file and unzip it
2. Open matlab and click on simulink icon on home tab
3. Click on open when the following window pops up 

4. A window pops up from which select the required file and click on open 5. Once the file is opened, click on run which is in the simulate tab. Once the simulation is ready click on scope to view the results.

Result

Issues Faced

1. Because of the version difference, functions might have changed and errors might occur so change functions according to the version(this simulation was done on R2022a).

Reference:

https://web.archive.org/web/20180409221922id_/http://www.ijritt.org/paper/IJRITTV3IS10001.pdf