ELECTRIC DRIVES CONVERTERS IN ELECTRIC DRIVE SYSTEMS MODULE 2 Dr. Nik Rumzi Nik Idris Dept. of Energy Conversion, UTM 2006

CONVERTERS - Module 2 AC-DC controlled rectifier approximate model SIMULINK examples open-loop closed-loop Switch Mode DC-DC converter 2-Q and 4-Q converters Small signal modeling unipolar bipolar SIMULINK example Current-controlled for SM converters Bridge converter hysteresis fixed frequency 3-phase VSI hysteresis fixed frequency SVM-based Assignment 1

AC-DC controlled rectifier +Vo+Vo +Vo+Vo 90 o 180 o 90 o For steady state continuous current flow Average voltage over 10ms Average voltage over 3.33 ms 50Hz 1-phase 50Hz 3-phase 180 o  

AC-DC controlled rectifier firing circuit controlled rectifier  +Va–+Va– vcvc v a (s)v c (s) DC motor The relation between v c and v a is determined by the firing circuit ? It is desirable to have a linear relation between v c and v a

AC-DC controlled rectifier linear firing angle control Input voltage VmVm vtvt vcvc 0  22 33 44 Sawtooth compared with control signal Results of comparison to trigger SCRs Output voltage

AC-DC controlled rectifier linear firing angle control VmVm vtvt vcvc 0  22 33 44  vcvc   A non-linear relation between V a and v c

AC-DC controlled rectifier Cosine-wave crossing control VmVm vsvs vcvc 0  22 33 44 Input voltage Cosine wave compared with v c Results of comparison trigger SCRs Output voltage

AC-DC controlled rectifier Cosine-wave crossing control VmVm vsvs vcvc 0  22 33 44   V s cos(  t) V s cos(  ) = v c A linear relation between v c and V a

AC-DC controlled rectifier e.g. cosine wave crossing control

AC-DC controlled rectifier Control model V a is the average voltage over one period of the waveform - sampled data system Delays depending on when the control signal changes – normally taken as half of sampling period

AC-DC controlled rectifier Control model V a is the average voltage over one period of the waveform - sampled data system Delays depending on when the control signal changes – normally taken as half of sampling period

AC-DC controlled rectifier Control model v c (s)V a (s) Single phase, 50Hz T=10ms Three phase, 50Hz T=3.33ms Simplified if control bandwidth is reduced to much lower than the sampling frequency

AC-DC controlled rectifier SIMULINK EXAMPLES MATLAB v6.5, SIMULINK v5 SympPowerSystems toolbox Open-loop control Closed-loop control

AC-DC controlled rectifier Open loop firing circuit controlled rectifier  +Va–+Va– vcvc DC motor modeled with R-L and V dc

Three-phase AC source Controlled rectifier Load ‘Firing circuit’ scr_openloop_3phase.mdl

AC-DC controlled rectifier Closed loop firing circuit current controller controlled rectifier  +Va–+Va– vcvc i ref To control the current – current-controlled converter Torque can be controlled Only operates in Q1 and Q4 (single converter topology)

closed_loop_unipolar_4q_with_id.mdl Open-loop system from previous simulation Closed-loop elements