ELECTRIC DRIVES CONVERTERS IN ELECTRIC DRIVE SYSTEMS MODULE 2 Dr. Nik Rumzi Nik Idris Dept. of Energy Conversion, UTM 2013

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 PI controller

Current-Controlled Converters Current need to be controlled (in drives): To control the torque To limit the current – protect the switching devices Motor Example of current control in cascade control structure converter speed controller position  + * 1/s current T* *   kT Kt

Current-Controlled Converters ON-OFF Controllers Separated PWM block Hysteresis Non-linear controllers PI controllers Linear controllers

Current-Controlled Converters PI-based (linear controller) Vdc Pulse width modulator vc iref PI +  q vtri Vdc q vc q Vdc Pulse width modulator vc

Current-Controlled Converters PI-based – extending to 3-phase i*a + PI PWM PWM Converter i*b + PI PWM PWM i*c + PI PWM PWM Sinusoidal PWM Motor Interactions between phases  only require 2 controllers Tracking error

Current-Controlled Converters PI-based Perform the 3-phase to 2-phase transformation - only two controllers (instead of 3) are used Perform the control in synchronous frame - the current will appear as DC Interactions between phases  only require 2 controllers Tracking error

Current-Controlled Converters PI-based i*a PWM + PI Converter i*b i*c Motor

Current-Controlled Converters PI-based i*a 3-2 PWM 2-3 PI Converter i*b i*c 3-2 Motor

Current-Controlled Converters PI-based PI controller dqabc (stationary stationary) abcdq (stationary  stationary) SVM or SPWM VSI IM va* vb* vc* ids iqs +  Ids* iqs*

Current-Controlled Converters PI-based PI controller dqabc (rotating stationary) abcdq (stationary  rotating) SVM or SPWM VSI IM va* vb* vc* ide iqe +  Ide* iqe* Synch speed estimator s

Current-Controlled Converters PI-based – simulation with control in stationary frame Simulink and SimPowerSystems References PI controllers Load 32 transformation VSI 32 transformation

Current-Controlled Converters PI-based – simulation with control in stationary frame d and q current components viewed in rotating frame ia as viewed in stationary frame

Current-Controlled Converters PI-based – simulation with control in synchronous frame Simulink and SimPowerSystems 14

Current-Controlled Converters PI-based - simulation with control in synchronous frame d and q current components viewed in rotating frame ia as viewed in stationary frame 15

Current-Controlled Converters Hysteresis-based + Vdc − ia ia + Va  iref va iref ierr q q ierr

Current-Controlled Converters Hysteresis-based - extending to 3-phase system Motor + i*a i*b i*c Converter

Current-Controlled Converters Hysteresis-based - extending to 3-phase system High bandwidth, simple implementation, insensitive to parameter variations Variable switching frequency – depending on operating conditions Instantaneous error for isolated neutral load can reach double the band For isolated neutral load, ia + ib + ic = 0 control is not totally independent h id iq is h

Current-Controlled Converters Hysteresis-based – simulink block VSI Load References Hysteresis comparators

Current-Controlled Converters Hysteresis-based – simulation results Current error Actual and reference currents Actual current locus

Current-Controlled Converters Hysteresis-based – simulation results 21