DSP-based field oriented control of a load commutated current source inverter (LCCSI)-fed AC motor drive

In the power range of above 1 MW, industrial AC drive load-commutated current source inverters (LCCSI) are controlled by simple methods like the combination of V/f ratio constant control at low frequency and V/f ratio constant-angle control at high frequency. This gives a good steady-state but poor dynamic performance. This paper describes a drive control of LCCSI-fed induction motors which is based on the principle of field oriented control. Along with taking into account the output capacitor´s effect, the direct field oriented control referred to rotor flux fixed reference frame without a speed sensor is applied to decouple torque and flux generating currents and to overcome the problem of instability caused by the output capacitor. This control scheme is implemented by a 32 bit floating point Digital Signal Processor (DSP) chip-TMS320C30. The availability of this control scheme is verified by computer simulation and experimental results for a laboratory LCCSI-induction motor (10 HP) system.<>