Direct Power and Torque Control of AC/DC/AC Converter-Fed ...

6. Simulation and Experimental Results
Fig. 6. 17. Experimental speed reversal from 71% to -71% of nominal speed. The proportional
gain K
PU
of DC-link voltage controller is 3.5 times higher then calculated; a) with active
power feedforward PF , b) with active power feedforward
PF
UI
.
Ω
From the top: DC-link voltage 100V/div, line current 10A/div, active 2.5kW/div and reactive 2.5kVar/div
power, mechanical speed of IM 1000rpm/div, stator current 10A/div, command and estimated torque 20
Nm/div. DC-link capacitor C=47uF
In Fig. 6. 16a,b waveforms for case with active power feedforwards
PF
Ω and
PF
UI
are presented. Shown speed reversal are from -53% to 53% of nominal speed
because DC-link voltage fluctuation for case PF
Ω
under transient +/- 71% of
nominal speed is too high. Only for higher proportional gain of DC-link controller
K
PU
equals to 3.5 times of the calculated value (based on Eq. (3.73)) the DC-link
voltage fluctuations are acceptable (see Fig. 6. 17). From Fig. 6. 17 can also be
concluded that
PF
UI
gives superior results then PF
Ω .
Further, for stressing the contrast between AC/DC/AC converter with VSR results
presented in Fig. 6. 15, Fig. 6. 16, and Fig. 6. 17 can be compared with results of
AC/DC/AC converter with diode rectifier shown in Fig. 6. 18.
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