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CHAPTER 2: EXPERIMENTAL IMPLEMENTATION OF MATRIX CONVERTER DRIVE
V max
Output voltage
Modulation Index
V min
1.2
1
0.8
0.6
0.4
0.2
0
f min
Mod. index
Output Freq.
f
rated
Output frequency
Figure 2.8: V/f control technique
0 2 4 6 8 10
Time (s)
12 14 16 18 20 22 0
Figure 2.9: V/f implementation
To allow this an internal voltage reference has been created within the control code. To
control the voltage, the modulation index is slowly increased from 5% to the final value
of 70%, this happens during the first 10 seconds. The output frequency, instead, linearly
increases from 0 to 100Hz in the first 20 seconds. Fig. 2.9 shows the representation of
the speed and the modulation index during a run of the converter. The modulation
technique used is the Venturini optimized that allows, injecting a third harmonic, to
reach up to a maximum modulation index of 86.6%, rather than the 50% available with
the basic Venturini (Fig. 2.3b).
27
f max
120
100
80
60
40
20
Output frequency [Hz]