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an investigation of dual stator winding induction machines

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egulation capabilities <strong>of</strong> the controllers. The variations <strong>of</strong> the load resist<strong>an</strong>ce are given in<br />

Figure 9.9(q). Signific<strong>an</strong>t redistribution <strong>of</strong> active power from each <strong>stator</strong> <strong>winding</strong> set is<br />

m<strong>an</strong>ifested in the value <strong>of</strong> the electromagnetic torques. For ch<strong>an</strong>ges in load resist<strong>an</strong>ces,<br />

output dc voltage distribution coefficient (γ ) or rotor speed, the controlled dc voltage<br />

effectively tracks the comm<strong>an</strong>ds. The simulation results <strong>of</strong> the dynamic responses <strong>of</strong> the<br />

system to the ch<strong>an</strong>ging parameters, which are given in Figure 9.10, are used to check the<br />

robustness <strong>of</strong> the control scheme. The magnetizing induct<strong>an</strong>ces <strong>of</strong> both <strong>stator</strong> <strong>winding</strong><br />

sets are increased by 10% <strong>of</strong> their rated values while the rotor resist<strong>an</strong>ces increase by<br />

50% <strong>of</strong> their rated values as shown in Figure 8.7 (n, p <strong>an</strong>d q). During the variations <strong>of</strong> all<br />

these parameters, the output dc voltage is well regulated to be const<strong>an</strong>t. It is observed<br />

from the simulation results that the ch<strong>an</strong>ges <strong>of</strong> the rotor resist<strong>an</strong>ces <strong>of</strong> both <strong>winding</strong> set<br />

have bigger influences to the system th<strong>an</strong> those <strong>of</strong> the variation <strong>of</strong> magnetizing<br />

induct<strong>an</strong>ces, which c<strong>an</strong> be observed from the waveforms <strong>of</strong> the corresponding voltages.<br />

The proposed system <strong>an</strong>d its control scheme have been experimentally implemented<br />

using TMS320LF2407A DSP. Two voltage source inverters are serially connected while<br />

each <strong>of</strong> them feeds a <strong>stator</strong> <strong>winding</strong> set as shown in Figure 9.1. The <strong>dual</strong> <strong>winding</strong><br />

<strong>induction</strong> generator is coupled with a dc machine by the rotor shaft <strong>an</strong>d the dc machine is<br />

used to drive the generating system. At the beginning, the rotor speed <strong>of</strong> generator is<br />

fixed at 1600 rpm. Small initial voltages are supplied to the capacitors <strong>of</strong> the PWM<br />

rectifiers connected to the both <strong>winding</strong> sets. Then the DSP controller starts to send out<br />

the control PWM signals. The starting processes <strong>of</strong> the ABC <strong>an</strong>d XYZ <strong>winding</strong> sets are<br />

shown in Figure 9.11(a) <strong>an</strong>d (b) respectively. The dc voltages ramp from 0 to 200 V. The<br />

steady state waveforms <strong>of</strong> the generator <strong>winding</strong>s are shown in Figure 9.12 (a-b).<br />

333

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