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EEE_G545_91_C_2009_2 - L in series with a stray resistance...

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EEE G545 Control & Instrumentation of Power Electronic Systems Comprehensive Examination Marks: 40 (Open Book) Time: 3 hours ______________________________________________________________________________ 1. A three-phase AC to DC converter operates out of an AC source characterised by line voltage V ll , frequency ω 0 , and supply side per-phase inductance L c . The output terminal DC voltage may be assumed to be ripple-free (perhaps due to an appropriate L-C filter !), and is connected to a load of resistance R L . Relate the output DC voltage V o and per-phase fundamental frequency component of input current I i 1 so as to obtain the functions that relate geometric control equilibrium points for this system: a. For a fixed setting of firing angle α c . b. Independent of the firing angle. ...(10) 2. Consider the DC-DC converter shown in Fig. P2 , which can transfer power from V 1 to V 2 , or vice versa. Supoose in a practical setup, V 1 and V 2 are fixed, have source resistance r 1 and r 2 in series respectively, and the inductor has an inductance
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Unformatted text preview: L in series with a stray resistance r L . The duty cycle is defined as D , which represents the fraction of operating cycle time for which S 1 is gated; while (1 − D ) represents the fraction of time for which S 2 is gated. Identify the valid configurations, frame the configuration state equations, and hence the averaged state equations for the setup. Assume that the switches and diodes are ideal. ...(15) 3. Obtain a suitable incremental averaged model for the converter in Fig. P2 that can be suitably used for linear control. ...(5) 4. In the digital domain, a second order converter transfer function is found to have marginally stable complex conjugate poles in open loop, with no zeros. Show that if the converter control loop is closed through a positive feedback path, then it is possible to make the poles perfectly stable ...(10) EEE G545/10/Compre + V S S D D 1 1 2 2 1 + V 2 P2...
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