Q:

Strong power systems have very small system impedances (e.g., R _syst = 0.001 ?, and X _syst = 0.005 ?) whereas weak power systems have fairly large system impedances (e.g., R _syst = 0.1 ?, and X _syst = 0.5 ?). Power quality problems are mostly associated with weak systems. Unfortunately, distributed generation (DG) inherently leads to weak systems because the source impedances of small generators are large, that is, they cannot supply a large current (ideally infinitely large) during transient operation. This application example studies the power-factor correction for a relatively weak power system where the difference between the displacement power factor and the total power factor is large due to the relatively large amplitudes of voltage and current harmonics.

1. Perform a PSpice analysis for the circuit of Fig. E5.1.1, where a three-phase thyristor rectifier fed by a Y/Y transformer with turns ratio ( N _p/ N _s = 1) via a filter (e.g., capacitor C _f) serves a load ( R _load). You may assume R _syst = 0.05 ?, X _syst = 0.1 ?, f = 60 Hz, , , and . Thyristors T ₁ to T ₆ can...