On the evaluation of power quality indices in distribution systems with dispersed generation

Abstract

The increasing penetration of dispersed generation (DG) influences the power quality (PQ) levels in the distribution networks. Then, an accurate assessment of PQ disturbances in presence of DG is needed and adequate probabilistic indices should be adopted to properly quantify the random nature of the disturbances. In this paper, a tool for the calculation of slow voltage variations, waveform distortions, unbalances, voltage fluctuations and voltage sag probabilistic indices has been developed by using ® DigSilent Power Factory software. Numerical applications are performed on a 120-bus distribution network whose DG units are wind generators and gas turbine units.

Coordinated control of multi‐functional grid‐tied inverters using conductance and susceptance limitation

“…It should be noted that they include sinusoidal components because of the harmonic and unbalanced issues. According to (9) and (10), the total conductance and susceptance of the load can be expressed as (see (11)) where superscript '*' represents conjugate complex numbers, p and q are the instantaneous active and reactive power of the equivalent load. It should be noted that the instantaneous power can also be calculated in natural abc fame, which can be written as…”

“…In particular, the unreasonable trip-out accidents of grid-tied inverters caused by the harmonic resonances in series and/or parallel are frequently reported [6][7][8]. Besides, the power quality of the micro-grid will relate the on-grid electricity price of the micro-grid in the power quality market in the near future [9,10], and thus affect the economic operation of the micro-grid.…”