Smart grids instrumentation-obtaining subgrid impedance information

Abstract

Summary The paper deals with impedance measurements in smart grids. It presents the current state of the research in the field, with the information on methods and assured accuracy of grid impedance determination with the use of invasive methods. Associated problems and propositions for impedance observation infrastructure, which can be embedded in smart grid, are presented. Copyright © 2015 John Wiley & Sons, Ltd.

Methods of unbalanced voltage control in nonsolidly grounded systems based on current injection

“…Existing unbalanced voltage limiting methods are as follows: (1) line transpositions and bus phase transposing-the former is difficult to achieve and needs heavy workload, and the latter produces poor effect; (2) installing coupling capacitors-it cannot adapt to the systems with frequent structure changes, and it can even aggravate 3-phase voltage unbalances; and (3) deviating Petersen coil from the resonance point, or increasing the damping rate appropriatelythis method has limited effect because it can only reduce the amplification effect of Petersen coil. At present, more flexible and more effective methods to control the unbalanced voltage are desiderated in this field.…”

“…The smart distribution grids call for greater demands on power quality and safety performance, and in such cases, unbalanced voltage control (UVC) is an important aspect in future distribution network studies.…”