Search

This paper deals with an analytical model to evaluate the noncharacteristic harmonics that are generated by three-phase three-wire voltage-source converters (VSCs) operating under unbalanced sinusoidal voltage conditions. This model permits the calculation of the oscillating current on the VSC dc side by considering the unbalanced voltages on its ac side. It can be used to prove that the use of dc voltage control techniques to eliminate VSC dc-side double frequency voltage ripple necessarily creates three-phase currents with undesirable low-frequency harmonic components on the VSC ac side. In this paper, the attention is directed to the instantaneous oscillating real power component at twice the line frequency, rather than to other power components. The noncharacteristic current components analyzed in this paper, such as the fundamental negative sequence and third-order harmonic components of positive and negative sequences are calculated using the proposed model in time-domain simulations. A simple model to calculate the dc-side capacitor to mitigate these noncharacteristic harmonic problems is presented. [ABSTRACT FROM PUBLISHER]

SUMMARY Sensitivity analysis oriented by optimal power flow problem is applied in this work to estimate nodal technical losses in power transmission networks in a smart grid environment. This approach aims to efficiently provide active power loss indices as a result of load variations at each single load bus connected to the system. Unlike the power flow algorithm, this technique does not require an iterative process to find the solution, which results in a faster methodology with high accuracy and reduced computational cost, even when considering all the characteristics of the system. The methodology starts from a known optimal solution obtained by optimal power flow, considered as the base case. From the base case solution, new solutions can be evaluated by sensitivity analysis when system load bus perturbations occur. Tests were carried out on the IEEE 14 and 118 bus systems in order to evaluate the proposed technique performance. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]