In modern power systems the generation and load composition are changing, and systems are moving towards their stability limits. In these systems more emphasis should be given to demand response (DR) related possibilities and alternatives when assessing network voltage and reactive power control management aspects. To perform adequate system studies and assess system performance it is of critical importance to model the system components in adequate manner. In this paper, load modelling aspects related to DR possibilities for voltage and reactive power control are discussed in detail. A reactive power-voltage (QV) analysis approach is proposed to determine the load's capability to provide voltage and reactive power support through DR during contingencies near nominal voltage levels. Different load modelling alternatives, i.e. static and dynamic load models, are covered together with detailed analysis on their influence and limitations regarding network voltage and reactive power control. It is shown that DR actions can be integrated into composite load models in a manner that enables the analysis of reactive power management and voltage control with existing network planning models. The results presented in this paper are relevant for network owners and system operators when deciding the needed level of details in their study models.

Smart Cities can benefit from existing municipal low voltage (LV) distribution grids by supporting public services with permanent power supply and providing grid connection points to distributed generators (DG). The increased integration of DGs and inverter based non-linear loads increases voltage quality issues, thus the cost-efficient assurance of voltage quality in LV grids with long radial lines is of increasing importance for the operators of municipal electricity distribution systems. Conventional methods for mitigating voltage quality issues (e.g., power line renovation) might not be optimal solutions either technologically or economically. Existing studies do not address all relevant issues related to the assurance of required voltage quality in such LV grids. This paper provides an overview of the applicability and rationality of traditional as well as alternative methods to solve voltage problems in LV grids. The authors use DIgSILENT PowerFactory software to simulate the performance of voltage stabilisers under different conditions. The authors propose a robust method for the classification of LV feeders and provide recommendations on how to resolve voltage quality problems, with the help of different power quality improvement devices, where the traditional methods of upgrading to medium voltage and grid reinforcement are economically infeasible. Based on our results, recommendations for mitigating voltage quality problems in LV distribution grids with radial lines of different lengths are given.

Ni-YSZ | YSZ | GDC | LSC single cells with different thickness of the electrodes have been prepared and studied at temperatures from 773 K to 1073 K. Single cells with high power density (~ 700 mWcm-2) and good time stability have been analyzed in detail using impedance spectroscopy data. Influence of the cathode thickness and synthesis temperature (i.e. porosity) on the rate limiting parameters has been demonstrated.