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The penetration level of wind energy is continuously growing, and it is especially relevant in European countries such as Denmark, Germany, and Spain. For this reason, grid codes in different countries have been recently revised, or are now under revision in order to integrate this energy in the network taking into account the security of supply. This paper is related to reactive compensation, which is one aspect usually included in these codes. On the other hand, a great number of installed wind parks are formed by fixed speed wind turbines equipped with induction generators. The typical scheme for reactive compensation in this kind of wind parks is based on capacitor banks locally controlled in each machine. This configuration makes very difficult to follow the requirements of the new grid codes. To overcome this problem, a configuration with a central controller that coordinates the actuation over all the capacitor steps in the wind park is proposed in this paper. A central controller algorithm that is based on a dynamic programming is presented and evaluated by means of simulation. At this time, the proposed scheme has been installed at the Sotavento Experimental Wind Park (Spain) and it is currently being tested. [ABSTRACT FROM AUTHOR]

This two-part paper surveys the frequency and voltage control ancillary services in power systems from various parts of the world. In this first part, the nomenclature used to describe active power reserves across 11 systems is first reviewed in order to facilitate the comparison of frequency control ancillary services. The essential technical features of frequency and voltage control ancillary services are then described. Finally, the technical requirements adopted in eight jurisdictions (North America, continental Europe, Germany, France, Spain, the Netherlands, Belgium, and Great Britain) are compared. The companion paper surveys the economic features of these ancillary services. [ABSTRACT FROM AUTHOR]

The increasing installed wind power capacity has caused wind power generation to become a significant percentage of the entire electric power generation. As a consequence, the power system operators have included wind power plants regulation to improve the control of the overall power system, both in steady-state and transient operation. Therefore, wind power systems are required to verify the grid connection requirements stated by the power system operators. In presence of grid voltage dips, the low voltage ride-through (LVRT) requirement compliance produces a mismatch between the generated active power and the active power delivered to the grid. The conventional solution assumes that the active power surplus is dissipated in a dc-link resistor. In this paper, a control scheme for the back-to-back neutral-point-clamped converter is proposed. Under grid voltage dip, the controllers for generator-side and grid-side converters work concurrently to meet the LVRT requirement by storing the active power surplus in the turbine-generator mechanical system inertia while keeping constant the dc-link voltage. Simulation and experimental results verify the proposed control scheme. [ABSTRACT FROM PUBLISHER]

The expected growth of the number of electric vehicles can be challenging for planning and operating power systems. In this sense, distribution networks are considered the Achilles' heel of the process of adapting current power systems for a high presence of electric vehicles. This paper aims at deciding the maximum number of three-phase high-power charging points that can be installed in a low-voltage residential distribution grid. In order to increase the number of installed charging points, a mixed-integer formulation is proposed to model the provision of decentralized voltage support by electric vehicle chargers. This formulation is afterwards integrated into a modified AC optimal power flow formulation to characterize the steady-state operation of the distribution network during a given planning horizon. The performance of the proposed formulations have been tested in a case study based on the distribution network of La Graciosa island in Spain. [ABSTRACT FROM AUTHOR]