DYNAMIC BEHAVIOUR OF POWER SYSTEMS IN LARGE ISLANDS WITH HIGH WIND POWER PENETRATION N.D. Hatziargyriou 1 E.S.Karapidakis 1 D .Hatzifotis 2 Department of Electrical and Computer Engineering National Technical University of Athens Engineering & Construction of Transmission Projects Department Public Power Corporation 42, Patission Str., 106 82 Athens, Greece Tel. +301-7723661, Fax +301-7723659 22, Chalcocondyli Str., 10432 Athens, Greece Tel. +301-5292337, Fax +301-5236958 SUMMARY In this paper, the impact of high wind power penetration on the dynamic stability of power systems operating in large islands is investigated. The analysis of the power system of the largest Greek island, Crete, shows that it is possible to achieve a large wind power penetration without dynamic security problems, if conventional machines spinning reserve exists and the frequency and voltage control systems of the units have a sufficiently fast response. Keywords: Wind Generation, Isolated Power System, Dynamic Stability, Modeling, Simulation. 1.INTRODUCTION The installation of wind turbines (WT) in large islands, where the electric power is usually produced by gas and diesel units, presents considerable interest. This interest is increased when an important wind energy potential exists, which is usual in many islands. In these cases significant displacement of conventional fuels can be obtained by a high wind power penetration. Nevertheless, in this case it is important to ensure that the electric power system operation will not be disturbed, because of the connection of WTs to the system, [1]. The main problems being identified are related to system security, control of frequency and voltage and management of system generation reserve, [2]. The operation of wind generators in an isolated power system imposes technical constraints which must be considered, as increased wind penetration may seriously reduce the system operating security performance, [3]. These constraints determine a maximum permitted wind power penetration that depends on the load and the size of the conventional units. This maximum value can be increased if the wind generators are allowed to be controlled from the system control centre. In this paper, the dynamic behavior of isolated systems in large islands with thermal units and WTs is investigated using EUROSTAG software, [4]. This investigation aims to define operating rules for increasing wind power penetration in islands without deteriorating their dynamic security. This is one of the aims of CARE, an R&D program financed by the European Union. 2.PRESENTATION OF THE POWER SYSTEM The power system shown in Fig.1 is based on the power system of Crete which is the largest Greek island. It provides a good study case for illustrating the different operating features of large isolated systems and the security assessment studies that should be conducted. The main features of the system are the following: A. It is a purely thermal system that consists of 64 busbars, 20 generator (PV) buses, 11 wind power generator buses and 33 load (PQ) buses. The conventional generation system consists of two major power plants having eight groups of generating units. These plants are located near to the major load points of the island. A third plant (group) is considered to be installed in another area of the network to provide a better distribution of the power produced geographical. There are twenty generating units installed which are oil-fired units. Characteristics of the units are shown in Table 1. Table 1 Data of the system generating units No. of Machines Nominal Power (MW) Steam 6 103.5 Diesel 4 48 Gas 7 185 Comb.Cycle 1+2 132 W.T. 161 81.7 Total 181 550.2 B. The system peak load is equal to 360 MW while the active power losses have been calculated to be 4MW. This means that there is a reserve generating capacity of 104.5 MW which is about 29% of the system load demand and losses. The transmission network consists