外文翻译---风电对电力系统角稳定性的影响(编辑修改稿)

外文翻译---风电对电力系统角稳定性的影响(编辑修改稿)内容摘要：

o preserve the system stability [2, 3]. There is no doubt that wind power will play a predominant role in adding clean and nonpolluting energy to the country’s grid. However, as more wind turbines are connected to the grid, their impact on the power quality of services populated with wind generation is being more evident, so it is important to analyze the transient stability of power system including wind power stations [4]. A threephase fault is applied to a 14 bus IEEE test system, and cleared by disconnecting the affected line. In this paper, the focus is limited to determine Critical Clearing Time (CCT) for the several cases by observing the transit behavior simulation of a test system during grid faults using a Matlab power system analyze toolbox (PSAT) [5]. The structure of this paper is as follows. First, the wind model is described briefly。 also the wind turbine concepts are described. Then, the test system and the applied models are presented. The oscillation of a group of generators during a fault is analyzed by observing the transient behavior for following cases: A Changing a wind source locates. B Different generator technologies. C Increasing gradually a rate of wind sources peration. To conclude, the results are clarified on the basis of existing theories and parison between different cases in order to choose a best case and avoid a worse one. Wind Model Wind energy is transformed into mechanical energy by means of a wind turbine whose rotation is transmitted to the generator by means of a mechanical drive train. The windpower equation [6, 7] is given by: Pt=1/8ρ π d2v3 Cp where ρ is the air density, r is the turbine radius, ν is the wind speed, and Cp is the turbine power coefficient which represents the power conversion efficiency and it is a function of the ratio of the rotor tipspeed to the wind speed, termed as the tipspeedratio (TSR). Such disturbances are the most mon in the grid, the grid disturbances considered in this paper are of short duration, maximum a few hundreds of milliseconds. Since the considered grid disturbances are much faster than wind speed variations, the wind speed can he assumed constant. Therefore, natural wind variations need not be taken into account. The wind speed is set to a constant 15 m/s. Turbine Models There are many different types of wind turbines in use around the world, each having its own list of benefits and drawbacks [8]. In this paper two main types of wind turbines are taken into account: • A constant speed wind turbine (Fig. 1a), which consists of a grid coupled shortcircuited induction generator [9]. The wind turbine rotor is connected to the generator through a gearbox. The power extracted from the wind is limited in high wind speeds using the stall effect. No active control systems are used. • A variable speed wind turbine with wound rotor induction generator (Fig. 1b) – doublyfed induction generator (DFIG). The rotor winding is supplied using a backtoback voltage source converter [10]. As in the first case, the wind turbine rotor is coupled to the generator through a gearbox. In high wind speeds the power extracted from the wind is limited by pitching the rotor blades. Figure 1a. Squirrel cage induction generator Figure 1b. Doublyfed induction generator Test System The test system for this study is presented in Fig. 2, it is derived from IEEE test system。 this work consists of 14 buses, 5 generators, 11 loads and 83 branches. The transformers connecting generators to the grid are adjusted accordingly. Wind turbines are the 2 MW machines described above in section 2. Note that the generators do not represent a single machine but a group of strongly coupled generators and for this test system the total power is divided as follow: Table 1. Active power of test system generators Generator N176。 1 2 3 4 5 Power(MW) 615 60 60 25 25 The disturbance investigated is a threephase shortcircuit on Bus number 2. This threephas。