电力系统外文翻译付中文

电力系统外文翻译付中文内容摘要：

dmills Blade angle control is primarily used for optimization of the wind turbine mechanical power with respect to ining wind and hence, this control ability is not necessarily available at failure events in external power system with respect maintaining the shortterm voltage stability. This implies that the pitch or active stall wind turbines may operate as conventional (passive)stall wind turbines, by the same way as windmills onland, with the exception that they may not be disconnected. As the basis case with respect to the offshore wind turbine data, the rotor winding resistance upRR .  , the generator inertia sHG  ,the mill inertia sHM  , 6 and the shaft stiffness radelupK ./.. ,see Appendix A. If no dynamic reactive pensation is applied, a short circuit fault and a posefault line tripping will result in voltage instability, see . The windmills will be, then , tripped by the protective relays and power reserves of approx. 150 MW shall be found immediately. For voltage reestablishing after the short circuit fault, it will be necessary to use 100 MVAr of dynamic reactive pensation. The simulated curves for the voltages and speeds are given in . It is noticed that the wind turbine dynamic properties such as the voltage, the generator speed etc, show a fluctuating behaviour in the windmill drivetrain system. Despite the wind turbines have different initial setpoints, the windmills show a coherent response at the failure event in the external work so that the fluctuations are inphase and at the same frequency. The fluctuation frequency is the torsional mode of the windmill shafts. When the voltage is reestablished, fluctuations in any electrical or mechanical properties are no longer seen. There is no selfexcitation of the wind farm with a large number of wind turbines equipped with induction generators because the induction generators are passive systems in that no synchronizing torque and fast control have been applied. 7 6. Dynamic stability improvements within conventional technology The movement equation of a windmill in terms of the lumpedmass system is )(2)( GM EML HH TTdtd , (1a) Where MT and ET are the mechanical torque of the rotating mill and the electric torque, respectively, and L is the lumpedmass system speed ,GM GGMML HH HH   (1b) Where M and G are the mill mechanical speed and the electric speed of the generator, respectively, and MMM wPT )( at the given wind, w. The dynamic stability limit of the windmill is found from the movement equations (1a) 8 and (1b) as the speed L above the kipspeed where EM TT  . This solution is the critical speed of the windmill, C , so that exceeding the critical speed, CL   , leads to protective disconnection of windmills caused by overspeeding (prevention of voltage instability). Theoretical explanation for this definition can be found in Ref. and its graphical illustration is shown in . From the definition of the dynamic stability limit, a number of stability improvement methods can be introduced in terms of conventional windmill technology that are given in the following. . Generator parameters The shape of the electric torque versus speed curve, )( GET  , is influenced by the windmill induction generator parameters in accordance with )()( )()()( 222GTGTGTGGSGE XR RVT     (2)Where SV is the windmill generator terminal voltage as a function of the generator speed, and the machine impedance )()( GTGT jXR   with is given by the induction generator electrical parameters such as the stator resistance, SR , the stator reactance, SX , the magizing reactance, MX , the rotor resistance, R ,and the rotor reactance, RX , as given in Ref. The shortterm voltage stability will be always improved when the critical speed of the windmill is expande。