【正文】 ement 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 8 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 expanded. This can be reached when: 1. the values of MSS XXR , and RX are reduced, 2. the value of the rotor resistance, R ,is increased. Graphically this is illustrated in case of increasing the rotor resistance value, R ,is increasing the rotor resistance value, R ,see . 9 Increasing the rotor resistance by the factor of 2, as in the example, leads to significant expanding of the critical windmill speed, C? , and the dynamic reactive pensation demands are reduced significantly. When the rotor resistance is .. 0 upRR ? , there will only be necessary to use 25MVAr dynamic reactive pensation The voltage in the wind farm connection point is shown in . The 25MVAr dynamic reactive pensation shall be pared with the reactive pensation demands in case of the rotor resistance value of 0R that are in Section 5 found to be 100MVAr. The dynamic reactive pensation demands are reduced significantly. On the other hand, this solution leads to increasing the power losses in the rotor circuit when the power system is in normal operation as well. Enforcing mechanical construction It is a mon opinion that when the inertia of the rotating system is higher, the more 10 stable operation is expected in the power system in postfault situations. In terms of the dynamic stability limit definition, the inertia value does not influence on the windmill critical speed. Two wind turbines with identical generator data and different inertia values 1MH and 2MH , where 21 MM HH ? , have the same critical speed values 21 CC ?? ? . Due to different inertia values, the wind turbines will, however, accelerate differently at the failure event and hence, have the different critical failure times 21 CC tt ? . Because of this, the heavy wind turbines show more stable behaviour pared with tinny wind turbines, as long as the failure time is not too long. In practical situations, the failure time is short enough and the heavy wind turbines will be preferred with respect to maintaining the voltage stability. Windmills are equipped with the shaft systems where the effective shaft stiffness viewed from the generator terminals is relatively low .In normal operation, there will be accumulated an amount of potential energy in the shafts and the lower the shaft stiffness is, the more the potential energy accumulated is .At a short circuit fault, the shafts are relaxing and the potential energy is disengaged into the generator rotor kiic energy. This results 11 in the more intensive acceleration of the generator rotor. The contribution to the generator rotor speed caused by the shaft relaxation is )/(2 GMG KHT??? .Increasing the shaft stiffness, K, leads, therefore, to the reduction of the windmill overspeeding at failure events, see , and hence, to the improvements of shortterm voltage stability, in accordance with the dynamic stability limit considerations. The simulation results dealing with dynamic reactive pensation demands at varying parameters of the windmill mechanical construction, MH andK ,are collected in Table 1. 12 Enforcement of the windmill mechanical c