Hi! When my Hydroelectric station is not connected to a GRID (islanded mode) I control the frequency or the speed, and here are the equations for my turbine: http://oi46.tinypic.com/3127ixe.jpg Look the third equation. I built that in Matlab Simulink, and my out put is turbine speed n[o/min] http://oi48.tinypic.com/1zqc3o5.jpg That's all good. But now I want to make simulation model when my hydroelectric station is connected to the GRID. In that case I control the Power and my speed is constant, f=50Hz so n=const. So I need equations for that case, and If I look my third equation dw/dt=(1/J)*(Mv-Mtr-Mt) dw/dt=0(because speed is const) -> Mt=Mtr-Mv So my equation in this case is Mt=Mtr-Mv ? Mt is load torque and I think it should be my output if I want to control the power Mv- is Torque developed on turbine blades(Torque of water) Mtr - friction torque I just want to check am I right about this guys?