Question

Consider a wind farm that is composed of 16 wind turbines arranged in strings of 4 wind turbines each. The voltage level of each wind turbine is 0.69 kV. The wind farm is connected to the medium voltage power system, at 60 kV. Q1: Assuming that the string voltage is 20 kV, and an ideal transformer, what is the turns ratio of the wind turbine transformer? Q2: Is the wind turbine transformer a step-down or step-up one? Why? Q3: What would be the string voltage if the (ideal) wind farm transformer has a turns-ratio of 0.55? Consider a power system with a high share of wind power. The time is early afternoon and there is a large production from wind turbines, covering around 60% of the consumption. A synchronous generator covers the rest of the consumption. Suddenly, due to a sudden drop in the wind speed, 1/3 of the wind turbines stop producing. Q1: Will the frequency increase or decrease? Why? Q2: From a stability perspective, what kind of disturbance would that be? Q3: What are the available options to restore the frequency to its nominal value?

Answer 1

- Given data total wind tur bives = 16 Each string have : 4 turbines village loved f each one = 0.696V voltage of power system a Goku Each string delivus 20kW, what is twin ratio :? 0.6980 0.6920 0.69kv soron heller 0.69xv a here all it wind tulbines and connected in series to get voltage sum, so = 4x moltage lend of each turbine - 4x0.69% € 9.76 KV

that means V, : 2.7 bkv apoi 20kV = V tram jumen Input a stning output = 2.76k V from home output : 2016 so twin ratio = Ny Vz 12 - 2.76k 2ok = 0.138 Q22 - wind turbine trous former is step-up because the output of stning is 2.76 kV but wе мүмiли 20kV сира уми each string .. so for that purpose we need to step-up the voltage from 2.76Xv to 20kV

- what about sharing voltage of turmations 0.550 the actual string output is 9.76kW V = 2.764V V ? the tunnadio = 0.155 2.76 k . 0.55 V = 5.01KV