Dynamic Modes of a Brushless Doubly-Fed Generator for Wind Turbines

Wind turbines are nowadays very important for a significant contribution to the supply of electricity. Since the composition of such electrical networks includes generators of relatively low power, this leads to the need for parallel operation of several generators to satisfy large energy demands. To do this, it is necessary to control the voltage and frequency parameters at the output of generators, that is impossible in conventional synchronous generators with permanent magnets. The problem posed can be solved by using a doubly-fed machine as electric generator, which makes it possible to control the voltage and frequency parameters at the output of the electric generator, regardless of the rotation speed of the wind turbine shaft. In contrast to the currently used double conversion of electricity (rectification, inversion), in this case, it is not necessary to carry out the conversion of energy to the full power of the wind turbine. It is possible to reduce the power of the inverter and thereby increase the efficiency and reliability of the entire wind turbine. The load is connected to the stator winding of the generator, which gives a high quality of electricity supplied to the electrical network. The article also discusses the dynamic modes of a wind turbine with an electric generator based on a doubly-fed machine. The frequency dependencies for both leading and lagging modes of the shaft rotation speed, as a function of the nominal value, have also been obtained.