Impact of large scale grid-connected wind generators on the power system network

In recent years, there has been a large increase in power demand without corresponding increase in power generation. With the issues around global warming, the use of renewable energy such as wind and solar has gained popularity. Renewable energy is clean, sustainable (will never run out), environmentally friendly. In addition, it requires a relatively low maintenance and running costs. Many countries are looking into integrating wind farms into their grids so as to reduce their carbon emissions, increase energy security and possibly create jobs. Although wind energy has many advantages, the integration of wind farms into the power grid may cause some problems due to the random nature of wind. Increasing penetration levels of wind power is expected to impact on the stability of the system, in particular voltage stability. Commonly used wind generator technologies are: Squirrel Cage Induction Generator (SCIG), Doubly-Fed Induction Generator (DFIG) and the Direct-Drive Synchronous Generator (DDSG). The SCIG is a fixed speed wind generator whilst the DFIG and DDSG are variable speed wind generators. This paper investigates the impact of large scale grid-connected wind generators on the power system network. It is shown that the voltage stability of the system depends to a large extend on the wind generator technology used. The SCIG wind turbines can reduce the system reactive power reserve margins. The higher the integration of the SCIG wind farm, the more the reactive power margins are reduced. Overall, the system is more vulnerable to voltage instability with SCIG wind farms. Variable speed wind generators on the other hand tend to have a better performance when connected to the grid. The integration of DFIG and/or DDSG greatly improves the reactive power margins of the system and thereby the voltage stability of the system.