Three questions about wind grid codes and power electronics
Power electronics devices can help wind farms address grid connection issues.
1) Why is there so much discussion around grid codes these days? Who writes them and enforces them?
As more utilities install wind and solar power on their network, the variability and fast growth rate of this renewable energy source requires coordinated connection procedures to ensure grid reliability.
Placing performance parameter requirements on voltage ride-through, active and reactive power, harmonics and frequency control will allow the wind farm to seamlessly connect to the grid without causing disruption on the power supply for the entire network.
While there is no unified grid code for wind in the United States, majority of the Independent System Operators or Regional Transmission Operator (RTO) as well as the regional regulators for utilities, have adopted their own grid codes that wind plants must adhere to in order to successfully be connect to the grid and be a contributor to the regions power supply.
2) If VArs are sometimes referred to as reactive or “imaginary” power, why do they matter?
Our electrical grid transports real or active power from the generation source to the load. During this process, reactive or “imaginary” power occurs as a result of the natural characteristics of the layout and components that make up the electrical grid. The real power does all of the work on the network and is responsible for powering your computers, iPads, TVs, appliances etc, and is measured in watts. The more reactive power on the network, the less real or active power can be delivered by the power lines. Therefore, managing the reactive power on transmission or distribution lines can help increase power flow and allow better use of the electrical infrastructure that is already in place. Without proper management of reactive power, voltage instability and collapse can occur, causing power disruptions, and in extreme cases, cause widespread outages.
Since the energy output from a wind farm is not always constant and cannot be predicted, the reactive power from the generators in the turbines, as well as the cables, the transformers, and other electrical components in the system, make it difficult to control the reactive power. This can lead to poor voltage regulation on the surrounding grid. Grid codes often specify the reactive power output or performance a wind farm must maintain in order to be safely connected to the grid.
3) What are the advantages for wind developers to look at advanced power electronics for connecting a wind farm?
As the energy output of wind farms is generally at the mercy of the availability of the wind, the variability of the power output can disrupt voltage stability and power flow, which not only causes power quality issues on the grid, but can also prevent wind farm developers and owners from maximizing the amount of energy they can sell on the grid.
By using advanced power electronics, wind farms can regulate their voltage and reactive power levels to make sure meet the interconnection requirements and help maintain grid reliability. Power electronic technology can be placed directly in the wind turbine with either DFIG or full conversion converters with control of active and reactive power happening in each individual wind turbine. However, depending on the location of the turbines relative to the collector system or the location of the wind farm itself, an advanced power electronic system may be needed at the point of interconnection in order to more precisely and accurately manage the voltage levels and reactive power for the entire system. This is where equipment such as STATCOMs have proven to be effective in managing the performance characteristics of wind farms.
Speak with me and other technology experts on May 5th in Las Vegas during a special half day educational seminar. Hosted by ABB, this technical training will take place in conjunction with AWEA Windpower. Topics include Statcom, Series Condensors, MicroGrids & connecting to the grid. Register now!