FACTS for wind power
When connecting wind farms to power grids, consideration needs to be given to the ability of the wind farm to produce energy while not impairing grid stability and reliability. As more and more wind farms are connected to the grid, transmission system operators are strengthening Grid Code requirements, specifically related to reactive power, voltage control, and fault ride-through capability. Wind farms often require dynamic reactive power compensation to comply with Grid Code requirements.
Ideally, wind farms should be connected to stiff grids in order not to influence stability or power quality in a detrimental way. This is usually not the case, however. Quite the contrary, wind power is usually connected far out in the grid, at sub-transmission or distribution levels, where the grid was not originally designed to transfer power from the system extremities back into the grid. Particularly when the grid is weak, unacceptable voltage gradients may occur. To keep system voltages within limits, FACTS is a powerful means.
FACTS is also useful as a means for increasing the power transmission capacity of existing grids, thereby aiding in congestion management and making room for additional power transfer from wind farms over existing grids.
When wind penetration increases to the point where it becomes a significant fraction of the load, added regulation is required for good grid stability control to compensate the fluctuations in generated wind power.
All in all, within wind power, there are applications for SVC, STATCOM and Series Compensation.
Sea cables: a key issue
For off-shore wind, comprehensive AC sea cable networks add another dimension, calling for additional elaborate reactive power control. The overall scope of reactive power control should encompass the wind farm just as well as the sea cables, to bring about a well regulated reactive power balance of the whole system, answering to the same demands on reactive power regulation as any other medium to large generator serving the grid.
FACTS for solar power
As prices of photo-voltaic cells plummet, solar power is becoming competitive in comparison with more traditional kinds of generation. Solar plants rated hundreds of MW are now a reality, and with grid codes demanding a certain percentage of reactive power contribution, compensating devices will be called for. This is where FACTS comes into the picture.