**5. Conclusions**

In Figure 14, an example of over-response to this curtailment is presented for the 49.5-MW wind power plant discussed previously. The TSO set point was ordered during early morn‐ ing (03:00 to 07:00). When wind speed was above the cut-out wind speed (20 m/s), wind power decreased below the set point, reaching half generation and almost no generation.

**•** From 00:00 to 03:00, no curtailment was ordered. Most wind turbines were near or at 1 pu during this period. At 02:10, a slight wind power lull occurred as wind speed fell.

**•** From 03:00 to 04:40, a 0.6 pu TSO set point was applied. Then wind speed passed 20 m/s and most of the wind turbines were disconnected by cut-out speed protection. Wind pow‐ er plant production fell to 0.1 pu, much less than 0.6 pu. Then wind speed went down, and wind power plant production almost reached the TSO set point. Some wind turbines were maintained at maximum available power; whereas others were disconnected, result‐ ing in the TSO set point for the whole wind power plant. Some wind turbines were at maximum available power, and the rest remained disconnected. This kind of regulation

**•** From 04:40 to 07:40, the TSO set point changed from 0.6 pu to 0.5 pu. More wind turbines

**•** Finally, at 07:40, the TSO released the set point and the wind power plant recovered nor‐

This additional drop must be replaced by the generation reserves.

involves repeated connections and disconnections during curtailment.

**Figure 15.** Example of an over-response in a 49.5-MW wind power plant on January 1, 2010

The sequence of range of production was as follows:

were disconnected to achieve this change.

mal control.

300 Advances in Wind Power

There are different types of events in which wind power fluctuates significantly. In some cases, fluctuations are produced by variations of wind speed, especially during meteorologi‐ cal events such as storms. Other power fluctuations are not directly linked with wind behav‐ ior and have a technical cause related to power system operation issues.

In this chapter, examples of the different events affecting wind power fluctuations were shown.The behaviors and the responses of the Spanish power system and wind power plants experiencing such events were analyzed. Examples presented in this chapter show that some of the wind power integration issues are related to low-voltage ride-through. They are solved through strict grid code enforcement. Other solutions to manage the reserve power generation and the wind power fluctuations are also very important in order to ach‐ ieve high levels of wind power penetration. In the Spanish case, this could require increas‐ ing the availability of dispatchable and fast-start power plants, as well as increasing wind power plant participation on supporting the power system by providing voltage control, in‐ ertial emulation, frequency control, oscillation damping, or updated voltage ride-through capabilities.
