# On the Contribution of Wind Farms in Automatic Generation Control: Review and New Control Approach
## 3 Wind Farms Contribution in AGC
### BESS and FACTS Integration with Wind Farm  
The intermittent and unpredictable output power of wind farms may cause the use of supplementary source of energies in the power system to reach a more efficient frequency control and AGC contribution in the power system. Energy storage system is one of the important sources of energy that can be installed in wind integrated power systems to absorb and release the energy Integration of a real 34 MW battery storage system in a 51 MW wind farm in Japan is shown in Reference [62]. Frequency control is one of the important aims in utilizing this battery storage. As there are many types of energy storage technologies, the redox flow batteries (RFB), flywheels, capacitive energy storages and superconducting magnetic energy storages (SMES) have the most contribution for wind farms in the AGC based on the literature. Furthermore, there is high potential to improve the frequency control of multi-area power systems with FACTS devices, since they can control the tie-lines power. Regarding the mentioned features, energy storage systems and FACTS have the most contribution for wind farms to contribute in AGC of power systems. Integration of flywheel storage systems with wind farms was investigated in Reference [63]; in which the wind-flywheel system reduced the settling time and smoothed the frequency deviations more effectively. In Reference [64], it was shown that the application of SMES system in addition to dynamic active power support from wind farm is an impressive solution to improve the transient performance of the frequency after some disturbances. Coordinated design of AGC and redox flow batteries to minimize the frequency deviation in the wind integrated multi-area power system was demonstrated in Reference [65]. The aforementioned studies have investigated the sole integration of energy storage systems for wind farms in the AGC issue. However, application of energy storages in one area may not affect the frequency performance of other areas; as well application of energy storage for all areas is not an economical solution. Therefore, it is rational to use FACTS devices alongside wind-storage system to better control of tie-line power. The efficiency of such system was proven in Reference [66] by coordinated design of thyristor-controlled phase shifter (TCPS) and SMES system (in one area) incorporated with dynamic participation of wind farms in a deregulated two-area power system. Similar system was investigated in Reference [67] by applying the SMES system to each areas of the two-area power system. Such applications increase the cost of system, since the electromagnetic energy storage systems are still expensive. Furthermore, coordinate application of RFB with static synchronous series compensators (SSSC), and capacitive energy storage (CES) with TCPS, in wind integrated power systems for better contribution in the AGC were addressed by the studies [68; 69]. Furthermore, a detailed review of existing papers in Sections 3.1 and 3.2 is summarized in Table 1. Type of generation units contributed in the power systems, system configuration (energy storage and FACTS), control approach, and optimization techniques are addressed in Table 1. As shown, most of the studies are done in multi-area power system that demonstrates the capability of wind power to contribute to frequency control of large-scale power system.