# Synchronous Generator Stability Characterization for Gas Power Plants Using Load Rejection Tests
## 5 Conclusions  
This paper studies the characterization of power plants parameters from AVR and speed governor single tests under no-load conditions and a posterior load rejection test at reduced power in order to provide the synchronous generator (SG) parameters to the power system operator (PSO) with which simulates contingencies.  
Once given the registers of voltage and frequency variations from the on-site tests, the parameters' characterization is carried out in two stages:  
1. In the first step, the model is simulated under no-load conditions in order to change the controllers' set point (steady-state parameters) of the AVR and speed governor in an idle move.
2. In the second step, the load rejection simulations make it possible to find the transient controllers' parameters by fitting the parameters in an iterative process, in this case manually performed, in order to reach simulation curves similar to those measured in the experimental tests.  
Figure 11: Plant 1 simulation fittings: (**a**) no-load voltage set point changes; (**b**) no-load frequency set point changes; (**c**) load rejection test, voltage transient; (**d**) load rejection test, frequency transient.  
Figure 12: Plant 2 simulation fittings: (**a**) no-load voltage set point changes; (**b**) no-load frequency set point changes; (**c**) load rejection test, voltage transient; (**d**) load rejection test, frequency transient.  
Figure 13: Plant 3 simulation fittings: (**a**) no-load voltage set point changes; (**b**) no-load frequency set point changes; (**c**) load rejection test, voltage transient; (**d**) load rejection test, frequency transient.  
This paper presents some cases of a fieldwork carried out in more than 60 audited gas power plants, where the response of their controllers was studied. Some of them had problems with wrong controllers adjustments creating an instable system, while others did not have proper coordination in the generator protections, resulting in inappropriate disconnections from the network. For these reasons, these types of audits have high relevance for the power system reliability.  
In the audits shown in this paper, it must be noted that, at the fitting process, they did not fit well at steady-state after-transient parts of the simulation. The accuracy of a model depends on the level of detail required for the specific application. While the GENSAL model is a simplified model, it captures the essential behavior of synchronous generators and allows the PSO to perform contingencies simulations with admissible computational times. However, for more detailed analysis, more advanced models such as the [PERSON]'s model or the detailed electromagnetic transient model (EMT) could be used. The choice of model depends on the specific requirements of the analysis. On the other hand, advance fitting tools such as evolutionary algorithms should be used in further studies to perform the iterative parameters' fitting process.  
Conceptualization and methodology, A.M. and C.A.P.; software, A.M.; validation, J.M.G., K.M. and C.A.P.; formal analysis, K.M. and J.M.G.; writing--original draft preparation, A.M., J.M.G. and K.M.; writing--review and editing, J.M.G. and K.M.; supervision, C.A.P.; project administration, C.A.P. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. Not applicable. Not applicable. Not applicable. Not applicable. Not applicable. Not applicable.  
The authors declare no conflict of interest.