Development of a Technique for Identification of Critical Locations for Maintaining Voltage Stability with Penetration of Wind Generation in Power Systems

International Journal of Electrical and Electronics Engineering |

© 2020 by SSRG - IJEEE Journal |

Volume 7 Issue 5 |

Year of Publication : 2020 |

Authors : Ganiyu Adedayo Ajenikoko, Lambe Mutalub Adesina, Olubunmi Adewale Akinola, Oluwadare Emmanuel Seluwa, Ayofe Ojeyinka Oluseyi, Joel Oyedele Olusola, Oluwasegun Adeyemi Adebiyi, Adebayo Wasiu Eboda |

##### How to Cite?

Ganiyu Adedayo Ajenikoko, Lambe Mutalub Adesina, Olubunmi Adewale Akinola, Oluwadare Emmanuel Seluwa, Ayofe Ojeyinka Oluseyi, Joel Oyedele Olusola, Oluwasegun Adeyemi Adebiyi, Adebayo Wasiu Eboda, "Development of a Technique for Identification of Critical Locations for Maintaining Voltage Stability with Penetration of Wind Generation in Power Systems," *SSRG International Journal of Electrical and Electronics Engineering*, vol. 7, no. 5, pp. 9-20, 2020. *Crossref,* https://doi.org/10.14445/23488379/IJEEE-V7I5P102

##### Abstract:

This paper discussed a technique for identification of critical locations for maintaining voltage stability with penetration of wind generation in power systems. When synchronous generation is displaced by wind, the loss of regulation capability have significant impacts, particularly on the voltage stability of the system, which will directly affect the rotor angle stability of the remaining convectional synchronous units present in the system. In this research paper, a small signal analysis was performed using appropriate mathematical notations. Some procedural steps were taken to identify critical locations for voltage stability. All existing and potential wind farms were modelled as full synchronous units, displacement of a single convectional generator existing in the system and re-examination of each mode identified from the previous step in great details. The process was repeated for the displacement of each of the existing synchronous units in the test system. Voltage stability analysis was carried out by subjecting a load bus in the system to a fault in order to determine the critical clearing times for each of the cases using the DSA tools software packages. Selected buses on the Nigerian 330 Kv grid system were displaced and active and reactive power flows were re-dispatched. The participation factors for the synchronous wind farms were computed.

The reactive power control from wind generation was utilized to control the bus voltages of transmission systems to improve the system voltage security when coupled with the variable and uncertain nature of the active power injections from wind generation. The under-excitation of the synchronous generator was greatly reduced by achieving balanced scheduled voltages at buses across the system,. The field voltage of the machine was improved and angular separation was minimized as a result of contingency occurrence. The rotor angle stability of the system was improved with an adequate maintenance of synchronism in the system. The results of this research paper showed that there were 28 participating wind farms on generator 33 while on generator 35, participating wind farms of 28, 26, 35 and 4 were recorded. Generators 26, 28, and 35 had significantly higher participation factors than the other wind farms and were therefore considered to be significant for the displacement of generator 28. In addition, 35 participating wind farms were recorded on generators 36 and 37 as a result of the configuration of the generators. Generators39, 40 and 41 recorded wind farms of 39, 4, 34, 28 and 26 with adequate participation. The same was computed for the displacement of each generator and the synchronous wind farms that displayed consistently high participation factors. There was no limit on the value of the participation factor, however for each system configuration; the value of each participating generator was compared to the others that were present. For generators 36 and 37, the participating factors were 0.08 and 0.04 respectively while for generator 39, participating factors of 0.13 and 0.06 were recorded on the same generator due to the configuration of the generator. The participating factor on generator 40 was 0.09 while the participating factor decreased from 0.08 to 0.06 on generator 41 due to the positional arrangement and configuration of generator 41.

After completing ten small-signal analyses, six farms presented consistently high average participation factors and were identified as critical farms. Buses 4, 26, 28, 34, 37 and 39 were noticeably higher in average participation factors compared to the other farms for each of the four scenarios and hence, were considered critical due to the fact that in the power flow dispatch on these farms had a significantly higher reactive power. Generators 26, 28, and 35 had significantly higher participation factors than the other wind farms and were therefore considered to be significant for the displacement of generator 28. The farm with the greatest capability to provide the system with reactive power had the largest participation factors for each of the scenarios regardless of active power flows and loading level driven by the network configuration and impedances.

The critical control case and the full control case were more secured as compared to the synchronous wind case due to the fact that the synchronism of the system was increased when there was lesser active power provided by the synchronous generation in the system. Thus, replacing synchronous generators with asynchronous wind farms increased the synchronous strength of the system and also, introducing wind generation increased the critical clearing times of the system. There was no significant difference between the critical control case and full control case, indicating that the stability of the system did not decrease as lesser control was applied by the wind generation. In addition, the critical clearing times were significantly lower at the lower penetration level as a result of larger percentage of the system’s active power provided by the synchronous generator. Hence, the system was more sensitive to application of a bus fault and the critical clearing time decreased at the 23.9% penetration level. Thus, the critical clearing times for the synchronous wind case, full control case and the critical control case were 15.03, 16.98 and 16.60 respectively.

By supporting the voltage at the identified critical locations with the aid of wind generators, the voltage stability and rotor angle stability can be maintained while minimizing the levels of control required by the system. This research paper has contributed to the continued secure and reliable operation required of a modern power system which will assist to achieve government targets to increase the sustainability levels of power systems.

##### Keywords:

Critical locations, Critical clearing times, Voltage stability, Wind generations, Reactive power, Active power, Rotor angles.

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