Requirement
For the construction project of the first ever wind farm in West Africa, Capsim was chosen to perform a study regarding the impact and the compatibility of a 25MW wind farm on the “Réseau National Interconnecté” (RNI – interconnected national grid) of Togo.
The main aim was to check whether the integration of the wind farm on the electrical grid was possible or not and also to define the necessary conditions for stability when the farm is connected. The substation to which the installation will be connected is managed by the national electrical grid company. This substation is also connected to the public electrical transmission grid managed by a neighbouring country operator.
Realization
This study is based on the modelling and simulation of the numerical model of a part of the interconnected grid between the 2 concerned countries. The study is focused on the main transport lines which could be impacted (modification of the power flow) and on the distribution network nearby the new wind farm.
The numerical model was built from the data provided by the electrical grid companies. The data consisted in one hand of elements of the network in its 2013 configuration and in the other hand the modification projects expected by 2015 regarding the commissioning of the future wind farm.
This model was then used for different study cases:
- A load flow study was performed using different normal configurations and contingencies (N-1 study). This case consists in calculating an initial state and then to simulate the loss of an important equipment in order to observe the consequences which can vary from a simple load flow alteration to a blackout. This consists of checking whether the voltage static criteria (overvoltage, extreme undervoltage) are exceeded and whether reinforcements are to be made.
- A transient stability study which consists in checking the dynamic behaviour of the electrical network during usual events (gusts and decrease in wind speed) or incidents (wind turbines disconnection due to tripping). Here; the objective is to identify situations in which the dynamic criteria regarding the voltage, frequency or the stability of generators are not respected
- A short-circuit study which aims to verify whether or not the equipment remain correctly sized despite the additional contribution of machines of the future wind farm in case of a fault
Results
This study allowed to :
- Perform a validation regarding the fact that the integration of the 25MW wind farm does not question the stability of the Interconnected National Grid
- Demonstrate that in case of islanded operation (no grid connection with neighbouring countries), limits of wind energy penetration levels are necessary in order to respect the allowed frequency variations during the greatest occuring transients (wind gust).
Model of the RNI du Togo, made under the ETAP software
