Validation of Decentralized and Coordinated Operation of Frequency and Voltage Control Systems

As a part of ELECTRA IRP project, this PhD work will focus on development and validation of robust and coordinated control algorithm for frequency and voltage control. One of the actual research points is the virtual inertia which could be achieved by means of energy storage system or energy resources able to be deployed quickly in the system (e.g. electric vehicles). Different research studies concentrated on the implementation of virtual inertia control algorithms considering single or multiple units but in both cases has not been mentioned the limitation and /or consequence on the controller stability in function of the system inertia. Due to the fast variability of the energy resources mix (i.e. between renewable and traditional power plant) influencing the system inertia, the control algorithm need to be auto adapted to the network reconfiguration ensuring the controller optimization and the system stability. Moreover injecting active power in the distribution grid for frequency control (virtual inertia and/or primary control) could lead to local voltage deviation. Different studies focused on providing voltage and frequency control from the same unit acting on the active power but assuming a power grid with high inertia which limits frequency instability. Thus this study will take into account the impact of possible coupling between voltage and frequency controller due to the low system inertia which could lead to system instability.
Further the control architecture will be investigated according to the different control objective and time scale limitation. For example, on one hand the virtual inertia controller need to be fast enough to limit the rate of change of frequency implying the need of local automatic controller limiting communication delays. On the other hand the controller should to be accessed and modifiable by the operator in case of need (e.g. network reconfiguration).
This study will address the frequency and voltage control considering actual and new boundaries :
1) Ensure the state of the charge of the energy storage within high and low limits
2) Provide frequency and voltage control from the same unit considering low inertia in the system.
3) Coupling among different controllers
4) Investigate the different control architecture and the relative constraint (e.g. time scale, communication delay)