Power Grid Controls Revisited
Key words: voltage and frequency control, price signal in a market context, stability, implementation
The electricity sector is moving from an integrated organisation (i.e., a framework in which production, transmission and distribution of the energy were ensured by a unique company) to a deregulated scheme in which the roles are ensured by several actors (several producers, transmission grids operators (TSO), traders, active consumers, … ) in a market – competitive - context. Several basic controls of the power system should be revisited to adapt to this new context.
The voltage and the frequency of a power system are maintained at specified levels (for security and economical purposes) by controls at several hierarchical levels: a secondary control level at transmission grid level provides references to be tracked by local controller implemented at each generator, called primary controllers.
Several principles of these controls should be revisited in the new context of the electricity sector mentioned above:
- the list of actuators used for the control should be defined on new bases. For example, the generators which participate to the secondary frequency control are no longer a priori imposed – as a so-called pro-rata participation – but they are selected according to price bids given by the generators to a market mechanism. This leads to a so-called merit-order list which evolves in time according to the prices and the state of the power system.
- the signals used for the secondary voltage control need a dedicated telecommunication system since they come from different locations of the transmission grid. Moreover, they are from both transmission and production parts which are no longer managed by the same entities in the new context of the electricity sector.
Research subject, general work plan:
Several levels of investigation are envisaged:
- which are the good mechanisms to choose the actuators? Which is the impact of this choice to the actual frequency control used in France? Which are the evolutions to propose?
- Which is the impact of a merit-order list on stability? How stability can be investigated and ensured in this context where commutations of the actuators take place?
- How the use of distant signals can be limited?
propose new controls
This work is proposed in a general framework of collaboration with RTE – the French Transmission System Operator – and it is thus connected to real needs of the interconnected power systems. Realistic tests and validations of the theoretic developments mentioned above are possible on grid models and scenarios provided by RTE. The Control of Power Grids chair which exists between Ecole Centrale Nantes and RTE R&D (http://chairerte.ec-nantes.fr/ ) guarantees the direction and the financial founding of this work. Several PhD subjects may be established for this general theme. The PhD work will be supervised in collaboration with specialists from Nantes and other research centres in France and abroad, according to the specificities of each subject.
The work will be carried out in Nantes-France.