Application of null space method in computing electricity prices with voltage-stability constraints

Nodal pricing is used in electricity markets around the world to facilitate the electricity trading among market participants. The nodal prices are computed by finding the shadow prices of the energy balance and branch constraints in the optimization problem at each node for each market period. The conventional approach to compute the nodal prices is by formulating a security-constrained economic dispatch using DC power flow equations, which ignore the voltage constraints. However, voltage-demand dependence at each electrical node is well studied in the area of voltage stability. In this paper, we first model the voltage constraints using the null space methodology. Then, we derive the voltage-price relationship at each node by deriving two different curves - voltage-demand curve, and price-demand curve - for each node of the system. This information on voltage-price relationship can be useful for better understanding of the economics of voltage support and also for pricing voltage regulation as a novel ancillary service.