Cooperative optimal power flow with flexible chemical process loads

Abstract

Power systems operations involve dispatching generation capacity and ancillary services as required to sustain reliable functioning of the electric grid. The dispatch schedules are determined by solving power flow calculations that incorporate models of the network components in real time as the power grid conditions change. Electricity intensive chemical processes can potentially provide grid support services and a closer coordination between process and grid operations can be beneficial. This cooperation is hindered by the lack of suitable process models, which appropriately protect process information. We propose a means to model the grid-relevant dynamics of chemical processes, and a framework for embedding such models in optimal power flow calculations. We present an extensive case study concerning cooperative demand-response operation for an electricity-intensive chemical process, chlor-alkali production. The results indicate significant flexibility and economic benefits both at the utility and at the end-user levels.

A decoupling strategy for protecting sensitive process information in cooperative optimization of power flow

“…Note that transmission constraints such as () are active per definition in congested grids. Our previous results 8 support the interpretation that the mismatch between assumed and implemented process demand visualized in Figure 1 that is present in the sequential approach is a drawback with significant economical impact in congested grids.…”

“…As a consequence, the cooperative OPF problem eliminates the mismatch between modeled and implemented process demand. Our previous results show 8 that the cooperative and the sequential approach are economically comparable in normal grid conditions. However, the cooperative approach can be superior to the sequential approach in congested grids because it can avoid load shedding and reduce congestion.…”

“…The cooperative OPF problem , developed in our previous work, 8 avoids sequencing by integrating the conventional OPF problem and the scheduling of industrial demand into a monolithic optimization problem in the integrated formulation. The demand of cooperating electricity users becomes a decision variable of the monolithic problem and can thus be incorporated both in the grid description as load and in the process model describing end‐user behavior.…”

“…However, the cooperative approach can be superior to the sequential approach in congested grids because it can avoid load shedding and reduce congestion. This can improve the economics of the grid and the resulting electricity prices tremendously 8 . Note that transmission constraints such as () are active per definition in congested grids.…”

“…Nevertheless, when grid operators act and decide separately from users, they cannot utilize the full potential of DSM in electrical power grids. In a recent article, Otashu et al have examined the effect of cooperative optimal power flow (OPF) calculations, in which grid operators are granted unrestricted access to the full operational flexibility of large industrial energy consumers to optimize the electrical energy transmission 8 . We will refer to this problem as integrated formulation of cooperative OPF problems.…”