  The natural gas and electricity systems are now becoming more and more
strongly coupled. While gas-fired units (GFUs) are replacing the retired coal
plants, the power systems are also increasingly dependent on the flexibilities
provided by GFUs to accommodate intermittent renewable energies. The GFUs'
capability of power generation relies on the availability of gas resources,
which is determined jointly by the capacity of gas suppliers and their
associated pipeline networks. However, the gas and electricity markets are
operated separately. As a con-sequence, the GFUs actually have to "represent"
the whole power system to bid on the gas market: they need to make forecasts on
future gas consumption, and bear the risk of improper contracts or being unable
to meet the generation schedules due to insufficient gas supply. When facing
larger shares of renewable energies and more-frequent gas network congestion,
the current market framework is especially unreliable and inefficient, and also
economically unfriendly to the investors of the GFU assets. In this paper, we
try to develop a framework which can combine the two markets. By properly
pricing the scarce resources, e.g., gas transmission capacity, the joint market
can help allocate them more efficiently while satisfying the demands. And by
considering the uncertainty brought by renewable energies, a more
forward-looking day-ahead market clearing framework is presented. The
formulation, algorithm of the pro-posed joint market model will be presented,
as well as some case studies.
