HYDRO SCHEDULING IN THE NETWORK POWER MODEL
The UPLAN suite of market modeling tools is uniquely
equipped for the complex task of evaluating the worth of hydro assets. The
built-in hydro-scheduler is unparalleled in the industry for its ability to use
the detailed representation of the multiple watersheds to capture the optimal
operating policy of hydro assets in competitive markets.
The data takes into account each plant in every river basin operating in a
region, as well as all the hydrological aspects of operation. The optimization
maximizes the overall generator profits from serving the demand for electric
energy with the available hydro and thermal generating resources, while
respecting all the hydrological, thermal, transmission and demand constraints of
the overall system. At the system level, the solution recognizes constraints
such as load curves at the various demand centers, transmission network
capabilities and reserve margins. At the individual generator level, the
solution incorporates factors such as the outage rates and outage duration.
Hydro Assets and Ancillary Service
Revenues
The strategic significance of
hydro assets is the capability to store energy. Storage allows for competitive
advantage through the tradeoff between offers made in the energy and ancillary
service markets, which can be submitted or withdrawn depending on the prevailing
prices during real-time. Storage plants make their bids based on the calculated
water value in the Energy market. In the Ancillary
Services market, the storage hydro can supply regulation in addition to spinning
and non-spinning reserve capacity. Indeed, a major benefit of a hydro asset is
the dominant position that this plant enjoys in the competitive market.
How the Hydro-Thermal Scheduler works with the UPLAN
The NPM is a structural market model with an advanced Optimal Power Flow (OPF)
program that solves the problems presented by the following inextricably linked
components: the power market, multi-area 
chronological production costing and transmission power flow. The objective of
the OPF is to maximize the combined value of the producers’ and consumers’
surplus based on offers, bids and reliability criteria, while accounting for the
network constraints and plant operational characteristics. The hydro-thermal
scheduling problem is set up to run over the planning horizon, solving one month
at a time. The schedule produced satisfies the supply and demand balance each
hour while determining the operation of the hydro resources over the whole month
in one step. The scheduler simultaneously evaluates each of the hydro plants as
an energy provider as well as an ancillary services provider. This ensures that
the interaction between the energy and ancillary service markets is captured,
and that the prices are free of arbitrage between the markets.
The optimization algorithm internally commits (SCUC) and dispatches (SCED) hydro
and traditional generators to develop the price and quantity of the hydro
dispatched. Users may choose to dispatch the hydro against the load or load net
of wind and minimize the total costs to the system. Alternatively, UPLAN
provides an option to dispatch hydro and pumped storage against price profile to
maximize the owner’s revenues.
Modeling the River Basin System
At system level, UPLAN coordinates the operation of the entire basin. In doing
so, it looks into the starting and ending reservoir level due to natural inflows
/outflows and hydro generation. The various system-related parameters and
constraints are presented below.
These are composed of rivers, streams, canals, and reservoirs. The discharge
from one reservoir may flow into a stream that flows into another reservoir
downstream. Streams and rivers within a common watershed must be recognized as
sharing runoff in a series of mutual flow transactions. Successful resource
management must account for the flow volumes between reservoirs in cascade, the
time delays involved in flow from upstream to downstream and reservoir storage
capacities.
The optimization
maximizes the overall generator profits from serving the demand for electric
energy with the available hydro and thermal generating resources, while
respecting all hydrological, thermal, transmission and demand constraints. The
hydro-thermal scheduling/dispatching model is set up to run over the planning
horizon, solving one month at a time. The scheduler simultaneously evaluates
each of the hydro plants as an energy provider as well as an ancillary services
provider.
- Plant capacity in MW
- Upstream and downstream flow
- Upstream and downstream flow constraints
- Minimum and maximum reservoir levels
- Minimum and maximum inflow and outflow
- Head height
- Spill
- Discharge
- Ancillary services revenues for regulation and spinning reserves
