IEEE Electrification - December 2022 - 41

designed on an implicit assumption
of the aggregate load flexibility (or
response) from buildings. Therefore,
communication between the utility
and buildings is one way, i.e., prices
to devices, with no feedback from
the building loads to establish the
optimum price. Unlike " prices to
devices, " TCC is a two-way process;
i.e., it includes feedback between the
price and quantity. Because every
flexible load in a TCC process plays a
role in balancing the electricity supply and demand, the
price is a function of electricity quantity in the coordination
function. Other objectives besides the balancing
objective might affect electricity price as well. On the
consumption or demand side, quantity is a function of
the price and status of the controlled devices within a
building as well as other local conditions.
For illustrating the TCC concept, a distributed hierarchical
market structure is used (Figure 3). In this
approach, there is a market at the building level (shown
by the oval), the neighborhood level, and the distribution
level. In each of the markets, supply-and-demand
curves are balanced, and other constraints and objectives
are imposed. More details on the implementation
of a hierarchical market approach can be found in
Katipamula et al. (2019). In the TCC approach, the first
Unlike " prices to
devices, " TCC is a
two-way process; i.e.,
it includes feedback
between the price
and quantity.
step is to generate the price-capacity
(or flexibility) curve for each participating
DER. The price-capacity curve
expresses the inherent flexibility of
a device as a function of price, as
shown in Figure 4(b). The coordination
of hierarchical markets is critical
for reliable implementation,
including connectivity to external
sources. Because this article is
focused on the application of TCC to
buildings, we discuss only how the
demand curves are created and aggregated in a building
and used to support the TCC process.
Price-Capacity Curves
In a price-capacity curve, the x-axis represents the
capacity, and the y-axis represents the price. The capacity
bounds (q- and q+) are constructed as follows: the
system that this curve represents requires a certain minimum
power or energy to meet the service levels and is
willing to pay any price for it. For example, in a VAV airhandling
unit (AHU), this could represent the minimum
ventilation that the system must always provide to meet
the service levels. Likewise, there is a certain maximum
energy or power the system can consume, irrespective of
the price (even if the price is negative), to meet the service
levels. The minimum and maximum capacities
Goal
Prioritize Alternative Loads for Curtailment to Manage Demand
Criteria
Type of
Zone
Difference Between
the Zone Set Point and
Zone Temperature
Number of
Curtailments
Rate of
Change of the
Cooling Load
RTU
Power
Alternatives
RTU 1RTU 2RTU 3RTU 4RTU 5
Figure 2. An example of the analytic hierarchy process that uses RTU loads to manage the building peak demand.
IEEE Electrification Magazine / DECEMBER 2022
41

IEEE Electrification - December 2022

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