  A rapidly changing electricity sector requires adjusted and new ancillary
services, which enable the secure and reliable operation of the electricity
system. However, assessments and policy advice regarding ancillary services and
market design lack methods to evaluate the complex interaction of markets and
services. Therefore, this paper contributes an open-source agent-based model to
test design options for ancillary services and electricity markets. The
Ancillary Services Acquisition Model (ASAM) combines the agent-based modeling
framework MESA with the toolbox Python for Power System Analysis (PyPSA). The
model provides various design parameters per market and agent-specific
strategies as well as detailed clearing algorithms for the day-ahead market,
intra-day continuous trading, redispatch, and imbalances. Moreover, ASAM
includes numerous policy performance indicators, including a novel price
mark-up indicator and novel redispatch performance indicators. A stylized
simulation scenario verified and validated the model and addressed a redispatch
design question. The results displayed the following implications from order
types in redispatch markets with multi-period all-or-none design: (1) The order
design provides few risks for market parties, as orders are fully cleared. (2)
Large orders may lead to dispatch ramps before and after the delivery period
and may cause ramp-risk mark-ups as well as additional trading of imbalances on
intra-day. (3) All-or-none design in a liquid situation leads to the
over-procurement of redispatch by the grid operator, as orders cannot be
partially activated. Moreover, it is likely that the grid operator induces
imbalances to the system by incomplete redispatch activation (i.e. upward and
downward redispatch volumes are not equal).
