  We apply Coloured Petri Nets (CPNs) and the CPN Tools to develop a formal
model of an embedded system consisting of a power converter and an associated
controller. Matlab/Simulink is the de-facto tool for embedded control and
system design, but it relies on informal semantics and has limited support for
transparent and integrated specification and validation of both the power
converter electronics, controller (hardware), and the control logic (software).
The contribution of this paper is to develop a timed hierarchical CPN model
that mitigates the shortcomings of Simulink by relying on a Petri net
formalisation. We demonstrate the application of our approach by developing a
fully integrated model of a buck power converter with controller in CPN Tools.
Furthermore, we perform time-domain simulation to verify the capability of the
controller to serve the control objectives. To validate the developed CPN
model, we compare the simulation results obtained in an open-loop configuration
with a corresponding implementation in Simulink. The experimental results show
correspondence between the CPN model and the Simulink model. As our CPN model
reflects the fully integrated system, we are able to compare CPN simulation
results to measurements obtained with a corresponding implementation in real
hardware/software and compare closed-loop with open-loop configuration. The
results show alignment for the steady state while further refinement of the
control algorithm and validation is required.
