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Chun Kwong,<br>
You have to be a bit careful when using the Powell's Method solver to
make sure that the controller models that you are using (Type2, etc.)
are set up to accomodate that solver and are in the appropriate mode
for that solver. The idea of the Powell's Method solver is that if the
system that you are trying to control has very nearly no capacitance
(in other words no ability to store energy anywhere) then the system is
going to react so quickly to changes in controller output that the
Successive Substitution solver will not be able to converge. A good
example is a PV panel and a resistive load. If the thermal capacitance
of the PV panel is neglected then the combination of those two
components may have difficulty converging on an operating point. The
Powell's Method solver seeks to remedy the problem; my limited
understanding of it is that it wiggles the inputs to each component by
a little bit and it looks to see if the outputs wiggle a lot or a
little. If they wiggle only a little, the system is said to be stable
and converged. If they wiggle a lot, the solver tries to find a
different discrete control state that is a better solution. 99 times
out of 100, convergence problems in a successive substitution
simulation are the result of oversimplification of the system
(neglecting the piping, choosing models that have no thermal
capacitance, tolerances too loose, timestep too big) and will not
really be helped at all by switching to the Powell's Method controller.<br>
Kind regards,<br>
David<br>
<br>
<br>
<a class="moz-txt-link-abbreviated" href="mailto:a8304506@graduate.hku.hk">a8304506@graduate.hku.hk</a> wrote:
<blockquote cite="mid:1231762562.496b34829c63c@imp3.webmail.hku.hk"
type="cite">
<pre wrap="">Hello, Trnsys users.
I try to perform a simulation using the Powell's method for iteration, but with
errors "inconsistency in the input data" found for some components. However,
when I switch back to the successive method, there is no error. Do anyone know
how to rectify the problems? Your reply is appreciated. Thank you!
Best Regards
LEE, Chun Kwong
Research assistant
Division of Building Science and Technology
City University of Hong Kong
</pre>
<pre wrap="">
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