I have a problem with a simple transformer or with the flows connecting it with the bus it generates or the bus it consumes: if I put no lower bound on the in-/out-flow, the activity of the transformer is bigger than zero in a particular time-step (it consumes and produces some energy); but if I put a lower bound on the in-flow or out-flow - even much lower than the value it assumes without the bound - then, the solver cannot find any optimal solution!

There is an active upper bound on the same flow, however there shouldnâ€™t be any conflict between the two, because the upper bound is bigger than the lower one in any time-step (the max value is bigger than the min value and the capacity-in equals the capacity-out; efficiency is 1). Moreover, the problem exists also when I remove the upper bound.

I get the infeasibility with any range of time-steps I consider (actually I havenâ€™t tried all the combinations of the 8760 timesteps, itâ€™s my conclusion based on few combinations).

I tried to get some more information on the issue by adding a â€śshortageâ€ť transformer producing the same bus. The solver found a solution but the bus is produced only by the shortage transformer, even with a very high cost. It seems to me this particular transformer cannot work at all when there is a lower bound on its in-/out-flow.

I use the min and max bounds also on other flows/transformers, and they all work properly.

Furthermore, with om.pprint() I see that the flow is properly considered in the equations.

Am I missing anything? Has anyone experienced anything similar?

Iâ€™m using the â€ś*def nodes_from_excel(filename)*â€ť

Here is the interested portion of code:

[â€¦]

```
timeseries = xls.parse('time_series')
distributed_PV = xls.parse('distributed_PV')
for i, t in distributed_PV.iterrows():
noded[i] = solph.Transformer(
label=i,
inputs={
noded[t['from']]: solph.Flow(
nominal_value=t['capacity [MW]'])},
outputs={
noded[t['bus']]: solph.Flow(
nominal_value=t['capacity [MW]'],
min = timeseries[i],
max = timeseries['it_solar_pv_s_fix'])})
```

[â€¦]

the distributed_PV xls sheet content is as follows:

```
from bus capacity [MW]
it_PV_use it_bus_PV_use it_bus_el_t&d 10440
```

and the timeseries for the first three time-steps are:

it_PV_use

0.0752

0.0721

0.0676

it_solar_pv_s_fix

0.0100

0.0100

0.0100