Running time according to level switching |
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Manual -> Energy Management System (EMS) -> Multi-level combined heat and power plants (CHPs) -> Time-dependent restrictions for CHPs -> Running time according to level switching |
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The minimum and maximum running time of CHPs must be set for each level. Instead of four times for a component (minimum switch-on time, minimum switch-off time, maximum switch-on time and maximum switch-off time) there are only two times - minimum and maximum running time per level - in order to describe a CHP with levels.
The minimum running time (switch-on time) of a level indicates how long the CHP has to run at the least on this level. After a level is reached, the optimization must wait at least this amount of time before a new set value input can be made for the next lower level.
The maximum running time of a level indicates how long a CHP is allowed to run on this level at the most. With the exception of the lowest level (nominal power), the CHP is switched to the next lower level after this time expires. At that a level counts as active even if the CHP actually runs on a higher level. The maximum running time of the individual levels must be attuned to other restrictions with regard to minimum running time and forewarning. Thus a timely switch to a lower level is possible. The optimization must also prevent set value inputs to a higher level when the maximum running time cannot be adhered to e.g. because of the minimum running time of the higher level.
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Manual switching can cause violations of the defined restrictions. These are intercepted by the EMS. |
For the lowest level (nominal level) the maximum running time has a different meaning than for the other levels. The maximum running time of the lowest level indicates how long a CHP is allowed to run on this level alone at the most. After that the CHP must be switched to the next higher level.
Example for the parameterization of the individual levels:
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Level |
0 |
1 |
2 |
3 |
4 |
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Output |
100 |
200 |
300 |
400 |
500 |
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minimum switch-on time (in seconds) |
-- |
60 |
60 |
60 |
60 |
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Forewarn time (in seconds) |
-- |
210 |
0 |
0 |
0 |
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Delay time for switch-on (in seconds) |
-- |
30 |
30 |
30 |
30 |
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Delay time for switch-off (in seconds) |
-- |
30 |
30 |
30 |
30 |
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Minimum value for the maximum switch-on time (in seconds) |
210 |
240 |
180 |
120 |
60 |
The times which must be entered in the parameterization for the switch-on and switch-off always refer to the level for which they are entered. This means that the switch-off time which is parameterized for one level is considered if a "switching" is carried out from this level to the next lower level. The switch-on time is considered if a "switching" is carried out from a lower level to this level.
As the lowest level represents the CHP running with nominal power, no information for minimal running time, forewarn time, delay time for switch-on and delay time for switch-off is necessary.
The minimal allowed values for the maximum switch-on times of each level are as follows:
Forewarn time of the next higher level
maximum/minimum switch-on time, forewarn time of the last level
maximum/minimum switch-on time, forewarn time of next higher level
+ delay time for switch-on for the next higher level
+ minimum value for the maximum switch-on time of the next higher level
+ forewarn time of the next higher level
+ delay time for switch-off for the next higher level
If for one CHP the maximum switch-on time for one level is below the calculated minimum value for the maximum switch-on time, the CHP is treated as not available and a corresponding availability identification is set for the readiness.
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