Generator Formulate Non-convex
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Generator Formulate Non-convex

Units:-
Mode:Input Only
Multi-band:False
Default Value:1
Validation Rule:In (0,1,2)
Key Property:No
Description:Controls when integers are used to enforce clearing of marginal efficiency tranches in order.

Generator Formulate Non-convex controls when integers are used to enforce clearing of marginal efficiency tranches in order. The simulator will detect (but not correct) when there is an out of order dispatch of the fuel offtake variables an issue a warning. In order to force the order, a set of integer variables and constraints are required. This setting can take these values:

Auto (value = 1)
This option enables the non-convex formulation if any of the below options is detected:
  • Non-monotonically increasing (generator) or decreasing (load) incremental efficiency function is detected,
  • If hydro units define an efficiency curve,
  • If units participate in Waste Heat Markets.
Always (value = 2)
Convexity variables/constraints are added to the formulation regardless of whether or not the input appears convex.
Never (value = 0)
Convexity variables/constraints are not included in the formulation.

Settings other than 'Auto' supersede the Heat Rate Error Method setting in the Production object.

Potential uses of this setting are:

  1. Your hydro generator defines a multi-band Efficiency function but you know that integers are not required i.e. the water values imply that it is never 'optimal' to use more water than necessary to generate. In this case you can set Formulate Non-convex = "Never".
  2. You receive a warning stating the non-convex fuel is detected. In this case you can set Formulate Non-convex = "Always" to resolve the issue.

Non-convex dispatch is usually related to:

  1. Min Offtake, take-or-pay, Fuel obligations.
  2. CCGTs and Heat Loads: It might be less-expensive to (artificially) increase GT's consumption of fuel per unit of electricity in order to produce more wasted heat for the free-cost ST.
  3. Hydro units don't have costs, so the order is not even naturally expected. It may be better to use the most inefficient variables in order to release more water to a downstream location.

See also: