needle_combination#
A needle combination or isolated production zone of a generator with separate turbine efficiency curves. Can be used to model pelton turbines and other turbines with forbidden production zones
Input connections |
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Output connections |
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License |
SHOP_PELTON |
Release version |
13.0.0.a |
Introduction#
The needle_combination object in SHOP is used to model both Pelton turbines and generators with forbidden production and/or discharge zones. The SHOP_PELTON license is required to use the needle_combination object.
Pelton turbines#
When modelling a Pelton unit, the needle_combination represents the production and discharge characteristics of the unit when a specific combination of needles is controlling the flow of water through the nozzle. The attributes p_min, p_max, p_nom, and turb_eff_curves are specified on the needle_combination object to describe its operating range and efficiency. Defining multiple needle_combinations and then connecting them to a generator object will enable SHOP to choose which of the needle_combinations (if any) should be used to generate power in each hour.
Turbine with forbidden operating regions#
Other turbine types, such as Francis turbines, is usually modelled as having a continuous operating range between p_min and p_max in SHOP. However, some turbines may experience vibration or other unwanted behaviour when discharging water or producing power in a region within its operating range. These forbidden production and/or discharge regions can be modelled by using the needle_combination object. Having needle_combinations without overlap in production and/or discharge ranges will force SHOP to not operate in the forbidden region(s). This is shown in more detail in this example.
MIP#
Running SHOP without binary variables can lead to fractional commitment of generators and production below p_min. This problem can be more pronounced for generators modelled with needle_combinations, since it will be possible to fractionally operate on more than one needle_combination at the same time. The only way to ensure that this problem does not occur is to have an active mip_flag, which will force the optimization to pick only one needle_combination to operate on. Especially Pelton units delivering reserves may be “tempted” to operate a little bit on several needle_combinations to more easily deliver reserve capacity.
Input and output#
Most of the results for generators modelled with the use of needle_combinations are still found on the generator object, such as production and discharge. A few output attributes are still saved on the needle_combination object, which can be seen in the attribute table below. The same is true for the input attributes: all input generator attributes are still used for Pelton turbines, except for p_min, p_max, p_nom, and turb_eff_curves on the needle_combination object. Some attributes exist on both the generator and needle_combination, such as p_fcr_min (generator) and p_fcr_min (needle_combination). In these cases the needle_combination attribute is preferred over the generator attribute, but the generator attribute is still used if it is not present on the needle_combination.
Examples#
Attributes#
p_max#
Static maximum production for the needle combination. Unit: MW.
p_min#
Static minimum production for the needle combination. Unit: MW.
p_nom#
The nominal production that is the rated capacity of the needle combination, only used for droop calculations. Unit: MW.
turb_eff_curves#
The turbine efficiency curve(s) as a function of discharge through the turbine for this needle_combination. Several curves can be specified for different head levels (reference value in the XY) to make the efficiency head-dependent. Units: x: M3/S and y: %.
p_fcr_min#
Temporary minimum production allowed for the needle combination when delivering FCR. If this is not set, any p_fcr_min attribute defined on the generator object will be used instead. Note that the p_fcr_n_min and p_fcr_d_min attributes on the needle_combination will take precedence over this attribute if both are specified. Unit (y): MW.
p_fcr_n_min#
Temporary minimum production allowed for the needle combination when delivering FCR-N. If this attribute is not specified, the p_fcr_min attribute on the needle_combination object will be used instead. Unit (y): MW.
p_fcr_d_min#
Temporary minimum production allowed for the needle combination when delivering FCR-D. If this attribute is not specified, the p_fcr_min attribute on the needle_combination object will be used instead. Unit (y): MW.
p_fcr_max#
Temporary maximum production allowed for the needle combination when delivering FCR. If this is not set, any p_fcr_max attribute defined on the generator object will be used instead. Note that the p_fcr_n_max and p_fcr_d_max attributes on the needle_combination will take precedence over this attribute if both are specified. Unit (y): MW.
p_fcr_n_max#
Temporary maximum production allowed for the needle combination when delivering FCR-N. If this attribute is not specified, the p_fcr_max attribute on the needle_combination object will be used instead. Unit (y): MW.
p_fcr_d_max#
Temporary maximum production allowed for the needle combination when delivering FCR-D. If this attribute is not specified, the p_fcr_max attribute on the needle_combination object will be used instead. Unit (y): MW.
p_frr_min#
Minimum production allowed for the needle combination when delivering FRR. If not specified, the head-dependent minimum production for the needle combination is used as lower bound for downward FRR. Unit (y): MW.
p_frr_max#
Maximum production allowed for the needle combination when delivering FRR. If not specified, the head-dependent maximum production for the needle combination is used as upper bound for upward FRR. Unit (y): MW.
production_cost#
Production cost depending on the production of the needle combination. Units: x: MW and y: NOK/MW.
min_discharge#
Minimum discharge as a function of net head. Units: x: NO_UNIT and y: NO_UNIT.
max_discharge#
Maximum discharge as a function of net head. Units: x: NO_UNIT and y: NO_UNIT.
original_pq_curves#
Original PQ-curve for the needle combination that includes non-convex regions. Units: x: M3/S and y: MW.
convex_pq_curves#
Convexified PQ-curve for the needle combination that includes all the time-dependent operating limits and remove all the nonconcave points of the original PQ curve. The slope of each segment is non-increasing. Units: x: M3/S and y: MW.
final_pq_curves#
Final PQ curve for the needle combination that is the final form included into the MILP optimization problem. The first point of the convex PQ curve is extended to Q=0. Units: x: M3/S and y: MW.
max_prod#
The head dependent maximal production of the needle_combination, most accurate in incremental iterations. Unit (y): MW.
min_prod#
The head dependent minimal production of the needle_combination, most accurate in incremental iterations. Unit (y): MW.
solver_committed_fraction#
The value of the (relaxed) binary variable uesed to model the on/off status of the needle combination in full iterations. The value could be a fractional number between 0 (off) and 1 (on) if the unit commitment constraints are relaxed (mip_flag turned off). Unit (y): NO_UNIT.