Simulation

Simulation#

Introduction#

It is possible to run a simulation on an entire watercourse in SHOP. When running a simulation, no constraints are taken into account. The model is neither run through the same validation functions as for optimization. The purpose is to return the physical response of the system given all user-controllable decisions as input. The SHOP simulator was first described in [32].

Input data#

Input of model and data is done using the same format as for optimization. For the simulation, most decisions that otherwise are made by the optimization must be given as schedules. Plants are operated based on input schedules. The following table sums up the possible schedule settings for each plant.

TXY attribute	Description
sim_gen_mw_flag	Use data from generator “production_schedule” attribute (in MW)
sim_gen_m3s_flag	Use data from generator “discharge_schedule” attribute (in m3/s)
sim_plant_mw_flag	Use data from plant “production_schedule” attribute (in MW). The production will be distributed in an optimal way for the best unit combination on the plant. The best unit combination is selected among those combinations that can be constructed by only adding or removing units from the combination that was used in the previous timestep.
sim_plant_m3s_flag	Use data from plant “discharge_schedule” attribute (in m3/s). The discharge will be distributed in an optimal way for the best unit combination on the plant. The best unit combination is selected among those combinations that can be constructed by only adding or removing units from the combination that was used in the previous timestep.
sim_reservoir_masl_flag	Use data from “masl_schedule” attribute (in m) for the reservoir directly above the plant. If the plant is below a junction or creek intake, this functionality cannot be used. Only the discharge of this plant and its bypass gate will be used to fulfil this schedule. If the discharge needed to keep the schedule is larger than the maximum capacity of the plant, it will use the bypass gate. The discharge in the plant will be distributed in an optimal way for the best unit combination on the plant. The best unit combination is selected among those combinations that can be constructed by only adding or removing units from the combination that was used in the previous timestep.

If several of the flags are set to 1 in the same timestep for the same plant, they will have the same priority order as in the table above. That is, sim_gen_mw_flag has the highest priority while sim_reservoir_masl_flag has the lowest priority. In addition, the following data is required as input to the simulation.

All standard gates and bypass gates must have schedules in m3/s.
All reservoirs must have start volume set.
All pumps must have committed status set.

If a schedule is missing on a plant or unit, but the simulation is started in the same session as an optimization, the result from the optimization will be used as schedule. Otherwise, the schedule will be set to 0. If a start reservoir is missing, it is set to 0.

Simulation rules#

If the decisions lead to situations that are physically infeasible or not adequately described by the input data the rules listed below are applied.

If there is discharge from an empty reservoir, the discharge remains unchanged and the reservoir remains empty. The artificial volume added is reported as a warning.
If there is inflow or discharge into a full reservoir without overflow possibilities, the discharge and inflow remains unchanged and the reservoir remains full. The artificial volume removed is reported as a warning.
If the schedule of a generator results in a flow below zero, the flow remains unchanged and the amount below zero is reported as a warning.
If the schedule of a generator results in a flow more than 20% above the maximum from the turbine efficiency curves, the flow remains unchanged and the amount maximum is reported as a warning.

Commands#

The commands listed in the table below are added to SHOP to interface the simulator. There are two main modes for reservoir simulation. Without any options set, the command “start shopsim” will calculate and output the storage trajectory of each reservoir. With the “/inflow”-option set, the command will calculate and output the inflow to each reservoir and creek intake needed to reproduce the input reservoir storage time series.

Command	Options	Comment
save optres_for_shopsim		Save generator schedule in MW, pump schedule in MW, gate schedule in m3/s to an ascii file that can be used as input data for simulation. Specify file name after the command.
start shopsim	/gen_mw_schedule, /gen_m3s_schedule, /plant_mw_schedule, /gen_m3s_schedule, /inflow	Run simulation. Default setting is /gen_mw_schedule. The schedule options are used on plants where no corresponding txy flag is set. See separate documentation for the inflow simulation option.
return shopsimres	/generator	Write results from simulation to ascii file.
save shopsimseries	/start, /end, /removeequal	Write results from simulation to ser file.
save xmlshopsimseries	/start, /end, /removeequal	Write results simulation to xml file.

Result data#

The simulator calculates the physical behaviour of the system given the input schedules, but also reports the economical value of the schedule.

Physical results#

The time series in the table below are returned as physical results from the simulation.

Object type	Attribute name	Data type	Comment
Reservoir	sim_storage	TXY	Start volume for each time step, length is number of time steps plus 1 to include end reservoir
Reservoir	sim_height	TXY	Reservoir height in masl volume for each time step, length is number of time steps plus 1 to include end reservoir
Plant	sim_discharge	TXY	Discharge in m3/s
Plant	sim_production	TXY	Production in MW
Generator	sim_discharge	TXY	Discharge in m3/s
Generator	sim_production	TXY	Production in MW
Pump	sim_upflow	TXY	Flow in m3/s (positive for upward flow)
Pump	sim_consumption	TXY	Consumption in MW
Gate	sim_discharge	TXY	Discharge in m3/s
Junction	sim_tunnel_flow_1	TXY	Flow through first input tunnel in m3/s
Junction	sim_tunnel_flow_2	TXY	Flow through second input tunnel in m3/s
Junction_gate	sim_tunnel_flow_1	TXY	Flow through first input tunnel in m3/s
Junction_gate	sim_tunnel_flow_2	TXY	Flow through second input tunnel in m3/s

Economical results#

As a post-processing operation after the simulation, the value of the simulated schedule is calculated. The table below summarizes the data provided by the calculation.

Object type	Attribute name	Data type	Description
Objective	sim_grand_total	double	Overall objective, calculated as the sum of sim_rsv_end_value plus sim_market_sale_buy minus sim_startup_costs minus sim_rsv_penalty
Objective	sim_rsv_end_value	double	Value of the simulated end storage of water in the reservoirs. The end valuation is done in the same way as in the optimization. If the endpoint_desc is given in €/MWh, it is converted based on the start reservoir and the best efficiency point of the plant. If cuts are used, water values from the most restrictive cut given the end volume of all reservoirs in the systems are used.
Objective	sim_vow_in_transit	double	Value of the simulated end storage of water in the reservoirs. The same water value is used as for the reservoir below.
Objective	sim_market_sale_buy	double	Market price times the simulated production and consumption for all units in the system.
Objective	sim_startup_costs	double	Startup and shutdown costs for all changes in production between 0 and any number larger than 1.0e-3 for all timesteps when mip_flag is activated for the plant.
Objective	sim_rsv_penalty	double	The sum of absolute values of artificially added and removed water from reservoirs in the simulation multiplied with the reservoir penalty cost used in the optimization.

Examples#

Examples available for simulation.