Data Format

1. Input Data Format

Instances are specified by JSON files containing the following main sections:

Each section is described in detail below. For a complete example, see case14.

1.1 Parameters

This section describes system-wide parameters, such as power balance penalties, and optimization parameters, such as the length of the planning horizon.

Key Description Default Time series?
Time (h) Length of the planning horizon (in hours) Required N
Power balance penalty ($/MW) Penalty for system-wide shortage or surplus in production (in $/MW). This is charged per time period. For example, if there is a shortage of 1 MW for three time periods, three times this amount will be charged. 1000.0 Y

Example

{
    "Parameters": {
        "Time (h)": 4,
        "Power balance penalty ($/MW)": 1000.0
    }
}

1.2 Buses

This section describes the characteristics of each bus in the system.

Key Description Default Time series?
Load (MW) Fixed load connected to the bus (in MW). Required Y

Example

{
    "Buses": {
        "b1": {
            "Load (MW)": 0.0
        },
        "b2": {
            "Load (MW)": [
                26.01527,
                24.46212,
                23.29725,
                22.90897
            ]
        }
    }
}

1.3 Generators

This section describes all generators in the system, including thermal units, renewable units and virtual units.

Key Description Default Time series?
Bus Identifier of the bus where this generator is located (string) Required N
Production cost curve (MW) and Production cost curve ($) Parameters describing the piecewise-linear production costs. See below for more details. Required Y
Startup costs ($) and Startup delays (h) Parameters describing how much it costs to start the generator after it has been shut down for a certain amount of time. If Startup costs ($) and Startup delays (h) are set to [300.0, 400.0] and [1, 4], for example, and the generator is shut down at time t, then it costs 300 to start up the generator at times t+1, t+2 or t+3, and 400 to start the generator at time t+4 or any time after that. The number of startup cost points is unlimited, and may be different for each generator. Startup delays must be strictly increasing. [0.0] and [1] N
Minimum uptime (h) Minimum amount of time the generator must stay operational after starting up (in hours). For example, if the generator starts up at time 1 and Minimum uptime (h) is set to 4, then the generator can only shut down at time 5. 1 N
Minimum downtime (h) Minimum amount of time the generator must stay offline after shutting down (in hours). For example, if the generator shuts down at time 1 and Minimum downtime (h) is set to 4, then the generator can only start producing power again at time 5. 1 N
Ramp up limit (MW) Maximum increase in production from one time period to the next (in MW). For example, if the generator is producing 100 MW at time 1 and if this parameter is set to 40 MW, then the generator will produce at most 140 MW at time 2. +inf N
Ramp down limit (MW) Maximum decrease in production from one time period to the next (in MW). For example, if the generator is producing 100 MW at time 1 and this parameter is set to 40 MW, then the generator will produce at least 60 MW at time 2. +inf N
Startup limit (MW) Maximum amount of power a generator can produce immediately after starting up (in MW). +inf N
Shutdown limit (MW) Maximum amount of power a generator can produce immediately before shutting down (in MW). Specifically, the generator can only shut down at time t+1 if its production at time t is below this limit. +inf N
Initial status (h) If set to a positive number, indicates the amount of time the generator has been on at the beginning of the simulation, and if set to a negative number, the amount of time the generator has been off. For example, if Initial status (h) is -2, this means that the generator was off at simulation time -2 and -1. The simulation starts at time 0. Required N
Initial power (MW) Amount of power the generator at time period -1, immediately before the planning horizon starts. Required N
Must run? If true, the generator should be committed, even that is not economical (Boolean). false Y
Provides spinning reserves? If true, this generator may provide spinning reserves (Boolean). true Y

Production costs and limits

Production costs are represented as piecewise-linear curves. Figure 1 shows an example cost curve with three segments, where it costs 1400, 1600, 2200 and 2400 dollars to generate, respectively, 100, 110, 130 and 135 MW of power. To model this generator, Production cost curve (MW) should be set to [100, 110, 130, 135], and Production cost curve ($) should be set to [1400, 1600, 2200, 2400]. Note that this curve also specifies the production limits. Specifically, the first point identifies the minimum power output when the unit is operational, while the last point identifies the maximum power output.

Figure 1. Piecewise-linear production cost curve.

Additional remarks:

Example

{
    "Generators": {
        "gen1": {
            "Bus": "b1",
            "Production cost curve (MW)": [100.0, 110.0, 130.0, 135.0],
            "Production cost curve ($)": [1400.0, 1600.0, 2200.0, 2400.0],
            "Startup costs ($)": [300.0, 400.0],
            "Startup delays (h)": [1, 4],
            "Ramp up limit (MW)": 232.68,
            "Ramp down limit (MW)": 232.68,
            "Startup limit (MW)": 232.68,
            "Shutdown limit (MW)": 232.68,
            "Minimum downtime (h)": 4,
            "Minimum uptime (h)": 4,
            "Initial status (h)": 12,
            "Must run?": false,
            "Provides spinning reserves?": true,
        },
        "gen2": {
            "Bus": "b5",
            "Production cost curve (MW)": [0.0, [10.0, 8.0, 0.0, 3.0]],
            "Production cost curve ($)": [0.0, 0.0],
            "Provides spinning reserves?": true,
        }
    }
}

1.4 Price-sensitive loads

This section describes components in the system which may increase or reduce their energy consumption according to the energy prices. Fixed loads (as described in the buses section) are always served, regardless of the price, unless there is significant congestion in the system or insufficient production capacity. Price-sensitive loads, on the other hand, are only served if it is economical to do so.

Key Description Default Time series?
Bus Bus where the load is located. Multiple price-sensitive loads may be placed at the same bus. Required N
Revenue ($/MW) Revenue obtained for serving each MW of power to this load. Required Y
Demand (MW) Maximum amount of power required by this load. Any amount lower than this may be served. Required Y

Example

{
    "Price-sensitive loads": {
        "p1": {
            "Bus": "b3",
            "Revenue ($/MW)": 23.0,
            "Demand (MW)": 50.0
        }
    }
}

1.5 Transmission Lines

This section describes the characteristics of transmission system, such as its topology and the susceptance of each transmission line.

Key Description Default Time series?
Source bus Identifier of the bus where the transmission line originates. Required N
Target bus Identifier of the bus where the transmission line reaches. Required N
Reactance (ohms) Reactance of the transmission line (in ohms). Required N
Susceptance (S) Susceptance of the transmission line (in siemens). Required N
Normal flow limit (MW) Maximum amount of power (in MW) allowed to flow through the line when the system is in its regular, fully-operational state. May be null is there is no limit. +inf Y
Emergency flow limit (MW) Maximum amount of power (in MW) allowed to flow through the line when the system is in degraded state (for example, after the failure of another transmission line). +inf Y
Flow limit penalty ($/MW) Penalty for violating the flow limits of the transmission line (in $/MW). This is charged per time period. For example, if there is a thermal violation of 1 MW for three time periods, three times this amount will be charged. 5000.0 Y

Example

{
    "Transmission lines": {
        "l1": {
            "Source bus": "b1",
            "Target bus": "b2",
            "Reactance (ohms)": 0.05917,
            "Susceptance (S)": 29.49686,
            "Normal flow limit (MW)": 15000.0,
            "Emergency flow limit (MW)": 20000.0,
            "Flow limit penalty ($/MW)": 5000.0
        }
    }
}

1.6 Reserves

This section describes the hourly amount of operating reserves required.

Key Description Default Time series?
Spinning (MW) Minimum amount of system-wide spinning reserves (in MW). Only generators which are online may provide this reserve. 0.0 Y

Example

{
    "Reserves": {
        "Spinning (MW)": [
            57.30552,
            53.88429,
            51.31838,
            50.46307
        ]
    }
}

1.7 Contingencies

This section describes credible contingency scenarios in the optimization, such as the loss of a transmission line or generator.

Key Description Default
Affected generators List of generators affected by this contingency. May be omitted if no generators are affected. []
Affected lines List of transmission lines affected by this contingency. May be omitted if no lines are affected. []

Example

{
    "Contingencies": {
        "c1": {
            "Affected lines": ["l1", "l2", "l3"],
            "Affected generators": ["g1"]
        },
        "c2": {
            "Affected lines": ["l4"]
        },
    }
}

1.8 Additional remarks

Time series parameters

Many numerical properties in the JSON file can be specified either as a single floating point number if they are time-independent, or as an array containing exactly T elements, where T is the length of the planning horizon, if they are time-dependent. For example, both formats below are valid when T=3:

{
    "Load (MW)": 800.0,
    "Load (MW)": [800.0, 850.0, 730.0]
}

Current limitations

2. Output Data Format

The output data format is also JSON-based, but it is not currently documented since we expect it to change significantly in a future version of the package.