JSON data format

An instance of the stochastic security-constrained unit commitment (SCUC) problem is composed multiple scenarios. Each scenario should be described in an individual JSON file containing the main section belows. For deterministic instances, a single scenario file, following the same format below, may also be provided. Fields that are allowed to differ among scenarios are marked as "uncertain". Fields that are allowed to be time-dependent are marked as "time series".

• Parameters
• Buses
• Generators
• Storage units
• Price-sensitive loads
• Transmission lines
• Reserves
• Contingencies

Each section is described in detail below. See case118/2017-01-01.json.gz for a complete example.

Parameters

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

Example

{
  "Parameters": {
    "Version": "0.4",
    "Time horizon (h)": 4,
    "Power balance penalty ($/MW)": 1000.0,
    "Scenario name": "s1",
    "Scenario weight": 0.5
  }
}

Buses

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

Example

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

Generators

This section describes all generators in the system. Two types of units can be specified:

• Thermal units: Units that produce power by converting heat into electrical energy, such as coal and oil power plants. These units use a more complex model, with binary decision variables, and various constraints to enforce ramp rates and minimum up/down time.
• Profiled units: Simplified model for units that do not require the constraints mentioned above, only a maximum and minimum power output for each time period. Typically used for renewables and hydro.

Thermal Units

Profiled Units

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 $2400 to generate, respectively, 100, 110, 130 and 135 MW of power. To model this generator, Production cost curve (MW) should be set to [100, 110, 130, 135], and Production cost curve ($) 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:

• For time-dependent production limits or time-dependent production costs, the usage of nested arrays is allowed. For example, if Production cost curve (MW) is set to [5.0, [10.0, 12.0, 15.0, 20.0]], then the unit may generate at most 10, 12, 15 and 20 MW of power during time steps 1, 2, 3 and 4, respectively. The minimum output for all time periods is fixed to at 5 MW.
• There is no limit to the number of piecewise-linear segments, and different generators may have a different number of segments.
• If Production cost curve (MW) and Production cost curve ($) both contain a single element, then the generator must produce exactly that amount of power when operational. To specify that the generator may produce any amount of power up to a certain limit P, the parameter Production cost curve (MW) should be set to [0, P].
• Production cost curves must be convex.

Example

{
  "Generators": {
    "gen1": {
      "Bus": "b1",
      "Type": "Thermal",
      "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,
      "Initial power (MW)": 115,
      "Must run?": false,
      "Reserve eligibility": ["r1"]
    },
    "gen2": {
      "Bus": "b5",
      "Type": "Thermal",
      "Production cost curve (MW)": [0.0, [10.0, 8.0, 0.0, 3.0]],
      "Production cost curve ($)": [0.0, 0.0],
      "Initial status (h)": -100,
      "Initial power (MW)": 0,
      "Reserve eligibility": ["r1", "r2"],
      "Commitment status": [true, false, null, true]
    },
    "gen3": {
      "Bus": "b6",
      "Type": "Profiled",
      "Minimum power (MW)": 10.0,
      "Maximum power (MW)": 120.0,
      "Cost ($/MW)": 100.0
    }
  }
}

Storage units

This section describes energy storage units in the system which charge and discharge power. The storage units consume power while charging, and generate power while discharging.

Example

{
  "Storage units": {
    "su1": {
      "Bus": "b2",
      "Maximum level (MWh)": 100.0,
      "Charge cost ($/MW)": 2.0,
      "Discharge cost ($/MW)": 2.5,
      "Maximum charge rate (MW)": 10.0,
      "Maximum discharge rate (MW)": 8.0
    },
    "su2": {
      "Bus": "b2",
      "Minimum level (MWh)": 10.0,
      "Maximum level (MWh)": 100.0,
      "Allow simultaneous charging and discharging": false,
      "Charge cost ($/MW)": 3.0,
      "Discharge cost ($/MW)": 3.5,
      "Charge efficiency": 0.8,
      "Discharge efficiency": 0.85,
      "Loss factor": 0.01,
      "Minimum charge rate (MW)": 5.0,
      "Maximum charge rate (MW)": 10.0,
      "Minimum discharge rate (MW)": 2.0,
      "Maximum discharge rate (MW)": 10.0,
      "Initial level (MWh)": 70.0,
      "Last period minimum level (MWh)": 80.0,
      "Last period maximum level (MWh)": 85.0
    },
    "su3": {
      "Bus": "b9",
      "Minimum level (MWh)": [10.0, 11.0, 12.0, 13.0],
      "Maximum level (MWh)": [100.0, 110.0, 120.0, 130.0],
      "Allow simultaneous charging and discharging": [false, false, true, true],
      "Charge cost ($/MW)": [2.0, 2.1, 2.2, 2.3],
      "Discharge cost ($/MW)": [1.0, 1.1, 1.2, 1.3],
      "Charge efficiency": [0.8, 0.81, 0.82, 0.82],
      "Discharge efficiency": [0.85, 0.86, 0.87, 0.88],
      "Loss factor": [0.01, 0.01, 0.02, 0.02],
      "Minimum charge rate (MW)": [5.0, 5.1, 5.2, 5.3],
      "Maximum charge rate (MW)": [10.0, 10.1, 10.2, 10.3],
      "Minimum discharge rate (MW)": [4.0, 4.1, 4.2, 4.3],
      "Maximum discharge rate (MW)": [8.0, 8.1, 8.2, 8.3],
      "Initial level (MWh)": 20.0,
      "Last period minimum level (MWh)": 21.0,
      "Last period maximum level (MWh)": 22.0
    }
  }
}

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.

Example

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

Transmission lines

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

Example

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

Reserves

This section describes the hourly amount of reserves required.

Example 1

{
  "Reserves": {
    "r1": {
      "Type": "spinning",
      "Amount (MW)": [57.30552, 53.88429, 51.31838, 50.46307],
      "Shortfall penalty ($/MW)": 5.0
    },
    "r2": {
      "Type": "flexiramp",
      "Amount (MW)": [20.31042, 23.65273, 27.41784, 25.34057]
    }
  }
}

Contingencies

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

Example

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

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, if they are time-dependent, where T is the number of time steps in the planning horizon. For example, both formats below are valid when T=3:

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

The value T depends on both Time horizon (h) and Time step (min), as the table below illustrates.

Current limitations

• Network topology must remain the same for all time periods.
• Only N-1 transmission contingencies are supported. Generator contingencies are not currently supported.
• Time-varying minimum production amounts are not currently compatible with ramp/startup/shutdown limits.
• Flexible ramping products can only be acquired under the WanHob2016 formulation, which does not support spinning reserves.
• The set of generators must be the same in all scenarios.