Power System Grid Data Structure

The following sections detail the typical data structure for power system grids. This structure is largely based on the MATPOWER-FUBM model, which is an extended and modified version of the popular MATPOWER tool, designed to handle power flow and optimal power flow problems for AC, DC, and hybrid AC/DC power grids using the Flexible Universal Branch Model (FUBM).

Bus Data

This table contains information about each bus (node) in the power system:

• bus_i: Bus Number. A unique identifier for each bus in the system.
• type: Bus Type. Categorizes the bus based on its operational characteristics in a power flow study. Common types include:
  • 1: PQ bus (load bus - specified active and reactive power).
  • 2: PV bus (generator bus - specified active power and voltage magnitude).
  • 3: Slack bus (reference bus - specified voltage magnitude and angle, typically one per system).
  • 4: Isolated bus.
• Pd: Active Power Demand (MW). The real power consumed at the bus.
• Qd: Reactive Power Demand (MVAr). The reactive power consumed at the bus.
• Gs: Shunt Conductance (p.u.). The real part of the shunt admittance to ground at the bus, representing shunt resistance (e.g., losses in shunt reactors).
• Bs: Shunt Susceptance (p.u.). The imaginary part of the shunt admittance to ground at the bus, representing shunt capacitance (e.g., line charging or shunt capacitors/reactors).
• area: Area Number. The number of the control area to which the bus belongs. Power systems are often divided into control areas for operational purposes.
• Vm: Voltage Magnitude (p.u.). The per-unit voltage magnitude at the bus. This is an output of power flow studies for PQ buses and an input for PV and Slack buses.
• Va: Voltage Angle (degrees). The voltage angle in degrees at the bus. This is an output of power flow studies for PQ and PV buses and an input (usually 0) for the Slack bus.
• baseKV: Base Voltage (kV). The nominal voltage of the bus in kilovolts. This is crucial for converting per-unit values to actual values.
• zone: Zone Number. The number of the loss zone to which the bus belongs. Used for grouping buses for loss calculations or other regional analyses.
• Vmax: Maximum Voltage Magnitude (p.u.). The upper limit for the voltage magnitude at the bus, used in optimal power flow (OPF) studies.
• Vmin: Minimum Voltage Magnitude (p.u.). The lower limit for the voltage magnitude at the bus, used in optimal power flow (OPF) studies.
• Complexity_bus: Complexity Metric (Bus Model). Indicates the complexity of the model used for the bus, such as whether it's a dynamic or static representation.
• Complexity_load: Complexity Metric (Load Model). Indicates the complexity of the model used for the load connected to the bus, such as constant power load, constant current load, or constant impedance load.
• Complexity_bus_LF: Complexity Metric (Bus, Load Flow Model). Indicates the complexity of the bus model specifically used in load flow calculations.
• Complexity_load_LF: Complexity Metric (Load, Load Flow Model). Indicates the complexity of the load model specifically used in load flow calculations.

Line Data

This table describes the transmission lines connecting buses in the system:

• fbus: From Bus Number. The bus number at one end of the transmission line.
• tbus: To Bus Number. The bus number at the other end of the transmission line.
• r: Resistance (p.u.). The series resistance of the transmission line in per unit.
• x: Reactance (p.u.). The series reactance of the transmission line in per unit.
• b: Total Line Charging Susceptance (p.u.). The total shunt susceptance of the line, typically divided equally between the two ends. It represents the capacitive effect of the line.
• rateA: Long-Term Rating (MVA). The continuous thermal rating of the line in MVA.
• rateB: Short-Term Rating (MVA). The short-term (e.g., 2-hour) emergency thermal rating of the line in MVA.
• rateC: Emergency Rating (MVA). The emergency (e.g., 15-minute) thermal rating of the line in MVA.
• ratio: Transformer Tap Ratio (p.u.). For transformers, this is the off-nominal tap ratio of the transformer on the 'from' bus side. For lines, it's typically 1.0.
• angle: Transformer Phase Shift Angle (degrees). For phase-shifting transformers, this is the phase shift angle in degrees. For lines, it's typically 0.
• status: Line Status. Indicates whether the line is in service (1) or out of service (0).
• angmin: Minimum Voltage Angle Difference (degrees). The minimum allowed voltage angle difference across the line (fbus - tbus), used in OPF.
• angmax: Maximum Voltage Angle Difference (degrees). The maximum allowed voltage angle difference across the line (fbus - tbus), used in OPF.
• Complexity: Complexity Metric (Line Model). Indicates the complexity of the model used for the line, such as dynamic or static modeling.
• Complexity_LF: Complexity Metric (Line, Load Flow Model). Indicates the complexity of the line model specifically used in load flow calculations.

Generator Data

This table provides details for each generator connected to the buses:

• bus: Bus Number. The bus number to which the generator is connected.
• type: Generator Type. Can indicate the type of generator (e.g., synchronous, asynchronous) or its role in specific studies.
• Pg: Active Power Output (MW). The scheduled or actual active power output of the generator.
• Qg: Reactive Power Output (MVAr). The scheduled or actual reactive power output of the generator.
• Qmax: Maximum Reactive Power Output (MVAr). The upper limit for the reactive power output of the generator.
• Qmin: Minimum Reactive Power Output (MVAr). The lower limit for the reactive power output of the generator.
• Vg: Voltage Setpoint (p.u.). The voltage magnitude setpoint for the bus to which the generator is connected (applicable for PV and Slack buses).
• mBase: MVA Base of Generator (MVA). The machine base MVA of the generator, used for per-unit calculations specific to the generator.
• status: Generator Status. Indicates whether the generator is in service (1) or out of service (0).
• Pmax: Maximum Active Power Output (MW). The upper limit for the active power output of the generator.
• Pmin: Minimum Active Power Output (MW). The lower limit for the active power output of the generator.
• Pc1: Lower real power output of PQ capability curve (MW).
• Pc2: real power output of PQ capability curve (MW).
• Qc1min: Minimum Reactive Power Output at Pc1 (MVAr). The minimum reactive power output at Pc1.
• Qc1max: Maximum Reactive Power Output at Pc1 (MVAr). The maximum reactive power output at Pc1.
• Qc2min: Minimum Reactive Power Output at Pc2 (MVAr). The minimum reactive power output at Qc2.
• Qc2max: Maximum Reactive Power Output at Pc2 (MVAr). The maximum reactive power output at Qc2.
• ramp_agc: Ramp Rate for AGC (MW/min). The active power ramp rate for automatic generation control.
• ramp_10: Ramp Rate for 10-minute Reserve (MW/min). The active power ramp rate for 10-minute reserves.
• ramp_30: Ramp Rate for 30-minute Reserve (MW/min). The active power ramp rate for 30-minute reserves.
• ramp_q: Reactive Power Ramp Rate (MVAr/min). The reactive power ramp rate.
• apf: Area Participation Factor. The participation factor of the generator in an area's AGC response.

Interface-Converter Data

This table contains information specific to DC/AC interface-converters within the system (e.g., HVDC converters). The parameters often mirror those of transmission lines but include additional control variables:

• type: Converter Type. Specifies the type of inter-converter.
• fbus: From Bus Number. The bus number at the 'from' end of the converter.
• tbus: To Bus Number. The bus number at the 'to' end of the converter.
• r: Resistance (p.u.). The series resistance of the converter.
• x: Reactance (p.u.). The series reactance of the converter.
• b: Total Charging Susceptance (p.u.). The total shunt susceptance of the converter.
• rateA: Long-Term Rating (MVA). The continuous thermal rating of the converter.
• rateB: Short-Term Rating (MVA). The short-term emergency thermal rating.
• rateC: Emergency Rating (MVA). The emergency thermal rating.
• ratio: Tap Ratio (p.u.). The tap ratio of the converter transformer.
• angle: Phase Shift Angle (degrees). The phase shift angle of the converter transformer.
• status: Converter Status. Indicates whether the converter is in service (1) or out of service (0).
• angmin: Minimum Voltage Angle Difference (degrees). The minimum allowed voltage angle difference across the converter.
• angmax: Maximum Voltage Angle Difference (degrees). The maximum allowed voltage angle difference across the converter.
• PF: Active Power Flow From (MW). The active power flow to the 'from' side of the converter.
• QF: Reactive Power Flow From (MVAr). The reactive power flow to the 'from' side of the converter.
• PT: Active Power Flow To (MW). The active power flow to the 'to' side of the converter.
• QT: Reactive Power Flow To (MVAr). The reactive power flow to the 'to' side of the converter.
• MU_SF: Lagrangian Multiplier for From-Side Apparent Power Limit. Used in optimization for constraints related to apparent power on the 'from' side.
• MU_ST: Lagrangian Multiplier for To-Side Apparent Power Limit. Used in optimization for constraints related to apparent power on the 'to' side.
• MU_ANGMIN: Lagrangian Multiplier for Minimum Angle Difference. Used in optimization for angle difference constraints.
• MU_ANGMAX: Lagrangian Multiplier for Maximum Angle Difference. Used in optimization for angle difference constraints.
• VF_SET: Voltage Setpoint at From Bus (p.u.). The voltage magnitude setpoint for the 'from' bus.
• VT_SET: Voltage Setpoint at To Bus (p.u.). The voltage magnitude setpoint for the 'to' bus.
• TAP_MAX: Maximum Tap Ratio. The upper limit for the tap ratio of the converter transformer.
• TAP_MIN: Minimum Tap Ratio. The lower limit for the tap ratio of the converter transformer.
• CONV: Converter Control Mode. Indicates the control mode of the converter (e.g., voltage control, power factor control).
• BEQ: Equivalent Susceptance (p.u.). An equivalent susceptance parameter for the converter.
• K2: Control Parameter. A control parameter specific to the converter's operation.
• BEQ_MIN: Minimum Equivalent Susceptance (p.u.). The lower limit for BEQ.
• BEQ_MAX: Maximum Equivalent Susceptance (p.u.). The upper limit for BEQ.
• SH_MIN: Minimum Shunt Admittance (p.u.). Minimum value for shunt admittance if the converter includes variable shunt elements.
• SH_MAX: Maximum Shunt Admittance (p.u.). Maximum value for shunt admittance.
• GSW: Switching Conductance (p.u.). Represents switching losses or a conductance in the converter model.
• ALPHA1, ALPHA2, ALPHA3: Losses Coefficients. Constant, linear, and quadratic coefficients for losses in the converter model.
• Column37: (Unspecified). An additional column not used at the moment, possibly reserved for future use or specific model extensions.

System Parameters

This table defines overall system parameters:

• Area: Number of Area. The number of each area in the power system.
• Fb: Base Frequency (Hz). The nominal operating frequency of the power system area (e.g., 50 Hz or 60 Hz).
• Sb: Base MVA (MVA). The area base apparent power in MVA. All per-unit values in the system are typically based on this value.