From GridLAB-D Wiki
Jump to: navigation, search

Overview

The diesel_dg object represents a synchronous distributed generation. The model supports both a QSTS-only model and subsecond (deltamode) modes of operation.

Properties

It is important to note that the parameter tables below represent variables that can be altered at the GLM level. With a few exceptions, all have a default value and do not need to be populated (but can be overridden with better values, if the user has them).

The properties are divided into the QSTS and subsecond sets. This mode of operation is determined by the Gen_type:

Table 1 - Mode Select
Property Type Unit Description
Gen_type enumeration none Selects the overall mode of operation for the diesel_dg object. Valid selections include:
  • CONSTANT_PQ - QSTS-only mode diesel generator
  • DYN_SYNCHRONOUS - QSTS and deltamode-compatible diesel generator

QSTS Mode

For QSTS mode, the follow properties are valid:

Table 2 - QSTS Parameters
Property Type Unit Description
Rated_VA double VA Nominal power rating of generator
power_out_A complex VA Scheduled output power of phase A
power_out_B complex VA Scheduled output power of phase B
power_out_C complex VA Scheduled output power of phase C
real_power_generation double W Total real/active power output
real_power_out_A double W Current real power output for phase A
real_power_out_B double W Current real power output for phase B
real_power_out_C double W Current real power output for phase C
reactive_power_generation double VAr Total reactive power output
reactive_power_out_A double VAr Current reactive power output for phase A
reactive_power_out_B double VAr Current reactive power output for phase B
reactive_power_out_C double VAr Current reactive power output for phase C

Deltamode

For deltamode-enabled simulations, the following variables are commonly available, or enable the specific controls detailed later:

Table 3 - Deltamode Base/Common Parameters
Property Type Unit Description
Rated_VA double VA Nominal power rating of generator
Rated_V double V Nominal line-to-line voltage rating. Will pull from attached parent, if not populated.
deltamode_only_changes bool N/A Dynamic equations are only initialized once, on the first QSTS-to-deltamode transition. Assumes all changes occur in deltamode.
current_out_A complex A Output current of phase A
current_out_B complex A Output current of phase B
current_out_C complex A Output current of phase C
power_out_A complex VA Output power of phase A
power_out_B complex VA Output power of phase B
power_out_C complex VA Output power of phase C
Convergence criteria variables
rotor_speed_convergence double rad/s Convergence criterion on rotor speed between deltamode timesteps - must be satisfied (if enabled) to return to QSTS
rotor_speed_convergence_enabled bool N/A Enables the checking of the rotor_speed_convergence variable
voltage_convergence double V Convergence criterion on terminal voltage magnitude between deltamode timesteps - must be satisfied (if enabled) to return to QSTS
voltage_magnitude_convergence_enabled bool N/A Enables the checking of the voltage_convergence variable
General governor variables
Governor_type enumeration N/A Selects the governor control model applied to the diesel generator. Valid options are:
  • NO_GOV - No governor
  • DEGOV1 - DEGOV1 Woodward Diesel Governor
  • GAST - GAST Gas Turbine Governor
  • GGOV1 - GGOV1 Governor Model
  • P_CONSTANT - P_CONSTANT mode Governor Model
P_f_droop_setting_mode enumeration N/A Defines what variable sets the bias/offset for the P-f droop curve (when enabled). Available choices are:
  • FSET_MODE - fset defines the curve offset/bias
  • PSET_MODE - Pset or Pref defines the curve offset/bias
General exciter variables
Exciter_type enumeration N/A Selects the exciter/AVR control model applied to the diesel generator. Valid options are:
  • NO_EXC - No exciter installed
  • SEXS - Simplified Excitation System installed
SEXS_mode enumeration N/A Selects the mode of operation for the simple exciter model. Valid options are:
  • CONSTANT_VOLTAGE - Maintains a voltage set point
  • CONSTANT_Q - Maintains a desired reactive power set point
  • Q_V_DROOP - Implements a Q-V droop functionality
General set-points/inputs for controls
wref double pu Reference/setpoint frequency for governor controls
w_ref double rad/s Reference/setpoint frequency for governor controls - takes priority over wref
vset double pu Input voltage set-point to AVR controls
Vset double pu Input voltage set-point to AVR controls - overloaded variable of vset
Pref double pu Input real power set point to governor controls
Pset double pu Input real power set point to governor controls - overloaded variable of Pref
fset double Hz Reference/setpoint frequency for governor controls - takes priority over wref
Qref double pu Input reactive power set point for AVR controls (when supported)

Note that individual categories below also each have their own variables. Not all of the input variables are accepted at all times -- certain ones are only enabled with specific control types (exciter or governor).

The power_out_A, power_out_B, and power_out_C variables are typically output variables. They can be an initial value for the start of the simulation, but if the diesel_dg object is attached to a SWING node, it will be initialized by the system powerflow.

Base Machine

The underlying synchronous machine dynamics are modeled as a subtransient round-rotor generator model. The unbalanced operation of three phase synchronous machines is modeled using a simplified fundamental frequency model in phasor representation according to [1, 2, 3, 4]. This simplification allows representing the machine in symmetrical components where the positive sequence represents the main electrical torque, and the negative sequence current produces a torque in opposition. The total electrical torque is constant, facilitating the solution and determination of equilibrium. However, the variation of electrical torque due to unbalanced operation reported in [5, 6] is ignored. In addition, typical assumptions for transient stability models are also made: ignoring sub-transient saliency, and neglecting the stator dynamics [7].

Parameters specific to the underlying machine model are:

Table 4 - Machine model parameters
Property Type Unit Description
Machine properties
Rated_VA double VA Nominal power rating of generator
overload_limit double pu per-unit value of the maximum power the generator can provide
omega_ref double rad/s Reference frequency of generator
inertia double s Inertial constant (H) of generator
damping double pu Damping constant (D) of generator
number_poles double N/A Number of poles in the generator (not currently supported)
Ra double pu Stator resistance
Xd double pu d-axis reactance
Xq double pu q-axis reactance
Xdp double pu d-axis transient reactance
Xqp double pu q-axis transient reactance
Xdpp double pu d-axis subtransient reactance
Xqpp double pu q-axis subtransient reactance
Xl double pu Leakage reactance
Tdp double s d-axis short circuit time constant
Tdop double s d-axis open circuit time constant
Tqop double s q-axis open circuit time constant
Tdopp double s d-axis open circuit subtransient time constant
Tqopp double s q-axis open circuit subtransient time constant
Ta double s Armature short-circuit time constant
X0 complex pu Zero sequence impedance
X2 complex pu Negative sequence impedance
State variables
rotor_angle double rad rotor angle state variable
rotor_speed double rad/s machine rotor speed state variable
field_voltage double pu machine field voltage state variable
flux1d double pu machine transient flux on d-axis state variable
flux2q double pu machine subtransient flux on q-axis state variable
EpRotated complex pu d-q rotated E-prime internal voltage state variable
VintRotated complex pu d-q rotated Vint voltage state variable
Eint_A complex V Unrotated, unsequenced phase A internal voltage
Eint_B complex V Unrotated, unsequenced phase B internal voltage
Eint_C complex V Unrotated, unsequenced phase C internal voltage
Irotated complex pu d-q rotated sequence current state variable
pwr_electric complex VA Current electrical output of machine
pwr_mech double W Current mechanical output of machine
torque_mech double N*m Current mechanical torque of machine
torque_elec double N*m Current electrical torque output of machine

Governor Models

To control the mechanical power and rotor speeds of the diesel_dg object, several governor types have been implemented. Note that most of these have roots in transmission-level models, though can work on distribution-level devices with appropriate parameters.

DEGOV1

The DEGOV1 governor represents a simple Woodward Diesel Governor model.

Parameters specific to the DEGOV1 model are:

Table 5 - DEGOV1 model parameters
Property Type Unit Description
Governor properties
DEGOV1_R double pu Governor droop constant
DEGOV1_T1 double s Governor electric control box time constant
DEGOV1_T2 double s Governor electric control box time constant
DEGOV1_T3 double s Governor electric control box time constant
DEGOV1_T4 double s Governor actuator time constant
DEGOV1_T5 double s Governor actuator time constant
DEGOV1_T6 double s Governor actuator time constant
DEGOV1_K double pu Governor actuator gain
DEGOV1_TMAX double pu Governor actuator upper limit
DEGOV1_TMIN double pu Governor actuator lower limit
DEGOV1_TD double s Governor combustion delay
State variables
DEGOV1_x1 double pu Governor electric box state variable
DEGOV1_x2 double pu Governor electric box state variable
DEGOV1_x4 double pu Governor electric box state variable
DEGOV1_x5 double pu Governor electric box state variable
DEGOV1_x6 double pu Governor electric box state variable
DEGOV1_throttle double pu Governor throttle state variable

GAST

The GAST governor represents a simple

Parameters specific to the GAST model are:

Table 6 - GAST model parameters
Property Type Unit Description
Governor properties
GAST_R double pu Governor droop constant
GAST_T1 double s Governor electric control box time constant
GAST_T2 double s Governor electric control box time constant
GAST_T3 double s Governor temperature limiter time constant
GAST_AT double s Governor Ambient Temperature load limit
GAST_KT double pu Governor temperature control loop gain
GAST_VMAX double pu Governor actuator upper limit
GAST_VMIN double pu Governor actuator lower limit
State variables
GAST_x1 double pu Governor electric box state variable
GAST_x2 double pu Governor electric box state variable
GAST_x3 double pu Governor electric box state variable
GAST_throttle double pu Governor throttle state variable

GGOV1

The GGOV1 governor models represent a combustion or combined cycle turbine governor, particularly one with an embedded PID control.

Parameters specific to the GGOV1 model are:

Table 7 - GGOV1 model parameters
Property Type Unit Description
Governor properties
GGOV1_Load_Limit_enable bool N/A Enables/disables load limiter (fsrt) of low-value-select
GGOV1_Acceleration_Limit_enable bool N/A Enables/disables acceleration limiter (fsra) of low-value-select
GGOV1_PID_enable bool N/A Enables/disables PID controller (fsrn) of low-value-select
GGOV1_Pset double pu GGOV1_Pset input to governor controls - overloaded with Pref
GGOV1_fset double Hz fset input to governor controls - overloaded with fset
GGOV1_R double pu Permanent droop
GGOV1_Rselect int32 N/A Feedback signal for droop. Options are:
  • 1 - selected electrical power
  • 0 - none (isochronous governor)
  • -1 - fuel valve stroke ( true stroke)
  • -2 - governor output ( requested stroke)
GGOV1_Tpelec double s Electrical power transducer time constant
GGOV1_maxerr double pu Maximum value for speed error signal
GGOV1_minerr double pu Minimum value for speed error signal
GGOV1_Kpgov double Governor proportional gain
GGOV1_Kigov double Governor integral gain
GGOV1_Kdgov double Governor derivative gain
GGOV1_Tdgov double s Governor derivative controller time constant
GGOV1_vmax double pu Maximum valve position limit
GGOV1_vmin double pu Minimum valve position limit
GGOV1_Tact double s Actuator time constant
GGOV1_Kturb double Turbine gain
GGOV1_wfnl double pu No load fuel flow
GGOV1_Tb double s Turbine lag time constant
GGOV1_Tc double s Turbine lead time constant
GGOV1_Fuel_lag int32 N/A Switch for fuel source characteristic. Options are:
  • 0 - fuel flow independent of speed
  • 1- fuel flow proportional to speed
GGOV1_Teng double s Transport lag time constant for diesel engine
GGOV1_Tfload double s Load Limiter time constant
GGOV1_Kpload double Load limiter proportional gain for PI controller
GGOV1_Kiload double Load limiter integral gain for PI controller
GGOV1_Ldref double pu Load limiter reference value
GGOV1_Dm double pu Speed sensitivity coefficient
GGOV1_ropen double pu/s Maximum valve opening rate
GGOV1_rclose double pu/s Minimum valve closing rate
GGOV1_Kimw double Power controller (reset) gain
GGOV1_Pmwset double MW Power controller setpoint
GGOV1_aset double pu/s Acceleration limiter setpoint
GGOV1_Ka double Acceleration limiter Gain
GGOV1_Ta double s Acceleration limiter time constant
GGOV1_db double Speed governor dead band
GGOV1_Tsa double s Temperature detection lead time constant
GGOV1_Tsb double s Temperature detection lag time constant
State variables
GGOV1_fsrt double Load limiter block input to low-value-select
GGOV1_fsra double Acceleration limiter block input to low-value-select
GGOV1_fsrn double PID block input to low-value-select
GGOV1_speed_error double pu Speed difference in per-unit for input to PID controller
GGOV1_x1 double Unlabeled state variable
GGOV1_x2 double Unlabeled state variable
GGOV1_x2a double Unlabeled state variable
GGOV1_x3 double Unlabeled state variable
GGOV1_x3a double Unlabeled state variable
GGOV1_x4 double Unlabeled state variable
GGOV1_x4a double Unlabeled state variable
GGOV1_x4b double Unlabeled state variable
GGOV1_x5 double Unlabeled state variable
GGOV1_x5a double Unlabeled state variable
GGOV1_x5b double Unlabeled state variable
GGOV1_x6 double Unlabeled state variable
GGOV1_x7 double Unlabeled state variable
GGOV1_x7a double Unlabeled state variable
GGOV1_x8 double Unlabeled state variable
GGOV1_x8a double Unlabeled state variable
GGOV1_x9 double Unlabeled state variable
GGOV1_x9a double Unlabeled state variable
GGOV1_x10 double Unlabeled state variable
GGOV1_x10a double Unlabeled state variable
GGOV1_x10b double Unlabeled state variable
GGOV1_ValveStroke double Unlabeled state variable
GGOV1_FuelFlow double Unlabeled state variable
GGOV1_GovOutPut double Unlabeled state variable
GGOV1_RselectValue double Unlabeled state variable
GGOV1_fsrtNoLim double Unlabeled state variable
GGOV1_err2 double Unlabeled state variable
GGOV1_err2a double Unlabeled state variable
GGOV1_err3 double Unlabeled state variable
GGOV1_err4 double Unlabeled state variable
GGOV1_err7 double Unlabeled state variable
GGOV1_LowValSelect1 double Unlabeled state variable
GGOV1_LowValSelect double Unlabeled state variable

P_CONSTANT

The P_CONSTANT governor model represents a governor to dispatch a desired real power value into the grid. It is built off a modified version of a typical DEGOV1 governor.

Parameters specific to the P_CONSTANT model are:

Table 8 - P_CONSTANT model parameters
Property Type Unit Description
Governor properties
P_CONSTANT_Pref double pu Pref input to governor controls - overloaded with Pref
P_CONSTANT_ki double pu parameter of the integration control for constant P mode
P_CONSTANT_kp double pu parameter of the proportional control for constant P mode
P_CONSTANT_Tpelec double s Electrical power transducer time constant
P_CONSTANT_Tact double s Actuator time constant
P_CONSTANT_Kturb double pu Turbine gain
P_CONSTANT_wfnl double pu No load fuel flow
P_CONSTANT_Tb double s Turbine lag time constant
P_CONSTANT_Tc double s Turbine lead time constant
P_CONSTANT_Teng double s Transport lag time constant for diesel engine
P_CONSTANT_ropen double pu/s Maximum valve opening rate
P_CONSTANT_rclose double pu/s Minimum valve closing rate
State variables
P_CONSTANT_x1 double pu Governor electric box state variable
P_CONSTANT_x4 double pu Governor electric box state variable
P_CONSTANT_x4a double pu Governor electric box state variable
P_CONSTANT_x4b double pu Governor electric box state variable
P_CONSTANT_x5 double pu Governor electric box state variable
P_CONSTANT_x5a double pu Governor electric box state variable
P_CONSTANT_x5b double pu Governor electric box state variable
P_CONSTANT_x_Pconstant double pu Initial bias/power offset - for delta controls
P_CONSTANT_err4 double pu Error between desired governor output and current output
P_CONSTANT_ValveStroke double pu Governor throttle position
P_CONSTANT_FuelFlow double pu Governor fuel consumption value
P_CONSTANT_GovOutPut double pu Current mechanical power output

Exciter Models

Output voltage/reactive power on the diesel_dg object is controlled via a simple exciter (SEXS) model. Unlike the governor controls, with distinct governor operations for each model, all voltage/reactive power modes are built on top of the simple exciter. As such, the parameters below are generally utilized by every operating mode listed in this section.

Parameters specific to the SEXS model are:

Table 9 - SEXS model parameters
Property Type Unit Description
Exciter properties
KA double pu Exciter gain
TA double s Exciter time constant
TB double s Exciter transient gain reduction time constant
TC double s Exciter transient gain reduction time constant
EMAX double pu Exciter upper limit
EMIN double pu Exciter lower limit
State variables
bias double pu Exciter bias state variable
xe double pu Exciter state variable
xb double pu Exciter state variable

CONSTANT_VOLTAGE

By default, the simple exciter is in CONSTANT_VOLTAGE operation mode, which regulates the positive-sequence terminal voltage of the diesel_dg (note the positive sequence measure there - massive unbalance can occur, but still be "regulated on average" to the proper value).

Parameters specific to the CONSTANT_VOLTAGE operation mode are:

Table 10 - CONSTANT_VOLTAGE mode parameters
Property Type Unit Description
Vterm_max double pu Upper voltage limit for super-second
Vterm_min double pu Lower voltage limit for super-second

The voltage reference is set through the common property of vset or Vset, defined above.

CONSTANT_Q

The CONSTANT_Q mode of operation allows the diesel_dg object to maintain a set reactive power output. This is accomplished through a simple PI controller that adjusts the exciter set points.

Parameters specific to the CONSTANT_Q operation mode are:

Table 11 - CONSTANT_Q mode parameters
Property Type Unit Description
Exciter_Q_constant_Qref double pu Qref input to AVR controls
Exciter_Q_constant_ki double pu Integration gain for constant Q mode
Exciter_Q_constant_kp double pu Proportional gain for constant Q mode

Q_V_DROOP

The Q_V_DROOP mode of operation apply a droop curve to the voltage/reactive power output, allowing for a proportional response to deviations and coordination with other generators.

Parameters specific to the Q_V_DROOP operation mode are:

Table 12 - Q_V_DROOP mode parameters
Property Type Unit Description
mq_QV_Droop double pu Q-V droop slope
SEXS_Q_V_droop double Q-V droop slope - overload of mq_QV_Droop
Vset_QV_droop double pu Voltage setpoint/offset of QV droop
SEXS_Vset double pu Voltage setpoint/offset of QV droop - overload of Vset_QV_droop
Vref_SEXS double pu Voltage reference for SEXS exciter - overload of vset or Vset above

Other Operations/Operating modes

There are a couple supplementary modes of operation or outputs for the diesel_dg object.

CVR Operations

The exciter also supports an extension to all of the above operating modes, though its use is primarily aimed at the CONSTANT_VOLTAGE and Q_V_DROOP modes of operation. The overall idea is when the frequency drops or rises on the system, the voltage is decreased or increased (respectively) to try and decrease or increase the load (for voltage-dependent load sources, like impedance and current). Details on the approach and the impacts can be found in this paper.

Parameters specific to the CVR operation mode are:

Table 13 - CVR mode parameters
Property Type Unit Description
Exciter properties
Vref double pu Exciter CVR control voltage reference value
CVR_mode enumeration N/A Determines the CVR mode in Exciter model. Valid options are:
  • HighOrder - High order control mode
  • Feedback - First order control mode with feedback loop
CVR_enabled bool N/A True to enable CVR control in the exciter
CVR_ki_cvr double pu parameter of the integration control for CVR control
CVR_kp_cvr double pu parameter of the proportional control for CVR control
CVR_kd_cvr double pu parameter of the deviation control for CVR control
CVR_kt_cvr double pu parameter of the gain in feedback loop for CVR control
CVR_kw_cvr double pu parameter of the gain in feedback loop for CVR control
CVR_PI bool N/A True if the PI controller is implemented in CVR control
CVR_PID bool N/A True if the PID controller is implemented in CVR control
CVR_Kd1 double parameter of the second order transfer function for CVR control
CVR_Kd2 double parameter of the second order transfer function for CVR control
CVR_Kd3 double parameter of the second order transfer function for CVR control
CVR_Kn1 double parameter of the second order transfer function for CVR control
CVR_Kn2 double parameter of the second order transfer function for CVR control
vset_delta_MAX double pu Maximum delta Vset limit
vset_delta_MIN double pu Minimum delta Vset limit

-

State variables
vadd double pu Delta Vset
vadd_a double pu Delta Vset before going into bound check
x_cvr1 double pu Exciter state variable - CVR mode
x_cvr2 double pu Exciter state variable - CVR mode

Fuel Emissions Calculation

The diesel_dg model has some very simple fuel, emissions, and "frequency metrics" calculations. The frequency deviation and frequency-related metrics in Table 14 aren't really emissions-related, but are only computed when emissions capabilities are activated.

Parameters specific to the fuel emissions capabilities are:

Table 14 - Fuel emissions calculations parameters
Property Type Unit Description
fuelEmissionCal bool N/A flag to enable if the fuel and emission calculations
outputEnergy double kWh Total energy(kWh) output from the generator
FuelUse double gal Total fuel usage based on kW power output
efficiency double kWh/gal Total energy output per fuel usage
CO2_emission double lb Total CO2 emissions based on fuel usage
SOx_emission double lb Total SOx emissions based on fuel usage
NOx_emission double lb Total NOx emissions based on fuel usage
PM10_emission double lb Total PM-10 emissions based on fuel usage
frequency_deviation double pu Frequency deviation of diesel_dg
frequency_deviation_energy double pu Frequency deviation accumulation of diesel_dg
frequency_deviation_max double pu Frequency deviation of diesel_dg
realPowerChange double W Real power output change of diesel_dg
ratio_f_p double pu Ratio of frequency deviation to real power output change of diesel_dg

References

  1. Kundur, P. “Power system stability and control” New York: McGraw-hill, 1994.
  2. Harley, R. G., E. B. Makram, and E. G. Duran. "The effects of unbalanced networks on synchronous and asynchronous machine transient stability." Electric power systems research 13, no. 2 (1987): 119-127.
  3. Makram, E. B., V. O. Zambrano, and R. G. Harley. "Synchronous generator stability due to multiple faults on unbalanced power systems." Electric power systems research 15, no. 1 (1988): 31-39.
  4. Makram, E. B., V. O. Zambrano, R. G. Harley, and Juan C. Balda. "Three-phase modeling for transient stability of large scale unbalanced distribution systems." Power Systems, IEEE Transactions on 4, no. 2 (1989): 487-493.
  5. Salim, R. H., and R. A. Ramos. "A Model-Based Approach for Small-Signal Stability Assessment of Unbalanced Power Systems." IEEE Transactions on Power Systems, November 2012.
  6. Krause, P., O. Wasynczuk, and S. Scott. "Analysis of electric machinery." IEEE Power Eng. Soc 15, no. 3 (1995).
  7. Kundur, P., and P. L. Dandeno. "Implementation of advanced generator models into power system stability programs." Power Apparatus and Systems, IEEE Transactions on 7 (1983): 2047-2054.

See Also