Diesel Generator

The diesel_dg object represents a synchronous distributed generation model of a diesel generator. The model supports both a QSTS-only model and subsecond (transient mode) 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 transient mode-compatible diesel generator

PQ CONSTANT mode diesel dg

This section describes GridLAB-D™ implementation of diesel generator in PQ constant mode.

A constant_P mode is implemented in the governor type P_CONSTANT:

In the constant_P mode, a time delay is applied to the electric power output from the diesel generator. The delayed electric power output is compared with the constant real power reference, then applied to a PI controller, to get the actuator input. The actuator part and time delay part of the GGOV01 governor is used in constant_P mode. Output of the constant_P mode is the mechanical power of the diesel generator.

The constant_Q mode is implemented based on the existing exciter SEX_PTI:

GridLAB-D™ Implementation

Diesel Generator in PQ Constant mode example

This diesel generator object is implemented in both constant P and constant Q mode.

By selecting Governor_type as P_CONSTANT, the constant P mode is selected. This example sets Pref value as 0.5 p.u. The PI controller settings for the constant Pref mode are 0 for proportional control, and 0.05 for integral control. In addition, parameters of the actuator and time delay part of the P_CONSTANT are also defined in the example.

By selecting Exciter_Q_constant_mode as true, the constant Q mode is selected. This example sets Qref value as 0.6 p.u.. The PI controller settings for the constant Q mode are 0.01 for proportional control, and 0.05 for integral control.

Example of Diesel Generator in PQ Constant mode

module generators;
object diesel_dg {
     flags DELTAMODE;
     parent 8;
     name Gen2;
     Rated_V 4156; //Line-to-Line value
     Rated_VA 1000000; // Defaults to 10 MVA
     Gen_type DYN_SYNCHRONOUS;
     rotor_speed_convergence ${rotor_convergence};
     Exciter_type SEXS;
     Governor_type P_CONSTANT;
     // Actuator and time delay parameters for P_CONSTANT mode
     P_CONSTANT_Tpelec 1.0; // Electrical power transducer time constant, sec. (>0.)
     P_CONSTANT_Tact 0.05; //0.5; // Actuator time constant
     P_CONSTANT_Kturb 1.5; // Turbine gain (>0.)
     P_CONSTANT_wfnl 0.2; //0.2; // No load fuel flow, p.u
     P_CONSTANT_Tb 0.01;//0.1; // Turbine lag time constant, sec. (>0.)
     P_CONSTANT_Tc 0.2; // Turbine lead time constant, sec.
     P_CONSTANT_Teng 0.0; // Transport lag time constant for diesel engine
     P_CONSTANT_ropen 050; // Maximum valve opening rate, p.u./sec.
     P_CONSTANT_rclose -050; // Minimum valve closing rate, p.u./sec.
     P_CONSTANT_Kimw 0.0;//0.002; // Power controller (reset) gain 
     inertia 2.5;
     // PI controller parameters of P_CONSTANT mode
     P_CONSTANT_Pref 0.5; // Set P reference, p.u. 
     P_CONSTANT_kp 0;  // ki for the PI controller implemented in P constant transient mode
     P_CONSTANT_ki 0.05;  // kp for the PI controller implemented in P constant transient mode
     Exciter_Q_constant_Qref 0.6; // Set Q reference, p.u. 
     Exciter_Q_constant_mode true; // Flag indicating whether the diesel generator exciter is operating based on Qref given
     Exciter_Q_constant_kp 0.01;  // ki for the PI controller implemented in Q constant transient mode

}

Properties

This table lists the properties related to diesel generator in PQ constant mode. Some parameters used by diesel_dg can be found in the diesel_dg documentation page.

Table 2: diesel_dg property descriptions

Property name	Type	Unit	Description
Gen_type	enumeration	none	Defines type of diesel generator (INDUCTION , SYNCHRONOUS, DYN_SYNCHRONOUS). Should choose DYN_SYNCHRONOUS for diesel generator in PQ constant mode.
rotor_speed_convergence	double	rad	Convergence criterion on rotor speed used to determine when to exit transient mode
Exciter_type	enumeration	none	Exciter model for dynamics-capable implementation (NO_EXC , SEXS). Should choose diesel_dg_type
Governor_type	enumeration	none	Governor model for dynamics-capable implementation (NO_GOV , DEGOV1, GAST, GGOV1_OLD, GGOV1, P_CONSTANT). Should choose P_CONSTANTfor this diesel generator in PQ constant mode.
Parameters related to P constant mode
P_CONSTANT_Pref	double	none	Pref value for P constant mode
P_CONSTANT_kp	double	none	Parameter of the proportional control for constant P mode
P_CONSTANT_ki	double	none	Parameter of the integration 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	none	Turbine gain
P_CONSTANT_wfnl	double	none	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	/s	Maximum valve opening rate
P_CONSTANT_rclose	double	/s	Minimum valve closing rate
P_CONSTANT_Kimw	double	/s	Power controller (reset) gain
Parameters related to Q constant mode
Exciter_Q_constant_Qref	double	none	Qref value for Q constant mode
Exciter_Q_constant_mode	double	none	True if the generator is operating under constant Q mode
Exciter_Q_constant_kp	double	none	Parameter of the proportional control for constant Q mode
Exciter_Q_constant_ki	double	none	Parameter of the integration control for constant Q mode

Test cases

In order to verify the implementation of PQ_CONSTANT mode diesel generator, a test case in 123-bus feeder with one isochronous mode diesel_dg Gen 1, and one PQ_CONSTANT mode diesel_dg Gen 2 is applied. At 5.001 second, part of the feeder is disconnected. Gen 1 will reduce its generation, and Gen 2 will maintain its generation after the transient. Below diagram shows the generation from the two generators before and after the transient.

To run this case, please find in the autotest in GridLAB-D™ generator module.

QSTS Mode

For QSTS mode, the follow properties are valid:

Table 3: 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 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 transient mode-enabled simulations, the following variables are commonly available, or enable the specific controls detailed later:

Table 4: 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.
transient mode_only_changes	bool	N/A	Dynamic equations are only initialized once, on the first QSTS-to-transient mode transition. Assumes all changes occur in transient mode.
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 transient mode 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 transient mode 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

Table 5: General set-points/inputs for controls

Parameter	Type	Unit	Description
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)

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 6: 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 7: 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 8: 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 9: 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 10: 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 11: 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 12: 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 13: 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 14: 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 15: 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 16: 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.

Related Concepts:

• Early diesel_dg documentation
• Constant PQ modes for diesel
• Generator Module Guide
• Generators (module)
  • Battery
  • Diesel dg
  • Energy storage
  • inverter
  • Microturbine
  • Power electronics
  • Rectifier
  • Solar
  • Windturb dg