Diesel dg

= 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:

QSTS Mode
For QSTS mode, the follow properties are valid:

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

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:

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:

GAST
The GAST governor represents a simple

Parameters specific to the GAST model are:

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:

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:

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:

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:

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

CONSTANT_Q
The CONSTANT_Q</tt> 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:

Q_V_DROOP
The Q_V_DROOP</tt> 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:

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</tt> and Q_V_DROOP</tt> 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:

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:

= 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 =


 * Early diesel_dg documentation
 * Constant PQ modes for diesel