While strictly speaking, renewable generation does not have an "exciter", "governor", or "stabilizer" in the way that a synchronous generator model does, the relationships in software between the convertor model, electrical model and mechanical model are very similar. These relationships are shown more in the Generator Models Overview topic.
As a result, when looking at generators in the Simulator user interface, the various renewable models will be listed under the traditional categories for synchronous machines of "machine model", "exciter", "governor", or "stabilizer". In addition to these blocks, there are also additional blocks for Aerodynamic, Pref Controller, and Plant Controller objects. These were first added in Version 18.
Examples are shown below.
|
Model Class |
Type 3 Wind Second Gen |
Type 4 Wind Second Gen |
Solar PV |
Distributed Solar PV |
Energy Storage |
Type 1 Wind |
Type 2 Wind |
Type 3 Wind First Gen |
Type 4 Wind First Gen |
GE Type 2 Model |
GE Type 3 or Type 4 |
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Wind Machine Models
|
REGC_A |
REGC_A |
REGC_A |
PVD1 |
REGC_A |
WT1G WT1G1 |
WT2G WT2G1 |
WT3G WT3G1 |
WT4G WT4G1 |
GENWRI |
GENWTG |
|
Wind Electrical Models listed as Exciters |
REEC_A |
REEC_A |
REEC_B |
REEC_C |
WT2E WT2E1 |
WT3E WT3E1 |
WT4E WT4E1 |
EXWTG1 |
EXWTGE |
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|
Wind Mechanical Models listed as Governors |
WTGT_A |
WTGT_A |
WT1T WT12T1 |
WT2T
|
WT3T WT3T1 |
WT4T |
WNDTRB |
WNDTGE |
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|
Wind Pitch Control |
WTGPT_A |
WT1P_B |
WT2P WT12A1 |
WT3P WT3P1 |
|
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|
Aerodynamic Model |
WTGA_A |
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|
Pref Controller Model |
WTGTRQ_A |
||||||||||
|
Plant Controller Model |
REPC_A REPC_B |
REPC_A REPC_B |
REPC_A REPC_B |
REPC_A REPC_B |
Development of these second generation models was performed extensively in the WECC Model Validation Working Group in the western part of the United States. The following documents reports which describe these models in more detail created by WECC.
- WECC-Type-1-and-2-Generic-Turbine-Pseudo-Governor-model-1012.pdf
- WECC-Type-3-Wind-Turbine-Generator-Model-Phase-II-012314.pdf
- WECC-Type-4-Wind-Turbine-Generator-Model-Phase-II-012313.pdf
The following images depict how the Type 3 and Type 4 wind turbine models pass signals between one another. Solar PV and Energy Storage models work the same as well.
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Second Generation Type 3 Wind Turbine
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Second Generation Type 4 Wind Turbine
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First Generation Type 4 Wind Turbine 
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First Generation Type 4 Wind Turbine 
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It will obviously not make any sense to configure a generator to use a wind machine model with a traditional synchronous machine exciter model and governor, so care should be taken not to setup such configurations. Presently Simulator does perform some validation checks and returns validation errors in situations like this.
A wind farm usually consists of many small (several MW) turbines. Each individual turbine’s voltage is usually less than 1 kV (600 V is common) with a step-up transformer to increase the voltage to several dozen kV (34.5 kV common). The wind farm is usually modeled in aggregate requiring the aggregate model to account for impedance of collector system and then model per unit values at N times individual values. How accurate the aggregation is remains an open question.
There are four major types of wind turbine models used in transient stability studies which will each be considered in detail shortly.
- Type 1 : Induction generators with fixed rotor resistance
- Type 2 : Induction generators with variable rotor resistance
- Type 3 : Doubly-fed induction generators
- Type 4 : Full converter generators
Type 1: Induction generators with fixed rotor resistance
The most basic representation of a Type 1 wind turbine is as a conventional induction machine, however inertia is modeled with the machine. More detailed representations also include using a two-mass model (one mass for the generator and one for the turbine), and a pseudo governor. Inertia is sometimes modeled with the machine and sometimes as a governor in Simulator. A pseudo-governor is modeled as either a governor or a stabilizer in Simulator (depending on how inertia is modeled).
The MOTOR1 and GENIND models from the GE DYD file are the same, except for a sign convention on the current. They have integrated inertia. They cannot be used with other Type 1 governor/stabilizer models so no turbine dynamics are included. The CIMTR1, CIMTR2, CIMTR3, and CIMTR4 models from the PTI DYR file have the same restrictions as with the MOTOR1 and GENIND models .
The WT1G model is the GE DYD representation for a Type 1 wind turbine, while the WT1G1 is the PTI DYR model. Electrically they are quite similar to the GENIND model, except they do not include any inertia. Therefore they must be modeled with a WT1T (GE) or WT12T1 (PTI) model, both of which are included in the list of governors. The WT1T/WT12T1 models can represent the generator/turbine using either a one mass or two mass model. Both of these governors can also be used with Type 2 Wind Turbines.
The WT1P (GE) and WT12A1 (PTI) models represent a pseudo governor response model. These models are listed inside Simulator as a stabilizer models. The inputs to these models are machine speed and electrical output, while the output of the model is mechanical power. Again, these models can be used for both Type 1 and Type 2 wind turbines. It is recommended that you use the [machine / governor / stabilizer] grouping of [WT1G / WT1T / WT1P] or [WT1G1 / WT12T1 / WT12A1] to represent Type 1 wind machines.
Type 2 : Induction generators with variable rotor resistance
The Type 2 models augment the Type 1 by allowing for variable rotor resistance control in the wound rotor induction generator. This model is used to represent wind turbines such as the Vestas V80. Resistance control is represented by a PowerWorld Simulator using a model from the "exciter" list. Inertia is included with some machine models, or is included with a pseudo governor model. PowerWorld supports two classes of Type 2 models. From the GE DYD file we support the combination of the GENWRI machine, EXWTG1 exciter, and WNDTRB governor. From the PTI DYR file we support the combination of the WT2G1 machine, WT2E1 exciter, WT12T1 governor, and WT12A1 stabilizer.
Modeling Using GENWRI, EXWTG1, and WNTRB models
The GENWRI models represents a single cage induction generator, and also includes a single mass inertia model with the machine. The initial operating slip must be given. From this, PowerWorld then calculates the necessary resistance to match this slip. The EXWTG1 exciter specifies the minimum and maximum external rotor resistance. The WNDTRB models the blade pitch control with an input of rotor speed and an output of Pmech. The resistance is set initially to match default slip of -0.04. During the fault the resistance increases to compensate for the increased speed.
Modeling Using WT2G1, WT2E1, WT12T1, and WT12A1 models
The W2G1 model is the PTI representation for a Type 2 wind turbine which should be similar to the GE models. These are all based on new standards which are being developed for wind turbine modeling. Electrically it is quite similar to the GENWRI model, except they do not include any inertia. Therefore they must be modeled with a WT1T (GE) or WT12T1 (PTI) model, both of which are included in Simulator as governor models. They also can use the WT1P or WT12A1 pseudo governors (which are included in Simulator as stabilizer models). The initial operating point is given by the R_Rot_Max field, which specifies the total rotor resistance. The external rotor resistance is controlled using the WT2E1 model, which is modeled in Simulator as an exciter.
The WT2E1 model controls the external resistance between values given by Rotrv_min and Rotrv_max. The inputs to WT2E1 are rotor speed and electrical power. Rotor speed is converted to an equivalent power using a piecewise linear slip-power curve that is entered with the WT2G1 model. The curve is assumed to have odd symmetry (f(-x) = -f(x)). An offset is added to model to get it to initialize to zero.
Type 3 : Doubly-fed induction generators
Modeling using the WT3G ,WT3E, WT3T and WT3P models
The GE DYD file supports a combination of models of a WT3G machine model, WT3E exciter, WT3T governor, and WT3P stabilizer to model a Type 3 wind generator. The WT3G model represents the generator behavior of the Type 3 and is the interface with network equations. The WT3E model represents the reactive power control. The inputs to WT3E are the generator real and reactive power, and the voltages at the terminal and regulated bus, while the outputs are Eqcmd and Ipcmd. The WT3T model represents the mechanical equations. The WT3T inputs are the blade pitch and electrical power, while output is the rotor/turbine speeds. The WT3P model represents the pitch control. The WT3P input is the generator speed/power, while the output is pitch angle.
Modeling using the WT3G1, W3G2 ,WT3E1, WT3T1 and WT3P1 models
The PTI Type 3 models are very similar to the GE models except some default values are different. There are two machine models: WT3G1 and WT3G2. The WT3G2, an enhancement to the WT3G1, is recommended for new studies. WT3E1 is almost identical to WT3E (parameters in different order in the file format and PTI allows different negative rate limit). The WT3T1 is identical to WT3T. The WT3P1 is identical to WT3P (parameters in different order in the file format).
Detailed Models for common GE 1.5, 1.6, and 3.5 MW Turbines
GE provides more detailed models for their popular 1.5 MW, 1.6 MW and 3.5 MW turbines. These are modeled using the GEWTG (machine), EXWTGE (exciter), and WNDTGE (governor). The WNDTGE model combines the wind turbine model with the pitch control model; both one and two mass models are supported. PowerWorld provides the GE defaults for all three units for both single and double mass, and for either 60 or 50 Hz. When reading an EXWTGE model from a DYD file, PowerWorld automatically detects older record formats, reading parameters in the appropriate order for the format.
Type 4 : Full Converter Models
To model full converter wind turbines, use the WT4G1 machine model and WT4E1 exciter model.