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ETAP PowerStation 4.0

User Guide

Copyright 2001 Operation Technology, Inc.

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Operation Technology, Inc. 20-1 ETAP PowerStation 4.0

Chapter 20

User-Defined Dynamic Models (UDM)

The PowerStation User-Defined Dynamic Models (UDM) program is an interpreter tool which links user-defined governor, exciter, and Power System Stabilizer (PSS) models for synchronous generators and exciter models for synchronous motors. PowerStation compiles these dynamic models when conducting transient stability studies at run time. The UDM control blocks can be created using the Matlab Simulink interface tool. PowerStation includes a number of internally modeled turbine/governor, exciter/AVR, and PSS block diagrams such as IEEE types and manufacturer specified models. The UDM program is needed in cases when a specific model is not represented internally in PowerStation. Using Simulink®, Create UDM Template File Create a custom dynamic model (block diagram / transfer function). Save the model in a specific directory in PowerStation, this is called a UDM Template file.

From PowerStation Editors, Create UDM Equation File Select the UDM Template Model (governor, exciter, or PSS) for any synchronous generator. Select the UDM Template Model (exciter) for any synchronous motor. Press the Compile button to create the UDM Equation file, which is specific for that machine. PowerStation gives you options to map input and output variable names as well as test the model. From PowerStation Transient Stability Mode, Run Studies Run transient stability studies and the UDM models will be automatically used.

User-Defined Dynamic Models Create UDM


20.1 UDM Template File Open the Simulink Editor and build your control block diagram, such as governor, exciter, or PSS model, using the applicable block components provided by Simulink. When you save the control block diagram as XYZ, Simulink will automatically generate a scripting file “XYZ.mdl”, which we refer to as the UDM Template file. This implies that you can use this Template file for any applicable machines in multiple PowerStation project files.

20.1.1 Create Template File Using Simulink Some rules and requirements on creating UDM Template files are applied to the current version of ETAP PowerStation and are specified below. • The blocks and components of Simulink, which are recognized by ETAP PowerStation application

are as following:

• The maximum order of a transfer function (Transfer Fcn) block is a third order function. • The function types that can be used in an Fcn block consists of: sin, cos, tan, atan, abs, exp, sqrt,

and log.



• The input/output variable names you specify for your block diagrams in Simulink can be specified

arbitrary and then mapped to PowerStation input/output variable names using the System Variable Selection Editor (Section 20.4). However, to simplify your work, we recommend using the following key words for the input/output variable names. The appropriate key words reserved for PowerStation UDM Turbine/Governor, Exciter/AVR, and PSS models, are given in the following tables.

Turbine/Governor Model Key Word Description

Pe Generator Real Electrical Power Input W Generator Speed

Output Pm Turbine Output Mechanical Power

Exciter/AVR Models Key Word Description

Vt Machine Terminal Voltage CVt Machine Terminal Voltage in complex form

It Machine Terminal Current CIt Machine Terminal Current in complex form Pe Machine Real Power Qe Machine Reactive Power Vs PSS Signal

Input

Ifd Machine Field Current

Output Efd Exciter Output Voltage

PSS Model Key Word Description

Vt Generator Terminal Voltage W Shaft Speed f Generator Terminal Voltage Frequency

Pe Generator Real Power Pm Generator Mechanical Power

Input

Ang Generator Rotor Angle

Output Vs PSS Output Signal



Some examples of block diagrams showing the input and output variables for turbine/governor, exciter/AVR, and PSS models are shown below.



20.1.2 Saving UDM Template File The control block diagram file (XYZ.mdl) created by Simulink must be saved under the following folders:

Governor Models ETAPS\PowerStation\Udm\Gov Exciter Models ETAPS\PowerStation\Udm\Exc PSS Models ETAPS\PowerStation\Udm\Pss

The following figure shows two UDM exciter models saved in the directory in which the PowerStation program is installed. These two models can then be selected from the Exciter page of synchronous generators and motors.

User-Defined Dynamic Models Select UDM


20.2 Select UDM Models Once an UDM Template file is created and saved in the applicable folder, PowerStation will automatically add it in the list box of Governor, Exciter, or PSS models for synchronous machines. You can select the desired UDM Template file in the Exciter, Governor, or PSS page of synchronous machine editors. Note that the same Template file can be used for multiple machines in multiple PowerStation project files. The Compile UDM button becomes active once you select a UDM Template file.

20.2.1 UDM Models for Synchronous Generator Exciter/AVR The following figure shows how to select an Exciter UDM Template file for a synchronous generator.



20.2.2 UDM Models for Synchronous Generator Turbine/ Governor The following figure shows how to select a Governor UDM Template files for a synchronous generator.



20.2.3 UDM Models for Synchronous Generator PSS The following figure shows how to select a PSS UDM Template file for a synchronous generator.



20.2.4 UDM Models for Synchronous Motor Exciter/AVR The following figure shows how to select an Exciter UDM Template file for a synchronous motor.

User-Defined Dynamic Models UDM Compiler Editor


20.3 Compile UDM Equation File After you select a UDM Template file from an Editor, click on the “Compile UDM” button to create a compiled equation file for the selected machine and UDM model. This compiled equation file is automatically linked to this machine and will be used from now on whenever you run the transient stability studies. When you click the Compile UDM button, the UDM Compiler dialogue box will show up. This Compiler dialogue box provides three functions for you to specify the initial condition parameters, compile the UDM script file to the equation file, and the test equation file.

20.3.1 UDM Compiler

User-Defined Dynamic Model

Type This indicates the model type (Governor, Exciter, or PSS) that the UDM Template file represents.

Element This indicates the ID of the machine that the UDM Template file will be compiled to an Equation file.

User-Defined Dynamic Models UDM Compiler Editor


UDM Template File This indicates the name and the path of the UDM Template file (script file created by Simulink). Compile UDM Template File to Equation File Here you can complete the Equation file and change the Advanced Setting.

Advanced Setting In this Advanced Setting Editor you can specify the initial condition parameters: Max, Iteration, Precision, and Increment Step. These parameter settings will affect the convergence of initialization calculation.

Max. Iteration This parameter defines the maximum iteration of initialization calculation. The default value is 2000. It is recommended that you do not change this parameter in most cases.

Precision This parameter defines the precision in per unit for the convergence of initialization calculation. The default value is 0.0001. It is recommended that you do not change this parameter in most cases.

Increment Step This parameter defines the increment step for the convergence of initialization calculation. The default value is 0.0035. It is recommended that you do not change this parameter in most cases.

Compile Click this button to convert the UDM Template file to UDM Equation file that will be used by PowerStation.

UDM Equation File This indicates UDM Equation file name and path.

Test Model Click this button to test the UDM Equation file with different test modes in a stand-alone mode.

User-Defined Dynamic Models System Variable Selection Editor


20.4 System Variable Name Mapping When you click on the Compile button, the Variable Name Mapping Editor will show up. This editor consists of Governor, Exciter, and PSS editor pages, which are provided for you to select the appropriate system input, output, and reference variable names represented by block names in model block diagram. This editor allows you to map the variable names of the input, output, and reference of the Template file to the keyword that are used by PowerStation. If the correct key words (as explained in previous sections) are used in model block diagram (Template file), the proper variable names corresponding to PowerStation key words are automatically picked up in the selection list box, otherwise it shows None. Click the OK button in an editor page to carry out the compiling processing. Once the compiling is successfully completed, the UDM Template file is converted to an UDM Equation file with the name and format as “UDM_GENID_XYZ.bin”, where GENID is the ID of the machine and XYZ is the name of the Template file. This Equation file is saved under the same folder where project file resides.

20.4.1 Governor Page The following displays the variable names of the input, output, and reference variables for governors.



System Input

Speed (W) Select to map the variable name of the governor input speed to the PowerStation key word (W). Speed is in per unit of the generator synchronous speed.

Elec Power (Pe) Select to map the variable name of the governor input electrical power to the PowerStation key word (Pe). This is the generator real electrical power in per unit of the generator MW.

System Output

Mech Power (Pm) Select to map the variable name of the governor output power to the PowerStation key word (W). This is the generator output mechanical power in per unit of the generator MW.

System Reference

Speed Ref (Wref) Select to map the variable name of the speed reference to the PowerStation key word (Wref). This is the governor speed reference in per unit of the generator synchronous speed.

Power Ref (Pref) Select to map the variable name of the power reference to the PowerStation key word (Pref). This is the governor power reference in per unit of the generator MW.

Temp Ref (Tref) Select to map the variable name of the temperature reference to the PowerStation key word (Tref). This is the governor temperature reference in per unit of the governor base.



20.4.2 Exciter Page The following displays the exciter system variable selection page and describes the exciter input, output, and reference variables.

System Input

Terminal Voltage (Vt) Select to map the variable name of the exciter input terminal voltage to the PowerStation key word (Vt). This is the machine terminal voltage magnitude in per unit of the nominal machine terminal bus voltage.

Terminal Current (It) Select to map the variable name of the exciter input terminal current to the PowerStation key word (It). This is the machine terminal current magnitude in per unit of the rated machine current.

Complex Terminal Voltage (CVt) Select to map the variable name of the exciter input complex terminal voltage to the PowerStation key word (CVt). This is the complex machine terminal voltage in per unit of the nominal machine terminal bus voltage.



Complex Terminal Current (CIt) Select to map the variable name of the exciter input complex terminal current to the PowerStation key word (CIt). This is the complex machine terminal current in per unit of the rated machine current.

Real Power (Pe) Select to map the variable name of the exciter input real electrical power to the PowerStation key word (Pe). This is the machine real electrical power in per unit of the machine MVA.

Reactive Power (Qe) Select to map the variable name of the exciter input reactive power to the PowerStation key word (Qe). This is the machine reactive power in per unit of the machine MVA.

PSS Signal (Vs) Select to map the variable name of the exciter input PSS signal to the PowerStation key word (Vs). This is the PSS output signal in per unit of nominal machine terminal bus voltage.

Field Current (Ifd) Select to map the variable name of the exciter input field winding current to the PowerStation key word (Ifd). This is the machine field winding current in per unit of machine base.

System Output

Field Voltage (Efd) Select to map the variable name of the exciter output voltage to the PowerStation key word (Efd). This is the machine exciter output voltage in per unit of the nominal machine terminal bus voltage.

System Reference

Voltage Ref (Vref) Select to map the variable name of the voltage reference to the PowerStation key word (Vref). This is exciter voltage reference in per unit of the nominal machine terminal bus voltage.



20.4.3 PSS Page The following displays the PSS system variable selection page and describes the PSS input and output variables.

System Input

Shaft Speed (W) Select to map the variable name of the PSS input shaft speed to the PowerStation key word (W). This is generator shaft speed increment in per unit of the generator synchronous speed.

Voltage Frequency (f) Select to map the variable name of the PSS input voltage frequency to the PowerStation key word (f). This is the generator terminal voltage frequency increment in per unit of the nominal system frequency.

Real Power (Pe) Select to map the variable name of the PSS input real power to the PowerStation key word (Pe). This is the generator real electrical power increment in per unit of the machine MVA.

Rotor Angle (Ang) Select to map the variable name of the PSS input rotor angle to the PowerStation key word (Ang). This is the generator rotor angle increment in radius.



Mech Power (Pm) Select to map the variable name of the PSS input mechanical power to the PowerStation key word (Pm). This is the generator mechanical power increment in per unit of the generator MVA.

Terminal Voltage (Vt) Select to map the variable name of the PSS input terminal voltage to the PowerStation key word (Vt). This is the generator terminal voltage magnitude increment in per unit of the nominal machine terminal bus voltage.

System Output

PSS Signal (Vs) Select to map the variable name of the PSS output signal to the PowerStation key word (Vs). This is the PSS output signal in per unit of nominal machine terminal bus voltage.

User-Defined Dynamic Models Test Model Editor


20.5 Test Model The UDM program also allows you to do a standard-alone test for your UDM equation files. Depending on the model type you have selected, click the Test Model button, and a Test Model Editor, like the Governor Test Model Editor, the Exciter Test Model Editor, or the PSS Test Model Editor, will show up. This editor is provided for you to specify the appropriate system input variable values and the test type as Load Shedding, Load Acceptance, and Fault Bus on a simple power system. The test power system consists of a single generator connected to a single load via a transmission line as shown below. The parameters of the power system are built in the program.

20.5.1 Governor Model Test The following displays the governor model test editor and describes the test input/output values, simulation time, and test types.

Vt Governor

Exciter

Generator

ZL



System Input (pu)

Speed (W) This parameter defines the generator speed in per unit. The default value is 1.0.

Elec Power (Pe) This parameter defines the generator real electrical power in per unit. The default value is 1.0 for testing load shed and fault bus, and 0.5 for testing load acceptance.

Simulation Time

Time Step (sec) This parameter defines the simulation time step in seconds. The default value is 0.005.

Total Time (sec) This parameter defines the total simulation time in seconds. The default value is 40.0.

System Output (pu)

Mech Power (Pm) This field displays the governor output mechanical power in per unit.

Test Type

Load Shed Select this option to simulate power system load shed by 50%.

Load Acceptance Select this option to simulate power system load adding by 50%.

Fault Bus Select this option to simulate short-circuit fault on the generator terminal bus.

Test When the test input values and simulation times are specified and a test type is selected in the governor model test editor, you can implement the governor model testing by clicking the Test button.

Plot When the testing is successfully completed, the results are available for plot. Click the Plot button in the Test Model Editor, the plot window will show up as shown below:



An Example of a Governor Test Result Plot on Load Shed

20.5.2 Exciter Model Test The following displays the exciter model test editor and describes the test input/output values, simulation time and test types.



System Input (pu)

Terminal Voltage (Vt) This parameter defines the generator terminal voltage in per unit. The default value is 1.0.

Terminal Current (It) This field displays the generator terminal current in per unit.

Real Power (Pe) This field displays the generator real electrical power in per unit.

Reactive Power (Qe) This field displays the generator reactive electrical power in per unit.

PSS Signal (Vs) This parameter defines the PSS input signal in per unit. The default value is 0.

Field Current (Ifd) This parameter defines the generator filed winding current in per unit. The default value is 0.

Complex Terminal Voltage (CVt) This field displays the generator terminal complex voltage in per unit.

Complex Terminal Current (It) This field displays the generator terminal complex current in per unit.

Simulation Time



System Output (pu)

Filed Voltage (Efd) This field displays the exciter output voltage in per unit.

Test Type

Load Shed Select this option to simulate power system load shed by 50%.

Load Acceptance Select this option to simulate power system load adding by 50%.



Fault Bus Select this option to simulate short-circuit fault on generator terminal bus.

Test When the test input values and simulation times are specified and a test type is selected in the exciter model test editor, you can implement the exciter model testing by clicking Test button.


An Example of an Exciter Test Result Plot on Load Shed



20.5.3 PSS Model Test The following displays the PSS model test editor and describes the test input/output values, simulation time, and test types.

System Input (pu)

Shaft Speed (W) This parameter defines the generator speed increment value in per unit. The default value is 0.005.

Terminal Voltage (Vt) This parameter defines the terminal voltage increment in per unit. The default value is 1.0.

Real Power (Pe) This parameter defines the increment value of the generator real electrical power in per unit. The default value is 0.01.

Rotor Angle in rad (Ang) This parameter defines the generator rotor angle increment value in radius. The default value is 0.01.

Mech Power (Pm) This parameter defines the increment value of the generator mechanical power in per unit. The default value is 0.01.



Voltage Frequency (f) This parameter defines the increment value of the generator terminal voltage frequency in per unit. The default value is 0.01.

Simulation Time



System Output (pu)

PSS Signal (Vs) This field displays the PSS output signal in per unit.

Test When the test input values and simulation times are specified in the PSS model test editor, you can implement the PSS model testing by clicking the Test button. The PSS model test is conducted only with a pulse disturbance on its input signals.


An Example of a PSS Test Result Plot on a Pulse Disturbance of Shaft Speed

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