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Objective
Validate the OP8219 interface for the Festo 2 kW dynamometer encoder module with the Opal simulator and validate the OP8219 interface unit’s inverter signals at the 8857/37 inverter gates.
Description
This section presents integration of the Festo 2 kW dynamometer encoder module and 8857/37 inverters into OPAL-RT simulator using the Festo 8219 inverter decoder interface unit and OP8662 high voltage and current measurement unit.
The user is presented with a SIMULINK-based model to perform a basic operation of the dynamometer encoder module and Festo 8219 inverter.
Model Overview
The RT-LAB model depicted in figure 1 consists of two subsystems.
The “SM_OP5707” subsystem includes the model that runs on the real-time simulator
The “SC_Offline_User_Interface” subsystem presents the user interface that runs on the host PC.
The subsystem consists of five areas as shown in figure 2:
The blue area (PWM Enable (Module 1, 2)) enables the PWM signals of the inverter modules
The green area (Frequency Reference (Module 1, 2)) is dedicated to adjusting the switching frequency of the inverter modules
The yellow areas (Duty Cycle Reference (Module-1)) and orange (Duty Cycle Reference (Module-2)) areas are used to set individual modulation indexes for each leg of the inverter modules.
The gray area (Signal Monitoring) is the block for receiving and monitoring data from the OPAL-RT simulator
The SM_OP5707 subsystem has two main blocks, including OP5707 IO Interface and PWM_GENERATION, as shown in figure 3:
The OP5707 IO Interface is used to interface the PWMs, voltages, current measurements, and encoder signals
The PWM_GENERATION generates the PWM signals for the inverter modules based on the modulation index and switching frequency set by the user
Connection Diagrams
Power off equipment before connecting any cable. See the Test Procedure below.
The connections of the OP5707 to the OP8662 and to the OP8219 are demonstrated in figure 4. The encoder terminal (DB9F) of the dynamometer needs to be connected to the encoder input (DB9F) of the OP8219 to measure the speed and position of the WRIM (DFIG). Connections must be performed as shown in figure 4.
The connections of the Festo 8857 inverter, OPAL-RT OP8662, and OPAL-RT OP8219 are illustrated in figure 5.
The user must respect the direction and location of the measurement depicted in figure 5.
The encoder connection between OPAL-RT OP8219 and Festo 8540 dynamometer is presented in figure 6.
The control connections (PWM) using the provided DB9 cables between OPAL-RT OP8219 and Festo 8857 inverters is also presented in figure 7.
Test Procedure
Ensure that all power source outputs are off (see figure 8 below).
Connect the system power circuit and connection signals as shown in figures 4 to 7.
Powered on the OP8662
Ensure that the power adaptor is connected to the OP8219 (figure 9).
Ensure that the Festo inverter modules 8857 are powered on using the 24 V AC voltage provided by the Festo power supply 8525 (figure 10).
Ensure that the 120 Ω resistive load Festo 8509 is switched on.
Ensure that the jumpers are always installed on the OPAL-RT OP8219 board (figure 12).
For all tests using OP8219, the jumpers need to be installed, unless otherwise stated.
Launch RT-LAB.
Import the model zip file in RT-LAB (see below).
Build, load, and execute the model.
Adjust the variable voltage knob to establish an AC voltage level with the amplitude of 80 Vpeak (Line-to-line voltage).
The following measured voltages and currents are shown in the RT-LAB scopes (figures 14 to 16).
The PWM signals are enabled for the 3-phase inverter Festo 8857 modules 1 and 2 by changing the reference from ’0′ to ’1′ (figure 17)
The modulation reference for the Festo 8857 inverter is set to ’0.5′ as shown in the following figure for modules 1 and 2.
Set the reference frequency to ’4000′ for modules 1 and 2.
The measured PWM signals of the Festo 8857 inverter (module 1 or 2) approximately match the settings as shown in figure 20.
Turn on the Festo 8540 dynamometer and set it to “Speed Mode” at 2500 rpm in the forward direction.
The following results can be observed for the measured speed, position, and direction, respectively.
To stop the model:
Disable the PWMs for the 3-phase inverter modules by setting the “PWM Enable Module1,2″ from ’1′ to ’0′
Turn the variable voltage knob to ‘0 V’
Reduce the speed to zero and stop the dynamometer
Turn off the inverter module 8525, 8219 and OP8662.
Reset the model in RT-LAB
Conclusion
Based on the preceding tests, the hardware and software included in Festo’s models are declared fully functional and compliant with OPAL-RT specifications.