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Objective
Validate the basic operation of Festo inverter connected to a RL load.
Description
This section presents the CPU model and test procedure for testing the inverter with RL load.
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 three areas as shown in figure 2.
The blue area (Inverter Control) enables the PWM signals (Enable Inverters) of the inverter module, sets it switching frequency (Inverters Switching Frequency), and adjusts its modulation index (Inverter modulation amplitude)
The gray area (Signal Monitoring) is the block for receiving and monitoring data from the OPAL-RT simulator
The orange area also provides important information regarding the test instructions
This subsystem consists of three main areas, including “OP8219 and OP8662 IO Interface,” “SIMULATION MODEL BASED ON MATLAB’S ‘UNIVERSAL BRIDGE’ BLOCK,” and “SIMULATION MODEL BASED ON ‘RT-LAB 2-LEVEL TSB’ BLOCK” as shown in figure 3.
The orange area is used to interface the PWMs besides the voltage and current measurements.
The blue and yellow areas are respectively used to implement the model in MATLAB and the real-time simulator.
Both real time and MATLAB models are compared with the results measured from the test bench.
Test Procedure
The connections of the OPAL-RT OP5707 to the OP8662 and OP8219 are demonstrated in figure 4 and must be performed as shown.
The connections of the Festo 8857 inverter, OPAL-RT OP8662, and OPAL-RT OP8219 are illustrated in figure 5 and the user must respect the direction and location of the measurement depicted.
The control connections (PWM) using the provided DB9 cables between OPAL-RT OP8219 and Festo 8857 inverters is also presented in figure 6.
Ensure that all power source outputs are off
Connect the system power circuit and connection signals as shown in figure 4-6
Launch RT-LAB
Import model zip file (see below) in RT-LAB
Build, load, and execute the model
Power on the OPAL-RT OP8662
Ensure that the power adaptor is connected to the OP8219.
Ensure that the Festo inverter modules 8857 are powered on using the 24 V AC voltage provided by the Festo power supply 8525.
Ensure that the 120 Ω resistive load 8509 is switched on.
Ensure that the jumpers are always installed on the OP8219 board.
For all tests involved using OP8219, the jumpers need to be installed, unless otherwise stated.
Ensure the Festo power supply unit 8525 is powered on and the voltmeter’s selection knob is set to DC 7-N.
Launch RT-LAB
Import model zip file in RT-LAB
Build, load, and execute the model
Increase the variable voltage knob to establish a DC voltage level of 100 V.
Enable the PWM signal for the 3-phase converter that is being tested, by using the toggle switch from ’0′ to ’1′.
The modulation reference for the Festo 8857 inverter is set to ’0.12′ as shown in figure 14.
The switching frequency reference for the Festo 8857 inverter is set to ’4000′ as shown in figure 15.
Ensure the Festo 8857 converter measurements approximately match the ones shown in figure 16. The 8857 inverter measures:
AC current of approx. ‘1.6 A’ peak
AC voltage of approx. ‘70 V’ peak
To stop the model:
Set the Festo 8857 ‘Inverters modulation amplitude’ modulation reference to ’0′.
Disable the PWM signal for the 3-phase converter that is being tested, by using the toggle switch from ’1′ to ’0′
Turn the variable voltage knob to ‘0 V’
Turn off the Festo bench
Reset the model in RT-LAB.
Conclusion
Based on the preceding tests, the hardware, and the software included in Festo inverter connected to a RL load model are declared fully functional and compliant with OPAL-RT specifications.