Control of FESTO’s 8540 dynamometer based on Mitsubishi’s A-800 inverter

In this subsection, the user is presented with a SIMULINK-based model to perform basic control over FESTO’s 8540 dynamometer through the serial interface. In this demo, the dynamometer will be operated in torque mode with speed limit. This means that the dynamometer will follow the torque reference if the speed limit is not surpassed. If the speed limit is reached the torque reference will be automatically limited so the speed limit is respected. Worth noting that while operating the dynamometer in torque mode, the speed needs to be limited to avoid the risk of over-speed (which would be the case if the torque developed by the dynamometer surpasses that from friction and the load at its shaft).

Since the user may be interested in monitoring and getting an insight into the serial communication protocol between OPAL-RT's simulator and Mitsubishi's A-800, some of the signals involved in the serial communication protocol are brought into the user’s console.

Procedure

1. Connect the OPAL-RT simulator to the OP8660 as shown in section 1.
2. Connect the OPAL-RT simulator with the host computer as shown in section 2.
3. Perform the control connections between OPAL-RT’s hardware and FESTO’s 8540 dynamometer as shown in section 3.3, i.e., serial asynchronous link (3.3.1) and ABZ encoder link (3.3.2).
4. Turn-on the 8540 dynamometer and, through its touch panel, enable its Computer-Based control, as depicted in Figure 5.1. In this operating mode, user can monitor the state of the dynamometer: torque, speed (frequency), current and voltage.

Import project zip in RTLAB.

Figure 2 presents the SIMULINK console generated by RT-LAB while executing Dynamometer_A700_OP4510.slx.

• First, establish a limit for the speed of the dynamometer. The allowed speed range for this demo is [0-1800] [rpm]. A recommended value is 1000[rpm].
• Next, establish a torque reference for the allowed range for this demo is [0-5] N*m. A recommended value is 0.7 N.m. Try different torque values close to 0.7 N*m and see the effect on the dynamometer's speed.
• Start the dynamometer using the Start_Stop manual switch (value 1).
• Stop the dynamometer using the Start_Stop manual switch (value 0).

The user console will allow you to monitor the speed and torque of the dynamometer. The speed reading comes directly from the dynamometer’s ABZ encoder connected to the OP8660. On the other hand, the torque reading is monitored through the serial link between the OP5600/OP4510/OP7000 simulator and dynamometer’s A-800 driver.

Console for the Dynamometer_A700_OP4510.slx demo as the model runs and the 8540 dynamometer operates in torque mode.

Control of FESTO’s 8857 inverter

In this subsection, user is presented with a SIMULINK-based model to perform basic control over FESTO’s 8857 inverter. A simple DC to AC scheme is implemented to feed a three-phase RL load as shown in Figure

5.3. Apart from verifying the correct operation of FESTO’s 8857 inverter and the control pulses generated by the OPAL-RT simulator, user will be able to make a side-by-side comparison between the actual waveforms generated by the hardware and those generated by the real time simulation of the circuit of interest (using both Simscape Electrical™ Specialized Power Systems (SPS, formerly known as SimPowerSystems™) and RT-LAB inverter blocks).

Procedure

1. Connect the simulator to the OP8660 as shown in section 1.
2. Connect the simulator with the host computer as shown in section 2.
3. Perform the control connections between OPAL-RT’s OP8660 and FESTO’s 8857 inverter as shown in section 3.4. Additionally, perform the power connections depicted in Figure 5.4 between OP8660’s voltage and current channels and FESTO’s hardware.

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• Make sure the selected inverter is fed through its 24 [V] AC input, as shown in section 3.4.2. (the same control pulses are sent to both inverters, so the user can choose any one of them). Turn ON the selected

inverter. Turn ON the 8525 power source: use 8525’s voltmeter and variable voltage knob to establish a DC voltage level between 40 and 50[V] DC. Make sure the voltmeter’s selection knob is set to DC 7-N.

• Import project zip in RTLAB.
• Figure 5 presents the SIMULINK console generated by RT-LAB while executing INVERTER_8837_OP4510.slx. The console will allow the user to enable the operation of the selected inverter, modify the frequency of the modulation carrier and monitor the current/voltage waveforms through the RL load. As indicated at the beginning of this section, a comparison is performed between the simulation output waveforms (using both Simscape Electrical Specialized Power Systems (SPS) RTE inverter blocks) and the actual waveforms of FESTO's 8857 inverter.

Figure 5.6 presents a detailed view of the console’s scope. User is encouraged to compare the generated waveforms, where:

• Ia/Va_SPS => simulation waveform obtained using Simscape Electrical Specialized Power Systems (SPS) universal IGBT bridge block (yellow trace)
• Ia/Va_RTE => simulation waveform obtained using RTEvents 2-level TSB block (red trace)
• Ia/Va_meas => actual waveform measured by OPAL-RT's OP8660 acquisition module (blue trace).
• It is worth noting from Figure 5.6, the close proximity between the measured current waveforms and those obtained by simulation through RT-LAB’s 2-level TSB block.

Advanced control techniques: Regulation of a DC-link bus

In this subsection, the user is presented with a SIMULINK-based model to perform advanced control over FESTO’s energy conversion hardware. More precisely, in this demo the 8857 Inverter is controlled to regulate a DC-link bus. Details on the control strategy are covered in OPAL-RT’s document RCP regulation of a DC link through an IGBT-based inverter. In this demo, the 8525 three-phase voltage source feeds the 8857 inverter, whose control regulates the DC voltage at its capacitor as shown in Figure 5.7. The resistive module 8311 is used to verify the correct regulation of the DC bus as the load is varied.

Figure 5.7: Advanced control of inverter module 8857: regulation of a DC bus.

 Procedure

1. Connect the OPAL-RT simulator to the OP8660 as shown in section 1.
2. Connect the OPAL-RT simulator with the host computer as shown in section 2.
3. Perform the control connections between the OP8660 module and FESTO’s 8857 inverters as shown in section 4. It is up to the user to decide which converter will act as DC-bus regulator: the MATLAB model sends the control pulses through the two inverter outputs of the OP8660.
4. Perform the power connections depicted in Figure 8 between OP8660’s voltage and current channels and FESTO’s hardware.

• Import project “DC_BUS_REGULATION_OP4510_OP8660.zip” in
• Figure 9 presents the SIMULINK console generated by RT-LAB while executing DClinkRegulation_Inverter8857_OP4510.slx. The SIMULINK console will allow users to enable and configure the operation of the demo and monitor the system waveforms. Before proceeding to the next step, make sure that the toggle switch Inverters Enable in the console is in the 0 position. The controls in the console will allow user to:
• Select the data source for the demo through the toggle switch Reference Control:
  • 1=> The model will run a simulation of a DC-bus control
  • 3=> The model will control the actual FESTO hardware to regulate a DC-bus
• Enable/disable the 8857 inverter to regulate the DC bus to the selected set-point through the toggle switch Inverters
• Set the desired voltage set-point through the DC-link reference control. The recommended voltage range goes from 80 to 120[V]. FESTO's 8311 resistive load is connected at the terminals of the DC-link and the voltage must not exceed 120 [V] so as not to surpass the nominal power of the

• Turn ON the 8525 power source: use 8525’s voltmeter and variable voltage knob to establish a phase to neutral voltage around 40 [V] RMS. Make sure the voltmeter’s selection knob is set to either AC 4-N, AC 5-N or AC 6-N. The phase-to-ground voltage of 40V [RMS] corresponds to a maximum phase-to-phase (instantaneous) value of Vt=100 [V].
• To adjust the required voltage user can also employ SIMULINK’s 

  console, making sure that the signal Vt (graphically available through the Monitor scope and numerically through the Vt RMS display) has a value close to 100 [V].

Figure 5.9 Console for the DClinkRegulation_Inverter8857_OP4510.slx mdl demo as the model runs.

1. Make sure the Reference Control has a value of 3, so the model can receive the voltage and current measurements from the hardware and the DC-link regulation can be
2. Make sure the inverter is properly connected to the 24 [V] AC output from the 8525 power source, as shown in section 4.2. User can now turn ON the 24[V] AC supply to feed the inverter.
3. Toggle the Inverters Enable switch to 1. The DC-bus will be regulated to the specified set-point. User will be able to verify the operation of the DC-bus regulation by a) Changing the DC reference as the resistive load is kept constant, as shown in Figure 5.10; b) Changing the resistive load as the DC link reference remains constant, as shown in Figure 11; c) Combining both a) and b).