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1 Schematic Diagrams
2 Test Setup Specifications
3 RT-LAB Model Descriptions
- 3.1 User Interface Dashboard
- 3.2 Computation Subsystem
4 Sensor Calibration

To practically demonstrate the operation of PELab-6PH, a generic model is developed that allows the user to test the power modules of the unit in a stand-alone mode of operation. Through this model, the user is able to control the modulation index, fundamental frequency, switching frequency besides observing all the measured signals and faults.

Schematic Diagrams

Figure 9 presents the circuit diagram of the PELab power modules and measurements in the stand-alone mode. As demonstrated, the DC links of both modules are connected to an ITECH power supply to feed the loads connected on the AC side of the converters. The external voltage and current measurements are also connected to the power modules for monitoring the input DC current, as well as the line voltages.

Figure 9. Schematic diagram of the test bench configured for the example model

The necessary power and sensor connections with respect to the model schematic are illustrated in figure 10. As shown, a single unit ITECH power supply is used to feed both power modules. The cut-off switches are used between the output of the modules and the loads. The three-phase load banks are configured using resistive heater fans. The external voltage and current sensors are also involved in demonstrating their performance. Accordingly, V1 and V2 are used to measure the first and second line-to-line voltages of the first module, while V3 and V4 measure the same voltages of the other module. The external current sensors, including i1 and i2, are respectively measuring the input DC current of module1 and module2.

Figure 10. Power and sensor connections on the back panel

Test Setup Specifications

The model and test setup specifications are presented in table 8.

Table 8. Model and test setup parameters

Parameter	Unit	Value

Parameter	Unit	Value
Maximum DC voltage	Volt	500 V
Maximum DC current	Ampere	15 A
Maximum switching frequency	Hertz	50 kHz
ITECH voltage rise time	Second	15 s
Switching dead time	Micro second	0.6 us
Control sampling time	Micro second	20 us
Maximum load power	Watt	5 kW
Simulator model	-	OP4512
Bitstream model	-	TE0741_3-EX-0001-3_2_10_45-IOConfig1_4OP8110SFP-01-01.bin

This model is developed and tested on an OP4512 simulator with the I/O configurations shown on the left column in figure 11. It can be used as it is for an OP4610XG simulator with a similar I/O configuration.

If the power supply is not ITECH make sure that the voltage is not stepped up immediately after enabling the output. Otherwise, it will damage the DC-link capacitors. Accordingly, use a power supply with a controllable slew rate or voltage rise time.

RT-LAB Model Descriptions

Figure 12 depicts the overall view of the computation and user interface subsystems that are used to control and monitor the PELab unit in the stand-alone configuration.

User Interface Dashboard

The user dashboard shown in figure 13 runs on the user PC. This interface allows the user to control the modulation index, adjust the fundamental frequency, set the switching frequency, enable or disable the PWM signals, and monitor the measured analog signals besides the fault flags.

The following table details the function of each subsystem block and scope exist in the user interface. Please note that the control and monitoring features of both modules in the user interface are identical.

Table 9. Detailed description of the user interface subsystem

Block	Function

Block	Function
	Receives the fundamental frequency and the modulation index and then transfers them to the simulator to generate the switching reference signal
	Sets the switching frequency from 2 kHz to 50 kHz The switching frequency must be lower than 50 kHz if the output current is more than 8 A
	Enables or disables the PWM signals
	Provides the instantaneous value of the voltages measured by the internal and external sensors
	Provides the instantaneous value of the currents measured by the internal and external sensors
	Plots the back panel voltage measurements
	Plots the traces of the back panel current measurements
	Provides the voltages and currents that are related to the first power module
	Provides the voltages and currents that are related to the second power module
	Plots the reference signal that is generated based on the desired modulation index and fundamental frequency
	Provides the status of the fault flags

Computation Subsystem

The computation subsystem depicted in figure 14 runs on the simulator and communicates with the PELab unit through the digital and analog terminals. This subsystem includes four main areas, listed in table 10.

Table 10. Detailed description of the computation subsystem

Block	Function

Block	Function
	Generates the three-phase PWM reference signals, as well as the switching pulses for the first power module
	Generates the three-phase PWM reference signals, as well as the switching pulses for the second power module
	Receives the fault flags through the digital inputs
	Receives the measured signals through the analog inputs. Scaling (sensitivity) and offsetting of the analog signals is performed in this subsystem

Sensor Calibration

According to table 3 and table 10, each current and sensor has a scaling factor and offsetting bias that is considered in the “Analog Signal Conditioning and Offsetting” area of the computation subsystem of the PELab example model. As shown in figure 15, the sensitivity must be set based on the scaling factor of each sensor, while the offsetting bias can be tuned so that the best conversion accuracy is attained.

Specialized Solutions Documentation

Example Model