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Video: 4.0.2. Analog Outputs
Last Updated 11 months ago


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TRANSCRIPT

00:00:00

Hello and welcome back. In the previous lesson, we mentioned that the last step in setting up  

00:00:06

a C-HIL system involves adjusting interface related settings of the model. In this lesson,  

00:00:10

we will talk about Analog Output settings and how they can be set up in Typhoon HIL Control Center. 

00:00:17

For analog outputs, adjusting interface related settings means mapping the necessary signals from  

00:00:22

the model to the appropriate AO pins of the HIL device and setting the correct scaling and offset. 

00:00:28

In this lesson, we will demonstrate a scenario which considers devices under test for which  

00:00:33

the voltage and current capabilities of the HIL device are sufficient, and interfacing  

00:00:38

is done through an interface board.For devices under test which require  

00:00:42

higher voltage or current levels than what the HIL device can provide,  

00:00:46

such as relays and some types of controllers, interfacing is done through a HIL Connect device.  

00:00:52

This scenario will be covered in future courses. You can find more information about this in  

00:00:57

the How to scale simulated signals for a C-HIL interface how-to guide in the Materials section. 

00:01:02

Now, let s talk about scaling.The ratio between the range of the  

00:01:07

variable in the simulation and the voltage range of the HIL device outputs determines the scaling  

00:01:13

required for any given analog output signal.The voltage range of the HIL device outputs  

00:01:19

used in the denominator of this equation should match the interface board input and  

00:01:23

controller specifications as required.Let s look at the following example. 

00:01:28

Here, we see the three main parts that comprise a C-HIL setup. 

00:01:32

In our simulation, let s assume that we are measuring an alternated sinusoidal signal  

00:01:37

with a maximum amplitude of 120 volts.When determining the scaling factor,  

00:01:42

it is important to consider the largest measured value which can appear in the simulation and needs  

00:01:48

to be seen by the device under test an example of this would be to consider transient events,  

00:01:54

where we can have simulation values significantly higher than the nominal ones. 

00:01:58

The scaling factor must ensure that signals of interest produced by simulation do not  

00:02:04

reach HIL device saturation limits and end up clipped at the output. 

00:02:07

Next, we have the Interface board with its rated Analog Inputs and Outputs. 

00:02:13

And finally, we have the controller with its rated Analog inputs. 

00:02:17

In this case, notice that the interface board was designed in such a way so that its outputs match  

00:02:22

the controller under test. However, the rated analog input voltage range of the interface board  

00:02:28

is given as -5 to +5 volts. Therefore, instead of considering the default HIL device output  

00:02:36

specifications, -10 to 10 volts, we will take the interface board inputs into consideration  

00:02:42

when choosing the denominator of the equation.Considering this, a scaling factor of 24 is  

00:02:49

calculated to capture all possible values of the simulated signal. 

00:02:52

In the previous slide, notice that we were considering an interface board with a given  

00:02:57

predefined characteristic. By looking at its Input and Output voltage ranges, we see that  

00:03:03

in this case the Interface Board introduces its own scaling and offset. We refer to this scaling  

00:03:09

as the voltage gain of the board, which in this example is given by setting Gv equal to 0.3. 

00:03:16

The gain at the interface board is a parameter defined at the hardware level of the board. It  

00:03:21

is a part of its specification and can vary for different interface boards. In case no interface  

00:03:27

board is used, voltage gain is equal to 1.As an alternative to the calculation shown before,  

00:03:33

we can use the interface voltage gain to calculate the scaling directly from controller input  

00:03:38

specifications, with the following equation:Here, the range of the simulated variable  

00:03:45

is divided by the analog input voltage range of the controller and multiplied  

00:03:49

by the voltage gain at the interface board.Let s calculate the scaling factor again. 

00:03:55

We see that we have calculated the same value as in the previous equation. We will see how  

00:04:01

different scaling values influence the signals measured on the HIL device outputs later on. 

00:04:06

In addition to scaling, an offset may be required for both AC and DC signals so that the signals  

00:04:13

match the controller ADC specifications. For AC signals, the offset is usually used  

00:04:18

to represent the negative half of the cycle as a set of positive values. For DC signals,  

00:04:23

the offset can be used when measuring a DC value which can change its sign during  

00:04:28

simulation runtime, such as for charging and discharging currents in a battery system. 

00:04:32

We can define scaling with the following equation.Here, the offset is equal to the voltage measured  

00:04:40

at the analog outputs of the HIL device that represents the value of 0 in the simulation. 

00:04:45

In the previously shown example, we see that the AC signal can be fully represented  

00:04:51

on the HIL Device IOs using only scaling therefore, the offset to be defined in the  

00:04:56

Analog Output settings is equal to zero.In this example, we can notice that the  

00:05:03

Interface board will later include the required offset to match the controller specifications. 

00:05:07

Now that we know how to calculate the scaling and the offset, let s  

00:05:11

look at how they can be set in Typhoon HIL Control Center. Let s open Schematic Editor. 

00:05:16

In this example, an IGBT leg is connected to a resistive-inductive load and is operating in an  

00:05:23

open-loop, with a sinusoidal modulating signal.As you can see, the IGBT leg is currently  

00:05:29

controlled from inside of the model. In an actual C-HIL setup, the gate drive signals  

00:05:34

from a real controller would be connected to the digital inputs of the HIL device and  

00:05:39

used to drive the switches in the IGBT leg.In addition, the measurements of interest in  

00:05:44

the model have to be assigned as HIL device analog outputs and routed to the controller  

00:05:49

through the proper interface board.The first method of setting analog  

00:05:53

outputs is by using the Output Settings component found in the System Library. 

00:05:58

The Output Settings component enables signal assignment to analog or digital outputs of  

00:06:03

HIL devices within the Schematic Editor model. Here, we can also set some additional settings. 

00:06:09

Let s assume here that the variable of interest is the load current and let s add this signal.  

00:06:14

Using the Name combo-box, we can select the Analog Output pin to which we want to assign the signal. 

00:06:21

In the previous theoretical example, we showed how we can calculate scaling and offset for  

00:06:26

voltage measurements. When it comes to current measurements, these signals are also represented  

00:06:31

as voltages on the outputs of the HIL device, so the exact same procedure shown before applies. 

00:06:36

Let s consider that the currents range from +/-30 amperes in this model. Assuming we have  

00:06:42

the same interface board detailed in the previous example, whose input range is from +/-5 volts,  

00:06:48

we calculate a scaling value of 6. Since the load current is a sinusoidal AC value, the value of  

00:06:55

offset will be zero. Notice that we can also limit the voltage range independently for each analog  

00:07:01

output. Let s keep that unchecked for now.When it comes to Analog Output settings,  

00:07:08

the Hardware Settings tab in Model settings offers a few additional settings. 

00:07:14

As we can see, we have an option to Limit all the device analog outputs to +/- 5 V. For now,  

00:07:21

we will also leave this option unchecked.By checking the Reset analog/digital outputs  

00:07:26

on simulation stop option, the analog and digital outputs can be forced to reset to  

00:07:31

0 when the simulation stops. Otherwise, the outputs will report the last recorded value. 

00:07:37

Now, let s compile the model and go into HIL SCADA. 

00:07:42

Once the outputs are set and the model is compiled and loaded,  

00:07:46

the Analog and Digital Outputs in the Model Settings section in  

00:07:50

SCADA will be set according to the Output Settings parameters defined in the model. 

00:07:57

Signals that were already defined in Schematic Editor using the Output  

00:08:01

Settings component are locked and marked by an icon on the left. You can unlock them and  

00:08:06

modify the settings as desired. However, be aware that whenever you reload the model,  

00:08:12

these modifications will be replaced back to the settings defined in Schematic Editor. 

00:08:16

The best practice is to define output settings in Schematic Editor. Still, if necessary,  

00:08:22

you can override them in HIL SCADA.Let s now check how changing Analog  

00:08:27

Output settings manifests on the outputs of the HIL device in practice. 

00:08:31

To demonstrate this, the HIL Device is disconnected from the C-HIL setup,  

00:08:35

and we ve connected a PC Oscilloscope directly to the AOs of the HIL Device. 

00:08:42

First, let s see how different scaling factors impact the output signal. 

00:08:51

Now, let s reduce the scaling factor until the output signal goes over the HIL device limits. 

00:09:00

Since the rated output voltage range of the analog outputs of the HIL device is from -10 V to +10 V,  

00:09:07

we can see that the outputs ended up being saturated when exceeding these values. 

00:09:12

Now, let s get back to the calculated scaling factor and set different values of offset,  

00:09:17

to see how our signal changes. 

00:09:24

Previously, we have mentioned the option to limit output voltages of the HIL device. 

00:09:29

In both Schematic Editor and SCADA, we can customize these voltage limits by selecting  

00:09:35

the appropriate checkbox. In the case of our example, we will set these limits to minus  

00:09:40

and plus 5 volts to ensure compliance with interface board specifications. Right now,  

00:09:45

we will be setting them from HIL SCADA.Now, let s decrease the scaling factor once again. 

00:09:56

We see that the signal has now been clipped at our set limit. 

00:10:00

In this video, we ve shown you how you can set up  

00:10:03

Analog Output settings for your C-HIL applications. Thank you for watching!

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