Lab 1: Simulink Introduction The purpose of this lab is to give you a basic idea as to how simulink looks and operates. At the end of the lab, you are to print a schematic as well as your output and the bode plot generated. Please name and label them “ECEN405 Lab 1: Simulink Introduction”. Open matlab, along the top under the “home” tab you will find the Simulink icon. Alternatively, type “Simulink” into the command window. Fig: 1 You should now have the “Simulink Library Browser” open. There are a number of libraries listed here, we will be using “Simscape SimPowerSystems” and a few elements from the basic “simulink” library (note: libraries such as SimPowerSystems do not connect directly to other libraries eg SimElectronics). Create a new model by selecting the icon below from the top of the “Simulink Library Browser”. Save model as “LabOne” Fig: 2 We need to change the settings to suit our simulation (this is not always the case). The cog icon at the top of the model will take us to “Model Configuration Parameters”. We want the stop time to be 0.1 as we only need to observe the model for a short time. We will also need to set the Max step to 1e-6. This is because we will be switching at 20kHz and if the max step is too high, you can lose some detail. Fig: 3 Now we will begin creating the model. Add a subsystem from the “commonly used Blocks”, and name it PWM. Subsystems are good for keeping a model organised, especially when you have a busy circuit. A subsystem is another layer which can have a sub circuit of your system inside, with inputs and outputs. Although we are not using it in this lab, by right clicking on the subsystem, you can create a “mask” where you can pass parameters into the subsystem without entering it. Fig: 4 To enter a subsystem (when it does not have a mask) double click on it. In this subsystem we will create our PWM generator. First add a triangle wave generator which you can find by typing “triangle generator” into the search bar at the top of the libraries (select the one from simscape). Once it is in your model, double click on it and change the frequency to 20000Hz. In the same way, add a sum block, double click on it and change one of the + signs to a –. Add a Relay block (from simulink-1),a mux and a scope (both can be found in the commonly use blocks library). Double click on scope, go to parameters, in “general” change the number of axis to 2. In history, uncheck the “Limit data points to last” box Fig: 5 Now connect the above blocks as shown below (Fig 6), leave the scope open to one side Fig 6 Go back to initial tab Add sine wave generator and set the frequency to 50Hz (not 50hZ is 314.16 rad/s) and connect the sine wave generator to the PWM tab and hit run (play sign at the top of the screen). If you want a more intuitive feel of what’s happening, try changing the frequency of the sine to a much higher one (eg 5000Hz) and zoom in (be sure to change it back to 50Hz). Below is an image of a higher frequency sine wave compared to the triangle wave. Fig: 7 We will now add 2 Mosfets from Simscape/SimPowerSystems/Specialized Technology/Power Electronics Double click on the Fet and change Ron to 20e-3 and uncheck “Show measurement port” Fig: 8 Add 3 RLC branch blocks from Simscape/SimPowerSystems/Specialized Technology/Elements Double click on one branch, change “branch type” to “R” and resistor value to “4”, and change the name of the branch to “Load” Change the next RLC block to RL, with a series resistance of 0.077 Ohms and Inductance to 560uH. The last leg should be RC with R = 0.022 Ohms and a capacitance of 47uF. Fig: 9 In the same library, find Ground and add it to the simulation. From Simscape/SimPowerSystems/Specialized Technology/Measurement add a voltage and current sensor. And from the Simscape/SimPowerSystems/Specialized Technology/Electrical Sources library, add the DC voltage source and set it to 40V and connect as follows Fig: 10 Add another subsystem, name it “Inv”, connected as shown below. Constant blocks can be found in the “Commonly Used Blocks”. Fig: 11 Now connect the high side Fet to the output of the PWM and the low side Fet to the output of the Inv block. Libraries from Simscape often need solvers, for the case of SimPowerSystems we need to add a “powergui” found in Simscape/SimPowerSystems/Specialized Technology Now add a scope, following the same procedure as we did above (2 inputs, uncheck limit data), your model should look like this – Fig: 12 Now if we replace the sine wave input with a DC voltage ref we have a buck converter. However, we will now make this model a full bridge. Fig 13 shows the full bridge layout, you have all the components to implement this except the product block which can be found in the “commonly used blocks” library. Once connected, run the simulation and ensure the response is similar to fig 13 Fig 13 You can also analyse the response of a system by right clicking on the line coming out of the PWM block, on the drop down menu, going to “linear analysis” and selecting “Input Perturbation”. Repeat this on the output of the Voltage sensor but instead of selecting “Input Perturbation”, select “Output Measurement”. Then click “Analysis” from the top menu, “control design” and “Linear analysis”. In the “Linear Analysis tool” window, Change the “Plot Result” to bode and hit “Linearize”. Fig: 14 Now print the output scope, the schematic of the full bridge and the bode plot and hand them in.
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