In this tutorial, I will explain you the working of controlled rectifiers and how we can implement them using MATLAB Simulink. Rectifiers are one of the very basic circuits of electronics however, controlled rectifiers are those whose output waveform can be controlled using electronic switches by controlling their firing angles. At the start a comprehensive introduction of controlled rectifiers is provided along with the types and uses of these. After that the circuit of controlled rectifiers is implemented on MATLAB’s Simulink. At the end you are provided with a simple exercise to perform it on your own regarding the concepts discussed in the tutorial.
Introduction to Rectifiers
Controlled rectifiers are the basic components of power electronics. As the name suggests in a controlled rectifier we can control the shape of the output waveform of the rectifier with the help of switches. The waveform shape will depend on the firing angle of the switch connected to the bridge.
Types of rectifiers
Controlled rectifiers can be classified into two major types
- Half wave rectifier
- Full wave rectifier.
Half wave rectifier
Unlike simple half wave rectifier, half wave and full wave-controlled rectifiers depends on the number of switches used in the circuit. The pulses given to the switches have a specified pwm and that pwm will decide the shape of the rectified output wave, and the pwn of the pulse is also used to define the firing angle of the rectifier as you will see shortly.
Full wave rectifier
A full wave rectifier however uses both the positive and negative parts of the AC wave to rectify. Again in this case we use switches with gate pulses to be used as the firing angles of the rectified output. The rectified output will not be a pure sinusoidal waveform although it will be a distorted sine 0 output before sinusoidal and rectified sine wave after firing angle of the pulses in the gate input of switches.
controlled rectifiers in Simulink MATLAB
In the model, I am going to discuss with you we are going to design a Half wave controlled rectifier and the designing of full wave controlled rectifier is left as an exercise for you.
Open MATLAB to create a model and then open simulink by clinking on the icon present in the main page of MATLAB or by typing simulink in the command window of MATLAB. Once the simulink window pops up , click on the block named as blank model as we have been doing in the previous tutorials. After that open the library browser and in the search bar of library browser search “Pulse generator” as shown in the figure below, and press enter.
Figure 1: Searching block
- After searching the only block in the search result will be the source “pulse generator” as shown in the figure,
Figure 2: Pulse generator
- Drag and drop this block on the simulink model or add it to the simulink model by right clicking on it and selecting add to model as shown in the figure below,
Figure 3: Adding block to model
- Lets’ first add all the sources to the model and after that we will move to the main components. The power to the rectifier will be provided by the AC Voltage source. Lets’ now locate the position of the AC Voltage source in the library browser. In the library browser select the block simscape and then select Power System as shown in the figure below,
Figure 4: Power system
- In the power system block, select the block named Specialized Technology as shown in the figure below,
Figure 5: Specialized Technology
- From this block, select fundamental blocks as shown in the figure below,
Figure 6: Fundamental blocks
- From fundamental blocks select sources
Figure 7: Sources
- This is the place were all the power sources reside, select AC Voltage source from inside of that block as shown in the figure below
Figure 8: AC voltage source
- As we have done previously add block to model do the same in adding this block to model. Now go back to the fundamental blocks model we encountered in our way here and from that block select the block named power electronics as shown in the figure below,
Figure 9: Power electronics
- From this block select the block of thyristors (used in place of diodes in controlled rectifiers) and add block to model as shown in the figure below
Figure 10: Thyristors
- Go back to the fundamental block and select the power gui as shown in the figure below, and add it to the model. The purpose of this block is to provide a kind of source code to the blocks used from power section.
Figure 11: Power gui
- Again from the fundamental blocks select measurement block as shown in the figure below,
Figure 12: Measurement block
- From this block select the Voltage Measurement block and place two such blocks on the model, one for input measurement and one for output as shown inn the figure below,
Figure 13: Voltage Measurement
- Again go back to the fundamental blocks and select the Elements block (for placing load) as shown in the figure below,
Figure 14: Elements block
- From this block select the series RLC branch, so we can test our circuit for any kind of load, and place it to the model as shown in the figure below,
Figure 15: Series RLC branch
- The last thing we need to place is the scope so we can see the waveform of the rectifier at the output. Search scope in the search bar of the library browser and add it to the model as shown in the figure below,
Figure 16: Scope
- Now we are done with placing components and lets move toward the model and place the components accordingly as shown in the figure below,
Figure 17: Place component
- Connect the thyristors in the form of bridge for full wave rectification as shown in the figure below,
Figure 18: Bridge
- Connect the power source in the same fashion as we have done in case of simple full wave rectifier and also connect the load. Now connect the pulse generator to the input pin g of the thyristor and also connect voltage measuring blocks at input and output as shown in the figure below,
Figure 19: Pulse generator connected
- At the output connect the scope, but first we need to do some changes. Double click on scope, then select file and change the number of input ports to 2 as shown in the figure below,
Figure 20: No. of input ports
- To the input ports of scope connect the input and the output of the controlled rectifier as shown in the complete block diagram below. Also, double click on the RLC branch and change it to only Resistors and set its value to 400.
Figure 21: Complete block diagram
- Now set the parameters of the pulse generator as shown in the figure below,
Figure 22: Parameters of pulse generator
- Also we have to change the parameters on the input AC Voltage Source as shown in the figure below,
Figure 23: Source block parameters
- Change the layout of the scope to two blocks by changing the properties of scope as shown below,
Figure 24: Changing layout
Figure 25: Selecting 2 blocks for layout
- Now run the model using the run button and adjust the scale of the scope. The output of the full wave controlled rectifier is shown in the figure below,
Figure 26: Output
- You can change the angle of control by changing the phase delay in pulse generator parameter.
Exercise:
- Perform the analysis on full wave controlled rectifier using MATLAB’s Simulink. It would be much simpler than the one performed in this tutorial.
(Hint: Number of diodes to be used will be two)
How can view output vtg value