代做Simulation of Buck Converters Using PSIM代做Python语言
- 首页 >> Algorithm 算法Department of Electrical Engineering
Simulation of Buck Converters Using PSIM
1 Objectives
The purpose of the experiment is to understand a circuit simulation package – PSIM (Power Simulation), and use the programmes to study and analyse power electronic circuits. PSIM has the characteristics of high simulation speed, high accuracy and friendly user interface, which provides a powerful simulation environment for power electronic circuit analysis, control system design and so on. The following sections will show you how to construct a Buck converter and a Full-Bridge inverter and how to use PSIM to study its performance.
2 Apparatus/Software
(1) IBM PC or compatible computer
(2) Microsoft Windows 7 or newer versions
(3) PSIM
3 Procedures
The workstation is an PC or compatible computer with Windows 7 or newer versions installed.
3.1 Install PSIM
(1) Download PSIM Demo Version at https://powersimtech.com/products/psim/psim-pricing- and-licensing/download-demo/ ;
(2) Select “Skip. I will register later” during the installation.
3.2. Creating Project
To begin with, open this software and set a new project. The procedures are as follows,
- Click “File >> New Project”
Then, create a name and choose the project location. Click “OK” .
A blank project will be created successful.
3.3. Creating Schematic Diagram
Schematic diagram can be constructed in the main window of the programme. The procedure for constructing a schematic diagram for simulation in PSIM are in the followings:
- Search components in “Library Browser”(a) or “Elements” menu (b) or The bottom menu bar (c).
(a) (b)
(c)
- Select the component and pull it to the main window for placing it in the diagram.
- Make connection between components by clicking a junction of a component, pull the line to the junction of another component.
- Set parameters or values of the components by double clicking.
- Set the Current Flag to 1, the current of this component can be viewed in the SIMVIEW.
- Place Simulation Control component to set the simulation time step length, total time and so on.
NOTE:
The PSIM demo version limits the maximum number of data points to 6000, so if possible, please set the simulation time step length as small as possible to display a longer simulation time.
- To delete a component or a line, select it and press “Delete” key on the keyboard
3.4. Simulation
Operation of the circuit in the created schematic diagram can be predicted with simulation using
PSIM. The procedures are shown as follows,
- Sketch circuit diagrams as below,
- For carrier wave setting, you can set its values according to the picture below.
- Save the work before running the simulation.
- Click “Run PSIM Simulation (F8).
- The progress bar below the page shows the simulation progress.
- After the simulation is completed, click “Run SIMVIEW” to view the waveform.
- Select the variable(s) you are interested in to view its(their) waveform(s).
4. Buck Converter
Buck converter is a popular DC/DC converter for which the output voltage can be stepped down. One of the most useful applications is the switched mode power supply that has the advantages of high efficiency and small size.
The major components of a Buck converter include a semiconductor switch (e.g. IGBT), a free- wheeling diode, an inductor and an output filtering capacitor. The control circuits include a DC voltage source, a triangular-wave voltage source, a voltage comparator and an on-off switch controller to interface between the control circuit and the power circuit. All these components can be found in ELements.
4.1. Buck Converter in CCM
4.1.1. Open-loop Control of Buck Converter in CCM
Construct a circuit diagram of the buck converter with open-loop control as shown below. Specifications of the circuit are:
. Input voltage is 100V.
. Switching frequency is 5kHz.
. Output voltage is 50V.
Getting inductors, capacitors and resistors from Elements, the keyword for searching of the components are L, C, andR, respectively. Resistance of load is 5Ω. L1 is 1mH. C1 is 100uF.
Performing the transient analysis, the recommended time step and simulation time that are 10µs and 10ms, respectively. It is noted that entering units of parameters is not necessary. Observe the waveforms and check if the end time of the simulation is appropriated for obtaining simulation results. If not, enter a new total time and repeat the simulation.
Expected Results:
4.1.2. Closed-loop Control of Buck Converter in CCM
Construct the closed loop control Buck converter as shown below with PSIM. The specification of the closed-loop control Buck converter is the same as the open-loop control converter except that the modulation signal is replaced by a feedback control circuit, not a constant DC voltage source.
Closed loop control of a buck converter
The reference output voltage is 50V. Voltage sensor and current sensor are adopted to get the values of current and voltage to facilitate the closed-loop control. The lable (IL, Vout) can be found at:
H(s) is s-domain Transfer Function.
K is proportional blcok.
You can try to modify the parameters of the PI and P controllers to improve the performance and control the output voltage. Change the end time of the simulation to an appropriate value for transient analysis to obtain a steady state output voltage. Observe the simulated output voltage.
Expected Results:
It can be seen that the transient response of Buck converter with closed-loop control is faster than that with open-loop control.
4.2. Buck Converter in DCM
When the load is very low, the inductance current will be discontinuous, that is, the Buck converter runs in DCM.
4.2.1. Open-loop Control of Buck Converter in DCM
The specification of the Buck converter in DCM is the same as that in CCM except that the load resistor is changed to 40Ω .
In DCM, the relationship between output voltage Vo and input voltage Vin does not satisfy the formula: Vo = D * Vin, and the output voltage is affected by the load. Therefore, when the duty cycle is set to 0.5 under open-loop control, the output voltage is not 50V. The results are as follws.
4.2.2. Closed-loop Control of Buck Converter in DCM
The closed-loop control can make the output voltage constant regardless of the load change.
The specification of the closed-loop Buck converter in DCM is the same as the closed-loop control converter in CCM except that the load resistor is changed to 40Ω and K of proportional block is changed to 0.01.
Expected results:
5. The Report
The report should include simulation results of output voltage, inductor current, MOSFET current of each case. Answering the following questions:
i) Identify the critical condition for the CCM and DCM.
ii) Is the steady-state voltage the same with the calculated results? If it is not, why?
Bonus: Suggest what improvements can be done to achieve a better steady-state waveforms.
The waveforms and circuit can be obtained by using PrtScn or Snipping Tool to capture and paste to any Paint tools.