Pulse Width Modulation Interface Description
5. Three level PWM modulation simulation in java 5.1 Program description The presented program consist of applications or applets on the Web, pursuing simulation vector modulation methods used to control for three-level converters with pulse width modulation. This allows you to quickly generate and verify data using the graphical interpretation - the dynamic waveforms sinusoidal and rectangular, vector space and bar charts. Due to the simple service, the program can be a teaching aid in the learning (a desire to understand the processes control for three-level converters) and ancillary material to be affecting the efficiency of the performance of tasks performed at the laboratory. The first applet is devoted to multicarrier modulation, second to Space Vector Modulation. The software packages include: effective program editor with a graphical support to generate the waveforms, graphic simulator of modulation methods for controlling converters, including: o implementation of multicarrier modulation o implementation of Multilevel Space Vector Modulation (ML-SVM) space vector divided by sectors and regions, presentation of the various fillings vector (bar representation of data), graphics, dynamic interpretation switching times in the form of rectangular waveforms. o analysis of the impact of additional sources of energy for the circuit parameters, o analysis of the impact for passive electrical circuit (resistance, inductance coils) on the current distribution of three phase converter, o analysis of the impact for non-linear elements (diodes) on the circuit parameters system switching mode of converters control (manual / automatic), graphic controller for automatic control work converters (signaling mode of operation: on / off), interpreter of the data input - the detection of irregularities related to the data.. The main application window is shown in fig 5.1. We can divide them into the following panels fig 5.2. 1.. Managing data panel This module is responsible for the transmission of data input (processed chain) to other functional blocks. Works closely with the interpreter, who controls the process of entering information into the system 2. Space Vector panel. The module is responsible for the correct functioning of the dynamic space vector and interpretation of vector fills and switching times. 3. Graphic interpretation panel. Block graphic interpretation realizes sinusoidal modulation, and allows for an analysis of the impact of the various parameters in whole converter system with load. 4. Additional information panel. The panel includes basic information about the application name and version.
. Fig 5.1. The main application window Panel 4 Panel 1 Panel 3 Panel 2 Panel 1 Fig 5.2 The division of applications for individual blocks (modules)
5.2. Description of the user interface As an example we take the Space vector modulation applet. User interface of this applet is divided as follows (fig 5.3): 1. Bar allows you to select the appropriate mode (auto / manual) 2. The choice of laboratory analysis 3. The screen showing the sinusoidal modulation. It presents three sine waveforms shifted in phase by 120 degrees. 4. Scheme showed the available shapes. 5. Description of three phase sinusoidal waveforms. 6. Text box determining the vector amplitude 7. Text box determining the vector phase 8. Button to run the simulation for three-level converters 9. Approves or modifies data. 10. Button to stop the simulation. 11. Indicators determining the mode of control two-level converters 12. Vector space divided into sectors and regions 13. Bar allows the reading of the relevant numbers of sectors and regions 14. Bar graphs showing the fulfillment of the three vectors used for the modulation (in percent). The sum of filling is 100%. 15. Graphs showing switching times in three phases in one sampling time. Fig5.3 Description of the components of the user interface - SVM method
5.3. The functionality of the program The program allows you to carry out research for four issues. The most important feature of the system is the possibility of entering data, to make modifications to variables, the work carried out in two modes (auto / manual). You can also watch waveforms, whether the behavior of vectors in space. An application is divided into different groups: o Space Vector Modulation (without watching current), o SVM with RL load, o SVM with RL load and additional voltage source. o SVM with RL load and nonlinear elements (diodes). 5.3.1. Space Vector Modulation The topic of this section is the implementation of SVM method. The user of the program may carry out a simulation, which will generate adequate waveforms rectangular depicting the distribution of vector, or its individual fillings. Fig 5.4 Description of the procedure performed during the SVM method implementation
The procedure performed during the SVM method implementation consist of the following points (see Fig 5.4) 1. The first step starts the simulation Space Vector Modulation is the choice of operating mode control converters - switching program in the state automatically. 2. Then select the appropriate value of amplitude and the angle of the vector. 3. Downloading data is via the SET button;. For each value should be modified to confirm your changes. The next step is to run simulations that occurs when you click START button. To stop the running waveforms the button STOP is used. 4. On the screen we get a dynamic modulation, which is generated by converter reference voltage shifted in phase by 120 : 4 2 U 1 = A*sin( ωt + π + ϕ), U 2 = A*sin( ωt + π + ϕ) 3 3 U 3 = A*sin( ωt + ϕ) 5. At the bottom of the main window we receive a rectangular shapes, which illustrates the distribution of switching time of vectors. 6. Running the application through the START ; creates vector rotation in space, and thus change the sector and region. 7. The corresponding position vector associated with various fillings change. Each region corresponds to three values of vectors determining triangle vertices restricting the region. The total sum of fillings, three bar graphs, equals the total completion - 100%. 5.3.2. RL circuit In the case of RL load, we perform the analysis of the passive elements effects (resistance and inductance) on the three-level converter parameters (shape of currents). The way to carry out such a study has been shown in Figure 5.5. 1. The first step of analyzing the passive elements influence on the shape of electrical currents and voltages in the circuit is to select the appropriate value induction coils, resistance and voltage. 2. In the second step it is necessary to enter the value of amplitude and the angle of the vector - the same as in the case of Space Vector Modulation. Start ; starts the simulation, SET ; - approve the input, STOP ; - stops to generate waveforms. 3. On the screen, receive voltage and currents waveforms, which shape depends on the parameters selected in step 1 and 2
Fig 5.5.Analisyssys of influence of RL parameters 5.3.3. RL circuit with additional voltage source Another feature is the ability to carry out the analysis of the impact of additional voltage in the system. A description of the procedure was presented in Figure 5.6. 1. At first should be interesting to set resistance, inductance and voltages (U1 and U2) values. 2. The next step is to select the appropriate value of amplitude and the angle of the vector - the same as in previous case. 3. The results are two dynamic waveforms: current and voltage.
Fig 5.6 Influence analysis of additional voltage sources. 5.3.4. RL circuit with nonlinear elements (diodes). The last element of the built-in program is the possibility of analyzing the effect of non-linear elements (diodes) in the converter system Figure 5.7. Activities in the course of this analysis are exactly the same as in the case study of the impact of additional sources connected to the circuit.
Fig 5.7 Influence analysis of non-linear elements in circuit with RL elements 5.3.5. Multicarrier Modulation. In order to watch the graphical presentation of the method with carriers, we are using the second applet. This applet has the similar appearance to previously described, and similar strategy of the service. The main difference consists in giving two sliders, letting change the carrier s frequency (FREQUNCY) and amplitudes of reference voltage (AMPLITUDE). For three-level converter control we are choosing the option named Multicarrier.. Using these two sliders we can receive different shapes of the reference voltage which in this particular case were indicated with values 2, 1 and 0 (see fig. 5.8).
Fig. 5.8 Presentation multicarrier PWM method for three-level converter 5.4 Summary of program for three-level converters The aim is to show the distribution of software operation, which will allow for the simulation methods of vector and multicarrier control three-level converters. This application has several options, which may be an ideal material support, used for work related to the examination and analysis of 3-level converters. The program allows you to quickly obtaining and verifying data with graphical interpretation - dynamic waveforms, the space vector and bar charts. With the main advantages of an application, you must recognize the simplicity of use and the ability to run the program on different system platforms. In the case of the applet is also the ability to view the results of research into the available Internet browsers.