Space vector pulse width modulation SVPWM provides a better technique compared to
the other pulse width modulation techniques. This paper presents simulation and implementation of
SVPWM signal generation for driving three phase two level voltage source inverter VSI, also
proposes and analyzes a new switching sequence for generating an SVPWM. Simulation results are
obtained using the simulation package PSIM. and the inverter performance is evaluated in terms of
total harmonic distortion (THD). The model is experimentally implemented and verified on Arduino
Mega Atmega2560 microcontroller

Abdalla, Othman Hassan

English

SUST Journal Systems (Sudan Univ. of Science and Technology)

SUST Journal of Engineering and Computer Science (JECS), Vol. 19, No. 2, 2018   10  Space Vector Pulse Width Modulation Technique Applied to Two Level Voltage Source Inverter  Gussay Abdalrahman, Othman Hassan Abdalla, Mohamed Ismail Jibril, Ahmed A.Awad Electrical & Computer Department, Engineering Faculty, Karary University  othman313@gmail.com,   Received: 12/90/2018 Accepted: 12/29/2018  ABSTRACT- Space vector pulse width modulation SVPWM provides a better technique compared to the other pulse width modulation techniques. This paper presents simulation and implementation of SVPWM signal generation for driving three phase two level voltage source inverter VSI, also proposes and analyzes a new switching sequence for generating an SVPWM. Simulation results are obtained using the simulation package PSIM. and the inverter performance is evaluated in terms of total harmonic distortion (THD). The model is experimentally implemented and verified on Arduino Mega Atmega2560 microcontroller.  Keywords: Space vector modulation, Voltage source inverter, two- level inverter  لاصمختسم-   ةقرولا هذى .ةضبنلا ضرع نيمضتل يرخلاا قرطلاب ةنراقم لضفا ةجيتن ول  يغارفلا ييجتملا ةضبنلا نيمضت  ةاكاجملا حضوتتل يغارفلا ييجتملا ةضبنلا نيمضت ةقيرطل ميمصتلاو تاراشلاا ديلوروطلا يثلاث ريغمل  وذردصم ديجلا ىوتسملا يئانث ضرع مت اضيا . جمانربلا مادختساب ايقيقحت مت ةاكاحملا .يغارفلا ييجتملا ةضبنلا نيمضت ديلوتل حيتافملا نمازت ةقيرطل ديدج ليمحتوPSIM ءادلاا مييقت متو .ب وقيقحتو ةءانب مت جذومنلا .ةيمكلا تايقفاوتلا شيوشت ثيح نم ريغممل عون قيقدلا مكحتملا مادختساArduino Mega Atmega2560 .  INTRODUCTION Pulse width modulation is the process that used in sophisticated power electronics systems. which based on generating an analog signal from a digital source by control the duty cycle and frequency through turning the switches on and off at a fast rate. Space vector modulation is one of the most preferred PWM strategies today, because of it’s easier digital realization, best DC bus utilization and less THD in output voltages. Inverter means conversion of DC to AC power by using PWM techniques to get AC voltage (or current) output. These output waveforms are desired for many applications, in adjustable speed drives (ASD), uninterruptible power supplies (UPS), active filters, and second generation of flexible AC transmission systems (FACTS) [1-3]. With the development of microprocessors, SVPWM   became one of   the   most important PWM techniques for three-phase inverter   [4, 5]. This paper tries to provide all the necessary information required to design and implement practical SVPWM technique on a two-level voltage source inverter in a simplified format. Furthermore, compare the amount of THD for different switching sequences in space vector modulation. Power simulation package PSIM environment is used to implement and simulate the VSI and obtain the results of simulation in form of waves for voltage and current. Furthermore, the results are confirmed by the experimental hardware setup. VOLTAGE SOURCE INVERTER There are many sources of the DC voltage for VSI. The source may be a battery's bank, wind turbine energy, and solar photovoltaic cells. Furthermore, AC voltage supply after a rectifier to DC can be qualified as another dc voltage source [6, 7]. Voltage source is called as stiff if the magnitude of source voltage is not depending on the load connected to the source. In VSI voltage supply is considered as stiff at the input [8]. A typical schematic diagram of a two-level voltage source inverter is shown in Figure.1. Six switches (S1 to S6) are the power switches that SUST Journal of Engineering and Computer Science (JECS), Vol. 19, No. 2, 2018   11  make the output shape. The upper switches and lower switches are complimentary to each other [9].   Figure 1: Schematic diagram of two-level VSI  From Figure1, there is a possibility for eight structures of switching status can be configured in the two-level VSI as inserted in Table 1. Status (1) means one of the upper switches is conduct, and status (0) means one of the lower switches is conduct. The three digits in the status correspond to the legs (a, b, & c) in inverter respectively. For example, the switching status [100], means in leg (a) one of the upper switches (S1) is conduct, and in legs (b & c) there are two of the lower switches (S6& S1) are conducted in the inverter respectively. There are two statuses, [111] and [000] gives zero in the output called zero conditions, and the others are active conditions [10]. SPACE VECTOR MODULATION The concept of space vector is being derived from the revolving magnetic field of induction machine. Three-phase quantities are transformed to two-phase quantity [11].  The active and zero switching conditions can be represented by active and zero space vectors, respectively. A typical schema of space vector for two-level VSI is shown in Figure 2. The six vectors V1 to V6 shapes a symmetric hexagon with similar sectors (1 to 6). Each sector is separated by 60 degrees to each other. From Figure 2, Vref is the reference voltage vector which used to control the magnitude and frequency of fundamental voltage.  TABLE1: SWITCHING CONDITIONS AND ON-STATUS SWITCHES Space Vector Switching conditions On-Status Switches Zero Vector    111          000          Active Vector    100             110             010             011             001             101             Figure 2: schema of space vector for two-level VSI SVPWM IMPLEMENTATION   When these 3-phase voltages in equations (1), (2) & (3) are applied to the AC machine, they produce a revolving magnetic flux in the air gap of the machine. This revolving flux component can be represented as a single revolving vector. The magnitude and angle of the revolving vector can be found by {α,β}or Clark’s Transformation [12]. The SVPWM is achieved by the next, following steps:   .1 Space vector Calculation Let three-phase sinusoidal voltage quantities be [13].                                                                                                                                                                                                    SUST Journal of Engineering and Computer Science (JECS), Vol. 19, No. 2, 2018   12  This step determined  ⃗     &    through {   } transformation:  ⃗               (                  )                                 | ⃗    |  √                                                              (    )                                                        Real and imaginary parts:      (                    )                       (                 )                             From equation (7) and (8) we can get the transformation  [    ]     [           √   √  ]   [      ]                            .2 Switching Time Durations Switching time durations,   ,    and    are calculated for sector 1 by the Volt-Sec method as:                                                                       (    )                                                                                                        where    √                                                                                                Generally switching time durations for all sectors can be determined by the following equations:             *   (     )+                                                      (       )                                               .3  Switching Sequences After calculations of space vectors and the switching time durations, the next step is determining prospective switching sequences for a given,     . I.First Switching Sequence Different groups of switches will be turned on or off if      pass into sectors one by one, Figure 3 shows Space vector diagram for      passes through all sectors. This sequence begins and ends with Zero Vector [000] as indicate in Table 2.  Figure 3: Space vector diagram for First sequence  TABLE 2: SWITCHING SEGMENT FOR FIRST SEQUENCE  sec Switching segment 1    000    100    110    111    110    100    000 2    000    010    110    111    110    010    000 3    000    010    011    111    011    010    000 4    000    001    011    111    011    001    000 5    000    001    101    111    101    001    000 6    000    100    101    111    101    100    000  II.Second Switching Sequence The inverter output voltage will change everyone cycles over time when      revolves around every rotation in space, This switching sequence begins and ends with switching status [111] instead of [000] as shown in Figure 4.   III. Third Switching Sequence  The conduction of the lower switches in inverter legs will be longer than that of the upper switches if used the First sequence the same thing happens in the upper switches if used the second sequence. SUST Journal of Engineering and Computer Science (JECS), Vol. 19, No. 2, 2018   13  This will cause unbalanced in power and heating. The problem can be solved by used the two types of the switching sequences alternatively, as shown in Figure 5.   Figure 4: Space vector diagram for Second  Sequence   Figure 5:  Space vector diagram for Third sequence TABLE 3: SEVEN-SEGMENT FOR MODIFIED SWITCHING SEQUENCE sec Switching segment 1    100    110    111    100    111    110    100 2    110    010    000    110    000    010    110 3    010    011    111    010    111    011    010 4    011    001    000    011    000    001    011 5    001    101    111    001    111    101    001 6    101    100    000    101    000    100    101  IV Modified Switching Sequence  The output of the inverter is adjusted by modulate the magnitude & revolving speed of reference voltage. The design of switching sequence for a given reference voltage is not unparalleled. This proposed switching sequence is different from other sequences, for example, in a sector 1 starts and ends with vector   .and in a sector 2 starts and ends with vector    and so on in other sectors as shown in Table 3.  SIMULATION of SVPWM  Simulation used SVPWM technique based on space vector theory & using Power Simulation package PSIM environment to obtaining the results.    First block in the model as shown in Figure 6 calculates space vector by determines  ,    by convert three phase sinusoidal voltage into two- phase equivalent using Clark’s transformation through Equations (7), (8) & (9), and then determines     , and angle (   ) using Equations (5) & (6).  As shown in Figure 7, the second block is used to determine vector location which determines      position in various sectors.   Figure 6: Space Vector Calculation  Next step the model calculates switching time duration (  ,    and   ) using Volt-Sec method through Equations (11), (12) & (13).as shown in Figure 8. The last step the model used lookup tables(Q1-Q6) which derived from switching sequence tables to generate space vector pulses required to drive the VSI as shown in Figure 9.  RESULTS Simulation results have been taken for various switching sequences feeding a passive load for SUST Journal of Engineering and Computer Science (JECS), Vol. 19, No. 2, 2018   14  R=2Ω and L=   . Switching frequency of 5 kHz was used in the model. DC link voltage of the two-level inverter was taken as 220V. Figures 10 to 13 shows inverter output waveforms produced by SVM scheme. The first sequence in Figure 10 shows line-line and phase voltages output waveforms. It furthermore, shows sinusoidal output current waveform for the inverter with THD (13%) for fundamental frequency 60Hz. As can be seen the output voltage waveform has two levels. The second sequence output waveforms illustrated in Figure 11 as can be seen the output waveforms are plotted for voltages and also for current with THD (14%). Figure 12 illustrate the third sequence output waveforms.   Figure 7:  Vector location determination   Figure 8: switching time duration calculation  Figure 9: Switching sequences generation.      Figure 10: Inverter output waveform for First sequence     Figure 11: Inverter output waveform for Second sequence 0-5050100150200250Va0-100-200-300100200300Vab0 0.02 0.04 0.06 0.08 0.1 0.12Time (s)0-10-20-30102030I(RL1a)0-5050100150200250Va0-100-200-300100200300Vab0 0.02 0.04 0.06 0.08 0.1 0.12Time (s)0-10-20-30102030I(RL1a)SUST Journal of Engineering and Computer Science (JECS), Vol. 19, No. 2, 2018   15   Comparing with previous sequences (First and Second) it can be seen the THD is decreased to (10%). Figure 13shows proposed switching sequence output waveforms.as we can see the results shows less harmonics distortion in the output waveform. Also it can be observed that the THD is decreased to (4%) comparing with the other switching sequences. Table 4 shows comparative results statement of all four switching sequences.   Figure 12: Inverter output for Third sequence   Figure 13: Inverter output for modified sequence  EXPERIMENTAL SETUP The model of SVPWM for two levels VSI in (section 5) is implemented on Arduino Mega board Atmega2560 microcontroller and the experimental results are presented for two-level inverter before and after LC filter. Figure 14 shows the experimental circuit design for two level (VSI). The circuit is consisted of Arduino Mega board with ATmega2560 microcontroller. This microcontroller generates space vector pulses from code written by (IDE) software. Furthermore, circuit contains 6 switches type N-channel MOSFET(IRF450) and high & low side transistor drivers’ type (IR2112). Figures 15 & 16 illustrate real phase voltage wave forms measured by oscilloscope, generated by space vector modulation for two level VSI before and after LC filter .and its same as waveforms that we get from previous simulation model.  Figure 17 shows the Real image for experimental circuit setup.  TABLE 4 . COMPARATIVE RESULTS BETWEEN FOUR SEQUENCES No Performance Parameters First Second Third Modified Sequence 1 Phase voltage THD 288% 264% 286% 280% 2 Line voltage THD 117% 117% 123% 113% 3 Line current THD 13% 14% 10% 4%    Figure 14: Experimental circuit design for two- level VSI .  0-5050100150200250Va0-100-200-300100200300Vab0 0.02 0.04 0.06 0.08 0.1 0.12Time (s)0-10-20-30102030I(RL1a)0-5050100150200250Va0-100-200-300100200300Vab0 0.02 0.04 0.06 0.08 0.1 0.12Time (s)0-10-20-30102030I(RL1a)SUST Journal of Engineering and Computer Science (JECS), Vol. 19, No. 2, 2018   16   Figure 15: Measured voltage waveforms for two level VSI before filter   Figure 16:  Measured voltage waveforms for two level VSI after filter   Figure 17: Real image for experimental circuit setup  CONCLUSION  The simulation study of a two-level inverter is implemented using SVPWM because it's more efficiently, generates less harmonic distortion and simple digital realization. In this paper, a two-level inverter has been modeled and simulated using the PSIM package program. Simulation results have been given for various switching sequences using 5kHz switching frequency and a passive load. 220v is used for DC voltage supply of a two-level inverter. Comparative is made between four switching sequences and the proposed one is the best choice to drive the inverter because it has less THD comparison with other switching sequences. Implementation is confirmed by generating SVPWM waveforms from code written in cheap microcontroller and results are matching with the simulation very well.    Further studies should be done for more than two-level SVPWM to get higher level for voltages. In the future, studies may be available for implementing the same switching sequences that we realize but in the three level or four level. Definitely, the performance will be different comparing with switching sequences in two- level inverter.  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Space Vector Pulse Width Modulation Technique Applied to Two Level Voltage Source Inverter

http://journal.sustech.edu/index.php/JECS/article/view/332/109

Space Vector Pulse Width Modulation Technique Applied to Two Level Voltage Source Inverter

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