International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) ...
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) ...
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) ...
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) ...
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) ...
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) ...
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) ...
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) ...
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) ...
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Analysis and simulation of multilevel inverter using multi carrier based pwm

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Analysis and simulation of multilevel inverter using multi carrier based pwm

  1. 1. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME 200 ANALYSIS AND SIMULATION OF MULTILEVEL INVERTER USING MULTI CARRIER BASED PWM CONTROL TECHNIQUE Dr. Hina Chandwani1 , Himanshu N Chaudhari2 and Dhaval Patel3 1 (1Associate Professor, Dept. of Electrical Engineering, The M.S.University of Baroda, Vadodara, India) 2 (2 Assistant professor, Dept. of Electrical Engineering, SNPIT&RC, Umrakh, Bardoli, Gujarat, India) 3 (3Student, Dept. of Electrical Engineering, The M.S.University of Baroda, Vadodara, India) ABSTRACT Multilevel voltage source inverter (VSI) has been recognized to be very attractive in high voltage dc to ac conversion.. It is based on the cascade connection of the several H- bridge inverter cells. This Paper proposes a multi carrier based control techniques for multilevel topology. Under multicarrier based PWM, different level shifted techniques has been used for obtain desire output and comparatively analysis has been done for required minimum harmonic distortion. Several tests to quantify the performance of the inverter under the proposed modulation scheme are carried out using Matlab Simulink models. Keywords: Matlab Simulink, Symmetrical type Cascaded Multilevel Inverter (SCMLI),Total harmonic distortion(THD). INTRODUCTION The importance of multilevel inverters[MLI] has been increased since last few decades. These new types of inverters are suitable for high voltage and high power application due to their ability to synthesize waveforms with better harmonic spectrum and with less THD. Numerous topologies have been introduced and widely studied for utility of non-conventional sources and also for various drive applications. Amongst these topologies, the multilevel cascaded inverter was introduced in Static VAR compensation and in drive systems. INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING & TECHNOLOGY (IJEET) ISSN 0976 – 6545(Print) ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), pp. 200-208 © IAEME: www.iaeme.com/ijeet.asp Journal Impact Factor (2013): 5.5028 (Calculated by GISI) www.jifactor.com IJEET © I A E M E
  2. 2. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME 201 It has the advantages like high power quality waveforms, lower voltage ratings of devices, lower harmonic distortion, lower switching frequency and switching losses, higher efficiency, reduction of dv/dt stresses etc. It gives the possibility of working with low speed semiconductors in comparison with the two-levels inverters. Numerous of MLI topologies and modulation techniques have been introduced. But most popular MLI topology is Diode Clamp, Flying Capacitor and Cascaded Multilevel Inverter (CMLI). In this paper we are using a CMLI that consist of several H-Bridge inverters and with equal voltage DC sources named as Symmetrical type Cascaded Multilevel Inverter (SCMLI). The total output voltage is the sum of the outputs of all the full-bridge modules in the CMLI inverter and every full bridge can create the three voltages +V, 0 and -V. The sources in each full-bridge need to be isolated if the inverter is going to be implemented in active power transfer application, for voltage balance reasons since there isno common DC-bus torecharge the sources energy content. However, since the CMLI uses separate energy sources it is well suitable for renewable energy or energy/fuel cell applications there every separate voltage source could be isolated. A drawback for the energy/fuel cell applications is however that the sources must be charged individually or through the inverter. Multilevel PWM methods uses high switching frequency carrier waves in comparison tothe reference waves to generate a sinusoidal output wave, much like in the two-level PWMcase. To reduce harmonic distortions in the output signal shiftingtriangular carrier waves areused. There are several methods that change disposition of or shiftmultiple triangularcarrier waves. The number of carrier waves used is dependent to the number of switches tobe controlled in the inverter. In addition to the sinusoidalcarrier wave modulation methods presented furtherdown there are also two more well-known alternative methods that will not be discussed inthis paper: Alternative Position Opposition Disposition (APOD) and Phase OppositionDisposition (POD). I. CASCADED MULTI LEVEL INVERTER(CMLI) This method eliminates the excessively large number of bulky transformers required by conventional multi-level inverters, the clamping diodes required by diode clamped multilevel inverters and the bulky capacitors required by flying capacitor multilevel inverters. This method consists a series connection of multiple H bridge inverters. Each H-bridge inverter has the same configuration as a typical single-phase full-bridge inverter. This method introduces the idea of using separate DC sources to produce an AC voltage waveform which is nearly sinusoidal. Each H bridge inverter is connected to its own DC source. By cascading the output voltage of each H-bridge inverter, a stepped voltage waveform is produced. If the number of H-bridges is N, the voltage output is obtained by summing the output voltage of bridges as shown in equation. Fig.1shows configuration of ACMLI of single-phase.
  3. 3. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME 202 Fig.1. Single-phase cascaded multilevel inverter If ACMLI has N no. of H-Bridges, The output voltage could be expressed as; Vo (t) = Vo1 (t) + Vo2 (t) + ..... + Vo N (t) …………(1) Where, Vo1 (t) ,Vo2 (t) , ..... Vo N (t) is the output of individual H-bridge. II. CARRIER BASED PWM TECHNIQUES The carrier-based modulation schemes for multilevel inverters can be generally classified into two categories: phase-shifted and level-shifted modulations. Both modulation schemes can be applied to the cascaded H-bridge(CHB) inverters. An m-level MLI using multicarrier modulation scheme requires (m-1) triangular carriers, all having the same frequency and amplitude. The (m-1) triangular carriers are horizontally disposed for phase shifted modulation and vertically disposed vertically disposed for level shifted modulation such that the bands they occupy are contiguous. Phase shift PWM [2pp, 3pp, 4pp] involves the same principle of standard 2-level PWM to gate the switches using the comparison between two signals, reference and carrier, but exploit more than one carrier to generate the driving signals. Allcarriersare having same amplitude and frequency but asthe name suggests, the carriers have to be displaced by shifting their phases. The phase shift can be done choosing any delay but the minimum harmonic distortion of the output is achieved using the delay ∆ given by equation (1), where Ts is the switching period. ∆=Ts/((n-1)) -------(1)
  4. 4. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME 203 Fig.2 The output switching frequencies results will be higher than carrier one and (2) shows the relationship between output and carrier switching frequencies, fout and fcar respectively for m-level converter. fout= (m −1) x fcar. -----(2) Most of the level shifted carrier based PWM techniques have been derived three carrier dispositionstrategies. The phases of carrier signals are rearranged to produce three main disposition techniques known as IPD, POD and APOD. The reference or modulating wave is positioned at the Centre of the carrier set and continuously compared with the carriers.Whenever the magnitude of reference wave is greater than a carrier wave positive going switching pulse is obtained. When the reference goes above all the carriers maximum output is obtained. As the reference falls below each carrier the corresponding levels in the inverter output gets reduced. Carrier arrangements and corresponding switching patterns generated by seven-level Disposition PWM are illustrated in Figs. 3–5. (i) In-phase disposition (IPD), where all carrier waveforms are in phase (ii) Phase opposition disposition (POD), where all carrier waveforms above zero reference are in phase and are 1800 out of phase with those below zero
  5. 5. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME 204 (iii) Alternate phase disposition (APOD), where every carrier waveform is in out of phase with its neighbor carrier by 1800 III. SIMULATION, RESULT AND DISCUSSION The computer software package Matlab Simulink was used to implement all of the Modulation Techniques. 5-Level PSPWM Fig 6: Simulink model using two bridges. The Matlab Simulink Model for single phase 5-level MLI using Phase Shifted PWM Technique(Common in all modulation techniques for CMLI using two H-bridges bridges) is shown in Fig.6. In five level High Frequency modulation only two bridges will require. The sub-circuit block for Modulation techniques holds the control circuit for phase shifted modulation technique.
  6. 6. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME 205 In PSPWM switching Frequency is four times higher than the carrier frequency accordingly five level output using PSPWM is shown in Fig.7. In seven level High Frequency modulation three bridges will require. The sub-circuit block for Modulation techniques holds the control circuit for phase shifted modulation Technique. Fig.8 7-level output with three bridges using PSPWM 5-Level LSPWM The Matlab Simulink Model for single phase 5-level MLI using Level Shifted PWM Technique is shown in Fig.9. In five level High Frequency modulation only two bridges will require. The sub-circuit block for Modulation techniques holds the control circuit for Level Shifted (POD) modulation Technique and is shown in Fig.10.
  7. 7. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME 206 Fig.9 5-level using LSPWM Control Pulse Generation Fig.10 5-level output using LSPWM 7-Level Level Shifted PWM (IPD, POD, APOD) The Matlab Simulink Model for single phase7-level MLI using Level Shifted PWM Technique is shown in Fig.11. It can be easily implemented as shown in Fig.12, however few changes of no. of carriers and phase change of triangular carrier waves are required according to modulation techniques. Output and FFT of 7-level using IPD, POD and APOD modulation techniques is shown in fig.13, 14 and 15 respectively.
  8. 8. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME 207 Fig.13 7-Level using IPD LSPWM [FFT] Fig.14 7-Level using POD LSPWM [FFT] Fig.15 7-Level using APOD LSPWM [FFT] 0 0.1 0.2 0.3 0.4 0.5 0.6 -50 0 50 Selected signal: 30 cycles. FFT window (in red): 23 cycles Time (s) 0 2 4 6 8 10 12 14 16 18 20 0 0.02 0.04 0.06 0.08 0.1 Harmonic order Fundamental (50Hz) = 60.07 , THD= 0.67% Mag(%ofFundamental)
  9. 9. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME 208 THD RESULTS The Matlab Simulink was used to implement all of the Modulation Techniques their output and FFT analysis. The THD Comparison of different techniques is show in Table.1 Table. 1 No. of output levels Control Technique No of Bridge Required THD 5 MCPWM(POD) 2 1.00 7 MCIPD 3 0.80 7 MCPOD 3 0.67 7 MCAPOD 3 0.73 IV. CONCLUSION Single phase cascaded type high frequency multi-level inverter employing different multi carrier single reference modulation schemes has been investigated and their FFT analysis has been performed. It is conclude from Table 1 that PODPWM technique provides output with relatively low harmonic distortion. Itis observed that LSPWM have higher output switching frequency than the carrier frequency and so useful for implementing with microcontroller based devices where maximum triangular carrier frequency with better sampling rate is limited due to limitation of operating frequency of devices. REFERENCES Journal Papers [1] 2pp. B. P. McGrath, D. G. Holmes, “Multicarrier PWM Strategies for Multilevel Inverters”,IEEE Trans. on Ind. Elect., Aug. 2002, Vol. 49, Num. 4, pp.858-867. [2] 2pp. M. Calais, L. J. Borle, V. G. Agelidis, “Analysis of Multicarrier PWM Methods for Single-Phase Five Level Inverter”, Power Electronics Specialists Conference PESC 2001, 17-21June 2001, Vol. 3, pp. 1351-1356. [3] 3pp. B. Mwinyiwiwa, Z. Wolanski, B. T. Ooi, “Microprocessor-Implemented SPWM for Multiconverters with Phase-Shifted Triangle Carriers”, IEEE Trans. on Ind. Appl., May/Jun.1998, Vol. 34, Num. 3, pp 487-494. [4] Pradeep B Jyoti, J.Amarnath and D.Subbarayudu, “The Scheme of Three-Level Inverters Based on SVPWM Overmodulation Technique for Vector Controlled Induction Motor Drives”, International Journal of Electrical Engineering & Technology (IJEET), Volume 4, Issue 2, 2013, pp. 245 - 260, ISSN Print : 0976-6545, ISSN Online: 0976-6553. [5] B.Kiran Kumar, Y.V.Sivareddy and M.Vijayakumar, “Comparative Analysis of Sine Triangle and Space Vector PWM for Cascaded Multilevel Inverters”, International Journal of Electrical Engineering & Technology (IJEET), Volume 4, Issue 2, 2013, pp. 155 - 164, ISSN Print : 0976-6545, ISSN Online: 0976-6553. Book [6] Bin Wu.”High-Power ConvertersAnd Ac Drives”.

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