comparative study and analysis of different levels of

International Journal of Application or Innovation in Engineering & Management (IJAIEM) Web Site: www.ijaiem.org Email: [email protected]

Volume 10, Issue 9, September 2021 ISSN 2319 - 4847

Volume 10, Issue 9, September 2021 84

ABSTRACT Conventional Inverters have the drawbacks of producing high voltage stress, low-efficiency, and high temperature and are limited to small scale industrial applications. Hence for large scale industries, high-power applications and grid-connected renewable energy systems, the concept of Multi-level Inverters is the best choice. Multi-level Inverter promises a lot of advantages such as improved sinusoidal output voltage waveforms with reduced Total Harmonic Distortion [THD] over a conventional Inverter. This paper presents the design of different levels of Cascaded H-Bridge Multi-level Inverter for grid connected Photovoltaic system with reduced Total Harmonic Distortion [THD] using MATLAB/Simulink. A real time 66/11kV Santhe bachalli Sub- Station of KPTCL, Mysuru which is having 2 MW Solar Power Generation integrated to the Sub-Station at 11kV reference is considered for performance evaluation of proposed Multi-level Inverter. Keywords: Total Harmonic Distortion, Cascaded H-Bridge Multi-level Inverter, Photovoltaic System, Grid Connected

1. INTRODUCTION The electricity consumption is increasing gradually due to the increase of number of users and high power

applications. Increasing energy demand leads to lack of fossil fuels and conventional energy generation due to significant global emission. In this regard, renewable energy has become very popular and demanding as a solution to the increase in energy demand. By usage of renewable energy resource provides the pollution free environment. Photovoltaic system is one of the energy resources rapidly growing all over the world, especially in grid-connected applications. Utilities are adopting solar as their fastest growing power source. Solar based technologies uses the PV cells for the conversion of the solar energy into electrical energy. The solar PV system consists of PV cells, converters, and the control unit for the regulation of Converter. [1]. In the grid connection PV system photo voltaic Inverter is the one of the most essential part, which is used to convert DC power into AC power which is to be fed into the grid. Conventional [two-level] Inverter has some limitations with respect to the harmonic distortion and output voltage level. To solve this problem the concept of Multi-level Inverter is introduced for PV applications. Multi-level Inverter promises a lot of advantages such as reduced harmonics , low dv/dt stress, low Electro-Magnetic Interference [EMI], high efficiency, high voltage ability and good quality of power due to multiple levels(stepped) output waveform. Depending on the quality of output voltage and the synthesized number of output voltage levels, they have the capacity to avoid the use of filters [2].

Various topologies of Multi-level Inverters are available viz Diode-Clamped Inverter, Flying Capacitor / Capacitor Clamped Inverter and Cascaded H-bridge MLI. The variance is in the working of switches and the source input voltage to the Multi-level Inverters.[4] The Total Harmonic Distortion and cost of implementation of Cascaded H-bridge Multi-level Inverter is lesser compared to that of Diode-Clamped and Flying Capacitor Inverter[5]. In this paper, the design and implementation of different levels (5,7 and 9) of Cascaded H-bridge Multi-level Inverter for

Comparative Study and Analysis of Different levels of Cascaded H-Bridge Multi-Level

Inverter (CHB-MLI) for Grid-Connected PV system using PWM Technique

Anita Patgar, Sowmyashree N, Dr. M S Shashikala, Dr. Divakar H R

1Department of Electrical and Electronics Engineering, SJCE,JSS S&T University, Mysore, India Email: [email protected]

2Department of Electrical and Electronics Engineering, SJCE,JSS S&T University, Mysore, India Email: [email protected] 3Department of Electrical and Electronics Engineering, SJCE,JSS S&T University, Mysore, India Email: [email protected]

4Department of Master of Computer Applications, PES College of Engineering, Mandya, India Email: [email protected]



Volume 10, Issue 9, September 2021 Page 185

grid connected Solar PV system to enhance the quality of power supply and efficiency with reduction in Total Harmonic Distortion is propounded.

2. CASCADED H-BRIDGE MULTI-LEVEL INVERTER The cascade H-bridge Multi-level Inverter consists number of single full bridge Inverter units. Each bridge is fed by separate dc source namely battery, PV cell or any kind of dc supply. The output of each bridge is summed up to generate almost sinusoidal output voltage waveform for nth level of CHB-MLI. Each full bridge Inverter unit of the CHB-MLI requires a separate dc source and four semi-conductor switches. Four semiconductor switches are able to produce three different voltage levels namely +vdc, 0 and –vdc depending on the switching state.[6]. The block diagram of the CHB-MLI is as shown in figure 1

Figure: 1 Block Diagram of CHB-MLI

3. MODELING OF CASCADED H-BRIDGE MULTI-LEVEL INVERTER [CHB-MLI] In this paper, four different levels of three phase cascaded H-bridge Multi-level Inverters [5level, 7level, and 9 level] are modeled and integrated with solar PV system to analyze the performance of the grid connected photovoltaic system. The parameters required for the each phase leg of Cascaded H-Bridge Multi-level Inverters are as shown in the table 1

Table: 1 Parameters of Cascaded H-Bridge Multi-level Inverters

Para

met

er

per

phas

e

Equ

atio

n

3 le

vel

5 le

vel

7 le

vel

9 le

vel

No of DC source m=2*n+1 1 2 3 4

Switch 2(m-1) 2(3-1)=4 2(5-1)=8 2(7-1) = 12 2(9-1)=16

Maximum O/P voltage

=Vdc =2Vdc =3Vdc =4Vdc

Minimum O/P voltage

=-Vdc =-2Vdc

=-3Vdc

=-4Vdc

Where n represents DC source, m represents voltage level




3.1 THREE PHASE FIVE LEVEL CASCADED H-BRIDGE MULTI-LEVEL INVERTER [CHB-MLI] Figure: 2 represents circuit diagram of three-phase five-level CHB-MLI. One H-bridge cell is a three-step single-phase CHB-MLI. Two bridge circuits generate five level voltage i.e. 2Vdc, Vdc, 0, −Vdc and −2Vdc. where Vdc is the source voltage [PV]. To design a three-phase 5-level CHB-MLI, 6 separate DC source, 6-capacitors at the DC side and 24 switches are needed. One pair of switches produces +ve result and another couple of switches provides –ve result.

Figure:2 Circuit Diagram of a Three-Phase Five Level CHB-MLI

Modulation Technique: The control of out voltage is essential in order to compensate the input voltage variation and for Inverter regulation. Hence in each module of phase leg Carrier-based level- shift sinusoidal-pulse-width-modulation technique is employed to generate the gate signals. For 5 level inverter (5-1=4) 4 no. of carrier waves are required to generate the output waveform. These four carrier waves are in phase with zero upper and lower references. Two carrier waves above the zero reference and two carrier waves below the zero reference as shown in Figure: 3

Figure:3 Carrier wave and Reference waves for a Five-Level CHB-MLI with PD-PWM

The 5 level CHB-MLI is operated in five modes of switching as shown in Table 2. Table 2 Switching States of Five Level CHB-MLI

Voltage A1 A2 A3 A4 A5 A6 A7 A8

2Vdc 1 0 0 1 1 0 0 1

Vdc 1 0 0 1 0 1 0 1

0 0 1 0 1 0 1 0 1

−Vdc 0 1 1 0 0 1 0 1

-2Vdc 0 1 1 0 0 1 1 0




If the reference wave is larger than the first +ve carrier wave of the Inverter , it is tuned to +Vdc. If the reference wave is larger than the second +ve carrier wave [upper most] of the Inverter, it is tuned to +2Vdc. If the reference waveform is smaller than all the +ve carrier wave as well as −ve carrier wave then it is switched to “0”. If the reference wave is less than the first −ve carrier wave of the Inverter, it is tuned to−1Vdc. If the reference wave is less than the second −ve carrier waveform [lower most] of the Inverter, is switched to−2Vdc.

3.2 THREE PHASE SEVEN LEVEL CASCADED H-BRIDGE MULTI-LEVEL INVERTER [CHB-MLI] Figure: 4 represents circuit diagram of three-phase 7-level CHB-MLI. One full-bridge circuit is a three-step CHB-MLI. Two bridge circuit generate five levels of voltage and three bridge circuit generate 7 voltage-levels i.e 3Vdc, 2Vdc, Vdc, 0, [−Vdc], [−2Vdc] and [-3Vdc] where Vdc is source voltage [PV]. To design Three-phase 7-level CHB-MLI, 9 different DC source, 9 capacitors at the DC side, 36 switches are needed.

Figure: 4 Circuit Diagram of A Three-Phase Seven level CHB-MLI For 7 level inverter (7-1=6) 6 no. of carrier waves are required to generate the output waveform. Three carrier waveforms above the zero-reference line and three carrier-waves below the zero-reference line and all carrier waves are in phase. The seven level CHB MLI is operated in seven modes of switching as shown in Table 3.

Table 3. Switching states of IGBT for 7 level CHB-MLI

Voltage S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12

3Vdc 1 0 0 1 1 0 0 1 1 0 0 1

2Vdc 1 0 0 1 1 0 0 1 0 0 1 1

Vdc 1 0 0 1 0 0 1 1 0 0 1 1

0 0 0 1 1 0 0 1 1 0 0 1 1

−Vdc 0 0 1 1 0 0 1 1 1 0 0 1

-2Vdc 0 0 1 1 0 1 1 0 0 1 1 0

-3Vdc 0 1 1 0 0 1 1 0 0 1 1 0




3.3 MODELING OF NINE LEVEL CASCADED H-BRIDGE MULTI-LEVEL INVERTER [CHB-MLI] Figure: 5 represent circuit diagram of three-phase 9-level CHB-MLI. Four bridge module generate 9 voltage levels i.e 4Vdc, 3Vdc, 2Vdc, Vdc, 0, −Vdc, −2Vdc, -3Vdc,-4Vdc where Vdc is source voltage. To design three-phase 9-level CHB-MLI, 12 different DC source, 12 capacitors at the DC side, 48 switches are needed.

Figure: 5 Circuit Diagram of a Three-Phase Nine level CHB-MLI

For 9 level inverter (9-1=8) 8 no. of carrier waves are required to generate the output waveform. Four carrier waves above the zero-reference line and four carrier-waves below the zero-reference line and all carrier waves are in phase. The Nine level CHB MLI is operated in nine modes of switching as shown in Table 4.

Table 4.Switching states of IGBT for 9 level CHB-MLI

Voltage G-

S1

G-

S2

G-

S3

G-

S4

G-

S5

G-

S6

G-

S7

G-

S8

G-

S9

G-

S10

G-

S11

G-

S12

G-

S13

G-

S14

G-

S15

G-

S16

4Vdc 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1

3Vdc 1 0 0 1 1 0 0 1 1 0 0 1 0 1 0 1

2Vdc 1 0 0 1 1 0 0 1 0 1 0 1 0 1 0 1

Vdc 1 0 0 1 0 1 0 1 0 1 0 1 0 1 0 1

0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

−Vdc 0 1 1 0 0 1 0 1 0 1 0 1 0 1 0 1

-2Vdc 0 1 1 0 0 1 1 0 0 1 0 1 0 1 0 1

-3Vdc 0 1 1 0 0 1 1 0 0 1 1 0 0 1 0 1




-4Vdc 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0

4. SIMULATION OF GRID CONNECTED PHOTO-VOLTAIC SYSTEM THROUGH 5,7 AND 9 LEVEL OF CASCADED-BRIDGE MULTI-LEVEL INVERTER

The live example of 66/11kV Santhebachalli Sub-Station of KPTCL, Mysuru is considered as a case study for this Project. A 2 MW Solar PV system integrated with 7 Bus-System through different level Cascaded H-Bridge Multi-level Inverter is considered for simulation to study the performance and efficiency of the system.

This model uses Simulink blocks such as, three-phase source, three-phase series RLC branch, three-phase transformer, PV array with Genetic algorithm based MPPT, grid block connected through 3 different levels(5,7 and 9) of cascaded H-Bridge Multi-level Inverter and three-phase load with voltage and current measurement system connected to measuring scope.

Simulink model consists of a three-phase voltage source having a phase-to-phase voltage [Vrms] of 66kV and a three-phase transformer of 12.5MVA connected in series with RL branch having a resistance of 2.9987 ohms and an inductance of 0.019H. 6 numbers of 11kV feeders viz Chottana Halli, GRS, Adihalli, C S Halli, S B Halli [Town], and Sarangi are considered to model the practical system. Measurement blocks were incorporated to measure voltage and current and to analyse performance of the model. Table 5 shows the load details of the 11kV feeders.

Table: 5 Load details of the 11kV feeders

Sl No Type Feeder Name Loa

d Reactive Power in

KVAR Active Power in

KW

1 NJY (Domestic) Chottana Halli 1 280 496

2 Rural (IP) GRS 2 430 663

3 Rural (IP) Adihalli 3 365 575

4 Rural (IP) C S Halli 4 284 417

5 NJY (Domestic)

S B Halli (Town) 5 169 245

6 NJY (Domestic) Sarangi 6 210 372

A 2 MW PV [83937.15*12*2] array is modeled in Simulink environment and the details of the PV array considered for the simulation is listed in Table 6. These PV array has been fed with irradiance of 1000 W/Sq.m and temperature of 250C. DC input is obtained from the PV array and is given to the Genetic Algorithm based MPPT controller to obtain the maximum power point. These were connected to the 3 different levels of CHB-MLI which converts the generated DC supply into AC supply with low harmonic distortion. Then these blocks were connected to 2MVA three phase transformer, which connects to a grid system as shown in figure:6

Table: 6 Specifications of 83.9 kW PV Array

Array Data

Parallel strings 55

Series-connected modules per string 5




Module Data

Module SunPower SPR-315E-WHT-D

Maximum Power (W) 305.226

Voltage at maximum power point Vmp

(V) 54.7

Open circuit voltage Voc (V) 64.2

Temperature coefficient of Voc (%/deg.C) -0.27269

Cells per module (Ncell) 96

Short-circuit current Isc (A) 5.96

Current at maximum power point Imp (A) 5.58

Temperature coefficient of Isc (%/deg.C) 0.061745

Figure: 6 Three-phase Five Level CHB-MLI Model Developed in MATLAB/SIMULINK

In this paper, three different levels of three-phase cascaded H-bridge Multi-level Inverters [5level, 7level, and 9 level] are modeled as per the design shown in figure 2, 4 and 5 respectively and integrated with solar PV system to analyze the performance of the grid integrated photovoltaic system.

5. RESULTS AND DISCUSSIONS

5.1 RESULTS OF SIMULINK MODEL OF FIVE LEVEL CASCADED H-BRIDGE MULTI-LEVEL INVERTER [CHB-MLI]

Simulink model of 66kV grid integrated system with PV array through 5 level cascaded H-bridge Multi-level Inverter is developed to show the performance of the system. The Figure: 7 shows the voltage profile of three-phase 5 level CHB-MLI without LC filter for a simulation duration of 0.2s.




Figure: 7 Voltage profile of the Five Level CHB-MLI without LC filter.

The five level voltage profile was found with maximum voltage 1355 Volts and Minimum Voltage [-] 1355 Volts.

The total harmonic distortion for the developed 5 level CHB-MLI inverter without filter is as shown in Figure: 8.

Figure: 8 THD Analysis of 5level CHB-MLI Without Filter

From the results, the total harmonic distortion of 27.33 % was observed. The harmonic analysis shows that 2nd ,3rd ,4th ,5th and 6th harmonics are predominant and all the other has very low impact.

Figure: 9 shows the voltage profile of three-phase 5 level CHB-MLI with LC filter, it was noted that voltage profile is less disturbed compared to the 3 level voltage wave form.




Figure: 9 Simulation Results of 5 Level CHB-MLI With Filter

The total harmonic distortion for the developed 5 level cascaded H-Bridge Multi-level Inverter with filter is as shown in Figure: 10

Figure: 10 THD Analysis of 5 Level CHB-MLI With Filter

From the results, the total harmonic distortion of 9.36 % was obtained for 5 level CHB-MLI with filter. From the analysis, it is noted that the total harmonic distortion was reduced to 9.36% from 27.33% by the implementation of LC filter.

Figure: 11 shows that the voltage and current profile of the Grid connected solar PV system through 5 Level CHB-MLI. Peak voltage:-8.542*10^3 Volts, Current: 139 Amps.




Figure: 11. Simulation Results Of Grid Connected Solar PV System Through 5 Level CHB-MLI

5.2 RESULTS OF SIMULINK MODEL OF SEVEN LEVEL CASCADED H-BRIDGE MULTI-LEVEL INVERTER [CHB-MLI]

The Figure: 12 shows the voltage profile of the three-phase seven Level CHB-MLI without LC filter for simulation duration of 0.2s.

Figure: 12 Simulation Results of 7 Level CHB-MLI

The Seven level voltage profile was found with maximum voltage 1974 Volts and Minimum Voltage -1985 Volts.

The total harmonic distortion for the developed 7 level CHB-MLI without filter is as shown in Figure: 13.




Figure: 13 THD Analysis of 7 Level CHB-MLI Without Filter

From the results, the total harmonic distortion of 22.62 % was observed. The harmonics analysis shows that 2nd harmonic is predominant and all the other has very low impact.

Figure: 14 shows the voltage profile of three-phase 7 level CHB-MLI with LC filter.

Figure: 14 Voltage Profile of Three-Phase Seven Level CHB-MLI With LC Filter.

The total harmonic distortion for the developed 7 level cascaded H-Bridge Multi-level Inverter with filter is as shown in Figure: 15.

Figure: 15 THD Analysis of 7 Level CHB-MLI with Filter





Figure: 16 shows that the voltage and current profile of the Grid connected solar PV system through Cascaded H-Bridge 7 Level Inverter

Figure: 16. Simulation Results of Grid Connected Solar PV System through CHB-MLI

5.3 RESULTS OF SIMULINK MODEL OF NINE LEVEL CASCADED H-BRIDGE MULTI-LEVEL INVERTER [CHB-MLI]

The Figure:17 shows the voltage profile of the Nine Level CHB-MLI for simulation duration of 0.2s.

Figure: 17 Simulation Results of 9-Level CHB-MLI Without Filter

The nine level voltage profile was found with maximum voltage 2483 Volts and Minimum Voltage - 2485 Volts

The total harmonic distortion for the developed 9 level CHB-MLI inverter without filter is as shown in Figure: 18. From the results, the total harmonic distortion of 12.85 % was observed.

Figure: 18 THD Analysis of 9 Level CHB-MLI Without Filter

.Figure:19 shows the voltage profile of three-phase 9 level CHB-MLI with LC filter.




Figure: 19 Voltage Profile of Nine Level CHB-MLI With LC Filter.

The total harmonic distortion for the developed 9 level cascaded H-Bridge Multi-level Inverter with filter is as shown in Figure: 20.

Figure: 20 THD Analysis of 9 Level CHB-MLI With Filter


Figure: 21 shows that the voltage and current profile of the Grid connected solar PV system through 9 Level CHB-MLI.




Figure: 22. Simulation Results of Grid Connected Solar PV System through 9 Level CHB-MLI

5.4 COMPARISON OF OUTPUT VOLTAGE OF DIFFERENT LEVELS OF CASCADED H-BRIDGE INVERTER

Four different levels [i.e. 3, 5, 7 and 9] of CHB-MLI are simulated and simulation results are compared with theoretical results [i.e Vdc, 2Vdc, 3Vdc, and 4Vdc respectively]. Comparisons of output voltage are given in table 7.

Table 7. Comparison of Output Voltage of Different Level of CHB-MLI

Sl No Different levels of CHB-MLI Theoretical result [Vmax] Simulation Result [Vmax]

1 5 1341.6 V 1355 V

2 7 2007.6 V 1974 V

3 9 2724.8 V 2483 V

It is observed that the simulation results are approximately equal to the theoretical values. And also from results it was observed that the output voltage of the Multi-level Inverter increases with increase in the level of the inverters.

5.5 THD ANALYSIS OF DIFFERENT LEVELS OF CASCADED H- BRIDGE MULTI-LEVEL INVERTER The total harmonic distortion obtained by the different levels of CHB-MLI with and without filter has been

compared in the table 7

Table 7 Comparison of Total Harmonic Distortion [THD] of CHB-MLI

Serial No. Inverter level THD Percentage [without filter] THD Percentage [with

filter] THD Decreasing?

1 5 27.33 9.36

2 7 22.62 10.52 Yes




3 9 12.85 0.23 Yes

6. CONCLUSION

Design and modeling of different levels of cascaded H-Bridge Multi-level Inverter [i.e 5-level, 7-level and 9 level] for the grid connected real time system is presented in this paper. Comparison of output voltages obtained by the different levels of CHB-MLI is carried out. It is observed that the output voltage of the CHB-MLI increases with the increase in number of Inverter level. Analysis of total harmonic distortion is also carried out. Analysis shows that as the Inverter levels increase, percentage of total harmonic distortion decreases and provides smoother sinusoidal waveform. From the performance evaluation, it was observed that 9 level CHB-MLI combined with Genetic Algorithm based MPPT Technique extracts Maximum power from Photovoltaic system and also enhances the efficiency of the grid connected PV system by improving the quality of power. This analysis can be helpful in implementing the CHB-MLI in various high and medium power applications including the renewable energy resources.

ACKNOWLEDGMENT I would like to express deepest thanks and gratitude to the Department of E&EE, JSS S&TU, Mysuru, and the invaluable assistance of all the Senior Engineers and technical staff of KPTCL, Mysuru/Mandya for their constant support. I wish to pay my special regards to my family & friends for their endless love, support and encouragement.

References [1] Ali Bughneda , Mohamed Salem et al. “Review of Multi-level Inverters for PV Energy System Applications”,

Energies-2021 [2] V. Fernão Piresa,b, A. Cordeiroc, et al.” Three-phase Multi-level Inverter for grid-connected distributed

photovoltaic systems based in three three-phase two-level inverters”, Solar Energy Volume 174, 1 November 2018 [3] Cavalcanti, Marcelo C.; Farias, Alexandre M.; Oliveira, Kleber C.; Neves, Francisco A. S.. “Eliminating Leakage

Currents in Neutral Point Clamped Inverters for Photovoltaic Systems.” IEEE Transactions on Industrial Electronics, Vol. 59, No. 1. January 2012

[4] Abdelaziz Fria, Rachid El Bachtiria, et al. “A comparative study of three topologies of three-phase (5L) inverter for a PV system”, Energy Procedia 42 ( 2013 ) 436 – 445, The Mediterranean Green Energy Forum 2013.

[5] Nursyafiqah Binti Zahari. “Cascaded H - Bridge Multi-Level Inverter” A thesis submitted in partial fulfillment of the requirement for degree of Bachelor in Electrical Engineering (Electrical) Faculty of Electrical Engineering Universiti Teknologi Malaysia .June 2013

[6] Lini T Koshy, Rini Jones S.B “A Model Based Maximum Power Point Tracking for PV Panels using Genetic Algorithm”, International Journal of Engineering and Advanced Technology (IJEAT) ISSN: 2249 – 8958, Volume-4 Issue-6, August 2015

[7] Adnan Hussein Ali.“ An adaptable different-levels cascaded h-bridge inverter analysis for PV grid-connected systems”, International Journal of Power Electronics and Drive System (IJPEDS), 2019

[8] V. Jammala, S. Yellasiri, and A. K. Panda, “Development of a new hybrid Multi-level Inverter using modified carrier SPWM switching strategy,” IEEE Trans. Power Electron., 2018

[9] Bidyut MAHATO, Saikat MAJUMDAR, et al. “Carrier-Based PWM Techniques for Multi-level Inverters: A Comprehensive Performance Study” Journal of Science Part A: Engineering and Innovation, GU J Sci, Part A, 5(3): 101-111-2018

[10] Rekha Agrawal, Shailendra Jain” Multi-level Inverter for interfacing renewable energy sources with low/medium- and highvoltage grids” IET Renew. Power Gener., Vol. 11 Iss. 14, pp. 1822-1831, 2017.

[11] Dmitry Baimel, Saad Tapuchi, et al.“A Review of Carrier Based PWM Techniques for Multi-level Inverters' Control”, Wseas Transactions on Power Systems, E-ISSN: 2224-350X, Volume 12, 2017

[12] Anjali Sudarsanan, Roopa R, et al. “Comparison of Conventional & New Multi-level Inverter Topology:, International Journal of Scientific & Engineering Research, Volume 6, Issue 2, February-2015




[13] Abdelaziz Fri, Rachid El Bachtiri, et al. “Comparative study of H-bridge Multi-level Inverterdedicated to PV, IEEE, 978-1-4673-6374-7/13/$31.00-2013

[14] Bailu Xiao, Ke Shen, et al.“Control of Cascaded H-Bridge Multi-level Inverter with Individual MPPT for Grid-Connected Photovoltaic Generators:, 978-1-4673-0803-8/12/$31.00 IEEE-2012

[15] Rodriguez et al. “Multi-level Inverters: A survey of topologies, control, and applications”. IEEE Transactions on Industrial Electronics 2002

[16] M.H. Rashid, Power Electronics Circuits, Devices, and Applications, 3rd edn. (Pearson Prentice Hall, 2004) [17] P. Palanivel, S.S. Dash, “Analysis of THD and output voltage performance for cascaded multilevel inverter using

carrier pulse width modulation techniques” IET Power Electron. 4(8), 951–958 (2011) [18] P. Satheesh Kumar et al. “Performance Evaluation of Nine Level Modified CHB Multilevel Inverter for Various

PWM Strategies” International Journal of Modern Engineering Research (IJMER), Vol. 3, Issue. 5, Sep - Oct. 2013

[19] Chapala Shravani “Implementation of 5-Level H-Bridge Inverter with Multicarrier based Modulation Techniques” International Journal of Recent Technology and Engineering (IJRTE) ISSN: 2277-3878, Volume-8 Issue-5, January 2020

[20] Ronak A. Rana, Sujal A. Patel “Review of Multilevel Voltage Source Inverter Topologies and Analysis of Harmonics Distortions in FC-MLI” Electronics 2019

comparative study and analysis of different levels of

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