A Multilevel Inverter Structure based on Combination of Switched-Capacitors and DC Sources

ABSTRACT:  

This paper presents a switched-capacitor multilevel inverter (SCMLI) combined with multiple asymmetric DC sources. The main advantage of proposed inverter with similar cascaded MLIs is reducing the number of isolated DC sources and replacing them with capacitors. A self-balanced asymmetrical charging pattern is introduced in order to boost the voltage and create more voltage levels. Number of circuit components such as active switches, diodes, capacitors, drivers and DC sources reduces in proposed structure.

This multi-stage hybrid MLI increases the total voltage of used DC sources by multiple charging of the capacitors stage by stage. A bipolar output voltage can be inherently achieved in this structure without using single phase H-bridge inverter which was used in traditional SCMLIs to generate negative voltage levels. This eliminates requirements of high voltage rating elements to achieve negative voltage levels. A 55-level step-up output voltage (27 positive levels, a zero level and 27 negative levels) are achieved by a 3-stage system which uses only 3 asymmetrical DC sources (with amplitude of 1Vin, 2Vin and 3Vin) and 7 capacitors (self-balanced as multiples of 1Vin). MATLAB/SIMULINK simulation results and experimental tests are given to validate the performance of proposed circuit.

KEYWORDS:
  1. Multi-level inverter
  2. Switched-capacitor
  3. Bipolar converter
  4. Asymmetrical
  5. Self-balancing

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig (1) Three stage structure of the proposed inverter

 EXPECTED SIMULATION RESULTS:

 

 Fig (2) Waveform of the output voltage in (a) 50Hz and pure resistive load (b)

the inset graphs of voltage and current

 Fig (3) waveform of the output voltage in 50Hz with resistive-inductive load

 Fig (4) Capacitor’s voltage in 50Hz (a) middle stage (b) last stage

CONCLUSION:

 In this paper, a multilevel inverter based on combination of multiple DC sources and switched-capacitors is presented. Unlike traditional converters which used H-bridge cell to produce negative voltage that the switches should withstand maximum output AC voltage, the suggested structure has the ability of generating bipolar voltage (positive, zero and negative), inherently. Operating principle of the proposed SCMLI in charging and discharging is carried out.

Also, evaluation of reliability has been done and because of high number of redundancy, there has been many alternative switching states which help the proposed structure operate correctly even in fault conditions. For confirming the superiority than others, a comprehensive comparison in case of number of devices and efficiency is carried out and shows that the proposed topology has better performance than others. For validating the performance, simulation and experimental results are brought under introduced offline PWM control method.

REFERENCES:

[1] L. G. Franquelo, J. Rodriguez, J. I. Leon, S. Kouro, R. Portillo, and M. A. M. Prats, “The age of multilevel converters arrives,” IEEE Trans. Ind. Electron. Mag., vol. 2, no. 2, pp. 28–39, June, 2008.

[2] M. Saeedifard, P. M. Barbosa and P. K. Steimer,”Operation and Control of a Hybrid seven Level Converter,” IEEE Trans. Power Electron., vol. 27, no.2, pp. 652–660, February, 2012.

[3] A. Nami. “A New Multilevel Converter Configuration for High Power High Quality Application,” PhD Thesis, Queensland University of Technology, 2010.

[4] V. Dargahi, A. K. Sadigh, M. Abarzadeh, S. Eskandari and K. Corzine, “A new family of modular multilevel converter based on modified flying capacitor multicell converters IEEE Trans. Power Electron., vol. 30, no.

1, pp. 138-147, January, 2015.

[5] I. López, S. Ceballos, J. Pou, J. Zaragoza, J. Andreu, I. Kortabarria and V. G. Agelidis,” Modulation strategy for multiphase Neutral-Point Clamped converters,” IEEE Trans. Power Electron., vol. 31, no. 2, pp. 928–941, March, 2015.

Simulation of a Single-Phase Five-Level Cascaded H Bridge Inverter with Multicarrier SPWM B-Spline Based Modulation Techniques

ABSTRACT

 Multilevel Power Inverters are now often used to convert DC to AC voltage waveform. This kind of converter allows high power quality with low output harmonics and lower commutation losses with respect to the traditional ones in order to optimize this aspect. This paper presents a novel simulation analysis of the Multicarrier Sinusoidal Pulse Width Modulation (MC SPWM) techniques B-Spline functions based to control the switches of five-level single-phase cascaded H bridge inverter. In order to verify the performance of the converter, the harmonic content of the voltage due to modulation techniques has been taken into account. Results highlight the comparison between different B-Spline functions.

 KEYWORDS

  1. Multilevel power converter
  2. Multicarrier modulation techniques
  3. B-spline functions

 SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM

Fig. 1: CHBMI single-phase with 2n+ 1 level

 EXPECTED SIMULATION RESULTS

 

 Fig. 2: Comparison of TH D% versus reference voltage trend for Phase Disposition PD carriers: B 2(t), B  3(t) and B 4(t).

Fig. 3: Comparison TH D% versus reference voltage trend for

Phase Opposition Disposition POD carriers: B  2(t), B  3(t) and B 4(t).

Fig. 4: Comparison TH D% versus reference voltage trend for

Alternative Phase Opposition Disposition AP OD carriers: B 2(t),

B 3(t) and B 4(t).

Fig. 5: Comparison TH D% versus reference voltage trend for

Phase Shifted PS carriers: B  2(t), B 3(t) and B  4

Fig. 6: Comparison Fundamental Amplitude versus reference

voltage trend for Phase Disposition PD carriers: B2(t), B3(t) and

B4(t).

Fig. 7: Comparison Fundamental Amplitude versus reference

voltage trend for Phase Opposition Disposition POD carriers:

B 2(t), B  3(t) and B 4(t).

Fig. 8: Comparison Fundamental Amplitude versus reference

voltage trend for Alternative Phase Opposition Disposition AP OD

carriers: B 2(t), B 3(t) and B 4(t).

Fig. 9: Comparison Fundamental Amplitude versus reference

voltage trend for Phase Shifted PS carriers: B  2(t), B 3(t) and B 4(t).

 CONCLUSION

This paper presents a simulation analysis of the Multi carrier Sinusoidal Pulse Width Modulation techniques B-Spline functions based for five-level single-phase cascaded H-bridge invert er. The multi carrier modulation techniques taken into account are PD, POD, AP OD and PS using PB 2(t), PB 3(t) and PB  4(t) as carrier signals. In order to verify the performance of converter and harmonic content of the voltage, the used tool for comparison of different modulation techniques is TH D%. The computed TH  D% values versus reference voltage (peak value) for the phase voltage have been presented and the related results have been compared among different carrier signals used. The minimum value of the TH D% has  been obtained by using the PS modulation techniques with PB 4(t) as carrier signal.

REFERENCES

 [1] A. Ta k a  ha  s hi I. Nab e and H. Aka  g i, A new neutral-point clamped PW M invert er, IEEE Trans. Ind. A  p pl., 17, 518″ 1981.

[2] .T. Rodriguez, .T.-S. La i, and F. Z. Pen g, Multilevel invert  er s: a survey of top  o l o  g i e s, controls, and applications, Industrial Electronics, IEEE Transactions on, vol. 49, no. 4, pp. 724- 738, Aug. 2002.

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