A Modified Cascaded H-Bridge Multilevel Inverter for solar applications

ABSTRACT:

In this paper, a modified cascaded H-bridge multilevel inverter (MLI) is proposed and designed for solar applications. Generally, as the level of conventional multilevel inverter increases, the required number of switches and size increases. The proposed topology is cascade of unit stages which involves 5 switches and two voltage source; moreover a unit stage is capable of generating 5 levels. Also, the detailed analysis of cascaded multilevel inverter is discussed which incorporates three different methodologies involving less number of power devices in order to generate maximum number of levels. This results into reduction in gate drive circuitry and less switching losses. The proposed MLI is designed for power 1.5kW and In phase level shifting SPWM technique has been incorporated in which 5kHz carrier wave is compared with 50Hz of sinusoidal wave with a modulation index of 0.8. As a result, total harmonic distortion (THD) is achieved as 4.71% with LC-filter for above mentioned multilevel inverter. The circuits are modeled and simulated with the help of MATLAB/SIMULINK.

KEYWORDS:

  1. Modified cascaded H-bridge MLI
  2. Solar
  3. SPWM techniques
  4. Total Harmonic Distortions

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig1. Proposed N-level modified cascaded MLI

EXPECTED SIMULATION RESULTS:

Fig.2 Output voltage and current waveforms (9-level) without filter

Fig.3 Output voltage and current waveform (9-level) with LC- filter

Fig.4 (a)-(c) Gate Pulse for 10 switches

Fig.5 Output voltage and current waveforms (13-level) without filter

Fig.6 Output voltage and current waveform (13-level) with LC- filter

Fig.7 Output voltage and current waveforms (17-level) without filter

Fig.8 Output voltage and current waveform (17-level) with LC- filter

Fig.9 THD of 9-level (first methodology) without filter

Fig.10 THD of 9-level (first methodology) with filter

Fig.11 THD of 13-level (Second methodology) without filter

Fig.12 THD of 13-level (second methodology) with filter

Fig.13 THD of 17-level (Third methodology) without filter

Fig.14 THD of 17-level (Third methodology) with filter

CONCLUSION:

In this paper, a new topology of modified cascaded H bridge MLI is designed for solar high power application. The three different methodologies have been analyzed and 9-level, 13-level and 17-level output is observed in the respective methodology. The number of switches used in the topology is less which in turn reduced the corresponding gate driving circuitry and made the circuit compact in size. The circuits of proposed MLI are simulated in MATLAB/SIMULINK and total harmonic distortions for the three methodologies are obtained by using FFT analysis window. The lowest THD observed with LC-filter is 4.71%. The proposed MLI is designed for power 1.5kW and In-Phase level shifting method is followed for the pulse generation for all three methodologies.

REFERENCES:

[1] Wei Zhao; Hyuntae Choi; G. Konstantinou; M. Ciobotaru; and V. G. Agelidis “Cascaded H-bridge Multilevel Converter for Large-scale PV Grid-Integration with Isolated DC-DC stage” PEDG, IEEE 2012.

[2] S. Rivera; S. Kouro; B. Wu; J. I. Leon; J. Rodriguez; and L. G. Franquelo “Cascaded H-bridge multilevel converter multistring topology for large scale photovoltaic systems,” IEEE ISIE 2011, pp.1837-1844.

[3] N.A. Rahim; K. Chaniago; and J. Selvaraj “Single-Phase Seven-Level Grid Connected Inverter for Photovoltaic System”, IEEE Transactions on Industrial Electronics, Vol. 58, No. 6, June 2011, pp. 2435-2443

[4] B. Singh; N. Mittal; and K. S. Verma “Multi-Level Inverter: A Literature Survey On Topologies And Control Strategies”, International Journal of Reviews in Computing, Vol. 10, July 2012, pp. 1-16

[5] Zhiguo pan; F .Z Peng; Victor Stefanoic; and Mickey Leuthen “A Diode-Clamped Multilevel Converter with Reduced Number of Clamping Diodes.”2004 IEEE.

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