This study presents a new circuit topology of the Modular Multilevel Converter (MMC) which is deployed for photovoltaic grid applications. In the conventional MMC, two arm inductors are placed in each phase to limit the circulating current. In the proposed topology, the inductors are replaced by a transformer. The proposed circuit gives a 50% reduction of the voltage rating of the power devices and the capacitors in comparison with the conventional MMC. The required dc-link voltage which is fed directly by PV panels is also reduced by half. The paper presents a PWM method to control the solar inverter output voltage. The proposed concept is confirmed through simulation and experimental results.

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A New Circuit of Modular Multilevel Inverter for
Grid-Connected Photovoltaic Conversion Plants
ABSTRACT:
This study presents a new circuit topology of the Modular Multilevel Converter (MMC) which is
deployed for photovoltaic grid applications. In the conventional MMC, two arm inductors are
placed in each phase to limit the circulating current. In the proposed topology, the inductors are
replaced by a transformer. The proposed circuit gives a 50% reduction of the voltage rating of
the power devices and the capacitors in comparison with the conventional MMC. The required
dc-link voltage which is fed directly by PV panels is also reduced by half. The paper presents a
PWM method to control the solar inverter output voltage. The proposed concept is confirmed
through simulation and experimental results.
KEYWORDS:
1. Photovoltaic (PV) conversion
2. Modular multilevel converter
3. Pulse width modulation
4. Parameter
SOFTWARE: MATLAB/SIMULINK
CONCLUSION:
In this paper, the feasibility of a new circuit topology for the MMC has been outlined, where it is
deployed as an interface between the grid and PV modules. With this arrangement, the voltage
rating of capacitors and the power semiconductor devices are effectively reduced by half. The dc
bus magnitude which is formed by the dc output from PV array is also reduced by half. A
method to suppress the 2nd harmonic current in the inverter has been discussed. The concept of
level-shifted PWM, where the modulating waveform is shifted and scaled to bring inside one

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carrier, has been used to reduce the switching frequency. With this, there is no need to calculate
the duty cycle of individual cells. The proposed idea has been verified by simulation and
experimental results under disturbance in the system caused by solar irradiance changes.
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No. 1, pp. 416-421, Jan. 2013.
[3] International Energy Agency. (2010, May). Technology Roadmap, Solar Photovoltaic Energy
[Online].
[4] E. Romero-Cadaval, G. Spagnuolo, L. G. Franquelo, et al., “Grid-Connected Photovoltaic
Generation Plants,” IEEE Ind. Electron. Mag., Vol. 7, No. 3, pp. 6-20, Sept. 2013.
[5] M. G. Villalva, J. R. Gazoli and E. R. Filho, “Comprehensive Approach to Modeling and
Simulation of Photovoltaic Arrays,” IEEE Trans. Power Electron, Vol. 24, No. 5, pp. 1198-
1208, May 2009.