《《Modular Multilevel Inverter with New Modulation》.pdf

IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 28, NO. 11, NOVEMBER 2013 5063 Modular Multilevel Inverter with New Modulation Method and Its Application to Photovoltaic Grid-Connected Generator Jun Mei, Member, IEEE, Bailu Xiao, Student Member, IEEE, Ke Shen, Student Member, IEEE, Leon M. Tolbert, Fellow, IEEE, and Jian Yong Zheng Abstract—This paper proposed an improved phase disposition needed during light load conditions; meanwhile, this part pulse width modulation (PDPWM) for a modular multilevel in- of electrical energy would be released again for the load verter which is used for Photovoltaic grid connection. This new when the load is at the peak. As a result, the peak power modulation method is based on selective virtual loop mapping, to achieve dynamic capacitor voltage balance without the help of of the grid and the reliability of power supply can be an extra compensation signal. The concept of virtual submodule improved. (VSM) is first established, and by changing the loop mapping rela- 2) Fault ride-through capacity: A large-scale PV system has tionships between the VSMs and the real submodules, the voltages been required to have the ability to withstand short periods of the upper/lower arm’s capacitors can be well balanced. This of voltage abnormality, such as the voltage short-term method does not requiring sorting voltages from highest to lowest, and just identifies the MIN and MAX capacitor voltage’s index drop caused by short-circuit fault. The PV system should which makes it suitable for a modular multilev