Abstract
Due to global warming and shortage of fossil fuels, the grid-connected solar photovoltaic (PV) system has gained significant popularity all over the world. The modular multilevel cascaded (MMC) inverter is the natural choice for step-up transformer and line filter less direct medium voltage grid integration of solar PV systems. However, power quality and loss are the important issues while connecting the PV system to the medium voltage grid through MMC inverter. Modulation technique is the key to maintain output power quality, e.g., total harmonic distortion (THD) and to ensure low switching and conduction losses. In this paper, an advanced modulation technique named “triangle saturated common mode pulse width modulation (TSCMPWM)” control is proposed for a 3-phase 5-level MMC inverter-based grid-tied PV system. Compared to traditional modulation techniques, the proposed TSCMPWM control offers the lowest voltage THD as well as lower inverter power losses. Performance of the proposed modulation technique is evaluated in MATLAB/Simulink environment and tested with a reduced scale prototype test platform. Both simulation and experimental results show the effectiveness of the proposed modulation technique.
Highlights
To mitigate the increasing energy demand without affecting the environment, the renewable energy sources such as solar, oceanic wave, and wind are being considered as the alternative source of energy all over the world
In grid-connected solar PV plants, inverters play an important role in conversion of electrical energy from DC to AC before feeding the solar power to grid
A wide research has been done by the research community on different types of multilevel inverter topologies
Summary
To mitigate the increasing energy demand without affecting the environment, the renewable energy sources such as solar, oceanic wave, and wind are being considered as the alternative source of energy all over the world. The neutral point clamped (NPC), flying-capacitor (FC), cascaded H-bridge (CHB) and modular multilevel cascaded (MMC) are the basic multilevel inverter topologies used in different industrial applications [5] Among these basic topologies, MMC has drawn significant attention from the research community for its numerous advantages such as capability to control the internal power flow, ease of implementation, low harmonic distortion in the output voltage, and less maintenance cost [6,7,8,9,10,11]. The performance (voltage and current THDs and the power losses) of the proposed switching technique is compared with that of the existing modulation techniques such as SPWM, THPWM, CSVPWM, THSDPWM, TDBCPWM, and SDBCPWM.
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