Ain Shams Engineering Journal (Jul 2023)
Power quality improvement of a distribution system integrating a large scale solar farm using hybrid modular multilevel converter with ZSV control
Abstract
Photovoltaic system is a major source of power generation. Its production is affected by the varying shading conditions that occur due to changing weather and other environmental factors. The modular multilevel converter (MMLC) is a promising selection to achieve high power. However, to achieve more levels of voltages the conventional MMLC requires more cells which eventually increases the complexity and losses. In this paper, the hybrid MMLC is proposed which have fewer IGBT switches for the same number of output level which eventually decreases the losses and improves the voltage output. The production of power is enhanced due to the series and parallel connection of half and full bridge cells in the converter configuration. The power quality issues such as voltage, current, and power are also satisfactorily handled by the converter without using any active or passive filters. However, due to the variation of input irradiation and temperature the output parameters such as Voltage, current and power show disturbance. Mitigation of these unbalances for a grid connected converter is important to stabilize the control and the quality of power injected into the grid. Therefore, zero sequence control (ZSC) is proposed for producing the balanced power during unstable input parameters. For ensuring the balanced power among the phases of the Converter to be fed to the grid zero sequence voltage (ZSV) is injected in each phase of the converter output validating the power balancing among the phases fed to the low voltage grid. Simulation results are presented to assess the output parameters before and after the injection of ZSV in the low voltage (LV) grid connected Hybrid MMLC of a large scale PV system and demonstrate the improved performance. This investigation is verified by simulation results with PSCAD software.
