Tank Circuiting of 3-Pole PV Based DC Microgrid for Pole-to-Pole Voltage Balancing

Abstract

This paper focuses on the regulation of pole-to-pole voltage in 3-Pole PV Based DC Microgrid (3-PPDM). This type of microgrid is conceived to mimic in dc microgrid, the operational feature of grid-connected three-phase ac microgrid where no transformer is required at distribution level for the provision of different voltage levels (phase and line) operation within the ac microgrid. 3-PPDM is developed with PV Based DC Microgrid connected to ac grid via single stage dc link and 3-Level Voltage Source Converter (3L-VSC). Operation of distributed flexible dc loads at lower voltage level on the dc link without dc-dc converters cause voltage imbalance among poles. This imbalance violates the technical constraints for desirable operation of both the 3L-VSC and distributed dc loads. Distributional effects of this violation are reduction in dc link voltage and grid parameters (voltage and current) qualities. Consequently, distributed Pulse Width Modulation (d-PWM) based algorithm was developed together with a 2-in-1 Tank Circuit (TC) to regulate this imbalance under slowly/rapidly varying irradiance by bringing the voltage differential among poles nearly to zero. The simulation results obtained under rectification and inversion operational mode of 3L-VSC show marginal improvement in dc link voltage and grid current qualities at reduced operational cost.