Abstract
Microgrid faces various challenges such as reverse power flow, peak power demand, voltage limit violations, etc., due to significant installations of renewable energy sources (RESs) and electric vehicles (EVs). For continuous and effective operation of such a system, enhanced and complex control methodologies are needed. Smart transformer (ST) has emerged as a promising solution for overcoming such challenging issues. This paper proposes the operation of battery energy storage system (BESS) integrated ST in a meshed hybrid microgrid. Instead of connecting through ac interconnections with normally open (NO) circuit breakers (CBs), the same line is connected through the medium voltage (MV) dc links of ST. This introduces several paths for controlled power flow in the system. As compared to ac interconnections, this configuration improves the performance of the overall system during various adverse operating conditions such as reverse power flow, peak power demand, and voltage sag. Moreover, the MVDC line voltage is controlled by one ST, resulting in reduced control complexity of other power converters. Detailed simulation and experimental results are provided to show the merits of the proposed system.
Highlights
Renewable energy sources (RESs) such as photovoltaic (PV), wind, etc. are emerging as a sustainable solution for growing energy needs
This control concept can be extended to a three-grid/multi-grid system with one of the Smart transformer (ST) controlling the MVDC link voltage and other STs controlling the power flow based on the mode of operation
SIMULATION RESULTS Simulation is conducted in PSCAD software and the parameters are shown in Table 1 and Table 2
Summary
Renewable energy sources (RESs) such as photovoltaic (PV), wind, etc. are emerging as a sustainable solution for growing energy needs. The peak power production from PV sources leads to high reverse power flow in the microgrid during low-load hours, and voltage magnitude rise can cause irreversible damage to the connected equipments [3]. The voltage rise due to reverse power flow is handled by solutions such as on-load tap changers (OLTCs) [5], and active power control of PV inverters [6]. The ac interconnections with normally open (NO) circuit breakers (CBs) are conventionally used for the microgrid interconnections, the system has limited power control features. In this scenario, the medium voltage (MV) dc interconnection to the ac microgrids provide advantages such as flexible active power transfer capability, independent active.
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