An efficient multilevel interconnect control algorithm in AC/DC micro-grids using hybrid energy storage system

This paper presents a multilevel control method in two layers of micro-grids. Downstream grid (BatteryConverter Structure utilizing the distributed maximum power point tracking (DMPPT) for photovoltaic (PV) systems) and upstream grid (distributed generation (DG) sources with hybrid energy storage system (HESS)). In the downstream grid, each PV includes a DC/DC battery-converter with DMPPT. DMPPT converters can be used for voltage amplification and maintaining a constant PV voltage in the event of partial shading. To control the power and voltage in the upstream grid, hybrid energy storage systems (HESSs) distributed among AC/DC microgrids are introduced. Each storage unit has two basic tasks. First, it controls the voltage of the node which as storage unit is connected (local node). Second, it controls the node identified as the global reference node on the grid. The output power of the HESS is controlled in such a way that the node voltage fluctuates in a predefined permissible range. This is due to fluctuations like load changes, reduced power of DGs or power constraints in DGs. To determine the power reference for each HESS, the state of charge (SoC) is considered matched to the dead-band droop control. Simulations were performed by MATLAB/Simulink.

Automated summary

This paper presents a multilevel control method in two layers of micro-grids, utilizing distributed maximum power point tracking for photovoltaic systems and hybrid energy storage system for distributed generation sources. The control strategies for power and voltage regulation in both downstream and upstream grids are discussed, with detailed explanations on how DC/DC battery-converter with DMPPT and HESS are used. Simulations were conducted using MATLAB/Simulink to validate the proposed control method.