Cooperative Decentralized Tertiary Based Control of DC Microgrid with Renewable Distributed Generation

Abstract

This paper introduces a cooperative decentralized control strategy to control power management in a DC microgrid integrated with multiple energy Renewable energy sources (RES) mainly of Photovoltaic (PV), and conventional distributed generations (DGs). Control strategy is based on a hierarchical structure of primary, secondary and tertiary controllers. DC bus voltage signal is used to enable power sharing among different power sources and for seamless transition between modes of operation. Primary control is mainly based on an adaptive droop mechanism [1], [2] to regulate voltage output of each converter and balance generation amongst sources. Secondary controller is applied to measure voltage across the micro grid and update voltage setpoint for primary controllers. Consequently, Tertiary controller is a higher-level controller, that is responsible for the economic dispatch of all power sources in the whole dc microgrid cluster. A cooperative control strategy is applied to implement the primary, secondary and tertiary controllers. Recent research papers had implemented tertiary controller in a single mode dc microgrids to control voltage setpoints and perform economic dispatch of power generation. Moreover, this paper discusses stability issues introduced by constant power loads. Constant power loads (CPL) are one of the main factors causing destabilization in dc microgrids by which the main bus voltage shows significant oscillations and may collapse. Distributed generations are connected to the microgrid thorough Line Regulating Converters (LRC). However, novelty of this paper is in implementing cooperative decentralized voltage and current control, based on dead zone and power generation capacity, to mitigate voltage oscillations in dc microgrids and to reduce the entire generation cost by controlling voltage output of every single power converter. Ultimately, the effectiveness of the proposed technique is verified using MATLAB/SIMULINK 2016b based on a composite dc microgrid test system.