Sharif Digital Repository

This article proposes two novel approaches to improve the superimposed frequency droop scheme for the control of dc microgrids (MGs). Conventional voltage-based control strategies suffer from issues such as undesirable voltage regulations, poor power sharing among the sources, and negative effects of line resistances on the equivalent droop characteristics. To overcome these challenges, a superimposed frequency droop scheme has been introduced. However, this method suffers from three major issues: 1) instability in terms of load variation, which is due to the location of system dominant poles; 2) limitation in system loading due to the limitation in the transferred reactive power; and 3)... 

This paper proposes an adaptive droop characteristic to enhance the superimposed droop frequency scheme for the control of DC microgrids. Conventional superimposed droop frequency scheme solves the poor current sharing and undesirable voltage regulation issues in DC microgrid. However, this method suffers from two main problems which are (i) instability in terms of load variation due to the limitation in transferrable reactive power, and (ii) poor voltage quality caused by the injected AC voltages in the DC system. In this paper, an adaptive droop characteristic is proposed to decrease the transferred reactive power and mitigate system overall voltage quality, and its performance is verified... 

In this paper a novel droop approach for power management in low voltage dc MicroGrids (MGs) based on a master-slave concept is presented. A virtual frequency is injected by a master unit, which is proportional to its output power. Other slave units determine their output power according to the corresponding frequency based droop characteristics. Unlike the dc voltage-droop methods, the proposed virtual frequency-droop approach can be smartly applied for proportional power management among the energy units and loads as well as adding zero net energy capability to the MG. Both power flow and energy flow can be performed without utilizing an extra communication system. Simulation results... 

In this paper, a novel droop approach for autonomous power management in low voltage DC (LVDC) microgrids based on a master-slave concept is presented. Conventional voltage-based droop approaches suffer from poor power sharing due to line resistance effects on a virtual resistance, which is solved by introducing a communication system to increase the current sharing accuracy. In this paper, a virtual frequency is superimposed by the master units, and slave units determine their output power according to the corresponding frequency-based droop characteristics. Unlike the voltage-droop methods, the proposed virtual frequency-droop approach can be applied for proportional power management among...