An Improved Droop Control Method for DC Microgrids Based on Low Bandwidth Communication With DC Bus Voltage Restoration and Enhanced Current Sharing Accuracy

Abstract

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On Secondary Control Approaches for Voltage Regulation in DC Microgrids

“…G is the n×n conductance matrix of MG, which can be calculated as (5), Gd is a diagonal matrix which includes the droop conductance of the droop controlled converters, which can be calculated as (6), and n is the total number of busses. …”

“…In short feeders the resistance of lines and voltage drop on the lines are small, hence, the differences in voltage levels will be small. Here the following approaches, which employ different voltage regulation schemes, have been considered:  Approach I: regulating the average voltage of generator busses [6], [10], [11], V1, V4 in The effects of the different control approaches on voltage regulation are explained in the following.…”

“…In centralized schemes, the voltage of localized loads connected to a common bus or the voltage at the coupling point into the utility grid should be regulated [9], [10]. On the other hand, in decentralized methods, the average voltage of generator busses (busses with voltage source converter), is controlled [6], [7], [10]- [12], [16] In the centralized secondary approach, it is considered the loads are localized at a common buss and the secondary controller regulates the voltage of the common bus at a reference value. A central control unit measures the voltage of common buss and send the set point voltage to the voltage controlled converters [8]- [10].…”

“…The voltage or voltages of some busses are communicated among the converters. The secondary control of each converter regulates the average voltage of these busses [6], [8], [12]. Furthermore, in order to improve the system resiliency and reliability, a consensus protocol based secondary approaches are presented in [11], [17], where only the voltage of generation busses are communicating among the converters.…”

Voltage control of DC islanded microgrids: A decentralized scalable approach

“…Existing controllers for the stabilization of DC ImGs are mainly based on droop control [5], [13], [14] and stability analysis has been performed only for specific ImGs [5], [13], [14]. Similar approaches to voltage stabilization have been also used for multi-terminal high voltage DC systems [15].…”