Synchronverter-Enabled DC Power Sharing Approach for LVDC Microgrids

Abstract

In a classical ac Micro-Grid (MG), a common frequency exists for coordinating active power sharing among droop-controlled sources. Like the frequency droop method, a voltage based droop approach has been employed to control the converters in dc MGs. However, voltage variation due to the droop gains and line resistances causes poor power sharing and voltage regulation in dc MG, which in most cases are solved by a secondary controller using a communication network. To avoid such an infrastructure and its accompanied complications, this paper proposes a new droop scheme to control dc sources by introducing a small ac voltage superimposed onto the output dc voltage of converters. Therefore, dc sources can be coordinated together with the frequency of the ac voltage, without any communication network like Synchronous Generators (SGs) in conventional power systems. Small signal stability analysis as well as mathematical calculations are presented to demonstrate the analogy between the proposed strategy and frequency-based droop approach of the SGs. The effectiveness of the proposed control system is evaluated by simulations and verified by experiments.

System-level lifetime-oriented power sharing control of paralleled DC/DC converters

“…So far, power management and load sharing approaches have been presented employing voltage droop method [18], [19] and frequency droop control [20], [21], where the load sharing among paralleled converters has been performed proportional to the corresponding rated powers. Furthermore, reference [22] presents another droop approach taking into account the power loss of converters and hence improving the overall system efficiency.…”

Proportional Load Sharing and Stability of DC Microgrid with Distributed Architecture Using SM Controller

“…To address the aforementioned challenges, different control schemes for DC microgrids are reported in [7,[10][11][12][13][14][15][16]. Commonly, these control schemes can be categorized as centralized and decentralized control [10][11][12][13][14][15][16][17][18][19][20][21].…”

On Secondary Control Approaches for Voltage Regulation in DC Microgrids

“…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].…”

“…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. Furthermore, a frequency droop based approach is also presented in [7], [16] in which the average voltage of generation busses can be properly regulated without utilizing any communication system. Furthermore, dc voltage in the dc MG is a local variable and voltage variation due to the feeder resistances at different points of MG is necessary in order to control the current flow.…”