A novel slack bus-free load flow method for dc microgrids and distribution systems with dc-bus signaling control methods

Abstract

SUMMARYA significant section of the future electrical power systems, that is, smart grids, will be dc microgrids and distribution systems. Obviously, the voltage control is one of the important issues of these dc power systems. DC-bus signaling (DBS) control methods, as distributed, autonomous, simple, highly reliable, inexpensive, modular and practical control methods, are one of the most important categories of the voltage control methods in dc microgrids and distribution systems. In the dc power systems with DBS control methods, the determination of the generated power shares of the distributed power sources, as vital entries for the conventional load flow methods, before the execution of a load flow method, is not possible. Also, in these dc power systems, none of the power sources can be considered as a constant voltage source, that is, the slack source. Consequently, the conventional load flow methods are not applicable to dc microgrids and distribution systems with DBS control methods. In this paper, a novel, practical, robust, fast, precise load flow method is presented to overcome the mentioned serious complexities in the dc power systems. The proposed load flow method necessitates the least input data. It determines the generated power shares of all the sources during its execution. Besides, the load flow method necessitates no constant voltage source or slack source. Furthermore, the proposed load flow method benefits from low computational time and the storage requirements and the removal of the ill-conditioned problem. The algorithm validation and the numerical results derived in this paper confirm the accuracy and the remarkable performance of the load flow method.

Application of linearised load flow method for droop‐controlled DCMGs

“…However, a major shortcoming of this paper is that Farooq et al [8] neglected primary-level droopcontrol effect. Asad and Kazemi [9] proposed a modification to the distribution load flow technique to incorporate the effects of droopcontrol/DC bus signalling. However, the method proposed is only valid for a radial system.…”

“…• In [7][8][9][10][11][12][16][17][18], the researchers proposed recursive or iterative techniques such as Newton-Raphson, trust region-dogleg algorithm, forward-backward power flow etc. to solve a set of non-linear equations for obtaining the steady-state system variables.…”

“…Recursive/iterative methods are time-consuming and computation intensive. The method proposed in [9] does not require the calculation of Jacobian elements. The method employs the backward-forward distribution load flow technique to solve the set of non-linear algebraic equations.…”

“…• Fast, accurate, linear technique applicable to radial/non-radial grid-connected/islanded systems: Some researchers modelled the primary-level droop control in their works [7,9,10,12,17]. However, all these papers used iterative techniques such as Newton-Raphson method [17], backward-forward algorithm [9], and trust region method [7,10]. The method proposed in this paper solves a set of linear algebraic equations, and hence, there is no need for calculating the Jacobian elements.…”

An accurate current sharing method for an Islandeddroop‐controlled dcmicrogrid without communication between remote buses

“…Increased penetration of DC loads and sources and availability of advanced power electronic converters are making DC microgrid (DCMG) a viable and attractive option. [1][2][3][4][5][6][7][8][9][10] Researchers have focused on developing a suitable control strategy for reliable and stable operation of a DCMG. Droop control strategy at the primary control level has emerged as the most popular choice for autonomous and secure load sharing in a DCMG.…”