A Two-Layer Control Scheme Based on P – V Droop Characteristic for Accurate Power Sharing and Voltage Regulation in DC Microgrids

Abstract

The increasing penetration of dc distributed energy resources (DERs) and dc loads has motivated the utilization of dc microgrids (MGs). In this paper, a new two-level control scheme is proposed for accurate power sharing and appropriate voltage regulation in dc MGs during islanded operation mode. In the primary control level, a P-V ̇ droop method is proposed to eliminate the dependency of power sharing among DERs on line resistances. Since the P-V ̇ droop deviates the voltage derivative to a nonzero value, a voltage derivative restoration mechanism is adopted in the secondary control level to provide voltage stability. The secondary control level also compensates the voltage deviations by cascading an outer voltage control loop with the inner voltage derivative restoration loop. The secondary control signal is broadcasted to each DER via a unidirectional lowbandwidth communication link. Small signal stability of the proposed scheme is analyzed by studying the locus of the system eigenvalues. To verify the efficacy of the proposed method and compare it with the conventional scheme, real-time simulations in OPAL-RT lab setup are provided. keywords-Distributed energy resources, DC microgrids, power management, voltage regulation.

Robust, Accurate, and Fast Decentralized Power Sharing Mechanism for Isolated DC Microgrid Using Droop-Based Sliding-Mode Control

“…For evaluating the efficiency of the proposed DBSMC control strategy in the field of the isolated buck converterbased DC MG, the real-time digital simulation method is performed, using the RTDS system of Figure (18) consisting of five PB5 processing cards. The proposed DBSMC controller is exerted to the studied isolated DC MG in a real-time digital simulation, in varying operating conditions and in the presence of structured uncertainties and external disturbances, just like Cases 1 and 2 and under the same conditions.…”

“…) |S|dt ≤ V (0) < ∞ (B 18). Since ρ > (ξD max , so:∞ 0 (ρ − (ξD max ) |S|dt ≥ 0.This positive value will be limited.…”

“…A low bandwidth communication network can improve the load sharing accuracy [17]. In [18], a two-level control technique is suggested for an islanded DC MGs, in such a way that, a P-V droop strategy and a voltage derivative restoration mechanism are utilized as primary and secondary control; respectively. However, the existence of communication network in the DC MG structure can increase the cost and stabilization time as well as reduce the reliability.…”

Modeling of Ship DC Power Grid and Research on Secondary Control Strategy

“…In order to address the issue of voltage ripple, Zhang Qinjin [17] suggested a DC microgrid power distribution method based on active frequency injection, adding a mode switching segment to the parallel current sharing control system based on frequency injection, and the mode is ordinary droop control in steady state to solve the problem of voltage ripple. Mehdi Baharizadeh [18] proposed a two-layer control scheme based on P-dv/dt droop characteristics for precise power sharing and voltage regulation of DC microgrids. The trade-off between damping and sharing accuracy must be taken into account while setting the rappel factor.…”

An Adaptive Backstepping Sliding Mode Cascade-Control Method for a DC Microgrid Based on Nonlinear Virtual Inertia

“…This control method is easy to meet the fixed switching frequency requirements and demonstrates the strong robustness of sliding mode control. The reference [23] proposes a cascade control scheme with a conventional droop control method for the outermost control and an internal cascade control scheme consisting of a voltage derivative control inner loop and a voltage control outer loop. The control method achieves accurate power-sharing and proper voltage regulation of the DC microgrid in islanded operation mode.…”