Doost Mohammadi F, Keshtkar H, Dehghan Banadaki A, Feliachi A
Christopher Newport University, Newport News, VA, 23606, USA.
California Polytechnic State University, San Luis Obispo, CA, 93407, USA.
Heliyon. 2019 Jun 27;5(6):e01823. doi: 10.1016/j.heliyon.2019.e01823. eCollection 2019 Jun.
This paper proposes a novel cooperative secondary control strategy for microgrids which is fully distributed. There is a two-layered coordination, which exists between inverter based DGs of both types, i.e. Voltage Source Inverter (VSI) and Current Source Inverter (CSI), also called PQ inverter. In first layer of the proposed two-layered cooperative control strategy, VSIs will take care of the primary average voltage regulation by implementing the average consensus algorithm (ACA); then in the second layer of control, the PQ inverters will improve the voltage quality of the microgrid while maintaining the average voltage of buses at the same desired level. Zone dedication algorithm is utilized in the second layer for voltage quality purposes based on sensitivity analysis. The sensitivity analysis is based on Simplified Jacobian matrix and the result of that is used to define the zone related to each DG in the microgrid. The goal of this zone dedication is to assign loads to the DGs that can compensate their changes with less effort (generating less power) than the others. There are two major contributions in this paper; 1- PQ inverters are effectively involved to increase microgrids capacity for better power management by introducing sensitivity to the PQ inverters set-point. This is defined based on the structure of the microgrid and takes into account the location of load changes. 2- The proposed strategy not only focuses on transient response but also improves the steady state response which smooths the voltage profile of the system while keeping the average voltage at the same desired level. The algorithm has been applied to a 13 bus system with a fully distributed communication in which each VSI inverter only communicates with its immediate neighbors and each PQ inverter is only in touch with associated bordering agents. The conclusive results verify that the proposed control strategy is an effective way to control the microgrid's voltage to have a smoother and stable voltage profile. The analysis also confirms the robustness of the proposed cooperative control in presence of possible time delays.
本文提出了一种全新的适用于微电网的完全分布式协同二次控制策略。在两种基于逆变器的分布式电源（DG）之间，即电压源逆变器（VSI）和电流源逆变器（CSI，也称为PQ逆变器），存在两层协调机制。在所提出的两层协同控制策略的第一层中，VSI将通过实施平均一致性算法（ACA）来负责一次侧的平均电压调节；然后在第二层控制中，PQ逆变器将在保持母线平均电压处于相同期望水平的同时，提高微电网的电压质量。基于灵敏度分析，在第二层中利用区域划分算法来改善电压质量。灵敏度分析基于简化雅可比矩阵，其结果用于定义微电网中每个DG相关的区域。该区域划分的目标是将负载分配给那些能够比其他DG以更小的努力（产生更少的功率）来补偿其变化的DG。本文有两个主要贡献：1 - 通过引入对PQ逆变器设定点的灵敏度，使PQ逆变器有效地参与进来，以提高微电网进行更好的功率管理的能力。这是基于微电网的结构定义的，并考虑了负载变化的位置。2 - 所提出的策略不仅关注暂态响应，还改善了稳态响应，在保持平均电压处于相同期望水平的同时，平滑了系统的电压曲线。该算法已应用于一个具有完全分布式通信的13节点系统，其中每个VSI逆变器仅与其直接相邻的节点通信，每个PQ逆变器仅与相关的边界代理进行联系。最终结果验证了所提出的控制策略是控制微电网电压以获得更平滑和稳定电压曲线的有效方法。分析还证实了所提出的协同控制在存在可能的时间延迟情况下的鲁棒性。
