Abstract
When the line impedance is considered in the microgrid, the accuracy of load sharing will decrease. In this paper, the impact of line impedance on the accuracy of load sharing is analyzed. A robust droop control for a high-voltage microgrid is proposed based on the signal detection on the high-voltage side of the coupling transformer. For a high-voltage microgrid, the equivalent impedance of coupling transformer connecting distributed generator with the grid is usually the dominate factor. Compared with the conventional droop control strategy, the proposed control method in this paper detects the feedback signal from the high-voltage side of the coupling transformer. The impact of line impedance on the load sharing accuracy can be mitigated significantly. The proposed droop control only changes the detection point of the feedback signal, thus it is easy to be implemented. The PSCAD/EMTDC simulation results show the effectiveness of the proposed robust droop control concept in load sharing and voltage regulation with highly accuracy.
Highlights
In order to address the environmental pollution and energy crisis, many distributed generations (DGs), e.g., solar energy, wind energy, microturbines, and fuel cells are widely used. These DGs are connected to the utility grid via inverters, which are known as the microgrid [1, 2]
The high-voltage large scale microgrid for campus and island are most likely to be developed [18, 19]. In these kinds of microgrids, DGs are always connected to the utility grid by a step-up coupling transformer
If the robust droop method proposed in reference [8] is applied in the high-voltage microgrid as shown in Fig. 3, in addition to current flowing into AC common bus, the remote bus voltage V should be sampled by voltage sensors as shown in Fig. 4 with Ks connected to Channel 1
Summary
The accuracy of reactive power sharing using Q-V droop control is usually substantially affected by the equivalent impedance of DG and line impedance [10]. Reference [8] proposed a robust droop control and the robustness of the voltage output and load sharing accuracy could be enhanced obviously. It is only suitable for the centralized microgrid with communication equipment. The high-voltage large scale microgrid for campus and island are most likely to be developed [18, 19] In these kinds of microgrids, DGs are always connected to the utility grid by a step-up coupling transformer.
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