Abstract

This paper presents the islanding detection and automatic mode switching for inverter-based distributed generation sources (DGs) in the microgrid with an improved droop controlled scheme. The modification in the conventional droop among the DGs is contrived to share the load proportionate to their power capacity. And to reduce the circulating currents and to improve reactive power-sharing the virtual impedance is implemented for the microgrid in the stand-alone mode operation. Also, the modified Park synchronous reference frame based phase-locked loop (PSRF-PLL) is implemented for the operation of the microgrid in the grid-connected mode. The islanding detection and automatic mode switching depend on the PSRF-PLL, which uses the input obtained from the stationary reference frame. The proposed PLL implemented in this work is simple in construction and keeps the phase locking error to near zero, thus leading to proper locking with reduced complexity. The control scheme's performance in the microgrid is validated using the real time hardware in the loop platform. The performance of PSRF-PLL based islanding detection scheme is analyzed considering the various grid disturbances, and the comparative study with the other PLL based scheme is also presented in this paper to show the improved performance of the proposed PSRF-PLL scheme.

摘要

本文介绍了微电网中基于逆变器的分布式电源 (DG) 的孤岛检测和自动模式切换，采用改进的下垂控制方案。DG 之间传统下垂的修改旨在分担与其功率容量成比例的负载。并且为了减少循环电流和改善无功功率共享，在独立模式运行中为微电网实施了虚拟阻抗。此外，改进的基于 Park 同步参考系的锁相环 (PSRF-PLL) 用于微电网在并网模式下的运行。孤岛检测和自动模式切换取决于 PSRF-PLL，它使用从静止参考系获得的输入。在这项工作中实现的建议 PLL 结构简单，并将锁相误差保持在接近零，从而导致适当的锁定，同时降低了复杂性。该控制方案在微电网中的性能使用实时硬件在环平台进行验证。考虑到各种电网干扰，分析了基于 PSRF-PLL 的孤岛检测方案的性能，并在本文中介绍了与其他基于 PLL 的方案的比较研究，以显示所提出的 PSRF-PLL 方案的改进性能。