微電網係指由分散式電源、儲能設備、交/直流負載、電力轉換器組成之區域型電網，其根據與市電端之併連形式可將運轉狀態分為併網模式與孤島模式。由於運轉模式與再生能源間歇性供電量之因素導致微電網電力潮流及故障電流大小與方向不為單一性，使得傳統電網之保護方式已無法滿足微電網之需求。

本文建立一套適用於微電網以SCADA為基礎之保護管理系統(PMS)，其中整合了合併單元(MU)與智慧型電子裝置(IED)，PMS採用IEC 61850通訊協定以實現資料高速傳輸與系統適應性保護，同時具備低阻抗故障保護與高阻抗故障保護之能力。於低阻抗故障保護策略中，透過MU將微電網各節點之電壓、電流及開關狀態等資訊回傳至SCADA，PMS經由取得之資訊執行拓撲分析、IED群組歸屬判斷及其方向性過電流保護設定，並回傳結果給各IED以達適應性保護之目的；於高阻抗故障保護策略中，亦透過MU傳回微電網各節點具時間標記之取樣電流值，由PMS執行取樣電流之時-頻轉換，並透過統計步驟運算高阻抗故障判斷指標，以達微電網高阻抗故障偵測與保護之目的。

本文以核研所微電網作為示範場域，透過Matlab/Simulink軟體建立微電網系統模型，模擬不同運轉情形下微電網保護管理系統(PMS)之應變能力。結果顯示PMS在不同微電網運轉情況下皆能順利偵測並排除故障，達到微電網全面性保護之目的。

Microgrid is a regional power grid composed of distributed generators (DGs), energy storage devices, AC/DC loads, and power converters. According to the interconnection with the utility, the microgrid can be operated in grid-connected mode and island mode. However, magnitudes and directions of power flows or fault currents in the microgrid may change accordingly since the intermittent characteristics and the operating modes of renewable energy. Therefore, traditional overcurrent protection schemes no more meet the protection requirements of the microgrid.

This thesis setups a SCADA-based protection management system (PMS) for the microgrid that integrates merging unit (MU) and intelligent electronic devices (IEDs). The IEC 61850 protocol is introduced to implement the high-speed data communication and the adaptive protection. The short circuit protection of the microgrid will focus on the ability of low-impedance fault protection and high-impedance fault protection. In the low impedance fault case, the information (such as voltages, currents for fault detection and circuit breaker status for topology analysis) are sampled by the MU, and then be transmitted to the SCADA platform via IEC 61850. Then, PMS in the platform performs the group assignment and relay setting of each IED. In the high-impedance fault protection strategy, the currents sampled by the MU with time stamp are transmit to the PMS. Then, PMS performs the time frequency transform of sampled currents and calculates the index of high impedance fault.

The microgrid of Institute of Nuclear Energy Research is used as a case study and is modeled by MATLAB/Simulink. In the simulation, several typical cases are carried out to test the fault detection capability of the PMS. The simulation results show that the PMS’s performance is satisfactory. Regardless of whether the short-circuit fault is low-impedance or high-impedance, the microgrid is fully protected.

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