Abstract Conventional protection schemes are not effective in microgrids due to the possibility of bi-directional current flow and fault level reduction in the islanded mode caused by converter interfaced Distributed Generations (DGs). This paper proposes a hybrid tripping characteristic based protection scheme for microgrids. The proposed characteristic uses both voltage and current measurements to decide the tripping time, thus it is called hybrid tripping characteristic. Same relay setting is used in both grid connected and islanded mode of operation of the microgrid. Therefore, communication facilities are not required in the proposed scheme unlike many existing communication-based solutions. Voltage measurement helps in differentiating low-fault-current situation from overloading condition. It also helps in the reduction of the operating time in islanded mode. Acceptable relay operating time is achieved in both grid connected and islanded mode. A coordination problem is formulated and solved with the proposed hybrid characteristic. The obtained protection coordination is independent of the operating mode of the microgrid. The performance of the scheme is evaluated using both PSCAD simulations and hardware experiments. It is found that the proposed protection scheme performs satisfactorily for various fault impedance values, fault locations, DG combinations, overload situations and measurement errors. The performance of the scheme has been compared with the existing schemes.

中文翻译：

---

基于混合跳闸特性的交流微电网无通信保护方案

摘要 由于转换器接口分布式发电 (DG) 导致孤岛模式中双向电流流动和故障水平降低的可能性，因此传统保护方案在微电网中无效。本文提出了一种基于混合跳闸特性的微电网保护方案。提出的特性使用电压和电流测量来决定脱扣时间，因此称为混合脱扣特性。在微电网的并网和孤岛运行模式中使用相同的继电器设置。因此，与许多现有的基于通信的解决方案不同，所提出的方案中不需要通信设施。电压测量有助于区分低故障电流情况和过载情况。它还有助于减少孤岛模式下的操作时间。在并网模式和孤岛模式下均可实现可接受的继电器操作时间。使用所提出的混合特性制定并解决了协调问题。获得的保护协调与微电网的运行模式无关。该方案的性能使用 PSCAD 模拟和硬件实验进行评估。发现所提出的保护方案对于各种故障阻抗值、故障位置、DG 组合、过载情况和测量误差都能令人满意地执行。该方案的性能已与现有方案进行了比较。使用所提出的混合特性制定并解决了协调问题。获得的保护协调与微电网的运行模式无关。该方案的性能使用 PSCAD 模拟和硬件实验进行评估。发现所提出的保护方案对于各种故障阻抗值、故障位置、DG 组合、过载情况和测量误差都能令人满意地执行。该方案的性能已与现有方案进行了比较。使用所提出的混合特性制定并解决了协调问题。获得的保护协调与微电网的运行模式无关。该方案的性能使用 PSCAD 模拟和硬件实验进行评估。发现所提出的保护方案对于各种故障阻抗值、故障位置、DG 组合、过载情况和测量误差都能令人满意地执行。该方案的性能已与现有方案进行了比较。发现所提出的保护方案对于各种故障阻抗值、故障位置、DG 组合、过载情况和测量误差都能令人满意地执行。该方案的性能已与现有方案进行了比较。发现所提出的保护方案对于各种故障阻抗值、故障位置、DG 组合、过载情况和测量误差都能令人满意地执行。该方案的性能已与现有方案进行了比较。