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Abstract：
The integration of Distributed Generators (DGs) into distribution systems (DSs) leads to more reliable and efficient power delivery for customers. However, the possibility of bi-directional power flow creates new technical problems for protection schemes. This poses a threat to conventional strategies because the relay settings have to be adjusted depending on the network topology and operational mode. As a solution, it is important to develop novel fault protection techniques to ensure reliable protection and avoid unnecessary tripping. In this regard, Total Harmonic Distortion (THD) can be used as a key parameter for evaluating the grid\'s waveform quality during fault events. This paper presents a comparison between two DS protection strategies that employ THD levels, estimated amplitude voltages, and zero-sequence components as instantaneous indicators during the faults that function as a kind of fault sensor to detect, identify, and isolate faults. The first method uses a Multiple Second Order Generalized Integrator (MSOGI) to obtain the estimated variables, whereas the second method uses a single SOGI for the same purpose (SOGI-THD). Both methods rely on communication lines between protective devices (PDs) to facilitate coordinated protection. The effectiveness of these methods is assessed by using simulations in MATLAB/Simulink considering various factors such as different types of faults and DG penetrations, different fault resistances and fault locations in the proposed network. Moreover, the performance of these methods is compared with conventional overcurrent and differential protections. The results show that the SOGI-THD method is highly effective in detecting and isolating faults with a time interval of 6-8.5 ms using only three SOGIs while requiring only 447 processor cycles for execution. In comparison to other protection methods, the SOGI-THD method exhibits a faster response time and a lower computational burden. Furthermore, the SOGI-THD method is robust to harmonic distortion, as it considers pre-existing harmonic content before the fault and avoids interference with the fault detection process.
摘要：
将分布式发电机(DG)集成到配电系统(DS)中，可以为客户提供更可靠和高效的电力输送。然而,双向潮流的可能性为保护方案带来了新的技术问题。这对常规策略构成威胁,因为必须根据网络拓扑和操作模式来调整中继设置。作为解决方案,重要的是开发新的故障保护技术，以确保可靠的保护和避免不必要的跳闸。在这方面,总谐波失真(THD)可用作故障事件期间评估电网波形质量的关键参数。本文介绍了两种采用THD级别的DS保护策略之间的比较，估计振幅电压，零序分量作为故障过程中的瞬时指标，作为一种故障传感器来检测，identify,并隔离故障。第一种方法使用多个二阶广义积分器（MSOGI）来获得估计变量，而第二种方法使用单个SOGI用于相同的目的（SOGI-THD）。两种方法都依赖于保护装置(PD)之间的通信线路以促进协调保护。这些方法的有效性是通过使用MATLAB/Simulink中的仿真来评估的，考虑了各种因素，例如不同类型的故障和DG穿透，所提出的网络中不同的故障电阻和故障位置。此外，将这些方法的性能与传统的过电流和差动保护进行了比较。结果表明，SOGI-THD方法在仅使用三个SOGI的时间间隔为6-8.5ms的故障检测和隔离中非常有效，而只需要447个处理器周期即可执行。与其他保护方法相比，SOGI-THD方法具有更快的响应时间和更低的计算负担。此外，SOGI-THD方法对谐波失真具有鲁棒性，因为它在故障前考虑了预先存在的谐波含量，并避免了对故障检测过程的干扰。
