Electric Engineering Department, Polytechnic University of Catalonia (EEBE-UPC), 08019 Barcelona, Spain.
Department of Energy Technology, Aalborg University, 9200 Aalborg, Denmark.
Sensors (Basel). 2023 May 18;23(10):4874. doi: 10.3390/s23104874.
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.
分布式发电（DG）与配电系统（DS）的集成，为客户提供了更可靠、更高效的电力输送。然而，双向功率流的可能性为保护方案带来了新的技术问题。这对传统策略构成了威胁，因为继电器的设置必须根据网络拓扑和运行模式进行调整。因此，开发新的故障保护技术来确保可靠的保护和避免不必要的跳闸是非常重要的。在这方面，总谐波失真（THD）可以用作评估故障期间电网波形质量的关键参数。本文比较了两种 DS 保护策略，它们使用 THD 水平、估计幅度电压和零序分量作为故障期间的瞬时指标，作为一种故障传感器，用于检测、识别和隔离故障。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 来实现相同的目的（SOGI-THD）。这两种方法都依赖于保护设备（PD）之间的通信线路来实现协调保护。通过在 MATLAB/Simulink 中进行仿真，考虑了不同类型的故障和 DG 渗透率、不同的故障电阻和建议网络中的故障位置等各种因素，评估了这些方法的有效性。此外，还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 方法仅使用三个 SOGIs 就能在 6-8.5ms 的时间间隔内有效地检测和隔离故障，执行仅需 447 个处理器周期。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内容，并避免了故障检测过程中的干扰。
