عنوان مقاله
یک روش ساده برای تشخیص حالت جزیره ای با یک منطقه غیر قابل شناسایی ناچیز
فهرست مطالب
مقدمه
سیستم مورد مطالعه
روش پیشنهادی تشخیص حالت جزیره ای
عملکرد روش پیشنهادی تشخیص حالت جزیره ای در طی شرایط جزیره ای
نتیجه گیری
بخشی از مقاله
مزیت ها ی این روش پیشنهادی شامل :
1) بر خلاف تعدادی از روش های فعال شناسایی حالت جزیره ای که قبلا اشاره شد، روش پیشنهادی هیچ بلوک کنترل اضافی نیاز ندارد.
2) بر خلاف اهمیت روش های غیرفعال، روش پیشنهادی، NDZ ناچیز دارد.
3) روش ساده و آسان برای اجرایی شدن است و براساس به کارگیری روش OVP/UVP عمل می کند.
نتایج شبیه سازی، کارآمدی روش پیشنهادی شناسایی حالت جزیره ای را نشان می دهد.
کلمات کلیدی:
A Simple Technique for Islanding Detection With Negligible Nondetection Zone H. H. Zeineldin, Member, IEEE, and James L. Kirtley, Jr., Fellow, IEEE Abstract—Although active islanding detection techniques have smaller nondetection zones than passive techniques, active methods could degrade the system power quality and are not as simple and easy to implement as passive methods. The islanding detection strategy, proposed in this paper, combines the advantages of both active and passive islanding detection methods. The distributed-generation (DG) interface was designed so that the DG maintains stable operation while being grid connected and loses its stability once islanded. Thus, the over/undervoltage and over/underfrequency protection method would be sufficient to detect islanding. The main advantage of the proposed technique is that it relies on a simple approach for islanding detection and has negligible nondetection zone. The system was simulated on PSCAD/EMTDC and simulation results are presented to highlight the effectiveness of the proposed technique. Index Terms—Distributed generation (DG), inverter, islanding, over/underfrequency, over/under voltage. I. INTRODUCTION I SLANDING is a condition in which a part of the utility system, which contains load and generation, is isolated from the rest of the utility system and continues to operate. An islanding event could occur as a result of a fault on the upstream feeder of a distribution substation which could lead to the operation of the main feeder recloser. The recloser will attempt to close after a certain time interval (usually between 500 ms to 1 s). The islanding detection method should be capable of operating in a timely manner to avoid damages that could result from reclosing on an energized network. There are three main categories for islanding detection methods which include: 1) passive, 2) active, and 3) communication-based methods. Passive methods rely on monitoring a certain parameter and then setting thresholds on the selected parameter. Despite its simplicity and easiness to implement, passive methods suffer from large nondetection zones (NDZs). NDZs could be defined as the loading conditions for which an islanding detection method would fail to operate in a timely manner. Selecting suitable thresholds for passive methods that rely on monitoring THD and voltage unbalance becomes a hard and complex task since these parameters are system Manuscript received March 06, 2008; revised May 19, 2008. Current version published March 25, 2009. This work was supported by the Masdar Institute of Science and Technology. Paper no. TPWRD-00121-2008. H. H. Zeineldin is with the Masdar Institute of Science and Technology, Abu Dhabi, United Arab Emirates (e-mail: hatem@MIT.EDU). J. L. Kirtley, Jr. is with the Massachusetts Institute of Technology, Cambridge, MA 02139 USA. Digital Object Identifier 10.1109/TPWRD.2009.2013382 dependent [1]. Active methods introduce deliberate changes or disturbances to the connected circuit and then monitor the response to determine an islanding condition [2]. Active methods have smaller NDZ but, on the other hand, can degrade the power quality of the system [2]. In addition, some active methods require the implementation of addition controllers which increases the complexity of the islanding detection method [3]–[5]. Communication-based methods have negligible NDZ but are more expensive than the former methods. A comprehensive survey on the different islanding detection methods could be found in [2] and [6]. In this paper, we aim to develop a new islanding detection technique that would incorporate the advantages of the three islanding detection categories while avoiding their drawbacks. The DG interface control under study is designed to operate at unity power factor and the load is modeled as a constant RLC load. The proposed method relies on designing the DG interface so that the DG maintains stable operation while being grid connected and loses its stability once islanded. A simple and easy to implement method, such as the over/undervoltage and over/underfrequency protection (OVP/UVP and OFP/UFP), is used to detect an islanding condition. The OVP/UVP and OFP/UFP method relies on monitoring the voltage and frequency at the DG interconnection point. Once the magnitude of either one exceeds a prespecified threshold value, an islanding condition is declared and the DG is disconnected. The paper is organized as follows: Section II presents the system and DG interface model under study. Section III presents the proposed islanding detection method. Section IV provides simulation results that highlight the performance of the proposed islanding detection technique. Section V highlights the impacts of system voltage variations on the proposed technique and presents an extension to the proposed islanding detection method. Finally, conclusions are drawn in Section VI.
