عنوان مقاله
تشخیص حالت جزیره ای برای DG مبتنی بر اینورتر با توجه به فرکانس کلید زنی آن
فهرست مطالب
مقدمه
روش تشخیص حالت جزیره ای مبتنی بر فرکانس کلید زنیPWM اینورتر
مطالعه در مورد سیستمDG واحد
مطالعه در مورد سیستم DG چندگانه
نتیجه گیری
بخشی از مقاله
سیستمDG سینگل متصل به گرید
در یک شبکه توزیع واقعی، فیدر بین ولتاژی بالا(HV) ولتاژ متوسط (MV) و ترانسفورماتورهای MV/LV در شکل 1 دارای یک امپدانس بزرگ از نظر بزرگی نسبت به امپدانس ترانسفورماتور در مقایسه با خطوط توزیع کوتاه در طرف LV می باشد. برای مثال، شبکه توزیع در بخشی از سئول کره جنوبی در شکل 1 نشان داده شده است.که فیدر های اتصال کوتاه در طرف LV با امپدانس کمتر از 0.05 p.u. دارد.
کلمات کلیدی:
New Islanding Detection Method for Inverter-Based Distributed Generation Considering Its Switching Frequency Soo-Hyoung Lee, Student Member, IEEE, and Jung-Wook Park, Senior Member, IEEE Abstract—Islanding detection is one of the most important issues for the distributed generation (DG) systems connected to an electric power grid. The conventional passive islanding detection methods inherently have a nondetection zone (NDZ), and active islanding detection methods might cause problems with safety, reliability, stability, and power quality on a power system. This paper proposes a passive islanding detection method with the zero NDZ property by considering the switching frequency from an inverter of the DG system. Moreover, the proposed method does not cause any negative effects in the aforementioned problems because it avoids applying the intended changes such as variations of reactive power and/or harmonics, which are required in the active islanding detection methods. Several case studies are carried out to verify that the proposed method can detect the islanding operation within 20 ms, which is less than 150 ms required in a recloser as the shortest mechanical reclosing (delay) time. Moreover, this value satisfies the requirement of 2 s given in IEEE Std. 1547. Index Terms—Distributed generation (DG), inductance concentration bus, islanding detection, load concentration bus, pulsewidth modulation (PWM) inverter, switching frequency. I. INTRODUCTION ACCORDING to the increased prices of fossil fuels such as oil and natural gas, it is expected that the electric power industry will undergo considerable and rapid change with respect to its structure, operation, planning, and regulation. Moreover, trends in power system planning and operation are being toward maximum utilization of existing infrastructures with tight operating margins due to the new constraints placed by economical, political, and environmental factors. The distributed generation (DG) system is one of the most possible solutions to deal with the aforementioned problems. The DG is based on the renewable energy sources such as fuel cell, photovoltaic, and wind power, as well as combined heat and power gas turbine, microturbine, etc. The number Manuscript received May 14, 2009; revised May 14, 2009 and November 3, 2009; accepted November 23, 2009. Date of publication May 10, 2010; date of current version September 17, 2010. Paper 2009- PSEC-114.R2, presented at the 2009 Industry Applications Society Annual Meeting, Houston, TX, October 4–8, and approved for publication in the IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS by the Power Systems Engineering Committee of the IEEE Industry Applications Society. This work was supported by the Human Resources Development Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea Government Ministry of Knowledge Economy (Grant 2007-P-EPHM-E-08-0000). The authors are with the School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea (e-mail: reasonable@yonsei.ac.kr; jungpark@yonsei.ac.kr). Digital Object Identifier 10.1109/TIA.2010.2049727 of DG systems is rapidly increasing, and most of them are connected to a distribution system by supplying power into the network, as well as local loads [1]. An islanding operation occurs when the DG continues supplying power into the network after power from the main utility is interrupted [2], [3]. If the islanding operation occurs, the distribution network becomes out of the utility’s control. It can therefore cause a number of negative impacts on the network and DG itself, such as the safety hazards to utility personnel and the public, the power quality problems, and serious damage to the network and DG unless the main utility power is restored correctly and quickly [1]. Furthermore, the DG system must be also disconnected from the network for its protection by the effective detection method before the recloser starts to operate following by the islanding operation. Two types of islanding detection methods, which are the passive and active methods, have so far been developed. Some representative passive methods detect the islanding operation by monitoring over-/undervoltage (OUV) and over-/ underfrequency (OUF) [4], [5]. The changes of voltage and frequency are caused by the mismatches of active and reactive power, respectively. However, these methods have the nondetection zone (NDZ), where the OUV/OUF-based detection method fails to detect the islanding operation. This NDZ is calculated by setting the threshold values for frequency and amplitude of the voltage [6]. In practice, the rate of change of frequency and vector-shift methods are very commonly used in the U.K. and other European countries [7]. Although these methods are effective in reducing the NDZ, they cannot remove it completely. The other passive methods using voltage unbalance (VU) and total harmonic distortion (THD) might determine the islanding operation even in the NDZ [1]. However, those passive methods still neither overcome the NDZ completely nor operate fast enough, despite using the VU and THD methods.
