Design of an online intelligent alarming system for cascading failures of group of wind farms

In China, large-scale wind power is integrated to the power grid in a concentrating way by connecting a group of wind farms together. Each wind farm is consisted of hundreds of wind turbines and covers a large geographical area. However, such a system is vulnerable to occasional faults which can easily develop into cascading failures of adjacent wind farms, making the wind farms lose most of their power in a very short time. Cascading failures have occurred several times in reality. It is urgently necessary to construct an online assistant system to detect, analyze and explain the cascading events timely and effectively. Given that Phasor Measurement Units (PMUs) are widely installed in Chinese wind farms, the dynamic process can be recorded effectively, supplemented with Supervisory Control and Data Acquisition system (SCADA) signals. In this paper, a conceptual design of an online intelligent alarming system for cascading failures of wind farms based on PMUs and SCADA is introduced. The system is justified using real data collected in wind farms.

I. Introduction

Wind power has become the most important and practical renewable energy resource. By the end of October 2012, the total installation capacity of wind power in China reaches 52.22GW [1], [2]. Large-scale wind power is often distributed in sparsely populated districts and covers wide areas. It is first generated by wind turbines connected with low-voltage feeders within a wind farm, whose capacities are usually 1–3 MW. Then power from adjacent wind farms is gathered together through transmission lines to an extra high voltage substation, where the wind power is integrated to the main power grid. Such a system of wind farms is vulnerable to faults due to its wide-spreading area and close interconnections. Actually, a real system of a group of wind farms in northern China experienced several large-scale cascading failures every year. Security has become a major issue for large-scale integration of wind power in China.