The Study For Low-frequency-low-voltage Automatic Load Shedding Device

The characteristics of modern power system are large capacity generators, extra-high voltage lines, large-scale and long-distance transmission interconnection, The reliability and economical efficiency of power supply have been significantly increased. But the system has become increasingly network-dependent, the system frequency and votage collapse has always existed. To ensure the quality of power supply, ensure stable operation of power system security, to prevent the power system frequency and voltage collapse accidents of one of the measures is to use low-frequency-low-voltage load shedding equipment. Power system of the "three lines of defense" concept put forward, more enhanced low-frequency-low-voltage load shedding equipment status. With the power of China in recent years, technology and computer technology, computer-based low-frequency-low-voltage load shedding equipment in power system by set to get more and more widely used. Centralized computer which low-frequency-low-voltage load shedding equipment more rapid development momentum, the market is very good.In this article, Fully discussed the power system principles of low-frequency-low-voltage load shedding; studied the power system frequency characteristics, the affect of frequency deviation and voltage deviation; Probed the improved frequency and under voltage load shedding strategy, proposed the"emergency wheel +basic wheels +spare whee"low-frequency voltage load shedding mode, and to take various measures to effectively reduce the occurrence of excessive removal; Analyzed various frequency algorithms, including the cycle method, analytical method, error minimization algorithm, orthogonal to the modulation method, is proposed to improve frequency algorithm, is introduced adaptive phasor algorithm based on the traditional zero-crossing frequency measurement, simulation and practical application results show the reliability and practicality of the algorithm; designed based on digital signal processor (DSP) and microprocessor (MCU) centralized low-frequency-low-voltage load shedding equipment, Details of the device hardware and software programs, and low-frequency-low-voltage load shedding control logic, and a brief description of the low-frequency-low-voltage load shedding capabilities development work, introduced the RTDS and the device test results on the RTDS.This device developed by has through a static model test at the National Center of Quality Supervision & Test of Relay (NCQTR),and has through real-time digital simulation system (RTDS) tests at the North China Electric Power Research Institute (NCEPRI), and has received applications in the field.