Study On Evaluation Method Of Power Supply Reliability Considering Voltage Sags

With the rapid development of high technology in today's society,the proportion of user-sensitive equipment has increased significantly,and the number of power interruption caused by voltage sag is increasing.These modern loads are sensitive to power quality problems such as voltage dips and short interruptions compared to conventional loads.It can be seen that the requirements of modern electric power load on power quality are getting higher and higher,and the requirements for power supply reliability are becoming more and more strict.Although the voltage sag does not cause complete interruption of the system and user power,it cannot guarantee the continuous power supply of the user,and the user cannot obtain the required power from the power supply system,thereby affecting or even destroying the continuous work of the user sensitive equipment or the production line,resulting in the user.The actual "continuous power interruption ".In order to meet the requirements of modern load on power quality,it is necessary to re-recognize the reliability assessment of power supply,and transfer the reliability assessment of power supply to the user experience.The quality of power directly felt by users is the key factor in evaluating the continuity of power supply and the quality of power supply in a power supply enterprise.This paper firstly studies the current situation and existing problems of voltage sags and power supply reliability evaluation indicators at home and abroad,and from the perspective of the impact of voltage sag on power users,aiming at the main indicators of power supply reliability in China's existing power supply reliability evaluation procedures,considering the impact of voltage sag,the corresponding sag equivalent power supply reliability supplementary index is established..Through the supplement and improvement of the original indicator system,the evaluation of power supply reliability from the perspective of user experience is realized.Then,a Monte Carlo method based stochastic simulation method is proposed to estimate the reliability index of the sag equivalent power supply.The method takes into account the operating characteristics of the relay protection,and considers the stochastic characteristics of the sensitive load withstand capability,and estimates the voltage sags and interruption event characteristics of the distribution network node and the frequency of load interruption,based on the random prediction results.Calculate the proposed sag equivalent power supply reliability index and the original indicator.The proposed method can comprehensively evaluate the current status of grid power quality and power supply reliability under the condition of known grid parameters,promote power quality management and engineering applications,and guide users to access sensitive loads.Finally,in order to make the proposed index more engineering practical and operability,this paper proposes a statistical evaluation method for the sag equivalent power supply reliability index of the actual grid operation.Collecting the monitoring data of the power quality monitoring system and the mining system to be evaluated;extracting the characteristic magnitudes such as the amplitude and duration of the voltage sag for each event;and investigating and obtaining the basic data of each power user at the monitoring point:including the basis Parameter data(such as user equipment type,equipment sensitivity,etc.)and actual operational data of the event(such as the daily output value of the sag,the economic loss caused by a single slam event,the number of abnormal equipment,power,etc.);based on the above basis The data calculates the sag equivalent power supply reliability indicator.The method provides an idea for the engineering application of the index,and verifies the engineering practicability of the index.With the installation and popularization of the power quality monitoring device of the user side,the acquisition of the basic data is more convenient.