Application And Research Of Frequency Control Technology In Direct Air Cooling System

China is a country with extremely short water resources.In order to save water resources,more and more power plants are using direct air-cooling technology to cool the steam discharged from steam turbines at this stage,especially in areas where there is a shortage of water resources,direct air cooling technology is the only option for power plant cooling technologies in the area.Direct air cooling system with a large number of fans and pumps,in the traditional baffle speed control mode,these energy-consuming units to the power plant caused a lot of power loss.Therefore,it is imperative to carry out frequency conversion in the direct air cooling system of the power plant.This paper first introduces the working principle and advantages of the direct air cooling system,and analyzes the reasons for using the VVVF(frequency control)technology in the direct air cooling system,followed by the development process of power electronics,introduces the development history of VVVF technology and research status at home and abroad.The second part of the paper introduces the inverter which is the core equipment of the VVVF technology in detail,and expounds the working principle of the inverter and the main classification of the inverter respectively.At the same time the principle of speed regulation of the inverter is explained based on the principle of the motor.Then through the analysis of the mechanical characteristics and working principle of the motor,this paper studies the energy-saving research of the VVVF technology for two kinds of loads,fan and water pump.The results show that the use of VVVF technology in direct air cooling system can greatly reduce energy consumption.And through the two cases of actual transformation,the data proves the economic benefit brought by VVVF technology.In order to further enhance the energy-saving quality of the direct air cooling system,a reasonable optimization and control strategy for the variable frequency speed regulation system can realize the deep energy saving from the perspective of the system itself.In this paper,a detailed analysis of the loss of frequency control system,the loss of the entire system is divided into two types:uncontrollable loss and controllable loss.For controllable loss,three optimization control strategies are proposed:constant-slip energy-saving control,energy-saving constant power factor control and direct energy-saving step-down control.And describes the realization of three control strategies.Finally,this paper introduces the NOORII air-cooled frequency conversion project in Morocco,including the project design,commissioning procedures and summary of the problems.Through a complete project explains how the VVVF technology in direct air cooling system is applied,and through some experimental data,the energy saving effect of field application is simply analyzed.