Research On Energy-Saving Fuzzy-Frequency Control Equipment Of Large And Middle Transformer Cooling System

Large and medium transformer is one important equipment of power plants and substations. With the continuous enlarge scale of power system and voltage levels increasing, currently the total capacity of the transformer had reached 9-10 times of the total power generation capacity.These is the iron loss and copper consumption during the transformer operation , which will be converted into heat caused radiation, than can lead to the riseing temperature for the transformer, in order to ensure good heat dissipation for the transformer, it must be using a certain cooling way to take away the heat generated by the transformer, otherwise, it can cause the temperture rising, if it exceed the allowable limit, can cause the transformers from reducing the service life to been damaged heavily. According to research, the transformer winding temperature increasing by 6℃above the temperature limit, the use of life will be shortened by half. Therefore, the study on the safety of energy-saving operating mode for the transformer cooling system, enterprises energy saving, controlling the cost of the power generation and power supply, reducing the power consumption of the substations will have great significant.With the power electronics technology developing, the variable frequency technology is becoming mature by step, and been widely used in practices, which caused the prices of finished transformer declined andthe operation stability and reliability also greatly enhanced. Using of variable frequency technology to control and adjust the output power of the cooling device of the large power transformers equal to the total loss of the transformers, combined with the feedback regulation of the transformer oil temperature and ambient temperature, can control the transformer top oil temperatureina given range of smaller, it will have great significance for the transformer security, economic operation and to extend its life.Although using the inverter technology in conjunction with the feedback of the transformer oil temperature and environmental temperature has been able to control and adjust the output power of the cooling device of the large power transformers equal to the total loss of the transformers, thus it can control the upper transformer oil temperature in a smaller to within the given range and improve the transformer to run security and economy. But the relationship between the cooler input power and the amount loss power of transformer is difficult to accurately calculate, so simply using the conventional PID will inevitably cause energy waste on controlling the temperature deviation large or small, and when the fan had small speedt to frequent adjustmentsinevitably. Therefore, it is introduced fuzzy control composed the Fuzzy_PID compound control based on the conventional PID control, using the the PID controlling proportion to improve the dynamic response speed, using the PID controlling integral to eliminate steady-state error, thus it will improve the steady-state performance of fuzzy control.Using this compound control method to adjust the cooling speed of the motor to ensure heating and cooling of the real-time balance high-precision for the transformer, so that the transformer is always in high economy state, and can prolong the transformers service life. Variable frequency technology controlling the transformer startting can effectively reduce the impact current when the motor startup, thereby it can prolong the life of the fan motor.The device uses PLC as the core control unit, using PLC program control to replace the original relay control circuit, so it can to overcome the conventional hard-contact cooling control system and the hard-wired logic control and thehigh failure rate of the shortcoming. Using the PLC built-in Modbus-RTU master function to compose the simple serial communication network, it can realize Serial Communication of the PLC and frequency converter, PLC and the local thermometer, long-range serial communications devices. At the same time, PLC's CPU unit constitutes is high-speed processing speed is also a necessary condition to compose fuzzy-PID controller. Another, PLC is rich communication interfaced to support multiple communication protocols, which can improve the automation of substations or power plants management level by interfacing with the substation or power plant computer control system.Practice shows that the device has high reliability, precise controlling and energy-saving effect obviously, and can extend the life of transformer and the cooling fan, it can meet the requirements of large and medium-sized transformer cooling control device intelligent control.