Modification Design Of Primary Air Control System In A Coal Gangue 2×300MW Power Plant

At present,most of the high-voltage motors equipped with the primary fans of the boilers in thermal power plants adopt the operation mode of power frequency operation liquid coupling adjustment,which will cause a lot of energy waste.Therefore,reducing the ratio of production electricity consumption and reducing production pollution emissions are the transformation goals pursued by today’s thermal power plants.The primary fan is the main power-consuming equipment in thermal power plants,and the existing liquid coupling adjustment and control method of the primary air not only causes a lot of waste of electric energy,but also has a large starting current,causing shocks to the motor and high-voltage cables,and liquid coupling jams.The control method of the primary fan is in urgent need of transformation.This paper analyzes the problems existing in the existing hydraulic coupling control method of the two primary fans of a 2×300MW unit in a coal gangue power plant in Shaanxi.Using high-voltage frequency conversion control methods,the plant’s primary fans are designed for frequency conversion and energy saving.Designed a frequency conversion speed regulation system with a topological structure unit connected in series with a multi-level high-high voltage frequency converter as the core,including the selection of the frequency converter,the frequency converter control power supply and the cooling system,etc.;the primary wind frequency conversion energy-saving control program was designed,It mainly includes primary air pressure detection and constant pressure control system(realizing PID control on DCS),interlocking control of PLC-based inverter and local control,realizing the frequency conversion transformation of the two primary fans of the coal gangue power plant.This paper compares the energy-saving effects before and after the transformation,and analyzes the three-month trial operation data of a fan after the frequency conversion transformation.The energy saving rate under different loads reaches 30%-50%.After the frequency conversion transformation of the primary fan,the current value of the A side is reduced to 98.21 A under the 270MW load condition,and the energy saving rate is 49.18%at the 210MW load;the current value of the B-side motor is reduced to 127.28A under the 300MW load,at 150MW.The highest energy saving rate under load is 59.39%.A total of 3.15 million kilowatt-hours of electricity has been saved,and the energy-saving effect is remarkable.It is expected that the cost can be recovered in four years after the transformation and operation.And after the frequency conversion transformation,real-time monitoring and control of the frequency conversion speed regulation system by the DCS system can be realized;the bypass structure of the high-voltage frequency converter is used to realize the automatic switching between the power frequency frequency conversion and improve the stability of the primary fan system.