The FGI large-capacity medium voltage drive has successfully put into operation the power plant feed water pump renovation project
Electric feed water pumps play a crucial role in ensuring efficient and stable water supply to boilers in thermal power plants and are a key link for the stable operation of the power plants. At present, the speed regulation method of hydraulic couplings adopted by most electric feedwater pumps in thermal power plants has problems such as high power consumption rate, low speed regulation efficiency and severe water snatching. Medium voltage drive technology is an energy-saving and efficient AC speed regulation method. If medium voltage drive are used to transform the electric feed water pump unit, it will greatly improve the speed regulation performance, power-saving efficiency, and significantly enhance the safety and economy of the unit's operation.
Recently, the 11.5MW medium voltage drive for feed water pumps developed by FGI successfully passed the 168-hour continuous operation acceptance! This marks that the equipment has withstood the rigorous tests in key performance aspects such as stability and reliability, adding strong support for efficient and energy-saving solutions in the industrial field.
2.project overview
A certain power plant in Inner Mongolia has put into operation 4*660MW large-scale generating units. The transformation of high-pressure and high-power electric feedwater pumps in this power plant has become another important project of the FGI transformation.
Each unit of this power plant is equipped with 3 electric feedwater pumps, and the capacity of each feedwater pump is 35%. During normal operation, the feedwater pumps are activated according to the load of the unit. At full load, all three feedwater pumps operate simultaneously. This renovation project includes adding high-voltage frequency converters to the feedwater pumps, as well as the construction of the building's infrastructure and power distribution. Before the renovation, the feedwater pumps were speed-regulated through a hydraulic coupling. Based on the actual load rate of the units in the plant, there is a significant potential for energy savings for the feedwater pumps. To reduce the plant's power consumption and save energy, frequency converters were added to the A and C feedwater pumps, while the original hydraulic coupling was not removed. The hydraulic coupling was fully opened during normal operation, and the water flow was controlled by the frequency converter, further reducing the plant's power consumption.
The unit configuration is as follows: The boiler of a single unit is a supercritical primary intermediate reheat, four-corner circular combustion, direct current boiler designed and manufactured by Harbin Boiler Works, with an efficiency of 92.71% under rated working conditions. The steam turbine is a single-stage intermediate reheat, double-cylinder double-exhaust, direct air-cooled, condensing steam turbine designed and manufactured by Harbin Steam Turbine Works. The generator is a QFSN2-660-2 three-phase AC stein-pole synchronous steam turbine generator produced by Harbin Electric Machinery Factory. It adopts water-hydrogen-hydrogen cooling method, with a stator rated voltage of 20kV, a rated current of 21170A and a rated capacity of 733.33MVA.
The system consists of a pre-pump, an electric motor, a hydraulic coupling (including the working oil circuit and lubricating oil circuit parts), and a feed water pump. According to the load changes of the unit, the system adjusts the water supply volume of the feed water pump through the hydraulic coupling to meet the water supply volume requirements of the boiler production system.
3.System transformation plan
Facing complex systems and high-difficulty renovations, FGI conducted detailed on-site investigations. Combining years of rich experience in power plant applications, it had multiple on-site exchanges and technical communications with users. Eventually, it confirmed a renovation solution that was in line with the actual situation on site. At the same time, it provided full technical support throughout the process and stayed at the user's site to complete the entire system frequency conversion renovation.
The existing hydraulic couplings in the power plant do not need to be removed. All the functions of the existing hydraulic couplings are retained. The position of the hydraulic coupling's spoon tube is fixed at the maximum opening degree, and the speed of the feed water pump is regulated by the high-voltage frequency converter configured for the motor.
The working oil pump and auxiliary oil pump of the hydraulic coupling remain unchanged. A backup oil pump is added and connected in parallel to the existing auxiliary oil pump. It is matched with a motor with the same power as the existing auxiliary oil pump motor. One auxiliary oil pump is in use and the other is on standby. They start and stop according to the original logical judgment conditions and achieve interlocking between the new and old pumps.
4.Reforestation effect
Each unit's feedwater pump operates for approximately 7,500 hours throughout the year. The current and operating time of the feedwater pump under various load conditions of the unit were recorded. The energy consumption of the A and C electric feedwater pumps before and after the frequency conversion transformation was compared. The annual power consumption at the power frequency was about 130 million kWh, while the annual power consumption after the transformation was 112 million kWh. The total power saved was approximately 17 million kWh, with a power-saving rate of over 13%. The annual cost savings from the feedwater pump frequency converter was about 7 million yuan. After the frequency conversion transformation of the feedwater pump, the energy-saving effect was obvious, and the speed regulation performance was excellent, bringing significant economic benefits to the power plant and receiving unanimous praise from users.
A large number of tests were conducted on the on-site control and reliability aspects. It was ultimately proven that the system could still maintain the original standby mode after the transformation and did not affect the reliability of the feedwater system. No potential risks caused by the transformation were triggered, and the project was successfully completed.
5.Sum up
performance in the frequency conversion transformation of power plant feed water pumps and enriched its project experience. The remarkable energy-saving effect, stable and reliable product performance, and perfect solution are the driving forces behind the successful implementation of the transformation, providing a new power-saving approach for domestic power enterprises to save energy and reduce consumption. The user highly praised FGI's comprehensive capabilities in air-cooled medium voltage drive and engineering system renovations, once again confirming FGI's strong technical strength as a leading domestic frequency conversion enterprise.
