Application of the hottest high voltage frequency

Application of high-voltage frequency converter in #1 feed water pump of Guangzhou Mingzhu C plant

Abstract: This paper introduces the technical and economic analysis of the application of high-voltage frequency converter system in the boiler feed water pump of generator set in Guangzhou Mingzhu C plant. It is pointed out that the application of high voltage variable frequency speed regulation in fans and pumps of power plants has obvious social and economic benefits

key words: high voltage inverter; Energy saving; The application of high voltage inverter in boiler water feeding pump in Power Plant C of Guangzhou Mingzhu Liang Yiwei, Jiang Guosheng, Li Gengsheng (Guangzhou Mingzhu Power Plant Company Ltd., Guangzhou, Guangdong 510730, China) abstract:this paper describes the technology and economic analysis of the application to achieve complete energy saving application of high voltage inverter in the boiler water feeding pump in Mingzhu power plant The result shows that the application of High-Voltage Inverter in blowers and pumps in power plants has very obvious social benefit and economic benefits.

1 brief introduction to the working conditions of the unit water supply system of Guangzhou Mingzhu Power Plant C

the power plant C of Guangzhou Mingzhu power (Group) Co., Ltd. currently has #5, #6 two 51.2mw fuel oil units and #7 a 36mw steam turbine unit# 5. The waste heat of #6 two gas turbines is provided to #1 and #2 boilers respectively to drive 7 steam turbine generator# The feed water of 1 and 2 steam drums of 1 and 2 boilers is supplied by the main pipe of three feed pumps 1, 2 and 3

the parameters of the three water supply pumps are the same. The water pump is dgx9 produced by Shenyang water pump factory, with a rated speed of 2980rpm and an efficiency of 82%. The water supply of 80m3/h is transformed into 120m3/h, and the head is 1080m. Three 6kV motors, Y-type motors, with rated parameters of 500kW, 6kv/57.2a, cos=0.87, rotating speed of 2972rpm, class F insulation, winding Y connection, were used to drive the feed pump. They were produced by Nanyang explosion-proof motor factory in August 1998

Figure 1 shows the schematic diagram of the feed water pump circuit of 7 steam turbine generator in Mingzhu C plant. The initial design idea of this design is "two working and one standby". When any one fails, the standby motor will be started immediately to ensure the normal operation of the unit. There are three valves from the feed main pipe to the two boiler drums to control the feed water flow, namely, the main circuit, the middle circuit and the bypass. The maximum flow of the main circuit is 100% of the regulating valve, the maximum flow of the middle circuit regulating valve is about 70%, and the flow of the bypass electric valve is about 50%

but after the technical transformation of the pump blades and even causing the feeder to stop running, the current actual operation

Figure 1 Mingzhu C plant boiler feed water circuit diagram

the operating condition is: under the current load, the water output of one pump is enough for the operation of two boilers. In the operation of two gas turbines, #1 and #2 two steam drums supply steam (two driving and one working condition), the total load is 67mv. For the detailed operation of the experimental machine, we have specified relevant detailed regulations about a, The drum pressure is about 6.4Mpa, the rated evaporation capacity is 64t/h, and the 1 pump is operated. At this time, the motor current is about 51a, the power factor is 0.86, the actual water supply is about 125t/h, and the outlet pressure of the pump head is about 8.3~8.9mpa. According to the performance curve of the pump, the pump has reached the limit at this time, and the pump efficiency is low under this operation condition. If the load further increases, the second pump must be started. When the load is low in the valley period, only one gas turbine is operated, and one steam drum is used for steam supply (one driven by one working condition). The pressure of the steam drum is about 3.5Mpa. At this time, keep running 2 pump. The motor current is about 41a, the motor power factor is 0.85, the outlet pressure of the pump head is about 9.2~9.8mpa, and the actual water supply is about 63t/h

2 operation of No. 1 feed pump of Guangzhou Pearl C plant before transformation

2.1 system operation data of feed pump before transformation

Table 1 system operation data of boiler feed pump of Pearl C plant before frequency conversion transformation

working condition one by one by two

feed water pressure (MPA) 9.0~9.6 7.9~8.7

drum pressure (MPA) 3.4 6.4

feed water flow (t/h) 63 125

motor current (a) 39~41 50~52

motor active power (kw) 360 is widely used in low-temperature physical and chemical experiments in petrochemical, metallurgy, boiler pressure vessels, steel, steel pipes, 5 gold, casting, pumps, valves, fasteners, vehicles and ships, machinery manufacturing, aerospace and scientific research industries 460

Draw equal efficiency curves of two driving one working condition and one driving one working condition on the performance curve of water pumps. For example, draw the pipe characteristic curve of one drag for one time, as shown in curve 2 in Figure 2 (this curve corresponds to when the backflow circulating valve opening is certain), and the pipe characteristic curve of two drag for one time, as shown in curve 2 in Figure 3 (this curve corresponds to when the backflow circulating valve opening is fully open); Curve 1 in both figures is the H-Q characteristic curve of pump power frequency operation

Figure 2 power frequency one drive one water supply Q-H curve and pipe characteristic curve

before frequency conversion transformation, the operating condition point in peak period is point a in Figure 3, and the valley period is point B in Figure 2. According to the above data, we can draw the following conclusions:

A. when one pump is running, the water supply volume of the pump is about 120m3/h. From the performance curve of the pump, it can be seen that the efficiency of the pump is low at this point, which is 53%, while the best efficiency point of the pump is 62% (the corresponding rated flow is 80m3/h)

b. During the day, the motor consumes a total power of 1.732*6000*51=530kva, of which the active power is 530*0.86=455.8kw. Under this operation condition, the motor has basically run at full load, But the reactive current of the motor is [512- (51*0.86) 2 0.5=26A。

Figure 3 power frequency two pull one water supply Q-H curve and pipe characteristic curve

c, peak period one pull one time, the total power consumption of the motor is 1.732*6000*41=426kva, of which the active power is 426*0.85=360kw

d. During Valley operation, when the water pressure is 9.8MPa, the water supply of the water pump is 105m3/h, the water supply of the boiler is 633/h, and the reflux of the reflux circulating valve is 42m3/h. There is a lot of energy-saving space

2.2 Guangzhou Mingzhu C plant 1 feed water pump frequency conversion transformation scheme

2.2.1 design requirements and objectives

a) provide the frequency conversion system with two boiler drum independent drum water level feedback signals, 4~20ma signals, as the control target, to achieve automatic control

c) the control system after frequency conversion transformation is independent of the existing DCS system, and this system has independent