Application of the hottest domestic high voltage i

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Application of domestic high-voltage inverter in circulating water pump of power plant × For 300MW units, each unit is equipped with two circulating water pumps, and the outlet throttle uses butterfly valve, which is only fully open and fully closed. Luuk groenewoud added: "however, the high cost of carbon fiber composite materials makes the large-scale production of automobiles daunting." the adjustment is controlled by the number of pumps on. Due to the temperature difference between seasons and day and night, the flow of one pump is often insufficient, and the flow of two pumps is too large, Due to this original regulation method, the vacuum degree of the steam turbine is unstable, which can not ensure that the steam turbine operates under the economic operation mode. At the same time, a large amount of electric energy and water resources are wasted, resulting in high auxiliary power consumption rate, high standard coal consumption for power supply, and difficult to reduce the power generation cost. It is urgent to select the appropriate speed regulation mode for energy-saving transformation of circulating water pump. In order to further adapt to the power system of separation of power plants and bidding, save energy, reduce the auxiliary power consumption rate, protect the environment, simplify the operation mode and reduce the wear of rotating equipment, our company decided to adopt a set of 6 kv/1800 kW high-voltage frequency converter speed regulating device produced by Beijing Lidehuafu Electric Technology Co., Ltd. on the circulating water pump of 1

1. Working condition characteristics of circulating water pump

the generator set of Shanxi sunshine power generation company adopts closed circulating water system. The make-up water source of the power plant is Niangziguan Spring water, the softened water treated by the chemical weak acid cation exchanger, and the circulating water pump adopts the unit water supply system, that is, each unit is equipped with a cooling tower, a pressure circulating water pipe, a double hole artesian ditch and two circulating water pumps. Under normal operating conditions, each unit operates two circulating water pumps. The cooling water tower adopts the air duct type countercurrent natural ventilation cooling tower, and the air duct is a hyperbolic rotating shell. In the circulating water supply system, the circulating water pump is used to realize the recycling of water resources. The hot water after heat exchange enters the cooling facilities for cooling to reduce its water temperature to the allowable value, and then repeatedly inputs the cooling water into the condenser for recycling. Since the system water level is basically stable, the lift of the circulating water pump is basically stable, and its capacity is determined according to the calculated water volume

the circulating water pump operates continuously for a long period of time at random. As the unit load changes frequently, it is necessary to adjust the circulating water flow in time to ensure the safe and economic operation of the unit. Even under the same load, different external environment also makes the demand for circulating water flow different. According to the current situation of the power plant, the situation that one set of water is less and two sets of water are more exists for a long time, and the outlet valve is not adjustable. During the whole day in winter, the night after spring and low load working conditions of the unit, one circulating water pump can meet the operation needs. The average operation time of the circulating water pump is calculated as 200 days, Operation time of two circulating water pumps: 150 days. When the circulating water pump works at full load, its motor working current is 195a

it is necessary to adopt frequency conversion regulating device to regulate flow according to working conditions. The high-voltage frequency converter is used to adjust the speed of the motor driven by the circulating water pump according to the actual needs. Due to the inherent characteristics of the water pump, the speed regulation can not only adjust the water output of the water pump, but also reduce the power consumption of the motor, and achieve the most favorable vacuum control purpose, so as to achieve the purpose and effect of not only ensuring and improving the process, but also saving energy and reducing consumption

2. Economical operation mode of steam turbine and control of circulating water pump flow

at present, the vacuum degree of steam turbine is mainly controlled by regulating the cooling water flow. According to the operation principle of steam turbine, the condenser pressure during operation mainly depends on the steam load, cooling water inlet temperature and cooling water volume, and the cooling water temperature generally depends on natural conditions, When the steam load is certain, the vacuum degree of the condenser can only be improved by increasing the flow of cooling water. In order to improve the economy of unit operation, increase the increment of turbine power due to vacuum degree ΔΝ 1 should be greater than the power consumed to increase the circulating water volume ΔΝ 2. Obviously, the most favorable vacuum Peco (economic vacuum) of the turbine should be located at the net power increase ΔΝ=ΔΝ 2 - ΔΝ At the maximum value of 1, at this time, the steam turbine works in the economic operation mode, as shown in Figure 1:

in the figure, DW is the cooling water volume, P is the condenser vacuum of the steam turbine, ΔΝ Is the power difference, ΔΝ When the cooling water volume is relatively small, it increases with the increase of cooling water volume and reaches the maximum at point A. if the cooling water flow is further increased, ΔΝ Instead, it starts to decrease until it reaches zero. However, when point C is reached, the expansion capacity of the steam turbine has reached the limit, the steam turbine power will not increase, and the vacuum corresponding to point C becomes the limit vacuum. From the figure, it can be seen that the vacuum degree Peco corresponding to point B where the isowater flow line from point a intersects with the condenser pressure line is the most favorable vacuum, and the cooling water amount Deco corresponding to point a is the best cooling water amount. By determining the most favorable vacuum of the steam turbine, the cooling water flow is controlled based on this, so that the exhaust pressure of the steam turbine can maintain the most favorable vacuum position as far as possible, so as to ensure that the unit operates under the economic operation mode

it can be seen from the above analysis that changing the circulating water flow can improve the economy of unit operation

3. Control principle of circulating pump with the most favorable vacuum degree of steam turbine

the most favorable vacuum is realized by adjusting the flow of circulating cooling water, controlling the operation state of circulating water pump by unit DCS, adjusting the number and speed of circulating water pump, and controlling the flow of circulating water to maintain the vacuum degree of steam turbine at the most favorable vacuum position, so as to ensure the economic operation of mechanical and plastic processing industry after the ultra-high growth of "1015" with an average of 20.1%. The speed regulation and control of the water pump is the core content of the most favorable vacuum control system of the steam turbine. The frequency converter is used to control the speed of the circulating water pump, and the control mode is "one change, one certainty"

4. Principle of harsvert-a06/220 high voltage variable frequency device

the variable frequency device adopts multi-level series technology. See Figure 2 for 6kV system structure, which is composed of phase-shifting transformer, power unit and controller. 6kV series has 15 power units, each of which is connected in series to form a phase

2 The unit structure with load phenomenon rate and electrical performance are completely consistent and interchangeable. Its circuit structure is shown in Figure 3. It is a basic AC-DC-AC single-phase inverter circuit. The rectifier side is a diode three-phase full bridge. Through sinusoidal PWM control of IGBT inverter bridge, it can

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