Condensate pump frequency conversion decoupling control system and method for coal-fired power plant

Abstract

The invention discloses an energy-saving type condensate pump frequency conversion decoupling control system for a coal-fired power plant. The system comprises a condenser, a condensate variable frequency pump, a deaerator, a boiler, deaerator water level main and auxiliary adjusting valves, a pressure transmitter, a water level transmitter, a flow transmitter and a DCS control device. The DCS control device comprises a wiring terminal board, a connecting cable, an analog quantity clamping piece, a channel backboard and a main controller. The main controller comprises a logic module used for carrying out logic operation on received signals. The invention further discloses a condensate pump frequency conversion decoupling control method based on the system. Mutual coupling between control loops of a condensate system is effectively eliminated, whole-course cooperative control over the water level of a deaerator and the pressure of a condensate mother pipe is achieved, the disturbance resistance and the interference resistance of automatic control of the condensate system are enhanced, the throttling loss and the station service power consumption rate of the system are greatly reduced, and the optimal control performance and the optimal energy-saving effect are achieved.

Description

technical field [0001] The invention relates to a frequency conversion decoupling control system for a condensate pump in a coal-fired power plant, and also relates to a frequency conversion decoupling control method for a condensate pump in a coal-fired power plant based on the system. Background technique [0002] The condensate system of coal-fired power plant is the main auxiliary system of the power plant, which is used to transport the condensate in the hot well of the condenser to the deaerator, and at the same time provide desuperheating water, sealing water, cooling water, etc. to related equipment. Under the traditional frequency conversion control strategy of the condensate pump, due to the strong coupling between the water level adjustment of the deaerator and the pressure adjustment of the condensate jellyfish tube, there are still the following problems that lead to poor energy saving or economic benefits of the condensate water system: [0003] 1. The throttli...

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Problems solved by technology

Under the traditional frequency conversion control strategy of the condensate pump, due to the strong coupling between the water level adjustment of the deaerator and the pressure adjustment of the condensate jellyfish tube, there are still the following problems that lead to poor energy saving or economic benefits of the condensate water system:

[0003] 1. The throttling loss is large. During the normal operation stage of the unit (especially when the load is high), the water level of the deaerator is completely controlled by the coordinated adjustment of the main and auxiliary regulating valves. This control method cannot guarantee the water level of the deaerator during the adjustment process. The water level regulating valve of the deaerator is fully opened, resulting in a large amount of throttling loss

[0004] 2. The efficiency of the unit is low. The pressure of the condensate jellyfish tube is completely adjusted by the constant pressure of the condensate pump frequency converter. This control method is in the process of changing the load of the unit. The condensate pressure is completely manually set and cannot be automatically tracked and adjusted throughout the process, resulting in a decrease in unit efficiency.

[0005] 3. The control stability is poor. In the high-load stage, there is a strong coupling effect between the two control loops of the deaerator water level adjustment and the condensate jellyfish pipe pressure adjustment. The main performance is that the deaerator water level rises when the condensate pump inverter command increases. At the same time, the pressure of the condensate jellyfish tube also increases; in order to maintain the pressure of the condensate jellyfish tube, the regulating valve is opened, which in turn causes the water level of the deaerator to continue to rise, thereby causing the condensate pump inverter command to decrease

The water level control loop of the deaerator and the pressure control loop of the condensate jellyfish tube are two-variable strong-coupling control systems. The two control loops are cross-coupled and interact with each other, which reduces the anti-disturbance and anti-interference ability of the automatic control of the condensate pump. The control system The reliability and stability of the

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