As a part of the nuclear power feed water system, the normal operation of the feed water pump speed control system is of great significance to the safe operation of the entire nuclear power plant.
The excellent speed controller of the cooling feed water pump in the nuclear power plant is of great significance to the normal operation and reliable work of the system. On the basis of simplifying the model of the nuclear power feed water cooling system, the dynamic principle model of the system is established, thermostatic element and the PI controller of the feed water pump is designed according to the characteristics of the system, and the simulation analysis is carried out to verify the effectiveness of the designed controller.
Feed pump speed control system as a part of the nuclear power feed water system, its normal operation is of great significance to the safe operation of the entire nuclear power plant. The speed control system of feedwater pump, evaporator level control system and pressure control system cooperate with each other to form the Main Feedwater System of the secondary loop of nuclear power plant. Its main task is to maintain the constant pressure of the feedwater jellyfish. Frequency conversion speed regulation technology is the most widely used and the most promising technology in the control method of water supply system. Many domestic scholars have devoted themselves to the study of the application of constant pressure and variable flow feedwater pumps in feedwater pumping stations, and have achieved some results.
At present, the merits and demerits of several speed regulation modes, such as motor speed regulation, hydraulic coupling speed regulation, small steam turbine speed regulation, are generally discussed, and the application of the new control mode of feed water pump in nuclear power plant is not really studied.
With the further construction of nuclear power system, excellent speed controller of cooling feed pump in nuclear power plant has good practical significance and application prospects.
The simplified block diagram of the nuclear power feed water cooling system model is shown in Figure 1. The following assumptions are made in the process of water supply system modeling.
Neglect the change of the diameter and height difference between the inlet and outlet of the pump. It is assumed that the liquid in the pump is a viscous, negligible and incompressible ideal fluid. It is assumed that the front pump, the feed pump and the feed valve of the feed pump are on the same horizontal line.
In order to ensure the stability of the pressure difference of the feed water loop, the pressure difference of the control feed water loop is set at (0.4-1.5) 0.1 MPa. The PI controller is used in the feed water pressure differential circuit, in which KP = 100 and KI = 17. Fig.
3 (a), (b) are the response curves of feed water pressure difference and flow rate when the given feed water differential pressure is 1.5 MPa.
Adding differential pressure disturbance at 500 s and 1 200 s respectively to simulate the change of cooling load. The curves of feed water differential pressure and feed water flow are shown in Fig.
3 (a), (b).
The pressure difference at 500 s increases and the cooling load increases; the pressure difference at 1 200 s decreases and the cooling load decreases. According to the experimental results, it can be seen that the PI controller designed can achieve the given follow-up well under the given cooling load.