Coordinative Controler Of The Deaerator For Power Plant

Deaerator plays an important role in thermodynamic power plants since it can remove the harmful gas, such as oxygen, from the water before it enters the boiler and erodes the thermodynamic equipments. Deaerator can run in single mode or in parallel mode. The single mode has a simple structure and is easy to operate, but it is hard to adapt to the system's load variation. In practical case, overpressure and overflow can often occur in single mode. In order to overcome these disadvantages, parallel mode is often adopted in that it can cushion and adjust its balance by itself. But because the water chambers and the vapor chambers are connected and affected each other in parallel mode, thus it forms a strong coupling, nonlinear and multi-variable system. The variation of the water level and pressure in one deaerator can influence other deaerators' water level and pressure, therefore, it often results in the system's long time instability, deviation in control precision and ineligibility of the oxygen's quantity in the water which can cause great damage to boilers.Harbin Thermodynamic Power Plant adopts parallel deaerators and real time manual control mode. The purspose of this paper is to employ fuzzy control scheme to realize regulation function among two or more high-pressure deaerators and one low-pressure deaerator. If we only consider the prime factors which affect the deaerator' s water level and pressure, we can simplify individual deaerator' s mathematical model and construct the mathematical model of two high-pressure deaerators and one low-pressure deaerator and simulate on this model. We can prove the validity of parallel deaerator' s control from the results of simulation. Subject to the feature of variation and nonlinear of parallel deaerators, fuzzy control method is adopted to control multi-state variables. The regulation of fuzzy control is based on the state variables of the two high-pressure deaerators and the low-pressureiideaerator.In order to ensure the system' s security and practicability, practical controller for parallel deaertors is designed in this article which take Omron model C500 programmable controller as control kernel and equipped with extending modules. The issues to improve the hardware performance is discussed then, and the improved system is evaluated also.