Discussion On Improving Input Reliability Of Power Plant Start-up And Cooling Standby

Starting-up transformer of power plant can supply reliable power to auxiliary power system in case of failure,which is the key to safe operation and safe shutdown of generating units.For a long time,no-load hot standby operation mode has been adopted in power plant startup transformer.The no-load loss of the startup transformer is considered to be the necessary cost to ensure safe production.With the demand of energy saving and emission reduction and the improvement of automation technology of equipment products,it is possible to change from hot standby to cold standby.Start-up transformer from hot standby to cold standby can reduce the no-load loss of transformer and the auxiliary power consumption rate.It is a new energy-saving operation mode.In this paper,two difficult problems faced by the power plant startup transformer after the operation from hot standby to cold standby are studied:excitation inrush current and quick switching of auxiliary power.On the basis of the auxiliary power system of Feixian Power Plant,the inrush suppression method based on controlling remanence and polarity of bias direction is proposed in this paper.On the other hand, the EMTDC simulation model of induction motor group in Feixian Power Plant is established according to the dynamic response characteristics of motor load in the process of auxiliary power supply switching.The influence of motor parameters and channel number on rapid auxiliary power supply switching is studied,and the method of adjusting trigger angle is proposed to realize different power plant loads.The soft input of the motor can improve the success rate of switching power.The following conclusions are drawn:1)Based on the principle of magnetic bias and remanence interacting,the inrush suppression controller is added to the original control system,and the circuit breaker is merged into the power grid with the smallest impulse current,which effectively suppresses the impulse current.2)The influence of load parameters of induction motor on small disturbance stability is analyzed.Stator resistance,excitation reactance,inertia time constant,load parameters KL,beta and m have relatively small influence on small disturbance stability;stator leakage reactance,rotorresistance and rotor leakage reactance have relatively large influence on small disturbance stability.3)Trigger angle sequence alpha 0 and alpha 1 are the keys to realize soft input.The soft input of auxiliary motor under different loads can be realized by completing the revised control sequence within 5 cycles,which reduces the impact current of the system.