Research On Influence And Coordinated Optimization Of Changjiang Nuclear Power Plant Accessing To Hainan Power System

Hainan power grid,which covers the entire island,is responsible for the power supply of Hainan province.Due to its unique geographical location,Hainan power grid is a typical island power grid.The relatively weak power grid structure of Hainan power grid,the inner power supply structure of the grid along with the imbalance of power supply and load distribution make Hainan power grid have the following characteristics:(1)It is weakly connected with the main gird,and easy to form an isolated power grid;(2)The single generator capacity takes a large proportion of the power grid capacity,which makes it carry obvious "large capacity generator within a small power system" characteristics,and the unit failure could have great influence to the system;(3)The power supply and the load are distributed in an unbalanced way,with the power supply on the west side and the load mainly on the north and south sides.The power flow in the gird goes mainly from the west to the north,from the west to the south;(4)The power supply and its backup are insufficient,and the power grid has been relying on the contact line as the emergency standby for a long time;(5)Frequent natural disasters lead to large probability of power grid failures,especially multiple failures are easy to happen.In order to alleviate the power supply tension of Hainan power grid,the Changjiang nuclear power plant was built in Changjiang county,Hainan province.The 2x650 MW nuclear power unit,installed in the first phase of the project,is connected to Hainan power grid at a voltage level of220 k VChangjiang.nuclear power unit has the characteristics of large capacity and requires high safety.Meanwhile,Hainan power grid has small capacity and is weakly connected with the China southern power grid,unreasonably distributed.It should also be taken into consideration that the Qiongzhong pump-storage power station,which is compatible with the nuclear power unit,and the Fugang line 2,which strengthens the connection between the Hainan power grid and the main gird,cannot be put into operation as planned.All these factors will bring a series of problems that will affect the safe and stable operation of Hainan power grid.This paper mainly studies the influence of Changjiang nuclear power accesses on the operation of Hainan power grid,including:(1)The influence of nuclear power on the operation mode to the Fugang line: Since the start of Changjiang nuclear power plant's operation,the capacity of single unit of Hainan power grid will greatly increase,and the power fluctuation of the Fugang line caused by the failure of the unit has also largely increased,making the operation restrictions of the Fugang line more severe.The Fugang line is the only channel between Hainan power grid and the China southern power grid,therefore it shall be quite beneficial to both improving the power shortage situation of Hainan power grid and reducing the pressure of peak load regulation,as well as increasing its flexibility,by taking the measure of properly relaxing the restrictions on the exchange of power flow on the Fugang line.(2)The influence of nuclear power on the stability of frequency stability on Hainan power grid:The single unit capacity of Changjiang nuclear power unit is large,and the loss of nuclear power unit under the condition of isolated network will have a great impact on the frequency stability of Hainan power grid.In order to solve the low frequency problem caused by the loss of the nuclear power unit in the state of isolated network,measures can be taken to limit the power output of the nuclear power unit after or before the failure.(3)Coordination optimization on the third line of defense in Hainan power grid after the nuclear power is put into operation: The paper optimizes the load cutting measures of the second line of defense and the low frequency load reduction measures of the third line of defense in order to minimize the load cutting.It is recommended to adopt the strategy of "stable control and concentration" of the second defense line,that is,after power loss,the initiative load cutting measures of the second defense line should be taken as the main measure.In this way,the optimal cutting load can be guaranteed under uncertain boundary conditions(load and primary frequency modulation level).It can also guarantee the loss of one maximum capacity unit(350MW)at the time of isolated network without causing power safety accidents.Through a series of simulation calculation and analysis studies,the adaptability of the third defense line of the power grid after the nuclear power connected is clarified.It provides effective support for the safe and stable operation of Hainan power grid and nuclear power units,and is of great significance to arrange the operation mode of power grid.