Application Of Low Voltage Ride Through Device On Coal Feeder In Power Plant

The lack of low voltage traversal ability will cause the shock or disassembly of the power the large scale of the grid system will lead to power outages and load reductions and economic impact.Because when the plants caused by lightning strikes,electrical equipment such as short circuit,grounding power plant auxiliary power short-term voltage reduction or interruption,power supply and control of low voltage and short supply interruption,part of the auxiliary inverter will stop running after low voltage blocking action,power plant auxiliary especially coal feeder is controlled by inverter,inverter power supply and control power often taken from the factory with power,When the "low voltage pass through" occurs in the power supply,the frequency converter will lock the output quickly due to the low voltage,without effectively avoiding the transient fault of the system,and can not meet the needs of the stable operation of the power grid.This paper takes into account the frequency converter input power reduction or power loss,the frequency converter detects the dc bus voltage reduction,will trigger the low voltage protection.Combining with the principle and working mode of frequency converter,the problem of low voltage trip of frequency converter can be solved by add low voltage ride through device to keep the dc power supply voltage of frequency converter stable.In this thesis,we study the coal feeder low voltage ride through device,after modification,through simulation experiment,when one of two way power supply power supply disappears,or system power supply voltage instantaneous down to more than 20% of rated voltage,coal feeder inverter will not immediately tripped,guarantee the unit is not affected by the power fluctuation of the coal feeder,and will not or reduce the output of the unit,which ensures the normal operation of unit.The thesis contains 55 figures,11 tables and 52 references.