Application of HV frequency converter in condensate pump of power plant

Application of HV frequency converter in condensate pump of power plant

In some power plants, two sets of multistage centrifugal condensate pumps with 100% capacity are used respectively. 

The original design operation mode of condensate system is that two constant-speed condensate pumps with 100% capacity are mutually standby, that is, driven by a constant-speed motor, one in operation and one in standby. The flow of condensate is regulated by the feedwater regulating valve of deaerator, and equipped with a bypass to ensure safe operation of the condensate pumps under various operating conditions. Under normal operation, one condensate pump is in operation and one is in standby. When the running condensate pump fails, the other one is automatically put into operation. When the load changes, the deaerator water level is controlled by the opening of the deaerator water supply regulating door, which causes a large throttling loss. During startup and shutdown and low load, the bypass door has to be opened to maintain the minimum flow rate of the condensate pump, resulting in a waste of energy. In addition, even if the unit is running at full capacity, the water supply damper of deaerator can't be in the fully open position because of the large design margin. With the condensate pump running at a constant speed, the system has some problems, such as low efficiency, high energy consumption, short service life of equipment, large daily maintenance and high maintenance cost.

If the HV frequency converter is used to control the condensate pump motor, the variable load adjustment of deaerator water flow can be realized. The water regulating valve of deaerator can always be fully open, and the bypass valve is always closed, thus avoiding the above-mentioned power loss. In addition, the converter can make the motor realize soft start, avoid power grid impact and mechanical impact caused by direct start of the motor, greatly prolong the life of the motor, reduce pipeline vibration and improve the reliability of the system.