Method of estimating the efficiency of pumping unit frequency regulation (to be discussed)

Summary

The method of estimating energy saving from using frequency regulation of the pumping unit capacity in water supply systems is presented. The estimation of the capacity efficiency of pumping units is carried out only from the energy saving resulting from the use of frequency regulation instead of throttling (other saving components are not considered). To estimate energy saving it is required to compare the power consumed from the grid in the existing scheme of the regulation by penstock gate throttling and in the frequency regulation scheme. Then the energy saving in monetary form shall be compared with the expenses for retrofitting the frequency regulation system. The method is based on the graphical analysis of the pump operation point parameters in the operating group and optimized for the use in water supply systems operating by the pressure.

Key words

capacity , power saving , frequency regulation , pumping unit , efficiency evaluation , throttling

Control of centrifugal pump parallel operation

Summary

The problems related to the cable capacity of pumping units during their parallel operation (one with variable-frequency control, another one – without variable-frequency control) are considered. In the traditional control schemes (without variable-frequency control) the problem is solved by throttling of each pump with cable capacity levelling of their drive motors. This function is usually carried out by the operator in manual mode. Based on the conducted analysis an algorithm of pump control was developed that provided for their safe operation in the working area and maximum energy efficiency. It is proposed to carry out controlled throttling of the pump without variable-frequency control by controlling the position of the set point of the pump with variable-frequency control at the working area interface. To ensure failure-free operation of the pumping station in case of the pump with variable-frequency control emergency shutdown it is recommended to change the system of the pump without variable-frequency control for automated pressure maintaining with the help of throttling. To implement the given algorithm the use of a special process controller with the sufficient computing power (STK 500 type) and series SP 200 blocks is proposed.

Key words

power saving , frequency regulation , centrifugal pump , parallel operation , throttling