Control Technology of AC Excitation Speed Regulation of Pumping Station Motor

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Control Technology of AC Excitation Speed Regulation of Pumping Station Motor [Copy link]

In order to reduce flood disasters, my country has built many electric drainage and irrigation stations in the basins of major rivers. Generally, electric drainage and irrigation stations are designed with fixed lift. During floods, when the water level of the outer river exceeds the designed lift, the pump station is forced to shut down, so that the water in the inner river cannot be discharged in time, causing serious losses to the country and people's property. If the motor can be made to run super synchronously at this time, such as increasing the speed by 5%, the pump lift can be increased by about 10%, which can largely solve the problem of the pump being forced to shut down due to the high water level of the outer river and reduce the losses caused by inland river floods. Therefore, realizing the super synchronous operation of such motors has great social and economic benefits.

Since the supply voltage on the stator side of the pump motor is high voltage, when variable frequency speed regulation is used on the stator side, the speed regulation equipment is expensive, and the speed increase is limited by the supply voltage. If double-fed speed regulation is used, the capacity of the variable frequency equipment is much smaller than that on the stator side, because the pump requires a limited speed regulation range (only ±10%), which is economically cost-effective. Another important advantage of using double-fed speed regulation is that the reactive power absorbed from the power grid can be adjusted by adjusting the magnitude and phase of the excitation current, that is, the power factor of the motor can be adjusted, and it can also run in leading phase. Since there are a large number of units in this type of pump station, the use of this technology will play an important role in saving electricity and improving the power factor of the local power grid.

The rotor inverter of the AC excitation doubly fed speed regulating motor can be either an AC/AC inverter or an AC/AC inverter. Since the performance of the AC/AC inverter is better than that of the AC/AC inverter when running at low frequency, it is very suitable to use AC/AC inverter for the doubly fed speed regulation of pump station motors [1][2][3]. This paper introduces the design of a speed regulation system using three-phase zero-type AC/AC inverter, a 16-bit single-chip microcomputer as the control core, and a field programmable chip as the memory and logic circuit. It proposes a method for calculating the given values of the rotor current amplitude, phase, etc. when the speed is feedback-regulated with the desired power factor as the parameter, and gives the system's hardware and software design.