Hardware Design Of Mid-voltage Variable Frequency Variable Speed System For Electrical Submersible Pump

As electrical submersible pump is widely used for the oil extraction in oil fields, it becomes one of the most important oil extraction methods. But, the drive systems presently equipped for electrical submersible pump are mainly working at industrial frequency, which leads to much disadvantages such as large starting current and serious wasting of power, etc. Based on the sufficient investigation, this paper, using the modern AC speed regulating technology, designs a kind of cells cascaded multi-level inverter to drive the pump, which can solve most of the problems existing in the present application of electrical submersible pump.First, the paper briefly analyzes the present applied status and existing problems of the electrical submersible pump and AC speed regulating technology. Through the comparison of load characteristics in different driving situations of electrical submersible pump system, we give out the suitable solution, which is called cells cascaded multi-level inverter. Then, the theoretical analysis and simulation is carried on, and through the combination of technologies currently used in Mid-voltage inverters, the main circuit topology and controlling circuit structure adopted in this paper are introduced. Based on the above, the practical main circuit and controlling system of the cells cascaded multi-level inverter are designed and implemented. Also, the EMC (Electro-Magnetic Compatibility) and anti-interference ability are fully considered through the whole hardware design progress.The main circuit is formed by several low voltage power cells, which are put in series to output mid-voltage. That is, each phase consists of 3 cells arranged in series, and the whole inverter includes 9 ones. For the real modularization, all the cells are designed to have the same structure. The control circuit includes two parts, the master control board and the slave control board, where the slave boards have their own CPU and all work in the centralized control of the master board's CPU. At last, the paper carries out the experiment with load to confirm the validity of the hardwares. During the experiment we made much adjustments and optimization, and also gave out the prospect on more accurate synchronization methods.It shows, through the experimental validation, that the cells cascaded multi-level inverter described in this paper basically satisfies the demand of electrical submersible pump oil extraction system. It solves the problems when the pump system works at industrial frequency and attains the goal expected.