Research Of Switching Methods On Seamless Power Supply For Important Loads

With the rapid development of industrial technology, the important loads,which are mainly represented by petrochemicals, iron and steel enterprises, now have been put forward higher requirements on reliability of power supply.The power supply mode with a dual-power switching course is mainly utilized to ensure an uninterrupted power supply of this type of load by far,therefore,the power supply automatic transforming switch equipment has been widely used, which is mainly including a bus-bar automatic transfer switch equipment and a high-speed bus transfer device.The high-speed bus transfer device is based onthe bus-bar automatic transfer switch equipment,which has a better performance and a tendency to gradually substitute for the bus-bar automatic transfer switch equipment.However,the start signal for high-speed bus transfer deviceis an external signal,its start-up time is constrained by external environment, and it maybecannot start immediately as the main power failure occurs.In addition, the switching time of the high-speed bus transfer device is affected by the residual voltage during the break period and the phase difference of the backup power,the switching time will continue on a long term as it has a large phase difference, hence it can not meet the requirement of seamless power supply for the important loads.To meet the requirements of seamless power supply for the important loads,and in view of the insufficiency power automatic switch device,in this paper, a further research is then carried on,whose main content can summarize below:(1) Replace the conventional mechanical switch with the solid state transfer switch, in order to shorten the duration time of the power switching process.The zero switching control mode is adopted to build a simulation model for the solid-state switch in Simulink,and the RLC loads in the form of series and parallel are taken as examples.Empirical results show that the switch time is within 10 ms under the zero switching control mode, compared to the conventional mechanical switch,its switch time decreases greatly.(2) On the basis of the ideal asynchronous motor space vector model,and according to the inside nature of flux conservation principle of the motor, the analytical expression of the residual voltage of the motor during the break period is given which shows the variation of the residual voltage.The direct running process of the residual voltage during the break period and the backup power supply is simulated in Simulink IDE, consequently the adverse impacts of the residual voltage and the phase difference of the backup power supply on the power switch course can be revealed. The simulation for the performance of the high-speed bus transfer device is then implemented in Simulink, which shows the existing advantages and shortcomings of the high-speed bus transfer device.(3) The optimal matching strategy which is based on the phase sequence transformation for the backup power phase is proposed. The basic principle and mode of connection of the proposed strategy is described, and simulation for validation is then implemented. The results show that the proposed strategy can reduce the switching impact significantly.(4) In this paper, a seamless switching power supply method which is based on DVR is proposed.The principle and the process of the proposed method is described in detail with the related model built in Simulink,and a large number of simulations for validation is then implemented.The results show that the proposed method can not only achieve the quickness of the power switching course, but also can reduce the impact caused by the power switching course, and it still can be used to cope with the grid voltage dips issues.(5) In this paper, a seamless switching power supply method which is based on TCPST grading adjustment strategy is proposed.The principle and implementation of this proposed method is described in detail with the related model built in Simulink,and a large number of simulations for validation is then implemented.The results show that the proposed method can not only achieve the quickness of the power switching course, but also can reduce the impact caused by the power switching course.Compared with the existing methods,the switching efficiency is significantly improved which has a good application prospect.