Research On Pulse Power Supply Of Wastewater Treatment Based On Sliding Mode Control

With the rapid development of economy and technology,the productivity of the industry has been continuously improved,which causes the release of a large amount of wastewater.If it is left untreated,pollutants in the water can seriously affect the environment and even harm human health.Therefore,as an important class of high-power power supplies,the application value of wastewater treatment pulse power sources is very high and has a wide range.Based on this background,this paper will conduct research in-depth on the topology and the control strategy of the wastewater treatment pulse power supply and propose corresponding improvement measures.Due to the large output power of the wastewater treatment power supply,the topology structure of the ZVZCS phase-shifted full bridge is adopted as the main circuit structure for its characteristics.In order to realize the zero voltage turn-on of the switches of the leading leg,the capacitor can be connected in parallel.In order to realize the zero current turn-off of the switches of the lagging leg,the series blocking capacitor and the saturation inductor can be utilized in the primary side.Due to the reverse recovery characteristics of the diode,the secondary bridge rectifier diode will generate a voltage spike when it is turned off.For this characteristic,a double current rectifier circuit will be used on the secondary side of the transformer to achieve zero current shutdown of the diode,which suppresses the voltage spike,and this topology also conforms to the characteristic of the power supply that the full load current is high.At the same time,the influence of the inductor size on the current ripple and the diode ZCS is analyzed to complete the selection of the filter inductor.During normal operation of wastewater treatment pulse power supply,the load needs to be constantly switched between full load and no load.This paper changes the traditional current mode control into the second-order sliding mode control based on PWM for the problem caused by frequent load changing.In order to improve the control effect,this paper improves the sliding mode control law,and obtains the optimal control parameters through the transient analysis of the load changing,which accelerates the dynamic response process and reduces the voltage variation on the output capacitor during load changing.For wastewater treatment pulse power supply,after the load is switched from full load to no load,the over-voltage phenomenon will occur on the output capacitor,which will seriously affect the operation of the circuit and even cause safety hazards.In view of this phenomenon,this paper starts with the Buck circuit and improves the topology of the main circuit by adding auxiliary devices to the main circuit.At the same time,by introducing the AND logic of the load signal in the primary equivalent switch,the new problem brought by the improved topology is totally solved,thereby suppressing the phenomenon of no-load over-voltage and further improving the adaptability of the pre-stage converter to the pulsed load.Finally,this paper designs the sampling,control and drive circuit and writes the experimental program on TMS320F28335,and then builds the experimental platform.Then based on the simulation analysis,the correctness of the above scheme is further verified by experiments.