| In the modern sterilization industry,the application of bipolar high-voltage pulsed power supply(HVPPS)in the sterilization field has a better effect.Under the premise of killing a large number of bacteria,the bipolar HVPPS can ensure that the nutrients,pigments and taste of food will not change.The bipolar HVPPS currently existing in the market is divided into indirect and continuous modes: the indirect sterilization is not suitable for large-scale applications;the continuous sterilization can only treat a single bacteria.Therefore,it is very important to develop a bipolar HVPPS which can work continuously and can kill many kinds of bacteria simultaneously.At first,the mechanism of high-voltage pulsed electric field sterilization was discussed,the survival rate of bacteria in the liquid to be treated under different electric field strengths was studied,and the influence of the parameter frequency and voltage amplitude of the high-voltage pulse waveform on the effect of bacteria inactivation was studied.A bipolar high-voltage pulse sterilization system which is mainly composed of the load end and the power supply end was established.By analyzing the structure of multiple processing chambers such as the flat electrode processing chamber,the needle plate electrode processing chamber,and the coaxial electrode processing chamber,the coaxial electrode processing with a spacing of 3mm was selected as the load end,and the circuit model of the load end was established.Since the better voltage amplitudes for inactivation of penicillium,yeast,and E.coli are 3.75 k V,6k V,and 9k V,respectively,a modular sterilization structure was adopted in the power supply,and a bipolar HVPPS which can kill 3 kinds of bacteria simultaneously was established.The operation process of the single-module power supply and the three-module power supply,the respective output waveforms,and the parameter calculations were analyzed in turn.The results show that the amplitudes of the bipolar square waves that the two output to the load end are different,but the frequency and pulse width are the same.Studies have shown that when the frequency is 100～1000Hz,the high-voltage pulsed sterilization system has the highest working efficiency,and most bacterial species are easily inactivated.The sequence of each module switch was controled,the action time of each switch was set reasonably,and the charging and discharging process of each module were completed in turn to realize the function of adjustable frequency.The operation process of the power supply at the boundary frequency of 100 Hz,1000Hz and the intermediate frequency(500Hz)were studied,and the parameters were calculated.It can be seen through comparative analysis that the voltage amplitude of the power supply output decreases with the increase of the system frequency,but they all meet the sterilization requirements.Hardware design and software design for the operation process of the three-module system.Finally,the system was simulated at the boundary frequency of 100 Hz and 1000 Hz.The simulation results show that when the system is running at 100 Hz,the amplitudes of output voltage are 4.417 k V,6.176 k V and 9.687 k V respectively;when the system is running at 1000 HZ,the amplitudes of output voltage are 4.272 k V,6.082 k V,9.393 k V respectively,so the system can meet the ability to simultaneously eliminate multiple bacteria when the frequency is adjusted from 100 to 1000 Hz.The number of modules of the HVPPS is determined by the number of sterilized species.The timing parameters of the switches of different modules are controlled to enhance the cooperation between the different modules,thereby realizing a multi-module sterilization system that outputs ideal high-voltage pulsed waveform parameters such as pulse width,amplitude,frequency,etc.,and finally the multi-module sterilization system will have the ability to kill many kinds of bacteria at the same time. |
