Research On Suppression Method Of Power Fluctuation In Power System Under Pulsating Load

With the rapid development of military and civilian high-power power electronic loads,such as high-speed railways,electroplating welding,radar devices and high-performance microprocessors.They all show more and more significant load mutation characteristics,which pose severe challenges to the working mode and power quality of the power supply.Therefore,it is of great theoretical significance and engineering application value to suppress system power fluctuations and improve the power quality of power supply under pulsating load,and achieve a reasonable match between power supply and load.In this paper,the method of suppressing the power fluctuation on the input side of the power system and improving the power quality are studied in depth under the condition of pulsating load.First,the mathematical and simulation model of pulsating load is established.Based on the traditional system structure of uncontrolled rectifier-DC/DC converter-pulsating load,the influence of key parameters such as pulsating load period and duty cycle on the power supply system is analyzed.On this basis,the mechanism of the AC input side power fluctuation and the harmonic distortion characteristics of pulsating load current are analyzed.The method of suppressing the power fluctuation of the input side in the traditional system is studied.Three-phase PWM rectifier has the advantages of unit power factor operation and low current harmonic content.Therefore,PWM rectifier is used to replace the uncontrolled rectifier in the original system.Add a large-capacity energy storage capacitor on the output side of the rectifier to decouple the load power from the input power.Then,for the improved system structure,a power-current double-closed-loop control method based on bus voltage monitoring is designed to suppress power fluctuations.The accuracy of the phase-locked loop is very important to the control effect of the system.In order to improve the anti-interference performance of the controller,a digital phase-locked loop with a repeating internal model structure is used to improve the accuracy of the phase-locked angle and output frequency.Based on the idea of average power,a double-loop control method for power current with the purpose of controlling input power is designed.The control method mainly includes working condition detection and judgment,bus voltage adjustment,power current inner and outer loop controllers,input instantaneous power calculation,etc.,which can achieve accurate control of input power and suppress input power fluctuations.In addition,the power system under pulsating load has large power mutation.In order to verify the feasibility of the suppression method,a large signal model was established for the system.Based on the energy potential function theory,the stability boundary of the system is solved,and the stability analysis is carried out.Finally,in order to verify the effectiveness of the designed method,a system simulation model was built in PLECS,and simulation experiments were conducted for six common operating conditions and switching between any two operating conditions.In order to further simulate the operation of the actual digital control system,the controller is designed with the root locus method in the discrete domain,the control system is discretized,and the power fluctuation and current harmonic content before and after the discretization are compared and analyzed to verify the method.Effectiveness.