Research On Low Frequency Pulsed Power Suppression In Three-phase AC-DC Power Supply Systems

In recent years,different kinds of new radars have being widely used in airborne,shipborne and ground equipment systems.The high pulse power of the load make it difficult for the conventional electromechanical equipment to respond in time,resulting in a series of problems such as active power rush,harmonic current,and voltage fluctuation and flicker of the power supply system.In addition,the generator and transmission line need to be designed and configured with the peak power to meet the instantaneous high power demand of the pulsed load,which results in the overcapacity of the generator and increases the volume and weight of the system.In order to achieve the pulse power decoupling to improve the stability,reliability and power quality of the power supply system,and optimize the configuration of the system capacity,this dissertation starts with the existing system based on the uncontrolled diode-bridge rectifier,and studies the system architecture,circuit topology,control method and modulation strategy of the power supply system for the pulsed load.To improve the power quality and stability of the uncontrolled diode-bridge rectifier power system without changing its structure and configuration,a shunt pulse-harmonic multi-functional compensator(MFC)based on the bidirectional AC-DC converter is proposed to realize the power decoupling between the AC power source and the pulsed load.The basic operating principle of the MFC is to provide the instantaneous pulse power of the load together with the AC power source during the pulse on time,and absorb the redundant power of the power source during the pulse off time,as well as compensate the harmonic current and reactive current during the entire pulse period.The control methods,modulation strategies and basical characteristics of the MFC based on typical AC-DC converter systems,including single-stage,two-stage and quasi-single-stage AC-DC topology,are analyzed and compared.Theoretical analysis and experimental results show that the proposed MFC can compensate the low-frequency pulse current,fundamental frequency reactive current and high-frequency harmonic current simultaneously,which greatly improves the power quality and stability of the power supply system.Active rectification is the development direction of the AC-DC power supply systems.To intruduce actvie rectification into the existing system and combine the advantages of active rectifier and uncontrolled diode-bridge rectifier,as well as optimize the configuration of the power capacity and improve the power quality of the power supply system,a power transmission scheme with dual power paths is proposed based on the characteristics of the pulse load,that is,the dynamic power and steady state power of the pulsed load are transmitted through the two different power paths.Based on this scheme,a hybrid rectifier consisting of an uncontrolled diode-bridge rectifier and an active rectifier with parallel connection is further proposed.The active rectifier with a two-stage AC-DC converter is used for the dynamic power transmission and power decoupling.The hybrid rectifier provides normal mode and fault-tolerant mode in the case where one of the units is damaged or disconnected,which improves the reliability of the system.The operating principles,control method,as well as the design consideration of the hybrid rectifier in the normal mode and the fault-tolerant mode are analyzed in detail.The experimental results show that the proposed hybrid rectifier can decouple the pulsed power of the load from the average power of the AC power source to eliminate the AC pulse current,both in normal mode and fault-tolerant mode.The introduction of the fault-tolerant mode further improves the stability and reliability of the power supply system.The hybrid rectifier has advantages in efficiency,volume&weight,reliability,and can be applied for the pulsed load power supply system.To meet the requirements of the new generation of the pulsed load power supply systems based on the active rectifier,a dual DC output AC-DC converter with pulsed power decoupling is proposed.Based on the idea of the dual power path,the power supply system composed of two two-level AC-DC converters is studied,which are used for the dynamic power and steady-state power transmission,respectively.Based on this scheme,a dual DC output AC-DC converter is proposed by integrating the two two-level AC-DC converters.The operating modes of the dual DC output AC-DC converter,i.e.the two-level mode and the three-level mode,are studied.For the two-level mode,the power distribution is achieved with the switching of the operating mode,and a smooth switching method is proposed.For the three-level mode,an improved Space Vector Pulse Width Modulation(SVPWM)strategy with power distributing ability is proposed.The basic characteristics of the dual DC output AC-DC converter in the two operating modes,including the output voltage range,power distribution capability,input current quality and system efficiency,are compared and analyzed.The experimental results show that the dual DC output AC-DC converter can achieve pulsed power decoupling and improve the power quality of the power supply system,which provide a reference for the new generation of the pulsed load power supply system with active AC-DC converter.