Research On Hybrid Switching Control Based On Flexible Variable Madal UPQC

With the rapid development of global economy,the power electronic devices are playing an increasingly important role in the power system,but its widely used will result in many power quality problems,which cause serious damage to the safety of the power system and electricity users.The presence of defects in the face of the current power quality devices,such as certain functions are not comprehensive,bulky,idle and low economy,to develop a better flexibility,higher efficiency and economy,the new structure became more popular research.Therefore,the paper takes the power quality regulator as the research object,and studies the main circuit topology of UPQC which is carried out and its control method,which has definite theoretical significance and use value.Based on the two types of power quality disturbances,in the distribution network,a flexible variable modal UPQC of three-switch three-phase three-wire main circuit structure is proposed on the main circuit topology of back-to-back UPQC.This structure can be in keeping with the traditional structure of three kinds of compensation function requirements,not only can solve the back-to-back structure in some converter idle problems in the compensation method,also reduces the volume and improve the flexibility of installation of equipment,reduce the investment.Firstly,the main circuit structure and working principle of flexible variable modal UPQC are introduced in detail.The switching state,conduction mode and compensation function of the three modes of serial operation,parallel operation and serial-parallel operation are analyzed,and the corresponding of the mathematical model is established.Secondly,on the basis of the theory of hybrid switching system,the general model of switching control is extended to the multi-level switching model,and the hybrid structure of flexible variable modal UPQC is analyzed,and the hybrid switching system model of system working process is constructed.Then,according to the principle of the system's output control,operation mode and sub-mode continuous operation characteristics,the switching rule of hybrid switching control is studied.And based on DSP technology a preliminary design is carried out for flexible variable modal UPQC.Finally,the simulation model is constructed by using Matlab/Simulink simulation platform.The result proves the feasibility and validity of the proposed topology of flexible variable modal UPQC main circuit and its control method.Flexible variable modal UPQC is a kind of mode of flexible converter topology,with a more flexible,more efficient and more economical advantages,the work process with a typical discrete,continuous characteristics.Based on the theory of mixed switching system,this paper analyzes the characteristics of systematically hybird structure.Compared to the traditional control mode,it can be more clearly and more intuitively presented the switching process between subsystems.Therefore,the research content of the paper has certain theoretical significance.