Research On Parallel Resonant DC Link Inverter

With the continuous development of power electronic technology,inverter plays an increasingly important role in the fields of solar power generation,aviation power supply and motor speed regulation.Since the 1980s,the fully controlled devices represented by IGBT have been widely used.At the same time,people have higher requirements for high frequency,miniaturization and lightweight of inverter.Aiming at the problems of traditional hard switching inverter,such as large switching loss and electromagnetic interference,soft switching technology is proposed to meet these requirements.Among many soft switching inverter topologies,auxiliary resonant commutated pole inverter and resonant DC link inverter are favored by many scholars because of their superior performance.In this paper,the development of resonant DC link inverter is first introduced,then several typical resonant DC link inverter topologies are deeply analyzed.There are many problems in these topologies.For example,the voltage stress of switches are high in some topologies,the control is difficult in some topologies that needs to set the threshold value of inductor current,large capacity electrolytic capacitors are need in DC bus of some topologies,the cost of some topologies are high and the practicality are reduced because of using coupled inductors or transformers.In order to solve these problems,a novel parallel resonant DC link inverter is proposed.The proposed inverter not only has the advantages of simple structure,high conversion efficiency and low voltage stress,but also can realize zero voltage switching of inverter main switches and zero voltage or zero current switching of auxiliary switches.At the same time,the power in the auxiliary commutated circuit is small,and the freewheeling diodes of inverter can turn off under zero current condition,which overcomes the problem of reverse recovery.Moreover,there is no large capacity capacitors between DC bus so that there is no neutral point potential variation problem.Moreover,the DC bus voltage can cross zero at any time and last for the required time according to the PWM modulation and soft switching operation requirements of the inverter,and various modulation strategies can be flexibly adopted.Under the proposed modulation strategy,this paper analyzes the operation principle,softswitching implementation condition,loss of components and parameter design procedure of the soft-switching inverter.Finally,the simulation experiment results are given to demonstrate the validity and features of the soft-switching inverter.