Research On Energy-saving Single-phase Full-bridge Resonant DC Link Inverter

In engineering application,single-phase full-bridge inverters are widely used.It can be used in low power photovoltaic interconnection system.It can also be used for aviation inverters,inverted arc welding machines,bus and vehicle inverters,Metro Auxiliary inverters,etc.In order to improve the performance of single-phase full-bridge inverters,this paper will mainly study energy-saving single-phase full-bridge resonant DC link inverters.In the second chapter,a single-phase full-bridge soft-switching inverter with boost resonant DC link is proposed.During the operinational of the auxibiliary cirecuit locatied in the DC link of the inverateral,not only can the DC bus voltlager change peraciodically to zero,but also the stearady-state valiue of the DC bus voltagery of the invertarer can be increaesed,so that the fundamental wave amplitude of the output line voltage of the inverter can be increased.This method can effectively improve the utilization ratio of DC voltage of inverters and overcome the influence of zero state of DC bus voltage on the utilization ratio of DC voltage.A simple restricted unipolar SPWM control method is adopted.In each switching cycle,only one main switch is needed to switch.The trigger pulse of the main switch is low level time equal to zero state time of DC bus voltage,so that the main switch can complete zero voltage soft switching.In the second chapter,although the proposed inverter has simple structure and simple control method,the clamp capacitor equivalent to a voltage source on the DC bus is difficult to maintain the voltage stability of the clamp capacitor.In order to solve this problem,the single-phase full-bridge resonant DC link inverters with transformer-assisted commutation are proposed in the third chapter.The transformer can supply power to theclamp capacitor to maintain the voltabge stability of the clamp capaceitor,ensure that the steady-state voltage of the DC link is higher than that of the DC power supply of the inverter,and improve the utilization ratio of the DC voltage of the inverter.According to the auxiliary circuit structure proposed in Chapter 3,a single-phase full-bridge resonant DC link inverter powered by totem pole single-phase rectifier is proposed in Chapter 4,while the single-phase full-bridge resonant DC link inverter proposed in Chapter 2 and Chapter 3 is powered by an independent DC voltage source.In this chapter,only a set of auxiliary resonant circuits are set up in the DC link of the converter.Using these auxiliary circuits,the voltage of the output end of the rectifier and the input end of the inverter can be changed to zero respectively.The main switching devices on the bridge arm of the rectifier and the bridge arm of the inverter can complete the zero-voltage soft-switching,and the auxiliary switching can complete the zero-current soft-switching.The auxiliary circuit is in resonance only when the output voltage of the rectifier drops to zero(the input voltage of the inverter rises to steady-state voltage),which reduces the loss of the auxiliary circuit to a certain extent.In this paper,the working prociess of the cirecuit and the reliazing conditional of soft switching are descreaibed in detiail,the paraeimeters of the componeaints are designed,and the theoretical losses of the auxiliary circuit are calculated in detail.The phase plane analysisc methoed and analyze the dynamic characteristics of the inverters.Finally,the MATLAB circeuit model is buillt and the simulational experimente is carreied.The simulation results show that all three single-phase full-bridge resonant DC link inverters can realize soft switching and reduce switching losses.