The Research Of Resonant DC-Link Inverter

The advantage and disadvantage of two switching technology are discussed firstly based on soft switching technology and hard switching technology's work features. Conventional hard switching technology has several flaws below:On and off loss, inductive off, capacitive on and diode recover problems. Comparing with it, the loss of on and off decreases markedly, as the switches are on and off in zero voltage or zero current cases. And also the size of converter becomes smaller because of the higher of switching frequency. That is why more and more people pay more attention to it.The technology applied in Resonant DC Link Inverter (RDCLI) is one of soft switching technologies. It makes the current or voltage in DC bus return zero periodically; through resonant technology in the circumstance of switching change. So it can reduce on and off loss of switches.During the analysis of this kind soft switching inverter, simple resonant principles are talked about firstly. Analyzing the work principles, advantage and something need to rectify for different topologies. Further more, a Delta Modulation (DM) is given for the unique structures by researching RDCLI's control strategies. As is known, conventional Pulse Width Modulation(PWM) can acquire good quality outputs, but the resonant time is not comfort with phase'change all the time, so big error will be taken in if using PWM. DM can solve the problem properly. Because DM belongs to tracking control technology. It can follow the instructions real time, adjust inverter action to expectation. All of them are based on setting error value. Although DM can also solve the modulation time error, but the output waveforms can't reach the industrial standard (Total Harmonic Distortion THD).Considering this, a new control strategy called current optimal control (COC) is presented in paper. COC is that system samples the output value real time, comparing with expected value, considering all switching actions available then draw a concluding to decide which way would be fastest and best way to render system smooth. COC can make the ripple of output waveforms smallest, using current prediction control for a tool, which is based on DM, but better than DM.After discussion of principles a control strategies, RDCLI and Active Clamp Resonant DC Link Inverter (ACRLI) are discussed deeply in paper by using the...