Topology Of The High Power Soft—switching PWM Converter

With the more and more widespread applications of power electronic converters, they are expected to develop to be more miniaturized, higher-frequency and more efficient. However, the traditional converters which are always working under the condition of hard-switching now face some bottlenecks:the switching frequency is not high enough to get better quality of the output waveforms, the switching losses are not small enough to get the design of converters’ cooling system easier, more terribly, the power electronic devices’ hard-switching mode brings current and voltage spikes which cause serious EMI problems especially in high power applications. Considering all these disadvantages of traditional converters, the soft-switching converters which own higher frequency,nearly-zero switching losses and EMI influence should be one of the development tendency of power electronic converters.Firstly, this paper mainly does some research on the Auxiliary Resonant Commutated Pole (ARCP) soft switching technique applied in high-power converters. The ARCP soft switching technique is one of the most developed soft-switching technique which belongs to Zero-Voltage Transition(ZVT) soft switching technique. With this soft-switching topology, the main power electronic devices achieve zero-voltage turn-on and the snubber capacitors parallel to the main power electronic devices significantly decrease the turn-off losses by limiting the dv/dt of the core devices. Meanwhile, the control strategy of the ARCP soft-switching converters has a good fit to the traditional converters’ except that the auxiliary power electronic switching devices should be controlled independently.Secondly, this paper advances the loss calculation model of the ARCP soft-switching topology during a single switching cycle. Also, losses distribution during commutations are analyzed in this section.Thirdly, this paper introduces the design method of the resonance parameters and the control parameters based on the principles of the minimum of commutation losses and the optimization of control of auxiliary power switching devices.Fourthly, this paper lays emphasis on the research of some problems found in the soft-switching dual-pulse experiment. These problems are mainly due to the non-ideal characteristics of the hardware components of the soft-switching test bench.Lastly, the loss comparison experiment is accomplished in this paper on the base of the single-phase dual-pulse testing bench hardware which owns the DC-link voltage up to600VDC and the load current700A. With the experimental platform, loss comparison between the hard-switching and soft-switching working mode was carried out. The experimental results indicated that the zero-voltage-transient commutation of main power electronic devices were achieved and it is highly identical with the ideal ARCP theories. Through the experiment, the statistical analysis of the loss distribution in the commutations of the ARCP power module was verified to find out what to be done to reduce the total loss. However, the equivalent series resistance of the resonant circuits principally due to the self-made resonant inductance is so high that the losses involved in the soft-switching commutations have no remarkable advantage towards the losses in the hard-switching commutations.In addition, the issues such as dead-time effect of the ARCP soft switching inverter and the imbalance of ARCP neutral point potential which had got few concerns in the past were also analysed in this paper.