Research On Key Technologies Of Low-Cost And High-Reliability Non-Common-Ground Interleaved Boost Type DC/DC Converters For Photovoltaic Application

In recent years,environmental problems have become increasingly serious and primary energy is on the verge of scarcity,which promoting the application of solar energy and other green energy in distributed photovoltaic power generation systems.As the represent of the Boost type DC/DC converters,non-common-ground interleaved Boost type DC/DC converters have become the key power conversion equipment in distributed photovoltaic power generation systems due to the advantage of low ripple,simple modulation and strong scalability.How to realize that the low-cost and high-reliability operation of the non-common-ground interleaved Boost type DC/DC converters has important research significance.Firstly,this paper introduces the existing soft-switching non-common-ground interleaved Boost type DC/DC converters and their working mechanism,and analyzes the drawback of resonant soft-switching interleaved Boost type DC/DC converters and leakage inductor soft-switching interleaved coupled inductor Boost type DC/DC converters in terms of causing the resonant spike on switches and additional cost of devices.Then,this section analyzes the mechanism of non-resonant soft-switching technique and its application,which can provide theoretical guidance for the research of this paper.Secondly,according to the realization mechanism of non-resonant soft-switching technique,this paper proposes the topology building methods based on the multiplexing of passive components and constructs the low-cost non-common-ground interleaved capacitor clamped DC/DC converter based on non-resonant soft-switching technique.By comparing with other non-common-ground interleaved Boost type DC/DC converters based on resonant soft-switching technique or the soft-switching technique based on leakage inductor,it is proved that the proposed converter can greatly reduce the current stress of switches and the additional cost for achieving soft switching,and avoid the spikes of resonant current.In addition,only an auxiliary inductor,operating in discontinuous conduction mode,with few μH is used to achieve the soft-switching of all switches and diodes,which can facilitate the condition for achieving soft switching.Finally,a test platform with 30～40V/400 V 400W was built to verify the theoretical analysis of the proposed converter.Finally,this paper analyzes the common start-up problem of non-common-ground interleaved Boost type DC/DC converters,and proposes an active flexible start-up method for non-common-ground interleaved Boost type DC/DC converters.After that,the hardware parameters and programming flows of the active flexible start-up method are analyzed.To be noticed that the proposed method can be employed into these converters with different types of Boost structures.Then,the detailed comparisons of different start-up methods are given.On one hand,compared with the programmed soft start-up method,the proposed start-up method has more significant effects,which can completely eliminate the start-up surge current and the output voltage overshoot.On the other hand,compared with the pre-charging method with resistance,the proposed method has smaller volume and doesn’t affect the operation of power converters after starting up,which can realize the high reliability start-up process.