Research On Input Parallel Output Series High-Step-up DC-DC Converter

With the rapid development of world industrial economy and the increasingly serious problem of environmental pollution,it is imperative to develop and utilize new energy efficiently.Photovoltaic(PV)and fuel cell belong to low-voltage renewable energy in new energy power generation system,and the output voltage of single battery can not meet the DC side voltage requirements of grid connected inverter.Therefore,high gain and high efficiency DC-DC boost converter is an important part of new energy generation system.On the other hand,in order to increase the life of PV and fuel cell and improve the stability of the whole system,the high gain DC-DC converter with low input current ripple and low output voltage ripple has great research significance.Due to the parasitic parameters of the devices,it is difficult to obtain high voltage gain for traditional boost converter.Introducing coupling inductors is an effective way to improve the voltage gain of converters.Based on the analysis and comparison of various ways and structures to improve the boost capability,a high gain DC-DC converter based on coupled inductor and interleaving parallel technology is proposed in this paper.Firstly,two primary windings of the coupled inductor are connected in parallel at input side,which reduces the current stress of the switch and the conduction loss of the switch.Secondly,interleaving control is used for driving signal on two switches in order to make the current on the primary windings of the two coupled inductors complementary,which reduces the input current ripple.Furthermore,the double voltage unit composed of two coupled inductors secondary windings in series and capacitor-diode further improves the boost capability of the converter.The leakage energy is absorbed by the embedded circuit and then released to the output side,therefore,the energy of leakage inductance is recycled and the voltage stress of the switches is also reduced.Based on the above converter,a coupled inductor soft switching high gain DC-DC converter with ultra-low voltage stress is proposed in this paper,which has high volyage gain and low ripple of input current and output voltage.At the same time,the voltage stress of diodes is is greatly reduced.Therefore,the efficiency of the converter can be further improved by selecting high performance devices.In addition,two switches can realize zero current switching on(ZCS)due to the effect of leakage inductance,so the switching loss is greatly reduced,and the reverse recovery of output diode is effectively suppressed.The operating principles and the steady-state analyses of two proposed converters are discussed in details in the paper,and the simulation platforms are implemented for performance verification.The state space average method is used to analysis small-signal model of proposed converter,and the appropriate closed-loop compensation controller is designed to improve the stability of converters.Finally,the hardware circuit and software of TMS320F2812 as the core controller are designed,and the experimental platform is built to verify the correctness of the theoretical analysis.