| Solar energy, as an inexhaustible supply of green energy, is an important part ofstrategies for the world energy development. Photovoltaic technology，one of effectiveways to use solar energy, has been developed rapidly. In stand-alone photovoltaicgeneration system, the operation of the storage link is essential to make the whole systemstably and efficiently. The bi-directional DC/DC converter is a multiduty unit to achievebi-directional flow of energy. It has seized great concern of scholars from all of the world.Bi-directional DC/DC converter is a bridge which connected DC bus of photovoltaicgeneration system with batteries, and is a core component of stand-alone photovoltaicgeneration system. Photovoltaic energy storage system can not only reduce the volumeand weight of the system but also the relevant costs significantly. It has importantresearch value for our future life consequently. The bi-directional DC/DC converter isresearched and applied to photovoltaic generation system in this paper.First, the concept of the bi-directional DC/DC converter and research backgroundare introduced, and the advantages and disadvantages of the current-voltage topology arereviewed. Then the current mode push-pull full-bridge bi-directional DC/DC converter isused to complete a stand-alone photovoltaic energy storage system. The high voltage sideof the converter is a full-bridge structure, and the low voltage side is a current-modepush-pull structure. There are two operating modes: (1) the Buck mode, the high-voltageside switches are driven, the low-voltage side switches are blocked, the excess energy onthe DC bus feeds to the battery side. (2) the Boost mode, the low-voltage side switchesare driven, and the high-voltage side switches are blocked , the battery energy istransformed to the DC bus to stable its voltage. Energy can flow bi-directionally by usingthe control strategy of limiting the current and steadying the voltage in high side andlimiting the voltage and steadying the current in low side.Based on the key technical requirements of the bi-directional DC/DC converter andconsideration of the actual engineering applications, the advantages and disadvantages ofthe current mode push-pull topology are analyzed. The reasons for the start-up current surge, leakage inductance of high frequency transformer caused by the switch off voltagespikes, magnetic reset of the input boost inductor, as well as the magnetic bias of highfrequency transformer are analyzed, theoretically, and a solution is put forward in thispaper. The operation of the current mode push-pull full-bridge bi-directional DC/DCconverter is analyzed, and the PSpice simulation is performed to verify the feasibility ofthe topology. At last, a l kW prototype are founded and the system debugging andexperimental validation are described in detail. The experimental results show that thebidirectional DC/DC converter topology worked with the advantages of simple structure,less components, simple control scheme, an energy bidirectional-flow. |
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