| Since entering the new century,with the increasing global warming and global energy shortage,the shortcomings of the traditional energy industry are becoming more and more obvious.The new energy industry provides new possibilities for solving the energy shortage and the sustainable development of human beings.But the new energy technology is not stable and the cost is high,so countries focus on improving efficiency and reducing costs in the new energy industry.The energy wall is a new energy solution for home users proposed by Tesla.Specifically,it uses a large number of small batteries to form a medium-sized energy storage power generation system,because the volume of light can be hung on the wall,so it is called the energy wall.Main availability of energy walls The photovoltaic energy storage inverter system caters to the needs of the development of distributed power supply,smart grid and energy Internet.It is also an important technical support to solve the problems of energy and environmental protection in China.A single-phase photovoltaic energy storage inverter is developed in this paper.The core circuit of this product is an improved parallel-series dual active bridge battery charging and discharging circuit and a H4 bridge rectifier inverter circuit.The improved parallel-series combined dual active bridge circuit replaces the series of the secondary side DAB module by the direct series of the transformer secondary side winding.Although the improved circuit requires higher voltage resistance to the secondary side switch tube,However,the reliability and cost are improved by reducing the number of DAB modules.The improved dual active bridge circuit can simplify the complexity of circuit design.To solve the disadvantages of the traditional external phase-shifting control method,which is difficult to realize zero voltage switch(ZVS)and single PWM phase-shifting control method in light load,a compound phase-shifting control strategy is proposed to minimize the effective value of inductance current in light load and critical realization ZVS,The effective value of inductance current is close to the minimum value in heavy load and can realize the ZVS.of all switches.The principle,modulation strategy and control method of single-phase H4 bridge two-way rectifier inverter are studied in this paper to realize PFC rectifier and parallel and off-grid inverter.PFC rectifier connected to the power grid for battery charging,to meet the grid side for the unit power factor requirements.The grid-connected inverter converts the energy of DC side photovoltaic cell and battery to AC side grid,while off-grid inverter gives DC side electric energy to load.A small signal control model of dual active bridge circuit is derived in this paper.The control model of new dual active bridge circuit in four charge and discharge modes is established.Parameter tuning and PSIM simulation are realized by using these four models.According to the required 5 kW prototype performance index,the main parameters of the two main circuits are designed.An optimization method of resonant inductance of two-way DC/DC circuit,the calculation method of isolation capacitance and the selection of switch tube are given.A calculation method of filter inductance and capacitance in bidirectional AC/DC inverter is also given,and the switch tube devices in the system are selected.Final The experimental prototype is built for the single-phase photovoltaic energy storage inverter system,and the theory and method are verified. |
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