High-Frequency Isolated Bi-directional Half-Bridge DC/DC Converter And Experimental Validation

The oil, coal and other traditional resources are dwindling that prompted us to use more new energy. New energy technologies have been rapidly developed and widely applied. The new energy largely access to power system has brought unprecedented challenges for stability and power quality of power system. The application of energy storage technology can reduce the influence of new energy power generation access to power system. At the same time, the lack of lithium batteries can be applied to the lithium battery energy storage system that achieve the gradient utilization. As an important part of lithium battery energy storage system, the bi-directional DC/DC converters become a focus of research.The paper is supported by the Beijing Science and Technology Commission "Research and demonstration application of large-scale photovoltaic power plants based on the unified power control equipment and DC microgrid technology(D131104002013003)".The high-frequency isolated bi-directional half-bridge converter is applied to the lithium battery energy storage system,through the phase shifting control can charge or discharge to the battery. The main contents are as follows:First, the isolated bi-directional DC/DC converter topology, modeling method, application status, control technology and soft switching technology are analyzed and compared in this paper. Combined with the actual needs of the task, select the high-frequency isolated bi-directional half-bridge converter as the object of study. The working principle of high-frequency isolated bi-directional half-bridge converter are introduced in detail. The steady output characteristics is analyzed;According to the main circuit laboratory low detailed physical models of design parameters, and simulate the steady-state conditions of the converter in the Boost and Buck mode;Also the soft switching conditions of high-frequency isolated bi-directional half-bridge converter is derived, and verified by simulation.Second, The mathematical modeling and control system of high-frequency isolated bi-directional half-bridge converter are researched. The state space average model is deduced, The model is reduced and simplified to establish a simplified state space average model and the linear small signal model; And on the basis of the small signal model, build the transducer voltage closed-loop system control structure, design and optimize the voltage loop control system through the potter diagram and the unit impulse response;And the symmetrical half bridge two-way dc converter control strategy, the duty ratio control strategy, phase angle control strategy, control mode and have been researched in detail.Finally, this paper designs high-frequency isolated bi-directional half-bridge converter control system, the sampling circuit and a drive circuit in detail. Design an experimental converter prototype of700W,which adopts TMS320F28335DSP as the control core, is built; Proposed by DSP to realize digital phase shifting method, and is experimentally verified on the prototype. The experimental results show that the high-frequency isolated bi-directional half-bridge converter topology has good steady-state performance, power switch tube can achieve soft switch, also suggests that by DSP software programming to realize digital phase shifting method is completely feasible. The works above make way for deeply researching based on the combination of the battery energy storage cascading power conversion system.