Abstract
LLC resonant DC-DC converter has wide working range, good voltage gains, and soft switching performance. So it is widely used in power transformation systems of new energy equipment such as UPS, electric vehicle, and photovoltaics (PV). The conduction loss in the main circuit constitutes the main loss occurred in the LLC resonant converter. It may greatly improve the power conversion efficiency of the converter by reducing the conduction loss. To solve the above problems, a method is proposed to calculate and design the parameters of the resonant element in this paper. This method abandons the traditional time sequence mathematical model, and, in order to reduce the effective value of the main loop current of resonant converter, the phase sequence modal analysis is applied. With ZVS as the constraint condition, the design parameters of resonance element that can minimize the conduction loss can be obtained. In the final part, an experimental prototype (300W) is designed and the effectiveness of the mentioned method is verified.
Highlights
With the global climate deterioration and the increase of energy demand, distributed generation (DG) which is utilized by the users was used to converse the clean energy to electricity, such as wind power and solar power systems
The LLC resonant converter works in P mode at this moment, the voltage is normalized to 2nVo, and the current is normalized to 2nVo/Zr, Lr and Cr start resonating, voltage of magnetic inductance Lm is clamped on 2nVo, resonant current iLr will change in sine wave shape, and its equation of iL
Electric vehicles, photovoltaic power generation, and other fields, DC-DC converter is the physical port that achieves energy-interaction between DC bus and distributed power supply and energy storage system (ESS), so its working capability and the power conversion efficiency is of great significance
Summary
With the global climate deterioration and the increase of energy demand, distributed generation (DG) which is utilized by the users was used to converse the clean energy to electricity, such as wind power and solar power systems. The switches of the primary side and the synchronous rectifier of the secondary side can work under the condition of soft switching without any auxiliary network It has great advantages in conversion efficiency. In literature [4– 8], a detailed analysis of the basic working principle of the LLC resonant converter is conducted, and the basic calculation and design methods of resonance parameters are proposed. All of these methods mentioned above are based on timing sequence, while they lack enough accuracy in calculating the energy loss as introduced in literature [9–13]. Through the modal analysis based on the mode of the phase sequence, more accurate relation curves which can show the maximum load voltage gain varying over frequency can be obtained, and the accurate modeling and calculation can be realized for the operational model of converter, and the optimized parameters which minimize the power loss of the converter can be obtained
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