| The thesis is based on the micro-grid wind turbine platform and analyzes4performance requirements for DC/DC converter:wide input range, high efficiency, isolated, power tracking. LLC resonant topology is selected as the design of DC/DC power conversion part.This paper analyzes the working state of LLC, states the error sources of FHA gain model and modifies it. Based on the most difficult working point to achieve ZVS, a critical magnetizing inductance design method is proposed.It’s not necessary for LLC converter to achieve full load output through the input range because of the specificity of fan load. Therefore, enlarging the resonant inductance can improve the frequency and effective duty in low input voltage condition, and high frequency leads to large input impedance and high efficiency. Output power is controlled by DSP, which is used to imitate the performance of power tracking.In order to satisfy the constant power output performance requirement under high wind speed condition, LLC converter must work in the buck mode. A variable modility control method is proposed. According to the input voltage, buck mode is divided into several parts, and each part uses PFM control or PWM control respectively. This variable modility control method can achieve both ZVS and ZCS. |
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