【摘要】 当LLC全桥变换器的变压器副边绕组匝数较多时,分布电感和分布电容较大,在变换器的幅频特性中出现附加的谐振峰,使调频控制的控制范围减小,甚至完全失效。提出LLC全桥调频控制和移相控制相结合的变结构控制方法,兼顾扩大控制范围和减小开关应力两方面的性能。根据大功率配网故障定位仪的要求,研制了LLC全桥变结构控制的高压直流变换器样机。用F28335 DSP实现整机控制,完成调频和移相控制的转换,并根据故障状态,分别实现恒流、恒功率和恒压反馈控制。设计的高压直流变换器,最大输出电压为20 k V,最大输出电流为0.5 A,最大输出功率4 k W。样机在实际应用中取得良好效果,验证了分析方法和设计方案的正确性。更多还原

【Abstract】 The large distributed inductance and distributed capacitance caused by the more number of transformer secondary windings makes the unexpected resonant peak appear in amplitude-frequency characteristic of the converter,which can reduce the control range of the frequency modulation control(FMC),or result in complete failure. A new variable structure control method in combination with LLC full bridge FMC and phase-shifting control(PSC)is proposed,which can expand the control range and reduce the switching stress. According to the requirements of the high-power distribution network fault locator,the prototype of HVDC converter with LLC full bridge variable structure control was developed. The complete machine control is realized by DSP F28335 to accomplish the conversion between FMC and PSC. The constant current,constant power and constant voltage feedback control are implemented according to the fault state. The maximum output voltage of the HVDC converter is 20 k V,maximum output current is 0.5 A,and maximum output power is 4 k W. The prototype achieved perfect effect in practical application. The correctness of the analysis method and design scheme was verified.更多还原