【作者】 于海坤；

【导师】 许建平；

【作者基本信息】 西南交通大学 ， 电力电子与电力传动， 2011， 硕士

【摘要】 功率因数校正(Power Factor Correction, PFC)技术可有效地减少网侧输入电流谐波含量并提高电源功率因数,是电网供电用电设备中不可或缺的重要组成部分。在各种PFC变换器电路拓扑中,Boost变换器因其拓扑结构简单、变换效率高、控制策略易实现等优点,被广泛应用于PFC电路中。工作于不连续导电模式(Discontinuous Conduction Mode, DCM)和连续导电模式(Continuous Conduction Mode, CCM)的Boost PFC变换器应用非常广泛,但二者均存在负载功率范围受限的缺点。伪连续导电模式(Pseudo Continuous Conduction Mode, PCCM)是一种介于DCM与CCM之间的新型工作模式。相比于DCM Boost变换器,PCCM Boost变换器的输出电压、电感电流纹波小,且负载输出能力强。与CCM Boost变换器相比,PCCM Boost变换器控制到输出的传递函数不存在右半平面(Right Half Plane, RHP)零点,进而具有理想的动态性能。因此,PCCM是一种具备优良工作特性的新型工作模式。本文提出工作于PCCM模式的Boost PFC变换器,在深入分析PCCM Boost PFC变换器的前提下,根据其特有的两个控制自由度,建立了电压环与电流环并行的控制环路。针对宽负载范围内具有高功率因数的控制目标,充分利用PCCM模式平均电感电流大于平均输入电流的特点,提出以负载电流为基准量实时调整参考电感电流谷值的控制策略。在此基础上,详细设计了电感电流谷值跟踪的数字控制算法和电压PI调节器参数。对PCCM Boost PFC变换器与传统DCM和CCM模式Boost PFC变换器进行了仿真验证。结果表明,负载功率较大时,DCM Boost PFC变换器的电感电流峰值远大于PCCM和CCM模式,大幅增加了开关管和EMI滤波器成本；PCCM和CCM Boost PFC变换器的电感电流峰值和纹波较小,具有应用于大功率场合的优良工作性能。在负载功率较小时,PCCM Boost PFC变换器实时降低参考电感电流谷值,使变换器稳定地工作在PCCM模式,保证变换器输入电流具有较高的正弦度；而此时CCM Boost PFC变换器的输入电流在输入电压过零点附近发生畸变,严重降低了变换器的功率因数。因此,在综合考虑功率因数、开关管电流应力、EMI等关键性能指标的前提下,宽负载范围下的PCCM Boost PFC变换器表现出了更加优越的工作特性。最后,本文设计了一台输出功率范围为70W-400W的实验样机,进一步对PCCM Boost PFC变换器和CCM Boost PFC变换器的工作性能进行了对比和验证。更多还原

【Abstract】 Power factor correction (PFC) technology which is an indispensable component of the electrical equipment supplied by power system can effectively reduce the current harmonics and improve the power factor. Boost converter is widely used as PFC circuit because of many advantages, such as the simple topology, high efficiency and easily achieved control strategy.Boost PFC converters are generally designed to operate in discontinuous conduction mode (DCM) or in continuous conduction mode (CCM). However, it is known that the converter suffers from restricted load range in the two operation modes. Pseudo continuous conduction mode (PCCM) is a novel operation intervened between DCM and CCM. Compared with DCM Boost converter, the PCCM Boost converter has a smaller voltage and current ripple, resulting in greater capacity of taking heavy load. Besides, there is no right half plane (RHP) zero in the control to output transfer function which, however, exists in CCM Boost converter. So the PCCM Boost converter exhibits a very attractive feature on transient response. On the whole, PCCM is a novel mode with excellent performance.A novel PFC converter operating in pseudo continuous conduction mode is proposed in this paper. On the premise of studying PCCM Boost PFC converter, two side-by-side loops are established and designed to control the typical two degrees of freedom. To extend the load range of Boost PFC converter, the point that the average inductor current is higher than the average input current in PCCM is perfectly utilized, which is meet by calculating and adjusting the reference valley value of inductor current on the basis of load current. Based on which, the digital valley current control strategy of current loop and PI compensation of voltage loop is designed.To verify the theoretical analysis, the PCCM Boost PFC converter has been simulated and compared with the Boost PFC converter operating in CCM and DCM controlled by conventional technique. Simulation results show that, when the Boost PFC converter operates at high output power, the inductor current peak value in DCM operation is much higher than that in PCCM and DCM operation, which would obviously ehance the switch and EMI cost. The PCCM and CCM Boost PFC converter with low inductor current peak value and ripples have good performance for high-power application. On the other hand, if the output power is reduced, the PCCM Boost PFC converter could regulate the reference valley value of inductor current in time and keep stable operation mode, and then have sinusoidal input current. However, the input current of CCM Boost PFC converter at low output power is non-sinusoidal, resulting in a relatively low power factor. Therefore, when the overall performance including power factor, switch current stress and EMI is taken into account, the PCCM Boost PFC converter exhibits more excellent capability for wide load range application.The performance of PCCM Boost PFC converter and CCM Boost PFC converter is compared and verified by using an 70W～400W experimental prototype.更多还原