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具有PI补偿环路的电流型Boost变换器的稳定性分析、电路仿真与硬件实验

作者:完美论文网  来源:www.wmlunwen.com  发布时间:2019/10/10 9:08:23  

摘要:在开关功率变换器中,Boost变换器广泛应用在功率因数校正、LED驱动、新能源发电等各种应用场合。在Boost变换器控制环路设计中,由于其控制至输出传递函数中存在右半平面零点,导致传统电压型控制的补偿器设计非常困难。相比于传统电压型控制,电流型控制可有效消除右半平面零点的影响,因此,近年来电流型控制Boost变换器得到了广泛的关注。电流型控制具有电流内环和电压外环两个控制环路,且电流内环对开关变换器的稳定性影响已得到了广泛关注和研究。然而,有关电压外环对开关变换器稳定性影响的报道相对较少。本论文将以电流型Boost变换器为研究对象,深入研究电压外环对其稳定性的影响。

首先,将峰值电流型(Peak Current Mode, PCM)控制应用于Boost变换器,其电压外环采用比例-积分(Proportional Integral, PI)补偿器。分析了PI补偿PCM控制Boost变换器的工作原理,建立了其二阶离散映射模型。基于该模型,采用分岔图、最大Lyapunov指数及特征根轨迹等分析方法,研究了补偿环路反馈增益和输出电容对Boost变换器的稳定性影响,给出了相应的临界稳定条件。结果表明:增大补偿环路反馈增益将降低PCM控制Boost变换器的稳定性;增大输出电容值将提高PCM控制Boost变换器的稳定性。利用PSIM电路仿真验证了理论分析的正确性。

进一步,将研究工作拓展至电压外环采用PI补偿器的谷值电流型(Valley Current Mode, VCM)控制Boost变换器。建立了PI补偿VCM控制Boost变换器的二阶分段线性模型,该模型考虑了输出电容的等效串联电阻(Equivalent Series Resistance, ESR)。基于该模型,研究了PI补偿VCM控制Boost变换器随反馈增益和输出电容ESR变化的稳定性机理,并给出了临界稳定条件。结果表明,增大补偿环路反馈增益将同样降低VCM控制Boost变换器的稳定性,而增大输出电容ESR将提高VCM控制Boost变换器的稳定性。利用PSIM电路仿真验证了理论分析的正确性。

最后,搭建了PI补偿PCM和VCM控制Boost变换器的硬件实验样机,硬件电路实验的结果很好地验证了本文理论分析和PSIM电路仿真的正确性。

关键词:Boost变换器;PCM控制;VCM控制;PI补偿器;反馈增益

In switching power converters, boostconverter is widely used in variety of application scenarios, such as powerfactor correction, LED driver, new energy generation and so on, For boostconverter with traditional voltage mode control, it is difficult to design itscompensator due to the existence of the right half-plane (RHP) zeros in thecontrol to output transfer function. Compared with traditional voltage modecontrol, current mode control can effectively eliminate the influence of theRHP zeros. Therefore, current mode controlled boost converter has been widelyconcerned in recent years. Current mode control has two control loops: innercurrent loop and outer voltage loop. The influence of inner current loop on thestability of switching converter has been widely concerned and studied.However, there are relatively few reports about the influence of outer voltageloop on the stability of switching converters. In this paper, the current-modecontrolled boost converter is taken as an example, and the stability effect ofouter voltage loop is deeply studied.

Firstly, the peak-current-mode (PCM)control is applied to boost converter, and the proportional-pntegral (PI)compensator is used in the outer voltage loop. The proportional principle ofPCM controlled boost converter with PI compensator is analyzed, and itssecond-order discrete-time model is established. Based on the model, thestability effect of compensation loop feedback gain and output capacitance onthe boost converter is studied by using bifurcation diagram, maximum Lyapunovexponent and characteristic root loci. Furthermore the corresponding criticalstability condition is derived. The results indicated that the stability of PCMcontrolled boost converter can be reduced by increasing the feedback gain ofcompensation loop, and can be improved by increasing the output capacitance.The correctness of theoretical analysis is verified by PSIM circuit simulation.

Furthermore, the research work is extendedto valley-current-mode (VCM) controlled boost converter with PI compensator Asecond-order piecewise linear model of VCM controlled boost converter with PIcompensator is established, where the equivalent series resistance (ESR) of theoutput capacitor is taken into account. Based on the model, the stabilitymechanism of outer voltage loop feedback gain and output capacitor ESR in VCMcontrolled boost converter with PI compensator is studied, and itscorresponding critical stability condition is derived. The results indicatedthat the stability of VCM controlled boost converter can be reduced by increasingthe feedback gain of compensation loop, and can be improved by increasing theoutput capacitance ESR. The correctness of theoretical analysis is verified byPSIM circuit simulation.

Finally, the hardware experiment prototypesof PI compensated PCM and VCM controlled boost converter are built. The resultsof hardware circuit experiment well verify the correctness of theoreticalanalysis and PSIM circuit simulation.

关键词:Boost变换器;PCM控制;VCM控制;PI补偿器;反馈增益

Boost converter; PCM control; VCM control;PI compensator; feedback gain

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