高性能直流变换器系统稳定性问题研究
发布时间：2018-09-13 08:56
【摘要】：摘要：随着电源、负载特性需求的不同,越来越多的DC-DC变换器采用高阶化拓扑或者采用分布式级联方式相互连接形成高性能的直流变换器系统,以满足不同的设计要求。直流变换器系统的稳定性一直以来是人们研究的热点。变换器的小信号模型参数是影响变换器系统稳定性的重要因素,本文针对影响变换器系统稳定性的关键参数：被控对象模型传递函数、音频敏感率、输入阻抗以及输出阻抗进行分析,并提出相应的优化方法以改善变换器系统的稳定性。 目前已有大量文献对基本的二阶变换器拓扑进行了深入分析,已解决了稳定性问题,但是在包含太阳能电池板、蓄电池等装置的场合,为了满足输入输出电流连续的要求,往往需要加入额外的滤波器或者采用含有多个电感电容元件的高阶变换器。高阶变换器的模型中含有多个零极点,尤其当模型中存在右半平面零点时,被控对象传递函数的相频曲线容易较早穿越.180。,限制反馈环路增益的带宽。本文归纳了优化高阶变换器被控对象的阻尼设计方法,针对广泛应用于航天电源系统的Superbuck变换器拓扑,提出一种RC阻尼设计方法,从而避免其被控对象传递函数中存在右半平面零点,保证其模型满足最小相位系统的条件,从而提高变换器的稳定性。 采用输入电压前馈的方法可以在理论上实现变换器的音频敏感率(输入电压扰动.输出电压扰动传递函数,audio susceptibility)等于零。但是当变换器模型的阶次较高时,理论所需的前馈控制器传递函数较为复杂且计算过程繁琐。为了简化求解过程,本文提出一种简化变换器电路模型的方法,而不会影响所得前馈控制器的准确性。此外,本文提出采用比例控制器代替理论所需的前馈控制器进行控制的方法,并分析了在这种控制方式下音频敏感率能够大幅度衰减的有效频率范围与主电路参数之间的关系,指出了比例前馈控制器仅取决于变换器的稳态电压增益比的规律。 在级联系统中,即使变换器单独能够稳定工作,级联时也未必稳定,这是由于级联的前后级变换器阻抗存在相互作用。为了提高级联系统的稳定性,需要减小前后级变换器的阻抗交截范围,对于DC-DC变换器而言,一方面希望降低前级变换器的输出阻抗,另一方面希望增大后级变换器的输入阻抗。 本文基于DC.DC变换器的一般性小信号模型,提出了以平均输入电流环为内环、输出电压环为外环的双环控制方法,分析了在这种控制方式下影响变换器输入阻抗的因素,并给出了改变内环电流采样系数前后变换器输入阻抗的量化计算过程。分析表明,当电流内环的截止频率大于电压外环截止频率时,增大电流采样系数,能够提高电流内环环路增益,有效增大变换器的输入阻抗。从而在级联系统中,能够有效减小负载变换器的输入阻抗与源变换器输出阻抗的交集,提高级联系统的稳定性。 同样的,为了优化变换器的输出阻抗,提出了一种在变换器输出端口模拟出并联虚拟电阻的控制方法,可以适用于模型中不含右半平面零点的变换器拓扑。这种控制方法在不改变变换器稳态工作点的基础上仅改变了交流小信号模型,因此不会带来额外的功率损耗。通过采用有源阻尼控制器的方法,可以有效降低变换器输出阻抗的谐振峰值,改善品质因数,达到优化变换器输出阻抗特性的目的。
[Abstract]:Abstract: With the different demand of power supply and load characteristics, more and more DC-DC converters adopt high-order topology or adopt distributed cascade interconnection to form high-performance DC-DC converter systems to meet different design requirements. Small signal model parameters are important factors affecting the stability of the converter system. In this paper, the key parameters affecting the stability of the converter system are analyzed, including the controlled object model transfer function, audio sensitivity, input impedance and output impedance, and the corresponding optimization methods are proposed to improve the stability of the converter system.
At present, a large number of literatures have analyzed the basic second-order converter topology deeply, and solved the stability problem. But in the case of solar panels, batteries and other devices, in order to meet the continuous input and output current requirements, it is often necessary to add additional filters or adopt high inductance and capacitance components. First-order converter. The model of high-order converter contains multiple zeros and poles. Especially when there are right half-plane zeros in the model, the phase-frequency curve of the transfer function of the controlled object is easy to cross. 180., which limits the bandwidth of the feedback loop gain. A RC damping design method is proposed to avoid the existence of right half-plane zeros in the transfer function of the controlled object and ensure that the model satisfies the condition of the minimum phase system.
The audio susceptibility of the converter can be realized theoretically by using the input voltage feedforward method. However, when the order of the converter model is high, the transfer function of the theoretical feedforward controller is complex and the calculation process is complicated. This paper presents a method to simplify the circuit model of the converter without affecting the accuracy of the feed-forward controller. In addition, a proportional controller is proposed to replace the feed-forward controller required by the theory. The effective frequency at which the audio sensitivity can be greatly attenuated is also analyzed. The relationship between the rate range and the parameters of the main circuit indicates that the proportional feed-forward controller only depends on the steady-state voltage gain ratio of the converter.
In cascaded systems, even if the converter can work stably alone, the cascade is not necessarily stable. This is due to the interaction between the impedance of the cascaded front and back converters. On the other hand, it hopes to increase the input impedance of the post converter.
Based on the general small-signal model of DC.DC converter, a double-loop control method with average input current loop as inner loop and output voltage loop as outer loop is proposed in this paper. The analysis shows that when the cut-off frequency of the current inner loop is greater than that of the voltage outer loop, increasing the current sampling coefficient can improve the gain of the current inner loop and increase the input impedance of the converter effectively. Stability of cascaded systems.
Similarly, in order to optimize the output impedance of the converter, a control method is proposed to simulate the parallel virtual resistance at the output port of the converter, which can be applied to the converter topology without the right half-plane zeros in the model. This method can effectively reduce the resonant peak value of the output impedance of the converter, improve the quality factor and optimize the output impedance characteristics of the converter.
【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM46
本文编号：2240672
[Abstract]:Abstract: With the different demand of power supply and load characteristics, more and more DC-DC converters adopt high-order topology or adopt distributed cascade interconnection to form high-performance DC-DC converter systems to meet different design requirements. Small signal model parameters are important factors affecting the stability of the converter system. In this paper, the key parameters affecting the stability of the converter system are analyzed, including the controlled object model transfer function, audio sensitivity, input impedance and output impedance, and the corresponding optimization methods are proposed to improve the stability of the converter system.
At present, a large number of literatures have analyzed the basic second-order converter topology deeply, and solved the stability problem. But in the case of solar panels, batteries and other devices, in order to meet the continuous input and output current requirements, it is often necessary to add additional filters or adopt high inductance and capacitance components. First-order converter. The model of high-order converter contains multiple zeros and poles. Especially when there are right half-plane zeros in the model, the phase-frequency curve of the transfer function of the controlled object is easy to cross. 180., which limits the bandwidth of the feedback loop gain. A RC damping design method is proposed to avoid the existence of right half-plane zeros in the transfer function of the controlled object and ensure that the model satisfies the condition of the minimum phase system.
The audio susceptibility of the converter can be realized theoretically by using the input voltage feedforward method. However, when the order of the converter model is high, the transfer function of the theoretical feedforward controller is complex and the calculation process is complicated. This paper presents a method to simplify the circuit model of the converter without affecting the accuracy of the feed-forward controller. In addition, a proportional controller is proposed to replace the feed-forward controller required by the theory. The effective frequency at which the audio sensitivity can be greatly attenuated is also analyzed. The relationship between the rate range and the parameters of the main circuit indicates that the proportional feed-forward controller only depends on the steady-state voltage gain ratio of the converter.
In cascaded systems, even if the converter can work stably alone, the cascade is not necessarily stable. This is due to the interaction between the impedance of the cascaded front and back converters. On the other hand, it hopes to increase the input impedance of the post converter.
Based on the general small-signal model of DC.DC converter, a double-loop control method with average input current loop as inner loop and output voltage loop as outer loop is proposed in this paper. The analysis shows that when the cut-off frequency of the current inner loop is greater than that of the voltage outer loop, increasing the current sampling coefficient can improve the gain of the current inner loop and increase the input impedance of the converter effectively. Stability of cascaded systems.
Similarly, in order to optimize the output impedance of the converter, a control method is proposed to simulate the parallel virtual resistance at the output port of the converter, which can be applied to the converter topology without the right half-plane zeros in the model. This method can effectively reduce the resonant peak value of the output impedance of the converter, improve the quality factor and optimize the output impedance characteristics of the converter.
【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM46
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