基于PIDNN的降压三电平直流变换器的控制策略研究

发布时间：2018-06-04 20:03

本文选题：三电平直流变换器 + 飞跨电容电压　；参考：《重庆大学》2016年硕士论文

【摘要】：多电平变换器具有开关管电压应力低、输出电压谐波小、容量大等优点,被广泛应用并得到快速发展。三电平直流变换器是多电平变换器中应用最为广泛的一种,相对于其他多电平变换器,其优势在于采用最少的开关管最大程度地降低了开关管的电压应力,而且在降低开关管电压应力的同时改善了输出性能,减小了输出滤波器体积,提高系统的动态特性,非常适用于要求中大功率而系统又不过于复杂的应用场合。然而在实际工程应用中,控制电路、驱动电路以及各个开关管之间的参数都不可能完全一致,从而导致各个开关管的导通关断时间不相等,系统参数变化以及负载突变等都有可能导致飞跨电容电压不稳定,从而导致开关管电压应力不相等,损坏电容及开关器件,三电平波形也不对称,失去其基本优势。因此,为了确保三电平变换器正常工作,必须对飞跨电容的电压采取一定的控制措施。三电平变换器的输出电压与飞跨电容电压之间存在强耦合的关系,而且其中存在开关变换,属于非线性系统,如何高效稳定地控制飞跨电容电压和输出电压是系统设计成败的关键。PID控制器结构原理简单,稳定精度高,可靠性能好等优点,目前在很多方面都有着广泛的应用,但是PID控制器必须依赖于精确的数学模型,然后调整出合适的PID控制器参数才能发挥出其优点。人工神经元网络是由大量简单的神经元按照一定的连接方式形成的仿生智能网,具有本质的非线性,多层神经元网络具有逼近任意函数的能力,对系统的控制不依赖于被控对象的数学模型、对被控对象的非线性具有天然的自适应能力,非常适合应用于三电平开关变换器中飞跨电容电压以及输出电压的控制。因此,将PID控制作为基本单元融合进入神经元网络,得到PID神经元网络(Proportional-Integral-Derivative Neural Network,PIDNN)控制器,兼顾神经网络和PID控制器的优点,既具有PID控制器的优点,同时可以自动补偿非线性系统在模型阶次、参数和输入信号等方面的变化,对被控对象具有非常好的适应性,非常适用于对降压三电平变换器的控制,增强其鲁棒性的同时提高了其控制性能。本文详细分析了降压三电平直流变换器的基本工作原理及其性能优点,给出了PIDNN控制器的工作原理,并针对文中的降压三电平直流变换器,设计出了PIDNN控制器,对具有强耦合性的输出电压和飞跨电容电压进行控制。在理论研究的基础上,对所设计的控制器进行仿真试验并对结果进行了分析,结果验证了理论分析的正确性以及PIDNN控制器在对降压三电平直流变换器控制上的优越性。
[Abstract]:Multilevel converter has been widely used and developed rapidly because of its advantages of low voltage stress, low output voltage harmonics and large capacity. Three-level DC / DC converter is one of the most widely used multilevel converters. Compared with other multilevel converters, the advantage of three-level DC / DC converter is that the minimum switching tube is used to minimize the voltage stress of the switch tube. Moreover, the output performance is improved while the voltage stress of the switch is reduced, the output filter volume is reduced, and the dynamic characteristics of the system are improved. It is very suitable for the application of medium and large power and the system is not too complicated. However, in the practical engineering application, the parameters of control circuit, drive circuit and each switch tube can not be completely consistent, which leads to the difference of the turn-on time of each switch tube. The variation of system parameters and the sudden change of load may lead to voltage instability of flyover capacitor, which leads to the voltage stress of switch tube is not equal, the capacitance and switch device are damaged, and the three-level waveform is not symmetrical, thus losing its basic advantage. Therefore, in order to ensure the normal operation of the three-level converter, it is necessary to take certain measures to control the voltage of the flyover capacitor. The output voltage of the three-level converter is strongly coupled with the flyover capacitor voltage, and there is a switching transformation among them, which is a nonlinear system. How to control the transcapacitor voltage and output voltage efficiently and stably is the key to the success or failure of the system design. The pid controller has the advantages of simple structure, high stability precision, good reliability and so on. It has been widely used in many fields. But the PID controller must depend on the precise mathematical model, and then adjust the appropriate parameters of the PID controller to give full play to its advantages. Artificial neural network (Ann) is a bionic intelligent network formed by a large number of simple neurons according to a certain connection mode. It has essential nonlinearity and multilayer neural network has the ability to approximate any function. The control of the system does not depend on the mathematical model of the controlled object, and it has natural adaptive ability to the nonlinearity of the controlled object. It is very suitable for the control of the flyover capacitor voltage and the output voltage in the three-level switching converter. Therefore, the PID control is fused into the neural network as the basic unit, and the PID neural network Proportional-Integral-Derivative Neural Network (PIDNN) controller is obtained, which takes into account the advantages of the neural network and the PID controller, and has the advantages of the PID controller. At the same time, the nonlinear system can automatically compensate for the model order, parameters and input signals, so it has a very good adaptability to the controlled object, and is very suitable for the control of the step-down three-level converter. Its robustness is enhanced and its control performance is improved. In this paper, the basic working principle and the performance advantages of the step-down three-level DC / DC converter are analyzed in detail, the working principle of the PIDNN controller is given, and the PIDNN controller is designed for the reduced voltage three-level DC / DC converter in this paper. The output voltage and the flyover capacitor voltage with strong coupling are controlled. On the basis of theoretical research, the designed controller is simulated and the results are analyzed. The results verify the correctness of the theoretical analysis and the superiority of the PIDNN controller in the control of the three-level DC / DC converter.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM46

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