直流变换器控制方法的研究

发布时间：2018-07-31 05:59

【摘要】：该论文中以提高直流变换器的稳态性能和瞬态响应性能以及指导直流变换器的参数设计为目的，设计出一种间接电压前馈型的滞环控制技术、增强型的滞环控制技术族，研究其动力学行为以及将其运用于Buck和Boost电路后进行深入研究。论文的研究工作主要分为三部分。第一、二部分研究对象为Buck变换器，第三部分研究对象针对Boost变换器。第一部分：基于电容充放电特性的滞环控制策略。提出了一种带有间接电压前馈的滞环控制方法，该方法控制设计简单，控制效果优良，具有较好的稳态和动态性能，基于电容充放电特性的快速滞环（Capacitor Charging and Discharging Fast Hysteretic, CCDFH）控制策略控制电路拓扑结构简单，不需要常规PWM控制中的误差放大器和补偿网络设计，减少了器件的使用数量和补偿网络的设计问题，同时所提出的CCDFH弥补了滞环控制的变频特性，在CCDFH控制中具有保持准恒频的输出效果。给出了CCDFH控制的静态和动态特性分析，同时针对电路各控制参数对稳定性的影响给出了定性定量分析。针对输入电压变化，对输出电压稳态到混沌态的演化，给出了仿真说明和验证，证明了主电路输入电压变化可以引起输出的混沌状态。针对滤波电容取值对输出电压的影响，通过仿真验证了滤波电容的取值大小可以引起输出的混沌态。另外通过仿真验证了ESR与输出电压纹波公式的正确性。推导出了滤波电容ESR临界值确定的方法，并用仿真和理论分析进行了验证，证明了所提出的ESR取值公式的有效性。第二部分：基于电容充放电特性的变滞环阈值自适应控制策略。提出了增强型的变滞环控制、变阈值控制（高阈值或低阈值控制），所提出的控制方法不仅保留了CCDFH控制的优点，同时使得控制效果得以提高，动态响应特性得以改善。提出了在输出负载或者输入电压变动时，利用输入电压的直接前馈或间接前馈信息以及与输出电压反馈相结合的复合前馈滞环控制方法。该方法结合了通过输入电压的变化情况来自动调节滞环宽度和利用输出电压调节电容充放电速率的特性，实现了对电容的充放电速率和滞环宽度的调节，带来了响应速度快和稳态结果好的效果。而且它只需要一个滞环比较器和反馈系数调节电阻，控制电路的器件数量大大减少，成本和体积均得到了较大改善。由于没有使用误差放大器，在消除了补偿电路带来的相位延迟问题的同时，有效提高了控制电路的动态特性。提出了一种带有间接前馈的自适应环宽控制策略，间接前馈控制环主要用来响应输入电压变化，改变电容充放电速率进而改变占空比。反馈控制环包括两个控制环（Rf环和k2环），Rf反馈控制环通过输出电压的变化来调节电容充放电速率进而改变占空比，k2反馈控制环主要将输出电压的变化信息反馈到滞环阈值中来，来快速调节占空比，实现输出的快速稳定响应。本滞环控制中占空比的调节主要由电容的充放电和滞环阈值两个因素来构成，本设计中的三个控制环共同实现了对于这两个影响因素的有效利用控制，，发挥了较好的控制效果。第三部分：运用于Boost电路的准恒频滞环控制针对Boost控制电路，传统控制方法难以满足对其诸如快速调节，良好动态调节性能等效果。基于此，我们提出一种基于电容充放电特性的滞环控制方法。使用该方法的控制电路不仅所需器件较少，有利于满足变换器的轻小薄要求，易于集成，功率密度高；而且在动态响应特性中，该控制电路在负载跃升和跃降时超调量和收敛时间均优于传统PWM控制电路。同时具有较宽的功率输出范围，弥补了常规滞环控制的变频问题，具有准恒频特性。
[Abstract]:In order to improve the steady-state performance and transient response performance of the DC converter and to guide the parameter design of the DC converter, an indirect voltage feedforward hysteresis loop control technology is designed, and the enhanced hysteresis control technology family is studied, and its dynamic behavior and its application to the Buck and Boost circuits are studied in depth. The research work of this paper is mainly divided into three parts. The first part is the Buck converter, the second part is the Buck converter, and the third part is the Boost converter.
The first part: hysteresis control strategy based on capacitor charging and discharging characteristics.
A hysteresis loop control method with indirect voltage feedforward is proposed. This method has simple control design, good control effect, good steady state and dynamic performance. The fast hysteresis loop (Capacitor Charging and Discharging Fast Hysteretic, CCDFH) control strategy based on capacitance charging and discharging characteristics is simple, and it is not required. The design of error amplifier and compensation network in conventional PWM control reduces the number of devices used and the design of compensation network. At the same time, the proposed CCDFH compensates the frequency conversion characteristic of hysteresis control and has the output effect of keeping the quasi constant frequency in the CCDFH control. The static and dynamic characteristics of the CCDFH control are given, and the electricity is also analyzed. The influence of each control parameter on stability is qualitatively and quantitatively analyzed.
In view of the change of input voltage, the simulation and verification of the output voltage steady to chaotic state are given. It is proved that the input voltage change of the main circuit can cause the chaotic state of the output. The simulation results show that the value of the filter capacitor can cause the chaotic state of the output by simulation of the effect of the value of the filter capacitor on the output voltage. In addition, the correctness of the ESR and the output voltage ripple formula is verified by simulation. The method of determining the critical value of the filter capacitor ESR is derived and verified by simulation and theoretical analysis, and the validity of the proposed ESR value formula is proved.
The second part: a threshold adaptive control strategy based on capacitor charging and discharging characteristics.
An enhanced hysteresis loop control, variable threshold control (high threshold or low threshold control) is proposed. The proposed control method not only preserves the advantages of the CCDFH control, but also improves the control effect and the dynamic response characteristics. The direct feedforward of the input voltage when the output load or the input voltage changes is proposed. The indirect feedforward information and the compound feedforward hysteresis control method combined with the output voltage feedback are combined to adjust the hysteresis width automatically and adjust the charge and discharge rate by using the output voltage through the change of the input voltage, and realize the adjustment of the charging and discharging rate and the hysteresis width of the capacitor, which brings the noise. The effect of fast speed and steady state results is good. Moreover, it only needs a hysteresis comparator and feedback coefficient to adjust the resistance, the number of devices in the control circuit is greatly reduced and the cost and volume are greatly improved. As the error amplifier is not used, the phase delay problem of the compensation circuit is eliminated effectively. Control the dynamic characteristics of the circuit.
An adaptive loop width control strategy with indirect feedforward is proposed. The indirect feedforward control loop is mainly used to respond to the input voltage change, change the charge and discharge rate of the capacitor and change the duty ratio. The feedback control loop includes two control rings (Rf ring and K2 ring), and the Rf feedback control loop passes the change of the output voltage to adjust the charge discharge rate of the capacitor. In order to change the duty cycle, the K2 feedback control loop mainly feedback the change information of the output voltage to the hysteresis threshold to quickly adjust the duty cycle and realize the fast and stable response of the output. The control of the duty cycle in the hysteresis control is mainly composed of two factors, the charge discharge and the hysteresis threshold of the capacitor, and the three control rings in this design together. The effective control of these two factors has been realized and good control effect has been achieved.
The third part: quasi constant frequency hysteresis control applied to Boost circuits.
In view of the Boost control circuit, the traditional control method is difficult to meet the effect of fast adjustment and good dynamic adjustment. Based on this, we propose a hysteresis control method based on the capacitance charge discharge characteristics. The control circuit using this method is not only less needed, but also easy to meet the light and thin requirements of the converter and easy to set. The power density is high, and in the dynamic response characteristic, the control circuit is superior to the traditional PWM control circuit when the load jump and the jump drop. It has a wide power output range, which makes up the frequency conversion problem of conventional hysteresis control, and has the quasi constant frequency characteristic.
【学位授予单位】：上海电力学院
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM46

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