【作者】 刘晓；

【导师】 张庆范；

【作者基本信息】 山东大学 ， 电力电子与电力传动， 2014， 博士

【摘要】 AC-DC矩阵变换器是一种拓扑结构新颖的降压型通用整流装置,由于无需大容量储能元件,所以具有结构紧凑、能量密度高、可靠性和可维护性好的优点,非常适合对重量、体积、效率和可靠性要求较高的应用场合。同时,其正弦输入电流的功率因数可以自由调节,最高可达1,具有天然的能量回馈能力,可以输出双极性电压并导通双向电流,允许负载四象限运行,符合理想整流器的基本要求。本文将理论分析、计算机仿真和样机实验相结合,系统、深入地研究了AC-DC矩阵变换器的空间矢量调制策略、新型非线性控制策略和谐振抑制方法等关键技术问题,为AC-DC矩阵变换器的实用化提供了理论支持和技术准备。本文首先从AC-DC矩阵变换器的空间矢量调制策略出发,深入分析了AC-DC矩阵变换器的变换关系。为了抑制共模电压峰值和减少窄脉冲的产生,提出了一种利用有效电流矢量代替零电流矢量的改进型空间矢量调制策略及其优化的开关调制模式。然后在考虑换流时间的基础上,推导了使用传统空间矢量调制策略搭配不同开关调制模式,及使用改进型空间矢量调制策略时,窄脉冲产生几率与调制度和扇区角度的关系表达式。理论分析证明,所提算法不仅对共模电压幅值、有效值和谐波含量有明显的抑制效果,还可在更宽的调制度范围内获得较优的输入、输出性能。仿真和实验结果验证了算法的可行性和有效性。针对AC-DC矩阵变换器抗电网畸变能力较差的问题,首先定量分析了AC-DC矩阵变换器在电源电压幅值不平衡和波形非正弦情况下的工作特性,推导了输入、输出各电量的解析表达式。然后提出了一种αβ坐标系下空间矢量调制策略的通用实现方法,其特点是可以灵活构造期望输入电流矢量,改变AC-DC矩阵变换器的工作特性。最后以获得平直的输出直流电压为目的,提出了一种期望输入电流矢量的构造方法,可以同时补偿电源电压矢量幅值和角速度不恒定造成的输出直流电压脉动。同时,该补偿控制策略有效减少了开平方、三角函数和反三角函数等复杂运算的次数,更利于工程实现。理论分析的正确性和算法的可行性得到了仿真实验的验证。提出了一种基于空间矢量表达和滑模变结构的非线性控制策略。推导了AC-DC矩阵变换器的误差状态空间模型,讨论了滑模切换线的选取方法,给出了滑动模态的可到达条件并设计了开关表。着重研究了控制器参数对变换器性能的影响,从最大化滑模存在域宽度和降低开关频率的角度出发,给出了控制器参数选择方法。实验结果证明,基于本控制策略的AC-DC矩阵变换器具有算法简单、无稳态误差、动态响应速度快、抗网侧干扰能力强和输入功率因数高等优点。输入LC滤波器是AC-DC矩阵变换器中不可或缺的重要组成部分,但是其固有的谐振特性易被电源电压中的谐波污染或输入电流中的谐波分量激发,造成变换器无法正常工作。为了在抑制输入滤波器谐振的同时,改善AC-DC矩阵变换器的运行特性,提出了一种两相同步旋转坐标系下的双闭环反馈控制策略。分别利用单周期控制技术和经典控制理论设计了输入电流内环控制器和负载电压外环调节器,并从数学的角度讨论了单周期控制策略与空间矢量调制策略的异同点。提出了一种具有选频特性的主动阻尼控制策略,并将其与输入电流内环控制器相结合,避免了类似算法中复杂的归一化和三角函数运算,降低了软件复杂度。在考虑实际控制器延时的基础上,分析了控制器参数对系统稳定性的影响。提出了一种基于DSP和CPLD的单周期控制器实现方法,使得数字化单周期控制成为可能。实验结果验证了所提算法的有效性和数字单周期控制的可行性。本文通过对AC-DC矩阵变换器调制策略和控制策略的研究,得出了一些有意义的经验和结论,为AC-DC矩阵变换器进一步的实用化研究提供了一定的技术基础。更多还原

【Abstract】 The AC-DC matrix converter (AC-DC MC) is a novel step-down AC-DC power conversion topology possessing many unique advantages over the existing rectifiers. Due to the absence of bulky energy storage components, the AC-DC MC shows a highly compact structure, high power density, high reliability and good maintainability, which make it very suitable for the application areas where weight, volume, efficiency and reliability are of importance. Besides, it can generate DC output with arbitrary polarity and wide-range controllable magnitude while drawing sinusoidal input current from the power source at unity or any specified input power factor, and very easy to extend to regenerative operation. All these highly attractive characteristics make the AC-DC MC an ideal future solution for AC-DC power conversion. Systematic and deeply studies have been conducted in this dissertation focused on the modulation algorithms and the control strategies of the AC-DC MC, as well as its input filter resonance mitigation methods by means of theoretical analysis, computer simulation and prototype experiment. These researches provide theoretical and technological foundation for the practical implementation of the AC-DC MC.Based on the in-depth analysis of the basic space vector modulation (SVM) strategy, an improved SVM method is developed for practical implemented AC-DC MC. The objectives of reducing the common-mode voltage (CMV) and eliminating the narrow pulses are accomplished by replacing the zero space vectors with suitable couple of active ones. Further considering the commutation time, the relationship between the modulation index, the sector angle and the probability of narrow pulse in the conventional and the proposed SVM method are derived. The proposed scheme not only can reduce the magnitude, the root mean square value and the harmonic components of the CMV, but also guarantees a better input and output performance in wider modulation ratio range. Simulation and experimental results verified the conclusions and the validity of the optimized strategy.In order to improve the poor performance of the AC-DC MC when the power source is distorted, the input and output characteristics of the AC-DC MC are theoretically analyzed in the conditions that the source voltages are unbalanced and non-sinusoidal respectively. Then, a universal implementation method in the αβ stationary coordinates for the SVM strategy is proposed, which allows the change of the performance of the AC-DC MC by flexibly modifying the demanded input current vector. At last, an input current reference construction method is proposed with the purpose of generating steady output DC voltage. The proposed compensation strategy not only eliminates the low-frequency ripples at the output side of the AC-DC MC caused by the magnitude and the angular frequency variation of the source voltage vector, but also simplifies the calculation process by reducing the requirements for complex real-time calculation operations including square root, trigonometric functions and anti-trigonometric functions. The correctness of the theoretical investigation is verified and the effectiveness of the proposed compensation method is testified by computer simulations.A novel direct control method applying the sliding-mode variable structure control technique and the space vector approach, aiming at both regulating the input currents and the output voltage, is presented. The proposed method is developed based on the modeling of the variable structure system considering the switching matrix and the dynamics of its associated input and output filters. Afterwards, the sliding surfaces and the switching laws are determined, the sliding surface reaching conditions are checked and the entire switching table is established. With the purposes of maximizing the sliding mode extension domain and minimizing the switching losses, the influence of the controller parameters to the converter performance is investigated in detail, and a practical parameter tuning approach is given. The designed sliding mode controller is tested by simulations and experiments. The obtained results show that the proposed control scheme guarantees fast dynamic response and precise control actions, especially ensuring a unity input power factor regardless of the system parameters and providing better output behavior with distorted source voltages.The input LC filter is essential in the AC-DC MC system, but its inherent resonance figure makes it easily to be excited by the harmonic pollution in the power source or by the harmonic components in the input currents drawn by the converter itself. This phenomenon may cause instability during operation, even result in severe system failure. With the purpose of enhancing the performance of the AC-DC matrix converter, a double closed-loop control method is proposed under the dq rotating reference frame. The inner-loop input current controller and the outer-loop load voltage controller are designed based on the one-cycle control (OCC) algorithm and the classical control theory respectively. And the consistency of the proposed OCC control method and the SVM strategy is mathematically proofed. A frequency selective active damping (AD) method by employing the grid-side input currents as feedback signals is developed so as to mitigate the input filter resonance actively. The proposed AD method is introduced into the inner-loop OCC controller to avoid the requirement of normalization and complex modulation index control in the existing strategies. A model including the proposed method and the input filter is established with considering delay caused by the actual controller, based on which, the active damping parameter design principle is investigated. A realization approach of the proposed OCC controller is proposed, which is suitable for the implemented digital control system utilizing DSP and CPLD chips. The experimental results are given to demonstrate the correctness of the theoretical analysis and the practicability of the proposed digital OCC control approach.This dissertation mainly pays attention on the modulation and control strategies of the AC-DC matrix converter. Some valuable experience and ideal results are given, which found the technological foundation for the AC-DC matrix converter’s further industry applications.更多还原