【作者】 谢斌；

【导师】 康勇； 戴珂；

【作者基本信息】 华中科技大学 ， 电气工程， 2010， 博士

【摘要】 电力电子技术的广泛应用为工业设备提供了高速、高效和节能的控制手段,但同时也给电网注入了不可忽视的无功以及谐波电流。有源电力滤波器是一种高效、稳定、灵活的优化电能质量的重要而且先进的手段,它的应用在提高公用电网质量上将占据重要地位。本文首先介绍了谐波的产生及危害、国际及国家规定的谐波标准、谐波抑制的方法、有源电力滤波器的分类以及基本工作原理。并联型有源电力滤波器常见的主电路结构有三相三线APF、电容中点型三相四线APF和三相四桥臂APF。数学模型是所有研究工作的基础,本文分别建立了三种主电路在同步旋转坐标系下的数学模型。虽然这些数学模型中存在着d轴与q轴电流的耦合,但在同步旋转坐标系下基波正序分量被变换成直流分量给控制策略带来了优势。对于三种主电路来说,在同步旋转坐标系下的双闭环控制策略基本相同。三相三线APF采用了SVPWM策略,电容中点型三相四线APF采用了SPWM策略,三相四桥臂APF采用了3D-SVPWM策略。调制策略的不同造成了直流侧电压利用率的不同,也即是相同的直流侧电压下APF的补偿能力不同。电容中点型APF与三相四桥臂APF相比有着以下缺点：由于采用了SPWM算法,输出波形畸变率较大,直流侧电压利用率较低,需要提高直流侧电压以满足补偿精度的要求；由于电容中点与零线相连,当需要补偿不平衡电流时,电容上会流过补偿电流,将会导致电容的使用寿命的减少。而优势在于结构简单,节省了一个桥臂的IGBT及输出电抗；SPWM算法实现简单,编程容易；由于该主电路与三相三线有源电力滤波器使用相同的主电路、控制电路,在实际工业应用时,可补偿三相三线系统和三相四线系统的谐波电流,对于不同的系统采用不同的控制软件即可。总的来说,目前国内外的APF产品多采用电容中点型的拓扑结构,这样既可以应用于三相三线系统,也可以应用于三相四线系统。直流侧电压控制是并联型有源电力滤波器的关键技术之一。直流侧电压的指令值都是根据电网电压的工作范围、APF的直流侧电容、额定输出电流、PWM逆变器输出侧电感、电流电压调节器以及调制策略等参数设计一个固定值,这样设计出来的直流侧电压指令值通常比较高。而较高的直流侧电压需要较大的直流侧电容耐压值同时带来了较大的开关损耗。直流侧电压的大小影响了APF的功率损耗大小。另一方面,直流侧电压的大小又会影响APF的补偿性能。本文提出了一种采用下垂调节器来控制直流侧电压指令值的控制策略。当电网电压升高时,提高直流侧电压,从而提高APF的补偿性能；当电网电压降低时,降低直流侧电压,在保证APF的补偿性能的基础上降低功率损耗。采用下垂调节器能够实现APF功率损耗和补偿性能的综合优化。谐波检测算法是影响有源电力滤波器性能的一个关键因素。在负载波动时,有源电力滤波器的动态响应速度与谐波电流指令的跟踪速度密切相关。通常负载电流发生变化时,任何谐波检测算法都需要一定的时间来跟踪这个变化,而这个时间的大小也就是谐波检测算法的动态响应时间。在这个动态响应时间内,谐波检测算法计算出的谐波指令是存在误差的。如果在负载电流的波动中含有有功电流的波动,则对于不同的谐波检测算法来说,这个误差也不相同。通常对各种谐波检测算法的分析仅包括了动态响应速度的分析,比较其动态响应时间,而并没有分析在动态响应时间内这个误差对有源电力滤波器的工作是否会造成影响。本文将以同步坐标变换检测算法和递归的离散傅立叶变换检测算法为例,来介绍基波提取算法和谐波直接提取算法在负载波动的暂态过程中对直流侧电压控制的影响。为提高有源电力滤波器的补偿性能和动态响应,本文提出了一种基于多同步旋转坐标的谐波电流控制策略,采用通过与某指定次正序或负序谐波角速度同步的旋转坐标变换,将该指定次谐波变成直流量,实现指定次谐波的检测和PI控制,从而实现对某指定次谐波电流的无静差补偿。完整的谐波电流控制器由多个独立的不同角速度的谐波电流控制器叠加组成。本文建立了APF在谐波旋转坐标系下的数学模型,针对谐波坐标系下的电流耦合提出一种更简单的综合解耦策略。对提出的指定次谐波电流控制器进行了分析,从理论上证明了与传统的电流环控制方法相比,指定次谐波控制可以使得补偿精度明显提高,利用零极点对消方法对提出的控制器参数进行了设计。试验结果验证了提出的控制策略的优越性。最后在以上研究的基础上,本文研制了三台并联型有源电力滤波器装置,采用了三种主电路结构。在这些装置基础上本文对调制策略、谐波检测算法、直流侧电压控制和电流调节器等进行了大量的实验研究,实验验证了本文论述的观点。更多还原

【Abstract】 Being the fast, potent, and economical control means to industrial devices, extensive use of power electronics technology, however, have also deteriorated power quality by injecting the non-negligible harmonics and reactive current to the network. Active Power Filter (APF) is an efficient, stable and flexible advanced mean for optimizing power’s quality, its application will play a significant role in improving the quality of power grid.This paper presents an introduction to the cause and perniciousness of the harmonic current, the harmonic current standard at home and abroad,the ways to-suppress the harmonic current, the classification of APF, and the basic principle of work.The familiar main circuits of shunt APF are three phase three wire APF, split-Capacitor three phase four wire APF, and three phase four leg APF. The mathematical model is the basis of any researches. This paper builds three mathematical models for three main circuits of shunt APF at synchronization rotational coordinate. Although there are coupled currents between d axes and q axes in these models, that the positive sequence component of the fundamental wave is transformed DC is a strong point for control strategy.Double closed-loop control strategies of three main circuits are similar at synchronization rotational coordinate. Three phase three wire APF use Space Vector Pulse Width Modulation (SVPWM) strategy. Split-Capacitor three phase four wire APF use Sinusoidal Pulse Width Modulation (SPWM) strategy. Three phase four leg APF use three-dimensional SVPWM strategy. The difference of the modulation strategy make different DC link voltage usage, that means APF have different compensate ability when DC link voltage is same. What follows is the shortcoming of Split-Capacitor three phase four wire APF in comparison with three phase four leg APF. The distortion of output wave is bigger and DC link voltage usage is lower because of SPWM strategy. Because of the midpoint of capacitor link with zero curve, the compensate current pass through capacitor when APF compensate unbalance current, that will make useful time of capacitor reduce. The strong point of Split-Capacitor three phase four wire APF is this main circuit saves IGBT and output inductance of a leg, and it has same main circuit and control circuit with three phase three wire APF. So it can be applicable three phase three wire system and three phase four wire system by using different software. DC link voltage control is a key technology of shunt APF. DC link voltage reference is designed according to operating space of the Grid voltage, DC link capacitor value, rating output current, output inductance value, current regulator, voltage regulator, and modulation strategy etc. parameters. That will bring the higher designed value of DC link voltage. The higher value will bring the bigger losses of APF. So the value of DC link voltage effects on power losses and compensative ability of APF. This paper introduces a control strategy which uses a drop regulator to regulate the reference value of DC link voltage. When Grid voltage increase, DC link voltage increase by the drop regulator for ensuring compensative ability of APF. When Grid voltage decrease, DC link voltage decrease by the drop regulator for decrease power losses of APF. The drop regulator can realize comprehensive optimization between power losses and compensative ability of APF.Harmonic detection algorithm is an important part of shunt active power filter and significantly affects its filtering characteristics. When the load current is fluctuating, all of harmonic detection algorithms need dynamic response time to track the varied load current and compute the real time harmonic current value. In the dynamic response time, there is error between the computed harmonic current value and the actual harmonic current value. For the different types of harmonic detection algorithms, the error is different. The previous publications are mainly focused on the dynamic response speed and dynamic response time of harmonic detection algorithms and do not analyze the error which will affect the APF system in the dynamic response time. This paper will analyze the error which is caused by computing with the different types of harmonic detection algorithms when the load current is fluctuating and the APF system is working in transient state. Then it moves on to discuss whether the error will affect DC link voltage control.To improve the compensation characteristic and dynamic response of three-phase shunt active power filter (APF), a novel control strategy based on multiple synchronous rotating reference coordinates is proposed. Positive-sequence and negative-sequence harmonic current are both transformed into DC components by respective harmonic synchronous rotating transformation, which are then controlled by proportion-integral (PI) regulators in order to implement zero steady-state error compensation. The complete harmonic current control is realized as the superposition of all individual harmonic controllers. Mathematical model is built based on the harmonic synchronous rotating frame and the combined decoupling control strategy is proposed. Theoretical analysis of harmonic current controller proves that the compensation accuracy is improved compared to the traditional current control of APF. The proposed controller is designed based on the pole-zero cancellation technique. The superiority of the control architecture proposed is verified completely by experimental results.Finally, based on all research above, three prototypes which use three main circuits respectively were realized. On the basis of these prototypes, this paper did a plentiful research on the modulation strategy, harmonic detection algorithm, DC link voltage control, and current regulator. The theories and strategies proposed in this paper are verified completely by experimental results.更多还原