三相四线制并联有源滤波器若干问题的研究

发布时间：2018-04-29 15:54

本文选题：三相四线制 + 有源滤波器　；参考：《西南交通大学》2014年博士论文

【摘要】：随着现代电力电子技术的发展,各种电力电了装置得到了广泛的应用,但也给电网带来了严重的谐波污染,威胁着电网和用电设备的安全。我国的低压配电系统主要采用三相四线制方式供电。三相四线系统中主要有对称的三相负载和单相负载,这些负载大多具有非线性特性及不对称性,这将在系统中产生很大的谐波电流及过大的中线电流。对称三相非线性负载产生正序谐波和负序谐波,但单相非线性负载虽然单台功率较小,但因其数量庞大,将在电网中产生大量的零序谐波电流,而且在中线上相互叠加,所产生的谐波是极其严重的。它一方面使得中线电流大大超过额定值,可能导致中线故障,产生中点移位,造成用户端相电压不平衡,影响用电安全：另一方面可能使设备因过热而损坏绝缘,危及设备安全。此外,电力系统中的谐波电流还将增加线路损耗,降低功率因数等。所以,三相四线制系统中的谐波抑制、中线电流消除及三相电流平衡具有重要的意义,已成为电力系统电能质量问题的研究热点。针对目前采用四桥臂有源滤波器解决三相四线制系统中的谐波及中线电流过大等问题,本文开展了以下几个方面的研究工作。首先,讨论了基于瞬时无功功率理论的三相四线制系统谐波电流检测方法,分析和比较了p-q法和p-q-r法的原理及特点。基于瞬时无功功率理论的谐波检测方法的原理是通过坐标变换,将三相电流中基波正序分量变换为直流分量,谐波及基波负序分量变换为交流分量,采用低通滤波器分离直流分量和交流分量,经反变换后得到含无功分量及谐波分量的参考电流信号。但当电源电压不对称或含有谐波时,坐标变换后的直流分量将含有基波负序分量,因此,常规的p-q法无法得到良好的效果,这可通过锁相环提取电源电压正序分量来消除检测误差。论文分析了常规锁相环的原理及结构,提出了一种新的基于非线性PI调节器的三相锁相环及三相四线制系统的改进p-q谐波检测算法,仿真及实验结果表明所提算法具有更好的检测精度及动态性能。其次,基于瞬时无功功率理论的谐波检测方法虽然是一种应用非常广泛的方法,但需要复杂的坐标变换、低通滤波器及锁相环等。为此,针对三相四线制系统的结构特点,提出了一种基于二维线性滤波器的三相四线制系统谐波电流检测方法。该方法将三相四线制系统分解为3个独立的单相系统,用3个二维线性滤波器分别提取不对称的各相基波电流分量,再通过瞬时对称分量计算,得到三相系统的基波电流正序分量,从而提取出谐波电流及无功电流分量。二维线性滤波器是基于自适应陷波器构造,与系统参数及电源电压无关,因此,所提算法具有很好的鲁棒性,且检测精度与电源电压无关,且无需低通滤波器及锁相环。在对称电源电压、不对称电源电压、对称畸变电源电压及不对称畸变电源电压四种情况下的仿真及实验结果证明了所提方法的正确性和有效性。再者,电流滞环控制因其无条件的稳定性、响应的快速性、与系统参数无关、很高的控制精度及实现简单等优点,在有源滤波器的电流控制中得到广泛运用,但其最大的问题是开关频率不固定,开关管的损耗较大。通过理论分析和系统仿真,确定了常规滞环控制方式下影响开关频率的主要因素,提出了一种模糊自适应的可变环宽滞环控制算法。算法根据电源电压的变化及跟踪电流偏差信号的变化,动态地调整滞环的宽度,有效地减小了开关管的开关频率及其变化范围,实现了准定频的滞环控制。通过对常规滞环控制、自适应滞环控制及模糊自适应滞环控制三种方式下的仿真及实验,结果表明,模糊自适应滞环控制方式相较于常规滞环控制方式,开关管开关频率下降了近60%,频率变化范围仅约为原来的30%。此外,通过对单相不对称三电平逆变器结构及原理的深入分析,提出了一种三相四桥臂三电平不对称逆变器拓扑结构,讨论了三相四桥臂不对称三电平结构特点,提出了基于abc坐标系下四桥臂不对称三电平逆变器的SVPWM控制算法。研究了单相不对称三电平逆变器结构及空间矢量调制算法,并将其应用于有源滤波器中,实现了谐波抑制。对单相不对称三电平逆变器的直流侧中点电位变化的原因进行了分析,提出了三电平不对称结构的双闭环中点控制方法,较好地实现了中点电位的控制。通过仿真及实验,验证了所提结构及控制方法的正确性和有效性。最后,以TMS320F2812 DSP为控制核心,研制了小功率并联式三相四桥臂有源滤波器实验样机,完成了相关的实验验证和研究。通过研究和实验验证,本文研究并提出的关于并联式三相四桥臂有源电力滤波器的谐波电流检测算法、模糊自适应滞环控制、四桥臂三电平不对称逆变器结构及其空间矢量控制(SVPWM控制)等关键技术的一些理论和方法是正确和可行的,能够用于有源滤波器的实际开发和生产中
[Abstract]:With the development of modern power electronics technology, all kinds of electrical and electrical devices have been widely used, but it also brings serious harmonic pollution to the power grid, which threatens the safety of power grid and electrical equipment. Our country's low-voltage distribution system mainly uses three-phase four wire system power supply. Three phase and four wire systems are mainly symmetrical three phase load and single. In phase load, most of these loads have nonlinear characteristics and asymmetries, which will produce large harmonic currents and too large midline currents in the system. Symmetric three-phase nonlinear loads produce positive and negative sequence harmonics. Although single phase nonlinear loads are small in single power, a large number of them will produce a large amount of power in the power grid. The zero sequence harmonic current, which is superimposed on the middle line, is extremely serious. On the one hand, it makes the middle line current much more than the rated value, which may cause the midline fault, produce midpoint shift, cause the imbalance of the end phase voltage of the user, and affect the electricity safety: on the other hand, it may cause the equipment to damage insulation due to overheating and endanger the installation. In addition, the harmonic current in the power system will also increase the loss of the line and reduce the power factor. Therefore, the harmonic suppression in the three-phase four wire system, the elimination of the middle line current and the balance of the three-phase current are of great significance. It has become the research hotspot of the power quality problem of the power system. At present, the active filter of the four bridge arm is adopted. In order to solve the problems of harmonic and middle line current in the three-phase four wire system, the following research work is carried out in this paper. First, the harmonic current detection method of three-phase four wire system based on instantaneous reactive power theory is discussed. The principle and characteristics of P-Q and p-q-r are analyzed and compared. Based on the instantaneous reactive power theory, the theory and the characteristics of the system are analyzed and compared. The principle of harmonic detection is to transform the positive sequence component of fundamental wave into DC component in the three-phase current, the harmonic and the negative sequence components of the fundamental wave are transformed into AC components, the DC component and the AC component are separated by the low pass filter, and the reference current signals with the reactive power and the harmonic components are obtained after the inverse transformation, but the power supply is used as the power supply. When the voltage is asymmetrical or harmonic, the DC component after the coordinate transformation will contain the negative sequence component of the fundamental wave. Therefore, the conventional P-Q method can not get a good effect. This can extract the positive sequence component of the power supply by the phase locked loop to eliminate the detection error. The improved P-Q harmonic detection algorithm for the three-phase phase locked loop and the three-phase four wire system of the sex PI regulator. The simulation and experimental results show that the proposed algorithm has better detection precision and dynamic performance. Secondly, the harmonic detection method based on the instantaneous reactive power theory is an unusual and widely used method, but it needs complex coordinate changes. In this way, a three phase and four wire system harmonic current detection method based on two dimensional linear filter is proposed. This method decomposes the three-phase four wire system into 3 independent single-phase systems and extracts the asymmetrical each with 3 two-dimensional linear filters, according to the structure characteristics of the three-phase four wire system. The phase fundamental wave current component is calculated by the instantaneous symmetric component, and the positive sequence component of the basic wave current of the three-phase system is obtained, thus the harmonic current and the reactive current component are extracted. The two-dimensional linear filter is based on the adaptive trap structure and is independent of the system parameters and the power supply voltage. Therefore, the proposed algorithm has good robustness and detection precision. The degree is independent of the power supply voltage, and there is no need for low pass filter and phase locked loop. The simulation and experimental results in four cases of symmetrical power supply voltage, asymmetric power supply voltage, symmetric distortion power supply voltage and asymmetric distortion power supply show that the proposed method is correct and effective, and the current hysteresis control is unstable because of its unconditional stability, The fast response, independent of the system parameters, high control precision and simple realization, has been widely used in the current control of active filter, but its biggest problem is that the switching frequency is not fixed and the loss of the switch tube is large. Through the theoretical analysis and system imitation, it determines the influence of the switching frequency under the conventional hysteresis control mode. The main factor of the rate is a fuzzy adaptive variable ring wide hysteresis loop control algorithm. The algorithm dynamically adjusts the width of the hysteresis loop according to the change of the power supply voltage and the variation of the tracking current deviation signal, effectively reduces the switching frequency and the range of change of the switch tube, and realizes the hysteresis control of the quasi fixed frequency. The simulation and experiment of three kinds of loop control, adaptive hysteresis control and fuzzy adaptive hysteresis control show that the switching frequency of the switch tube is reduced by nearly 60% compared with the conventional hysteresis control mode, and the frequency range is only about 30%., and the single phase asymmetric three level inverter is changed. An in-depth analysis of the structure and principle of a three-phase four bridge arm three level asymmetrical inverter is proposed. The asymmetric three level structure of the three-phase four bridge arm is discussed. A SVPWM control algorithm based on the four arm asymmetrical three level inverter in the ABC coordinate system is proposed. The structure of the single phase asymmetric three level inverter is studied. The space vector modulation algorithm, which should be used in the active filter, realizes the harmonic suppression. The reason for the change of the neutral point potential in the DC side of the single phase unsymmetrical three level inverter is analyzed. The double closed loop middle point control method of the three level asymmetric structure is proposed, which can better realize the control of the midpoint potential. The correctness and effectiveness of the proposed structure and control method are verified. Finally, with TMS320F2812 DSP as the control core, an experimental prototype of a small power shunt three-phase four arm active filter is developed, and the related experimental verification and research are completed. Through the research and experimental verification, the parallel three-phase four bridge arm is studied and proposed in this paper. The harmonic current detection algorithm of active power filter, the fuzzy adaptive hysteresis control, the four bridge arm three level asymmetric inverter structure and the space vector control (SVPWM control) are correct and feasible, and can be used in the actual development and production of active power filter.

【学位授予单位】：西南交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM761;TN713.8

【相似文献】