带不平衡负载的三相四桥逆变器控制技术研究

发布时间：2018-11-05 20:22

【摘要】：电能质量的一个极为重要参数是电压的平衡度,它影响电力运行设备的用电安全和正常运行。三相高性能逆变电源作为核心部件广泛使用在一些重要工业用电设备中,所以研究高性能的三相逆变器对提高电能质量具有十分重要的现实意义。对两种桥臂逆变器的主电路系统模型做了详细的理论推导,可知对于不平衡负载或非线性负载而言,三桥臂逆变器无法使系统输出电压满足国标要求;而四桥臂逆变器就能很好地调节三相之间的中点电位,保持三相电压的对称性,且多出的一个桥臂为不平衡电流提供输出通道。为了实现三相逆变器输出电压的高度对称性及各相间单独控制,本文采用了四桥臂结构和经典的PI双闭环控制策略。对于反馈控制系统采用实时的三相电压对称分量法完成正序、负序、零序的分解,经过正负序Park转换,得到彼此耦合DQ轴电压、电流分量。为了实现在DQ坐标系下各分量解耦,加入电流前馈解耦调节器,使输出的D轴、Q轴分量转换为独立的直流量,便于实现高精度、低稳态误差的控制方案,使逆变器输出三相电压高度对称。而零序分量在DQ旋转坐标系下值为零,采用简单的误差PI调节器即可实现零序分量为零。通过与三桥臂二维脉宽调制方法的对比,类推出四桥臂拓扑结构在abc坐标系下的三维空间电压矢量调制方案,并对三维空间电压矢量调制方案做了详细的理论研究,设计了简化方案的实现步骤,为四桥臂逆变器的开关器件提供八路控制信号,实现四桥臂功率器件的有序开通和关断,保证输出电压的对称性。完成了三相四桥逆变器硬件电路的详细设计及基于DSP处理器的程序代码编写。通过阻性对称负载与阻性不对称负载、非线性不对称负载及输出缺相运行等几种负载形式的闭环仿真,验证了反馈控制系统能有效消除负载不平衡时对电压不对称的影响,三相电压不对称率低于5%,控制策略是可行且有效的。
[Abstract]:One of the most important parameters of power quality is the voltage balance, which affects the safety and normal operation of power equipment. Three-phase high performance inverter is widely used in some important industrial equipments as the core component, so it is very important to study the high performance three-phase inverter to improve the power quality. The main circuit system model of two kinds of bridge leg inverter is deduced in detail. It is known that for unbalanced load or nonlinear load, the three-leg inverter can not make the output voltage of the system meet the requirements of national standard. The four-leg inverter can adjust the midpoint potential between the three phases and maintain the symmetry of the three-phase voltage, and the extra leg provides the output channel for the unbalanced current. In order to realize the high symmetry of the output voltage of the three-phase inverter and the separate control of each phase, the four-arm structure and the classical PI double closed-loop control strategy are adopted in this paper. For the feedback control system, the three-phase voltage symmetry component method is used to decompose the positive sequence, the negative sequence and the zero sequence. After the positive and negative sequence Park conversion, the coupling DQ axis voltage and current components are obtained. In order to realize decoupling of each component in DQ coordinate system, adding current feedforward decoupling regulator, the output D axis and Q axis component can be converted into independent direct flow, which is convenient to realize the control scheme of high precision and low steady state error. The output voltage of the inverter is highly symmetrical. The zero sequence component is zero in the DQ rotation coordinate system, and the zero sequence component can be realized by using a simple error PI regulator. By comparing with the three-arm two-dimensional pulse width modulation method, the three-dimension space voltage vector modulation scheme of the four-arm topology structure in the abc coordinate system is deduced, and the three-dimensional space voltage vector modulation scheme is studied in detail. The implementation steps of the simplified scheme are designed to provide eight control signals for the switching devices of the four-leg inverter, to realize the orderly opening and switching off of the four-leg power devices, and to ensure the symmetry of the output voltage. The hardware circuit of three-phase four-bridge inverter is designed in detail and the program code based on DSP processor is written. Through the closed-loop simulation of several load forms, such as resistive symmetric load and resistive asymmetric load, nonlinear asymmetric load and output short phase operation, it is verified that the feedback control system can effectively eliminate the effect of load imbalance on voltage asymmetry. The three-phase voltage asymmetry ratio is less than 5, and the control strategy is feasible and effective.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM464

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