PWM整流器的不平衡控制策略研究

发布时间：2018-11-20 20:53

【摘要】：本文在电网电压平衡时控制策略的基础上，研究在电网电压不平衡时，三相电压型PWM整流器的控制策略。不平衡电压可以表示为正序电压，负序电压，零序电压之和。电网不平衡时，由于负序电压的存在，会导致电网角度获取出现偏差，交流侧电流不对称运行，直流母线电压抖动。要对正负序电流分别进行控制，前提是对电压电流进行正负序分离，在论文中介绍了延迟法，陷波器法和低通滤波器法。电网不平衡时，由于负序电压的影响，系统会产生负序电流，负序电流与正序开关函数的乘积，会使输出直流电压产生谐波。针对稳定直流母线和输入三相电流对称运行的不同要求，提出了功率平衡的电压不平衡控制策略和电流对称的电压不平衡控制策略。电流对称的电压不平衡控制策略是在两相正同步参考坐标下实现的，通过对整流桥交流侧的电压矢量叠加负序电压补偿，使负序电流为零，这样就能达到电流对称运行的目的。如果输出侧直流母线电压稳定，在负载不变的情况下，输入的功率是不变的，这就要求输入侧存在负序电流。根据这个原则提出了在两相静止参考坐标下的内模控制器法和两相同步参考坐标下的四闭环控制法，，四闭环控制法是在双闭环的基础上，增加了负序分量的双闭环，控制效果好。两相静止参考坐标的内模控制器法，对于正序分量负序分量用同一个通道进行控制，相对四闭环的系统控制结构简单。在已有实验平台的基础上进行了改造，用接触式调压器构建简单的三相不平衡电压，通过实验验证了对称电流控制策略的正确性。
[Abstract]:Based on the control strategy of voltage balance, the control strategy of three-phase voltage source PWM rectifier is studied in this paper. Unbalanced voltage can be expressed as the sum of positive sequence voltage, negative sequence voltage and zero sequence voltage. When the power network is unbalanced, because of the existence of the negative sequence voltage, it will lead to the deviation of the power grid angle acquisition, the asymmetrical operation of the AC side current, and the DC bus voltage jitter. In order to control the positive and negative sequence current separately, it is necessary to separate the voltage and current in a positive and negative sequence. In this paper, the delay method, notch filter method and low pass filter method are introduced. When the power network is unbalanced, the system will produce negative sequence current due to the influence of negative sequence voltage, and the product of negative sequence current and positive sequence switching function will make the output DC voltage produce harmonics. According to the different requirements of stable DC bus and input three-phase current symmetrical operation, a voltage unbalanced control strategy with power balance and a voltage unbalanced control strategy with current symmetry are proposed. The voltage imbalance control strategy of current symmetry is realized under the two phase positive synchronous reference coordinates. By adding the voltage vector of the AC side of the rectifier bridge to the negative sequence voltage compensation, the negative sequence current is zero, and the purpose of current symmetry operation can be achieved. If the output DC bus voltage is stable and the input power is invariant under the condition of constant load the negative sequence current is required on the input side. According to this principle, the internal model controller method in two phase static reference coordinates and the four closed loop control method in two phase synchronous reference coordinates are proposed. The four closed loop control method is based on the double closed loop, and the negative sequence component is added to the double closed loop. The control effect is good. The internal model controller method of two phase static reference coordinates is used to control the negative sequence component of the positive sequence component with the same channel. The control structure of the system is simpler than that of the four closed loop system. On the basis of the existing experimental platform, a simple three-phase unbalanced voltage is constructed by using a contact voltage regulator, and the correctness of the symmetrical current control strategy is verified by experiments.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM461

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