三相电压型PWM整流器在电网不平衡下的控制策略的研究

发布时间：2018-06-13 22:26

本文选题：电压型PWM整流器 + 直接功率控制　；参考：《东北大学》2014年硕士论文

【摘要】：传统的整流器广泛采用的二极管整流电路和晶闸管相控整流电路,会给电网注入大量谐波,给电网造成污染。三相电压型PWM整流器具有输出电压恒定、能实现单位功率因数运行的特点,甚至可以实现电能回馈电网。电网不平衡情况下,基于电网平衡下设计的PWM整流器的控制策略将会出现不正常的运行状态,主要表现在交流侧会出现负序分量,导致交流电流不对称,出现非特征谐波,使电流总畸变率增加；另外直流侧也会出现谐波,使电压电流波形发生畸变。因此,对于电网不平衡情况下的PWM整流器的控制策略的研究非常有必要性。本文首先对PWM整流器的原理做了详细的介绍,主要是拓补结构,工作原理,分别在ABC静止坐标系、αβ静止坐标系和dq旋转坐标系中建立了开关周期平均模型和等效电路。选择了电压型的三相PWM整流器作为本文主要研究对象,并在坐标系中对其数学模型进行解耦。PWM整流器的电流控制技术是最早出现的控制方法,本文研究了间接和直接电流控制,并在直接电流控制中,引入了空间电压矢量定向控制,给出了实现该控制策略的主要算法,并建立了仿真模型。直接功率控制是近来发展起来的三相PWM整流器控制技术,本文在详细介绍了传统的直接功率控制策略后,针对其存在的问题,引用了电压定向直接功率控制策略和开关表的改进,利用了三状态开关信号的控制策略对传统直接功率控制策略进行了改进,并通过仿真验证了控制策略的有效性。在三相电网不平衡的条件下,分析了两种不平衡控制策略,其一是传统的双电流控制策略,主要是在正序、负序同步旋转坐标系中进行控制；其二是恒频直接功率控制。同时,还研究了两种电网电压正负序分量的提取方法,即二次谐波滤除法和信号延迟法,并对两种方法进行了比较。最后,在以上理论研究的基础上,本文最后对电网电压平衡和不平衡时的控制策略进行了较为详细的仿真研究。
[Abstract]:Traditional rectifier widely used diode rectifier circuit and thyristor phase-controlled rectifier circuit will inject a large number of harmonics into the power grid and cause pollution to the power network. Three-phase voltage source PWM rectifier has the characteristics of constant output voltage, can realize unit power factor operation, and can even realize power feedback to the power grid. Under the condition of unbalanced power network, the control strategy of PWM rectifier designed under the condition of power grid balance will appear abnormal operation state, mainly in the negative sequence component of AC side, resulting in asymmetry of AC current and non-characteristic harmonics. The total distortion rate of the current is increased, and harmonics also occur at the DC side, which makes the voltage and current waveforms distorted. Therefore, it is necessary to study the control strategy of PWM rectifier under unbalanced power grid. In this paper, the principle of PWM rectifier is introduced in detail. The principle of PWM rectifier is introduced in detail. The switching cycle average model and equivalent circuit are established in ABC stationary coordinate system, 伪尾 stationary coordinate system and DQ rotation coordinate system respectively. The three-phase PWM rectifier with voltage source is chosen as the main research object in this paper, and the current control technology of decoupling the mathematical model of PWM rectifier in coordinate system is the first one. The indirect and direct current control is studied in this paper. In the direct current control, the space voltage vector oriented control is introduced, the main algorithm to realize the control strategy is given, and the simulation model is established. Direct power control is a recently developed three-phase PWM rectifier control technology. The improvement of voltage oriented direct power control strategy and switching table is introduced. The traditional direct power control strategy is improved by using the control strategy of three-state switching signal. The effectiveness of the control strategy is verified by simulation. Under the condition of unbalance of three-phase power network, two kinds of unbalanced control strategies are analyzed. One is the traditional double-current control strategy, which is mainly controlled in the positive sequence, negative sequence synchronous rotating coordinate system, and the other is the constant frequency direct power control. At the same time, two methods of extracting the positive and negative sequence components of power network voltage, namely, the second harmonic filtering method and the signal delay method, are studied and compared. Finally, on the basis of the above theoretical research, the control strategy of the voltage balance and unbalance of the power network is simulated in detail in this paper.
【学位授予单位】：东北大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM461

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