南京航空航天大学博士学位论文
摘要
为了适应对称或非对称负载、线性或非线性负载的要求,三相逆变器可以采用四
个桥臂的形式实现三相四线制输出。
本文建立了四桥臂三相逆变器的数学模型,由数学模型可以得到四桥臂三相逆变
器中输出电压和电感电流等各个变量之间的关系,从而实现对输出电压的控制。
PWM控制是逆变器中应用最广的一种方法,本文对PWM调制技术进行了介绍,
分析了三桥臂三相逆变器和四桥臂三相逆变器的调制信号的特点;分析了三次谐波注
入的PWM控制
方案,其本质是改变了输出中点电压,提高了
系统的电压利用率;分
析了基于输出电压反馈的控制系统的性能,进行了系统仿真,得到了控制系统的调节
参数;本文将三次谐波注入的PWM控制方案应用到四桥臂三相逆变器中,可以带非
对称负载且具有较高的电压利用率。
SVM控制也可以应用到四桥臂三相逆变器中。本文提出了一种四桥臂三相逆变
器的二维S VM控制方案,具体的做法是,四桥臂三相逆变器中的前三个桥臂由二维
SVM控制得到导
通信号,同时,根据四桥臂三相逆变器与三桥臂三相逆变器的输出
中点电压在一个开关周期的平均值相等的原则,得到第四个桥臂的导通信号。
一些三相逆变器的控制结构中包含电流内环,电流控制器与变换器的性能密切相
关,电流控制器可以使得负载电流跟踪给定电流信号。通过比较实际电流和给定电流,
电流控制器发出开关信号以减小电流误差,因此,电流控制器起到抑制误差和调制的
作用。本文详细研究了电流内环的特性,提出了两种应用于四桥臂三相逆变器的电流
控制方案,它们在传统三桥臂逆变器的电流控制的基础上加入了对第四桥臂的控制,
通过电流控制,可以获得很多优良的性能,如:高精度、电流保护、快速响应能力等。
关键词:三桥臂;四桥臂;三相逆变器;脉宽调制;空间矢量调制;电流控制
四桥臂三相逆变器的控制和实现
Abstract
The three-phase four-wire inverter with four legs can deal with an arbitrary load:
unbalanced and/or balanced load; linear and/or nonlinear load.
Mathematics model of four-leg three-phase inverter is the base of theoretic analysis,
the relationship between variables, such as output voltage and inductance current, can be
established by the model.
The pulse-width modulation (PWM) is introduced since it is the most widely used
method. The characteristics of the modulation signals in three-leg, three-phase inverter and
four-leg three-phase inverter are analyzed. In order to get a high utilization of do bus
voltage, the distorted modulation waveforms can be used, such waveforms contain 3-th
harmonic in addition to the fundamental and can chance the neutral point voltage of the
output. The performance of the output voltage feedback control system is analyzed, the
parameters of the controller can be gained by computer simulation. The PWM control
stratecy with 3-th harmonic in addition is presented for four-leg three-phase inverter, the
inverter can deal with unbalanced load and has a high utilization of do bus voltage.
Space-vector modulation (SVM) techniques can be used in four-leg, three-phase
inverter. The two-dimensional SVM control stratecy can still be available in four-lec, three
phase inverter, the first three le-s can be controlled by c