【作者】 李祥生；

【导师】 邓智泉；

【作者基本信息】 南京航空航天大学 ， 电机与电器， 2010， 博士

【摘要】 为降低开关功放的成本以利于磁轴承的推广应用,本文分别采用三相四桥臂和五相六桥臂结构作为磁轴承开关功放的主电路,这两种多桥臂开关功放可分别用来驱动磁轴承三个和五个自由度的绕组,所需功率管的总数比传统的全桥功放分别减少1/3和2/5。这不仅减小功放的体积,同时节省了控制器的I/O口资源。本文将两种多桥臂开关功放的电流控制策略作为研究的重点,主要研究电流谐波含量低、动态性能好、负载适应能力强的控制方法,并解决由于多路负载连接于公共桥臂而引起的各相电流间的干扰问题。研究了一种基于电流PID调节的四桥臂开关功放节点电位控制法,可由各桥臂节点的电位直接获得各开关信号的占空比。该方法计算量小,易于数字实现,并具有三态开关功放电流纹波小且不受母线电压影响的优点。总结出三种典型的电位分配方式,分析了不同的分配方式对输出电流的纹波大小和总开关次数的影响,定性地分析了缓冲电路对死区时间的补偿作用,针对功放的特点又提出了解决四桥臂开关功放输出电流间干扰的过调制处理方法。该控制方法可以推广到具有公共桥臂的任意n桥臂功率变换器的控制当中。为比较节点电位法与三维空间矢量控制(SVPWM)的性能,本文对后者的实现方法进行简化。从计算机图形学的角度分析了abc和αβ0坐标系下电压矢量分布图之间的异同点,推导出三个基本电压矢量的作用时间与三相电压之间的关系,最后推导出各桥臂开关管的导通时间在24个四面体中的统一计算公式,证明了这两种方法的等效性。简化了现有各种断续脉宽调制(DPWM)的实现方法,并提出了两种三维SVPWM中特有的DPWM方式。为了解决节点电位控制中的输出电流间的干扰问题,需要研究四桥臂功率变换器的过调制控制方法。研究了三维SVPWM中的过调制问题,通过提取电压零轴分量将其转为二维SVPWM过调制问题以简化研究。提出了无需查表的单模式和双模式二维SVPWM过调制的无扇区算法,使得三维SVPWM过调制可由简化的SVPWM算法来实现。PID控制中输出电流的纹波较小,但是电流的幅值和相位存在误差且随频率升高而逐渐增加,在负载变化后各控制参数需重新调整,其带载能力较弱。本文研究了一种混合电流控制方法以提高四桥臂开关功放的性能。将全桥功放中的采样保持控制引入到各相桥臂的控制当中,并可根据电流误差连续调节公共桥臂的占空比,仿真结果表明该混合控制方法电流失真较小,具有较强的负载适应能力,且输出电流和给定信号之间无幅值和相位误差。比较和分析了多种控制方法在六桥臂开关功放中的性能,提出一种最大电流误差优先的采样保持控制方法,通过改进公共桥臂的控制策略,使五路电流的误差在每个控制周期都能得到调节。该方法具有与上述混合控制相似的性能,两者输出电流的谐波分布基本相同。在以DSP和CPLD为核心的两种多桥臂开关功放样机上进行了实验,验证了本文研究的电流控制方法的有效性。本文的工作对电机驱动中多相逆变器的控制研究具有一定的借鉴意义。更多还原

【Abstract】 In order to popularize the active magnetic bearings (AMB), low costs power amplifier is needed. This paper studied on the four-leg and six-leg switching power amplifiers, which could respectively drive three and five coils of the AMB. The amounts of the switches in two multi-bridge amplifiers were respectively reduced 1/3 and 2/5 comparing with H-bridge power amplifiers. The complexity of the power amplifier is reduced, and the I/O source in the controller is saved. The objective of this paper was to research the current methods with low total harmonic distortion (THD), high stability and strong adaptability to loads, and to resolve the interaction of the output currents for all loads were connected with the neutral leg.A node potential control method in four-leg power amplifier based on current PID regulating, which has the merits of three-state power amplifiers, was presented. It needs little algebraic operation, so it is easy to be implemented for the duty cycle of each bridge can be obtained directly from each potential. Three typical methods of distribution of the potential were summarized and their influence on current ripple and switch times were compared, the dead-time compensation of the snubber circuit was analyzed. A over-modulation algorithm was proposed and it eliminated the phase interference in the four-leg power amplifier. This method can be extended to control arbitrary n-bridge converter.The three-dimensional (3-D) space vector pulse width modulation (SVPWM) was simplified and its performance was compared with the node potential control method. The relationships, whether in abc orαβ0 coordinates, between three-phase voltages and the following elements: the tetrahedron in which the reference vector resides, three adjacent active switching vectors (or three switching states) and their duration times, were analyzed. Based on the analysis, the calculation of turn-on time of each switch in the actual implementation was simplified, and it was the same with the node potential control method. The implementation of common discontinuous PWM (DPWM) methods in existence were also simplified. In addition, two more DPWM methods peculiar to 3-D SVPWM were presented.The over-modulation was researched to resolve the phase interference in the four-leg amplifier. Over-modulation of 3-D SVPWM was changed into 2-D problem by separating the zero components from three-phase voltages. Two simple algorithms of single-mode and two-mode over-modulations in 2-D SVPWM were presented, and it is no need to identify the sector in which the voltage vector locates or to lookup tables. That makes the 3-D over-modulation can be implemented by the simplified SVPWM algorithm. A hybrid control method for four-leg amplifier was studied to overcoming the shortcomings in PID control. In this method, the neutral leg, which duty cycle is continuously adjusted, is controlled separately from other legs according to three current errors and three phase bridges are controlled by sample-hold control used in H-bridge amplifier to enhance dynamic performance and to enlarge the load range.The performances of various current control methods for six-leg power amplifier were compared. A maximum current error preferred sample-hold control method was proposed. Five currents all can be regulated in one sampling period by modified control method of the neutral leg. This method and the hybrid current control mentioned above were similar in the performance and spectrum of the output currents.The experiments were carried out with two multi-leg amplifiers using DSP and CPLD as the core controller and the experimental results verified the feasibility and effectiveness of these current control methods. The study of this paper has significance for reference in controlling the multi-leg inverters for multi-phase motors.更多还原