三电平牵引逆变器优化脉宽调制与中点电位平衡控制算法

发布时间：2018-05-05 03:16

本文选题：三电平牵引逆变器 + SVPWM　；参考：《西南交通大学》2017年硕士论文

【摘要】：二极管箱位型(neutral-point-clamped,NPC)三电平逆变器自1981年首次提出应用于交流传动系统以来,已成为中压大功率传动领域广泛应用的多电平逆变器。由于开关损耗、逆变器体积及散热能力等限制,现有功率器件最高开关频率一般不超过1kHz,为降低电机在宽速度范围内运行时的定子电流畸变、谐波转矩、谐波损耗、发热和噪声等,通常在不同速度区段采取不同的调制算法即多模式调制。如何在有限的载波比下,设计出电流谐波畸变和转矩脉动最低的三电平牵引逆变器优化脉宽调制算法,具有重要的理论和工程应用价值。因此,本文主要对不同类型、不同载波比下的脉宽调制算法及其谐波性能、中点电位平衡控制算法进行了研究。首先简要介绍了三电平牵引逆变器的主电路结构及其工作原理;分析了三电平异步空间矢量脉宽调制(space vector pulse width modulation,SVPWM)算法基本原理,以及基于60°坐标系计算矢量作用时间的异步SVPWM简化算法,.通过仿真对比分析了采用不同合成矢量序列的两种异步SVPWM简化算法的谐波性能。其次,介绍了三电平同步PWM的基本原理;针对基于空间电压矢量在线计算矢量作用角度的同步PWM,为消除偶数次谐波分量,设计了 8种满足半波对称、三相对称、考虑1/4周期对称约束的三矢量同步SVPWM;为进一步降低线电压的加权总谐波畸变率,分析并设计了 3种考虑矢量分配系数影响的四矢量同步SVPWM,得到特定矢量序列中矢量分配系数与谐波性能间的定量关系;针对基于单相桥臂电压波形离线计算开关角的优化同步PWM,根据优化目标的不同,分别对特定次谐波消除PWM、电流谐波最小PWM、转矩谐波最小PWM建立优化数学模型,结合初值经验公式和解轨迹微分预估初值的方法,完成不同载波比下各优化同步PWM的优化开关角求解,并对电流谐波性能进行了理论对比分析;针对如何设计三电平牵引逆变器全速域脉宽调制技术的问题,分别从载波比个数、最高开关频率、电流谐波畸变率、转矩脉动、DSP数字化实现等方面对比分析了上述两类同步PWM算法;最后通过仿真验证了各同步PWM的有效性,并对比分析了各同步PWM的谐波性能。再次,针对三电平牵引逆变器的中点电位不平衡问题,提出一种基于SHEPWM的中点电位平衡三级滞环控制方法,通过分析三相桥臂电压波形对应的开关矢量序列及其作用角度,设计了三种冗余矢量调整方案;该方法直接对三相PWM信号进行在线调整,适用于任何PWM算法;最后通过仿真验证了该中点电位平衡控制算法在两种异步SVPWM和两类同步PWM下,均能够实现对中点电位的有效控制。最后,基于TMS320F28335控制器和RT-LAB硬件在环实时仿真平台,完成三电平逆变器优化脉宽调制与中点电位平衡滞环控制算法的DSP程序开发,以及算法正确性和有效性的验证。
[Abstract]:Since its first application in AC transmission system in 1981, the three-level diode box type neutral point-clamped NPC inverter has become a widely used multilevel inverter in the field of medium-voltage and high-power transmission. Due to the limitation of switching loss, inverter volume and heat dissipation, the maximum switching frequency of existing power devices is generally not more than 1 kHz. In order to reduce the stator current distortion, harmonic torque and harmonic loss when the motor is running in a wide speed range, Heat and noise, usually adopt different modulation algorithm in different speed range, that is, multi-mode modulation. How to design the optimal pulse width modulation algorithm of three-level traction inverter with the lowest current harmonic distortion and torque ripple under the limited carrier ratio has important theoretical and engineering application value. Therefore, this paper mainly studies the pulse width modulation algorithm with different carrier ratio and its harmonic performance, as well as the midpoint potential balance control algorithm. Firstly, the main circuit structure and working principle of three-level traction inverter are introduced briefly, and the basic principle of three-level asynchronous space vector pulse width modulation (vector pulse width) algorithm is analyzed. And the simplified asynchronous SVPWM algorithm based on 60 掳coordinate system to calculate vector action time. The harmonic performance of two asynchronous SVPWM simplification algorithms using different synthetic vector sequences is analyzed by simulation. Secondly, this paper introduces the basic principle of three-level synchronous PWM, aiming at the synchronous PWM based on space voltage vector on-line calculating vector action angle, in order to eliminate even harmonic components, eight kinds of synchronous PWM are designed to satisfy half-wave symmetry and three-phase symmetry. In order to further reduce the weighted total harmonic distortion rate of line voltage, a three-vector synchronous SVPWM with 1 / 4 periodic symmetry constraint is considered. Three kinds of four vector synchronous SVPWMs considering the influence of vector assignment coefficient are analyzed and designed, and the quantitative relationship between vector assignment coefficient and harmonic performance in a particular vector sequence is obtained. Aiming at the optimal synchronous PWM based on off-line calculation of the switching angle based on the voltage waveform of the single-phase bridge arm, according to the different optimization objectives, the optimal mathematical models are established for the special harmonic elimination, current harmonic minimization and torque harmonic minimization PWM, respectively. Combined with the method of initial value empirical formula and trajectory differential estimation, the optimal switching angle of each optimized synchronous PWM under different carrier ratio is solved, and the harmonic performance of current is compared and analyzed theoretically. In order to solve the problem of how to design three-level traction inverter pulse width modulation technology in full speed domain, the number of carrier ratio, the highest switching frequency, the harmonic distortion rate of current, The digital realization of torque ripple DSP and so on are compared and analyzed. Finally, the effectiveness of each synchronous PWM is verified by simulation, and the harmonic performance of each synchronous PWM is compared and analyzed. Thirdly, aiming at the unbalanced neutral point potential of three-level traction inverter, a three-stage hysteresis control method of neutral point potential balance based on SHEPWM is proposed. The switching vector sequence corresponding to the voltage waveform of three-phase bridge arm and its action angle are analyzed. Three redundant vector adjustment schemes are designed, which can directly adjust the three-phase PWM signal online and can be applied to any PWM algorithm. Finally, the simulation results show that the proposed midpoint potential balance control algorithm is based on two asynchronous SVPWM and two classes of synchronous PWM. All of them can effectively control the midpoint potential. Finally, based on the real-time simulation platform of TMS320F28335 controller and RT-LAB hardware in loop, the DSP program of optimized pulse width modulation and neutral point potential balance hysteresis control algorithm for three-level inverter is developed, and the correctness and validity of the algorithm are verified.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464

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