【作者】 要焰梅；

【导师】 徐永向；

【作者基本信息】 哈尔滨工业大学 ， 电气工程， 2011， 硕士

【摘要】 在永磁同步电机驱动系统中,传统的逆变器采用固定开关频率调制方式,使得电机的噪音频谱中含有集中在开关频率及其整数倍处的谐波含量,这种噪音会给人带来不愉悦的感觉,甚至对人类的健康造成一定损害。虽然可通过采用较高的开关频率使噪音的功率谱密度较大的点出现在人类听力范围之外,但会使得逆变器损耗增加。因此,基于扩频原理的开关噪音抑制技术成为了人们研究的热点。本文针对这一问题,对周期频率调制和随机频率调制的扩频策略进行了深入研究。首先,在分析固定开关频率SVPWM原理及其在数字控制系统中的具体实现方式的基础上,对固定开关频率下的输出信号进行了谐波分析,得到了其频谱分布规律。通过在Simulink中进行的仿真分析,以及基于DSP的永磁同步电机驱动系统的实验研究,对理论分析进行了验证。其次,对三角波、锯齿波和正弦波这三种周期开关频率调制技术用于永同步电机系统开关噪音的抑制进行了深入研究。为了探究电周期和调制周期比值对降噪效果的影响,对5种周期比值情况作了仿真和实验研究,结果表明二者的比值越大,扩频效果越好。此外,还分析了调制函数与线电压基波相位对扩频效果的影响。对三种方式的仿真和实验研究表明,周期频率调制确实能够行之有效地将频谱能量扩展到更宽的范围内。再次,鉴于周期频率调制下信号频谱中的不连续性和带状分布性,本文将随机频率调制技术应用于永磁同步电机驱动系统中。在随机频率调制中,为了确保随机数具有较好的分布特性,本文采用了生成随机数性能较好的Mersenne Twister发生器法。仿真和实验结果都表明,与三种周期频率相比,随机频率调制能够取得最好的扩频效果。最后,针对频率调制技术使得逆变器输出电压和电流中谐波含量复杂,会引起转子的高频涡流损耗及逆变器损耗等性能的变化,本文采用有限元法计算了不同频率下的转子涡流损耗,然后对不同频率调制方式下转子涡流损耗和逆变器损耗进行了计算和对比分析。计算结果表明,采用周期频率调制和随机频率调制后,转子的涡流损耗会增大,而逆变器损耗的基本相同。更多还原

【Abstract】 In the conventional PMSM (permanent-magnet synchronism motor) drive systems, the fixed switching frequency in inverters introduces massive harmonics highly concentrated near switching frequency and its multiples to the acoustic noise spectrum, which causes annoying acoustic noise, even doing harms to human’s health especially the motor operators. Although the noise could be reduced by applying comparatively higher switching frequency out of human’s listening, switching loss of power electronics will become significant. Thus, noise reduction technique based on spread spectrum has drawn more and more attention. In this paper, periodic and random frequency modulation were investigated to explore their effects in terms of spectrum spreading and noise reduction.Firstly, based on the analysis about the principle of fixed frequency SVPWM(Space Vector Pulse Width Modulation), as well as its implementation in the digital control system, the output signals of the inverter under fixed switching frequency were analyzed, with the spectral distribution obtained. Moreover, simulation results by Simulink and experimental results in the DSP based plat verified the theory.Secondly, three periodic frequency modulation patterns, including the triangular, sawtooth and sinusoidal frequency modulation, were proposed to spread the spectrum of switching noise existing in PMSM system under fixed switching frequency modulation. In order to investigate the noise reduction and spectrum spreading effects under different ratios of electrical period and modulation period, we simulated and experimented under 5 ratios, whose results revealed that the bigger the ratio, the better the effects. Additionally, spectrum spreading effect under different phase angulars between switching frequency function and line voltage with the same periodic ratio were also researched. Simulation and experiment results illuminated that periodic frequency modulation could spread the harmonic energy to wider frequency ranges effectively with similar distribution under three patterns with just some differences in continuity.Besides, the spectrum under periodic frequency modulation is not as continuous as we expected, so we did some research on the random frequency modulation. In order to get the random numbers with good distribution performance, Mersenne Twister generators were used. And the final simulation and experimental results told that the random frequency modulation had the best effect compared with three periodic frequency modulation patterns mentioned before.Finally, the utilization of frequency modulation technique makes the harmonic components of output voltage and current of the inverter complex, which will cause the variation of rotor high frequency eddy current loss and inverter loss. Thus, rotor eddy current loss was calculated under different frequencies using finite element method, and than the eddy current loss and inverter loss under different frequency modulation patterns were calculated and compared in this paper. Calculation results indicated that the eddy current loss is higher under both the periodic and random frequency modulation compared with fixed frequency modulation. While, the loss of the inverters keeps almost the same.更多还原