方波电压法测量液体介质低tanδ值的原理和技术关键(续)

介绍了方波电压法测量液体介质 tanδ的原理。分析了实现这一测量方法的技术关键。在测量系统的趋稳时间、测量时间的控制、测量系统各参数的设置和电流测量仪器选用等方面 ,提出了通过实践验证的计算方法和解决方案 ,并证实该方法是测量液体介质低 tanδ值 。

基于SOGI高频方波电压注入的永磁直线同步电机无感控制

针对永磁直线同步电机的无感控制技术,为了解决传统高频方波注入法无法准确定位转子位置和转速的问题,提出了基于SOGI高频方波电压注入的无感方法。与传统的高频方波电压注入法不同,为了得到更好的高频电流信号,采用二阶广义积分器提取响应高频电流信号,采用正交锁相环解决反正切函数没有反馈直接放大噪声的影响。为证明无感控制技术的有效性,用Simulink进行了仿真验证。结果表明,基于SOGI高频方波电压注入的无感方法大大降低了误差,缩短了调节时间,提升了响应时间。

基于高频方波电压注入法和改进龙伯格观测器的永磁同步电机转速估计的研究

针对传统矢量控制方法难以获得精确的转子位置和转速的问题,提出一种基于高频方波注入法和改进龙伯格观测器的永磁同步电机的转速研究方法。因高阶系统稳定性较差,微机控制难度较高,并且由于高阶的传递函数中参数对电机参数和控制器参数的依赖性较大,因此很难对于永磁同步电机具有通用的控制性能。为解决上述问题,将龙伯格观测器中的电磁转矩前馈项替换为一个由速度指令组成的二阶系统,并用最小二乘法得到该二阶系统。仿真结果表明,改进方案在负载扰动下具有更好的跟踪精度和鲁棒性。

基于高频正交方波电压注入的永磁同步电机初始位置辨识

传统高频方波电压注入法辨识内置式永磁同步电机的转子初始位置时,存在多个零点,闭环调节收敛时间长,无法准确辨识磁极极性等问题,导致电机起动失败甚至反转。为此,提出一种基于高频正交方波电压注入的转子初始位置辨识方法。该方法将正交方波信号注入静止坐标轴,利用其高频响应电流辨识转子磁极位置后,再通过在直轴注入低频正弦电流信号辨识磁极极性。该方法的磁极位置信号不需要通过闭环调节获得,可直接通过求反正切获取,响应快,工程实现容易。最后在 1.5kW IPMSM 驱动系统上进行实验,实验结果表明本文所提出方法准确且有效。

Dynamic anti-plane characteristic on an infinite piezoelectric medium with a movable rigid cylindrical inclusion

Scattering and dynamic stress concentrations of time harmonic SH-wave in an infinite elastic piezoelectric medium with a movable rigid cylindrical inclusion are studied in this paper with the help of complex variable and wave function expansion method. The relations that a movable rigid cylindrical inclusion depends on intensity of incident wave and electric field are revealed. The expressions of dynamic stress at the edge of the inclusion are obtained. Numerical calculations are made with different wave numbers and different piezoelectric characteristic parameters. The calculating results show that dynamic stress concentrations at the edge of the inclusion have linear dependence on the incident electric field. And dynamic analyses are very important for an infinite piezoelectric medium with a movable rigid cylindrical inclusion at larger piezoelectric characteristic parameters.

Methodology Approach Using Harmonic Synthesis as Simulation Method for Investigation of Power Network with Non-Linear Loads

The paper deals with analysis and synthesis of non-harmonic and non-linear sources and appliances, and their interaction with harmonic power supply network. Basic idea is based on knowledge of harmonic spectrum of the sources and/or appliances, respectively. Obviously, one need to know voltage harmonic components of voltage sources （renewable with inverters,...）, and current harmonic components generated by non-linear appliances （rectifiers,...）. Method of investigation lies on decomposition of real electric circuit into n-harmonic separated equivalent schemes for each harmonic component. Then transient analysis will be done for each scheme separately using ＂impedance harmonic matrices＂. The important fact is that each equivalent scheme is now linearized and therefore easily calculated. Finally, the effects of each investigated schemes arc summed into resulting quantities of real non-linear electric circuit.