Abstract

An analysis of methods for controlling the current of an asynchronous electric motor in a frequency-controlled electric drive is performed. The disadvantages of a control system with relay current controllers that provide system operation in the “current corridor” mode are shown. Such disadvantages as increased thermal losses in the transistors of the frequency converter are caused by the unstable switching frequency of the motor current. The relevance of the principles of current control using the predictive model to form control actions in the frequency converter circuit with relay controllers is noted. A method of current control in an asynchronous electric drive is considered that makes it possible to stabilize the switching period of the inverter power switches when controlling the current in the motor. To obtain this result, it is proposed to influence the width of the hysteresis loop of the relay current controllers and form it depending on the parameters of the load circuit. The required accuracy of the current control is maintained. The structure of the control system is proposed, in which the considered method is implemented. A key element of the system is a computing unit that generates signals that set the required width of the hysteresis loop of the relay controllers. The method of predicting changes in the controlled current after the next switching of transistors in the inverter of the frequency converter of the electric drive is the analytical basis of the calculations. Analytical expressions providing the calculations necessary for the computing unit operation are presented. The effect of applying the relay current controllers with variable hysteresis in the control system of a frequency-controlled electric drive is shown.

中文翻译：

---

变频电驱动中感应电动机电流的有效控制

摘要

进行了用于控制频率控制电驱动器中的异步电动机的电流的方法的分析。显示了带有继电器电流控制器的控制系统的缺点，该继电器电流控制器以“电流通道”模式提供系统操作。电动机电流的不稳定开关频率会导致诸如变频器的晶体管中的热损耗增加等缺点。指出了使用预测模型在带有继电器控制器的变频器电路中形成控制动作的电流控制原理的相关性。考虑了一种异步电驱动中的电流控制方法，该方法可以在控制电动机中的电流时稳定逆变器电源开关的开关周期。为了获得这个结果，建议影响继电器电流控制器的磁滞回线的宽度，并根据负载电路的参数来形成它。保持了所需的电流控制精度。提出了控制系统的结构，其中实现了所考虑的方法。该系统的关键要素是一个计算单元，该计算单元生成设置继电器控制器的磁滞回线所需宽度的信号。在电驱动的变频器的逆变器的下一次晶体管开关之后，预测受控电流变化的方法是计算的分析基础。给出了提供计算单元操作所需的计算的分析表达式。