![]() The most important of the estimates is the assessment of sustainability which is made by sufficiently accurate, for example, criteria Nyquist. LSS equations have strict solutions, the qualities of which - stability, static and dynamic errors and the time of transient processes do not depend on the “right” part of the equations, which, as a rule, describe external perturbations or job signals. For such systems, you can highlight a number of important features: At the same time, strict solutions exist only in the area of linear stationary systems (LSS), which are described by linear differential equations with constant coefficients in the “left” part of the equations-the one that describes the control object itself-in our case, the electric drive. Reality is more complicated than any mathematical model. Everything is complicated by the fact that both linear and nonlinear equations of electromechanical complexes are only an approximation to real technical systems.ġ.2 About mathematical models and linear stationary systems At present, the following situation is “generally accepted”: scalar control preserves the nonlinearity of the AED, but is not intended for dynamic mechanisms and does not require dynamic analysis, and vector control reduces the AED to a DC drive therefore, complex nonlinear methods are not applied to anything. It turned out that AEDs are a substantially nonlinear link and the existing control methods (scalar control (SC), space vector control (SVC)) do not remedy this situation too much. ![]() The use of AED with frequency converters in a wide practice has encountered a number of problems. Developed in the 1970s, the principles of “transvector” control were immediately recognized as “reducing” the AED to a DC drive, that is, practically to a linear stationary system. The principles of frequency control were developed at the beginning of the twentieth century, but not having a wide practical application, they largely remained a theory. ![]() Only in the 1980s of the twentieth century, that is, 100 years after the invention, with the start of production of powerful controlled semiconductor switches, it became possible to effectively control the stator frequency and, along with it, almost any AED coordinates. At the same time, for more than 100 years, they have been used in mechanisms with virtually no control over the speed of rotation or the mechanical moment developed. Invented more than 150 years ago, they very quickly became integral elements in all technical systems due to their manufacturability, low price, good weight, and size characteristics. The use of dynamic feedback on the stator current allowed to significantly increase the dynamics and efficiency of a more stable scalar control.Īsynchronous electric motors (AEM) are the most common electromechanical converters in the industry. For identification of nonlinearities, dynamic formulas of transfer functions of torque generator in VFD are proposed, taking into account slip and stator voltage frequency The nonlinear transfer functions obtained in this work made it possible to substantiate structural solutions that linearize the VFD and substantially increase their efficiency. Comparative results of the analysis of dynamic of VFD with two types of sensorless control, vector and scalar, show the problems that these assumptions lead to. ![]() Therefore, the equations of the mathematical model on which the vector control system is based are compiled with the assumption of the sinusoidality of the processes occurring in the control object. Accounting for these nonlinearities leads to equations that are very problematic to solve. Such objects are characterized by dynamic nonlinearities that are difficult to take into account in the mathematical description for the development of control algorithms. A light rope is attached to it and runs over a pulley.The results of theoretical and practical research studies most widely used in the industry of variable frequency drives (VFD) are presented in this manuscript. \): Block on the Table (Coupled Blocks)Ī block rests on the table, as shown.
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