FC manufacturers use standard control algorithms, such as scalar (with various types of correction), current vector control, voltage vector control, and both open (sensorless) systems and closed systems with speed loop, flow loop, etc. Furthermore, Siemens and ABB companies use direct torque control (DTC) [11]. More complex algorithms can be used, adapted to the specific applications in small series and specialised FCs. Complex observers are developed to measure a number of parameters required to ensure their operability, introducing additional errors into the sensorless control systems. There is a practice of construction of multiloop control systems, significantly improving the characteristics of IMs. However, it also has a number of problems, for example, building dual-circuit systems with a current loop requires additional sensors to be installed on the motor, or, also, building quite complex observers. The construction of multi-circuit systems with serial FCs is not always possible due to the lack of appropriate functions in the software of such frequency converters and the inability to change their software [12]. Specialized and small-scale FCs have a high price, and are not universal (most often they are designed for use only on specific objects). FCs requires additional sensors to be installed on the motor or on the process unit. These disadvantages nullify the main advantages of using asynchronous motors--low price, reliability, low maintenance costs [13]. Vector control represents a method for how to control a variable frequency drive where the stator currents of a three-phase IM are conceptualized in the form of two orthogonal components that can be visualized as vectors, where the first component identifies the magnetic flux of the motor, while the other component identifies the torque. The IM control system calculates the appropriate current component assignments based on the magnetic flux and torque assignments specified by the system controlling the drive speed. In most cases, the usage of the proportional-integral (PI) controllers is to maintain the measured components of current on their reference values. In this way, the pulse-width modulation of the variable frequency drive controls the transistors switching as determined by the given stator voltages, which are the outputs of the PI current controllers [14]. Vector control is suitable for controlling synchronous or IMs [15]. Initially, it was established for high-performance motors which are required to operate smoothly over the whole range of speeds and provide full torque also at zero speed. That also includes high dynamic performance such as rapid acceleration and deceleration. Thus, vector control is increasingly demanded in various fields of the industry, as IMs provide important advantages in comparison with DC motors. Thanks to the increasing computing performance of the control electronics, vector control is expected to eventually supplant scalar control in most applications [16]. Vector control allows that IMs or synchronous motors can be driven for all operating conditions, similar to DC motors [17]. That means the AC motor functions in the same way as a DC motor where the magnetic field coupling and the armature flux coupling produced by the corresponding field and armature current (or torque component) are orthogonally directed. When torque is controlled, the flux coupling is not affected by the field, and thus the dynamic torque response is provided [18]. Vector control respectively generates the output voltage of the three-phase PWM motor originating from the complex voltage vector utilised to operate the complex current vector that is obtained from the input three-phase motor stator current by utilizing the projections or backward and forward rotations between the three-phase system, dependent on the time and speed into a two-coordinate time-dependent rotating reference system appropriate for these vectors description [19].