Modern microprocessors used for process control enable fast real-time computation. Therefore, an application of predictive methods in modulation and control in power electronics (active power filters, electrical drives), is possible. The predictivity shows itself in anticipation of output variables (currents or voltages) at the end of sampling interval, the latter being in order of some tens of microseconds. The submitter of the project proposal and his team have developed an original method for predictive control that enables complete monitoring over inverters' variables. Depending on the specific application, the methods have been named direct current control (DCC), immediate flux control (IFC) and predictive torque control (PTC). The main advantage of these approaches is complete control over variables at considerably reduced switching losses and exceptional dynamics compared to the traditional approaches. The algorithms have been tested on various heterogeneous final applications (active power filters, synchronous and induction motor drives), which indicates the versatility of the method while conserving the above mentioned advantages.
COBISS.SI-ID: 7112020
In recent years, fault diagnosis of electrical machines during their operation in a plant has gained a noticeable momentum. Its goal is to detect various types of faults at an early stage, thus preventing radical breakdown and enabling planning of a repair. In most cases, contemporary methods require expensive equipment and complicated procedures for detecting the faults. The method, presented in this paper, is intended for an early detection of broken rotor bars in induction motors. With this procedure, no additional hardware is necessary, except for a simple and fast algorithm that can run in parallel with an existing control program and can be implemented in an already present microprocessor circuitry. From voltage measurement through existing voltage probes, an average deviation from normal values, can be determined. This data serves as a diagnostic index that depends on the number of broken bars, i.e. the degree of the fault.
COBISS.SI-ID: 7819604
Synchronous motors are gradually replacing induction and DC motors in demanding applications with servo drives. In the area of control of AC machines, two methods have established themselves: field orientation control (FOC) and direct torque control (DTC). The first one enables reliable control, whilst the second offers better dynamics. At the same time, both methods exhibit some drawbacks: FOC is relatively complicated and contain inherent delays, while DTC is characterized by high torque ripple. The proposed method uses advantages of FOC, since the variables are transformed into field coordinates. On the other side, instead of using space vector modulation (SVM) it implements original method, named direct current control (DCC). The presented results obtained on a laboratory model of a synchronous motor show very good dynamic performance while reducing the switching losses.
COBISS.SI-ID: 7253844
This paper presents results of a comparative study of two possible hybrid filter topologies, comprised of a passive and active stage, which can be implemented in any general dc supply distribution system. The active stage is incorporated into the passive part in order to: 1) improve its insufficient attenuation in the low-frequency range and 2) source or sink any surplus energy flow between the dc source and load in case of low frequency current dynamics. In the low-frequency range nearly for 15 dB higher attenuation compared to the passive filter is achieved.
COBISS.SI-ID: 7554388
The paper describes a mathematical model to be used in calculating the current distribution among the coils in the low-voltage winding of the furnace transformer. The method is derived from the leakage magnetic-field distribution in the transformer based on the minimum magnetic-field energy. The energy is calculated by using the principle of the minimum reactive power in the transformer window. The results are validated by finite-element model. The knowledge of the proper current distribution is very useful in designing the furnace-transformer cooling system to avoid local overheating.
COBISS.SI-ID: 9305684