4 research outputs found

    Cascaded Multilevel Inverter-Based Asymmetric Static Synchronous Compensator of Reactive Power

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    The topology of the static synchronous compensator of reactive power for a low-voltage three-phase utility grid capable of asymmetric reactive power compensation in grid phases has been proposed and analysed. It is implemented using separate, independent cascaded H-bridge multilevel inverters for each phase. Every inverter includes two H-bridge cascades. The first cascade operating at grid frequency is implemented using thyristors, and the second one—operating at high frequency is based on the high-speed MOSFET transistors. The investigation shows that the proposed compensator is able to compensate the reactive power in a low-voltage three-phase grid when phases are loaded by highly asymmetrical reactive loads and provides up to three times lower power losses in the compensator as compared with the situation when the compensator is based on the conventional three-level inverters implemented using IGBT transistors.publishedVersio

    Išėjimo įtampos moduliavimo strategijos įtaka inverterio galios nuostoliams

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    The technique and results of investigation of power losses in inverter obtained for case when proposed Space Vector Pulse Frequency Modulation (SVPFM) method with averaged pulse lengths is employed for forming of three-phase inverter output voltage are presented in the work. The obtained results were compared with the results gained for conventional SVPFM method. It is shown that employment of the suggested modification of the SVPFM method allows decreasing the power losses in inverter, which is used in frequency converter for AC induction motor control, as compared to the case when conventional SVPFM method is employed. It is stated that reduction of power losses is caused by introduction of the switch commutation algorithm, which enables to minimize the number of switching of inverter switches and avoid commutations at maximal current. Additional reduction of the power losses is achieved by use of averaged pulse lengths, which allow improving the initial part of voltage spectrum.Lietuviška santrauka. Pateikta inverterio galios nuostolių tyrimo metodika ir rezultatai, gauti, kai jo trifazei išėjimo įtampai formuoti taikomas pasiūlytas vidutinės trukmės impulsų vektorinės erdvinės moduliacijos metodas. Tyrimų rezultatai lyginami su rezultatais, gautais įprastiniu EVIDM metodu. Parodyta, kad pasiūlytas metodas leidžia sumažinti galios nuostolius inverteryje, naudojamame dažnio keitiklyje asinchroniniams trifaziams elektros varikliams valdyti. Konstatuojama, kad galios nuostoliai sumažėja todėl, kad pasiūlytu metodu suformuota įtampa turi mažesnes žemojo dažnio spektro dedamąsias ir yra naudojamas raktų junginėjimo algoritmas, kuris leidžia išvengti raktų junginėjimosi laiko intervale, kuriame šiais raktais tiekiama srovė yra didžiausia

    CONSTANT SLIP CONTROL SYSTEM OF AN ASYNCHRONOUS MOTOR / PASTOVAUS SLYDIMO ASINCHRONINIO ELEKTROS VARIKLIO ROTORIAUS GREIČIO VALDYMO METODAS

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    Asynchronous motors are efficiently controlled using the scalar method. Main problems appear when the motor is fully loaded and desired rotation speed is slow. In such cases, the motor slip exceeds the magnitude of the nominal slip, causing the increase in stator current. The constant slip method was designed to control hardly loaded asynchronous motor. In this particular situation, the constant slip method provides a better efficiency than the scalar method. The magnitude of the motor current refers to the slip: the less is the slip, the less is the magnitude. It is impossible to find the optimal slip for minimization of current with the help of a model. Therefore, the nominal slip value was used as optimal. Santrauka Pasiūlytas pastovaus slydimo asinchroninio elektros variklio rotoriaus greičio valdymo metodas ištirtas modeliuojant, gauti rezultatai palyginti su skaliarinio valdymo metodo tyrimo rezultatais. Tyrimo rezultatai parodė, kad pastovaus slydimo asinchroninio variklio greičio valdymo metodas yra pranašesnis už skaliarinio valdymo metodą, kai valdomo variklio greitis yra nedidelis ir jo apkrova yra artima nominaliajai. Reikšminiai žodžiai: asinchroninis variklis, rotoriaus slydimas, dažnio keitiklis, inverteris, valdymo sistema

    Cascaded Multilevel Inverter-Based Asymmetric Static Synchronous Compensator of Reactive Power

    No full text
    The topology of the static synchronous compensator of reactive power for a low-voltage three-phase utility grid capable of asymmetric reactive power compensation in grid phases has been proposed and analysed. It is implemented using separate, independent cascaded H-bridge multilevel inverters for each phase. Every inverter includes two H-bridge cascades. The first cascade operating at grid frequency is implemented using thyristors, and the second one—operating at high frequency is based on the high-speed MOSFET transistors. The investigation shows that the proposed compensator is able to compensate the reactive power in a low-voltage three-phase grid when phases are loaded by highly asymmetrical reactive loads and provides up to three times lower power losses in the compensator as compared with the situation when the compensator is based on the conventional three-level inverters implemented using IGBT transistors
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