AN IMPROVED CONTROL ALGORITHM FOR «DYNAMIC CAPACITOR» VAR COMPENSATOR
Journal Title: Електротехніка і Електромеханіка - Year 2015, Vol 0, Issue 5
Abstract
Purpose. Modern approaches of VAR compensation are: using compensators with stepped regulation, STATCOMs, active pow-er filters. Recently, more attention is paid to VAR compensator’s design based on the direct AC / AC converters, which are called dynamic capacitors. Methodology. The dynamic capacitor (D-CAP) is the capacitor bank, which is connected to the mains through direct AC / AC buck converter. By varying the duty cycle of bidirectional switches, smooth control of reactive power can be achieved. However, in case of distorted mains voltage, D-CAP mains current will have a high THD. This is due to the fact that the D-CAP affects the frequency response of electric grid thus leading to the appearance of resonances. With non-sinusoidal mains voltage, capacitors are affected by harmonics. This reduces the reliability of the D-CAP, increasing the prob-ability of their failure. To eliminate these drawbacks it is sug-gested to improve the D-CAP control system so that the input current of the dynamic capacitor is forced to be close to sinu-soidal. This can be achieved if the duty cycle of the switching bi-directional switches is changed according to the proposed ex-pression. Results. The research is done on a single-phase D-CAP with the proposed control system, its input current dia-grams are shown. In contrast to the D-CAP with a constant duty cycle control, the resulting THD of its input current is much lower. Thus, the control system provides a form of the input current that is close to a sine wave. This reduces the influence of mains voltage harmonics on the D-CAP operation, increases its reliability and improves power quality. Originality. The pro-posed D-CAP control system ensures reliable operation with non-sinusoidal mains voltage. Practical value. Application of D-CAPs with the proposed control system allows for improved energy efficiency of electrical mains by providing VAR compen-sation and improving power quality.
Authors and Affiliations
S. K. Podnebennaya
Keywords
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- EP ID EP298264
- DOI 10.20998/2074-272X.2015.5.08
- Views 97
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