Group: 2014-FYP-28



Dr. Tahir Izhar


Sensitive loads require an uninterruptible supply of voltage and they are particularly prone to voltage sags. As variations in load voltage can cause severe damage to them and sometime complete failure of systems. This project presents an improved voltage control method that can compensate for voltage sags and swells in the power system and maintain the voltage in desired range. The most severe problems in the power system are voltage sags, swells, harmonics and spikes. In order to overcome these problems many devices including DVR is choice of interest. DVR is most e?cient and e?ective modern custom power device which is used in power distribution networks. DVR basically employs a series of voltage boost technology using solid state switches that injects voltage into system; in order to maintain the system voltage at rated value. DVR can also add other features like line voltage harmonics compensation, reduction of transients in voltage and fault current limitations. In our technique, during the times of voltage sag or swell, the source voltage is made to pass through an IGBT connected in AC RMS voltage controller configuration which chops the sine wave according to a certain value of duty cycle decided after comparing the measured voltage at load end with the desired value that is 230V RMS. According to error in desired and sensed voltage, PWM is generated according to which sine wave is chopped. This chopped sine wave is then fed to an auto-transformer which doubles the voltage at its output, this is compensated voltage. A filter at the output gets rid of the harmonics in the chopped wave as switching frequency of PWM is as high as 3khz. This filter produces a pure sinusoidal waveform of required magnitude at the load. This technique is more effective in the sense that, it uses only less switching devices and has a very quick response during abnormal conditions.

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