Performance enhancement of dynamic voltage restorer for voltage sag and swell problems using artificial intelligent controller

Abstract

Power Quality (PQ) in distribution systems and their solutions have received much attention in the recent years and have become an area of concern for modern industrial and commercial applications. Complicated industrial loads, commercial loads and distribution networks all are disturbed from various types of PQ problems such as voltage sag, voltage swell, power interruptions, harmonics, etc. At present, voltage sag and swell are recognized as the most frequent and severe threats and have consequences such as sensitive load tripping, production loss, revenue loss, malfunction of control equipment, equipment fail ure and long-term breakdown of components. Therefore, the need for solutions dedicated to customers with highly sensitive loads is significant and a fast response of voltage regulation is required. Dynamic Voltage Restorer (DVR) is a power electronic converterbased device, intended to protect crucial loads from supply-side voltage disturbances. DVR has become a well-known cost-effective solution for very deep sag and swell problems. The mitigation capability of DVR mostly depends on its maximum voltage injection ability and its active power contribution. In conventional DVR, battery energy storage is used as a DC input to provide active power, but batteries are still bulky, costly and must be disposed of once their chemicals are utilized. This limits the compensation capability of DVR. For better compensation, the choice of DC link voltage chosen should be higher than 1.5 times the grid voltage, which increases the VA rating of DVR. This leads to increase the size of DVR and its capital investment, which restrict its installation for many places. There has been an enhanced interest to incorporate Renewable Energy Resources at the DC input terminal of custom power devices like STATCOM and DVR. The chosen energy storage should be able to provide very high peak power during short time duration; the Ultra Capacitors (UCAP) are the better choice for energy storage instead of batteries with less cost