Electric Power Quality
Electric power quality is a term which has emerged and attracted attention in electrical power engineering in recent years, because end-use equipment is more sensitive to disturbances that arise both on utility power systems and within customer facilities. Also, this equipment is more interconnected in networks and industrial processes so that the impacts of a problem related to electric power quality on any piece of equipment are much more severe. Therefore, understanding the performance of power systems is becoming more and more important. Attention to power quality is a joint user-utility responsibility. The power quality problems can be overcome by the efforts between utilities and customers with applications of power electronics such as active power filters, dynamic voltage restorers, etc.
Active Power Filters
With the proliferation of non-linear loads such as diode/thyristor rectifiers, non-sinusoidal currents are produced and introduce harmonic pollution into the power system. These undesirable harmonics not only have deteriorated the power quality but also have induced the effect of interference in electronic circuits. The active power filters not only compensate for harmonics, but also compensate for reactive power, negative-sequence current, neutral current and/or flicker in the industrial power systems.
Dynamic Voltage Restorers
In many industrial processes high power quality is essential for their proper operation. Even slight voltage sags lasting only a few tenths of a second may result in disturbances with considerable costs due to loss of production. Voltage deviations are caused either by faults and their clearance in the high voltage grid or by fluctuations of load especially in weak distribution networks. Dynamic Voltage Restorers (DVRs) correct for voltage sags and unexpected load changes: maintaining the voltage to sensitive loads within acceptable tolerances. The result is improved process productivity and significant customer cost savings.
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