Abstract
A novel compensator topology is proposed for three-phase unbalanced loads in the distribution networks. The negative and zero sequence compensation networks are proposed using delta-connected and star-connected capacitor banks. The compensation networks are paralleled with the unbalanced load to achieve a perfect balancing of active power and a complete compensation of reactive power of the unbalanced load. Intelligent grouping compound switches are implemented to control the capacitors, where, therefore, each capacitor can be switched between phases or phase and ground. Wireless sensors are also applied to acquire the load quantities. The compensation method proposed is based on symmetrical component theory. In addition, the load compensation based on instantaneous symmetrical component theory with positive sequence online extraction is proposed under unbalanced and distorted source voltages. The proposed load-balancing method and device are applied to Liaoning, Neimenggu, and Jilin provinces. The application results are provided to validate the performance of the proposed compensator topology and compensation method.
Highlights
At present, the low-voltage three-phase four-wire distribution systems are facing the poor power quality problems such as high reactive power burden, unbalanced load, excessive neutral current, and voltage distortion
The static var compensator (SVC) which consists of delta-connected thyristor-controlled reactors and star-connected thyristor-controlled reactors and passive filters acts as a classic reactive power compensator for load balancing and power factor correction
The present paper sustains a new method applied for load balancing and reactive power compensation by using the model containing only capacitor banks which are controlled with intelligent grouping compound switches
Summary
The low-voltage three-phase four-wire distribution systems are facing the poor power quality problems such as high reactive power burden, unbalanced load, excessive neutral current, and voltage distortion. Active power filter (APF), combinations of APF and thyristor binary compensator (TBC), capacitor-clamped APF and DSTATCOM [7,8,9,10,11,12], and voltage source inverter (VSI) [13,14,15] have been proposed to compensate reactive power and unbalanced load and eliminate harmonics. For the combination of APF and TBC [8], the TBC compensates reactive power and balances the load, but it needs enormous capacitors and the utilization is not high, and three-phase four-wire system is not considered. Other problems need to be taken into account, such as unbalanced source currents and/or excessive current flowing through the neutral conductor These problems are mainly caused by unbalanced loads connected to three-phase four-wire systems. In order to avoid the use of the communication wire line and to improve the system reliability, wireless sensors are applied to acquire the realtime unbalanced load quantities in this paper
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