Search

Unintentional series and/or parallel resonances, due to the tuned passive filter and the line inductance, may result in severe harmonic distortion in the industrial power system. This paper presents a hybrid active filter to suppress harmonic resonance and to reduce harmonic distortion. The proposed hybrid filter is operated as variable harmonic conductance according to the voltage total harmonic distortion; therefore, harmonic distortion can be reduced to an acceptable level in response to load change or parameter variation of the power system. Since the hybrid filter is composed of a seventh-tuned passive filter and an active filter in series connection, both dc voltage and kVA rating of the active filter are dramatically decreased compared with the pure shunt active filter. In real application, this feature is very attractive since the active power filter with fully power electronics is very expensive. A reasonable tradeoff between filtering performances and cost is to use the hybrid active filter. Design consideration are presented, and experimental results are provided to validate effectiveness of the proposed method. Furthermore, this paper discusses filtering performances on line impedance, line resistance, voltage unbalance, and capacitive filters. [ABSTRACT FROM PUBLISHER]

Voltage fluctuations resulting from variable output power of renewable energy sources are strictly challenging power quality in distributed-generation systems. This paper presents a control method for distributed static synchronous compensator (D-STATCOM) to alleviate variation of both positive- and negative-sequence voltages. The D-STATCOM simultaneously operates as fundamental positive-sequence admittance and fundamental negative-sequence conductance to restore the positive-sequence voltage to the nominal value as well as reduce the negative-sequence voltage to an allowable level. Both admittance and conductance are dynamically tuned to improve voltage-regulation performances in response to load changes and power variation of renewable sources. A proportional–resonant current regulator with selectively harmonic compensation is realized to control the fundamental current of the D-STATCOM as well as reduce the harmonic current, which could be an advantage in practical applications due to high voltage distortion in low-voltage microgrids. Voltage-regulation performances are discussed for different D-STATCOM locations as well as different D-STATCOM currents. Computer simulations and laboratory tests validate effectiveness. [ABSTRACT FROM PUBLISHER]

This paper summarizes the main problems and solutions of power quality in microgrids, distributed-energy-storage systems, and ac/dc hybrid microgrids. First, the power quality enhancement of grid-interactive microgrids is presented. Then, the cooperative control for enhance voltage harmonics and unbalances in microgrids is reviewed. Afterward, the use of static synchronous compensator (STATCOM) in grid-connected microgrids is introduced in order to improve voltage sags/swells and unbalances. Finally, the coordinated control of distributed storage systems and ac/dc hybrid microgrids is explained. [ABSTRACT FROM PUBLISHER]

This paper presents a review of advanced control techniques for microgrids. This paper covers decentralized, distributed, and hierarchical control of grid-connected and islanded microgrids. At first, decentralized control techniques for microgrids are reviewed. Then, the recent developments in the stability analysis of decentralized controlled microgrids are discussed. Finally, hierarchical control for microgrids that mimic the behavior of the mains grid is reviewed. [ABSTRACT FROM PUBLISHER]