A Current Source Converter based Active Power Filter for mitigation of harmonics at the interface of distribution and transmission systems
ABSTRACT A medium power Current Source Converter (CSC) based Active Power Filter (APF) system is designed and implemented to suppress the amplification of low order harmonics at the Medium Voltage (MV) interface bus between the distribution and transmission systems, owing to the presence of large shunt capacitor banks installed only for reactive power compensation. For this purpose, four CSC based APF units designed at 1.0 kV are operated in parallel, and connected to the 31.5 kV MV bus via a specially designed coupling transformer. In each APF module, a specially designed LC-type input filter eliminates the switching ripples, and active damping method embedded into the control software suppresses harmonic frequencies around the natural frequency of the input filter. The resulting system can operate at relatively high frequencies in the range from 2.0 to 3.0 kHz, depending upon which selected harmonics among 5th, 7th, 11th, and 13th are to be eliminated. Furthermore, in order to reduce the installed capacity of CSCs, Selective Harmonic Amplification Method (SHAM) is applied to the APF system described in the paper. MV APF system has been built as a mobile system for temporary connection to a problematic MV interface bus, until a permanent solution is found for that location in the distribution system.
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ABSTRACT: Renewable energy sources (RESs) in any power system can participate in removing the harmonics from the line voltage, but the RESs need to estimate these harmonics first. In this paper, an efficient method to estimate grid harmonics is proposed to be used by single-phase RESs. The proposed method provides accurate estimation for the harmonics while it has lower computation complexity than the other existing methods. To make the harmonic estimation process fast and accurate, the harmonics in the sampled grid voltage is eliminated before passing it to the phase-locked-loop block used for estimating the grid phase. Another application of the proposed method is to transform single-phase voltage or current from the stationary reference frame into the $dq$ rotating reference frame. In this application, the use of the proposed method eliminates the need of generating fictitious voltage or current waveforms orthogonal to the measured quantities. The elimination of need to generate fictitious waveforms speeds up the transformation transients and reduces the operations to less than half of those required by traditional methods. Simulation and experimental results verified that the algorithm achieves fast and accurate harmonic estimation of highly distorted grid voltage.IEEE Transactions on Industry Applications 01/2014; 50(1):620-630. · 1.67 Impact Factor
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ABSTRACT: This paper presents a control algorithm based on enhanced phase-locked loop (EPLL) for distribution static compensator (DSTATCOM) to compensate reactive power, to provide load balancing, to eliminate harmonics, to correct power factor, and to regulate point of common coupling (PCC) voltages under linear and nonlinear loads. In this approach, an extraction of fundamental active and reactive power components of load currents for the estimation of source currents includes a signal-processing algorithm based on the EPLL scheme. The proposed control algorithm is implemented using a digital signal processor. Test results on a developed DSTATCOM are presented to validate the proposed control algorithm for compensation of reactive power, load balancing, harmonics elimination, power factor correction, and zero voltage regulation at PCC.IEEE Transactions on Power Delivery 01/2013; 28(3):1516-1524. · 1.52 Impact Factor