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This paper proposes a novel DC-side controller for grid-connected voltage source converters during asymmetrical faults. The controller is based on a modified second order generalized integrator (SOGI). The main objective is to mitigate the second order harmonic voltage oscillation on DC link as well as the positive sequence third-order harmonic current injection into the AC grid, due to negative sequence...
Characteristics of the current emission for new developed devices are changing resulting in lower low order harmonics and an increase in high order harmonics. For the low voltage network this results in an increase in high order harmonic voltages, violating more often the limits for the harmonic voltages at the 15th and 21th order harmonic. To improve this situation harmonic current could be reduced,...
This paper presents use of no-load current harmonic analysis to detect presence of inter-turn fault at incipient stage. At steady state, third and fifth harmonic components are predominant in transformer no-load current. Inception of fault results in decrease in THD and increase in increase in primary current. Based on reduction of total harmonic distortion (THD) of each phase and simultaneous increase...
A Hysteresis current control (HCC) modulation is commonly used because of its various advantages. However, the HCC modulation has the disadvantage that the modulation frequency varies in a fixed band and, consequently, produces non-optimum current ripples. To overcome this drawback, an adaptive hysteresis-band current control (AHCC) modulation has been suggested. However, when the AHCC is employed...
This paper proposes a method based on Wavelet Transform to determine an adaptive threshold to be used in the segmentation of combined disturbances related to Power Quality. This method is based on the decomposition of electrical signals that contain combined disturbances and uses the calculation of energy and entropy of energy of the second level of decomposition, obtained by Wavelet Transform, to...
This work deals with a shunt active power filter, which is controlled to compensate residential installations fed by two-phases and neutral derived from a three-phase grid. A compensation strategy is proposed to mitigate harmonic currents, reactive power and neutral currents due to reactive and nonlinear loads. System characteristics, the proposed control strategy and its implementation scheme are...
The Hysteresis current control (HCC) is a popular modulation technique used in active power filter (APF) applications owing to its simplicity of implementation, fast current response and peak current limiting capability. Despite these advantages, it has a major disadvantage when applied to three-phase isolated neutral point (INP) systems: interphases dependency causes very high-switching frequencies...
This paper presents a control method based on dynamic model of three-level neutral-point-clamped (NPC) voltage source converter (VSC) for integration of renewable energy sources (RESs) into the power grid. The proposed control method can provide continuous injection of active power besides the compensation of all reactive power and harmonic current components of loads through integration of RESs into...
The level of harmonic currents emitted by nonlinear household devices depends on many factors. Beside the general circuit topology, e.g. presence or absence of power factor correction (PFC) circuit the emission depends significantly on the distortion of the supply voltage. The paper discusses typical voltage distortions in public low voltage grids and proposes parameters for their quantification....
Power Quality is one of the critical issues when operating contemporary distribution networks. The increased interest in PQ is due to the increased employment of sensitive equipment loads and renewable generation technologies. Currently, the evaluation of PQ network performance is based on evaluating different phenomena separately, and a standardised way to evaluate the PQ as a whole for a bus or...
This paper presents a study of circulating current suppression control (CCSC) dynamic of Modular Multilevel Converter (MMC). This study is based on a 10th order linearized model composed of 6 states representing the basic dynamic of MMC and 4 states describing the dynamic of CCSC. The MMC dynamic states are zero sequence, basic frequency and second harmonics of maximal arm capacitor voltages in dq0...
Studies carried out by the Dutch transmission system operator TenneT have shown that the harmonic impedance of the 380 kV transmission grid, as observed from the point of connection for planned offshore wind power plants, could lie on a low resonance frequency of about 100 Hz. There is a concern that the low resonance frequencies could result in possible elevated voltages (Temporary Overvoltages,...
This work reviews the state-of-the-art in the field of harmonic resonance problems in Wind Power Plants (WPPs). Firstly, a generic WPP is modeled according to the equivalent circuits of its passive and active components. Main focus is put on modeling active components, i.e. the ones based on power converters. Subsequently, pros and cons of frequency and time domain analysis methods are outlined. The...
Static Var Compensator (SVC) is one of the most popular modern power system elements to stabilize voltage as well as to compensate reactive power demand. There are varieties of such circuit which deal with different technical arrangement, reactive power compensation technique, contribution to power system stability and individual features as well. In this paper simulation and experimental results...
Power quality levels in public low voltage grids are influenced by many factors which can either be assigned to the electrical environment (connected consumers, connected generation, network characteristics) or to the non-electrical environment (e.g. climatic conditions) at the measurement site. Type and amount of connected consumers (consumer topology) are expected to have a very high impact on power...
This work proposes a frequency-adaptive data processing technique for reliable synchrophasor measurements estimation under power system frequency variation. The proposed technique consists of four steps in which frequency estimation, filtering process, fast linear interpolation, and Radix-2 decimation-in-time (DIT) fast Fourier transform (FFT) approach are applied in a synergistic manner to provide...
The high penetration of photovoltaic systems in low voltage distribution networks can cause power quality problems due to the increased level of harmonics. In this paper an overview of the relevant power quality standards is provided along with an investigation of the harmonics generation in LV networks. Hardware experiments of harmonics measurements of PV inverters are conducted where the influence...
The concept of Wide-Area Measurement Systems (WAMS) envisages the transmission of current and voltage phasor samples from remote Phasor Measurement Units (PMUs) to control centres, relays or controllers. Compression of the high frequency samples of sinusoidal waveforms into phasors is usually done using Discrete-Fourier Transform(DFT)-like algorithms. The phasor data is normally useful only when the...
This paper reviews typical circuit topologies and control algorithms for on-board unidirectional single-phase electric vehicle battery chargers (EVBCs) and provides simple yet reasonably accurate component-based models for their representation for power system analysis. The accuracy of the developed models is validated against measurements of actual EVBCs, for both ideal voltage supply conditions...
Low Frequency AC transmission (16.7Hz) has recently gained notable interest in literature as an alternative to the existing VSC-HVDC transmission solution for integrating offshore wind parks. Its key advantages being the substantial gain in the range of transmissible power over traditional 50 Hz methods and the removal of the offshore converter compared to VSC-HVDC. This paper presents a system level...
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