Sigmar Maurer Deckmann

Characterization and Compensation of Harmonics and Reactive Power of Residential and Commercial Loads

This paper uses data obtained from laboratory measurements of typical home appliances to verify whether these nonlinear loads behave similar to current or voltage-type harmonic sources. Based on the measurements and additional simulations, it is stated that domestic and commercial electronic loads behave essentially like harmonic voltage sources. This behavior helps to explain why reactive shunt compensators and filters may even increase the harmonic current content in the feeders. Additionally, based on field measurements in a residential low-voltage distribution secondary, the share between linear and nonlinear loads, as well as the prevailing kind of their nonlinearity is analyzed. The measurements, made just before and after the installation of a capacitor bank, confirm that the use of shunt compensation increases both voltage and current distortion in the feeder

Frequency-Adjustable Positive Sequence Detector for Power Conditioning Applications

This paper proposes a novel and simple positive sequence detector (PSD), which is inherently self-adjustable to fundamental frequency deviations by means of a software-based PLL (phase locked loop). Since the proposed positive sequence detector is not based on Fortescues classical decomposition and no special input filtering is needed, its dynamic response may be as fast as one fundamental cycle. The digital PLL ensures that the positive sequence components can be calculated even under distorted waveform conditions and fundamental frequency deviations. For the purpose of validating the proposed models, the positive sequence detector has been implemented in a PC-based power quality monitor and experimental results illustrate its good performance. The PSD algorithm has also been evaluated in the control loop of a series active filter and simulation results demonstrate its effectiveness in a closed-loop system. Moreover, considering single-phase applications, this paper also proposes a general single-phase PLL and a fundamental wave detector (FWD) immune to frequency variations and waveform distortions

Selective disturbance compensation and comparisons of active filtering strategies

This paper presents an alternative method to evaluate selectively disturbance compensation. Instantaneous decompositions to be applied directly on voltages and current signals are used to identify the distorting and unbalancing components, and can be used to compensate either nonactive power, power oscillations, harmonics and load imbalances in a different way as provided by the traditional pq theory. Three control strategies of active filters were tested and compared for solving typical power quality problems. Simulation results are presented to show the main differences among the control strategies facing nonlinear, unsymmetrical and variable loads under generic voltage conditions. According to these results, it is shown that some shunt active filtering strategies can even improve the PCC voltages under resonance conditions.

Flicker propagation and attenuation

This article presents a brief study of flicker propagation and attenuation along a network. A DLL routine was implemented to emulate a digital flickermeter capable to run with commercial network simulation software. The voltage fluctuations are obtained by load modulation on the simulator. The results confirm some expected results, such as the influence of the short-circuit ratio and the voltage regulating effect of rotating machines upon flicker attenuation. A methodology to estimate flicker transfer factors is also presented.

Virtual Instrumentation Applied to the Implementation of IEEE-STD 1459-2000 Power Definitions

This paper discusses the utilization of virtual instrumentation to the implementation and evaluation of different power definitions, so that classical formulations and new definitions can be compared without the necessity of acquiring different power meters or analyzers. Accordingly, the definitions of IEEE Standard 1459-2000 for the measurement of power quantities under distorted and unbalanced situations, have been digitally implemented. Thus, several power and power factor components related to the decomposition of the measured voltage and current signals have been obtained. The proposed PC-based virtual instrument uses a high performance acquisition board and isolated sensors and transducers. All digital algorithms and routines have been implemented by means of a graphical development system. Regarding to the implementation of STD 1459, this paper also proposes several different algorithms to the required decompositions of voltage, current and power components

About voltage sags and swells analysis

Time at level analysis of discrete events is proposed to characterize voltage sags and swells instead of the simple magnitude vs duration characteristics presently used. Although requiring a little more computer memory and digital processing, the proposed methodology constitutes a significant improvement for the characterization of unpredictable temporary voltage disturbances through simple numerical index. Some potential applications of the new method are: full conformity verification to existent or future standards; direct comparison with load sensitivity curves; implicit data compression for transmission and storage; automatic event classification; events ranking and propagation analysis. An IEEE database of voltage sags and swells was used to test the proposed methodology.

Flicker produced by harmonics modulation

Flicker effect caused by voltage harmonics modulation is discussed. Simple functions are used to show that harmonic components, despite satisfying the specific harmonic limits, may produce flicker due to combined amplitude modulation. Computer simulations, based on the International Electrotechnical Commission (IEC) methodology, are numerically validated and then applied to calculate the instantaneous flicker sensation resulting from different combinations of harmonics modulation. The results are also confirmed in laboratory tests using a flicker meter to measure the flicker levels obtained by synthesizing the same type of signals on a programmable function generator.

The Influence of Voltage Referential in Power Quality Indices Evaluation

This paper discusses the importance of the voltage referential for power quality monitoring and power systempsilas instrumentation. Considering the operating conditions of simple power circuits, it will be demonstrated that an incorrect choice of the voltages referential may result in erroneous quantification of some power quality indices, especially in three-phase four wire circuits. The use of a virtual reference point and the neutral conductor as reference have been considered and the simulation results confirm the influence of the voltage reference selection in the evaluation of total harmonic distortion, unbalance factors and voltage sags. Finally a way of linking both methods will be discussed by means of Blakesleypsilas theorem.

On-line evaluation of voltage quality indexes for harmonic distortion, flicker and sequence components

This paper describes an on-line voltage quality monitoring system, which detects simultaneously the total harmonic distortion, instantaneous flicker sensation and unbalancing components, present in three-phase voltages. To test the proposed monitoring functions, a microcomputer based system was implemented, processing the data on-line at 2.4 kHz sampling rate per phase. Signals with known disturbing effects were used to validate the algorithms. Results obtained from monitoring the network secondary voltages, are also presented to demonstrate the application feasibility of the proposed monitoring system.

Metodologia para identificação do componente fundamental da tensão da rede baseada no algoritmo recursivo da TDF

Considering the increasing demand on digital processing techniques for power electronics and power systems application, this paper deals with the use of a Recursive Discrete Fourier Transform (RDFT) for phase angle, frequency and magnitude identification of the grid fundamental voltages, irrespective to waveform distortions, frequency or amplitude deviations. It will be discussed that if the fundamental frequency of the measured voltages exactly matches the frequency for which the DFT has been designed, an ordinary RDFT algorithm is completely able to provide the necessary information about phase, frequency and magnitude. Two additional algorithms have been proposed to ensure the correct performance if the frequency departs from its nominal value: one for phase correction and another for identification of the fundamental component magnitude. Moreover, it is important to point out that by means of the proposed algorithms, the fundamental component can be identified in less than 2 cicles, independently of the input voltage signal. The analysis of the RDFT has been performed by means of simulation results. In order to evaluate the behavior of the RDFT in a practical system, experimental results regarding to the synchronization of a small generator and the power grid will be presented.