Distortion Power Research Articles

INFLUENCE OF SOLAR POWER PLANTS ON LOW-VOLTAGE DISTRIBUTION NETWORKS

It is analyzed indexes of electromagnetic compatibility of a solar power plant connected to a low-voltage network. According to the experimentally measured instantaneous values of currents and voltages generated by solar power stations, the currents of the higher harmonics are calculated. The measurement results showed that the presence of photovoltaic systems in the network can lead to a decrease in the quality parameters of the supply voltage, such as voltage fluctuations, harmonic distortion factors, voltage flicker and power factor. A comparison of the admissible values of the main parameters of electric energy with the experimental data is made. The probability of occurrence of oscillating energy-exchange processes and the need for experimental determination of the network impedance are shown.

INDIRECT POWER CONVERTER AS A SOURCE OF HARMONICS IN A SMART GRID

Investigated electromagnetic processes in the primary level of two-frequency converters, built on the inverter voltage. Implemented mathematical description of the processes that characterize intermittent, continuous, boundary-continuous and boundary-discontinuous modes. Set the difference between the last two modes. At the boundary point mode discovered the discontinuity in mathematical functions of integral indicators, including displacement power factor and distortion power factor of the SMART grid current indirect power converters.

Evaluation of Pattern Recognition Algorithms for Applications on Power Factor Compensation

This paper assesses different applied pattern recognition algorithms to decide the most appropriate power factor compensator for a particular point of common coupling. Power factor, current unbalance factor, total demand distortion, voltage harmonic distortion and reactive power daily variation, as well as human expertise, are the key parameters used to set each recognition algorithm. These algorithms are then trained with a series of both simulation and experimental data. Numerical results consistently indicate the decision-tree algorithm with depth 20 as the best classifier for power factor improvement in terms of all metrics considered in this work.

Selective Compensation of Distortion, Unbalanced and Reactive Power of a Thyristor-Controlled LC -Coupling Hybrid Active Power Filter (TCLC-HAPF)

Selective Compensation of Distortion, Unbalanced and Reactive Power of a Thyristor-Controlled LC -Coupling Hybrid Active Power Filter (TCLC-HAPF)

Enhanced low‐voltage ride‐through capability of flying capacitors inverter using model predictive control

Summary This paper proposes an enhancement of the low-voltage ride-through (LVRT) capability of multilevel flying capacitors inverter using an improved model predictive control (MPC). The proposed solution is a multiobjective control strategy ensuring simultaneous capacitors' voltages balancing and grid current injection with reduced total harmonics distortion (THD) and unity power factor even under severe voltage sags. The proposed MPC technique makes use of a multioptimization solution for the common problem of weight dissimilarity of the control objectives. The first optimization is achieved by the inclusion of the state variables normalization within the cost function computation. This will provide to the proposed MPC technique more robustness with the ability to take into consideration external disturbances (grid voltage sag) while ensuring the meeting of the state variables constraints. The second one is achieved through accurately tuning the weighting factor based on minimizing the grid current total harmonics distortion and the maximal errors on the capacitors' voltages. Theoretical analysis and simulation results are presented to prove that the presented solution guarantees continuous and smooth power transfer to the grid even under severe voltage sags. The obtained results are validated on a 1-kW experimental prototype.

Event-Based Energy Disaggregation Algorithm for Activity Monitoring From a Single-Point Sensor

The massive deployment of smart meters and other customized meters has motivated the development of nonintrusive load monitoring (NILM) systems. This is the process of disaggregating the total energy consumption in a building into individual electrical loads using a single-point sensor. Most literature is oriented to energy saving. Nevertheless, activity of daily livings monitoring through NILM is recently receiving much interest. This proposal presents an event-based NILM algorithm of high performance for activity monitoring applications. This is divided into two stages: 1) an event detector and 2) an event classification algorithm. The first one does not need to be trained and shows a detection rate up to 94%. The event classification algorithm uses a novel load signature based on trajectories of active, reactive, and distortion power (PQD) to obtain general models of appliance classes using principal component analysis. The F1 score and the F0.5 score (the last one is more relevant to activity monitoring) draw values of 90.6% and 98.5, respectively.

A Varying Frequency LPV-Based Control Strategy for Three-Phase Inverters

Grid-connected inverters have drawn a lot of attention in the integration of distributed generation systems and microgrids, as they are an effective interface for renewable and sustainable energy sources. Several strategies, including repetitive and resonant controllers, have been implemented in order to achieve low distortion and high-quality power. However, it has been proved that their performance decreases substantially when the grid frequency varies. This paper proposes a resonant control strategy based on a linear parameter varying (LPV) design, which is able to deal with changes in the network frequency. Controller aim is associated with injecting a clean sinusoidal current to the grid, even in the presence of nonlinear/unbalanced loads and/or grid-voltage distortions. Main emphasis is focused on presenting an applied LPV design procedure that covers plant modeling, controller synthesis, stability analysis, and experimental results that show the feasibility and effectiveness of the proposed scheme.

Multilevel Converter Based on Cascaded Three-Leg Converters with Reduced Voltage and Current

In this paper, a modularity concept using standard three-leg converters is addressed. Three-phase cascaded topologies composed of standard three-leg converters are investigated. They are composed of three, nine, twenty-one, or $n$ three-leg converters. It permits the reduction levels of currents and voltages on switches when compared with a conventional three-phase module or a cascaded H-bridge structure. In this way, three-leg cascaded converters are suitable to be applied in scenarios of high current in which other cascaded topologies become less attractive and high voltage. Furthermore, the proposed arrangement brings advantages such as modularity that leads to convenient construction, easy maintenance, and extension to higher voltage and current levels. A dynamic model is developed and a pulse-width modulation strategy is designed to the converter command accordingly with reference voltage. Discussions about fault tolerance and dc-link capacitor currents are also carried out. Comparisons in terms of converter rating, harmonic distortion, and semiconductor power losses between the proposed and conventional cascaded H-bridge topologies have been carried out. Simulation and experimental results are presented as well.

Voltage-Balancing Approach With Improved Harmonic Performance for Modular Multilevel Converters

In a modular multilevel converter (MMC), the voltage balance among the submodules is mandatory to generate the multilevel stepped waveform across the load and to ensure the equal voltage stress on the semiconductor devices. In addition, the output power quality (voltage and current waveforms) and the converter reliability greatly depend on the design methodology of a voltage-balancing approach. The improper design of the balancing approach causes higher voltage and current harmonic distortion and device power losses, which further affects the efficiency of the MMC. In this letter, an improved voltage-balancing approach is proposed to reduce the output voltage harmonic distortion and device power losses. The performance of the proposed approach is verified through MATLAB simulations and experimentally on a three-level-flying-capacitor-based MMC system. Also, the performance of the proposed approach is compared with the existing methodology to prove its superiority.

Harmonic control using matrix converter of unbalanced input voltage supplied from solar power system

Most of the renewable energy sources are not distributed directly to consumer. It gone through several section to get optimum output voltage and current with the almost zero distortion. Direct Matrix converters are well known of its better power quality and low power distortion to the reactive loads. Conversely, multilevel H bridge inverters are broadly used to attain a sinusoidal output voltage in solar photovoltaic application. Reactive power is subject to high importance for the operation of alternating current (AC) power systems. Moreover there is always a challenge to obtain the balance current control from an unbalanced supply voltage with minimum harmonic distortion for reactive load application from solar power system. The main objective of the proposed system is to maximize the power usage by maintaining the current and power factor nearby unity. There are many different optimization techniques are used so far in matrix converter, a novel method of optimization BAT algorithm is proposed for the power quality to get the best result. This work mainly deals with the compensation of reactive power used in Solar Photovoltaic Power System. Bidirectional energy flow is possible with matrix converter for battery charging. Simulation results are presented to confirm the appropriate operation of the system under different of operating conditions. Also, in the proposed method the percentage of the higher order harmonics can reduced less than 9% of matrix converter for solar photovoltaic application.

Projection to Mixture Families and Rate-Distortion Bounds with Power Distortion Measures

The explicit form of the rate-distortion function has rarely been obtained, except for few cases where the Shannon lower bound coincides with the rate-distortion function for the entire range of the positive rate. From an information geometrical point of view, the evaluation of the rate-distortion function is achieved by a projection to the mixture family defined by the distortion measure. In this paper, we consider the β -th power distortion measure, and prove that β -generalized Gaussian distribution is the only source that can make the Shannon lower bound tight at the minimum distortion level at zero rate. We demonstrate that the tightness of the Shannon lower bound for β = 1 (Laplacian source) and β = 2 (Gaussian source) yields upper bounds to the rate-distortion function of power distortion measures with a different power. These bounds evaluate from above the projection of the source distribution to the mixture family of the generalized Gaussian models. Applying similar arguments to ϵ -insensitive distortion measures, we consider the tightness of the Shannon lower bound and derive an upper bound to the distortion-rate function which is accurate at low rates.

Instantaneous Power Quality Indices Based on Single-Sideband Modulation and Wavelet Packet-Hilbert Transform

Diverse conditions in power systems, such as massive use of nonlinear loads, continuous switching and operation of large electrical loads, and the integration of renewable energies, among others, have adversely affected the power quality (PQ) because they produce undesirable distortions in the waveforms of voltage and current. The conventional way to quantify the PQ is using the PQ indices (PQIs). Yet, the nonstationary properties of voltage and current signals degrade the PQIs estimation whenever classical techniques are used. In this paper, a methodology based on single-sideband modulation method and the Wavelet and Hilbert transforms for the estimation of instantaneous PQIs is proposed. It is shown that the proposal yields better tracking of transitory changes in the voltage/current signals than classical techniques such as the short-time Fourier transform. The PQIs used are the root-mean-square values, frequency, total harmonic distortion, active power, reactive power, apparent power, distortion power, power factor, and total power factor. PQIs performance is validated using synthetic and real signals.

Real-Time Power Measurement Using the Maximal Overlap Discrete Wavelet-Packet Transform

This paper proposes the real-time estimation of the root-mean-square (rms) values, primary power quantities (active, total apparent, nonactive power, and power factor), and distortion power using the maximal overlap wavelet packet transform (MODWPT). The MODWPT provides a uniform frequency band and possesses the time-invariance property, which is ideal for the real-time power estimation. The performance of the proposed wavelet-based power measurement was assessed and compared to the IEEE Standard 1459-2010 in different case studies including stationary synthetic waveforms and power quality disturbances in experimental setup. The proposed method presented good results in the estimation of rms values and primary power quantities by using compact mother wavelets, whereas the estimation of distortion power was better with long mother wavelets.

Broadband signal response of thermo-acoustic devices and its applications.

Thermo-acoustic (TA) transducers are generation of sound speakers without any mechanical vibration system which exhibit an extremely wide frequency response range. In this paper, acoustic field responses to broadband input signals applied to both free-standing and nano-thinfilm-substrate thermo-acoustic devices are developed theoretically by using the Fourier transformation. A series of signals, including single-frequency signal, square root signal, periodic triangle wave signal, and periodic rectangular pulse signal, are applied to these TA devices in simulations and the acoustic pressure responses are investigated. The reproducibility of input signals is predicted. The single frequency results show good agreement with previously published experimental results. Alternative methods for reproducing the original signals with small distortion and low power consumption are introduced. The excellent performance of the TA devices on broadband signal responses will provide a design approach for sound parametric array and underwater communication equipment.

Performance Comparison of PV based Buck Boost and Interleaved Buck Boost Converter Inverter based Solar Systems

The power generated from the nature source such as wind, solar, Biomass etc, plays a vital role in the generation of power. Here we deal with the solar energy resource in inverters as an interleaved buck boost converter. By combining the photovoltaic power system with the inverter and interleaved buck boost converter is used to convert the Direct Current output of the converter as an Alternate Current used single phase inverter. The comparison of the above mentioned systems is done in terms of output power, ripple voltage and Total harmonic distortion.

Study on Third Harmonic Suppression Experiment with Low-Voltage Distribution Power System

To deal with the problem of ever increasing harmonic content in low-voltage distribution power system. A comparative experimental study on limiting the third harmonic current with low-voltage distribution power system in a residential area in Shijiazhuang. We’ve designed an experimental plan to limit the third harmonic under the condition of three-phase four-wire system and measured the impact of the limitation on current, voltage, current distortion rate, active power and distortion power. The results shows that limiting the third harmonic current can notably reduce the distortion power of low-voltage distribution power system and thus improve the electricity quality, but there's no significant power saving effect.

Fuzzy Logic Controller for Three Phase PWM AC-DC Converter

This paper discusses control strategy for the voltage regulation of a three phase pulse width modulation (PWM) AC-DC converter. A fuzzy logic controller (FLC) is employed in the outer voltage loop. Fuzzy logic controllers are preferred over the conventional proportional integral (PI) controllers because they are based on linguistic description and do not require a prior mathematical model of the system. The objective of the presented control system is to regulate the output DC voltage during both transient and steady state period. Also the line currents drawn from the grid should be sinusoidal and in phase with respective phase voltages to achieve a low total harmonic distortion (THD) and unity power factor. PI and FLC based control systems are implemented for three phase PWM AC-DC converter in MATLAB/Simulink and dynamic performance of the system is tested. The results demonstrate that compared to the conventional PI, the FLC based system is more robust and has a much better dynamic response. The low value of THD and sinusoidal current response ensures the system avoids polluting the utility grid.

Generalized LCL-Filter Design Algorithm for Grid-Connected Voltage-Source Inverter

LCL -filters are preferred over conventional L -filters for grid-connected voltage-source inverters (VSIs) due to their superior harmonic attenuation and smaller filter size and weight. The LCL -filter design process is complex and takes an iterative approach due to the considerations of resonance damping, reactive power compensation, harmonic attenuation limits, etc. This paper analyses the parameters of LCL -filter design in order to understand its significance in grid-connected applications. Secondly, based on the analysis, relationships between the resonance frequency, attenuation of switching ripple, reactive power production, and the ratio between the grid-side inductor and the inverter-side inductor are used to realize a simple LCL -filter design algorithm. The design considers LCL -filter as a single filtering unit rather than individual filtering contributions from passive components. The design is verified by simulations in MATLAB and validated experimentally via a hardware prototype. Results demonstrate the efficacy of the proposed method in terms of total harmonic distortion, harmonic attenuation, and reactive power compensated.

Cosmological constraints on exotic injection of electromagnetic energy

We compute cosmic microwave background (CMB) anisotropy constraints on exotic forms of energy injection in electromagnetic (e.m.) channels over a large range of timescales. We show that these constraints are very powerful around or just after recombination, although CMB keeps some sensitivity e.g. to decaying species with lifetimes as long as 1025 s. These bounds are complementary to CMB spectral distortions and primordial nucleosynthesis ones, which dominate at earlier timescales, as we also review here. For the first time, we describe the effects of the e.m. energy injection on the CMB power spectra as a function of the injection epoch, using the lifetime of a decaying particle as proxy. We also identify a suitable on-the-spot approximation, that can be used to derive accurate constraints, and describe its differences with the most up-to-date treatment. Our results are of interest not only for early universe relics constituting (a fraction of) the dark matter, but also for other exotic injection of e.m. radiation. For illustration, we apply our formalism to: i) Primordial black holes of mass 1013.5 g ≲ M ≲ 1016.8 g, showing that the constraints are comparable to the ones obtained from gamma-ray background studies and even dominate below ∼ 1014 g. ii) To a peculiar mass-mixing range in the sterile neutrino parameter space, complementary to other astrophysical and laboratory probes. iii) Finally, we provide a first estimate of the room for improvement left for forthcoming 21 cm experiments, comparing it with the reach of proposed CMB spectral distortion (PiXiE) and CMB angular power spectrum (CORE) missions. We show that the best and most realistic opportunity to look for this signal (or to improve over current constraints) in the 21 cm probe is to focus on the Cosmic Dawn epoch, 15 ≲ z ≲ 30, where the qualitatively unambiguous signature of a spectrum in emission can be expected for models that evade all current constraints.

On the total power factor of lift systems

The term “Total Power Factor” defined as the ratio between the active power and the apparent power (consisting of active, reactive and distortion power) of an electrical system has been used for years to describe how good an electrical supply system is utilized. To a single-phase system, it is well defined. To a balanced three-phase supply system, there is no problem in evaluating it because any voltage between two lines and any line-current could be used to find out the apparent power. To an unbalanced three-phase supply without a neutral wire, like that fed to a modern variable voltage variable frequency lift drive, an issue has arisen. This issue was raised by the first author of this article some 16 years ago. The active power can always be accurately measured by the famous “two-wattmeter method” but which line-voltage and which line-current should be chosen to estimate the apparent power becomes a big issue. The issue is now considered significant, because it was recently required in the mandatory Building Energy Code enforced in Hong Kong. In this article, various existing definitions have been studied and a couple of new definitions have been proposed. Based on cases of computer simulation, one final recommendation has been made, which is simple, straight forward, practical for use on-site and reasonable. It is hoped that this article could solve the problem raised by the first author published in year 2000 in BSER&T and practitioners may find it easy to implement this new definition. It is agreed that such a problem is mainly faced by the Building Energy Code assessors in Hong Kong. Practical application: The measurement of total power factor is a statutory requirement in Hong Kong and is a useful parameter used around the world. Based on site measurements, it is an inherent fact that the currents of the three phase lift systems are not perfectly balanced, whereas the voltages are more or less balanced. And owing to the absence of a neutral wire of the three phase supply to a lift system, it is impossible to measure such total power factor by using the conventional definition. If a neutral wire exists, it is not a problem anymore as the total power factor of each phase can be independently measured. Various definitions have been reviewed and one new definition is suggested that could solve this problem. Lift engineers could easily do the job by adopting this new definition, which is verified by simulation and site measurement.