Algorithms of packet wavelet transform for power determination under nonsinusoidal modes

Non-sinusoidal voltage in electrical networks is one of the most pressing problems in the field of power quality. In non-sinusoidal modes in electrical networks, in addition to losses of active power at the fundamental frequency, i.e. at the 1-st harmonic, active power losses occur at frequencies that are multiples of the fundamental frequency, corresponding to harmonics from 2 to 40. Additional harmonic active power losses increase losses in electrical networks, creating economic damage for both energy companies and consumers. The paper provides a review of the literature on the topic under consideration. A methodological approach is proposed to assess additional active power losses in overhead power lines. Based on the methodological approach, an analysis of the power quality indicators characterizing the non-sinusoidal mode, measured at the point of connection of 110 kV transmission line to the electrical network, was carried out, additional active power losses were determined.

The article deals with the problem of active power loss and voltage in the 220 kV electric network in the Northern part of the electric system of the Republic of Tajikistan. This problem is caused by the lack of reactive power com pentation in the nodes of the distribution network with a voltage of 10 kV and the transfer of the necessary reactive power to consumers via the electric network with a voltage of 220 kV or lower. In the nodes of the 10 kV distribution network, the maximum values of active and reactive power obtained by calculation are given. To solve the problem of reducing active power and voltage losses, it is proposed to decentralize reactive power compensation by placing reactive power compensation facilities on the 10 kV side. In order to justify the effectiveness of decentralization of reactive power compensation with the installation of reactive power compensation facilities on the 10 kV side, calculations were performed for all high-voltage substations of the Northern electric power system of the Republic of Tajikistan, as well as on the basis of the real existing 220 kV electric network for one node consisting of two transformer substations (TS Sughd - 500 and TS Hadzhent substations), using the Matlab software package, Power Systems built a computer model for optimizing the 220 kV power grid by reactive power.

Optimal load flow normally considers active and reactive power loads as independent of the voltage level. In the paper the exponential form of a static load model relating the active and reactive power components to the busbar voltage, is considered and the effects of incorporating this load model in the optimal load flow solution of several test systems are studied. The effects of modelling active and reactive powers are considered separately as well as when taken together. The results are compared with the respective standard optimal load flow solutions for a number of standard test systems.The differences in fuel cost, total power loss and voltage values when compared with the standard optimal load flow solution are significant for some systems. The fuel cost and power generation differences are the highest when only the active power variation with the voltage is modelled. The heavier the system loading, the lower the fuel cost difference between conventional OPF, and the OPF incorporating power variations with voltages. The differences in power loss are more pronounced when both active and reactive powers are modelled. The higher the loading, the less pronounced the difference in power loss. More significant deviations in voltage take place when both active and reactive powers are modelled. The modelling of reactive power is more influential on the voltages than is the modelling of active power on the voltage deviations. The contrary is true for the differences in phase angle and incremental cost of power delivered, wherein the main factor is active power modelling. There are no differences in iteration numbers for small-size systems. The larger and more heavily loaded systems exhibit a difference in the required number iterations.

A new, simple Digital Signal Processing (DSP) method for investigating dynamic behavior of Power Systems is considered, which combines Integrating Zero Crossing (IZC) and Quasisynchronous Sample Interpolation (QSI). It offers accurate (about 0.001%) and fast (30-40 ms) tracking, estimating and predicting the actual power-line frequency and its deviation, as well as spectral harmonic components of the actual power line voltages and currents with high accuracies (0.02%-0.05%), due to almost complete elimination of aliasing and leakage effects. The results of a computer simulation of this method and of many real-life experiments are given and explained. The proposed method (IZC, QSI) has been compared to other DSP methods used for Power System investigation and applied in Underfrequency Relay Protection (URP); Load Shedding and Restoration (LSR); Acquisition, Monitoring, and Control (AMC); Diagnostics and Quality Analysis (DQA); and in other industrial applications.

The field of advanced digital signal processing methods is one of the fastest developing scientific and technical disciplines, and is important in the field of Shunt Active Power Filter control methods. Shunt active power filters are highly desirable to minimize losses due to the increase in the number of nonlinear loads (deformed power). Currently, there is rapid development in new adaptive, non-adaptive, and especially hybrid methods of digital signal processing. Nowadays, modern methods of digital signal processing maintain a key role in research and industrial applications. Many of the best practices that have been used to control shunt active power in industrial practice for decades are now being surpassed in favor of new progressive approaches. This systematic research review classifies the importance of using advanced signal processing methods in the field of shunt active power filter control methods and summarizes the extant harmonic extraction methods, from the conventional approach to new progressive methods using genetic algorithms, artificial intelligence, and machine learning. Synchronization techniques are described and compared as well.

Due to the increased penetration of distributed generations in distribution systems, transient stability is one of the major concerns to be analyzed. This article presents a support vector machine based approach for transient stability detection using post-disturbance signals extracted from the optimally located distributed generations in a distribution system having distributed generation. Initially, distributed generations are placed optimally, and their optimal sizes are found with objectives of loss reduction and reliability improvement for various distributed generation penetration levels, system configurations, and system loading conditions. Various asymmetrical and symmetrical faults at different locations in the system are simulated to calculate the critical clearing times. The post-disturbance values of terminal voltage, active power, reactive power, and speed obtained from the distributed generations for both stable and unstable cases are used as input features of the support vector machine for finding the transient stability status. The dynamic simulations are carried out on IEEE 33-node and IEEE 69-node radial distribution test systems with four distributed generations, modeled in DIgSILENT power factory software (DIgSILENT GmbH, Germany). The proposed support vector machine based approach predicts the post-disturbance transient stability of the distribution system accurately.

Increasing integration of distributed energy resources (DER) in the electrical network has led distribution network operators to unprecedented challenges. This issue is compounded by the lack of monitoring infrastructure on the low voltage (LV) side of distribution networks at residential and utility sides. Non-intrusive load monitoring (NILM) methods provide an opportunity to add value to conventional electric measurements and to increase the observability of LV networks for the implementation of active management network techniques and intelligent control of DER. This work proposes a novel implementation of NILM methods for the identification of DER electrical signatures from aggregated measurements taken at the LV side of a distribution transformer. The implementation evaluates three machine learning algorithms such as k Nearest Neighbours (kNN), random forest and a multilayer perceptron under 100 scenarios of DER integration. A year of minutely reported values of electric current, voltage, active power, and reactive power are used to train and test the proposed model. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$F_{1}$ </tex-math></inline-formula> scores achieved of 73% and 93% for Electrical Vehicles (EV) and rooftop photovoltaic (PV) respectively and processing times below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$314~\mu \text{s}$ </tex-math></inline-formula> on an Intel Core i7-8700 machine. These results confirm the relevance of the NILM method based on low frequency electric measurements from the real-time identification of DER.

Methods of digital signal processing in control and monitoring systems are relevant today and largely replace the classic analog methods. This article discusses the main methods of digital signal processing and synthesis of appropriate devices, primarily digital filters.

This paper presents a novel power theory with a new construction of power parameters (consisting of apparent (S), active (P) and reactive (Q) power) for sinusoidal voltage supply with linear and nonlinear loads (nonsinusoidal current). This approach decompose every power parameter into two components (fundamental and distortion), each fundamental component is perpendicular on the distortion component. This theory refutes Budeanu's allegations about the reactive power and power factor calculations and some of IEEE standards 1459-2010 assumptions. Moreover, this paper proves that the total active and reactive power is the result of square root the summation of squares of fundamental and distortion components, and not just the arithmetic summation. The new proposed theory proves that the distortion angle (θn) is not just dependent on the total angle (6>t) and on the fundamental angle (θ1), but dependent on the total current (I1) and the fundamental current (I1). Moreover, it shows a new graphical representation of all power components and presents new formulas building the relationship between the total harmonic distortion (THD) and ((θ), (θ1) and (θ1)) phase angles. The new description of power categories has been supported by diagrams, figures and mathematical formulations. In addition, randomly chosen two circuits have been designed and simulated using Matlab-Simulink program in order to test the validity of the new proposed theory in comparing with Budeanu's and some IEEE standard 1459-2010 equations.

In order to analyze non-sinusoidal modes of power supply systems, an accurate determination of parameters for these modes is required. Effective values of currents and voltages are among these parameters. The work is based on the wavelet transform, which allows the values for these parameters depending on each harmonic component to be accurately defined without losing data in the time domain. The power supply system under the non-stationary and non-sinusoidal operation mode is considered in the paper. Analysis of higher harmonics influence from non-linear sources of 6 kV on losses in electric power lines is performed. In particular, effective values of currents and losses in the 6 KV line for each harmonic component separately are calculated. The results obtained by the wavelet-transform are compared to the results obtained by the Fourier transform and analytical calculation. As a numerical experiment a simulation model of the network with a non-linear, non-stationary load is developed in the environment of MATLAB Simulink.

Wound-rotor induction generators have numerous advantages in wind power generation over other types of generators. One scheme is realized when a converter cascade is used between the slip-ring terminals and the utility grid to control the rotor power. This configuration is called the doubly-fed induction generator (DFIG). In this paper, a vector control scheme is developed to control the rotor side voltage source converter that allows independent control of the generated active and reactive power as well as the rotor speed to track the maximum wind power point. A neuro-fuzzy gain tuner is proposed to control the DFIG. The input for each neuro-fuzzy system is the error value of generator speed, active or reactive power. The choice of only one input to the system simplifies the design. Experimental investigations have also been conducted on a laboratory DFIG to verify the calculated results.

In this paper, a comparative study is carried out on the six new switching tables and the conventional switching table of the direct power control (DPC) for voltage source rectifier (VSR). On the basis of the mathematical model for VSR, the expressions for variation of active and reactive power are obtained. In order to minimize the errors between the command and the estimated values of active and reactive power, the appropriate rectifier voltage vectors are selected. Six new switching tables are constructed accordingly. Compared to the conventional DPC, significant power ripple reduction and more sinusoidal line input current can be observed in the six new DPCs. A further comparative investigation is conducted among the six DPCs. Simulation and experimental results validate the effectiveness of the presented DPCs.

A method for allocating var support based on branch's complex power components is presented. First it is pointed out that source's active power and load's complex power should be responsible for var support based on analysis. Then each of source's active power and load's complex power is modeled by its equivalent nodal injection current sources based on reactive optimal power flow (OPF) solution. Each of source's reactive power used for var support is modeled by a shunt reactance called cost reactance. Finally, the nonlinear relationship between resistance and equivalent injection current sources is established based on the algorithm of branch's complex power components. As a result, var support of each reactance is accurately allocated between source's active power and load's complex power. The proposed method is of the following properties by comparison with the existing methods: The var support of a power system is always recovered; It is applicable for any transmission systems of looped configurations and loop flows; It needs no any assumption and simplification, and takes into account the interaction between active and reactive power; The proposed method gives a completely novel and analytical way of allocating var support cost. Simulation results of different power networks show that the proposed method is effective.

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&amp;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.

PurposeAt the current stage of electrical technology development, it is relevant to take into account the quality of electrical energy. It can be implemented if an assessed energy quality indicator is available. The amount of electrical energy is determined by active power, which is transmitted over a certain time period. In some cases, reactive power is included in the metering system. The distortion power is justifiably criticized and is not taken into account. The purpose of this paper consists in the substantiation of the indicator of the distortion of the periodic polyharmonic current electrical energy power, by separating from the instantaneous power such harmonics, which formed by same frequencies current and voltage harmonics.Design/methodology/approachUsing the method of calculating linear polyharmonic current circuits, the following quantities are identified in instantaneous power: active, reactive and apparent powers of each harmonic. These components are known from references as canonical.FindingsBy the method of instantaneous power harmonic analysis, the components formed by current and voltage harmonics of the same frequency and different frequencies are distinguished.Research limitations/implicationsThe RMS value of the instantaneous power due to current and voltage harmonics of different frequencies is justified in the work. This quantity allows you to distinguish the instantaneous power distortion level in comparison with the existing quantity.Practical implicationsThe results can be used to assess the level of instantaneous power distortion level in commercial and technical metering systems.Originality/valueThe definition of instantaneous power distortion by extracting the canonical components from it and determining the root mean square value of the remainder is proposed.