Electrical power components decomposition of periodic polyharmonic current

Purpose. Based on the instantaneous electrical power of a three-phase asymmetric system of sinusoidal periodic current, to determine positive, negative, zero-sequences active and reactive power, as well as invariance power factor. Methodology. In the unbalance case in three-phase electrical system, the electrical energy quality is evaluated by means on voltage and current positive, negative, zero-sequences. At the same time, similar components of active and reactive power have not received practical distribution. But it is precisely in terms of power that electricity is accounted for. The instantaneous power orthogonal components in the time domain are determined using the symmetrical components of voltage and current. Active, reactive powers of positive, negative and zero-sequences are allocated. The result obtained has the property of representativeness, which most of the known results lack. Findings. The three-phase system’s instantaneous power components are analytically determined, including the amplitudes of the oscillating power components. The need to take into account the oscillating instantaneous power components has been proven by means of a graphical interpretation of a special case of the three-phase system mode. As an integral indicator that takes into account the oscillating components of the three-phase system instantaneous power, its root-mean-square value over the repetition period is used. Originality. By calculating the transformer efficiency of the studied model according to the active power positive sequence and the same indicator according to the active power as a whole, it was established, that the component sequence separation affects the results of calculating the generalized indicators, including the power transmission system objects. This can lead to erroneous judgments about the efficiency of the specified facilities functioning. Practical value. The invariance power factor was used to characterize the electrical energy quality level of a three-phase sinusoidal current system in an unbalanced mode.

This paper reports a novel strategy for analysing a single phase power system feeding a non-linear load. This strategy is based on a new theory to transform the traditional single phase power system into an equivalent two-axis orthogonal system. This system is based on complementing the single phase system with a fictitious second phase so that both of the two phases generate an orthogonal power system. This would yield a power system which is analogous to the three phase power system but with the phase shift between successive phases equal to pi/2 instead of 2pi/3. Application of this novel approach makes it possible to use the complex or Gauss domain analytical method in a similar way to the well known method of instantaneous reactive power for three phase power system instigated by Akagi et al in 1983. Thus, for the fictitious two-axis phase power system, the concept of instantaneous active and reactive power could be instigated. Moreover, the concept of instantaneous power factor could be defined. The novel strategy of power system analysis outlined in this paper is applied to a single phase power system feeding a non-linear load in conjunction with an active power filter. The latter serves the purpose of compensating for either of the instantaneous reactive power or the harmonic current distortion in the single phase power system under investigation or for compensating of both. Experimental results demonstrated the effectiveness of the novel single phase power system analysis reported in this paper.

In electrical engineering, there are several power terms; active power, reactive power, instantaneous active power, instantaneous active power, instantaneous power, apparent power and complex power. Even though are used in daily activity, electrical practitioners are facing difficulty to explain those terms practically. This paper tries to solve those difficulty by interpret those term in practical way. Firstly, each power term are defined theoretically. Then those terms are presented mathematically. Next, power in single phase sinusoidal electric network is analyzed. Theoretical definition result is connected with power analysis result. Computer simulations are held to strengthen interpretation result. Considering the width of discussion area, this paper only covers most general application, that is single phase sinusoidal network.

This paper explores the feasibility of multilevel dual-active bridge-inverter (DABMI) applications for grid-connected applications of a modern Model of Predictive Direct Power Control (MPDPC) based on the conservative power theory (CPT). In the case of unbalanced grid voltages, the objective of the study is to promote continued active and reactive energy in MPDPC without reducing efficiency such as transient response and current harmonics. The nature of the instantaneous p-q theory permits only one out of three control targets to be fulfilled. The proposed control approached directly regulates the instantaneous active and reactive power to achieve three particular control objectives namely sinusoidal and symmetrical grid current, cancelling twice of fundamental grid frequency reactive power ripples, and removing twice grid frequency active power ripple. The techniques of complicated Grid part sequence extraction are unnecessary and improved at no extra expense, as is the case with current MPDPC fault-tolerant approaches. The instantaneous power at the next sampling instant is predicted with the newly developed discrete-time model. Each possible switching state will then be evaluated in the cost function defined until the optimal state which lead to the minimum power errors is determined. In MATLAB/Simulink simulation, the proposed CPT-based MPDPC measures reliability and performance at balanced and unbalanced grid voltages then compared with the conventional and existing MPDPC The proposed method manages to achieve all of three control targets which generates sinusoidal grid currents and attenuates active and reactive power ripple of twice the grid frequency exactly at the same time without losing its critical efficiency including transient reaction and current harmonics.

A correct definition of mode parameters is of great importance for examination of power quality indices under non-sinusoidal modes, these parameters being effective values of current, voltage, active and reactive power. A wavelet transform is a later method of digital signal processing. This method enables information about signal to be saved both in amplitude-frequency and time space. The technique of defining effective current values of non-sinusoidal transient mode is presented. This technique assumes the preliminary frequency decomposition of the examining signal using the packet wavelet transform. Modernization of existing mathematical models of instantaneous, active and reactive power calculation as well as distortion power under non-sinusoidal modes based on the packet wavelet transform is carried out. The comparison of simulation modeling results shows qualitative coincidence with analytical mode calculation.

In this paper, grid connected DSTATCOM with three phase three wire has been proposed for harmonics elimination, reactive power compensation and active power injection into the grid. An improved instantaneous reactive power theory based on the least mean square is computed. The least mean square (LMS) algorithm is combined with instantaneous reactive power theory (IRPT) to improve its dynamics performance and eliminates the use of low pass filter requirement for computation of reference current. The harmonics component of the active power is estimated from LMS algorithm generated load harmonics currents. The performance characteristic of DSTATCOM is estimated with control scheme using computer simulation. The technique is based on the instantaneous transformation of instantaneous signals and taking advantage of the subsequent calculation of power from supply side to the loads. The neural network based method to estimate the harmonic online, DSTATCOM can compensate the harmonics. The computer simulation is carried out with MATLAB Simulink power system block sets.

Aiming at the unreasonable phenomenon that the different harmonic power will be cancelled out in the current harmonic background, a harmonic energy measurement algorithm is proposed to improve the instantaneous reactive power. First, the three-phase voltage and current signals are constructed by the delay of single-phase voltage and current signals. Then by changing the rotational speed of the p-q coordinate system in the instantaneous reactive power theory, the signals of different frequency harmonics in the voltage and current are obtained after filtering. Finally, the active power and reactive power of the system are obtained by the power conversion. This method can not only measure the power in positive and backward separately, but also avoid the unreasonable phenomenon of the positive and reverse power offset when the electric energy is measured, and can be used in the single phase system and the three-phase system. Finally, the simulation results of Matlab verify the effectiveness and accuracy of the proposed method.

This paper deals with the presentation of different terms of the powers presented in the Instantaneous Reactive Power Theory (IRPT) in the general case of a generic power system voltage. This presentation is based on the use of the symmetric components in the E. Clarke stationary frame, where the instantaneous real active power, the instantaneous imaginary reactive power and the instantaneous zero sequence power are divided into their DC components and AC components function of the symmetric components. The contributions of these terms in the transfer of the energy from the power supply to the load in four wire system are explained, hence, a good choice of the power to be compensated using shunt active power filter can be obtained. Finally, simulation results are presented under unbalanced and distorted generic power system voltages, where different terms of the instantaneous reactive power theory are clarified and presented based on symmetrical components.

Introduction. Recently, photovoltaic (PV) systems are increasingly favored for converting solar energy into electricity. PV power systems have successfully evolved from small, standalone installations to large-scale, grid-connected systems. When the nonlinear loads are connected to a grid-tied PV system, the power quality can deteriorate due to the active power supplied by the PV array, there’s a noticeable decline in the quality of power delivered to consumers. Its combination with the shunt active power filter (SAPF) enhances system efficiency. Consequently, this integrated system is adept at not only powering local loads but also at compensating for reactive power and filtering out harmonic currents from the main grid. The novelty of the work describes how an operation of a small scale PV system connected to the low voltage distribution system, and nonlinear load can be achieved, the investigation aims to analyze the system’s behavior and elucidate the advantages of employing various control algorithms. These proposed algorithms are designed to ensure a unity power factor for the utility grid while prioritizing high convergence speed and robustness against load power fluctuations across different levels of solar irradiation affecting the PV modules. The purpose of this work is to enhance the dynamic performance of the SAPF by cooperatively using a self-tuning filter (STF) based instantaneous active and reactive power method (PQ) with a novel predictive current control, enhance the system resilience, ensure optimal management of the total active power between the PV system, the electrical network and the non-linear load by integrating the functionalities of the SAPF under different levels of solar irradiation and maintain the DC-link capacitor voltage constant. Methods. A novel predictive current controller is designed to generate the switching signals piloted the three phase source voltage inverter, also a novel algorithm of instantaneous active and reactive power is developed, based on STF, to extract accurately the harmonic reference under non ideal grid voltage, also the perturb and observe algorithm is used to extract, under step change of solar irradiation, the maximum power point tracking of the PV module and the PI controller is used to maintain constant the DC-link capacitor voltage of the SAPF. Results. The efficacy of the proposed system is primarily centered on the grid side, and the performance evaluation of the control system is conducted using the STF based PQ algorithm and predictive current control. In addition, comprehensive testing encompasses all modes of operation, including scenarios involving distorted voltage sources, step changes in solar radiation, and variations in nonlinear loads. Results highlight superior performance in both transient and stable states, affirming the robustness and effectiveness of the proposed controllers. Practical value. The total harmonic distortion value of the grid current for all tests respects the IEEE Standard 519-1992. References 21, tables 7, figures 25.

This paper deals with the problem of the early stator (the short-circuits) and rotor (broken bars) faults detection of the induction motors supplied from the frequency converter. The method basing on the FFT algorithm is used for the spectral analysis of the instantaneous active power, the instantaneous reactive power and the estimated electromagnetic torque. These signals are on-line calculated, basing on the measured currents and voltages of the motor. Computations of the instantaneous active and reactive power use the theory of the electric power for non-sinusoidal power systems. In this paper results of laboratory investigations for low power motor with modeled stator short-circuit and broken rotor bars are demonstrated. Tests were realized for different supply frequencies, what enabled the evaluating of the usefulness of the proposed analysis in the diagnostics of the stator and rotor faults in the converter-fed induction motor drives.

Cogeneration is defined as the simultaneous production of electricity and useful thermal energy. This production of electricity and thermal energy from the common source is more efficient than separate production of thermal energy and electrical energy. Because of the need for both thermal and electrical energy, cogeneration systems have been a part of industrial energy systems since early in this century. In fact, until the early 1950s, over half of industrial electrical energy use was produced from cogeneration systems. A favorable balance between thermal energy needs and electrical needs exists in many industries, and this balance serves as the driving force for the use of cogeneration systems. Several things led to the change of balance between the thermal and electrical requirements of industry which led to a general decline in the use of cogeneration over the next thirty years. The increase in the amount of electrical energy in the energy equation and the development of industry without associated thermal requirements were major factors in the development of a market for electricity from central generating plants. These large special-purpose generating plants could approach the efficiency and cost of cogeneration plants because of economies of scale and the variety of fuels acceptable in these plants. The availability of electricity from utilities at a reasonable price, combined with low fuel prices, allowed efficient plant operation independent of a balance between thermal and electrical energy. This reduction in the use of cogeneration systems in industrial plants continued into the early 1970s when the Arab oil embargo caused a precipitous rise in the cost of fuel and reduced growth of electrical use, new environmental restrictions and inflation began to eat into the economies of scale that had been realized with the construction of larger and more efficient electrical plants. Paper published with permission.

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.

The International Thermonuclear Experimental Reactor (ITER) is now implemented with Tokamak which requires about 1 GVar reactive power to compensate its power system for superconducting magnets where about 0.2 GVar is transferred from France Electrical Power Network, the other 0.75 GVar is generated by the system of Reactive Power Compensation and Harmonic Filtering, the Static VAR Compensator (SVC) configuration. ITER can experimentally generate 500 MW fusion thermal power in 400 s long pulse mode with about half of its construction area is for its power suppliers. It could only generate about 500 MW/3=167 MWe active electric power if it is to be configured with pressured water reactor due to that it is only about 1/3 conversion efficiency from thermal energy to electric energy. For such fusion machine, the requirement for reactive power is much larger than the active power it generates. Based on this requirement, one compact pulsed synchronous generator is suggested for this purpose. It can not only generate the fundamental reactive power to compensate and stabilize the power network, but also the active power for putting power on the grid. Due to its two purposes in one device configuration, it becomes cheap and reliable by implement it in the design of future fusion power plant for demonstration. Some consideration has been done to the special synchronous generator, which is intended for the concept design of Chinese Fusion Engineering Testing Reactor, targeting the compact Electric Power System for superconducting Tokamak.

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.

This work deals with the design, analysis and simulation of shunt active power filter SAPF, which compensate harmonic currents, and reactive power under balanced supply network. An optimal control theory for currents compensation based on particle swarm optimization is developed in this paper. The SAPF is connected in parallel with a nonlinear load which has caused current harmonics in industrial power plants and utility power distribution systems. The proposed optimal PI current controller using particle swarm algorithm determines the switching signals of the SAPF, and the algorithm based on instantaneous power (pq) theory has been used to determine the suitable current reference signals. The simulation results show that the new control method using PSO approach is not only easy to be implanted, but also very effective in reducing the unwanted harmonics and compensating reactive power. The studies carried out have been accomplished using the MATLAB Simulink Power System Toolbox.