Three-phase Power System Research Articles

An efficient GBDTRSO control strategy for PV connected H-Bridge Nine Level MLI System with quasi-Z-source inverter

In this manuscript, an extended topology based switched coupled inductor quasi-z-source with nine-level inverter is proposed for three-phase grid-tie photovoltaic power system using hybrid technique. The proposed method is the combined execution of Gradient Boosting Decision Tree (GBDT) and Rat Swarm Optimizer (RSO), hence it is called GBDTRSO method. The major objective of the GBDTRSO method is “compute the performance of photovoltaic system by the maximal power extraction”. Here, the designing of the proposed inverter is optimized to supply the maximal power from photovoltaic power generating system. Besides, the higher voltage gain diminished current ripple switched coupled inductor quasi-Z-source inverter i.e extended boost switched coupled inductor quasi-Z-source inverter topology is proposed. The vital aspects of proposed topology is higher voltage gain, ripple free continual source current, typical ground amid the direct current source and inverter circuit, therefore it is optimized for photovoltaic utilizations. The objective function is deemed depending upon its controller parameters with limits like, power, voltages, current, modulation index. These parameters have been employed to the inputs of proposed method. Ensure the maximal power supply to the load using Gradient Boosting Decision Tree technique in terms of maximum power point tracking. Furthermore, the Rat Swarm Optimizer diminished the feed power and controls the direct current link current, voltage and frequency levels. The proposed technique is activated in Matrix Laboratory (MATLAB)/Simulink platform, also the efficiency is likened with different existing methods. The statistical analysis of proposed and existing methods using energy sources is also analyzed. Finally, the experimental outcomes demonstrate that the proposed method is more efficient than the other existing methods.

Nonlinear Loads Compensation Using a Shunt Active Power Filter Controlled by Feedforward Neural Networks

The shunt active power filter (SAPF) is a widely used tool for compensation of disturbances in three-phase electric power systems. A high number of control methods have been successfully developed, including strategies based on artificial neural networks. However, the typical feedforward neural network, the multilayer perceptron, which has provided effective solutions to many nonlinear problems, has not yet been employed with satisfactory performance in the implementation of the SAPF control for obtaining the reference currents. In order to prove the capabilities of this simple neural topology, this work describes a suitable strategy of use, based on the accurate estimation of the Fourier coefficients corresponding to the fundamental harmonic of any distorted voltage or current. An effective training method has been developed, consisting of the use of many distorted patterns. The new generation procedure uses random combinations of multiple harmonics, including the possible nominal frequency deviations occurring in real power systems. The design of the generation of reference signals through computations based on the Fourier coefficients is presented. The objectives were the harmonic mitigation and power factor correction. Practical cases were tested through simulation and also by using an experimental platform, showing the feasibility of the proposal.

A Method for Responsibility Division of Multi-Harmonic Sources Based on Canonical Correlation Analysis

The variable background harmonic data and incomplete phasor information make multi-harmonic source responsibility division in three-phase symmetrical power system a significant challenge. In this paper, a background harmonic data selection method based on canonical correlation analysis is proposed to deal with multi-harmonic source responsibility division without phasor information. Firstly, the canonical correlation coefficient between harmonic voltage and harmonic current is used to characterize the fluctuations of background harmonic voltage. Then, the sliding window method is adopted to select the harmonic voltage and harmonic current with small fluctuations. Next, the canonical correlation results for selected data are used to calculate the harmonic responsibility index via the linear regression method. The harmonic responsibility index in the form of percentage represents the harmonic responsibility division. Finally, several experimental results demonstrate that the proposed method has a high accuracy in calculating the harmonic responsibility division, particularly when the user side contains fluctuations of unknown harmonic sources.

Fixed switching frequency scheme for current predictive control of DFIG

This paper suggests a new current predictive control algorithm for the wind-driven doubly-fed induction generator (DFIG) based on space vector modulation (SVM) with fixed switching frequency. Combining the current predictive controller and SVM has the benefits of a predictive controller, and fixing the switching frequency improves the output waveform quality. However, if classical predictive control is used, the computational burden will still be high. The proposed algorithm uses SVM to fix the switching frequency of the rotor side converter. Additionally, by using an incremental algorithm, the proposed technique prevents examining all inputs over the prediction horizon. As a result, in the proposed current predictive algorithm the computational time is significantly reduced. The detailed state-space model of DFIG and rotor side converter are used to execute the predictive algorithm. The proposed algorithm uses the rotor current to predict the next behavior of the DFIG, and then, by using SVM, the duty cycles of 2-level voltage source inverter are obtained. Finally, the proposed controller's responses are compared to those of the SVM-based field-oriented control strategy. Simulation results of the proposed controller on a two-level voltage source inverter under a balanced three-phase power system illustrate the satisfactory active and reactive power tracking and improved quality of the inverter outputs.

Power quality improvement in a photovoltaic based microgrid integrated network using multilevel inverter

Abstract The increasing use of power electronics devices as well as the integration of renewable source-based microgrids (MG) has seriously affects the power quality (PQ) of the three-phase power system. Therefore, for the improvement of PQ, it is required to reduce the total harmonics distortion (THD) in the utility network. In this work, the improvement of PQ is discussed in a photovoltaic (PV) based MG integrated three-phase system using a three-level H-bridge (3LHB) multilevel inverter (MI). The MI is used for compensating the source current harmonics and reducing the THD by meeting the IEEE standard guidelines. Besides, the proposed model helps manage the reactive power with control of DC link bus voltage through the PV system. The proposed model is helpful not only in reducing the harmonics but also in providing additional active power to the load if any electrical disturbances occur on the grid side. The maximum power point tracking (MPPT) technique employed in PV is of an improved form of Perturb and Observe (P&O). Further, the reference current generation is derived using the direct current control (DCC) and indirect current control (ICC) techniques. The MG integrated MI is investigated in both DCC and ICC method using three different DC bus voltage controllers; proportional-integral (PI), fuzzy logic controller (FLC), and fuzzy sliding mode control (FSMC). The proposed microgrid integrated system is analyzed with the MATLAB/Simulink tool.

Instantaneous Power Theory For Unbalanced Voltage Compensation Of 3-Phase Power Systems

This paper presents another control technique for a three-phase power systems which depends on instantaneous power hypothesis for unbalanced voltage. In this paper we will dissect power quality issues under distortional and unbalanced voltage conditions, In this methodology, the voltage and source voltages are utilized to create the reference voltages of an arrangement dynamic power channel and source currents are utilized to produce the reference currents of a shunt dynamic power channel. The proposed control approach depends on instantaneous power and is streamlined by utilizing a self-tuning channel, without utilizing any filters or phase bolted circle, and without estimating voltage or channel currents. The presentation of the proposed control approach is assessed regarding power factor adjustment, source impartial current alleviation, voltage adjusting and relief of the current and voltage harmonics of distortional and unbalanced voltages in a three-phase system. Accordingly, the occasions that current is estimated is diminished and system execution is improved. The outcomes got by MATLAB/SIMULINK programming show the viability of the proposed control procedure in contrast with the regular technique.

A total least squares enhanced smart DFT technique for frequency estimation of unbalanced three-phase power systems

In this paper, a robust technique is proposed for the estimation of fundamental frequency in unbalanced three-phase power systems. This is achieved by firstly justifying the modelling mismatch inherently overlooked in the conventional complex-valued least squares enhanced smart discrete Fourier transform method, and then applying the total least squares framework to minimise the error vectors corresponding to both the independent and dependent consecutive voltage measurements and, eventually, to achieve higher immunity to both noise and harmonic pollution. Simulations on both synthetic and real-world noisy unbalanced power systems demonstrate the performance advantage of the proposed algorithm over other smart discrete Fourier transform based ones.

Robust Frequency and Phase Estimation for Three-Phase Power Systems Using a Bank of Kalman Filters

In this paper we propose a powerful frequency, phase angle, and amplitude estimation solution for an unbalanced three-phase power system based on multiple model adaptive estimation. The proposed model utilizes the existence of a conditionally linear and Gaussian substructure in the power system states by marginalizing out the frequency component. This substructure can be effectively tracked by a bank of Kalman filters where each filter employs a different angular frequency value. Compared to other Bayesian filtering schemes for estimation in three-phase power systems, the proposed model reformulation is simpler, more robust, and more accurate as validated with numerical simulations on synthetic data.

Analysis of a geomagnetic induced current on a three-phase power transformer and power system

A geomagnetic induced current (GIC), resulting from adverse space weather, has a low occurrence rate but the potential for high impact events. Such events can disrupt the operation of a power system, especially the power transformer as the current flows in the transmission lines and through the transformer ground points. It is a well-documented fact that a GIC can cause a significant threat to ground-based networks as the induced current can enter into the transmission system through the wye-grounded transformers. This paper presents a simulation of a GIC on an IEEE 9-bus test system under steady-state conditions using PSCAD/EMTDC software. The main focus of this paper is the effects of a GIC on a three-phase power transformer that includes half cycle saturation and reactive power consumption. Based on the simulation results under GIC conditions, the magnitude flux and magnetising current of the power transformer as well as reactive power consumption increase and may lead to power system instability.

A Simple Frequency Estimator for Power Systems

Fast and accurate frequency estimation of an unbalanced three-phase power system in the presence of measurement offset is a challenging task. A simple to implement and tune method is proposed in this work through a delay-based linear-regression framework. Using two challenging scenarios, we verify the performance of our procedure in the presence of severe grid abnormalities, including voltage unbalance, harmonics, frequency jump, and dc offset. Comparative hardware-in-the-loop experimental results demonstrate the suitability of the proposed approach.

Analysis and Simulation of Reactive Power Theory for Harmonic Elimination using Shunt Active Power Filter

A distinct type of load draws non-sinusoidal current from the main supply, which cause harmonic disturbance and reduce the power quality. The major cause of harmonic distortion is this nonlinear load in a power system. In addition, the nonlinear loads causing harmonic distortion can interrelate harmfully with power system equipment, mainly motors, capacitors and transformers causing extra losses. In order to minimise these extra loses due to harmonic disturbance; the shunt active power filters (SAPFs) is investigated to maximize power quality. This paper presents the control method for extracting the reference currents for SAPF using instantaneous reactive power theory (IRPT). It has been evaluated and their performance is brought to a comparison under distorted supply and nonlinear load circumstances. This new speculation gives a general description of IRPT that is applicable for balanced or unbalanced loads and sinusoidal or non-sinusoidal waveforms in three-phase power systems compensation or non-compensation zero-sequence currents and voltages.

Investigation on Amplitude-Domain Modulation for Three-Phase Energy-Stored Quasi-Z Source Inverter

A novel amplitude-domain pulse-width modulation (AD-PWM) technique for three-phase energy stored quasi-Z-source (ES-qZSI) photovoltaic (PV) power system is proposed in this paper. The proposed modulation technique performs switching states and shoot-through behavior based on the relationship of size among three-phase voltages, showing the attractiveness of extreme simplicity and low computation. This paper further investigates the AD-PWM based three-phase PV power system. An active power control method integrated with reactive power compensation for the system in natural coordinate to avoid complicated calculation of trigonometric function. As a result, active power regulation integrated with reactive power compensation is fast and reliable. Compare with the state-of-arts of control schemes for ES-qZSI system utilizing techniques, the proposed control strategy has advantages: 1) The computation is low because there is no shoot-through reference and avoiding complexity vector calculation; 2) there is a reliable capability of ensuring the grid-injected current tracking the grid voltage in phase, owing to the reactive power generated by reactive power equipment is taken into account to control the ES-qZSI’s output current. Simulation and experimental results verify the outstanding features of the proposed AD-PWM and active power control strategy integrated with the reactive power compensation technique for three-phase ES-qZSI PV power system.

An Enhanced IEEE 33 Bus Benchmark Test System for Distribution System Studies

The transformation of passive distribution systems to more active ones thanks to the increased penetration of distributed energy resources, such as dispersed generators, flexible demand, distributed storage, and electric vehicles, creates the necessity of an enhanced test system for distribution systems planning and operation studies. The value of the proposed test system, is that it provides an appropriate and comprehensive benchmark for future researches concerning distribution systems. The proposed test system is developed by modifying and updating the well-known 33 bus distribution system from Baran & Wu. It comprises both forms of balanced and unbalanced three-phase power systems, including new details on the integration of distributed and renewable generation units, reactive power compensation assets, reconfiguration infrastructures and appropriate datasets of load and renewable generation profiles for different case studies.

A Novel Low-Complexity Frequency Estimation Algorithm for Industrial Internet-of-Things Applications

In this article, we present a novel autocorrelation-based frequency estimation algorithm for single-tone sinusoidal signals. In comparison to other state-of-the-art frequency estimation methods, the proposed one provides a better tradeoff between accuracy, complexity, and estimation range. In particular, the algorithm is able to achieve the Cramer–Rao lower bound for moderate and high signal-to-noise ratio, and its implementation is feasible even in resource-constrained microcontrollers, as those commonly used in the Industrial Internet-of-Things (IIoT) applications and low-cost instrumentation. Finally, we investigate the performance of the algorithm in the case of a practical IIoT application, i.e., frequency estimation of unbalanced three-phase power systems, showing that it outperforms several other autocorrelation-based estimators.

Clarke Transformation Solution of Asymmetrical Transients in Three-Phase Circuits

This work deals with the use of the Clarke transformation for the theoretical derivation of circuit models for the analysis of asymmetrical transients in three-phase circuits. Asymmetrical transients occur when only one or two phases of a three-phase power system are involved in a switch operation. Such a condition is critical from a theoretical viewpoint since the Clarke transformation is based on the assumption of circuit symmetry between the three phases. If the symmetry assumption is not met, the equivalent circuits in the transformed variables α, β, and 0 are not uncoupled. The literature concerning numerical approaches for asymmetrical transient analysis is very rich, but a comprehensive and rigorous analytical investigation of circuit models within the framework of the Clarke transformation is still lacking. Contrary to numerical approaches, analytical solutions provide deeper insight into the phenomenon and allow for theoretical interpretation and better understanding of the transient behavior. The proposed circuit models show that the β variables are always uncoupled with α and 0 variables, whereas coupling between α and 0 variables can be properly represented by an ideal transformer. Moreover, in the case of single-line switching, the β variables have no transient, i.e., they keep the steady-state behavior. Transient properties can be readily and effectively observed by representing the trajectory of the space vector on the complex plane. All the analytical results have been checked numerically through the Simulink (Matlab R2020a, The MathWorks, Inc., Natick, MA, USA) implementation of a specific three-phase circuit introduced to illustrate the main theoretical issues.

PSCAD 모델링을 통한 교류철도계통 전압불평형 보상 장치의 유효성 분석에 관한 연구

In AC railway system using single phase power, voltage unbalance for three phase is one of power quality issues. Voltage imbalance affects the life and efficiency of power facilities and devices that receive power from the same three-phase power system. Special transformers are applied to improve these problems, but it does not solve voltage imbalances completely.<BR> In this paper, we present the equation of voltage unbalance factor in system applied with scott transformer based on voltage unbalance factor defined in IEC standard. It then used actual measurement data to analyze the voltage unbalance characteristics. And the modeling for AC railway system, voltage unbalance compensation devices similar to actual site and are performed using PSCAD. The simulation was also performed by load modeling with actual measurement data. Through this, the validity of the improvement of the voltage unbalance using the compensation device is analyzed.

Design and Implementation a New Real Time Overcurrent Relay Based on Arduino MEGA

The relay is very important part of a power system to protect the electrical power system from the disturbances. The new proposed relay is overcurrent relay OCR that be used to protect the devices from any increasing of setting current. The new designs of OCR based on embedded system that used to emulate two characteristics: Instantaneous and Definite Time, The Instantinious work directly without any wait when the current exceed the max current that causes system damage, the other type is working when the passing current exceeded the setting current and at the same time the current continuous in a period of time. The proposed circuit which is used with three-phase power system load depending on the Arduino Mega as a main controller of OCR. The experimental results showed the reliability, sensitivity and flexibility under different operation conditions. This relay was tested on the modern electric system from (Audubon company) to several cases and the results showed the efficiency of the proposed OCR to protect the system.

Improved Frequency Estimation Algorithm Based on the Compensation of the Unbalance Effect in Power Systems

This article proposes a frequency estimation algorithm that effectively cancels the effect of unbalance in a three-phase power system. Precise frequency estimation under unbalance conditions is very difficult to achieve since a negative-sequence component distorts the spectrum of the phasor of three-phase voltage signals. In this article, two parameters of the negative-sequence component are analytically compensated by introducing a modified periodogram, i.e., the phase parameter is removed, and the magnitude parameter is converted into a scaling factor. Rapid and precise frequency estimation is achieved by applying an iterative spectrum peak searching method to the modified periodogram. To verify the performance of the proposed algorithm, computer simulations were performed with various unbalanced and transient reflected signals. The results of the simulations confirm the accuracy and rapid convergence performance of the proposed algorithm.

Modeling and simulation of induction motor based on Time Scale Frame Transformation

The time scale frame transformation is used to construct the analytic signal for single signal, and the large step simulation is carried out after the frequency reduction is rotated. It avoids the double frequency problem of Park transformation when the three-phase power system is asymmetrical, and also avoids the complexity of dynamic phasor method which needs to deal with the asymmetry problem in positive and negative zero order. Based on the principle of time scale frame transformation and the VBR model of induction motor, a time scale frame transformation model of induction motor is established. Then, the time scale frame transformation model of induction motor is programmed by Matlab software, and compared with the electromagnetic transient model of classical induction motor built by Simulink platform. The simulation example shows the accuracy and efficiency of the time scale frame transformation model of induction motor.

Relationship between Buchholz’s Apparent Power and Instantaneous Power in Three-Phase Systems

Similarly to how Steinmetz developed his theory of alternating current in single-phase sinusoidal systems, a few formal relationships between expressions of the instantaneous and Buchholz’s apparent power in three-phase systems were identified in this paper. Based on these relationships, a methodology to express Buchholz’s apparent power and its components in any three-phase, wye-configured system—sinusoidal or non-sinusoidal, balanced or unbalanced—through instantaneous power expressions was established. The application of the proposed method to the entire system allowed the determination of a novel quantity referred to as neutral-displacement power, which measured the impacts of the phenomena caused by the neutral path operation on the values of the source and load apparent power. These impacts were analyzed using a real-world urban installation with a neutral conductor deterioration simulation via an Excel platform as an application example.