Single-phase Power Research Articles

Third-Harmonic-Type Modulation Minimizing the DC-Link Energy Storage Requirement of Isolated Phase-Modular Three-Phase PFC Rectifier Systems

A three-phase ac/dc converter with high-frequency isolation can be realized as a monolithic three-phase or as a phase-modular system by combining three single-phase Power Factor Correction (PFC) rectifier modules with individual isolated dc-dc converters. Advantageously, for a phase-modular system the module configuration can be changed depending on the instantaneous input-output voltage ratio (i.e., a star-(Y)- or a delta-(Δ)-arrangement such that wide voltage ranges can be covered without a massive over-dimensioning of the main power components. However, the main disadvantage of a phase-modular converter realization is the fact that the input power of each PFC rectifier module pulsates at twice the mains frequency (which is inherent to single-phase power conversion) such that large dc-link capacitors are required. Recent literature predicts a substantial power pulsation reduction enabled by means of third-(3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> )-harmonic injection modulation which is applicable for the Y-connection (where a common-mode (CM) / zero-sequence (ZS) voltage is injected), and for the Δ-connection of the three single-phase PFC rectifier modules (where a CM / ZS current is injected). This changes the distribution of the power flow in the three-phase system and the power pulsation is shifted to higher frequencies. This paper experimentally verifies and extends the dc-link energy storage requirement reduction of the 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> -harmonic injection modulation concept: In a first step, the derivation of the harmonic injection concept is recapitulated and suitable control methods are discussed for both CM voltage (Y-arrangement) and CM current (Δ-arrangement) injection. Further, an alternative CM voltage injection strategy with simplified reference generation based only on the instantaneous grid voltage measurements is presented and compared to the pure 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> -harmonic injection modulation. Measurement results obtained from a 6 kW prototype reveal a dc-link voltage variation and/or energy buffering reduction by up to 38.6 % enabled by the harmonic injection modulation compared to conventional operation without 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> -harmonic injection modulation.

An experimental study of surge protection in smart meter installation in the residential sector

This paper aims to construct an experimental system using the Arduino UNO microcontroller board to measure the electrical quantities and protect against surge circumstances in a single-phase power supply. The system utilized a voltage sensor and a current sensor, and data was transferred to a personal computer for graphical examination. The Root Mean Square (RMS) method was used to measure electrical values, and the system is allowed to decide whether to turn the load on or off based on the comparison of RMS voltage measurement to the lowest and maximum voltages. The Telemetry Viewer v0.5 software was used to create the monitoring interface, which monitored the system's RMS voltage, RMS current, active power, and trip signal.

Single Phase Harmonic Mitigation Using Particle Swarm Optimization in Shunt Adaptive Power Filter

Purpose – These load sources are the main cause of generating harmonics, generating power loss in the transmission system and electrical equipment system, as well as reducing the life of electrical equipment, reducing the accuracy of electrical measuring devices, and reducing the signal transmission of communication devices. Methodology/Approach – This study applies the Particle swarm optimization (PSO) algorithm to DC-link capacitor voltage control based on the Proportional-integral (PI) control algorithm to determine the reference current. MATLAB/Simulation 2019a is used to simulate research results. Findings – The harmonic compensation performance of the SAPF circuit gives good results and meets the standard for total harmonic distortion (THD) of less than 5%. Originality/Value of paper – Bridge rectifiers with RL load and Non-linear load with active RC are applied in a single-phase power supply. The single-phase voltage source inverter is used to shunt the adaptive power filter (SAPF) to compensate for reactive power and current harmonics.

DC-Link Capacitance Reduction in PFC Rectifiers Employing PI+Notch Voltage Controllers

It is well-known that adding a notch filter in series with the typically employed type-II (or PI) regulator allows improving the tradeoff between dc-link voltage dynamics and grid-side current total harmonic distortion (THD) in practical single-phase power factor correction rectifiers. The article demonstrates that notch filter utilization alternatively allows reducing the value of dc-link capacitance in case hold-up time requirement is absent. The revealed value of minimum capacitance is expressed by explicit function of possible mains frequency values range, maximum expected grid voltage magnitude, rated system power, dc-link voltage set point, maximum tolerable grid-side current THD, and the desired phase margin (PM) of dc-link voltage loop. It is demonstrated that the proposed approach yields fourfold reduction of dc-link capacitance for typical values of 5% tolerable grid-side current THD under 40° PM constraint. Experimental results exhibit close-fitting resemblance to corresponding analytical predictions, verifying the proposed methodology.

Performance analysis of Newton-Raphson Power flow computations based on Power and Current Mismatches

This work studies the performance of single-phase power flow computations implemented using vector-based Python scripting language. Two approaches are considered, namely the current mismatch and power mismatch based on Newton-Raphson method. Both approaches are developed using rectangular coordinates and tested through a variety of IEEE test systems modelling high voltage transmission networks. The computational burden and accuracy of both implementations are duly discussed. This work will be later incorporated into our vector-based Non-linear Primal-Dual Interior Point Method as constraints.

Application of Three-Phase Power Flow Analysis to the Nigerian Distribution Networks

Single-phase power flow analysis is used to study most distribution networks in Nigeria. The use of single-phase-power flow analysis assumes that the network is balanced and that the conductor phases act identically. However, Nigerian distribution networks are highly imbalanced because of untransposed lines, irregularly distributed loads in conductor phases, mismatched conductor sizes, and spacing. Consequently, single-phase modeling of the networks fails to reflect actual network behavior, resulting in an incorrect power flow solution. This research presents the three-phase modeling of radial distribution networks for a three-phase-power flow study of Nigerian distribution networks. Olusanya's 54-bus and Ajinde's 62-bus distribution networks in Nigeria were evaluated, both of which were very imbalanced. Without making any assumptions about the network components, these two distribution networks were properly modeled. Each network's three-phase power flow study was carried out in the MATLAB environment. The power flow solutions for each network demonstrated unevenness in the voltage profile for each network phase, as well as inequality in the real and reactive power losses in each phase, indicating that the deployed three-phase-power flow analysis properly mirrored the underlying network characteristics. Therefore, applying three-phase power flow analysis to distribution networks is critical for proper assessment of distribution network performance.

Анализ возникновения бросков магнитного потока и намагничивающего тока при включении трансформатора на холостом ходу

This article discusses the transients that occur in power transformers when they are turned on at idle. The main negative consequences arising from magnetizing current surges and their impact on the quality of electrical equipment, in particular, false alarms of relay protection devices and deformation of transformer structural elements by electrodynamic forces, are given. The mathematical derivation of physical quantities determining the process of occurrence of magnetic flux and magnetizing current surges is presented on the example of switching on a power single-phase transformer in idle mode. As a result of mathematical analysis, the main factors affecting the flow of the transient process when the power transformer is switched on in idle mode were identified. A mathematical expression was obtained that allows determining the phase of the mains voltage for a favorable moment of switching on a single-phase transformer, depending on the magnitude of the residual magnetic flux in the steel core of the transformer. Based on the analysis of transients that occur when transformers are switched on at idle, methods or algorithms for switching on power transformers can be developed that allow for a smooth start of the transformer and avoid or minimize negative consequences.

A brief review on hardware structure of AC electric spring

&lt;span lang="EN-US"&gt;Decarbonizing power generation and reducing greenhouse gas emissions require renewable energy sources. Intermittent nature of renewable energy sources can cause blackouts, fluctuation in voltage, grid-connected inverter usage, inability to predict power generation, fluctuations in voltage and frequency. It is possible to balance between the supply and demand of power to overcome these problems by using an electric spring (ES). It is necessary to study its work, types, and controlling actions for realizing the benefits of the electric spring. This paper reviews the hardware structure of an ES based on voltage-source inverter (VSI) and current-source inverter (CSI) topologies, in single-phase and three-phase AC power distribution systems with renewable energy sources. The structure, control strategies, operating modes, advantages and disadvantages of each ES topology are elaborated to make it a suitable alternative for resolving different power quality issues caused due to the high penetration of renewable energy sources.&lt;/span&gt;

Active Thermal Control for Buck Converter-Based Active Power Decoupling Circuit

Aluminum electrolytic capacitors (AECs) and power semiconductor devices (PSDs) are typically identified as weak links in the reliable design of power converters. To eliminate the AECs from the design, active power decoupling (APD) circuits are preferred in single-phase power converters. However, in an attempt to eliminate AECs, this approach introduces the latter weak link in the design, i.e., PSDs in the APD circuit. This article proposes an active thermal control technique to improve the reliability of PSDs in the buck APD circuit. The proposed technique reduces the swing in junction temperature of PSDs using noninvasive power loss modulation. The power loss in PSDs is changed by varying the average voltage across the buffer capacitor. Further, a control technique is suggested to synthesize the reference for average voltage across buffer capacitor. This controller accounts for nonlinearities and minimum/maximum limits of power loss modulation. Further, the additional energy loss due to power loss modulation is restricted to a predefined limit. The proposed technique is validated with the help of circuit simulations and experimental studies with a 500 W laboratory prototype. For the selected mission profile, an increase of 28.5% in the lifetime of PSDs in buck APD circuit is estimated.

Method of calculation of electromagnetic torque and energy losses of three-phase induction motors when powered by a regulated single-phase voltage

Introduction. Single-phase power supply of induction motors is used in public utilities, in microclimate control systems for remote agricultural consumers, in water supply and pipeline transport systems, etc. In practice, there is the use of induction motors with three-phase stator winding in the conditions of single-phase power supply. Starting and operating capacitors are used to enable their operation when powered by a single-phase network. Problem. There are many fairly accurate methods for calculating the characteristics of an induction motor in asymmetric, including single-phase, modes of operation, but they are based on differential equations, which does not allow to obtain analytical expressions for preliminary analysis and synthesis of such systems. Goal. The purpose of this article is to develop the analytical method of definition of electromagnetic torque and energy losses of voltage-regulated three-phase induction motors working according to the scheme of single-phase inclusion with the phase-shifting capacitor. Methodology. The method is based on the theory of symmetric components and analysis of replacement schemes of induction machine in motor and generator modes. Results. The analysis of the obtained data shows that at a constant value of the phase-shifting capacitor capacity induction motor working according to the scheme of single-phase inclusion has a minimum of losses at one value of slip at different values of supply voltage. Therefore, if you keep this slip constant when the load changes, you can achieve a mode of minimizing losses at a constant value of the capacity, optimal for this slip. This shows that the thyristor voltage regulator can be used as an energy-saving element under variable load, while the capacitance of the phase-shifting capacitor can remain constant when changing the load in a wide range provided that this slip is stabilized. Originality. The developed method allows to obtain analytical expressions for comparative analysis of electromagnetic torque and energy losses of three-phase induction motors powered by a single-phase network at different values of the capacity of the phase-shifting capacitor, supply voltage for different variants of schemes for including three-phase induction motors in a single-phase network. Practical value. Based on the developed analytical method, the optimal parameters of phase-shifting capacitors and rational schemes for including three-phase induction motors in a single-phase network can be determined.

A new digital phase estimation technique based on centroid formula

Synchronization is a crucial aspect of grid-connected converters. Grid voltage amplitude, frequency, and phase are the most important parameters that have to be estimated in order to inject current with unity power factor. Compared to three-phase power systems, the estimation of these parameters for single-phase grids is more challenging since less information is available. This paper presents a novel approach to estimate the phase angle of a sine wave signal. This approach, based on computing the x-coordinate centroid formula, does not require a synchronous reference frame, a quadratic signal generator, or an amplitude estimation of the input signal. An application of this method for single-phase power systems is proposed. Experimental comparisons with other popular techniques under different test scenarios such as phase jump, frequency jump, harmonic distortions, and DC offset show that the proposed method gives satisfactory performances in terms of dynamic response and robustness.

Design and Analysis of Zeta Converter for Power Factor Correction Using Cascade PSO-GSA-Tuned PI and Reduced-Order SMC

This paper presents the design and analysis of a single-phase power factor correction (PFC) scheme using a DC–DC Zeta converter operating in continuous conduction mode. The presented DC–DC converter exhibits non-linearity due to switching elements that degrades the performance of the converter. Therefore, this paper proposes a non-linear cascade control of particle swarm optimization-gravitational search algorithm (PSO-GSA) tuned proportional-integral (PI) and sliding mode controller (SMC) in outer and inner loop, respectively, to improve the performance of the converter. The robustness of the controller is analysed by applying the load and line variations to the converter. The simulation results showed that the steady state performance indices such as integral absolute error and integral square error, and transient performance indices like settling time and peak overshoot are significantly enhanced for the proposed cascade control scheme compared to the PSO and root locus method of tuning the outer PI with the inner SMC controller. The proposed control scheme gives better performance in terms of power factor improvement, percentage reduction in total harmonic distortion, and efficient tracking of output voltage for change in reference voltage compared to other techniques presented. Further, the performance of the proposed scheme is tested for battery charging application of the solar photovoltaic system. The demonstrated simulation results are validated by implementing the DC–DC Zeta converter in real-time hardware set-up.

Bidirectional Buck-Boost converter as an Active Power Decoupling schema for Single-Phase Power Inverters

The power ripple in the DC-link of photovoltaic and energy storage systems interconnected to the AC mains can drastically impact the lifespan of the photovoltaic panel and the system in general. This problem can be easily solved by using DC-link electrolytic capacitors as a passive decoupling method; however, this implies significant drawbacks such as increased volume and cost of the capacitor and a significant reduction in efficiency and reliability. This can be compensated by replacing electrolytic capacitors with active power decoupling methods based on power electronic converters. Thus, a Bidirectional Buck-Boost converter as an active power decoupling scheme is proposed. First, a power decoupling overview is addressed. Afterward, the operation of the Buck-Boost converter is detailed. Therefore, the control strategy is also explained. Finally, some simulations and preliminary experimental results to verify the integrated operation of the power converter are given.

Multi-objective optimum design of five-phase squirrel cage induction motor by differential evolution algorithm

Compared with the traditional induction motors, five-phase squirrel cage induction motor (FSCIM) have the advantages of lower torque ripple and single-phase power, flexible control strategy, higher power density and fault-tolerant operation, which has been widely applied on electrical vehicles, rail transit, underwater vehicles and so on. This paper presents an analytical design optimization method based on the coupling of electromagnetic equivalent circuit (EEC) and differential evolution algorithm (DEA). Furthermore, the difference between three and five-phase winding on harmonic specific leakage permeance is investigated in detail. The nonlinear and oeolotropic influences of design geometrical parameters (slots openings, main dimension ratio, yoke height, airgap length, etc.) on the performances of the basic FSCIM model are evaluated with analytical model. For more accurate results, the harmonic characteristics of five-phase winding structure, iron core saturation, rotor slot skew width, stator end winding, slot leakage inductance and stator and rotor slot structure are considered. Meanwhile, the efficiency, power factor, maximum torque, slot fill factor and material consumption of FSCIM are calculated as the comprehensive objective function. The transient finite element analysis (TFEA) and experimental test verify the accuracy of the proposed optimum model. In addition, the feasibility of the multi objective optimization design scheme provided by the analytical model is verified by TFEA.

A Passive Islanding Detection Method for Distribution Power Systems With Multiple Inverters

The high penetration of grid-connected distributed energy resources (DERs) leads to a need for smart inverters to enhance their performance and minimize the negative impacts of these resources on grid behavior. However, the interconnection of these smart inverters may interfere with their anti-islanding algorithms, which creates detection difficulties. Advanced islanding detection techniques are therefore required to detect and disrupt islanding operations under such an environment with system’s disturbances and interferences. Even though various islanding detection methods have been developed in recent literature to identify islanding operations with high detection accuracy and minimized nondetection zone, these methods mainly focus on a single inverter system, which is incompatible in modern power system with high penetration of grid-connected inverters. In this article, an advanced passive islanding method is proposed for a single-phase distribution power system taking account of the interferences and disturbances brought by these grid-connected inverters. The effectiveness of the proposed passive islanding method is validated through experiments in a laboratory platform. Also, the experimental results have verified that the proposed methods can effectively terminate the islanding operation even with rich inverters’ interferences.

A new virtual oscillator control for synchronization of single-phase parallel inverters in islanded microgrid

ABSTRACT This paper describes the concept of virtual oscillator control (VOC) for parallel-connected single-phase inverters (SPIs). The principal idea is to introduce a series of weakly coupled oscillators (Deadzone oscillator-based VOC and Van der Pol oscillator-based VOC) that can be used for the regulation of single-phase power inverters in an islanded microgrid (MG). Its dynamic equations are used to provide the frequency and amplitude references of the inverters. In these traditional methods, there is always the presence of a 3−order harmonic in the output voltage, which causes a significant amount of 3−order harmonic current in the system. The non-linear dynamical equations of the oscillator are analyzed and its non-linear current source (NCS) is made simpler in order to develop new VOC for SPIs that can effectively get rid of the 3−order harmonic component in the oscillator’s output voltage. Finally, an extensive comparison of Deadzone-based VOC (Dz-VOC), Van der pol-based VOC (VdP-VOC), and new VOC-based controllers with linear and nonlinear loads is presented. The new VOC-based controller minimizes the 3-order harmonic component in the output voltage and achieves a quicker response compared to the conventional VdP-VOC-based controller. Simulation results of the Dz-VOC, VdP-VOC, and proposed new VOC-based control methods with different loads (Resistive, Linear RLC, non-linear) were compared and analyzed in detail. The total harmonic distortion (THD) of the current in Dz-VOC, VdP-VOC, and new VOC are 1.98%, 1.11%, and 0.21%, respectively. The 3rd harmonic is dominant in both Dz and VdP VOCs, while in the new VOC the 3rd harmonic is very less and below 0.1%. The new VOC is also showing good current sharing and fast voltage synchronization (within 0.2 s). Hardware experimentation is also carried out to analyze the efficacy of the proposed new VOC controlled SPI in standalone MG. The results clearly depict that the new VOC control strategy is quite efficient in handling the output voltage harmonics and situations of different loadings in the standalone MG.

Analysis and comparison of single-phase induction motor operation from single- and two-phase power sources using MATLAB simulation results

&lt;span lang="EN-US"&gt;Single phase induction motor (SPIM) has zero torque, this motor has many types and the main objective is to find the starting torque of the motor. This is done by providing auxiliary coils that are mechanically separated or weakened after 75% of the engine speed. The real problem here is that these auxiliary windings occupy a third of the iron core of the motor, and when they are separated or weakened, the capacity of the iron core is not fully used and the main windings must withstand the rated load current alone which shortens the life of the motor and reduces the hours of continuous operation of the motor. In this paper, a single-phase motor is fed from a single-phase power source and again from a two-phase power source, so that the auxiliary coils are not separated after 75% of the motor's speed and have a continuous role in the motor's operation. The torque and current flow in the motor are compared in both cases. Due to the rarity of the two-phase power supply in nominal uses, it can be supplied by a full bridge inverter. This comparison was provided by steady-state analysis and the results of MATLAB Simulink. &lt;/span&gt;

РОЗВИТОК ПРИНЦИПІВ ПОБУДОВИ ТА ВДОСКОНАЛЕННЯ МАГНІТНО- НАПІВПРОВІДНИКОВИХ ІМПУЛЬСНИХ ПРИСТРОЇВ СИЛОВОЇ ПЕРЕТВОРЮВАЛЬНОЇ ТЕХНІКИ

The principles of construction and improvement of magnetic-semiconductor devices of power converter technology using a complex synthesis of their elements, keys, nodes, and structures are considered in specific examples. The advan-tages are presented: synthesized semiconductor, magnetic and magnetic-semiconductor switches; combined single-phase power supply rectifiers; autotransformer multilevel voltage inverters; voltage converters with input current buffer node; pulse compression units with voltage doubling and generating special output pulses; the structure of a magnetic-semiconductor pulse generator assembled from the indicated components. It is shown that these advantages in comparison with known analogs include improved efficiency, quality of input electricity, efficient use of pulsed power supply by loads, simplification, and expansion of the functionality of the synthesized objects. As a result, materials were obtained. It was determined that it would be expedient to use and develop the presented complex synthesis concerning other objects of research of magnetic-semiconductor pulse devices of power converter technology. Ref. 9, fig. 8.

ANALISA JARINGAN DISTRIBUSI TEGANGAN MENENGAH DENGAN SISTEM SINGLE WIRE EARTH RETURN UNTUK WILAYAH TERTINGGAL, TERDEPAN DAN TERLUAR

Indonesia's rural electrification rate (RER) is still low. This is due to the high cost of installing a conventional three-phase or single-phase power supply in distributed rural loads. However, the Rural Energy Agency and the National Utility have made many efforts to address this issue. To this end, this document proposes a Single Wire Earth Return (SWER) electrification scheme for the electrification of a selected village, namely Serang, Banten. Field data were collected and used to design a potential SWER distribution network. A mathematical model representing SWER for Serang, Banten was developed and simulations were performed to determine soil potential and soil resistance. These two are important every time you install a HEAVY line. In addition, a technical and economic comparison was made in order to determine the short-term costs of the proposed SWER with the existing single-phase two-wire (SPTW) system. The technical and economic analysis shows that the proposed SWER system will achieve a cost saving of 50% compared to the installation of the SPTW system for Serang Banten electrification.

Accurate Circuit Parameter Determination of a Resonant Power Frequency Converter for High-Voltage and Partial Discharge Tests

For high-voltage (HV) and partial discharge (PD) tests on high-voltage equipment, a resonant power frequency converter has recently been developed. A single-phase power frequency converter with a resonant tuning and filter circuit and an HV testing transformer comprise the developed system. A difficulty in the tuning and filter circuit design is the unknown testing system circuit parameters, including unknown parasitic inductance, capacitance, and internal resistance. In this paper, a system with a voltage rating of 75 kVrms, apparent power of 40 kVA, and an operating frequency from 50 Hz to 200 Hz is considered for determination of the equivalent circuit parameters. From the determined circuit parameters, the appropriate resonant tuning and filter circuit was designed effectively. The transfer functions of the input and output testing voltages, along with the transfer impedance of the input voltage and signal voltage of the PD measuring port, were analyzed. The system design was verified by experiments with a voltage transformer. The gain of the transfer impedance was about 15 and 4 at the testing frequencies of 50 Hz and 200 Hz, respectively. With the proper design, it is possible to generate an output voltage waveform that is almost entirely sinusoidal and has a background noise level of under 1 pC. According to the experimental results, the system design of the resonant converter and the method for determining the equivalent circuit are very helpful for the HV and PD tests of voltage transformers in actual practice.