Values Of Phase Voltages Research Articles

Adaptation of a Cogenerator with Induction Generator to an On/Off-Grid Operation Using a Power Electronic System

Cogeneration sources play a very important role in the power industry with dispersed renewable sources with forced generation (e.g., photovoltaics and wind generators). They also fit into the circular economy by increasing the efficiency of fuel use, including biogas from agricultural or livestock waste. The aim of our research was to develop an effective source of electricity powered by agricultural biogas. The most important features of such a source are: operation in on-grid and off-grid mode, as well as a low cost of the device and uncomplicated operation. In addition, in Europe, the source of electricity connected to the power grid must meet the technical requirements of the “Network Codes Requirements for Generators” (NC RfG) network code. The appropriate certificate is easier to obtain using a power converter system for the source. For this purpose, an induction generator with a converter system and a small battery was planned. A converter system was developed and built, and then tests were carried out in various operating modes. During the measurements, it was confirmed that the requirements for the quality of electricity for off-grid and on-grid operation modes were met. The assumed maximum time of voltage recovery after changing the operating mode, amounting to 40 ms, was not exceeded. Furthermore, the limit values of phase voltages with unsymmetrical load, amounting to ±10% of the rated voltage, were not exceeded. In the battery usage off-grid mode, the time after a step change in the load power was not longer than 2 s.

Drive System Inverter Modeling Using Symbolic Regression

For accurate and efficient control performance of electrical drives, precise values of phase voltages are required. In order to achieve control of the electric drive, the development of mathematical models of the system and its parts is often approached. Data-driven modeling using artificial intelligence can often be unprofitable due to the large amount of computing resources required. To overcome this problem, the idea is to investigate if a genetic programming–symbolic regressor (GPSR) algorithm could be used to obtain simple symbolic expressions which could estimate the mean phase voltages (black-box inverter model) and duty cycles (black-box compensation scheme) with high accuracy using a publicly available dataset. To obtain the best symbolic expressions using GPSR, a random hyperparameter search method and 5-fold cross-validation were developed. The best symbolic expressions were chosen based on their estimation performance, which was measured using the coefficient of determination (R2), mean absolute error (MAE), and root mean squared error (RMSE). The best symbolic expressions for the estimation of mean phase voltages achieved R2, MAE, and RMSE values of 0.999, 2.5, and 2.8, respectively. The best symbolic expressions for the estimation of duty cycles achieved R2, MAE, and RMSE values of 0.9999, 0.0027, and 0.003, respectively. The originality of this work lies in the application of the GPSR algorithm, which, based on a mathematical equation it generates, can estimate the value of mean phase voltages and duty cycles in a three-phase inverter. Using the obtained model, it is possible to estimate the given aforementioned values. Such high-performing estimation represents an opportunity to replace expensive online equipment with a cheaper, more precise, and faster approach, such as a GPSR-based model. The presented procedure shows that the symbolic expression for the accurate estimation of mean phase voltages and duty cycles can be obtained using the GPSR algorithm.

ГРАФОАНАЛИТИЧЕСКОЕ ИССЛЕДОВАНИЕ РЕЖИМОВ ОДНОФАЗНОГО ЗАМЫКАНИЯ НА ЗЕМЛЮ

Relevance To determine the damaged phase in single-phase earth faults (SPEF), as well as for the purposes of relay protection and signaling of earth faults, it is important to know the phase voltages and the zero sequence voltage. Phase voltages are used to determine the damaged phase and determine the location of the damage. The zero sequence voltage is used to perform nonselective signaling of the SPEF and to determine the completeness coefficient of the fault in adaptive earth fault protections in networks with low earth fault currents. Single-phase short circuits in 6–35 kV networks occur as a rule through a fault resistance, the value of which can reach 5–7 kOhm or more. The fault resistance at the point of damage changes the values of both the zero sequence current and all phase voltages, and the zero sequence voltage. Therefore, the study of single-phase earth fault modes and the assessment of the effect of fault resistance on phase voltages and voltage. Aim of research The main aim of the research is to develop graphoanalytic methods for studying modes for SPEF through fault resistance in networks with an isolated neutral. Research methods Graphoanalytic methods are used to study the effect of fault resistance on phase voltages. The construction of phase voltage graphs directly in the fault resistance function may performe only for a specific electrical network. In the article, to perform the analysis in a generalized form, the equations of phase voltages are used as a function of intermediate variables, which depend on the value of the fault resistance, but do not depend on the parameters of the electrical network. As intermediate variables, the damage completeness coefficient, the relative fault resistance, as well as the angle by which the vector of zero sequence voltage, taken with the reverse sign, lags behind the vector of the pre-emergency voltage of the damaged phase. The main advantage of the phase voltage equations in the function of intermediate variables is that such equations have the same form for any electrical network. At the same time, voltage graphs and superimposed graphs of other parameters of the SPEF mode in relative units can be used as nomograms and allow us to study SPEF modes in a wide range of changes in fault resistances. Results Equations are obtained for the relative values of phase voltages and zero sequence voltages as a function of the damage completeness coefficient and the relative values of the fault resistance. Graphs of phase voltages and zero sequence voltages are constructed. Graphs of changes in the damage completeness coefficient and relative fault resistance are combined with voltage graphs. The obtained equations and constructed graphs are universal in nature, valid for any electrical network with an isolated neutral and can be used as nomograms for determining and analyzing all parameters of the SPEF mode in relative units. Formulas and examples of transition to named units are given.

A new level Increased NLM method of modular multi-level converters for reducing THD of output voltage

ABSTRACT This paper proposes a new modified level, increased nearest level modulation (NLM) method to improve the THD quality and enhance the quality of output voltage of modular multilevel converters (MMCs). Offshore wind farm links need connections from onshore national grids, and this paper is consistent with higher level voltage generation techniques by using MMC. By changing the on-number sub-modules (SM) at the middle position after using the round function, the generated gate logic by using the proposed method maintains a fixed magnitude value of phase voltage with a maximal number of (2 N + 1) levels, where N is the number of sub-modules per arm. The proposed method maintains the advantages of the conventional NLM such as simple implementation and low switching loss and avoids the disadvantages of the existing NLM method such as capacitor voltage ripple, peak value of arm inductor voltage, complexity in topology, etc. Both the advantages and disadvantages of the proposed and the conventional schemes are also studied, and an illustrated comparison shows the THD result differences for four methods. The system is simulated using MATLAB-Simulink to validate the feasibility of the proposed scheme and carried out by a hardware-in-the-loop simulation (HILS) system. By reviewing the simulation and experimental results, it was found that the proposed scheme improves the output voltage and THD quality.

Sensorless electric drive of the mixture supply system in the mold of the continuous steel casting installation

The system of automatic feeding of the slag-forming mixture into the mold of the continuous casting machine was investigated in this article. The necessity of using a slag-forming mixture in the process of steel production has been substantiated. The proofs are given that the consumption of the slag-forming mixture significantly affects the cost of the final product. The quality level of the final product depends on the uniformity and consistency of the mixture supply to the crystallizer. Therefore, the actual direction is the automation of the process of feeding the slag-forming mixture into the mold of the continuous casting machine. The description of the developed automatic installation, which implements the supply of slag-forming mixture, is presented. The necessity of using a sensorless electric drive for moving the trolley has been substantiated. A simulation model of a bogie electric drive with a vector control system based on sensorless determination of the angular speed of the engine has been developed. The description of the method for determining the angular speed of the motor based on the known values of phase voltages is given. The simulation of the developed electric drive system in the Matlab Simulink program, confirming the adequacy of the developed system. The introduction of a sensorless electric drive into the system for feeding the mixture into the mold of the continuous casting machine will increase the reliability of the entire system and reduce its weight and dimensions.

Phase voltage distortion of IPM and SPM machines with distributed windings in field weakening region

This study investigates the field-weakening capability of interior permanent magnet (IPM) and surface-mounted permanent magnet (SPM) machines with distributed windings by considering phase voltage distortion in field-weakening region. For analysis and comparison, the Nissan Leaf vehicle traction machine is studied as a reference benchmark machine and then a comparable SPM machine is designed within the main constraints of the benchmark machine. A finite element analysis model of the benchmark machine is developed and validated by published experimental measurement. Sinusoidal phase current is desired to enhance machine torque performance and power electronic converters employing vector control method are commonly used for traction machine supply. However, the machine terminal phase voltage distortion may introduce additional difficulties for machine control. Therefore, firstly, phase voltage distortions of IPM and SPM machines with distributed windings are compared and the mechanisms are discussed. Due to the voltage distortion, the peak value of phase voltage may be higher than the fundamental one. Therefore, the influences of IPM and SPM topologies on machine traction characteristics are investigated. The study indicates that SPM machines with distributed windings can be designed to achieve comparable torque and power performance and better field-weakening capability compared to IPM machines.

Development of hardware and software for calculation and monitoring of the unbalance factor in three­phase voltage system

Hardware and software for measuring and monitoring the unbalance factor of the three-phase voltage system is developed. The shortcomings of the existing technical and software solutions for calculating the unbalance factor, as well as problems of applying the methods used for analog control systems to digital systems are described. The block diagram of the microprocessor system for measuring the voltage unbalance factor in the ship three-phase network with the effective values of phase voltages is used. The analysis of the analytical expressions to calculate the unbalance factor allowed minimizing the utilization of system hardware necessary for the formation of all necessary signals. The optimized structure of the digital filter to calculate the effective value of the deterministic periodic signal at the optimum speed of a discrete system is proposed. An increase in the sampling rate in the optimized filter structure does not lead to an increase in the number of arithmetic operations of addition and multiplication, which is an advantage of the proposed system in comparison with similar ones. This allows monitoring of instantaneous changes in the unbalance factor of three-phase voltage and enables the system to operate in real time. The developed hardware and software can be integrated into the automated control system of the power plant and used in voltage control systems, as well as for the timely detection of voltage unbalance to protect equipment and prevent violation of normal operation.

Determination of power parameters of switched reluctance motor based on instantaneous values of phase voltages and currents

Determination of power parameters of switched reluctance motor based on instantaneous values of phase voltages and currents

Dual-Inverter-Fed Pole-Phase Modulated Nine-Phase Induction Motor Drive With Improved Performance

Typical value of rated phase voltage of pole phase modulated multiphase induction motor (PPMMIM) drives with wider speed range is in the order of few hundreds of kilovolts. This high value of phase voltage for high power density applications results in higher dc-link voltage requirement and switch voltage rating of two-level multiphase inverter. Further, using multiphase space vector pulse width modulation (SVPWM) yields less dc-link utilization. Methods to increase dc-link utilization using SVPWM with offset value of third harmonic order introduces dominant lower order harmonic currents into phase windings. One more major problem in high pole mode of PPMMIMs is higher torque pulsation due to decrease in phase number. To address these problems this paper proposes a dual-inverter-based multilevel voltage excitation scheme for nine-phase PPMMIM with 1:3 speed ratio. In four-pole mode a simple phase grouping technique to eliminate lower order harmonic currents in the phase windings is proposed. In addition each inverter feeding these phase groups is modulated using carrier-based three-phase SVPWM to achieve higher dc-link utilization. This paper also proposes a multilevel voltage generation scheme for 12-pole mode of operation using carrier phase shifted pulse width modulation (PWM) for inherently available equal voltage profile coils with the same dual inverter structure. The torque ripple using phase shifted carriers PWM and single carrier PWM are compared. Finite element method model of nine-phase PPMMIM is developed in Ansys Maxwell two-dimension and is cosimulated with three three-phase dual inverters in Simplorer environment. Experimental validation is done for linear and over modulation case on 9ФIM fed from three three-phase dual inverters controlled using Spartan six field programmable gate array board programmed in VHDL.

Estimation of On-Fly Phase Resistance of on 8/6 Switched Reluctance Motor for Sensorless Control

Given that most sensorless methods use the “flux linkage” algorithm for their control, this paper deals with possibilities to improve this sensorless method. When using the sensorless “flux linkage” method it is necessary to know not only the values of phase voltages and currents, but also the correct value of the phase resistance. During the operation of the switched reluctance motor, the value of the phase resistance is significantly changing due to the temperature dependence. Such resistance error causes an inaccurate estimation of the flux linkage. For this reason, it was desirable to implement a sensorless control algorithm for estimating phase resistance. In this paper, the experimental results of the implemented algorithm for estimating the phase resistance under the sensorless operation of a switched reluctance motor are presented. The practical implementation of control of the switched reluctance motor is carried out using a control system with a 16-bit digital signal processor. DOI: http://dx.doi.org/10.5755/j01.eee.20.5.7093

Design of Hybrid PWM Algorithm for the Reduction of Common Mode Voltage in Direct Torque Controlled Induction Motor Drives

This paper presents a novel hybrid pulse width modulation (HPWM) technique for the reduction of common mode voltage (CMV) in direct torque controlled induction motor drives based on the concept of imaginary switching times. In the proposed approach, different active zero state PWM (AZPWM) sequences are considered in which the actual switching times are calculated based on the instantaneous values of phase voltages. Moreover AZPWM sequences utilize active voltage vectors for composing the reference voltage vector instead of using zero voltage vectors. But these sequences suffer from steady state ripples. To reduce the ripples in steady state, a HPWM technique is developed in which stator flux ripple analysis is done for all the AZPWM sequences in terms of actual switching times, dc link voltage (Vdc), sampling time period (Ts). To validate the proposed PWM algorithm, numerical simulation studies have been carried out using MATLAB-Simulink and results are presented and compared.

A sensorless detecting strategy of rotor position and speed on permanent magnet synchronous motor.

A inverter-fed permanent magnet synchronous motor with a rotor position sensor and a speed sensor is used in many industrial applications as a DC-brushless motor. In this paper, a strategy which determines the rotor position and the speed of the permanent magnet synchronous motor by using the instantaneous values of phase voltage and phase current sensing is explained.In a permanent magnet synchronous motor, the permeance of the stater magnetic circuit is altered by rotating the rotor position; the inductance of a phase winding changes according to rotor positions. Hence, the phase voltages and currents of the motor have close relations with the rotor positions. Measured values of phase voltages and currents and the values of the equivalent circuit parameters are substituted to the voltage equation of the synchronous motor. Then, we can calculate the value of the rotor position angle by that voltage equation. The rotating speed of the rotor can be calculated from the voltage equation by substituting the rotor position angle. In these calculations, we used a 16-bit micro-computer and a DSP, and for sensing phase voltages and currents, 12-bit high quality A/D converters are used.Experimental results obtained by using the prototype system were congruous values of the rotor position angles and the rotating speed.