Nonsinusoidal Supply Research Articles

Harmonic Injection Strategy Considering Multiplane Iron Loss Impact With Optimal Magnetizing Flux Distribution for Multiphase Induction Machines

Lagging orientation error detuning induced by iron losses for multi-planes of multiphase IM under non-sinusoidal supply control triggers error in determination of calculated harmonic, fundamental air-gap flux advance angles and harmonic slip frequency. This in-turn leads to inaccurate harmonic injected currents, which are dependent on harmonic multiple of frequency for the corresponding plane with respect to fundamental plane frequency. This paper proposes the novel harmonic injection strategy considering the detuned impact of iron losses by keeping in view the complete iron loss modeling for both harmonic magnetizing flux orientation control (MFOC) and fundamental rotor flux orientation control (RFOC) planes. Furthermore, satisfaction of complete optimal flux distribution constraints for multiphase IM are taken into account which results in preserving optimal flux patterns throughout the mechanical loading particularly at low and medium load conditions. Contrary to other traditional orientation schemes, this paper adopts the MFOC and RFOC for harmonic and fundamental plane respectively for acquiring the aligned and synchronized control of harmonic and fundamental air-gap flux distribution. Detailed experimental results incorporating seven phase induction machine as prototype are utilized to evaluate the harmonic injected currents, advance angles, slip frequencies and induced EMF waveforms which validate the effectiveness of proposed scheme.

Уточненное моделирование и экспериментальное исследование энергоэффективной системы испытаний асинхронных машин

When testing asynchronous machines, it is important to use energy-efficient methods, for example, the method of mutual loading of two machines with articulated shafts. One machine operates in the mode of the motor – frequency converter, the second machine operates in the mode of the generator – industrial frequency network. Both machines are simultaneously tested under load and energy costs for testing are reduced due to its recuperation. The method requires a correct loading algorithm. The modeling of the method based on chain models does not consider the implementation feature. Thus, it is advisable to refine the simulation of the asynchronous machine testing system by the mutual load method. The method is based on strict models considering the coupling of machine torque on a common shaft, the operation of machines in the mode of frequency converter, non-sinusoidal supply voltage, saturation of steel, displacement of current in conductors, for example, based on the associated analysis of electromagnetic fields in both machines. The authors have applied the packages of electromechanical units with electrical and mechanical Ansys Simplorer ports and finite element analysis of electromagnetic fields Ansys Maxwell for refined simulation of the asynchronous machine testing system by the method of mutual loading. Experimental studies of the system have been carried out on laboratory equipment using certified devices. A refined simulation of an energy-efficient testing system of asynchronous machines by the method of mutual loading has been carried out. It is based on calculations of the electromagnetic field and allows us to read the transient and steady-state modes of operation of a two-machine unit with a common shaft. An automated stand has been created that allows testing asynchronous machines by the method of mutual loading. The developed refined simulation of electromechanical processes in asynchronous machines during tests by the method of mutual loading with associated calculations of electromagnetic fields in both machines provides calculated results with an error of no more than 5–7 % in comparison with 40 % error of calculations in the transient modes of operation using chain models.

The influence of non-sinusoidal voltage sources on the steady state performance of different NEMA Designs of IMs

Voltage distortion has become one of the most common power quality problems in industrial applications, which has gained a great deal of attention in recent years because of the widespread usage of non-linear loads. Three-phase induction motors are widely used and one of the factors that confirm the reduction of their performance is the presence of harmonics in their voltage supply. In this paper, the impact of non-sinusoidal supply voltages on the steady-state performance of different NEMA designs of squirrel cage induction motors (SCIMs) is presented. It presents the analytical modeling based on the equivalent circuit taking into consideration the skin effect impedance that incorporates the skin effect on the rotor bars, which is used to investigate the motor performance under such conditions. The importance of this study is that it compares all NEMA designs in terms of electromagnetic torque, efficiency, losses, power factor, stator and rotor currents, and derating factor under a distorted supply voltage that is polluted by the most significant odd harmonic orders at adjustable levels in the range of (0–25) % of THDv%. The obtained results are compared and validated with the system employed by using MATLAB/Simulink software.

Fair Power Factor Billing Under Unbalanced and Nonsinusoidal Voltage Supply

Utilities apply an additional fee for medium and large customers with low power factors. However, unfair financial charges may occur in installations subjected to voltage unbalance and harmonic distortion. The objective of this paper is to determine the fairest PF definitions and their corresponding measurement algorithms in the case in which a constant impedance load or an induction motor is supplied with unbalanced and nonsinusoidal voltages. Fairness is defined considering that the meter (built based on a particular definition and measurement method) under nonideal supply should lead to very close values as if it was submitted to an ideal balanced sinusoidal supply. We performed computational simulations to emulate several conditions in which a balanced customer (modeled as a constant impedance load or an induction motor) is charged due to a voltage supply no longer balanced and sinusoidal. We also performed experimental tests with an induction motor subjected to a wide range of unbalanced nonsinusoidal supply conditions to ratify the conclusions drawn from the simulations. Based on the simulation results and the experimental tests, we indicate some power factor definitions and measurement methods that are not significantly affected by voltage unbalance and harmonic distortions. These indicated PF definitions provide the fairest billing for conditions with unbalanced nonsinusoidal voltages.

Power quality improvement using model predictive control based shunt connected custom power device in a single phase system

Abstract The performance evaluation of a single-phase shunt-connected custom power device (SC-CPD) for current quality improvement is discussed in this paper. The SC-CPD performance is compared based on the linear triangle-comparison pulse width modulation (TC-PWM) control, hysteresis current control (HCC), and the predictive non-linear switching control strategies. The predictive switching control is implemented using the finite control set-model predictive control (FCS-MPC). The switching control techniques’ operational and implementation features are discussed for the given control objectives of the SC-CPD for a particular nonlinear load. Basic functional case studies with sinusoidal and non-sinusoidal supply mains in the presence of non-linear loads are presented to illustrate the appropriateness of the switching techniques. The SC-CPD model and control methodologies are developed in the MATLAB/Simulink environment, including designing of various circuit components. Finally, performance simulation results using the switching techniques have been compared and validated using OPAL-RT 4510-based real-time simulations.

An Improved Core Loss Model of Ferromagnetic Materials Considering High-Frequency and Nonsinusoidal Supply

With the emerging power electronic technologies, numerous electrical devices use high-frequency and nonsinusoidal supplies. Such sources generate complex harmonic fields that overburden the accurate prediction of core losses using the conventional finite element method (FEM). Thereby, to predict core losses under those high-frequency and nonsinusoidal supplies accurately, this study first built a test system for core losses measurement of ferromagnetic materials (e.g., soft ferrite, laminated steels, and nanocrystalline alloy) fed by the square and pulsewidth modulated (PWM) supplies. Then, the loss prediction problems of the classical core loss model under high-frequency and nonsinusoidal supplies are revealed. Afterward, an improved FEM-based core loss model is proposed, which includes a piecewise variable parameters based hysteresis loss model, an eddy current loss model considering different cross sections of magnetic circuit and supply waveforms, and improved excess loss coefficients. Experimental validations on different materials, the nanocrystalline alloy in an 11-kVA intermediate frequency transformer, the ultrathin silicon sheets in a 10-kW high-speed permanent magnet motor, and the nanocrystalline alloy in a 3-kW wireless power transfer system, are conducted systematically. The effectiveness and generality of the improved core loss model were verified.

Study the performance of three-phase induction motor under imbalanced non-sinusoidal supply

The rising of single-phase distributed generators and imbalanced loads in the electrical power grid can cause the three phases voltage to unbalance, causing in risen losses and overheating in motors. As a consequence of the growing usage of electronic equipment and non-linear load, the waveform of the voltage source of the electrical system is becoming distorted and variations appear among the phases. This work explores the negative impacts of imbalanced of 10 HP three phase induction motor squirrel-cage fed by three phase IGBT inverter at full load. The drive system has been designed and simulated by MATLAB/Simulink. The inverter switches are controlled by a pulse controller, which consists of two level pulse width modulation (PWM). The results represent the effects on the performance of the motor. The results of the Simulation show the negative impacts of imbalanced non-sinusoidal voltages which are higher than the case of balanced non-sinusoidal voltages. Also, the computation of voltage unbalance factor (VUF) depending on positive and negative sequence components are considered.

A three-phase induction motor performance under different loading types supplied from balanced and unbalanced Thyristorized supply voltage. (Dept. E.)

Induction motors are used extensively in a wide variety of industrial applications. The development in the power electronics field have led to an ever- increasing use of thyristors switching devices in the induction motors supply voltage control for the purpose of speed control, soft starting, and energy saving in these applications. Such power electronics switching devices generate different waveforms patterns of nonsinusoidal voltage according to balanced and unbalanced condition of their operation. So, the present paper investigates the impact of this nonsinusoidal supply voltage waveforms on the dynamic performance of a three-phase induction motor during balanced and unbalanced operation. Also, this paper considers the IM operation at different loading conditions. A MATLAB program has been used to model the thyristorized induction motor performance.

A new approach to single-phase systems under sinusoidal and non-sinusoidal supply using geometric algebra

The aim of this work is to present major upgrades to existing power theories based on geometric algebra for single-phase circuits in the frequency domain. It also embodies an interesting new approach with respect to traditionally accepted power theories, revisiting power concepts in both sinusoidal and non-sinusoidal systems with linear and nonlinear loads for a proper identification of its components to achieve passive compensation of true non-active current. Moreover, it outlines traditional power theories based on the apparent power S and confirms that these should definitively be reconsidered. It is evidenced that traditional proposals based on the concepts of Budeanu, Fryze and others fail to identify the interactions between voltage and current harmonics. Based on the initial work of Castro-Núñez and others, new aspects not previously included are detailed, modified and reformulated. As a result, it is now possible to analyze non sinusoidal electrical circuits, establishing power balances that comply with the principle of energy conservation, and achieving optimal compensation scenarios with both passive and active elements in linear and non-linear loads.

Rotor fault diagnosis of frequency inverter fed or line-connected induction motors using mutual information

Characteristics like robustness, adaptability to several load conditions, and low costs of operation and maintenance are some of the reasons three-phase induction motors are ubiquitous in industrial applications. Even so, these machines are subjected to electrical and mechanical faults which can result in malfunction. The detection of incipient faults is the focus of several recent studies because they provide information for timely decisions to avoid unplanned stops of industrial processes. A common problem of induction motors is the presence of broken rotor bars. Most of the methods of condition monitoring and fault diagnosis focus on the usage of only one type of power supply: line-connected or fed by frequency inverters. Given this situation, we present an alternative technique for the detection of broken rotor bars of three-phase induction motors regardless of the type of power supply. Our approach is based on similarity measures of the stator current signals of two motor phases in order to extract the relevant features of such signals, which are then classified using three intelligent systems: artificial neural network, support vector machines, and k-nearest neighbors. We performed 3310 experimental tests with motors operating in steady state, with sinusoidal and non-sinusoidal power supply, and variations of voltage unbalance levels, supply frequency, and load torque. Classification accuracy rates over 92% of success were obtained in these tests, which validate the proposed approach.

Operation of the induction motor in non-sinusoidal voltage supply conditions

The paper presents the theoretical basis of the mathematical expression derived from the American standard, used to determine the thermally permissible torque load capacity of the cage induction motors when supplied with distorted voltages. The results of the measurement verification of this expression for different voltage shapes supplying the tested motor are presented. The test results confirmed the correctness of the expression when the motor is supplied with distorted voltage with a limited number of higher harmonics.

Investigation of The impact of Unbalanced and Non-sinusoidal Supply Voltages on Converters.

In this paper two input current modulation strategies for matrix converters are experimentally analyzed under two different supply conditions: sinusoidal unbalanced voltages and non-sinusoidal balanced voltages. Both strategies use the Space Vector Modulation (SVM) technique in order to control the matrix converter accordingly to the input and output constraints. Strategy A modulates the input currents keeping the corresponding space vector in phase with the input voltage vector. Strategy B operates in order to keep the input current vector in phase with the positive sequence fundamental component of the input voltage vector. A comparison between the two strategies is made in terms of the reduction of the input current disturbances due to the unbalanced and non sinusoidal voltage on the grid. It is found that a dynamic current modulation strategy, independent of the voltage disturbances such as Strategy B, is more effective for the reduction of the RMS value of input current disturbances. The validity of the theoretical investigation i.e. the effectiveness of the current modulation strategy conforms to experimental tests result carried out on a matrix converter prototype.

Shunt Active Filter Based on 7-Level Cascaded Multilevel Inverter for Harmonic and Reactive Power Compensation

This paper proposes a simple fundamental active current extraction scheme for a 1-phase 7-level cascaded multilevel inverter. The proposed algorithm extracts the fundamental active component of the load current, irrespective of the change in supply frequency. Moreover, a band pass filter (BPF) based phase locked loop (PLL) is proposed for the generation of the unit vector template (UVT). This ensures the effective operation of the SAF, even under a non-sinusoidal supply voltage. The proposed algorithm provides an instantaneous value of the fundamental active component of the load current, which when drawn from the supply ensures that the source current is sinusoidal and that the unity power factor (UPF) is maintained at the supply end. The usage of two cascaded H-bridges powered by two dc sources of different magnitude are put into use for the realization of a 1-phase 7-level cascaded inverter. The functioning of the 1-phase SAF with a fundamental current extractor scheme is examined for steady-state and dynamic operation under non-distorted and distorted supply voltages.

Improving the accuracy and time of calculating steady-state modes of increased frequency electrical systems

The authors of modern Russian and foreign works suggest using the method of frequency analysis with Fourier transforms for modeling alternating current systems with a non-sinusoidal supply voltage. By applying the above-mentioned method to calculating steady-state modes of increased frequency power electrical systems (IFPES), we have found that there are significant differences between the calculated and experimental results, and the model calculation time is long. These problems can be solved by obtaining generalized formula expressions for the internal resistance value of IGBT transistors and the amplitudes of the acting EMF (voltage) in the IFPES applying Fourier decomposition. The generalized expressions for determining the internal resistance of IGBT transistors were obtained by analyzing physical processes of charge diffusion. The amplitude of the acting EMF (voltage) was determined by numerical integration. Simplified analytical expressions suitable for determining the frequency dependence of the resistance of IGBT transistors in the open state in electrical devices have been obtained. The IFPES calculation rate model has been optimized by frequency analysis. The obtained generalized analytical expressions allow making more accurate calculations of the transistor internal resistance value (with a difference of 70 % compared to the previously used value). By optimizing the calculation method we were able to reduce the model calculation from 8 hours to 3 minutes with Nk = 3000 harmonics. The modernized method can be used not only for calculating the IFPES but also for analyzing any electrical circuits with power electronics components exposed to non-periodic and non-sinusoidal currents and voltages.

Influence of Non-Sinusoidality of Voltage on Electricity Loss in Distribution Networks

The problem of electromagnetic compatibility in high-voltage distribution networks is considered, connected with the consumption of reactive power at the fundamental frequency and distortion of the current form in the feeding networks. The estimated indices of the calculation of power losses for non-sinusoidal supply voltage in the high-voltage distribution network for the PNS pump with a capacity of 50 MW are given. Methods for reducing the voltage non-sinusoidality.

The influence of nonsinusoidal supply voltage on the amount of power consumption and electricity meter readings

During electricity generation, transformation, distribution and consumption, distortions of voltage and current sinusoidal signals occur. Most consumers are non-linear, and a significant content of higher harmonics emerges when they are connected to the supply grid. The algorithms of modern electricity meters take into account most of higher harmonics, whilst with some fallibilities. However, when supply voltage and current have the same amplitude and a various harmonic composition, the readings of electricity meters can vary greatly. This article describes how the harmonic composition of supply voltage and current affects the readings of electricity metering devices. The analysed ratios do not depend on the amplitude of supply voltage.

Half-bridge Cascaded Multilevel Inverter Based Series Active Power Filter

A new single phase half-bridge cascaded multilevel inverter based series active power filter (SAPF) is proposed. The main parts of the inverter are presented in detail. With the proposed inverter topology, any compensation voltage reference can be easily obtained. Therefore, the inverter acts as a harmonic source when the reference is a non-sinusoidal signal. A 31-level inverter based SAPF with the proposed topology, is manufactured and the voltage harmonics of the load connected to the point of common coupling (PCC) are compensated. There is no need for a parallel passive filter (PPF) since the main purpose of the paper is to represent the compensation capability of the SAPF without a PPF. It is aimed to compensate the voltage harmonics of the load fed by a non-sinusoidal supply using the proposed inverter. The validity of the proposed inverter based SAPF is verified by simulation as well as experimental study. The system efficiency is also measured in this study. Both simulation and experimental results show that the proposed multilevel inverter is suitable for SAPF applications.

Modelling, design and analysis of multi-phase induction motor

Three-phase induction motor is extensively employed for the high power drive application rated at several megawatts, such systems generally exhibit poor performances in terms of losses and torque pulsations. Additionally, power semiconductors devices of large voltage and current rating requires in high power applications, which are either expensive or unavailable. Due to the potential benefits of multi-phase technology, recently some interest has also grown in the area of multi-phase machine. In this paper, mathematical model, analysis, design and simulation of multi-phase machine are carried out. Performance investigations of six-phase induction motor is carried out under steady-state and transient conditions when fed from sinusoidal and non-sinusoidal supply mains. For high power variable speed drives applications, multi-phase motor is supplied through power converters and its simulation studies are also carried out. The simulation studies of conventional three-phase induction motor and multi-phase motor of same rating are carried out and its comparative study is made to find out its suitability for general purpose drives applications. Based on simulation study, the multi-phase machine offers numerous advantages over the conventional three-phase induction motor drives such as improvement of the torque quality, reduction of the stator current per phase, improvement of torque density and increase of the fault tolerance.

Modelling, design and analysis of multi-phase induction motor

Three-phase induction motor is extensively employed for the high power drive application rated at several megawatts, such systems generally exhibit poor performances in terms of losses and torque pulsations. Additionally, power semiconductors devices of large voltage and current rating requires in high power applications, which are either expensive or unavailable. Due to the potential benefits of multi-phase technology, recently some interest has also grown in the area of multi-phase machine. In this paper, mathematical model, analysis, design and simulation of multi-phase machine are carried out. Performance investigations of six-phase induction motor is carried out under steady-state and transient conditions when fed from sinusoidal and non-sinusoidal supply mains. For high power variable speed drives applications, multi-phase motor is supplied through power converters and its simulation studies are also carried out. The simulation studies of conventional three-phase induction motor and multi-phase motor of same rating are carried out and its comparative study is made to find out its suitability for general purpose drives applications. Based on simulation study, the multi-phase machine offers numerous advantages over the conventional three-phase induction motor drives such as improvement of the torque quality, reduction of the stator current per phase, improvement of torque density and increase of the fault tolerance.

Analysis of 37-kW Converter-Fed Induction Motor Losses

This paper presents an energy efficiency analysis of a 37-kW standard squirrel-cage induction motor under sinusoidal and nonsinusoidal supply. The motor losses are analyzed using the conventional IEC loss segregation method and also numerically modeled using finite-element simulations. The measured and simulated loss components are compared with three different modulation methods. The overall simulated losses are in good agreement with the measured ones, but there exist differences in the loss components.