High Harmonic Content Research Articles

Input Power Quality Improvement in Switched Reluctance Motor Drive using Minnesota Rectifier

This paper deals with an input power quality improvement in a midpoint converter based switched reluctance motor (SRM) drive at ac mains using Minnesota rectifier. Normally a midpoint converter is used as a power converter for SRM drive. Conventionally three phase ac mains fed bridge rectifier is used as a dc source to feed this power converter which produces high content of harmonics at ac mains with a very low power factor. The proposed Minnesota rectifier with a midpoint converter fed SRM drive improves the power factor at ac mains with low current harmonics. This method provides constant dc link voltage and balanced capacitor voltages of the midpoint converter. The Minnesota rectifier fed SRM drive is modelled and its performance is simulated in Matlab/Simulink environment. The performance of Minnesota rectifier is compared with a conventional bridge topology for SRM drive to demonstrate improved power quality at ac mains.

A pendulum with an elliptic-type parametric excitation: Stability charts for a damped and undamped system

In this paper, a pendulum parametrically excited by the excitation which has the form of the Jacobi cn elliptic function is considered. Three cases related to the value of the elliptic parameter are distinguished: the case when it is smaller than zero, when it ranges between zero and unity, and when it is higher than unity. First, interpretations of the excitation with such elliptic parameter are given in terms of its period, higher harmonic content and the amplitude. These interpretations enable one to consider the elliptic-type excitation as a type of multi-cosine excitation whose frequency and amplitude are related mutually in a particular way. Stability charts are determined for damped and undamped systems. When the elliptic parameter is equal to zero, the governing equations considered transform to the well-known Mathieu equation. In all other cases, the governing equations considered can be seen as a new generalisation of the Mathieu equation. The influence of an arbitrary real elliptic parameter on the location and shape of the transition curves and instability tongues is investigated, illustrated and discussed in all three cases, which represent new and so far unknown results.

Real Time Harmonic Analysis of Recuperative Current through Utilization of Digital Measuring Equipment

This paper deals with device for online, real time analysis of recuperative current with use of microprocessor. This system is used in railway transport for measurement and analysis of recuperative-currents from converter in railway engine. Recuperative currents from converters in railway engines, flows through rail back to the distribution point. Content of higher harmonics in these currents must not exceed limits specified in international standard UIC 550-3, so exact measurement and analysis of this harmonics is necessary. Proposed device uses microprocessor for real time measurement and analysis of recuperative currents. DOI: http://dx.doi.org/10.5755/j01.eee.19.5.4364

A Systematic Approach for Medium-Voltage Power Factor Correction Design

The value proposition for the installation of power factor (PF) correction (PFC) to avoid costly utility penalties is easily understood. The attractive payback of such PFC opportunities often pushes the project ahead without engineering considerations. In the case of medium-voltage PFC, lack of upfront engineering can lead to unexpected consequences in the performance of the PFC equipment ranging from nuisance trips and blown fuses to catastrophic failure in the extreme. In this paper, the authors propose a systematic approach to the design of PFC for medium-voltage systems. Three actual case studies were selected to illustrate this systematic approach and show that it can be applied regardless of the size, type, and complexity of the facility. Such a methodology is composed of load flow and harmonic measurements, harmonic analysis, utility billing demand and PF analysis, and reactive compensation specification in the form of either capacitors or harmonic filters, if needed. Diverse and competing design constraints, including daily and week load cycles, nearby utility capacitors, switched or stepped requirements, specifics of utility tariffs, loads with high harmonic content, and harmonic resonance, are identified, analyzed, and then incorporated into the solution to ensure successful performance of the PFC equipment.

Cross‐switched multilevel inverter: an innovative topology

Multilevel inverters have attractive features which make them one of the most popular fields of investigations. They can operate in high power and high voltage conditions. Multilevel inverters generate output voltage with high quality and low harmonic contents. As the number of output voltage levels increases, the quality of the output voltage is improved leading to reduction of the filtering requirements. However, multilevel inverters have the disadvantage of increased power electronic switches. This leads to higher cost, size and complication. Some advanced topologies have been introduced to reduce the number of power electronic switches, unfortunately, most of these topologies need high voltage switches on their structure making them unsuitable for high voltage conditions. In this study, an innovative topology for multilevel inverter is proposed which reduces the number of switches considerably without using high voltage switches. The proposed topology is a general topology which can be extended for any number of voltage levels. The authors call this topology as cross-switched multilevel inverter. The simulation results obtained in PSCAD/EMTDC as well as the experimental results verify the proposed topology.

Frequency and Total Harmonic Distortion Estimation Based on Adaptive Filters

In this paper, a low computacional cost total harmonic distortion and frecuency estimation method is proposed. This method is based on adaptive digital filters allowing tracking the fundamental frequency variations. Real time experimental results obtained using a fixed point digital signal processor development kit are presented. They show an acceptable performance and have a robust behavior to signal distortions such as frequency fluctuations, high harmonic content, subharmonic and interharmonics.

Design Analysis of LCTLC Resonant Inverter for Two-Stage 2-Phase Supply System

This paper deals with the design analysis and synthesis of power resonant inverter with sinusoidal output voltage for sensitive loads. The proposed filter must be capable of removing higher harmonic components from the supplying voltage to reach a harmonic distortion of roughly 5% in the whole range of the load (0–100%). The inverter can be supplied from either single-phase voltage inverter in full-or half-bridge connection, or from simple DC/DC buck converter. Non-symmetrical control causes higher harmonic content, both odd and even. Simulation and experimental results based on designed parameters and subsequently obtained from Matlab and OrCad models confirm good quality of output quantities, voltage and current.

Mechanisms of high frequency song generation in brachypterous crickets and the role of ghost frequencies

Sound production in crickets relies on stridulation, the well-understood rubbing together of a pair of specialised wings. As the file of one wing slides over the scraper of the other, a series of rhythmic impacts causes harmonic oscillations, usually resulting in the radiation of pure tones delivered at low frequencies (2-8 kHz). In the short-winged crickets of the Lebinthini tribe, acoustic communication relies on signals with remarkably high frequencies (>8 kHz) and rich harmonic content. Using several species of the subfamily Eneopterinae, we characterised the morphological and mechanical specialisations supporting the production of high frequencies, and demonstrated that higher harmonics are exploited as dominant frequencies. These specialisations affect the structure of the stridulatory file, the motor control of stridulation and the resonance of the sound radiator. We placed these specialisations in a phylogenetic framework and show that they serve to exploit high-frequency vibrational modes pre-existing in the phylogenetic ancestor. In Eneopterinae, the lower frequency components are harmonically related to the dominant peak, suggesting they are relicts of ancestral carrier frequencies. Yet, such ghost frequencies still occur in the wings' free resonances, highlighting the fundamental mechanical constraints of sound radiation. These results support the hypothesis that such high-frequency songs evolved stepwise, by a form of punctuated evolution that could be related to functional constraints, rather than by only the progressive increase of the ancestral fundamental frequency.

Design and Implementation of 30kW Three-Phase PV Grid-Connected Inverter

This paper developed a mathematical model of three-phase PV grid-connected inverter, and studied the grid-connected current control method based on PI control in synchronous rotating reference frame. Simulation and experimental results from the prototype of 30kW three-phase PV grid-connected inverter proved the correctness and the feasibility of the control strategy, and this grid-connected inverter can operate at the unity power factor state with a nice dynamic performance, and the output current has high sinusoidal and low harmonic content as well as good symmetry.

Study on Harmonics Suppression of High-Power Rectification Circuit Based on Saber Simulation

It analyzed the quantity of differ-harmonic in the output from vary pulse rectification circuit. Considering the problems of great voltage fluctuation and high harmonics content in the rectification output under the direct-supply of current source mode, put forward the method of 12-pulse rectification circuit with equilibrium rector circuit with equilibrium reactor into direct-supply of current source mode. From the simulation results it can be summarized that 12-pulse rectification circuit with equilibrium reactor can not only smooth the output but also suppressing the harmonics.

Static–dynamic modelling of the electrical behaviour of a commercial advanced alkaline water electrolyser

This paper analyses the permanent and transient behaviour of a 1Nm3h−1 commercial advanced alkaline water electrolyser and develops a complete and integrated static–dynamic electrical model that can be applied to any commercial water electrolyser. The model is based on the thermodynamic, activation, double-layer and ohmic effects and phenomena that take place in a real alkaline electrolysis process. The parameters of the model are experimentally determined from both static and dynamic operating tests to the electrolyser. Based on these tests, the electrical behaviour of the electrolyser has been characterized, concluding that, at operating conditions of 45°C and 25bar, the cell area-specific resistance is 0.431Ωcm2 and the cell specific double-layer capacitances are 0.0467Fcm−2 for the anodic interface and 2.25×10−3Fcm−2 for the cathodic interface. The model has been implemented on MATLAB-Simulink® and validated in three different operating environments: at static operation by means of the I–V characteristic curves; at dynamic operation by means of a sinusoidal current of various amplitudes and frequencies superimposed to a DC current; and by using two power supplies with different conversion topologies, the first one harmonic free and the other with a high harmonic content. As it will be shown in the paper, the model simulations reproduce with a high accuracy the experimental electrical behaviour of the electrolyser.

Extreme-ultraviolet compact spectrometer for the characterization of the harmonics content in the free-electron-laser radiation at FLASH

The design and the commissioning results of a portable and compact spectrometer for the high harmonics content characterization of the extreme-ultraviolet radiation of FLASH (free-electron laser in DESY, Hamburg, Germany) are presented. The instrument is a grazing-incidence flat-field spectrometer equipped with two variable-line-spaced gratings; it covers the 2-40 nm wavelength region with a spectral resolution in the 0.1-0.2% range. Both spectral and intensity fluctuations of the fundamental emission and the harmonics are monitored.

Slot Harmonic Impact on Rotor Losses in Fractional-Slot Permanent-Magnet Machines

Fractional-slot permanent-magnet (PM) machines have several advantages, but they suffer from the high content of space harmonics in the air-gap magnetomotive force (MMF) distribution. The MMF space harmonic amplitude and frequency depend on the particular combination of numbers of slots and poles. Such harmonics induce losses in the rotor since they are not synchronous with the rotor speed. This paper compares several kinds of machines with the same stator lamination but with different numbers of phases; three-, five-, and seven-phase PM machines are considered. Several winding configurations are compared, changing the number of poles but maintaining the same number of slots. Although in each case there is a reduction in terms of harmonic content, it is shown that rotor loss reduction is lower than expected. Some considerations about the harmonic impact are given. Although no experimental results are given, this paper refers to previous works in which rotor losses have been investigated and measured experimentally.

Heuristic Algorithm for Photoplethysmographic Heart Rate Tracking During Maximal Exercise Test

Photoplethysmography (PPG) is a non-invasive optical technique that can be used to quantify the arterial blood pulse rate. Signal corruption by motion artifacts limits the practical accuracy and applicability of instruments for monitoring pulse rate during intense physical exercise. This study develops and validates an algorithm, which is based on linear filtering and frequency-domain and heuristic analyses, for extracting the heart rate from a PPG signal in the presence of severe motion artifacts. The basis of the hearth beat frequency selection is the observed high harmonic content of movement artifact signals with respect to the PPG-derived heartbeat. The algorithm, implemented in an experimental PPG measurement device, is developed by analyzing a set of PPG data recorded from a group of athletes exercising on a treadmill. An extensive set of tests is carried out during maximal exercise tests on a treadmill to validate the proposed algorithm by comparison with a reference electrocardiography measurement system. The Bland-Altman method is used to compare and evaluate PPG signals. The accuracy of the heartbeat measurement is better than ± 6.5 beats per minute (bpm) ( ≤ 4.2 %) even under maximal exercise conditions.

Quasi-active power factor correction on flyback-based dc/dc converter

This paper presents a novel input current shaper based on a quasi-active power factor correction (PFC) scheme. In this method, high power factor and low harmonic content are achieved by providing an auxiliary PFC circuit with a driving voltage which is derived from a third winding of the transformer of a cascaded dc/dc flyback converter. It eliminates the use of active switch and control circuit for PFC. The auxiliary winding provides a controlled voltage-boost function for bulk capacitor without inducing a dead angle in the line current. Since the dc/dc converter operates at high switching frequency, the driving voltage is also of high switching frequency, which results in reducing the size of the magnetic components. Operating principles, analysis and experimental results of the proposed method are presented. Copyright © 2011 John Wiley & Sons, Ltd.

Torque ripple minimization with optimized i sx estimation in vector control of current source inverter induction motor

In variable speed applications of high-power induction motors, current source inverters are usually used instead of voltage source inverters. Power switches delay and switching losses in high-power ranges, prevents inverters to operate properly in high frequencies. So the voltage and current waveforms of the motor supply consist of high harmonic content causing a high-torque ripple. One of the parameters that influences the torque ripple most is the stator flux reference value. Motors do not usually operate in their nominal load. Therefore, the optimum value of the flux is not equal to the nominal value. In this paper, an optimal isx reference for vector control system of current source inverter fed induction motor is produced by applying a simple estimator. Simulation results show that torque ripple has been reduced, especially in the loads less than their nominal power, as significantly as power factor has been improved. Also flux reduction causes to noticeable reduction in core and switching losses.

An Analytical Study of Parametric Effects on Rotor—Vortex Interaction Noise

A numerical method for modelling the aerodynamic interaction between rotor blades and an independently generated vortex is developed. In this method, the Navier—Stokes/Euler equations are adopted for capturing the features of rotor blade—vortex interaction (BVI) flow and the overset grids technique is used for multi-zone solution. To incorporate the effects of the vortex in the solution, a generalized grid-velocity approach is presented to simplify the computations. The acoustic prediction is based on the well-known Ffowcs Williams-Hawkings (FW-H) equation for acoustic pressure. By this method developed, a parametric study is performed to examine the effects of the vortex strength, miss-distance, core-radius, oblique interaction, and interaction angle in a blade-shaft plane on BVI noise. The results indicate that the increase in miss-distance, core-radius, obliqueness of interaction, or interaction angle in a blade-shaft plane is an effective approach to reduce BVI noise, makes the BVI noise less impulsive (lower high harmonic content in noise energy) and increases the high noise encompassed area. However, the decrease in vortex strength changes only the magnitude of noise, not its distribution in different harmonics. The research also indicates that oblique interaction in a rotor plane has a significant effect on radiation directionality, while other parameters show little impact on it.

Development of a new fault-tolerant induction motor control strategy using an enhanced equivalent circuit model

Variable speed induction motor drives operating with an open circuit phase fault generally have a high harmonic current content and impose a large torque ripple on the load. These effects result from the unbalanced nature of the faulted machine, and under these conditions, the effects of machine and converter non-linearities become more pronounced. It is important to include these non-linearities when modelling drive systems which may operate under fault conditions, and developing fault ride-through control algorithms. This paper proposes a modelling method for induction motor drives which includes machine saturation and space harmonics effects as well as inverter non-linearities, which does not require significant computation times. Results from an experimental test rig are presented to validate the model. The second part of the paper describes how the model was used to develop a new fault ride through control strategy for a voltage-fed vector controlled drive. Experimental results demonstrate the improved drive behaviour with an open-circuit winding fault when controlled with the new strategy.

Power transformer additional load losses separation procedure

The proposed procedure is based on the fact that total transformer losses (PLL1,n), determined by short circuit test, can be separated into two components: the eddy current losses in the windings (PEC1,n) and stray flux losses (PSL1,n) in iron parts of construction as well as in the transformer tank walls. The total additional load losses, PLLd1 and PLLdh, are determined by short circuit test results, conducted at rated frequency (f1) and at increased harmonic frequency (fh=h*f1). Using so obtained total additional load losses, PLLd1 and PLLdh, which can be expressed in the form PLLdh=PEC1,n*h2 + PSL1,n*h, the corresponding rate additional load losses values PEC1,n and PSL1,n are derived. At the end, for given load with predefined high harmonics content, (Ih/I1n), relative to rated current, the total additional load losses value ΣPLLdh > PLLd1, is found. In such a way all harmonics up to hmax are taken into account.

Simulation and Analysis of a Multilevel Converter Topology for Solar PV Based Grid Connected Inverter

There has been a noticeable increase in use of Solar PV based systems for power generation, given its renewable nature. A solar PV based grid tie inverters are used for dc-ac conversion. The conventional line commutated ac-to-dc inverters have square-shaped line current which contains higher-order harmonics. The line current with the high harmonic contents generates EMI and moreover it causes more heating of the core of distribution/power transformers. Alternatively, PWM based inverters using MOSFET/IGBT switches are also used for the same purpose. However, apart from higher switching losses, the power handling capability and reliability of these devices are quite low in comparison to thyristors/SCR. Nevertheless, the conventional thyristor based forced commutated inverters are not suitable for PWM applications due to the problems of commutation circuits. A pure sinusoidal line current or waveform with low har- monic contents is the most desirable. In the present work, a multilevel line commutated inverter topology has been proposed and analyzed which improves the wave shape and hence reduces the total harmonic distortion (THD) of the line current in a grid tie line commutated inverter. The scheme has successfully been implemented and tested. Moreover, the performance of the proposed topology is far better than the conventional line-commutated inverter. It reduces THD, losses, switching stress and EMI.