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Phase-locked loop (PLL) detects the total harmonic distortion variation by considering the fundamental component of current and voltage. The conventional PLL harmonic monitoring method considers only the fundamental harmonic content to decide the islanding. This paper proposes technique by introducing modified synchronous reference frame PLL to detect island condition with support of harmonic variation at point of common coupling. The proposed method can detect state of island using fundamental 3rd, 5th, and 7th harmonic content to decide the islanding condition. Three different islanding conditions and five different non-islanding conditions were taken into consideration for analysing the proposed method. The proposed method was compared with the conventional PLL to evaluate the effectiveness. The simulation results were tested and validated with experiment results, and the proposed method is recommended as another effective alternative for islanding detection. Also the proposed method has been tested for multiple distributed generation sets connected to the grid for testing of effectiveness of technique.

Introduction. Electromagnetic safety of power grid facilities staff requires the exclusion of electromagnetic fields (EMF) harmful effects. EMF is evaluated by 50 Hz electric and magnetic fields (EF and MF) values in the framework of working conditions special assessment, and very rarely the analysis of the electromagnetic environment (EME) is carried out in depth. The aim of the study - EME hygienic assessment of power grid EHV facilities personnel workplace with adequate 50 Hz EF and MF levels evaluation as well as the analysis of EF and MF in the frequency range from 5 Hz to 500 Hz amplitude-frequency characteristics. Materials and methods. 50 Hz EF and MF values assessment was carried out on open switchgears (S) of substations and within sanitary breaks of 500 and 750 kV overhead power transmission lines (OTL). Measurements along to OTL trasses was performed using matrix-based method. Measurements and analysis of EF and MF values in 5-500 Hz frequency range amplitude-frequency characteristics were performed in the territory of 500 and 750 kV S. Results. Power frequency 50 Hz measurements results at 500 and 750 kV S ground-level personnel workplaces showed the presence of an excess of permissible limit values by EF intensity and the absence of an excess by MF. The measured EF values within 500 and 750 kV OTL sanitary gaps require limiting the working time of linemen due to the excess of the hygienic norms for full work shift, while the MP levels were almost completely within the standard values for persons not occupationally connected with electrical installations maintenance. MF and EE frequency range from 50 Hz to 500 Hz spectral characteristics analysis showed that 3rd harmonic percentage does not exceed 2.5% for EF and 6% for MF of the main level, the level of the 5th harmonic does not exceed 1% for EF and 3.5% for MF, the level of the 7th harmonic does not exceed 0.2% for EF and 0.8% for MF. These data show despite its low levels the contribution of MF different harmonics in a possible adverse impact on humane than EF corresponding harmonics. Conclusions. There was the confirmation of the previously justified use of the "matrix" scheme for of EF and MF values measurement along OTL routes. The relevance of to EF and MF all frequency components expos ure assessing possible health risk in extremely high voltage S territories and under OTL, based on international recommendations due to the lack of sanitary regulations in the Russian Federation for >50 Hz-30 kHz EF and MF, is shown.

This paper proposes a reduced 2nd, 3rd, 5th and 7th harmonic current of all power supply units and ac drives which effects of heating neutral cables and transformer. The commercial or automation building require the operation of many parallel-connected switch mode power supply and ac drive on the same bus and transformer. Such a system significantly increases the high neutral current and power quality problems on the distribution network. The existing system mainly consists of switch mode power supply and a three phase ac drive for compressor loads (common to HVAC applications). A passive power filter (PPF) and a low rating APF (Active Power Filter) at point of common coupling (PCC) are used to power quality enhancement in the distribution system. A PPF is designed to reduce the harmonics and to compensate the reactive power in the distribution system and the APF located at an upstream position near main distribution broads (MDB), it performs the compensation for harmonic current which is produced from all of drive and for remaining harmonics after the PPFs can been operation. The Hybrid Power Filter System (HPFs) is the combination of PPF and APF which mostly use for reducing harmonic currents and improving power quality of the system. Finally, using the HPFs to solve this problem, the results can reduce distortion and neutral current. Keywords: Harmonic current, HPFs, APFs, PPFs, Power quality

The demand for extra-high voltage cables in the transmission grid is growing in the wake of the energy transition and growing need for expansion of transmission lines. The challenge regarding the resonance behavior is that the capacitive cable characteristics lead to a shift of the network resonances to lower frequencies. Parallel resonances amplify the harmonic voltage, which can pose a danger to network elements and is critical for switching operations at low frequencies. The likelihood for stimulating parallel resonances increases at lower frequencies, especially for typical transmission network harmonics such as the 5th and 7th harmonic fed in by distribution networks. Therefore, the focus in this report lies on the low frequency parallel resonances. In order to determine to which busbar a cable can be connected without amplifying critical harmonic voltages, it is important to know at which frequencies parallel cabling resonances occur and how the different network components affect the cabling resonances. In this report, a sensitivity study on cabling resonances is carried out. The correlations are shown on the example of a honeycomb network reflecting a real 380 kV network. This honeycomb network allows general investigations and statements. The results show that especially the distance to the cable and the cabling degree have a high impact on the resonance behavior while the busbar characteristics have a lower impact.

This paper presents a method optimizing the thrust force of a Micro Electro Mechanical System (MEMS) Permanent Magnet Linear Motor, based on harmonic current injection. Fourier decomposition is implemented to the air gap flux density of the motor to derive the fitting expression of the thrust force dependent to exciting current. Through analyzing the thrust force ripple of sinusoidal current excitement, the paper comes up with the strategy of harmonic current injection to eliminate the ripple component in the thrust force waveform. Mathematical demonstration is given that injecting harmonic current can totally eliminate the ripple caused by odd component of vertical air gap magnetic induction intensity. Simulation verification is implemented based on the 3rd and 7th harmonic injection control strategy, proving that the method is feasible for the thrust ripple is reduced to 4.3% of the value before optimazation. Experimental results lead to the consistent conclusion that the strategy shows good steady-state and dynamic performance.

We constructed a Yb:fiber frequency comb for the generation of a vacuum-ultraviolet frequency comb via 7th harmonic generation. The spectral coverage and the noise performance of this comb are tailored for probing the 229 m Th nuclear transition.

The doubly salient electromagnetic machine (DSEM) has the advantages of simple and reliable structure while suffering from the problem of torque ripple due to the salient poles. In order to reduce the torque ripple and improve the torque performance, this paper proposes a harmonic current injection method combined with the optimized proportion of the armature magnetomotive force (MMF) and field MMF. The relationship between the copper loss and the total MMF is investigated. The influence of MMF proportion on the average torque and torque ripple is studied and the optimized MMF proportion is obtained at the fixed copper loss. The effect of harmonic current injection on torque performance is further analyzed on the basis of the optimized MMF proportion. The finite element analysis (FEA) result shows the torque ripple of the 12/10-pole DSEM is decreased more than 50% and the average torque keeps nearly unchanged after injecting the 5th or 7th harmonic current under the optimized MMF proportion, and the loss increment after the harmonic injection is less than 3%.

As the driving unit of AC motor, frequency conversion device is more and more widely used because of its good energy-saving effect and high speed control accuracy. However, because the circuit topology of the frequency conversion device contains a large number of non-linear switching semiconductor devices, resulting in a large amount of output current, which interferes with the load. Firstly, the mechanism of high-order harmonic generation in frequency converter is analyzed, and the expression of high-order harmonic generation is obtained by mathematical modeling. Secondly, in order to suppress high-order harmonic generation in frequency converter, a harmonic suppression scheme based on specific harmonic injection method is proposed, that is, to inject 5 and 7 harmonic compensation voltage into SPWM sinusoidal signal, so as to reduce the specific harmonic content of output current. The simulation and experiment of MATLAB/Simulink prove that the scheme can effectively reduce the specific sub-high harmonics generated by frequency devices, reduce the harmonic distortion rate and improve the power quality of output current.

This paper considers the calibration of Low-Power-Factor wattmeters in high voltage transformer no-load and load loss tests. The value of lowest power factor calibrated is evaluated in consideration of on-site test data and ability of uncertainty evaluation. The harmonic components of both testing current and voltage are measured in the field loss measurement. By analyzing the harmonic components, a nonsinusoidal current with a percentage of 3rd, 5th, 7th harmonic wave is applied for the laboratory calibration of Low-Power-Factor wattmeter in simulation of its on-site tests. There is a voltage unbalance in the field loss measurement. Unbalanced voltage is applied for Low-Power-Factor Wattmeters in comparison with balanced situations. For higher accuracy and resolution, the calibration systems of Low-Power-Factor wattmeters are improved with a nonsinusoidal current and unbalanced voltage standard.

A 75-83GHz waveguide band-pass filter is designed and fabricated for harmonic rejection of a multiplier chain used in a polarimetric automotive radar. The radar uses a multiplier/amplifier chain to achieve the desired signal at E-band from a source at X-band. It is shown that this filter can provide more than 50 dB signal suppression at 72 GHz (7th harmonic) and 35 dB suppression at 85.5 GHz (9th harmonic) with less than 1 dB ripples in the pass-band and less than 500 ps group delay. The filter is made of a perforated septum placed in the E-plane of a rectangular waveguide. Fabrication error was successfully minimized by using a brass sheet and a high precision laser cutter. This high-performance filter is shown to improve the performance of the FMCW MMW radar by significantly lowering the noise floor and eliminating other interference effects.

Multipulse rectifier systems are commonly used to reduce harmonic emission. However, they still require the installation of noncharacteristic harmonic filters to prevent harmful resonance between its high-pass filter and the system impedance. The advantage of a multipulse configuration-very low noncharacteristic harmonic emission-is, therefore, not fully utilized. In view of this shortcoming, a novel filter called the damped high-pass filter is proposed. The filter does not cause resonance at the noncharacteristic harmonic frequencies. As a result, traditional noncharacteristic 5th and 7th harmonic filters are no longer needed, resulting in significant cost and space savings for the multipulse systems. The core idea behind this filter is a frequency-dependent resistor block that provides high damping at the noncharacteristic harmonic frequencies. The design procedure for the proposed filter is presented. Performance and usefulness of the new filtering scheme has been demonstrated through comparative studies on two actual industry cases.

The Modular Multilevel Converter (MMC) has proved to be an attractive technology in medium and high voltage Static Synchronous Compensator (STATCOM) applications. Nevertheless, once reactive power compensation profile is not constant over time, there are periods that a MMC-STATCOM works below its nominal capacity. In these periods, the converter can be used to perform ancillary services, such as Active Power Filtering. This paper analyzes the thermal stresses in the capacitors and semiconductor devices (i.e. IGBTs and diodes). The analyses take into account reactive compensation and harmonic current compensation of 5th and 7th harmonic components of a MMC based STATCOM. In addition, the limits of harmonic compensation for 5th and 7th harmonic orders are analytically derived. The results demonstrated lower thermal stresses during Active Power Filtering than the traditional STATCOM operation. Moreover, the 5th harmonic compensation is the most stressed one among the cases studied in this work.

This paper proposes a method to control the 3rd harmonic current of the open-winding 10 poles 12 slot PMSM for the torque ripple reduction. The conventional 3-phase star connected PMSM can utilize 5th and 7th harmonic, however, the open-winding PMSM can utilize 3rd harmonic which is intentionally increased by the magnet arrangement of 10 poles 12 slots motor. This shows some experimental results which show the effectiveness of the 3rd harmonic current control by using the open-winding dual 3-phase inverter for the torque ripple reduction.

A front-end for multi-generator power system was recently proposed, which utilizes a single wye-delta (Y-Δ) transformer to shunt between the two 30° phase-shifted generator outputs. The shunt type phase-shift transformer front-end provides comparable 5th and 7th harmonic elimination performance to the conventional 12-pulse rectifier with more than 75% transformer size reduction. In this paper, a hybrid front end, which consists of the shunt Y-Δ transformer and an active power filter is proposed to further improve the power quality. In this configuration, 11th and 13th harmonics from nonlinear load are actively compensated by the active power filter and 5th and 7th harmonics are trapped by Y-Δ transformer. Theoretically, the performance of the proposed front end is equivalent to a traditional 24-pulse rectifier with a significant reduction in the overall size and weight, which makes it attractive to large-scale industrial and shipboard applications. The harmonic cancellation principle of the proposed front end is derived and verified by simulation and experimental results.

This paper proposes a medium voltage (MV) DC collection grid concept for large-scale PV power plant with a line commutated 12-pulse SCR converter and an integrated solid-state transformer (SST) for utility interface. DC power from the PV power plant sections is first processed via a line commutated 12-pulse converter employing an inverter grade SCR’s is interfaced to a SST powered by a higher frequency AC-AC converter. The objective of this paper is having the SST operate at medium frequency (360Hz or 720Hz), to reduce the transformer size/weight to 1/3rd to 1/5th. It is shown due to 12-pulse operation a high-quality utility line current can be achieved with the cancellation of 5th and 7th harmonic currents. The proposed approach is a robust current fed system, that improves power density, is simple to control with an integrated solid-state transformer. Simulation results presented on an example 150 kW PV power plant to validate the concept. Experimental results from a scale down laboratory type 1kW system are also discussed.

To solve the problems of harmonic current and torque ripple caused by PWM dead-time, inverter and sticking error of slotless motor windings, a technology of torque ripple suppression based fast harmonics decomposition algorithm is proposed in this paper. The method can extract the fundamental, 5th and 7th harmonic current in three sampling periods by simple matrix operation and has higher efficiency and accuracy. In the paper, based on harmonic mathematical model of PMSM, the harmonic current and torque ripple are suppressed by harmonic voltage injection. The paper presents detailed theoretical analysis. And simulation results and experimental results demonstrate that the method proposed is effective.

To identify the grid impedance accurately, high frequency non-characteristic harmonic voltages and currents are often injected into the grid by the power converter firstly. Then, digital signal filters are used to extract the high frequency voltages and currents from the sampled voltages and currents at the point of common coupling. Finally, the grid impedance can be calculated. Due to effects of the grid background harmonics, such as 5th and 7th harmonic, the grid impedance identification precision is usually poor. In this paper, to improve the grid impedance identification precision, a new complex coefficient filter-based grid impedance identification method is proposed considering the effects of the grid background harmonics. To reduce the influences of the grid background harmonics, such as 5th and 7th harmonic, an improved complex coefficient filter is proposed by adding a 5th and 7th harmonic suppression module to the conventional complex coefficient filter. The filter characteristic of the proposed complex coefficient filter is analyzed in detail to show its properties. Additionally, a simplified implementation method of the proposed complex coefficient filter is also proposed to reduce the calculation burden. Finally, simulation studies are carried out to further show the effectiveness of the proposed grid impedance identification method.

The optimization function of the filter compensating device has been determined, the purpose of which was the possibility of the harmonic distortion factor minimizing, the arguments of which are the power of individual filters. To analyze and compare the efficiency of the filter compensating device, quality indicators measurements of the electrical energy at an agricultural machine-building plant were made. Using the developed methodology for the filter-compensating devices optimal parameters calculating in the Mathcad software environment, the parameters selection and determination of two options of filter-compensating devices were made. According to the calculations, it was found that for the object under study, the most optimal, effective and economical device is a filter compensating one with a narrow-band filter tuned to the 5th harmonic and a wide-band filter of the 3rd order tuned to the 7th harmonic.

The vector control algorithm based on vector space decomposition (VSD) transformation method has a more flexible control freedom, which can control the fundamental and harmonic subspace separately. To this end, a current vector decoupling control algorithm for six-phase permanent magnet synchronous motor (PMSM) is designed. Using the proposed synchronous rotating coordinate transformation matrix, the fundamental and harmonic components in d−q subspace are changed into direct current (DC) component, only using the traditional proportional integral (PI) controller can meet the non-static difference adjustment, and the controller parameter design method is given by employing internal model principle. In addition, in order to remove the 5th and 7th harmonic components of stator current, the current PI controller parallel with resonant controller is employed in x−y subspace to realize the specific harmonic component compensation. Simulation results verify the effectiveness of current decoupling vector controller.

A 12-pulse rectifier has been widely used for harmonic mitigation in a large-scale power system. Recently, a shunt phase-shift transformer rectifier was proposed and already has been utilized in a marine transportation. For a power system equipped with multiple generators, the shunt phase-shift transformer front-end selectively eliminates 5th and 7th harmonic component with more than 75% size reduction over the conventional 12-pulse rectifier. However, a shunt phase-shift transformer rectifier requires additional source inductors to eliminate the undesired harmonics and the relationship between the source impedance and harmonic elimination has not been verified. This paper evaluates the effect of the line inductor on a harmonic cancellation performance of the shunt phase-shift transformer. An equivalent circuit analysis and a mathematical derivation of the shunt phase-shift transformer rectifier are provided and the relationship between the source impedance and harmonic cancellation is mathematically derived. The computer simulation and experimental test results from proto type hardware verify the equivalent model and the mathematical analysis.

This chapter analyzes the electromagnetic vibrations of 12-slot/10-pole SPM machines with both Sine-shaped and Sine+3rd-shaped PMs. Radial force density expressions are calculated by Maxwell stress tensor method under both no load and on load conditions. The magnitude of the lowest mode of the machines with Sine-shaped and Sine+3rd-shaped PMs, which is 2nd mode for 12-slot/10-pole ones, are investigated. Since the amplitude of the 5th (fundamental in electrical angle) airgap flux density is increased for Sine+3rd-shaped PMs compared with Sine-shaped PMs, the 2nd mode due to the interaction between the 5th PM field and 7th harmonic (either from slotting or armature field or both) is larger. However, it is found the 15th PM field (third harmonic in electrical angle) in Sine+3rd-shaped PMs can interact with 17th field to generate an negative amplitude of 2nd mode to cancel part of the increase due to 5th PM field, though the total magnitude of 2nd mode is about 8.8% larger compared with the Sine-shaped PMs under both no load and rated load conditions. Furthermore mode analysis and vibration behaviors are conducted through ANSYS. Finally, experiments are carried out on the prototyped 12-slot/10-pole SPM machines.

A five level H-bridge Shunt Active Power Filter that uses variable sampling frequency and a Genetic Algorithm fitted predictive control model to achieve excellent harmonic tracking with low device switching frequency, for More Electric Aircraft Electrical Power System (with a supply frequency in the range 360 Hz to 800 Hz) is proposed in this paper. The Predictive Control Shunt Active Power Filter is designed to track 5th and 7th harmonic current references up to 5600 Hz with nominal tracking errors less than ±2% while using a relatively low device switching frequency. The system is modelled and simulated in Matlab/Simulink and an analysis of the excellent tracking result using the Variable Sampling and Genetic Algorithm based model is provided.

As an important part of EMU (Electric Multiple Units), the auxiliary power supply system plays an important role in the normal operation of the vehicle. In order to improve the reliability of the auxiliary power supply system, this paper analyses the harmonics of the auxiliary inverter under nonlinear load and suggests that the 6th harmonic voltage components in the DQ synchronous rotating coordinate system can be controlled to achieve the simultaneous control of the 5th and 7th harmonic voltage components in the three-phase static coordinate system. The instantaneous voltage PIR (Proportion Integral Resonance) closed loop control method in DQ synchronous rotating coordinate system is researched to eliminate the voltage aberration caused by harmonics and ensure the quality of output voltage. Finally, the simulation results show that the design has achieved the desired objectives.

In this paper a particular problem related to transformation of AC voltage into DC voltage used in tram supply is considered. Variable component is always present in rectified voltage. Pulsation of rectified voltage is influenced by different factors. In 12-pulse system, where two secondary transformer windings are used (one delta-connected, the other star-connected), an additional factor increasing the pulsation is the unbalance of the output voltages at these windings. Tap changer may be used to compensate (equalize) those voltages and its setting is optimized here by applying ant colony algorithm. Different supply voltage variants have been considered, with particular attention paid to distorted voltage, containing 5th and 7th harmonic. The effects of applying ACO algorithm are demonstrated.

An improved methodology for selective harmonic detection and compensation (SHC) is proposed for smart inverters used as a Shunt Active Power Filter (SAPF). It is equally applicable in abnormal operating conditions such as in the event of an asymmetrical grid fault. A Multiple-Complex-Coefficient-Filter (MCCF) based Phase Locked Loop (PLL) is designed and tested for 5th and 7th harmonic compensation. Associated harmonic as well as fundamental current controllers in Synchronous Reference Frame (SRF) are designed and verified through simulation. Multiple linear rotating Proportional-Integral (PI) controllers are deployed for regulating the line current. MATLAB-SimPowerSystems package is used as a software platform for the demonstration of controllers' transient and steady-state performance. The proposed approach can selectively detect and effectively reduce harmonics to meet IEEE standards. This approach can also be extended to n number of harmonic compensation in a fast and accurate manner.

Nonlinear loads are one of the main factors which affect the output voltage quality of a stand-alone system. This paper proposes a novel control strategy with 5th and 7th harmonic elimination in the power winding voltage for a dual-stator brushless doubly fed induction generator (DSBDFIG), which feeds a three-phase rectifier load. System configuration and working principle are firstly provided in this paper. Then, the scheme of the control strategy was deduced and detailed. Simulation results present the steady-state and dynamic performance and validate the effectiveness of the proposed control method.

This manuscript describes harmonic generation in semiconductor superlattices, starting from a\ud Nonequilibrium Green's functions input to relaxation rate-type analytical approximations for the\ud Boltzmann Equation in which imperfections in the structure lead to asymmetric current flow and\ud scattering processes under forward and reverse bias. The resulting current-voltage curves and the\ud predicted consequences on harmonic generation, notably the development of even harmonics are in\ud good agreement with experiments. Significant output for frequencies close to 1 THz (7th harmonic)\ud at room temperature, after excitation by a 141 GHz input signal, demonstrate the potential of\ud superlattice devices for GHz-THz applications.

This paper proposes a new method combing the Six-phase permanent magnet synchronous generation (PMSG) with 12-pulse series diode rectifier with active harmonic elimination at DC side in order to improve the quality of the ac line currents. The proposed scheme draws nearly sinusoidal currents by controlling the two sets of diode bridge output currents to be triangular and out of phase using the active PWM auxiliary circuit injects directly compensation currents at DC side. The compensation strategy is analyzed. The simulation results demonstrate that the 11th 13th current harmonic in the Six-PMSG stator currents basically are eliminated, with multiply 5th, 7th harmonic content. But the total harmonic distortion (THD) of the Six-PMSG resultant current can be close to 1%.

Multipulse rectifier systems are commonly used to reduce harmonic emission. However, they still require the installation of non-characteristic harmonic filters to prevent harmful resonance between its high-pass filter and the system impedance. The advantage of a multipulse configuration — very low non-characteristic harmonic emission — is, therefore, not fully utilized. In view of this shortcoming, a novel filter called damped high-pass (DHP) filter is proposed. The filter does not cause resonance at the non-characteristic harmonic frequencies. As a result, traditional non-characteristic 5th and 7th harmonic filters are no longer needed, resulting in significant cost and space savings for the multipulse systems. The core idea behind this filter is a frequency-dependent resistor block that provides high damping at the non-characteristic harmonic frequencies. Design procedure for the proposed filter is presented. Performance and usefulness of the new filtering scheme has been demonstrated through comparative studies on two actual industry cases.

In this paper the effect of motor vibration problems on the dynamic performance and electrical power quality of water pumping stations is studied. A pump unit was tested for a full load and no load operating conditions. The dynamic results indicated that there is a problem of looseness in the motor base plate. The measurements were repeated again after achieving good support to the motor on its base plate. The results indicated that the vibration level decreased about 48% due to good support. The electrical power quality analysis showed that; the total harmonic distortion (THD) increases by about 1–2% due to the effect of bad motor vibration, and the 5th and 7th harmonic contents also increased by about 0.5–1.0%. Also the bad motor vibration caused large values of instantaneous flicker. These results indicated that the bad motor support causes many dynamics troubles and causes some power quality problems for the electrical feeder. Keywords: Dynamic analysis, Power quality problems, Water pumping stations, Harmonic analysis, Bad motor vibrations

With the rapid development of high-voltage large-capacity converters, multi-level inverter has been more widely used. Cascaded H-bridge multi-level inverter topology and using the trapezoidal modulation technique are described in this paper. The trapezoidal modulation of the H-bridge cascaded inverter is simulation studied with Matlab simulation software. This paper analyzes trapezoidal modulation techniques, how to establish the elimination of specific harmonics of nonlinear equations and the equations of Runge-Kutta algorithm to solve the problem, given in the different modulation to eliminate the 5th and 7th harmonic of the switching angle data. Finally, simulation results show the feasibility and correctness of the trapezoidal modulation of selective harmonic elimination technique.

The XUV free electron laser FLASH, has been recently operated in the high-gain harmonic generation (HGHG) mode. We characterized the laser-induced energy modulation, as well as the temporal profile of the seeded FEL pulses. FEL saturation was reached for the 7th harmonic of the 266 nm seed laser.

Selective Harmonic Elimination (SHE) is an established technique to eliminate unwanted harmonics that causes aliasing effect in communication systems and affects power quality in electrical systems. In this paper, an analytical approach for SHE is proposed for harmonic elimination in a multilevel inverter. Traditionally, numerical methods like Newton Raphson Algorithm are opted to solve the transcendental SHE equations. The disadvantage in iterative computation is overhead in computational effort and the solution time can be problematic in real-time operation. Additionally, the numerical methods are sensitive to initial values and produce just one solution depending on the initial values. It doesn't provide insight into the possible solution sets. The closed-form equations generate the appropriate transition angles, single or multiples and the modulation ratio can be programmed into a microcontroller to vary the fundamental while eliminating the targeted harmonics. The approach has been illustrated to eliminate up to 7th harmonic in a seven level single phase inverter and up to 11th in a three phase system (no triplen harmonic elimination). Simulation results are included to verify theoretical formulation. A low voltage seven level inverter was built with a H-bridge and the experimental results verify the theoretical findings. Results include both single phase and triplen systems.

Molecular high-order harmonic generation (HHG) spectra from H2 + and its application to the generation of the isolated attosecond pulses (IAPs) have been numerically investigated. Results show that (i) the 7th harmonic order is enhanced with the nuclei around the equilibrium internuclear, and as the internuclear distance increased, this enhanced harmonic produces a red-shift (even disappearance). Theoretical analyses show that the electronic transition between the ground and the 1st excited states is responsible for the red-shift enhanced harmonic. (ii) The harmonic spectra exhibit several maxima and minima, and a red-shift of these points is predicted as the internuclear distance increased. (iii) By properly choosing the internuclear distance, the harmonic yield is enhanced, and there is only the single quantum path contributing to the harmonic spectra. (iv) Further, by properly adding the half-cycle pulse as well as the spatial inhomogeneous effect, a 375 eV supercontinuum with a pulse enhancement of 3.9 dB and some attosecond X-ray pulses shorter than 60as can be produced.

Many studies have investigated the influence of harmonics on insulation life. A limited number of these studies address electrical tree growth characteristics while even fewer employ harmonics maintaining a constant peak voltage. This experimental study sought to quantitatively identify any distinguishing features of electrical tree growth characteristics as a consequence of harmonic content. The total harmonic distortion (THD) and waveshape (Ks) indices were varied to a maximum of 40% and 1.6 respectively. Electrical trees were developed in point-plane geometry using 2 m tip radius hypodermic needles and a 2 mm gap in epoxy resin (LY/HY 5052) samples. Upon electrical tree initiation, 50 Hz composite waveforms incorporating harmonic content were applied as the excitation waveform at a constant voltage of 14.4 kV peak for 2.5 hours. No change in the electrical tree growth characteristics was identified using the width/length ratio. Electrical tree growth resulting from low power quality reduced operational insulation life and decreased the Weibull shape parameter β with the 7th harmonic displaying particular characteristics worthy of further investigation. © 2010 IEEE.

Harmonic generation of a driving laser propagating across a laser ablation plasma serves for the diagnosis of multicomponent plumes. Here we study the contribution of atomic and nanoparticle precursors to the generation of coherent ultraviolet and vacuum ultraviolet light as low-order harmonics of the fundamental emission (1064 nm) of a Q-switched Nd:YAG laser in a nanosecond infrared ZnS laser ablation plasma. Odd harmonics from the 3rd up to the 9th order (118.2 nm) have been observed with distinct temporal and spatial characteristics which were determined by varying the delay between the ablation and driving nanosecond pulses and by spatially scanning the plasma with the focused driving beam propagating parallel to the target. At short distances from the target surface (≤1 mm), the harmonic intensity displays two temporal components peaked at around 250 ns and 10 μs. While the early component dies off quickly with increasing harmonic order and vanishes for the 9th order, the late component is notably intense for the 7th harmonic and is still clearly visible for the 9th. Spectral analysis of spontaneous plume emissions help to assign the origin of the two components. While the early plasma component is mainly constituted by neutral Zn atoms, the late component is mostly due to nanoparticles, which upon interaction with the driving laser are subject to breakup and ionization. With the aid of calculations of the phase matching integrals within the perturbative model of optical harmonic generation, these results illustrate how atom and nanoparticle populations, with differing temporal and spatial distributions within the ablation plasma, contribute to the nonlinear medium., Funding has been provided by Ministerio de Economía y Competitividad (MINECO) of Spain under Project CTQ2013-43086-P. I.L-Q., A.B-C. and M.O. thank respectively MINECO, for a FPI fellowship (BES-2011-044738), CSIC, for a JAE-TEC 2010 contract and CSIC for a contract. Fruitful discussions with Dr. Mikel Sanz and Prof. A. Gonzalez-Arroyo are acknowledged.

Intracavity high harmonic generation was utilized to generate high average-power coherent radiation at vacuum ultraviolet (vuv) wavelengths. A ytterbium-doped fiber-laser based master-oscillator power-amplifier (MOPA) system with a 10 MHz repetition frequency was developed and used as a driving laser for an external cavity. A series of odd-order harmonic radiations was generated extending down to ∼ 30 nm (41 eV in photon energy). The 7th harmonic radiation generated was centered at 149 nm and had an average output power of up to 0.5 mW. In this way, we developed a sub-mW coherent vuv-laser with a 10 MHz repetition frequency, which, if used as an excitation laser source for photo-electron spectroscopy, could improve the signal count-rate without deterioration of the spectral-resolution caused by space-charge effects.

To reduce the undesired 5th and 7th stator harmonic current in the six-phase permanent magnet synchronous motor (PMSM), an improved vector control algorithm was proposed based on vector space decomposition (VSD) transformation method, which can control the fundamental and harmonic subspace separately. To improve the traditional VSD technology, a novel synchronous rotating coordinate transformation matrix was presented in this paper, and only using the traditional PI controller in d-q subspace can meet the non-static difference adjustment, the controller parameter design method is given by employing internal model principle. Moreover, the current PI controller parallel with resonant controller is employed in x-y subspace to realize the specific 5th and 7th harmonic component compensation. In addition, a new six-phase SVPWM algorithm based on VSD transformation theory is also proposed. Simulation and experimental results verify the effectiveness of current decoupling vector controller.

Summary form only given. This paper presents a study of distributed passive harmonic filter design to minimize harmonic distortions caused by non-linear loads in residential customers. The main objectives in this study are: (i) to improve the power factor, (ii) to reduce current and voltage distortions to standard limits, and (iii) to reduce electrical losses. In this sense, several measurements that were carried out in some domestic customers of the metropolitan distribution grid of Belem City, in the North of Brazil, have characterized as main harmonic distribution current sources the 3rd, 5th, 7th harmonic components. According to the results obtained, and considering the impacts caused in the distribution grid, a distributed filtering strategy is proposed using passive tuned filters of low costs to be installed in the customers.

Harmonic distortion is often a challenge in marine vessel power systems due to the presence of large motor drives containing diode or thyristor rectifiers. Governing standards impose requirements on bus voltage Total Harmonic Distortion (THD) which can be demanding to fulfil. An attractive measure to reduce THD is to use 12-pulse rectifiers, as they are known to cancel the 5th and the 7th harmonic. However, the added cost and space of this solution compared with standard 6-pulse rectifiers is significant. This paper proposes to base propulsion motor drives on 6-pulse rectifiers, and mitigate harmonic problems by means of power electronic based active filters. A detailed numeric simulation model is developed for evaluating the performance of the topology. A case study system is defined consisting of two propulsion motor drives and two synchronous generators. The active filter greatly improves the bus voltage THD in all defined simulation cases. The performance is also better than a corresponding system using 12-pulse rectifiers and no active filter © 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

To satisfy the need for multi-MW rf sources in frequency ranges where commercial sources do not exist, a study was undertaken on a class of devices based on gyro-harmonic frequency multiplication. This mechanism relies upon adding energy in gyrating motion to a linear electron beam that traverses a rotating-mode TE111-mode drive cavity in a dc magnetic field. The beam then drifts along the magnetic field into a second cavity, operating in the TEn11-mode tuned to the nth harmonic of the drive cavity. Studies of this configuration have been carried out for 2 < n < 7. Results are given for multi-MW, efficient operation of a 7th harmonic device operating at 20 GHz, and a 2nd harmonic device operating at 22.4 GHz.

Harmonic filtering is required for 12 pulse rectifier-utility interface to meet IEEE 519 harmonic current limits. Passive filter techniques employ tuned L-C filters at dominant 11th and 13th harmonic frequencies. However, they also require 5th and 7th tuned filters to avoid series and parallel resonance conditions. State of the art active filtering solutions require high bandwidth and relatively large rating PWM inverters for harmonic filtering of 12 pulse rectifier loads. Thus existing passive and active harmonic filtering solutions are not cost-effective for high power 12 pulse rectifier loads. Dominant harmonic active filter (DHAF) based on square-wave inverters is proposed to cost-effectively meet IEEE 519 harmonic current limits for 12 pulse rectifier loads. The proposed DHAF system employs square-wave inverters switching at 5th and 7th harmonic frequencies, which are transformer coupled in series with 11th and 13th passive filters respectively. The square-wave inverters are controlled to provide 'harmonic isolation' between the supply and load at 5th and 7th harmonic frequencies. The square-wave inverters are rated 1%-2% of the load kVA rating. The proposed DHAF system eliminates the need for large kVAR rated and bulky 5th and 7th passive filters, delivers superior harmonic filtering performance, and provides cost-effective harmonic filtering solution. Simulation results are given to validate the 'harmonic isolation' feature at 5th and 7th harmonic frequencies, and also demonstrate harmonic filtering required to meet IEEE 519 harmonic current limits.

The aim of this paper is to present a technique to reduce the harmonics in output voltage of a single phase inverter. An investigation is carried out with a circuit based on paralleling of two inverters by using interface reactors. Sinusoidal pulse-width modulation is used to generate the gating signals of the inverters. There is a phase difference between the gating signals of parallel branches. By varying the phase difference, an analysis is done to find the best situation when maximum harmonic elements can be reduced. Another two analyses are done by varying frequency ratio and modulation index. A conclusion is made about the finest modulation index depending on RMS value of fundamental component and presence of the 3rd, 5th & 7th harmonic components. Relation between frequency ratio and a specific harmonic component is also studied. A new equation is established which can be used to eliminate up to certain harmonic components setting a specific frequency ratio.

This paper presents an improved direct power control (DPC) strategy for grid-connected voltage source inverter (VSI) under unbalanced and harmonic grid voltage conditions. Based on the mathematic model of VSI with the negative sequence, 5th and 7th harmonic voltage components consideration, a PI controller is used in the proposed DPC strategy to achieve the average output power regulation. Furthermore, vector PI controller with the resonant frequency tuned at the two times and six times grid fundamental frequency is adopted to regulate both negative and harmonic components, and then two alternative targets of the balanced/sinusoidal current and smooth active/reactive output power can be achieved. Finally, simulation results based on Matlab validate the availability of the proposed DPC strategy.

High harmonic generation (HHG) at multi-megahertz pulse repetition rates is challenging, since pulse energy is several orders of magnitudes lower for such lasers than for those conventionally used for the HHG: micro-joules instead of milli-joules. However we have observed the 5th and 7th harmonic (till approx. 17 eV) with 5 μJ pulses at 50 MHz repetition rate with frequency doubled Yb:YAG Innoslab amplifier. The single-pass HHG with the Innoslab amplifier at 20.8 MHz repetition rate was demonstrated [1]. For these experiments the nonlinear pulse compression was implemented.

It is shown that the lowest TE{sub {ital s},{ital l}} mode in a cylindrical waveguide at frequency {ital s}{omega}, with group velocity nearly identical to group velocity for the TE{sub 11} mode at frequency {omega}, is that with {ital s}=7, {ital l}=2. This allows coherent radiation to be generated at the seventh harmonic during electron autoresonance acceleration. Conditions are found where such co-generation of 7th harmonic power at 20GHz is possible with overall efficiency greater than 80{percent}. This mechanism could make possible high efficiency cm-wavelength high power rf sources suitable for driving a future multi-TeV electron-position collider. {copyright} {ital 1996 The American Physical Society.}

To make dynamic voltage restorer (DVR) compensate the low-order harmonic voltage, overcome the effects on system performance of digital control, and improve the voltage compensation effect, a dual closed-loop digital PR control strategy, consisting of voltage outer loop fundamental proportional resonant (PR) control and current inner loop low-order harmonic PR control is proposed. The discretization methods of PR controller are analysed, a detailed analysis and parameter design of the fundamental PR controller and the 3rd, 5th and 7th harmonic PR controller in the discrete domain are carried out. The analysis shows that the harmonic PR controller can effectively compensate for the 3rd, 5th and 7th harmonic voltage, the fundamental PR controlled can achieve zero steady-state error tracking and inhibit the effects on output voltage of load current, and digital control system has good dynamic response characteristics. Based on the theoretical analysis, 11KVA DVR prototype is developed and tested. The effectiveness and feasibility of the proposed control strategy are verified by experimental results.

In steel making industries, the electrical arc furnaces (EAFs) present the main non linear loads connected to the power supply. One of the problems associated with this and needed to be studied and solved is the harmonics produced by those furnaces. The solution of the problems requires study and analysis of the harmonics. This can be done by working a model for the furnace circuit. This model is used for studding real practical case in steel plant of Libyan Iron & Steel Company (LISCO), in Misurata [5], where six arc furnaces are available. There are some problems reported and observed for filter banks of SVC system of the furnaces [4]. One of these problems is a failure of capacitor units in 5th and 7th harmonic filter banks due to the overvoltages produced by the harmonics. These overvoltages shorten the life-time of the capacitor. To solve the problem; a redesign of shunt passive filters (filter substation) has been done to reduce the amount of harmonics and save the capacitor banks from the over voltages.

Summary form only given. Partial discharge (PD) monitoring is a key method of tracking fault progression and degradation of insulation systems. Recent research discovered that the harmonic regime experienced by the plant also affects the partial discharge pattern, questioning the conclusions about equipment health drawn from PD data. This paper presents the design and creation of an on-line system for harmonic circumstance monitoring of distribution cables, using only PD data. Based on machine learning techniques, the system can assess the prevalence of the 5th and 7th harmonic orders over the monitoring period. This information is key for asset managers to draw correct conclusions about the remaining life of polymeric cable insulation, and prevent overestimation of the degradation trend.

In this paper, the rectifier transformer third winding to install high-pass filter have been studied, and the calculating method of the high-pass filter parameters have been put forward. The power factor and the filter parameter of three series rectifier unit in a company are calculated, then it’s discovered that the practical operating parameter tallies with theoretical result and the practical power factor fits with the theory in one of the series of filters, and this attain the system requisition, so then demonstrates the parameter calculation method in this paper is correct. It is suggested that the capacitance capacity of the high-pass filter of the third winding in aluminum electrolyzation rectifier unit should be calculated according to meeting to the displacement factor compensation requisition, that is, cut-off frequency: 3th harmonic, resonance frequency: 7th harmonic, quality factor: 5 or so, m: 0.2 or so, resistance: ≤10Ω. The greater the filtering resistance, the stronger the harmonic impedance, which will affect the harmonic filtering effect.