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1 
Analysis and Design of New Harmonic Mitigation ApproachesAeloiza Matus, Eddy 1972 14 March 2013 (has links)
Numerous approaches have been proposed in order to resolve the problems of current harmonics in electrical distribution systems. The rapid development of power semiconductors along with the revolutionary advances on microprocessors consolidated the motor drives industry and with it a massive proliferation of nonlinear loads. It was thought that these very same technological advances would trigger an explosive development of harmonic solutions based on power electronics. Moreover, the introduction of the instantaneous active and reactive power theory or the socalled p, q theory which simplifies and gives more robustness to the control strategies of active filters reinforced this idea. Three decades have passed since the first IGBT was introduced in early 1980s, and active harmonic solutions are not the first choice to solve harmonic pollution in electrical distribution systems, mainly due to the high cost and the perception of low reliability. Given this scenario, in this work two main approaches are explored. First, the combination of an asymmetric 18pulse rectifier with a reduced KVA active harmonic filter to improve the performance under abnormal utility conditions. Second, an interleaved active harmonic filter using multiple inverters connected in parallel at the ac and dc size, which will allow for higher power ratings and power density increase.
The performance issues of the asymmetric 18pulse rectifier under unbalanced voltage and preexisting harmonic components are analyzed, as well as the current distortion improvement, achieved when an active power filter is introduced.
On the other hand, the high frequency harmonic cancellation when interleaved inverters are used, the circulation of zerosequence current and the impact of interleaving on dc bus capacitor are analyzed. Finally, some methods to mitigate the low frequency circulating currents based on eliminating the zerosequence component, and the introduction of common mode inductors to reduce the high frequency circulating current are studied.
Without a doubt the search for new costeffective topologies able to reach broader power levels and voltage ranges will continue emerging giving more alternatives to users. Moreover, extensive research on wide band gap devices such as Silicon Carbide (SiC) and Gallium Nitride (GaN), with which it is possible to reach higher voltage breakdown and at least an orderofmagnitude lower switching losses, makes the future more promising for active solutions.

2 
Harmonic impact of modern residential loads on distribution power system and mitigation solutionsWang, Hui Unknown Date
No description available.

3 
Modeling, Measurement and Mitigation of Power System HarmonicsNassif, Alexandre Unknown Date
No description available.

4 
Modeling, Measurement and Mitigation of Power System HarmonicsNassif, Alexandre 11 1900 (has links)
Power system harmonics and interharmonics are power quality concerns that have received a great deal of attention in recent years. These phenomena can have several adverse effects on power system operation. The main harmonic and interharmonic sources are devices based on power electronics.
An emerging class of harmonic sources is comprised of power electronicbased home appliances. These appliances are dispersed throughout the lowvoltage distribution system, and their collective impact can result in unacceptable levels of voltage distortion. The characterization of home appliances based on their harmonic currents is an important step toward understanding the impact of these devices. This thesis presents an evaluation of the relative severity of the harmonic currents from these devices, and the impact of the disparity of the harmonic current phase angles.
Typically, the voltage supplied to each harmonic source is already distorted. This distortion causes a change of the harmonic current magnitudes (traditionally referred to as the attenuation effect). Common harmonic analysis methods cannot take this variation into account because they use a typical harmonic current source model specified by a supply voltage having little or no distortion. This thesis characterizes the harmonic attenuation effect of power electronicbased appliances. One of the findings is that harmonic amplification, rather than attenuation, can occur under credible voltage conditions. This finding had not been made previously. In order to include the harmonic attenuation/amplification in appliance modeling, a measurementbased harmonic modeling technique is proposed.
One of the most economic and effective ways to mitigate harmonics in power systems is through the use of harmonic shunt passive filters. These filters can be of many topologies. Selecting these topologies is a task that, today, depends on the experience and judgment of the filter designer. An investigation is carried out on the common filter topologies, and the most costeffective topologies for mitigating harmonics are identified.
As many of the larger harmonic loads also generate interharmonics, interharmonics have become prevalent in today’s mediumvoltage distribution system. Mitigation cannot be carried out until the interharmonicsource location is known. A method for interharmonic source determination is proposed and then verified through simulation and field measurement studies.

5 
Conductive interferences from multiple ECmotor installation : To measure and mitigate harmonicsAitman, Victor January 2022 (has links)
Products produced by a Swedish company are requested to be investigated regarding their harmonic and interharmonic currents injected into the public supply system to comply with the Swedish standard SSEN IEC 6100032, Electromagnetic compatibility (EMC). On behalf of Systemair Sweden AB, this bachelor thesis aims firstly to investigate if their product, PAFEC 4225 WH (Air Curtain), complies with standard SSEN IEC 6100032, and if not, what measures should be taken; and secondly to develop a lowcost instrument for the measurement of harmonics and interharmonics according to standard IEC 6100047 related to the requirements on equipment used in standard SSEN IEC 6100032. To this purpose, the standards have been looked into thoroughly, the preconditions for measurements have been studied in detail, and external meetings with a consultant at Delta Development Technology AB have been performed. Measurements of the harmonic spectrum generated by PAFEC 4225 WH have been performed first at Systemair Sweden AB’s Technical center in Skinnskatteberg, and later at Delta Development in Västerås. After this, a lowcost instrument was developed, including hardware and software design and implementation. The hardware implementation consists of a circuit board designed using EasyEDA (an online PCB Design Tool), a NI myDAQ (a data acquisition device made by National Instruments), and an enclosure designed with Solidworks and made with a 3Dprinter. The software implementation was conducted using LabVIEW – a graphical programming language. A few measurements were performed using instruments complying IEC 6100047 at Delta Development, and later with the lowcost instrument. Different line chokes were measured. The results showed that a 15 mH line choke connected in series with each motor would make the PAFEC 4225 WH comply with SSEN IEC 6100032. The results from the lowcost instrument did not match Delta Developments results regarding harmonic and interharmonic content. The difference could be caused by unfinished algorithm, different measurements conditions, and missing antialiasingfilter. For the future work it is recommended that Systemair Sweden AB can either develop the lowcost instrument or buy an existing instrument that complies with IEC 6100047, to enable to do measurements that comply with SSEN IEC 6100032. One does also need to investigate the grid during low activity or consider buying a signal generator for the purpose of fulfilling the preconditions to enable measurements. It is also recommended that further measurements are performed with the proposed line choke installed to check for any change in performance of the product.

6 
Methods to Mitigate Harmonics in Residential Power Distribution SystemsBagheri, Pooya Unknown Date
No description available.

7 
Low Switching Frequency Pulse Width Modulation for Induction Motor DrivesTripathi, Avanish January 2017 (has links) (PDF)
Induction motor (IM) drives are employed in a wide range of industries due to low maintenance, improved efficiency and low emissions. Industrial installations of highpower IM drives rated up to 30 MW have been reported. The IM drives are also employed in ultra highspeed applications with shaft speeds as high as 500; 000 rpm. Certain applications of IM drives such as gas compressors demand high power at high speeds (e.g. 10 MW at 20; 000 rpm).
In highpower voltage source inverter (VSI) fed induction motor drives, the semiconductor devices experience high switching energy losses during switching transitions. Hence, the switching frequency is kept low in such highpower drives. In highspeed drives, the maximum modulation frequency is quite high. Hence, at high speeds and/or high power levels, the ratio of switching frequency to fundamental frequency (i.e. pulse number, P ) of the motor drive is quite low.
Induction motor drives, operating at lowpulse numbers, have significant loworder voltage harmonics in the output. These loworder voltage harmonics are not filtered adequately by the motor inductance, leading to high total harmonic distortion (THD) in the line current as well as loworder harmonic torques. The loworder harmonic torques may lead to severe torsional vibrations which may eventually damage the motor shaft. This thesis addresses numerous issues related to lowpulsenumber operation of VSI fed IM drives. In particular, optimal pulse width modulation (PWM) schemes for minimization of line current distortion and those for minimization of a set of loworder harmonic torques are proposed for twolevel and threelevel inverter fed IM drives.
Analytical evaluation of current ripple and torque ripple is well established for the induction motor drives operating at high pulse numbers. However, certain important assumptions made in this regard are not valid when the pulse number is low. An analytical method is proposed here for evaluation of current ripple and torque ripple in lowpulsenumber induction motor drives. The current and torque harmonic spectra can also be predicted using the proposed method. The analytical predictions of the proposed method are validated through simulations and experimental results on a 3:7kW induction motor drive, operated at low pulse numbers. The waveform symmetries, namely, halfwave symmetry (HWS), quarterwave symmetry (QWS) and threephase symmetry (TPS), are usually maintained in induction motor drives, operating at low switching frequencies. Lack of HWS is well known to introduce even harmonics in the line current. Impact of threephase symmetry on line current and torque harmonic spectra is analyzed in this thesis. When the TPS is preserved, there are no triplen frequency components in the line current and also no harmonic torques other than those of order 6, 12, 18 etc. While TPS ensures that the triplen harmonics in the threephase pole voltages are in phase, these triplen frequency harmonics form balanced sets of threephase voltages when TPS is not preserved. Hence, triplen frequency currents flow through the stator windings. These result in torque harmonics of order 2, 4, 6, 8, 10 etc., and not just integral multiples of 6. These findings are well supported by simulation and experimental results.
One can see that two types of pole voltage waveforms are possible, when all waveform symmetries (i.e. HWS, TPS and QWS) are preserved in a twolevel inverter, These are termed as typeA and typeB waveforms here. Also, QWS could be relaxed, while maintaining HWS and TPS, leading to yet another type of pole voltage waveform. Optimal switching angles to minimize line current THD are reported for all three types of pole voltage waveforms. Theoretical and experimental results on a 3:7kW IM drive show that optimal typeA PWM and optimal typeB PWM are better than each other in different ranges of modulation at any given low pulse number. In terms of current THD, the optimal PWM without QWS is found to be close to the better one between optimal typeA and optimal typeB at any modulation index for a given P . A combined optimal PWM to minimize THD is proposed, which utilizes the superior one between optimal typeA and optimal typeB at any given modulation index and pulse number. The performance of combined optimal PWM is shown to be better than those of synchronous sinetriangle (ST) PWM and selective harmonic elimination (SHE) PWM through simulations and experiments over a wide range of speed.
A frequency domain (FD) based and another synchronous reference frame (SRF) based optimal PWM techniques are proposed to minimize loworder harmonic torques. The objective here is to minimize the combined value of loworder harmonic torques of order 6, 12, 18, ..., 6(N 1), where N is the number of switching angles per quarter cycle. The FD based optimal PWM is independent of load and machine parameters while the SRF based method considers both load and machine parameters. The offline calculations are much simpler in
case of FD based optimal PWM than in case of SRF based optimal PWM. The performance
of the two schemes are comparable and are much superior to those of synchronous ST PWM
and SHE PWM in terms of loworder harmonic torques as shown by the simulation and
experimental results presented over a wide range of fundamental frequency,
The proposed optimal PWM methods for two levelinverter fed motor drives to minimize
the line current distortion and loworder torque harmonics, are extended to neutral point clamped (NPC) threelevel inverter fed drive. The proposed optimal PWM methods for the NPC inverter are compared with ST PWM and SHE PWM, having the same number of
switching angles per quarter. Simulation and experimental results on a 3:7kW induction
motor drive demonstrate the superior performance of proposed optimal PWM schemes over ST PWM and SHE PWM schemes.
The di_erent optimal PWM schemes proposed for twolevel and threelevel inverter fed
drives, having di_erent objective functions and constraints, are all analyzed from a space vector perspective. The threephase PWM waveforms are seen as a sequence of voltage
vector applied in each case. The space vector analysis leads to determination of optimal
vector sequences, fast o_ine calculation of optimal switching angles and e_cient digital
implementation of the proposed optimal PWM schemes. A hybrid PWM scheme is proposed
for twolevel inverter fed IM drive, having a maximum switching frequency of 250 Hz. The
proposed hybrid PWM utilizes ST PWM at a _xed frequency of 250 Hz at low speeds. This
method employs the optimal vector sequence to minimize the current THD at any speed in
the medium and high speed ranges. The proposed method is shown to reduce both THD as well as machine losses signi_cantly, over a wide range of speed, compared to ST PWM
Position sensorless vector control of IM drive also becomes challenging when the ratio
of inverter switching frequency to maximum modulation frequency is low. An improved
procedure to design current controllers, and a closedloop ux estimator are reviewed. These are utilized to design and implement successfully a position sensorless vector controlled IM drive, modulated with asynchronous third harmonic injected (THI) PWM at a constant switching frequency of 500 Hz. Sensorless vector control is also implemented successfully, when the inverter is modulated with synchronized THI PWM and the maximum switching frequency is limited to 500 Hz.

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