| 1. |
- Antonopoulos, Antonios, et al.
(författare)
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Optimal selection of the average capacitor voltage for modular multilevel converters
- 2013
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Ingår i: 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013. - : IEEE. - 9781479903351 ; , s. 3368-3374
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Konferensbidrag (refereegranskat)abstract
- Variable-speed drives have reduced voltage requirements when operating below the base speed. In a modular-multilevel-converter-based (M2C-based) motor drive it is then possible to operate with reduced voltage in the submodule capacitors, than at the base speed. In this sense, a greater capacitor-voltage ripple can be accommodated, without exceeding the maximum peak-capacitor voltage. This paper presents an analytical investigation for the optimal selection of the average capacitor voltage for M2Cs, when the motor is operating with rated torque, below the base speed. This method does not require any power exchange between the converter arms, so it keeps the conduction losses at the minimum level. Additionally, the method decreases the switching losses, due to the decreased capacitor-voltage level. The overall ratings of the converter remain the same as in the base-speed operation. It is shown that this method can be applied at a speed range between the base speed and down to approximately one third of it, i.e, an operating range that covers the requirements for typical pump- and fan-type applications. The results obtained from the analytical investigation are experimentally verified on a down-scaled laboratory prototype M2C.
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| 2. |
- Ilves, Kalle, et al.
(författare)
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Analysis and operation of modular multilevel converters with phase-shifted carrier PWM
- 2013
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Ingår i: 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013. - : IEEE. - 9781479903351 ; , s. 396-403
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Konferensbidrag (refereegranskat)abstract
- The modular multilevel converter is a suitable topology for high-voltage high-power applications since the cascaded submodules can generate high-voltage waveforms with excellent harmonic performance at low switching frequencies. Many publications have been presented on the modulation and control of this converter type, some of which are based on phase-shifted carrier modulation. This paper presents an analysis of how the switching frequency affects the capacitor voltages, circulating current and alternating voltage at phase-shifted carrier modulation. It is found that integer multiples of the fundamental frequency should be avoided as they can cause the capacitor voltages to diverge. Suitable switching frequencies are then defined for which the arm and line quantities will be periodic and symmetric in the upper and lower arms. The theoretical results are then validated by both simulations and experimental results.
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| 3. |
- Kostov, Konstantin S., et al.
(författare)
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The input impedance of common mode and differential mode noise separators
- 2013
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Ingår i: 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013. - 9781479903351 ; , s. 1688-1695
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Konferensbidrag (refereegranskat)abstract
- This paper discusses the Δ-networks and other circuits designed to separate the conducted electromagnetic interference (EMI) into its common mode (CM) and differential mode (DM) components. The input impedances of CM/DM separators must be 50 Ω resistive in the measurement frequency band and they must be independent of the values of the noise signals and noise source impedances. The conditions for achieving such input impedances are derived. It is shown that many of the proposed separators, including the Δ-network suggested in the CISPR 16 standard, do not fulfill the input impedance requirement. This leads to unreliable CM and DM measurements, and consequently, to EMI filter oversizing and design by trial-and-error.
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| 4. |
- Norrga, Staffan, 1968-, et al.
(författare)
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The polyphase cascaded-cell DC/DC converter
- 2013
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Ingår i: Energy Conversion Congress and Exposition (ECCE), 2013 IEEE. - : IEEE. - 9781479903351 ; , s. 4082-4088
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Konferensbidrag (refereegranskat)abstract
- This paper describes a new type of unisolated dc/dc converter employing cascaded converter cells, and its operation is analyzed. The topology and the operation of the converter have similarities with the modular multilevel converter for polyphase ac/dc conversion, but the ac voltages and currents are in this case only employed for redistributing power within the converter. It is shown how the nominal modulation indices for ac and dc voltage influence the semiconductor expenditure for the converter. A methodology for optimizing the design of the converter with regard to the required silicon area is devised. It is found that at voltage conversion ratios close to unity it is preferable to use a combination of full-bridge cells and half-bridge cells. Under such circumstances the proposed converter can offer lower semiconductor expenditure than a conventional buck converter.
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| 5. |
- Svechkarenko, D.V., et al.
(författare)
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Finite element analysis of end ring impedance in squirrel cage induction machines
- 2013
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Ingår i: 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013. - 9781479903351 ; , s. 254-259
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Konferensbidrag (refereegranskat)abstract
- In squirrel cage rotors of induction machines with unconventional end region structure, the three-dimensional effects can be more pronounced as compared to conventional induction machines. As a result, the rotor impedance and machine power factor are affected by the design of the end ring and its supporting structure. To be able to account for this effect, three-dimensional finite element (3D FE) analysis is required. In this paper, the steady state 3D FE analyses are employed to identify the equivalent circuit parameters. Further, the internal power factor and the rotor bar and end ring impedances are investigated. It is further presented how the findings of the 3D FE study can be implemented in two-dimensional (2D) FE model in the distributed circuit.
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| 6. |
- Tenca, Pierluigi, et al.
(författare)
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Fault tolerant cost-effective carrierless stochastic synthesis of voltages and currents in multi-Cell multilevel converters via the central limit theorem
- 2013
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Ingår i: 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013. - : IEEE. - 9781479903351 ; , s. 1732-1739
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Konferensbidrag (refereegranskat)abstract
- The paper presents with experimental evidence a highly fault tolerant, cost-effective and carrierless solution to synthesize voltages (or currents) across the series (or parallel) connection of several voltage-source (or current-source) cells. Hundreds of voltage-source cells already characterize modern multilevel HVDC converters and structures based on current-source cells could become industrially meaningful too, if sufficient advancements in semiconductor and magnetic materials will occur. Exactly by relying on a large number of cells, the key approach is characterized by an unconventional absence of any determinism. The voltages (or currents) of all cells are generated as discrete independent random variables whose distribution is parameterized by the desired reference waveform to be synthesized. This is a radical difference from the already existing random PWM modulations, where only the switching instants are aleatory. The essence of the proposed method lies in observing that multilevel converters, which synthesize the desired waveforms through additive linear combinations (e.g. the simplest sum) of several elementary contributions, become naturally ruled by the Central Limit Theorem of the theory of probablity. Such a fundamental law of nature assures also that the greater the number of cells, the more the waveform synthesis becomes inherently robust, fault-tolerant and accurate. This property strikingly differs from those of deterministic centrally ruled modulations and it is also achieved with reduced hardware complexity and cost. The proposed method benefits from emerging technologies employing smaller mass-produced cells based on devices capable of improved switching characteristics, like SiC or GaN, thereby suiting design philosophies characterized by a high number of cost-optimized standard elementary units. Equally important, the proposed synthesis eliminates most physical communication channels (e.g. optical fibers) among the controller and the switches, thereby greatly improving the system reliability. The paper introduces also a hybrid variant of the method conceived for fewer cells.
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| 7. |
- Zhao, Shuang, 1982-, et al.
(författare)
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Off-Vehicle Evaluation of Active Oscillation Damping Schemes
- 2013
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Ingår i: 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013. - 9781479903351
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Konferensbidrag (refereegranskat)abstract
- Torsional drivetrains oscillations is a well known problem in electrical or hybrid electric drivetrains which may greatly influence the driving comfort. An experimental testing setup that can be used to design and evaluate active oscillation damping schemes is proposed in this paper. Instead of in-vehicle test, the drivetrain transmission is emulated from mathematic models, executed by a servo drive which is connected to the physical electrical drive system. The proposed setup functions as a hardware-in-the-loop simulator and can be easily adjusted to simulate any drivetrains without additional cost.
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