| 1. |
- Ahmed, Noman, et al.
(författare)
-
A computationally efficient continuous model for the modular multilevel converter
- 2014
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Ingår i: IEEE Journal of Emerging and Selected Topics in Power Electronics. - : IEEE. - 2168-6777. ; 2:4, s. 1139-1148
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Tidskriftsartikel (refereegranskat)abstract
- Simulation models of the modular multilevel converter (MMC) play a very important role for studying the dynamic performance. Detailed modeling of the MMC in electromagnetic transient simulation programs is cumbersome, as it requires high computational effort and simulation time. Several averaged or continuous models proposed in the literature lack the capability to describe the blocked state. This paper presents a continuous model, which is capable of accurately simulating the blocked state. This feature is very important for accurate simulation of faults. The model is generally applicable, although it is particularly useful in high-voltage dc applications.
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| 2. |
- Antonopoulos, Antonios, et al.
(författare)
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Modular multilevel converter AC motor drives with constant torque from zero to nominal speed
- 2014
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Ingår i: IEEE transactions on industry applications. - 0093-9994 .- 1939-9367. ; 50:3, s. 1982-1993
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Tidskriftsartikel (refereegranskat)abstract
- Modular multilevel converters are shown to have a great potential in the area of medium-voltage drives. Low-distortion output quantities combined with low average switching frequencies for the semiconductor devices create an ideal combination for very high-efficiency drives. However, the large number of devices and capacitors that have to conduct the fundamental-frequency current require more complex converter control techniques than its two-level counterpart. Special care needs to be taken for starting and operation at low speeds, where the low-frequency current may cause significant unbalance between the submodule capacitor voltages and disturb the output waveforms. In this paper, principles for converter operation with high torque in the whole speed range are investigated. Experimental results from a down-scaled 12-kVA prototype converter running a loaded motor at various speeds between standstill and the rated speed are also provided.
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| 3. |
- Ilves, Kalle, et al.
(författare)
-
A submodule implementation for parallel connection of capacitors in modular multilevel converters
- 2013
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Ingår i: Power Electronics and Applications (EPE), 2013 15th European Conference on.
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Konferensbidrag (refereegranskat)abstract
- The modular multilevel converter is a suitable converter topology for high-voltage high-power applications and consists of series-connected submodules. Typically, these submodules are half-bridges with dc capacitors. A voltage ripple in the submodule capacitors is inevitable due to the current flowing in the arms. The converter should therefore be controlled in such a way that the capacitor voltages are kept balanced and close to their nominal values over time. This paper presents a new submodule circuit which alleviates the balancing of the capacitor voltages. The proposed submodule circuit consists of two capacitors and eight switches, forming a three-level submodule. Ideally, the voltage and current rating of the switches can be chosen such that the combined power rating of the semiconductors is the same as for equivalent half-bridge submodules. The proposed submodule circuit provides the possibility of connecting the two capacitors in parallel when the intermediate voltage level is used. This will reduce the capacitor voltage ripple, especially at low switching frequencies and thus allow for a reduction of the size, weight, and cost of the submodule capacitors. The proposed submodule circuit is validated by both simulation results and experiments on a laboratory prototype. It is found that the parallel connection of the submodule capacitors will, in fact, significantly improve the balancing of the capacitor voltages.
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| 4. |
- Ilves, Kalle, et al.
(författare)
-
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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| 5. |
- Norrga, Staffan, 1968-, et al.
(författare)
-
Decoupled steady-state model of the modular multilevel converter with half-bridge cells
- 2012
-
Konferensbidrag (refereegranskat)abstract
- Modular multilevel converters, based on cascading of halfbridge converter cells, can combine low switching frequency with low harmonic interference. They can be designed for high operating voltages without direct series connection of semiconductor elements. This has led to a rapid adoption within high-power applications such as HVDC, STATCOM and railway interties. Analysing the operation of these converters in the frequency domain poses a few challenges due to the presence of significant low-order harmonic voltages in the cell capacitors. This paper presents a frequency-domain model of the MMC converter with halfbridge cells, based on a two-stage approach. First, the circuit equations are decoupled by a simple linear transformation, whereby the circuit schematic can be separated into a dc-side and an ac-side part. Second, the switching operation within the phase arms is modelled in the frequency domain by iterated convolution. The model is verified against a timedomain simulation of a converter with ratings valid for HVDC applications. It is shown that the proposed methodology, where all calculations are made in the frequency domain, can accurately reproduce the results from the simulation.
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| 6. |
- Norrga, Staffan, 1968-, et al.
(författare)
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Frequency-Domain Modeling of Modular Multilevel Converters With Application to Maximizing the Operating Region
- 2012
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Ingår i: IECON 2012 - 38th Annual Conference on IEEE Industrial Electronics Society. - : IEEE. - 9781467324212 ; , s. 4967-4972
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Konferensbidrag (refereegranskat)abstract
- Modular multilevel converters (MMC), based on cascading of half-bridge converter cells, can combine low switching frequency with low harmonic interference. They can be designed for high operating voltages without direct series connection of semiconductor elements. This has led to a rapid adoption within high-power applications such as high voltage direct current transmission, railway interties and medium voltage industrial motor drives. Analyzing the operation of these converters in the frequency domain poses a few challenges due to the presence of significant low-order harmonic voltages in the cell capacitors. This paper treats a frequency-domain methodology for computing inner variables of the MMC with half-bridge cells, based on a two-stage approach. First, the circuit equations are decoupled by a simple linear transformation, whereby the circuit schematic can be separated into a dc-side and an ac-side part. Second, the variables of the cell strings are computed in the frequency domain by iterated convolution. It is shown that the proposed methodology, where all calculations are made in the frequency domain, can accurately reproduce the results from a PSCAD simulation. Furthermore, the model is successfully employed as part of an optimization algorithm for maximizing the power handling capability of the converter by appropriately controlling the circulating current and zero-sequence ac-side voltage. Results from this work point to significant possibilities for improvement.
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| 7. |
- Ahmed, Noman, et al.
(författare)
-
Validation of the continuous model of the modular multilevel converter with blocking/deblocking capability
- 2012
-
Ingår i: AC and DC Power Transmission (ACDC 2012), 10th IET International Conference on. - : Institution of Engineering and Technology. - 9781849197007
-
Konferensbidrag (refereegranskat)abstract
- This paper presents the continuous model for the Modular Multilevel Converter (M2C). The model operates in two modes, either operating as a voltage source in deblocked mode or as a rectifying diode bridge in blocked mode. The model is validated by comparison with a detailed M2C model having 36 submodules per arm, using different control strategies. The comparison is based on time-domain simulations in PSCAD/EMTDC. The continuous model shows a very good agreement with the detailed model.
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| 8. |
- Hassanpoor, Arman, et al.
(författare)
-
Evaluation of different carrier-based PWM methods for modular multilevel converters for HVDC application
- 2012
-
Ingår i: IECON 2012 - 38th Annual Conference on IEEE Industrial Electronics Society. - : IEEE. - 9781467324212 ; , s. 388-393
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Konferensbidrag (refereegranskat)abstract
- The outstanding features of modular multilevel converters (M2C) make it attractive for high voltage direct current (HVDC) systems. In order to achieve high efficiency in HVDC converter stations, the switching frequency and the capacitor voltage ripple of the converter should be minimized. A suitable modulation algorithm should achieve an optimal tradeoff between these two requirements. This paper evaluates different carrier-based PWM algorithms and discusses the most challenging technical aspects of an efficient M2C. It is observed that decoupling the waveform synthesis from the selection of which cell to switch at each instant has beneficial impact on operation performance. The evaluation is done by time-domain simulation considering a grid connected, three-phase M2C converter and an advanced control system. Results of this study can be used for implementing more economical HVDC converters.
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| 9. |
- Hassanpoor, Arman, et al.
(författare)
-
Switching pulse pattern optimisation for modular multilevel converters
- 2014
-
Ingår i: 40th Annual Conference of the IEEE Industrial Electronics Society, IECON 2014. ; , s. 4722-4728
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Konferensbidrag (refereegranskat)abstract
- Modular multilevel converters (MMCs) are widely used in different applications such as high voltage direct current (HVDC) applications. The HVDC station loss is highly related to the converter switching pulse pattern which is generated by modulation algorithm and cell selection methods. This paper formulates the switching pulse pattern generation, as a versatile optimisation problem. The problem constraints and objectives are formulated for HVDC applications and compared with similar problems in the field of computer science. To overcome the computational complexity in solving the introduced optimisation problem, a heuristic method is proposed for cell selection algorithm. The method utilizes the current level in order to obtain lossless switching at zero-current crossings. The study of the proposed method, in a time-domain simulation platform, shows that the method can reduce the switching converter losses by 60% compared to carrier-based modulation, maintaining the same capacitor voltage ripple. Although this paper focuses on HVDC, the mathematical model is applicable for any MMC application.
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| 10. |
- Hassanpoor, Arman, et al.
(författare)
-
Tolerance-band modulation methods for modular multilevel converters
- 2013
-
Konferensbidrag (refereegranskat)abstract
- Modular multilevel converters (M2C) are increasingly used in high voltage direct current (HVDC) systems. The efficiency of M2Cs is highly related to the modulation method which determines the switching frequency and capacitor voltage ripple in the converter station. A new approach to modulation of M2C is presented in this paper. Tolerance-band methods are employed to obtain switching instants, and also cell selection. The proposed methods overcome the modulation problem for converters with few numbers of cells and also reduce the sorting efforts for cell balancing purposes while maintaining the cell-capacitor voltage limits. The evaluation is done by time-domain simulation by which the performance of each method is studied in both steady-state and transient cases. It is observed that using tolerance band methods not only reduces the switching frequency but also allows for handling severe fault cases in a grid connected system. Use of this method can reduce the switching losses and also allow for reduction of the cell capacitor size.
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| 11. |
- Ilves, Kalle, et al.
(författare)
-
Comparison of Cascaded Multilevel Converter Topologies for AC/ AC Conversion
- 2014
-
Ingår i: 2014 International Power Electronics Conference, IPEC-Hiroshima - ECCE Asia 2014. - : IEEE Computer Society. - 9781479927050 ; , s. 1087-1094
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Konferensbidrag (refereegranskat)abstract
- This paper presents a simplified qualitative comparison of previously presented cascaded multilevel converter topologies for ac-ac conversion with particular emphasis on motor drive applications. Performance criteria such as the pulsation of the stored energy in the cell capacitors and the total required semiconductor rating are derived by analytical methods. The main conclusion is that the back-to-back connected modular multilevel converter operates best at synchronous speed, whereas the modular matrix converter and Hexverter are better suited for low-frequency output. However, by injecting circulating currents in the phase arms the operating region can be extended for all of the studied topologies.
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| 12. |
- Ilves, Kalle, et al.
(författare)
-
On energy variations in modular multilevel converters with full-bridge submodules for Ac-Dc and Ac-Ac applications
- 2013
-
Ingår i: Power Electronics and Applications (EPE), 2013 15th European Conference on.
-
Konferensbidrag (refereegranskat)abstract
- The modular multilevel converter is a promising topology for high-voltage high-power applications. By the series-connection of submodules it can generate high-quality voltage waveforms with low harmonic distortion at low switching frequencies. The submodules are low-voltage converters with capacitive energy storages. These capacitive energy storages are a driving factor of the size, weight, and cost of the converter. For this reason it is important to ensure that the stored energy in the converter is distributed as evenly among the submodules as possible. In this paper it is found that during nominal operating conditions, a large amount of energy is moved back and forth between the upper and lower arms in the converter. These energy oscillations can, however, be reduced or even eliminated if an appropriate modulation index or voltage ratio is used. It is also found that an appropriate modulation index or voltage ratio can reduce the power rating of the semiconductors as well. The theoretical findings are validated by simulating two systems with different voltage ratios for ac-ac conversion.
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| 13. |
- Jin, Lebing, et al.
(författare)
-
Control and modulation of the stacked polyphase bridges inverter
- 2014
-
Ingår i: IEEE Energy Conversion Congress and Exposition. - : IEEE. - 9781479957767 ; , s. 3023-3029
-
Konferensbidrag (refereegranskat)abstract
- In order to meet the requirements of future electric vehicle (EV) drive systems, new converter topologies are required. The stacked polyphase bridges (SPB) inverter is a new topology which is well adapted to the needs for future EVs. In addition to low power losses, the SPB inverter also has fault tolerance ability and good dynamic behavior. This paper presents a further analysis of the control and modulation concept of the SPB inverter. Simulation results are used to verify the analysis conclusions.
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| 14. |
- Modéer, Tomas, 1979-, et al.
(författare)
-
High-voltage tapped-inductor buck converter auxiliary power supply for cascaded converter submodules
- 2012
-
Ingår i: 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012. - : IEEE. - 9781467308014 ; , s. 19-25
-
Konferensbidrag (refereegranskat)abstract
- This paper firstly presents a discussion of the requirements for an auxiliary power supply for high-power modular multilevel converter submodules. Next, some of the most challenging problems in designing a low power high voltage step-down converter are presented. Further, a suitable topology, the tapped-inductor buck converter, that overcomes most of the problems is analyzed. Both analytical expressions describing the operation and circuit simulations are presented. Finally, an experimental evaluation of a 3 kV, 100W prototype converter utilizing an autonomous high-voltage switch is presented.
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| 15. |
- Modeer, Tomas, 1979-, et al.
(författare)
-
Implementation and testing of high-power IGCT-based cascaded-converter cells
- 2014
-
Ingår i: Proc. Energy Conversion Congress and Exposition (ECCE), 2014 IEEE. - : IEEE. ; , s. 5355-5359
-
Konferensbidrag (refereegranskat)abstract
- This paper presents the design and implementation of cascaded-converters cells based on integrated gate-commutated thyristor (IGCT) half-bridges. The cell design is presented together with a discussion of means to supply gate drive power and as well as the cooling of the cell components. Also, the operation of the cells in a high-power resonant test circuit is presented.
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| 16. |
- Modéer, Tomas, 1979-, et al.
(författare)
-
Loss comparison of different sub-module implementations for modular multilevel converters in HVDC applications
- 2012
-
Ingår i: EPE Journal. - : European Power Electronics and Drives Association. - 0939-8368 .- 2376-9319. ; 22:3, s. 32-38
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a loss calculation and comparison between different submodule topologies and semiconductor choices for a Modular Multilevel Converter in a 1.1 GW, ± 320 kV HVDC application. Accordingly, a detailed analysis of the losses for three different M2C implementations using both insulated gate bipolar transistors (IGBTs) and integrated gatecommutated thyristors (IGCTs) is presented. The losses for six different submodule realizations are shown in a loss breakdown in Fig. 7. It shows that the very low conduction loss of the IGCT is to some degree offset by higher switching losses and extra turn-on snubber losses but that the IGCT implementations provide significantly lower losses than their IGBT counterparts. The loss break-down also shows that clamp-double submodules and full-bridge submodules suffer from approximately 25% and 50% additional losses respectively as compared to the half-bridge case. An experimental verification of the loss calculations has been performed using a down-scaled M2C prototype. The results show a very good agreement between calculations and measured losses.
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| 17. |
- Modeer, Tomas, 1979-, et al.
(författare)
-
Resonant Test Circuit for High-Power Cascaded Converter Submodules
- 2013
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Ingår i: Proc. European Conference on Power Electronics and Applications (EPE), 2013.. - : IEEE.
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a test circuit and methodology suitable for testing high-power half-bridge submodules such as would be used in cascaded converters for high-voltage dc converters. The circuit utilizes a series resonant tank and two half-bridge submodules with voltage and impedance cancellation in order to minimize hardware requirements.
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| 18. |
- Norrga, Staffan, 1968-, et al.
(författare)
-
A Novel Inverter Topology for Compact EV and HEV Drive Systems
- 2013
-
Ingår i: 39th Annual Conference of the IEEE Industrial Electronics Society, IECON 2013. - : IEEE. - 9781479902248 ; , s. 6590-6595
-
Konferensbidrag (refereegranskat)abstract
- This paper describes a new modular inverter topology suitable for compact drive systems in electric road vehicles. The topology is based on dc-side cascading of three-phase two level inverter bridges, each feeding a set of three-phase windings of a motor. This topology is compared by calculation to the known modular high-frequency (MHF) converter, and is found to have similar losses and semiconductor expenditure requirements. Simulations verify the dynamic and static properties of the converter in a realistic application.
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| 19. |
- Norrga, Staffan, 1968-, et al.
(författare)
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Converter Topologies for HVDC Grids
- 2014
-
Ingår i: ENERGYCON 2014 - IEEE International Energy Conference. - : IEEE Computer Society. - 9781479924493 ; , s. 1554-1561
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Konferensbidrag (refereegranskat)abstract
- HVDC grids have significant benefits and will likely play an important role in the future energy system. However, protection and fault handling aspects will be different from those of current ac transmission grids and point-to-point HVDC connections. Therefore, new power electronic solutions will be required. Different fault handling strategies are being discussed and the required converter hardware to implement these is identified. Also different converter topologies with the needed properties, mainly dc-side short-circuit handling capability, are described and compared.
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| 20. |
- Norrga, Staffan, 1968-, et al.
(författare)
-
INTERGRID - Enabling a sustainable energy system by large-scale intercontinental power transmission
- 2013
-
Ingår i: 2013 IEEE Power and Energy Society General Meeting (PES). - : IEEE. - 9781479913039 ; , s. 6672688-
-
Konferensbidrag (refereegranskat)abstract
- The current global energy supply system is clearly unsustainable in that it is largely based on combustion of fossil fuels. Apart from the fact that fossil fuels are a finite resource, their combustion contributes to carbon dioxide emissions which contribute to climate change that may have devastating consequences. Increased use of electricity as an energy carrier could enable a transition to a more sustainable energy system. The use of less carbon-intensive primary energy sources is however impeded by several factors related to the siting of generation. In a more sustainable energy system generation facilities need to be located very far from load centers. Nuclear power plants should be located far from densely populated areas in regions without seismic activity, for safety reasons. To counteract the temporal variability of uncontrollable renewable sources, such as wind and solar power, it is desired to pool the output from several plants over a very large area. The paper will discuss the potential and feasibility of a global overlay grid with the capability of solving the above problems. This grid would connect the continents and have capacity significantly higher than any present transmission facilities. This implies a rating of a single power corridor of tens or even hundreds of gigawatts.
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| 21. |
- Norrga, Staffan, 1968-, et al.
(författare)
-
Operating region extension for multilevel converters in HVDC applications by optimisation methods
- 2012
-
Ingår i: IET Conference Publications. - : Institution of Engineering and Technology. - 9781849197007
-
Konferensbidrag (refereegranskat)abstract
- Modular multilevel converters, based on cascading of halfbridge converter cells, can combine low switching frequency with low harmonic interference. They can be designed for high operating voltages without direct series connection of semiconductor elements. This has led to a rapid adoption within high-power applications such as high voltage direct current transmission. However, the overall hardware expenditure is generally greater than for conventional converters. Improving the operating range in the PQ-plane of the converter is thus desirable. In this work it is shown that optimisation of the internal variables of the converter can increase the power handling capability significantly for a given set of rating constraints. In this process optimal values for the circulating currents, the zero-sequence ac-side voltages and the average stored energy are sought. Also, a control algorithm is demonstrated by which the converter can be operated in the optimised operating point. Simulation results clearly indicate the feasibility of the proposed methodology.
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| 22. |
- Norrga, Staffan, 1968-, et al.
(författare)
-
Renewable Energy Sources for Electricity Generation
- 2012
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The use of conventional energy sources for electricity generation, such as fossil fuel combustion and nuclear power, is questioned because of environmental and safety issues and concerns about possible anthropogenic climate change. This has led to rapid developments in the field of renewable energy exploitation. Entire new fast-growing industries are formed to supply equipment for renewable power plants. The contribution from Swedish industry to this development has so far largely been limited to providing parts and components and in most cases no integrated power plants are offered. From a Swedish perspective an important question is therefore what measures are needed in terms of research and development to increase Swedish participation in the industries related to renewable power plants.Three renewable primary energy sources have been investigated with respect to their energy supply potential, the industries involved, the technical state-of-the-art and finally the state of academic research. These are wind power, PV solar power and geothermal power. Currently, wind power has by far the largest installed base worldwide of these (238 GW) and also has the lowest levelised cost of electricity (LCOE) with credible figures of 7 c€/kWh presented for onshore installations. PV solar power is second in terms of installed power at 67.3 GW but shows faster growth, thanks to rapidly decreasing cost of equipment. The LCOE figures are approaching those of wind power (10 c€/kWh for Southern Europe is recently reported), which should allow for further growth. Geothermal energy production has been exploited for decades, and the installed base has reached 10.7 GW. It shows attractive electricity cost figures thanks to high capacity factor. LCOE is highly dependent on the location, but figures in the range of 4 c€-11c€ have been reported, which implies a significant potential. In terms of installations in Sweden, wind power is by far the dominant of the studied sources, with the remaining two being of marginal significance currently.Regarding academic research to increase the industrial base within renewables in Sweden the following recommendations are given. For wind power this goal can be achieved by promoting research into generator, transformer, and power electronic converter concepts, in close cooperation with established or newly founded companies. As for PV solar power, likely the main potential for Swedish industry lies in seeking further openings in the field of balance-of-system (BOS) equipment, considering the extreme price pressure on PV cells and modules, which has effectively forced several Swedish PV module manufacturers out of business. Academic research should thus focus on BOS aspects, with the aim of reducing LCOE. Finally, for geothermal electricity generation careful monitoring of the area should be encouraged, both technically and in terms of business. This should allow for the identification of suitable areas for research. A particularly interesting aspect that applies to several kinds of renewable energy sources, due to their temporal and spatial variability, is the use of long-distance power transmission, especially high-voltage direct current (HVDC). This is a Swedish strength area with world-leading companies. Therefore, academic research should also focus on the connection of different types of large renewable energy plants to HVDC transmission links.
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| 23. |
- Norrga, Staffan, 1968-, et al.
(författare)
-
The polyphase cascaded-cell DC/DC converter
- 2013
-
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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| 24. |
- Tolstoy, Georg, et al.
(författare)
-
Elimination of vector changes due to sector changes with DTC
- 2014
-
Ingår i: 2014 16th European Conference on Power Electronics and Applications, EPE-ECCE Europe 2014. - : IEEE. - 9781479930159 ; , s. 6910748-
-
Konferensbidrag (refereegranskat)abstract
- In this paper it has been investigated if there is a possibility to reduce the switching frequency for a two-level inverter by improving the direct torque control (DTC) algorithm by adding a non-switching condition when a new sector is entered. It is believed that the DTC switching table can be improved by adding a non-switching condition when sector change occurs. This will reduce the number of switching actions by up to 12 per electrical rotation without interfering with the electrical machine performance.
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| 25. |
- Ängquist, Lennart, et al.
(författare)
-
Arm-current-based control of modular multilevel converters
- 2013
-
Ingår i: 2013 15th European Conference on Power Electronics and Applications, EPE 2013. - : IEEE. - 9781479901166 ; , s. 6631999-
-
Konferensbidrag (refereegranskat)abstract
- Inner control of a Modular Multilevel Converter (M2C) based on direct tolerance-band modulation of the arm currents has been studied. This approach is attractive because it allows low switching frequency, directly provides the desired arm-current waveform and enables fast protective actions at the same time as the complexity of the over-all control system is reduced. Issues related to common-mode voltage are discussed and supporting PSCAD simulations are presented together with some results from experiments with a reduced-power prototype converter.
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