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| 2. |
- Ahmed, Noman, et al.
(författare)
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Efficient Modeling of an MMC-Based Multiterminal DC System Employing Hybrid HVDC Breakers
- 2015
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Ingår i: IEEE Transactions on Power Delivery. - : IEEE. - 0885-8977 .- 1937-4208. ; 30:4, s. 1792-1801
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Tidskriftsartikel (refereegranskat)abstract
- The feasibility of future multiterminal dc (MTDC) systems depends largely on the capability to withstand dc-side faults. Simulation models of MTDC systems play a very important role in investigating these faults. For such studies, the test system needs to be accurate and computationally efficient. This paper proposes a detailed equivalent model of the modular multilevel converter (MMC), which is used to develop the MTDC test system. The proposed model is capable of representing the blocked-mode operation of the MMC, and can be used to study the balancing control of the capacitor voltages. In addition, the operation of the MMC when redundant submodules are included in the arms can also be studied. A simplified model of a hybrid high-voltage dc breaker is also developed. Hence, the developed test system is capable of accurately describing the behavior of the MMC-based MTDC system employing hybrid HVDC breakers, during fault conditions. Using time-domain simulations, permanent dc-side faults are studied in the MTDC system. In addition, a scheme to control the fault current through the MMC using thyristors on the ac side of the converter is proposed.
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| 3. |
- Ahmed, Noman, et al.
(författare)
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Performance of the modular multilevel converter with redundant submodules
- 2015
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Ingår i: IECON 2015 - 41st Annual Conference of the IEEE Industrial Electronics Society. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781479917624 ; , s. 3922-3927
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Konferensbidrag (refereegranskat)abstract
- The modular multilevel converter (MMC) is the state-of-the-art voltage-source converter (VSC) topology used for various power-conversion applications. In the MMC, submodule failures can occur due to various reasons. Therefore, additional submodules called the redundant submodules are included in the arms of the MMC to fulfill the fault-safe operation requirement. The performance of the MMC with redundant submodules has not been widely covered in the published literature. This paper investigates the performance of the MMC with redundant submodules in the arms. Two different control strategies are used and compared for integrating redundant submodules. The response of the MMC to a submodule failure for the two strategies is also studied. Moreover, the operation of the MMC with redundant submodules is validated experimentally using the converter prototype in the laboratory.
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| 4. |
- Antonopoulos, Antonios, 1984-, et al.
(författare)
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Optimal Selection of the Average Capacitor Voltage for Variable-Speed Drives With Modular Multilevel Converters
- 2015
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Ingår i: IEEE transactions on power electronics. - 0885-8993 .- 1941-0107. ; 30:1, s. 227-234
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Tidskriftsartikel (refereegranskat)abstract
- Variable-speed drives have reduced voltage requirementswhen operating below the base speed. In a modularmultilevel-converter-based (M2C-based) motor drive it is thenpossible to operate with reduced voltage in the submodulecapacitors, than at the base speed. In this sense, a greatercapacitor-voltage ripple can be accommodated, without exceedingthe maximum peak-capacitor voltage. This paper presents ananalytical investigation for the optimal selection of the averagecapacitor voltage for M2Cs, when the motor is operating withrated torque, below the base speed. This method does not requireany power exchange between the converter arms, so it keepsthe conduction losses at the minimum level. Additionally, themethod decreases the switching losses, due to the decreasedcapacitor-voltage level. The overall ratings of the converterremain the same as in the base-speed operation. It is shownthat this method can be applied at a speed range betweenthe base speed and down to approximately one third of it,i.e, an operating range that covers the requirements for typicalpump- and fan-type applications. The results obtained from theanalytical investigation are experimentally verified on a downscaledlaboratory prototype M2C.
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| 5. |
- Nikouei Harnefors, Mojgan, 1983-, et al.
(författare)
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Operation Under Fault Conditions of the Stacked Polyphase Bridges Converter
- 2016
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Konferensbidrag (refereegranskat)abstract
- The stacked polyphase bridges converter consists of several submodules that, on the input dc side, all are connected in series. Whereas controller designs presented in previous studies have been found promising for realizing equal voltage sharing between submodules, the survival and stability under fault conditions have not been studied. This paper presents a control strategy that enables survival of the converter after the occurrence of a sudden short circuit of a single transistor switch. The results are verified by simulations.
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| 6. |
- Nikouie Harnefors, Mojgan, et al.
(författare)
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Analysis of the dc-link stability for the stacked polyphase bridges converter
- 2015
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Ingår i: 2015 17th European Conference on Power Electronics and Applications (EPE'15 ECCE-Europe). - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- This paper presents an analysis of the capacitor voltage stability for a stacked polyphase bridges (SPB)type converter. The SPB converter comprises of several submodules which are connected in series.Therefore, stability of the dc-link voltage is very important to investigate. From the analysis, a correspondingcontroller and an analytical expression for stability are derived. The proposed controller andthe associated stability condition are verified in a simulation environment and on a small experimentalsetup.
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| 7. |
- Nikouie Harnefors, Mojgan, et al.
(författare)
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DC-link stability analysis and controller design for the stacked polyphase bridges converter
- 2017
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Ingår i: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 32:2, s. 1666-1674
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Tidskriftsartikel (refereegranskat)abstract
- The stacked polyphase bridges (SPB) converter consists of several submodules that all are connected in series to a voltage source. The total dc-link voltage should split in a balanced way among the submodules. This does not always occur inherently. This paper presents an analysis of the capacitor voltage stability for the SPB converter. From the analysis, criteria for stability are derived and three alternatives of a suitable balancing controller are designed. The proposed controller alternatives and their associated stability properties are verified on an experimental setup and by simulation.
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| 8. |
- Ali, Muhammad Taha, et al.
(författare)
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Effect of control parameters on infliction of sub-synchronous control interaction in DFIGs
- 2016
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Ingår i: 2016 IEEE International Conference on Power and Renewable Energy (ICPRE). - : IEEE conference proceedings. - 9781509030682 ; , s. 72-78
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Konferensbidrag (refereegranskat)abstract
- This research work deals with the analysis of sub-synchronous control interaction (SSCI) in doubly-fed induction generators (DFIGs). The time-invariant model of the DFIG is linearized to perform eigenvalue analysis and to obtain the participation factor of each state variable for unstable modes. The sensitivity of system eigenvalues related to sub-synchronous modes is analyzed with respect to all the proportional and integral parameters of the controllers in the rotor-side-converters and grid-side-converters. The major contribution of this research work is the outcomes based on eigenvalue analysis that clearly point out the control parameters to which sub-synchronous modes are highly sensitive. The effect of series compensation level on DFIG system and on the sensitivity of converter control parameters is also studied.
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| 9. |
- Ali, Muhammad Taha, et al.
(författare)
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Mitigation of Sub-Synchronous Control Interaction in DFIGs using a Power Oscillation Damper
- 2017
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Ingår i: 2017 IEEE Manchester PowerTech, Powertech 2017. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509042371
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Konferensbidrag (refereegranskat)abstract
- The aim of this research work is to analyse subsynchronous control interaction (SSCI) in doubly-fed induction generators (DFIGs) and to design a supplementary control technique for the mitigation of SSCI. A mathematical model of the DFIG is derived and linearized in order to perform an eigenvalue analysis. This analysis pinpoints the parameters of the system which are sensitive in making sub-synchronous modes unstable and hence are responsible for causing SSCI. A power oscillation damper (POD) is designed using a residue method to make the DFIG system immune to the SSCI. The POD control signal acts as a supplementary control, which is fed to the controller of the grid-side converter (GSC). The POD signal is applied to different summation junctions of the GSC controller in order to determine the best placement of the POD for effective mitigation of SSCI and for the increased damping of the system.
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| 10. |
- Ali, Muhammad Taha, et al.
(författare)
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Optimal tuning and placement of POD for SSCI mitigation in DFIG-based power system
- 2019
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Ingår i: 2019 IEEE Milan PowerTech, PowerTech 2019. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538647226
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Konferensbidrag (refereegranskat)abstract
- The phenomenon of sub-synchronous control interaction (SSCI) in doubly-fed induction generators (DFIGs) is investigated and the optimal tuning and placement of a power oscillation damper (POD) for its mitigation is proposed in this paper. The effect of the POD on the DFIG system is studied by placing it at all the summation junctions of rotor-side converter (RSC) and grid-side converter (GSC) controllers, turn by turn. Five local signals are examined as different input signals to the POD out of which three local signals gave promising results. These signals include the DFIG's active power, the magnitude of the DFIG's apparent power, and the magnitude of the current through the transmission line. Residues are calculated for each POD placement and for each input to the POD. The calculated residues are studied along with the root-locus plots to see the effect of the POD on the mitigation of SSCI and the stability of the DFIG-based system.
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