| 1. |
- Hassanpoor, Arman
(författare)
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Modulation of Modular Multilevel Converters for HVDC Transmission
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The outstanding features of modular multilevel converters (MMC) have recently gained much attention in the high-voltage direct-current (HVDC) transmission field. Power quality, converter cost and system performance are three crucial aspects of HVDC MMCs which are directly linked to the converter modulation and switching schemes. High power quality and performance require high switching frequency and large cell capacitor whereas low switching frequency and small cell capacitor are needed to reduce the converter cost.The main objective of this thesis is to propose a practical switching method for HVDC MMCs which balances the aforementioned contradictory requirements. A mathematical analysis of the converter switching pattern, against the power quality and converter cost, has been conducted to formulate an optimization problem for MMCs. Different objective functions are studied for the formulated optimization problem such as converter loss minimization, voltage imbalance minimization and computational burden minimization. This thesis proposes three methods to address different objective functions. Ultimately, a real-time simulator has been built to practically verify and investigate the performance of the proposed methods in a realistic point-to-point HVDC link.The most significant outcome of this thesis is the tolerance band-based switching scheme which offers a direct control of the cell capacitor voltage, low power losses, and robust dynamic performance. As a result, the converter switching frequency can reach frequencies as low as 70 Hz (with the proposed cell tolerance band (CTB) method). A modified optimized CTB method is proposed to minimize the converter switching losses and it could reduce the converter switching losses by 60% in comparison to the conventional phase shifted carrier modulation method.It is concluded intelligent utilization of sorting algorithm can enable efficient HVDC station operation by reducing the converter cost.
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| 2. |
- Hassanpoor, Arman, et al.
(författare)
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Optimization-Based Cell Selection Method for Grid-Connected Modular Multilevel Converters
- 2016
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Ingår i: IEEE transactions on power electronics. - : IEEE. - 0885-8993 .- 1941-0107. ; 31:4, s. 2780-2790
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Tidskriftsartikel (refereegranskat)abstract
- Modular multilevel converters (MMCs) are widely used in different applications. Due to low-loss operation, compactness, and high modularity, MMC is extremely attractive for high-voltage direct-current (HVDC) transmission systems. 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 optimization 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 optimization 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. Eventually, the practical functionality of the proposed method is verified in a real-time digital simulator, RTDS, for a 512-level converter in a point to point HVDC link. Although this paper focuses on HVDC, the mathematical model is applicable for any MMC application.
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| 3. |
- Hassanpoor, Arman, et al.
(författare)
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Tolerance Band Adaptation Method for Dynamic Operation of Grid-Connected Modular Multilevel Converters
- 2016
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Ingår i: IEEE transactions on power electronics. - : IEEE. - 0885-8993 .- 1941-0107. ; :99, s. 1-1
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Tidskriftsartikel (refereegranskat)abstract
- The use of modular multilevel converters (MMC) in high-voltage direct current (HVDC) transmission systems has grown significantly in the past decade. The efficiency, cell capacitor voltage ripple and dynamic performance are three contradictory aspects of the MMC which are related to the converter switching scheme. Previously introduced tolerance band-based schemes enable efficient and simple control for grid-connected MMCs. This paper addresses the dynamic operation of tolerance band switching schemes by proposing a dynamic boundary setting technique for steady-state operation and a switching scheme scheduling controller for transient fault handling. The performance of proposed methods are validated in a realistic point-to-point HVDC link, modeled in real-time digital simulator (RTDS) where two converters with 512 cells per arm are implemented. Utilizing the proposed methods will enable efficient implementation of tolerance band-based schemes for different operating points, and also a robust transient fault handling.
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| 4. |
- Pourmohamadiyan, P., et al.
(författare)
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A new automatic spark generation system for gasoline engines
- 2016
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Ingår i: Proceedings, 2016 IEEE International Conference on Industrial Technology (ICIT) : the Howard Plaza Hotel Taipei, Taipei, Taiwan, 14-17 March, 2016. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781467380751 ; , s. 1016-1021
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Konferensbidrag (refereegranskat)abstract
- This paper presents a new automatic spark system for gasoline engines by reshaping the electric field in the combustion chamber through repositioning high voltage electrodes and applying changes in the electrodes geometry. This system provides better and wider discharge resulting in higher efficiency and ignition rate. Furthermore, a much simpler timing system, relying exclusively on built in control parameters, i.e. chamber pressure, temperature and piston position is needed. Numerical simulation of this newly-proposed design is conducted using a time-dependent solver. In particular, electrical field is investigated along the course line of a single piston. It has been observed that ignition is easier to control at the right piston position and crank angle which will obviously lead to better fuel economy and environmental protection.
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