175 research outputs found
Modulation, efficiency and lifetime of two-level and multilevel converters for a hydropower application
No full textAlong with the integration of the renewable energy in the electrical grid, the pumped-storage hydropower has gained more and more attention due to its fast response and energy storage ability. To have a higher overall efficiency and more flexibility of the system, variable speed is preferred in the operation of the pumped-storage hydropower applications. The key component for the variable speed pumped-storage hydropower application is the full-size power converter, which is the main study object in this work.Different converter topologies, such as the two-level converter, the neutral point clamped converter, and the modular multilevel converter, have been investigated in this study. The simulation and experimental results verify the feasibility of the studied modulation and control methods for different converter topologies. The nine-level modular multilevel converter needs four times the amount of the power modules compared with the two-level converter, not to mention the extra submodule capacitors and arm inductors in the nine-level modular multilevel converter. However, the nine-level modular multilevel converter shows the best efficiency of 99.37% at nominal power in the loss study, while the classical two-level converter shows an efficiency of 98.44%. At the end, a lifetime study is conducted for power switches inside a modular multilevel converter, and it is found that with the used semiconductors design, i.e., the semiconductors have an RMS current value that of half of its stated maximum value, the lifetime requirement of 30 years can always be fulfilled
Modulation, efficiency and lifetime of two-level and multilevel converters for a hydropower application [Elektronisk resurs]
No full textAlong with the integration of the renewable energy in the electrical grid, the pumped-storage hydropower has gained more and more attention due to its fast response and energy storage ability. To have a higher overall efficiency and more flexibility of the system, variable speed is preferred in the operation of the pumped-storage hydropower applications. The key component for the variable speed pumped-storage hydropower application is the full-size power converter, which is the main study object in this work. Different converter topologies, such as the two-level converter, the neutral point clamped converter, and the modular multilevel converter, have been investigated in this study. The simulation and experimental results verify the feasibility of the studied modulation and control methods for different converter topologies. The nine-level modular multilevel converter needs four times the amount of the power modules compared with the two-level converter, not to mention the extra submodule capacitors and arm inductors in the nine-level modular multilevel converter. However, the nine-level modular multilevel converter shows the best efficiency of 99.37% at nominal power in the loss study, while the classical two-level converter shows an efficiency of 98.44%. At the end, a lifetime study is conducted for power switches inside a modular multilevel converter, and it is found that with the used semiconductors design, i.e., the semiconductors have an RMS current value that of half of its stated maximum value, the lifetime requirement of 30 years can always be fulfilled
Lifetime Analysis of Power Switches in a Back-to-back MMC for Variable Speed Hydropower Application
No full textThis paper studies the lifetime of the power switches in a back-to-back modular multilevel converter (MMC) for a variable speed hydropower application. In this study, to accurately evaluate the lifetime of the power switches, a detailed simulation model considering the hydro turbine model, the converter model, and the machine model is developed. The controller for the machine and the modulator for the converter are simulated in Matlab Simulink while the electrical behavior of the converter and mechanical behavior of the machine are simulated in PLECS. Furthermore, a mission profile based lifetime evaluation is conducted
Thermal modelling of a mutlichip IGBT power module
No full textLife time prediction and thermal management are among the key issues regarding the performance of today\u27s semiconductor devices. And a fast and accurate thermal model can be used to tackle those problems more efficiently. In this paper, different thermal models of an IGBT power module have been established and compared. Firstly, a 3D finite element method (FEM) model is simulated in COMSOL. And then, a lumped parameter thermal model with considering different aspects (heat spreading and thermal coupling) is derived. The simulation indicates that the proposed model can achieve a relatively accurate result within a short simulation time
A Model Predictive Control Method with Adaptive Weighting Factors for Enhancing Performance of Modular Multilevel Converters
No full textThis article introduces an approach to enhance the performance of modular multilevel converters (MMCs) by utilizing the direct model predictive control (MPC) strategy. The novel MPC method presented here incorporates a dynamic cost function, which adapts weighting factors according to the varying submodule (SM) capacitor voltages in the MMC. Through thorough simulation and experimental analysis, it is evident that the proposed MPC technique improves the performance of the MMC operation across a range of modulation indices. In addition, the approach achieves the desired 2N+1 phase output voltage level, which reduces the total harmonics distortion (THD) in the output voltage and current. Furthermore, the MPC controller demonstrates robustness against potential errors in system parameter estimation through the simulation results
Modular multilevel converter control with using a general space vector PWM method in medium voltage hydro power application
No full textThis paper studies a generalized space vector PWM (SVPWM) method for modulating the modular mul-tilevel converter (MMC) for a medium voltage hydropower application. In addition to the modulation of the MMC, the circulating current control and the submodule capacitor voltage balancing are included in the study. The simulation and experimental results show the feasibility of using the generalized SVPWM method for controlling the MMC. Furthermore, the loss study shows that the switching loss in the MMC can be reduced with 28% when a modification of the generalized SVPWM method is utilized, thus, the total efficiency of the converter can be increased
Shear-slip behaviour of prefabricated composite shear stud connectors in composite bridges
No full textThis paper has investigated the shear-slip behaviour of an innovative prefabricated composite shear stud (PCSS) connector and its application in the prefabricated steel–concrete composite bridges. A series of push-out tests are carried out on a total of 12 specimens, including 6 PCSS specimens and 6 conventional shear stud (CSS) specimens. Further comparison has been carried out between the test result and the data available from the literature. Based on the test, a high-resolution finite element (FE) analysis has been performed to reveal the load transfer mechanism of the PCSS connector at the component-level. After that, an advanced FE model has been established and validated by a full-scale test of the prefabricated composite bridge using the PCSS. With the FE model, the load-slip behaviour and slip distribution are investigated in details. The result highlights the enhanced shear capacity and ductility of the PCSS specimens compared with the CSS specimens, as well as the feasibility of PCSS connectors in composite bridges. Meanwhile, it is further revealed by the detailed investigation that the enhancement could be attributed to the lateral constraint on the concrete by the vertical steel plate in the PCSS. Besides, it is also found that the load-slip behaviour of composite bridges using the PCSS is influenced by the cracking at the seam between deck blocks. Consequently, abrupt changes can be found in the load-slip curve once the cracking occurs, which differs from the traditional composite bridges.Accepted Author ManuscriptSteel & Composite Structure
Modular multilevel converter control with using a general space vector PWM method in medium voltage hydro power application
No full textThis paper studies a generalized space vector PWM (SVPWM) method for modulating the modular mul-tilevel converter (MMC) for a medium voltage hydropower application. In addition to the modulation of the MMC, the circulating current control and the submodule capacitor voltage balancing are included in the study. The simulation and experimental results show the feasibility of using the generalized SVPWM method for controlling the MMC. Furthermore, the loss study shows that the switching loss in the MMC can be reduced with 28% when a modification of the generalized SVPWM method is utilized, thus, the total efficiency of the converter can be increased
A Study on the Lifetime of Q2L-MMC-DAB’s Switches for Wind Turbine Applications
No full textThis paper studies the lifetime of semiconductor switches of a dual-active-bridge (DAB) DC-DC converter for wind turbine applications. Quasi-two-level operating modular multilevel converters (MMC) are used as the building blocks of the DAB converter. One of the established lifetime models is used for the lifetime estimation of the switches. Measurement data of an onshore wind turbine for three hundred days is used as the mission profile. It is shown that the short-term thermal cycles (cycles with frequency in the range of switching frequency) are detrimental to the lifetime estimation of the auxiliary switches of the MMCs’ submodules. Thus, neglecting the short-term thermal cycles will overestimate the lifetime of the auxiliary switches by several orders of magnitude. On the other hand, these cycles will not affect the lifetime of the bypass switches considerably. It is also shown that the thermal stress on the secondary-side auxiliary switches is more severe than the primary-side ones. It is suggested that two parallel devices should be used for the secondary-side auxiliary switches; as a consequence, a reasonable lifetime is achieved for the secondary-side auxiliary switches
Performance comparison of five-level NPC and ANPC converters in medium voltage drives for hydro power application
No full textThis paper compares the performance of a five-level neutral-point clamped (NPC) converter and a five-level active neutral-point clamped converter (ANPC) for a medium voltage and variable speed pumped-storage hydropower application. It is found that the ANPC converter has a lower current total harmonic distortion (THD) compared with the NPC converter under the same switching frequency, while the losses are higher. However, the simple structure and the easiness of controlling the DC-link voltage means that the five-level ANPC converter has a high potential in the market of the aforementioned application
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