| 1. |
- Asimakopoulos, Panagiotis, 1985, et al.
(författare)
-
Current Sharing inside a High Power IGBT Module at the Negative Temperature Coefficient Operating Region
- 2016
-
Ingår i: 18th European Conference on Power Electronics and Applications, EPE 2016 ECCE Europe, Karlsruhe, Germany, 5-9 September 2016. - 2325-0313. - 9789075815245
-
Konferensbidrag (refereegranskat)abstract
- This work investigates the current sharing effect of a high power Soft Punch Through IGBT module in the Negative Temperature Coefficient region. The unbalanced current sharing between two of the substrates is demonstrated for different current and temperature levels and its impact on the thermal stressing of the device is evaluated. The results indicate that the current asymmetry does not lead to a significant thermal stressing unbalance between the substrates.
|
|
| 2. |
- Asimakopoulos, Panagiotis, 1985, et al.
(författare)
-
Design of a Modular Multilevel Converter as an Active Front-End for a magnet supply application
- 2014
-
Ingår i: 2014 16th European Conference on Power Electronics and Applications (EPE'14-ECCE Europe), Lappeenranta, Finland, 26-28 August 2014. - 2325-0313. - 9781479930159
-
Konferensbidrag (refereegranskat)abstract
- The aim of this work is to describe the general design procedure of a Modular Multilevel Converter (MMC) applied as an Active Front-End (AFE) for a magnet supply for beam accelerators. The dimensioning criteria for the converter and the dc-link capacitance are presented and the grid transformer requirements are set. Considering the converter design, the arm inductance calculation is based on the specifications for the arm-current ripple and the DC-link fault tolerance, but, also, on the limitation of the second harmonic and the second-order LC resonance of the arm current. The module capacitance value is evaluated by focusing on the required switching dynamics and the capacitor-voltage ripple according to a newly proposed graphical method. The loading of each semiconductor in the half bridge is calculated via simulation, indicating the unsymmetrical current distribution. It is concluded that the current distribution for each semiconductor depends on the mode of operation of the converter. The different criteria for the choice of the number of modules per arm are discussed. Finally, the complete system, including a model for the load and the converter control strategy applied to the converter is simulated and obtained results are presented.
|
|
| 3. |
- Asimakopoulos, Panagiotis, 1985, et al.
(författare)
-
Heat sink design considerations in medium power electronic applications with long power cycles
- 2015
-
Ingår i: 17th European Conference on Power Electronics and Applications, EPE-ECCE Europe 2015, Geneva, Switzerland, 8-10 September. - 9789075815221
-
Konferensbidrag (refereegranskat)abstract
- The aim of this work is to investigate the impact of the heat sink thickness and material, as well as, of the convection coefficient of the water cooling system on the power-electronics module thermal stressing. The heat extraction capability of different thicknesses is tested. It is concluded that the thickest heat sink results in marginally lower temperature variation at the junction level compared to the second thickest one. In the thickest heat sink case, the linear dependence of the thermal resistance on the thickness counteracts the benefit of the increased thermal capacitance. The increase in the cooling medium flow rate, which corresponds to an increase in the convection coefficient between the heat sink bottom surface and the water, can be avoided by increasing the thickness of the heat sink. In this way, the energy consumption of the cooling system is reduced. The increase in the flow rate drastically reduces the thermal stressing in the thinnest heat sink case. The increase of the heat sink thickness can be beneficial for long power cycles. Copper and aluminum are the two materials that are compared, with the copper heat sink exhibiting a slightly increased performance. The study is conducted for a medium power DC-DC converter of a magnet supply with focus on long power cycles.
|
|
| 4. |
- Asimakopoulos, Panagiotis, 1985, et al.
(författare)
-
IGBT Power Stack Integrity Assessment Method for High-Power Magnet Supplies
- 2019
-
Ingår i: IEEE Transactions on Power Electronics. - 0885-8993 .- 1941-0107. ; 34:11, s. 11228-11240
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a method for assessing the integrity of a series of insulated-gate bipolar transistor (IGBT) power stacks during factory-acceptance tests and service stops. The key challenge that is addressed in this paper is detecting common assembly issues that affect the power stack thermal path as well as distinguishing the acute aging effects of bond-wire lift-off and solder delamination. The method combines offline Vce measurements with current in the extended Zero Temperature Coefficient (ZTC) operating region as well as with sensing current without modifications to the power stack. It also employs on-the-stack Vce calibration for both the measurements. Additionally, only a fixed duty cycle pattern is needed to control the switches. The paper also presents a sensitivity analysis of the method to various parameters such as the current level in the extended ZTC operating region, the precision of the Vce measurement, as well as the ambient, the cooling-water, and the junction temperatures. The experimental results are obtained from a high-current IGBT power stack used in a magnet power supply for particle accelerators and are compared favorably to results from finite element method and lumped parameter network simulations confirming the applicability of the method.
|
|
| 5. |
- Asimakopoulos, Panagiotis, 1985, et al.
(författare)
-
Thermal stressing mitigation possibility intended for a DC-current magnet supply based on high power IGBT modules
- 2017
-
Ingår i: 2017 19th European Conference on Power Electronics and Applications. - 2325-0313. - 9789075815276 ; 2017-January
-
Konferensbidrag (refereegranskat)abstract
- This work investigates the possibility to reduce the thermal stressing of high power IGBT modules in a DC-current application. Using four load current profiles as examples, two mitigation strategies are presented and their benefit to the power stack in terms of lifetime prolongation is evaluated. In the final part of the work, the investigation focuses on the relation between the shape of the load current and the potential for thermal stressing limitation that the proposed mitigation strategies can provide.
|
|
| 6. |
- Bakas, Panagiotis, et al.
(författare)
-
Solar PV array-inverter matching considering impact of environmental conditions
- 2011
-
Ingår i: Conference Record of the IEEE Photovoltaic Specialists Conference. - 9781424499656 ; , s. 001779-001784
-
Konferensbidrag (refereegranskat)abstract
- Sizing of photovoltaic (PV) generators is an important issue which might affect the PV system overall yield and performance ratio. The procedure is realized according to inverter specifications with the most important one being the operating voltage range. The parameter that is affected by this specification is the number of PV modules per string and a software tool was developed in order to study the effects of this parameter on the system performance. Moreover, the PV generator voltage is highly affected by the ambient temperature of a specific location. Thus, the optimum number of PV modules per string will differ in locations with different environmental conditions. The importance of PV string sizing is high, since improper string length can lead to significant deficiencies on the overall inverter performance. A study of the effects of PV string size on annual system energy production and yield has been conducted for several locations in Europe with significantly different weather as well as for locations with extreme climatic conditions such as high altitude and desert areas.
|
|
| 7. |
- Behrouzian, Ehsan, 1985, et al.
(författare)
-
A hybrid photovoltaic and battery energy storage system for high power grid-connected applications
- 2013
-
Ingår i: 15th European Conference on Power Electronics and Applications (EPE). - 9781479901166 ; , s. Art. no. 6631920-
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a hybrid PV-battery grid connected system suitable for high power PV powerapplications. High power PV systems have impressive voltage fluctuation with regards to theirmaximum power point voltage. Using DC/DC converters to regulate this voltage is inefficient in highpower systems as it adds an extra power conversion stage. On the other hand switching frequency,voltage stress as inverter limitations and power quality issues should be considered in high powerapplications. Central PV structures because of low efficiency and high cost inverters are not suitablefor high power systems. Maximum power extraction from PV together with active and reactiveinjected power control is another challenge in high power system. Z-source multilevel inverter for PVarrays together with battery energy storage systems is a suitable solution for high power application.This paper proposes a control strategy for this hybrid system. A simulation with PSCAD has beendone to validate the control strategy. Simulation results show how proposed control and topologysatisfies high power requirements for PV grid connected systems.
|
|
| 8. |
- Papastergiou, K.D., et al.
(författare)
-
Photovoltaic string configuration for optimal inverter performance
- 2011
-
Ingår i: 8th International Conference on Power Electronics - ECCE Asia. - : IEEE. - 9781612849560 ; , s. 1632-1636
-
Konferensbidrag (refereegranskat)abstract
- In the recent years photovoltaic installations have been growing rapidly both in numbers and in size. The main reason for this growth has been the generous subsidies offered by policy makers. As financial incentives are now being gradually removed, PV plant manufacturers are in quest for more efficient plant configurations that eventually reduce the investment cost and increase the annual energy yield. This paper presents a methodology for optimally sizing the PV panel strings (series-parallel connection of PV generators) for any specific inverter equipment and for a given location weather dataset. The methodology is based on some new PV plant performance metrics presented here. Finally, the concept of maximum power point of the inverter (MPPTi) is introduced.
|
|
