| 1. |
- Alikhanzadehalamdari, Babak, 1993, et al.
(författare)
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Closed-Form ZVS Boundaries for Three-Phase M-level-to-N-level DAB Converters with Different Winding Configurations
- 2023
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Ingår i: IEEE Transactions on Power Electronics. - 0885-8993 .- 1941-0107. ; 38:7, s. 8528-8543
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Tidskriftsartikel (refereegranskat)abstract
- One of the essential characteristics of a three-phase dual-active-bridge (DAB) DC-DC converter is its inherent zero-voltage switching (ZVS) capability during the turn-on of the switches. This paper provides closed-form equations that identify the ZVS boundaries for an M-level-to-N-level DAB converter, where M and N can be any natural numbers. It is shown that the derived ZVS boundaries can be used for different converter topologies, including but not limited to: two-level full-bridge converter, three-level neutral-point-clamped converter, T-type converter, transition arm converter, modular multilevel converter, and controlled-transition-bridge converter. The effect of different winding configurations of the medium frequency transformer—YY, Y Δ , and ΔΔ —is also considered in the study. Additionally, easy-to-implement simplified ZVS boundaries are provided, and the effects of the different number of levels, transition times, and dead times on the ZVS operation are quantified. An important result shown is that the converters with the YY and the ΔΔ windings lose ZVS at partial loads as soon as the transition time increases from zero, whereas the ones with the Y Δ configuration retain ZVS at partial loads and DC ratios close to unity, without any advanced modulation techniques. The derived analytical models are validated with MATLAB simulations and experiments.
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| 2. |
- 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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| 3. |
- Asimakopoulos, Panagiotis, 1985, et al.
(författare)
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IGBT Power Stack Integrity Assessment Method for High-Power Magnet Supplies
- 2019
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Ingår i: IEEE Transactions on Power Electronics. - 0885-8993 .- 1941-0107. ; 34:11, s. 11228-11240
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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.
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| 4. |
- Asoodar, Mohsen, et al.
(författare)
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Accurate Condition Monitoring of Semiconductor Devices in Cascaded H-Bridge Modular Multilevel Converters
- 2023
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Ingår i: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 38:3, s. 3870-3884
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Tidskriftsartikel (refereegranskat)abstract
- This article presents an online condition monitoring (CM) scheme for semiconductors used in modular multilevel converters (MMCs) that comprise cascaded H-bridge submodules. The CM algorithm is based on detecting changes in the ON-state resistance of the semiconductors over time. The proposed method is shown to successfully perform a curve tracing of semiconductors in MMCs while the semiconductor junction remains at a temperature that is readily measurable and undergoes minute changes during the measurement process. The ON-state resistance value is estimated from the measured ON-state voltage drop of the semiconductors and the measured arm current. Measuring the ON-state resistance at known temperatures allows for separating temperature-dependent variations of the ON-state resistance from age-dependent variations of this parameter. Suitable methods for reducing the effect of noise on the curve-traced data are proposed, and a recursive least square estimator is used to extract the optimum ON-state resistance from the traced v(CE) - i
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| 5. |
- Asoodar, Mohsen, et al.
(författare)
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Online Health Monitoring of DC-Link Capacitors in Modular Multilevel Converters for FACTS and HVDC Applications
- 2021
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Ingår i: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 36:12, s. 13489-13503
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Tidskriftsartikel (refereegranskat)abstract
- This article presents an online health monitoring scheme for dc capacitors in modular multilevel converters (MMCs). The health monitoring algorithm is based on detecting changes in the dc capacitance value over time. The proposed algorithm only utilizes measurements that are typically available in flexible alternating current transmission systems and high-voltage direct current applications. Hence, in the proposed estimation method, no additional sensors are used. The estimation scheme considers the presence of noise in voltage and current measurements, and utilizes a recursive least square estimator in conjunction with a special low-pass filter to minimize the estimation errors. Simulation results of a hardware replica, as well as experimental results on a low-power MMC prototype show that the proposed scheme can identify the dc-link capacitance value with a maximum error of 1%.
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| 6. |
- Augustin, Tim, et al.
(författare)
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Experimental Study of Enhanced Active Resonant DC Circuit Breakers
- 2022
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Ingår i: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 37:5, s. 5687-5698
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Tidskriftsartikel (refereegranskat)abstract
- Enhanced active resonant (EAR) dc circuit breakers (DCCBs) are a novel type of DCCB that use a discharge closing switch as interruption medium. A technical limitation of discharge closing switches is the minimum voltage across the main gap required for successful triggering. A novel commutation process creating the minimum voltage internally is proposed, which allows to simplify the EAR DCCB configuration and to reduce its component count. In the prototype, the discharge closing switch is implemented with a TVG. Experiments show that the TVG can be triggered reliably down to a voltage of 50 V and that the discharge in the TVG is highly oscillatory at low current. The originally proposed EAR DCCB configuration has to be tuned such that the commutation to the TVG succeeds at low current. Conversely, the novel commutation process decouples the minimum voltage from the current level by adjusting the triggering delay. This allows reliable commutation irrespective of the operating conditions. It is shown that the novel commutation process does not adversely affect dc interruption. Proactive commutation operation and auto-reclosing strategies are demonstrated.
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| 7. |
- Bahmani, Amin, 1985, et al.
(författare)
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Accurate Evaluation of Leakage Inductance in High Frequency Transformers Using an Improved Frequency-Dependent Expression
- 2015
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Ingår i: IEEE Transactions on Power Electronics. - 0885-8993 .- 1941-0107. ; 30:10, s. 5738-5745
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Tidskriftsartikel (refereegranskat)abstract
- Moving towards higher power density in magnetic components, which is often realized by increasing the operating frequency, leads to the need for development of more accurate design tools, for example more accurate expressions for core losses, winding losses and leakage inductance calculations. This paper presents a new analytical expression intended to accurately evaluate the leakage inductance of transformers in the high frequency range in which the behavior of the magnetic field within the windings is altered. Unlike conventional expressions, which usually overestimate the leakage inductance at higher frequencies, this expression accounts for high frequency behavior of the magnetic field and provides high accuracy when operating at high frequencies. These high accuracy and applicability makes the derived expression of interest for designers to avoid time consuming finite element simulations without compromising with accuracy. The expression is validated by 2-D FEM simulation, as well as by measurements.
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| 8. |
- Bahmani, Amin, 1985, et al.
(författare)
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An Accurate Pseudoempirical Model of Winding Loss Calculation in HF Foil and Round Conductors in Switchmode Magnetics
- 2014
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Ingår i: IEEE Transactions on Power Electronics. - 0885-8993 .- 1941-0107. ; 29:8, s. 4231 - 4246
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Tidskriftsartikel (refereegranskat)abstract
- When operating higher up in frequency, the copper losses in transformer windings will significantly rise due to enhanced skin and proximity effect. This leads to a high need to develop new methods to accurately evaluate winding losses at higher frequencies. This paper investigates the effect of different geometrical parameters at a wide range of frequencies in order to propose a pseudoempirical formula for winding loss calculation in high-frequency transformers. A comprehensive analysis of the edge effect and ac resistance is done by performing more than 12 300 2-D finite element simulations on foil and round conductors. Unlike previous studies which mostly focused on specific case studies with limited applications, this model provides very high accuracy, especially where the most common analytical models drastically underestimate the winding losses, with a wide-range applicability which could be of interest for designers to avoid time consuming FEM simulation without compromising with the accuracy. Several transformers are built and the model is experimentally verified with a good agreement.
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| 9. |
- Bakar, Muhammad Abu, 1969-, et al.
(författare)
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Dual-mode stable performance Phase-Shifted Full-Bridge converter for wide-input and medium power applications
- 2021
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Ingår i: IEEE transactions on power electronics. - 0885-8993 .- 1941-0107. ; 36:6, s. 6375-6388
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Tidskriftsartikel (refereegranskat)abstract
- Power converters with an extended range of line voltage are the main requirement in today's industrial applications like photovoltaic and supercapacitors based energy systems. The variation in the line voltage severely degrades the performance of power converters, because of the extended freewheeling interval, more circulation current, narrow range of zero voltage switching and increased EMI. This work suggests a modified Phase-Shifted Full-Bridge converter that cuts the freewheeling interval and minimizes these problems. It extends the input voltage range by keeping the operational duty cycle of the converter high over the wide range of input voltage while maintaining the performance stable. The proposed converter consists of four low profile transformers having reconfigurable interconnection structure. There are two distinct reconfigurable modes, a series mode and a parallel mode, which can be configured with changes in the operational conditions. The operation of the proposed converter with high switching frequency improves power density. Additionally, the use of multiple transformers minimizes heat management efforts and reduces the overall volume of the converter. The proposed work is validated in hardware characterization for a wide range of input voltage 100-400Vdc and up to the load power of 1kW. The measured energy efficiency of the proposed converter remains stable over the complete range input voltage 100-400Vdc.
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| 10. |
- Bakas, Panagiotis, 1984-, et al.
(författare)
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A Review of Hybrid Topologies Combining Line-Commutated and Cascaded Full-Bridge Converters
- 2017
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Ingår i: IEEE transactions on power electronics. - : IEEE Press. - 0885-8993 .- 1941-0107. ; 32:10, s. 7435-7448
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Forskningsöversikt (refereegranskat)abstract
- This paper presents a review of concepts for enabling the operation of a line-commutated converter (LCC) at leading power angles. These concepts rely on voltage or current injection at the ac or dc sides of the LCC, which can be achieved in different ways. We focus on the voltage and current injection by full-bridge (FB) arms, which can be connected either at the ac or dc sides of the LCC and can generate voltages that approximate ideal sinusoids. Hybrid configurations of an LCC connected at the ac side in series or in parallel with FB arms are presented. Moreover, a hybrid configuration of an LCC connected in parallel at the ac side and in series at the dc side with an FB modular multilevel converter (MMC) is outlined. The main contribution of this paper is an analysis and comparison of the mentioned hybrid configurations in terms of the capability to independently control the active (P) and reactive power (Q).
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