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The rapid development of power devices in recent years has led to a proposal of high-power isolated DC-DC converters using medium-frequency (MF) transformers. To realize such converters, it is important to miniaturize magnetic devices such as the transformer and inductor, because the volume of the magnetic devices is larger than that of other components. This paper proposes a procedure for reducing...
In this paper, reliability-oriented switching frequency analysis for Modular Multilevel Converter is investigated. In the medium voltage and high voltage direct current applications, the switching frequency should be low enough to avoid the converter from high switching power losses. In the other hand, choosing the switching frequency very low will impose higher ripple over the capacitor and will...
Thermal loading of wind power converters is critical to their reliability performance. Especially for IGBT modules applied in a converter, both of the mean value and variation of the junction temperature have significant impact on the lifetime. Besides other strategies to reduce the thermal loading of the IGBT modules, the power losses and thereby the thermal stresses can be controlled by varying...
Modular multilevel converters (MMC) are used in the applications such as medium voltage multi-megawatt drives and in HVDC power transmission. The converter has several sub-modules connected in series that are switched appropriately to regulate the pole voltage. Besides regulation of output voltage, it is also essential to regulate the individual sub-module capacitor voltages. In this paper, a novel...
In order to reduce the power loss of phase-shift full-bridge(PSFB) converter under light load and standby conditions, this paper proposes a simple control method to achieve zero-voltage switching (ZVS) at light load without any additional auxiliary components. The converter with the proposed control method operates in discontinuous conduction mode (DCM) by decreasing switching frequency and all the...
Static power converters have widespread applications, such as ground power units (GPU) for airplanes. A modified static ground power unit based on 5-level Active Natural Point Clamped (5L-ANPC) multilevel converter is proposed in this paper. A new LS-PSC-PWM switching method for the 5L-ANPC converter is defined in this paper. The provided THD value of proposed converter will be less than those the...
In computer and telecommunication power supplies, the front end DC-DC stage is required to operate with a wide input voltage range to provide hold up time when AC voltage fails. Conventional LLC converter serving as the DC-DC stage is not suitable for this task, as the normal operation efficiency at 400Vin will be penalized once the converter is designed to achieve high peak gain, i.e. the wide input...
In a hybrid cascaded multilevel converter subject to different DC-link voltage levels among cascaded cells, should conventional carrier phase-shifting pulse-width modulation be applied, it will fail to multiply the equivalent switching frequency of the overall output voltage. As a consequence, this makes it more difficult to design the output filter and limits the overall output bandwidth. Based on...
This paper investigates various random PWM (RPWM) techniques for conventional two-level inverter-fed traction drives and proposes a discrete RPWM technique for acoustic noise reduction. The proposed RPWM technique randomizes within a set of predefined switching frequencies compared with the continuous nature of randomization in conventional RPWM techniques. The proposed method was compared with conventional...
This paper proposes a dual-loop voltage control for optocoupler feedback in capacitive output filter converter to mitigate the detrimental effect of the optocoupler on regulation performance. The dual-loop consists of primary-side regulation (PSR) loop and reference voltage correction loop. PSR loop performs output voltage regulation with indirectly sensed output voltage across tertiary winding of...
This paper deals with the performance assessment of different permanent magnet motor drives topologies for Starter/Generator in More Electric Aircraft systems. The comparison is focused on the power electronics part of the system, assuming the possibility to adapt the machine structure to better fit the specific configuration. Simulations performed with Matlab/Simulink and Plexim Plecs will be used...
This paper presents the predictive control of the H-NPC converter for single-phase grid-connected photovoltaic (PV) applications. This topology has been commercialized by one major manufacturer for small-scale rooftop PV applications, up to 8 kW, with classic PI control and an adapted carrier based PWM modulation. The proposed control scheme allows the dc-Link voltage control and the balance of the...
Soft magnetic composite (SMC) is considered as an alternative solution for core materials of inductors used in LCL filters in power converter applications. Performance of SMC inductors in damping a range of harmonics caused by voltage switching is an interesting topic. The method used in this paper is to test the inductors together with a 70 kW PWM inverter to examine the filtering effects for different...
Electric vehicles rely on efficient charging techniques to maximize battery performance, efficiency and lifetime. Most EV on-board chargers are supplied from single phase AC mains, and contain 2nd order mains frequency harmonic in the battery current. This harmonic current incurs extra loss in the battery, increases battery temperature, and hence reduces charging efficiency and battery lifetime. Conventional...
The capacitor voltage drift problem in Modular Multilevel Converter (MMC) system has been widely discussed in the past. It is well known that sometimes the capacitor voltages are balanced, without any active controls. However, due to the uncertainty and lack of theoretical explanations, active capacitor voltage controls are typically preferred for real applications, and the voltage balancing/drift...
In hard switching boost-type or buck-type three-phase power factor corrected rectifier systems the turn-on losses in continuous conduction mode (CCM) are usually higher than the turn-off losses. This is mainly caused by the reverse recovery effect of the freewheeling diode. The reverse recovery related turn-on losses however may be eliminated if the converter is operated in boundary conduction mode...
Low-voltage DC (LVDC) systems offer a promising means for improving distribution system efficiency and reliability. The DC-AC conversion stage, however, is one of the main challenges for LVDC networks. A low-voltage modular multilevel converter (MMC) for LVDC distribution systems is proposed in this paper. Analysis is presented to show that its efficiency can exceed that of a conventional 2-level...
In this paper, the design principles, procedures and considerations for a 3 kW high efficiency LLC resonant DC/DC transformer is presented. The efficiency-oriented design procedure involves analytical methods for calculating converter RMS current on both primary side and secondary side, transformer winding AC loss and MOSFET switching loss. These methods are reviewed in this paper. The resonant inductor...
For low output voltage application, a half-bridge LLC resonant converter family with synchronous rectifier (SR) that has a boost pulse width modulation (PWM) converter characteristic for hold-up state operation is proposed in this paper. In proposed converters, an auxiliary switch (or an auxiliary switch and a diode) is added at the primary side to provide the charging branch for series resonant inductor...
In this paper a new active output filter” (AOF) for variable speed constant frequency power system in aerospace applications is proposed. The proposed AOF is envisioned as a power semiconductor filter block. In the proposed system the passive L-C output filter components are replaced by an H-bridge. The H-bridge is operated at high frequency to inject voltage harmonics to achieve a sinusoidal output...
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