87,767 research outputs found
Advanced power cycler with intelligent monitoring strategy of IGBT module under test
No full textPower cycling (PC) test is one of the important test methods to assess the reliability performance of power device modules related to packaging technology, in respect to temperature stress. In this paper, an advanced power cycler with a real-time VCE_ON and VF measurement circuit for the IGBT and diode, which for the wear-out condition monitoring are presented. This advanced power cycler allows to perform power cycling test cost-effectively under conditions close to real power converter applications. In addition, an intelligent monitoring strategy for the separation of package-related wear-out failure mechanisms has been proposed. By means of the proposed method, the wear-out failure mechanisms of an IGBT module can be separated without any additional efforts during the power cycling tests. The validity and effectiveness of the proposed monitoring strategy are also verified by experiments
Reactive power influence on the thermal cycling of multi-MW wind power inverter
Full text linkIn this paper the reactive power influence on the thermal cycling of power devices in grid-connected inverter for 10 MW wind turbines is investigated. Restrained by the grid codes, the allowable reactive power ranges in relation to amplitude and phase angle of the load current for a single converter system are first presented at different wind speeds. Furthermore, the interaction between paralleled converter systems in a wind park is also considered and analyzed. By controlling the reactive power circulated among paralleled converters, a new concept is then proposed to stabilize the thermal fluctuation of the power devices during wind gusts. It is concluded that the reactive power may change the thermal distribution of power devices. By properly controlling the reactive power, it is possible to achieve a more stable junction temperature in the power devices during the fluctuation of wind speed, and thereby could provide a new way to improve the reliability of the wind power conversion system
A survey of SiC power MOSFETs short-circuit robustness and failure mode analysis
Full text linkThe aim of this paper is to provide an extensive overview about the state-of-art commercially available SiC power MOSFET, focusing on their short-circuit ruggedness. A detailed literature investigation has been carried out, in order to collect and understand the latest research contribution within this topic and create a survey of the present scenario of SiC MOSFETs reliability evaluation and failure mode analysis, pointing out the evolution and improvements as well as the future challenges in this promising device technology
Genetic algorithm based design of the active damping for a LCL-filter three-phase active rectifier
No full textThe use of a LCL-filter mitigates the switching ripple injected in the grid by a three-phase active rectifier. However stability problems could arise in the current control loop. In order to overcome them a damping resistor can be inserted, at the price of a reduction of the efficiency. On the contrary the use of the active damping seems really attractive but it is often limited by the use of more sensors respect to the standard control and by the complex tuning procedure. This paper introduces a new active damping method that does not need the use of more sensors and that can be tuned using genetic algorithms. It consists of adding a filter on the reference voltage for the converter's modulator. The tuning process of this filter is easily done, for a wide range of sampling frequencies, with the use of genetic algorithms. This method is used only for the optimum choice of the parameters of the filter and an on-line implementation is not needed. Thus the resulting active damping solution does not need new sensors or complex calculations. Moreover, in the paper particular attention is devoted to the dynamics of the system due to the introduction of the active damping
Design and Control of an LCL-filter Based Three-phase Active Rectifier
No full textThe aim of the paper is to propose a design procedure for an LCL-filter in a front-end three-phase active rectifier. The main goal is to ensure a reduction of the switching frequency ripple at a reasonable cost and, at the same time, to obtain a high performance rectifier. In this paper a step-by-step procedure for designing an LCL-filter is proposed and verified by simulations and experiments. An example of LCL-filter design has been reported and, with the obtained values, the filter has been realised and tested. The experimental results demonstrate the effectiveness of the design procedure both of the LCL-filter and of the controllers. The performance of the overall system is good both in the low and high frequency ranges. Moreover the good agreement between these results and those obtained in simulation validate the adopted model: the design procedure and the simulation model represent a powerful tool to design an LCL active rectifier without the need for the realisation of several prototypes
Design and control of a three-phase active rectifier under non-ideal operating conditions
No full textIndustrial engineers face many non-ideal operating conditions in the design of the active rectifiers: too long computation time, presence of acquisition filters, ac phases unbalance, location of the grid voltage sensors after a dominant reactance and passive damping if an LCL-filter is used. The phenomena generated by these conditions are generally non-linear. Hence the first step is to find out how much each of them affects the system's overall performance. Then,new rules for the tuning of the controllers can be developed on the basis of the analysis of the transient behavior and of the steady state harmonic content of the dc voltage and of the ac current. This procedure is developed in this paper through simulations and laboratory tests
Single-phase quasi-Z-source inverters: Switching loss reduction using a quasi-sinusoidal modulation strategy
No full textImpedance source inverters are gaining higher attention due to their merits compared with the two-stage solution, and among their possible structures, the quasi-Z-source inverter (qZSI) is commonly used due to its simple structure and continuous input current. In this paper, the single-phase qZSI is considered and a quasi-sinusoidal modulation (qSM) strategy is proposed in order to enhance its performance. Unlike the conventional modulation strategies, the proposed qSM strategy has a simpler implementation due to the utilization of only two reference signals, reduced switching losses, and improved energy conversion efficiency as a consequence. The proposed qSM strategy is analyzed and compared with the conventional modulation strategies using PLECS models of a 1.5 kVA single-phase qZSI. Finally, experimental results are shown in order to validate the obtained simulation results, demonstrating higher efficiency under the proposed qSM strategy
Grid impedance detection via excitation of LCL-filter resonance
No full textInverters adopted in distributed power generation, active filter and UPS are often connected to the grid through an LCL-filter. The impedance of the LCL-filter has a typical frequency spectrum with a resonance peak. Hence the LCL-filter has to be damped in order to avoid instability. However the resonance of the LCL-filter can be also excited in a controlled way in order to individuate the resonance frequency in the spectrum (using for example the FFT). This paper proposes to use a controlled excitation to measure the grid impedance, since this one influences also the resonance frequency. This paper addresses some possible limits, some solutions and some implementation issues (e.g. how to obtain a controlled resonance in the filter without damaging the system) in order to use the resonant peak for grid impedance detection. The analysis is validated both by simulations and experimental results
An EMC evaluation of the use of unshielded motor cables in AC adjustable speed drive applications
No full textThe most common solution for modern adjustable speed drives (ASD) is the use of induction motors (IM) fed by voltage-source inverters (VSI). The inverter generates a pulsewidth modulated (PWM) voltage, with dv/dt values of about 6 kV/μs or even more. In three-leg inverters for three-phase applications the occurrence of common-mode voltage is inherent due to asymmetrical output pulses. As a result, for electromagnetic compatibility (EMC) reasons, in most applications shielded cables are used between the inverter and the motor, implying high installation costs. The present paper discusses the use of cheaper, unshielded cables. A new method for measuring electromagnetic interference (EMI) from unshielded cables is proposed and measurement results are presented. The level of EMI is evaluated in different situations: without an output filter, with a classical LC output filter and with an advanced output filter with DC link connection. It is concluded that, from an EMC point of view, unshielded cables can give very good performance provided that a common-mode (CM) output filter is used
An overview of three-phase voltage source active rectifiers interfacing the utility
No full textIn this paper an overview of the three-phase voltage source active rectifiers and their applications is given. The basic control methods like phase and current controls are described. Advanced control such as two-axis based, feedforward and active damping if an LCL-filter is used are also described. The use of emerging control technologies such as direct power control, fuzzy control and soft computing like genetic algorithm are investigated. Particular attention is also paid to industrial problems such as cost, reduction of the number of sensors, non-ideal conditions, such as grid unbalance, LCL-filter design and EMI-issues. Finally, some tests results are presented and discussed in order to provide the theoretical analysis with a solid experimental basis
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