1,721,523 research outputs found
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
Grid impedance estimation via excitation of LCL-filter resonance
No full textInverters adopted in distributed power generation, active filter, and uninterruptible power supply are often connected to the grid through an inductance-capacitor-inductance (LCL) filter. The impedance of the LCL filter has a typical frequency characteristic 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 fast Fourier transform). This paper proposes to use a controlled excitation in measuring the grid impedance, since this one influences also the resonance frequency. This paper will address 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
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
Proportional-resonant controllers and filters for grid-connected voltage-source converters
No full textThe recently introduced proportional-resonant (PR) controllers and filters, and their suitability for current/voltage control of grid-connected converters, are described. Using the PR controllers, the converter reference tracking performance can be enhanced and previously known shortcomings associated with conventional PI controllers can be alleviated. These shortcomings include steady-state errors in single-phase systems and the need for synchronous d-q transformation in three-phase systems. Based on similar control theory, PR filters can also be used for generating the harmonic command reference precisely in an active power filter, especially for single-phase systems, where d-q transformation theory is not directly applicable. Another advantage associated with the PR controllers and filters is the possibility of implementing selective harmonic compensation without requiring excessive computational resources. Given these advantages and the belief that PR control will find wide-ranging applications in grid-interfaced converters, PR control theory is revised in detail with a number of practical cases that have been implemented previously, described clearly to give a comprehensive reference on PR control and filtering
Reactive Power Control for Improving Wind Turbine System Behavior Under Grid Faults
No full textThis letter aims to present a generalized vector-based formulation for calculating the grid-side current reference to control reactive power delivered to the grid. Strategies for current reference generation were implemented on the abc stationary reference frame, and their effectiveness was demonstrated experimentally, perhaps validating the theoretical analysis even under grid fault conditions
Sensitivity analysis of an LCL-filter-based three-phase active rectifier via a "virtual circuit" approach
No full textThree-phase active rectifiers based on the voltage source converter topology can successfully replace traditional thyristor-based rectifiers or diode bridge plus chopper in interfacing dc-systems to the grid. However, if the application in which they are employed has a high safety issue or if there are other loads connected to the same Point of Common Coupling (PCC), and sensitive to the harmonics produced by the switching of the converter, an LCL-filter has to be used. This kind of solution has been studied in theory but its sensitivity to the value of the LCL-filter passive elements employed, to the grid side stiffness and to the parameters of the controller has never been considered in detail. In. this paper the experimental results of an LCL-filter-based three-phase active rectifier are analyzed with the circuit theory approach. A "virtual circuit" is synthesized in role of the digital controller and of the feedback filters to have an homogenous model that allows a sensitivity analysis which is rigorous and straightforward for the industry
A quasi-Z-source-based inductive power transfer system for constant current/constant voltage charging applications
Full text linkThis article proposes a quasi-Z-source (qZS)-based Inductive Power Transfer (IPT) system for Electric Vehicles (EVs) charging applications. The IPT systems use the magnetic field to transfer power between two coils wirelessly, achieving improved reliability, safety and less environmental impact. Compared to the conventional IPT system, the proposed qZS-IPT system simultaneously achieves DC/DC regulation and DC/AC conversion through a single-stage conversion, thus lowering the cost and complexity of the system. Moreover, the reliability of the system is improved thanks to the qZS network shoot-though immunity and the reduced number of switches. To ensure the battery efficient charging and long service life, the constant current/constant voltage (CC/CV) method is considered. With the proposed innovative modulation scheme, the qZS can easily change between buck and boost modes, respectively, lowering or increasing the secondary side current. A theoretical analysis is presented for system design. Simulation results based on a 25 kW (200 V/135 A) low duty EV charger are presented to verify the effectiveness of the proposed scheme. Experimental tests are performed on a 150 W scale-down prototype to validate the analysis and demonstrate the effectiveness of the proposed qZS-IPT system for CC/CV chargers
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
Multiple Harmonics Control for Three-Phase Grid Converter Systems With the Use of PI-RES Current Controller in a Rotating Frame
No full textUdgivelsesdato: MA
Model predictive control of grid forming converters with enhanced power quality
Full text linkThis paper proposes an enhanced finite control set model predictive control (FCS-MPC) strategy for voltage source converter (VSC) with a LC output filter. The proposed control scheme is based on tracking the voltage reference trajectory by using only a single-step prediction within the controller horizon. Besides, the suitability of different frequency control schemes with the proposed scheme to prevent from inherent variable switching behaviour of conventional FCS-MPC is investigated. Based on that, the proposed method targets two major factors influencing power quality in grid forming applications by enhancing the output voltage harmonic distortion and also preventing variable switching behaviour of FCS-MPC. Although compared to multi-step prediction approaches, only a single-step multi-objective cost function to improve computation efficiency is utilized, the introduced control schemes are able to deliver higher power quality compared to its counterpart methods as well. Furthermore, the effect of different applied cost functions on the transient response of the system is studied and investigated for the future use of the VSC in microgrids (MGs). The effectiveness of the proposed scheme was assessed by simulation using MATLAB/SIMULINK and experiment using a 5.5 kVA VSC module and the results were in good agreement
- …
