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In this work an ac-dc-ac multilevel power converter is investigated. The developed configuration is composed of one single-phase ac-dc-ac three-leg module and two H-bridges, one of them connected in the shared part of the system to employ multilevel voltages to input and output converter, and the other one connected on the grid side for input overvoltage. The converter is employed in applications...
This paper proposes a single-phase ac-dc-ac converter composed of two three-leg converters connected in series with an H-bridge on its grid side. The proposed converter allows to feed the load voltage with sinusoidal voltages with constant amplitude and frequency and to operate with sinusoidal grid current with high power factor. Besides, the converter can be used to mitigate fundamental overvoltage...
In this paper, three control strategies for a wide band-gap bidirectional DC-DC converter (BDC) are introduced and combined to improve the vehicle traction system performance. A feed-forward control algorithm is proposed to reduce the voltage ripple of DC-link capacitor located between the BDC and traction inverter. Through voltage control of the BDC, both three-phase short and uncontrolled generator...
This study is to optimize the cell voltage and arm current in double-star modular multilevel converters (DSMMCs) based on Lagrange multiplier of energy cost function and arm current tracking control law. DSMMCs have been widely applied to high-voltage grid power injection, direct-current transmission, back-to-back power transfer, and energy storage systems. The size of capacitors and the rating of...
This paper presents a power-based droop controller for distributed energy resources converters in dc microgrids that are connected to the utility ac grid by a grid-interface converter. Typically, when dc microgrids are interfaced to ac power systems, the microgrid dc bus voltage can be affected by fluctuations caused, for example, by background harmonics present in the ac systems or by fluctuating...
This paper presents an ac ripple repression method for neutral-point voltage of three-level inverter system with electrolytic capacitor less. To reduce the volume of three-level inverter system, electrolytic capacitor with huge capacitance is must eliminated from dc-link. In the inverter system applying film capacitors, however, the ac ripple component in neutral-point voltage of dc-link is increased...
This paper presents a proportional harmonic power sharing (PHPS) control scheme to improve the voltage quality at point of common coupling (PCC) and share harmonic power simultaneously for an islanded microgrid. The proposed control strategy employs P+ multiple resonant controller, and P+ plus Q+-based improved droop control scheme to improve the voltage quality at the load bus. Additionally, the...
A novel control strategy which enables proportional linear and nonlinear loads sharing among paralleled inverters and voltage harmonic suppression is proposed in this paper. The proposed method is based on the autonomous currents sharing controller (ACSC) instead of conventional power droop control to provide fast transient response, decoupling control and large stability margin. The current components...
Direct power control (DPC) is an attractive control method for three-phase pulse-width modulation (PWM) rectifiers, due to the merits of simple structure, quick dynamic response and little tuning work. However, conventional switching table based DPC presents relatively high power ripples and current harmonics, which is especially serious when the grid voltages are unbalanced. Introducing space vector...
Harmonic power can be shared by controlling the equivalent harmonic impedance of distributed generation (DG) units in islanded microgrids. This paper firstly reviews several methods for controlling the equivalent harmonic impedance of DGs and adopts the method based on resistive active power filter (R-APF). Then, a droop relationship between the equivalent harmonic impedance of DGs and their remaining...
This paper presents the design of a digital controller for a 600 W Boundary-Conduction-Mode (BCM) interleaved boost converter used in an ac-dc Power-Factor-Correction (PFC) power supply. The output voltage of a typical boost PFC rectifier contains a 2nd harmonic ripple. Therefore to achieve good power factor, the output voltage compensator must have a low bandwidth, in order to sufficiently attenuate...
Diversifying the role of grid side converters (GSC) associated with distributed generation (DG) may have a technical and economic impact. The increasing number of residential photovoltaic rooftop systems can be exploited by distribution network (DN) operators in order to support and improve the power quality of the grid without considerable further investment. GSC can support the grid during abnormal...
The control of PWM rectifiers under unbalanced network has become an important issue in recent years, especially in the applications with weak grid. Conventional methods is based on voltage oriented control (VOC), which requires several PI controllers in dual reference frame and the sequence extraction of grid/rectifier voltages and currents. To reduce the control complexity, recently direct power...
Power quality of ac bus voltage is a key issue for microgrids. A model-predictive-control (MPC)-based distributed bus voltage compensation methods using inverter-interfaced distributed generators (DGs) connected to the concerned bus is proposed. The presented method can compensate bus voltage unbalance and harmonics and share the compensated current between inverters autonomously, with neither communication...
In the field of high-speed electrical drives, the use of SiC MOSFET inverters represents a viable solution since this kind of devices allows an improvement of the converter efficiency. Notwithstanding issues related to the high frequency operation of the SiC MOSFET's, like the failure of the motor winding insulation due to the increased electrical stress and hence a reduced system reliability, are...
This paper deals with a newly conceived control topology based on the Repetitive action in 4-leg VSI for stand-alone Ground Power Unit (GPU) applications. In such mode of operation, a dedicated controller has to regulate the inverter output voltages, which are measured at the output of the power filter. The proposed Repetitive Control can provide the required harmonic compensation capabilities that...
Voltage-sensorless control has been investigated for Voltage Source Inverters (VSIs) for many years due to the reduced system cost and potentially improved system reliability. The VSI based Resistive Active Power Filters (R-APFs) are now widely used to prevent the harmonic resonance in power distribution network, for which the voltage sensors are needed in order to obtain the current reference. In...
The grid inductance is a sensitive parameter to be considered in order not to degrade the control system performance and to guarantee the system stability. In this paper, the Grid Inductance estimation based on Generalized Integrators (GIGI) method is proposed. It carries out an online grid inductance detection, which disturbs the grid by injecting a time-limited and small-amplitude harmonic voltage...
This work investigates a linear model predictive control (MPC) in conjunction with a voltage source inverter with a grid-interfacing passive filter. In an ideal grid, standard linear MPC demonstrates fast transient and excellent steady-state performance while respecting the imposed constraints. Nevertheless, its direct application onto the grid-connected converters operating with a distorted grid...
This paper presents the Enhanced Series Bridge Converter (ESBC), a hybrid modular multilevel converter with H-bridge front end suitable for high power grid applications. It retains the advantages of other modular multilevel topologies while offering compact structure, making it attractive for offshore stations, back-back HVDC stations, and city centre infeeds. The structure, operating principles and...
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