output filter
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Author(s):  
Salman Harasis ◽  
Saher Albatran ◽  
Eyad Almaita ◽  
Khaled Alzaareer ◽  
Qusay Salem ◽  
...  

<p>Controlling weak grid-connected systems is very challenging. In transient, frequency and voltage oscillations may lead to voltage and/or frequency stability problems and finally lead to system collapse. During steady-state operation and at the point of common coupling (PCC), voltage degradation and grid voltage background harmonics restrict the inverter's functionality, reduce the power flow capability and cause poor power quality. With weak grid connection, grid impedance variance will contaminate the voltage waveform by harmonics and augment the resonance, destabilizing the inverter operation. In this paper, complete mathematical modeling is carried out and state feedback-plus-integral control is implemented to support the stabilization of the system. The proposed controller is adopted to provide a smooth transient under sudden load change by controlling the injected grid current under different grid inductance values. Furthermore, the proposed control is used to reduce the order and size of the inverter output filter while maintaining system stability. The proposed control has been compared with the conventional proportional integral (PI) controller under different scenarios to validate its effectiveness and to strengthen its implementation as a simple controller for distributed generator applications.</p>


Author(s):  
Abderrahmane Ouchatti ◽  
Redouane Majdoul ◽  
Ahmed Moutabir ◽  
Abderrahim Taouni ◽  
Abdelouahed Touati

In this article, a three-phase multilevel neutral-point-clamped inverter with a modified t-type structure of switches is proposed. A pulse width modulation (PWM) scheme of the proposed inverter is also developed. The proposed topology of the multilevel inverter has the advantage of being simple, on the one hand since it does contain only semiconductors in reduced number (corresponding to the number of required voltage levels), and no other components such as switching or flying capacitors, and on the other hand, the control scheme is much simpler and more suitable for variable frequency and voltage control. The performances of this inverter are analyzed through simulations carried out in the MATLAB/Simulink environment on a three-phase inverter with 9 levels. In all simulations, the proposed topology is connected with R-load or RL-load without any output filter.


2021 ◽  
Author(s):  
Branislav Stevanovic ◽  
Santiago Cobreces ◽  
Emanuel Serban ◽  
Pedro Alou ◽  
Martin Ordonez ◽  
...  
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Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5057
Author(s):  
Cheng Luo ◽  
Xikui Ma ◽  
Lihui Yang ◽  
Yongming Li ◽  
Xiaoping Yang ◽  
...  

Under unbalanced grid voltage faults, the output power oscillation of a grid-connected inverter is an urgent problem to be solved. In the traditional topology of inverters, it is impossible to eliminate power oscillation and simultaneously maintain balanced output current waveform. In this paper, considering the solvability of reference current matrix equation, the inherent mechanism of inverter output power oscillation is analyzed, and a modified topology with auxiliary modules inserted in series between the inverter output filter and the point of common coupling (PCC) is proposed. Due to the extra controllable freedoms provided by auxiliary modules, the inverter could generate extra voltage to correct PCC voltage while keeping balance of output current, so as to eliminate the oscillation of output power. Simulation and experimental results verify the effectiveness of the proposed topology.


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