The authors propose a novel method for the instantaneous digital
control of a PWM (pulse-width modulated) inverter used in an
uninterruptible power supply. The output voltage is compared to a
sinusoidal reference at each sampling instant to compute in real time
through a digital controller the pulse width of the same interval. The
closed-loop digital feedback eliminates the steady-state error of the
output voltage with a very short computation time. This strategy is
verified through computer simulations and provides a very fast
compensation of disturbances caused by nonlinear loads, such as
rectifiers and triac loads, with low total harmonic distortion and
"Single-phase islanded DG system. the robustness and the dynamic response of inverter , . However, in all the above cases, the control design leads to the output voltage waveform sensitive to the load variations. "
[Show abstract][Hide abstract] ABSTRACT: Maintaining good voltage regulation and achieving
fast dynamic response under sudden load fluctuation are extremely
important in distributed generation (DG) as well as
uninterrupted power supply (UPS) systems. This paper presents
a fixed frequency hysteresis controller, which is implemented on
the basis of sliding mode control (SMC) technique and fixed
frequency controlled logic with a hysteresis band. The controller
retains the benefit of hysteretic current control having fast
dynamic responses and mitigates the drawback of the variable
switching frequency. Here a ellipsoidal switching surface for the
inverter control is taken in phase plane, rather than the timeplot.
The control scheme leads to a robust behavior against
any load fluctuations. The designed switching surface allows a
faster tracking of the externally given sinusoidal reference. The
proposed method is then applied to 1-KVA, 110V, 50Hz islanded
1-� voltage source inverter (VSI) system. The results show that
the dynamic response is quite faster.
International Conference on Circuit, Power and Computing Technologies [ICCPCT]; 04/2014
"Várias formas de controle por tracking tem sido propostas na literatura para conversão CC-CA, dependendo de qual processamento é aplicado ao sinal de erro (Kawamura and Hoft, 1984; Maussion et al., 1989; Jezernik et al., 1989; Biel et al., 2003; Olm, 2003; Aracil et al., 2002; Leung et al., 2005). Em todos estes casos, o projeto de controle é baseado em um modelo de estágio de potência conduzindo a formas de onda de saída sensíveis às variações nos parâmetros deste estágio, tais como variações de carga. "
[Show abstract][Hide abstract] ABSTRACT: A new sliding-mode control scheme for the generation of au- tonomous oscillations in a single-phase inverter is presented. The proposed control scheme is based on an energy shap- ing approach and no external sinusoidal reference signal is required. Simulation and experimental results obtained con- sidering resistive and nonlinear loads are presented.
[Show abstract][Hide abstract] ABSTRACT: Abstract: This PhD research discusses digital control strategies for three-phase Pulse Width Modulated (PWM) voltage inverters used in Uninterruptible Power Supplies (UPS) for single unit and parallel unit systems. For the single inverter system, this research proposes a novel control strategy which utilizes the perfect Robust Servomechanism Problem (RSP) control theory to allow elimination of specified unwanted voltage harmonics from the output voltages under non-linear load conditions and to achieve fast recovery performance on load transient. This technique is combined with a discrete sliding mode current controller that provides fast current limiting capability needed for overload or short circuit conditions. For the parallel inverter system, a combination of two control methods is proposed: average power control method and droop control method. The average power method is used in order to overcome the sensitivity of load sharing to output voltage/current measurement errors and mismatch wiring impedances between units, while the droop method allows the control to still maintain proper load sharing in the event that inter-unit communication is lost. In addition to this, a harmonic droop scheme for sharing of harmonic content of the load currents is introduced based on the proposed single unit control. Control analysis, experimental and simulation studies, using two parallel three-phase PWM inverters, are presented to show the effectiveness of the proposed control strategies, both for single and parallel inverter systems. Title from first page of PDF file. Document formatted into pages; contains xviii, 224 p.; also includes graphics. Thesis (Ph. D.)--Ohio State University, 2004. Includes bibliographical references (p. 199-211). System requirements: World Wide Web browser and PDF viewer.
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