Dynamic voltage restorer (DVR) is used to mitigate the impact of the voltage sags. At first the structure of DVR and three basic compensation methods are introduced. Considering the compensation performance and the injection capability of the DVR, a generalized compensation strategy based on pre-fault compensation, energy-saving compensation and progressive phase rotation method is proposed. With this compensation strategy, the active power injected by DVR can be minimized on the premise of the quality of compensation. Simulation results demonstrate the efficacy of the proposed compensation strategy.
Cotton and sulfuric acid that concentration is 98% as the raw material, to compare the resulting solid carbon sulfonic acid content of the material under different reaction temperatures. FTIR analysis shows that the cotton carbon is an amorphous carbon after sulfonation reactions, a sulfonic acid group present in the resulting material. When the sulfonation temperature is 170 °C, the prepared cotton carbon sulfonic acid has the highest acid content. By the sulfuric acid TG/DTG curve analysis, it verify: 170 °C is the highest activity temperature point of sulfuric acid sulfonation reaction.
This study presents a novel bidirectional dc-dc buck-boost converter compatible with the flywheel energy storage system (FESS) and a robust control for bidirectional power flow, according to the single cycle average current control scheme and proportional-integral (PI) control theory. The proposed converter and its control are designed to adjust voltage to achieve current limiting start up and final speed keeping of the motor in charge mode and maintain a constant output voltage in the case that terminal voltage of the motor in the FESS drops continually in discharge mode. Simulation results demonstrate high performance of the converter in both steady-state and dynamic operations.
The permanent magnet synchronous motor (PMSM), a nonlinear dynamic system, can exhibit prominent chaotic characteristics under some choices of system parameters and external inputs. Based on a mathematical model of the permanent magnet synchronous motor, the existence of chaotic attractor is verified by the phase trajectory, Lyapunov exponent map and the bifurcation diagram. Chaotic phenomenon, such as a strong oscillation of speed and torque, unstable operating performance, affects the normal operation of motor. It makes the PMSM in a stable state to control chaos of the PMSM with a control strategy of infinitesimal geometry, which can eliminate chaos well.
Voltage sag is one of the most frequent and serious dynamic problems that impact the power quality. To solve this problem, fast and precise detection of the voltage sag is needed. A detection method is presented in this paper, using single phase voltage information, to be applied in the typical condition of unsymmetrical three-phase voltage sag. This method adopts fast recognition of voltage disturbance and SPLL. Finally, MATLAB simulation has been used to verify the effectiveness of the method.
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