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In this paper is presented the structure and working principle of the cascaded H-bridge multilevel converter with PWM rectifier and phase-shift transformer. Using the leak inductance as the filter reactor of the PWM rectifier can reducing the volume and cost of the converter; the phase-shift secondary side of the transformer can eliminate the current harmonics caused by the single power unit, restraining...
In this paper, two control strategies for three-phase series-parallel uninterruptible power supplies are compared. A series-parallel UPS consists of a parallel and a series converter. In this topology, most power required by load is supplied directly from AC line during standby mode. Therefore the overall efficiency is higher than that of a conventional UPS. Traditionally, the control strategy of...
The control for a diode-clamped three-level half bridge converter is researched in this paper. The reasons for the input current distortion around the zero-crossing point of the input voltage based on the voltage zero-crossing detection control are analyzed in detail, and a hybrid control which combines the reference voltage feed-forward control with the feedback control is proposed to prevent the...
A high performance modular three-phase utility-interactive converter is designed and implemented in this paper. This converter has three operation modes: grid-connection inverter mode, stand-alone inverter mode and rectifier mode. Control principles and modes of every mode are analyzed in detail and the modular design method is adopted. A simple but valid control strategy is proposed. Finally a 10...
This paper describes the optimal control of variable-speed permanent magnet synchronous generators system. In order to maximize generated power, permanent synchronous generator is controlled by a maximum power point tracking (MPPT) control and maximum efficiency control. A sensor-less scheme is proposed for MPPT. Experimental results have been carried out to verify the benefits of the proposed system.
The current source back-to-back converters have been largely neglected because of the slow transient response and low power factor, which is mainly resulted from a fixed PWM pattern and a poor control method. However, current source converters have intrinsic advantages such as the high reliability and the inherent current limiting capability. Due to these advantages, more and more people have been...
One position controlling source using sinusoidal wave by CPLD through linear amplifier technique for driving ring-type traveling-wave ultrasonic motor with 30 mm diameter of the stator (RTWUSM30) has been proposed and designed in this paper. The driving and controlling signals can be adjusted the frequency, the phase, the amplitude, and the phase difference of the two sin wave exciting signals through...
Permanent magnet synchronous generation (PMSG) has been more and more used in the wind power generation system due to its advantage of simpler structure, higher generation efficiency and more reliable operation. However, the behavior of wind power system during grid disturbances becomes more important with an increasing amount of wind energy installed. Nowadays the grid code demands that the wind...
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