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This paper presents the theoretical analysis on the errors in voltage synthesis and position estimation due to the voltage distortion in position-sensorless operation. Especially, the pulsating square wave signal injection method into the estimated d-axis would be focused on, revealing the nature that the position estimation performance depends on the frequency of the injected signal. From the analysis,...
In this paper, a method to detect islanding operation of distributed generator (DG) is proposed, which exploits frequency drift accelerated by grid unbalance component, namely negative sequence component of grid voltage. The negative sequence component could be added to the gain of frequency feedback loop in the conventional anti-islanding scheme. To keep the power factor regulation, the displacement...
For three-phase three-wire grid, a method to synchronize the converter to the grid voltage, which was distorted by low-order harmonics and unbalances, has been widely described. In addition to filtering them, the DC rejection can be achieved together with a frequency adaptive observer in order to eliminate DC bias in the voltage. The state equation for the observer is newly established, and the observer...
A grid synchronization technique is essential for grid-connected power converters. Phase-locked loop (PLL) has been widely exploited as an implementation technique, but additional efforts are required to deal with severely distorted grid voltages. In this paper, an observer is proposed to enhance the performance of PLL. A state equation is newly formulated to construct the observer, which extracts...
Accurate detection of the grid angle at the startup of a converter prevents the over-current trip and also reduces the commissioning time of the system. This paper presents a method to detect initial angle of the grid voltages by measuring the phase currents depending on conduction state of diodes. During the diode conduction, the source voltages are estimated and the estimated voltages are fed into...
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