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INCLUSION OF DEAD-TIME AND PARAMETER VARIATIONS IN VSC MODELLING FOR PREDICTING RESPONSES OF GRID VOLTAGE HARMONICS
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| Author(s) |
Jan Svensson |
| Abstract |
A discrete regulator-controlled VSC connected to the grid is analysed by discrete state equations and by the use of the average switch model method. The controller takes into account the dead-time, caused by the calculation time of the controller, as well as parameter variations. All transfer functions from one voltage component (d or q) to one current component (d or q) have the same gain characteristics. The gain of the grid voltages increases when the frequency increases. The gain has a maximum at approximately 20 % of the sample frequency and decreases rapidly at higher frequencies. The maximum gain is higher for the direct coupling of d and q-voltage to d- and q-current than for the cross coupling. The gain becomes higher when the estimated inductance is smaller than the correct inductance value. Both the d- and q-components of the voltage will fluctuate when the phase voltage harmonic components have the same amplitude in all three phases. The gain of the transfer function from the phase voltage to the grid current becomes higher than those of the d- and q- component transfer functions. The gain is still low at low frequencies resulting in a nearly sinusoidal current
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| Filesize: | 550.3 KB |
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| Type |
Members Only |
| Date |
Last modified 2016-03-09 by System |
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