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Master of Science Thesis in Electric Power Engineering - page 69 / 114

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VOLTAGE ORIENTED CONTROL – SIMULATION

SIMULATION3 – INFLUENCE OF THE GRID IMPEDANCE The simulation3 have been done to show the influence of the grid impedance on the system.

We multiplied by 10 both

and .

GRID MODIFICATION (), grid resistance (H), grid inductance

VALUE 1e 2 1e 4

Table 3.8 : Simulation3 – New grid impedance parameters

As we explain in section “3.8 Grid modeling”, if

is too big compare to the total inductance value

, the voltage

will be highly dependent on the current and will vary. The Figure 3.52a. shows

the effect of the grid impedance, the voltage is distorted. Despite that, the system is still working well even if this voltage is used by the PLL to calculate the voltage angle. Figure 3.52b. shows the

voltage angle under simulation3 condition, there is no visible distortion.

a. b. Figure 3.52 : Simulation3 with new grid parameters

  • a.

    voltage

  • b.

    Voltage angle Theta

SIMULATION4 – TEST WITH ACTIVE DAMPING GA

PARAMETER MODIFICATION

VALUE

, voltage controller

0.0028

active conductance

0.0028

, voltage controller

3.5457

The results of simulation4 is plotted in APPENDIX F, Figure 0.28. The simulation parameters are the same as simulation1 with the following modification on controller parameter. We also re write the equation to find them (equation XXX section “3.5.3 Voltage saturation, antiwindup, active damping”).

Table 3.9 : Simulation4

We can see on Figure 0.28 that the controller doesn’t work properly anymore, some oscillation appear on DC link voltage and the current is completely distorted.

We observed that the simulation becomes stable again by reducing the controller parameters values. The Figure 0.29 shows a simulation with the following modified parameters :

60

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