Simulation of infinite power supply system and three-phase short circuit of synchronous generator based on Simuink

1 Three-phase short circuit in infinite power supply system

First, the system diagram of the infinite power supply system is given, as shown in the figure below. A three-phase short circuit occurs at 0.02s, and the corresponding line parameters are shown in Figure 2. The amplitude of the short-circuit current periodic component and the magnitude of the impact current are obtained by Simulink simulation.

Figure 1 Infinite power supply system diagram

Figure 2 Line parameters

Then, we perform theoretical calculations in order to compare with the simulation results. The process of theoretical calculations is as follows:

First, define the benchmark value: SB=100MVA, UB=110kV (take the high voltage side).

Then calculate the per-unit reactance of each component:

XL=0.450*SB/UB2；

XT=(Uk%/100)(SB/SN)；

X*∑= XL+ XT；

Then calculate the per-unit value and actual amplitude of the effective value of the short-circuit period component

Iw=1/ X∑；

Iw= IwIB= I*w *sqrt(2)*100/(sqrt(3)*11)=13.70kA；

Finally, the impulse coefficient Kimp=1.8, then the impulse current is:

Iimp=Kimp*Iw=1.8*13.7=24.66kA。

Next, we will briefly introduce the simulation model. The complete simulation model is shown in the figure below.

The parameters of the transformer are shown in the figure below.

Set the three-phase short-circuit trigger time to 0.02s, as shown in the figure below

Short-circuit current and other parameters are measured using VI measurement, and the corresponding parameters are shown in the figure below.

The simulation results are shown in the figure below

It can be seen from the simulation results that the impact current is between 20kA and 25kA, and the three-phase short-circuit current amplitude is around 15kA, which is basically the same as the results of theoretical calculations.

2 Transient simulation of three-phase short circuit of synchronous generator

First, the complete model diagram of Simulink simulation is given, as shown below.

The synchronous generator uses a synchronous motor module, and the corresponding module settings are shown in the figure below.

The parameter settings of the step-up transformer are shown in the figure below.

When it is set to 0.08s, a three-phase short circuit occurs, as shown in the figure below.

The three-phase stator current in the final simulation results is shown in the figure below.