CHAPTER 4

Results and

discussion

1.1.

Simulation Results

Based on the proposed model of UPQC, the system is presented at

normal operating condition and faulted operating condition scenarios without

and with UPQC with comparison.

1.1.1.

Simulation results in normal operating

conditions

Simulation results

Without Using UPQC

As the model presented in Figure 3.10 with the test parameters

which is connected to a non-linear load has the following detail result

summaries. It is analyzed with different operating conditions. Load voltage and

load current waveforms with Fast Fourier Transform (FFT) analysis with time

domain and frequency domains to determine the difference in percentage of Total

Harmonic Distortion (THD).

In Figure 4.1 the load voltage waveform tells that until 0.3

seconds the load is at starting condition and after 0.3 second it works in its

normal operating condition. It is observed that the harmonic level of load

voltage with a THD of 11.17% and its magnitude is 0.9794p.u.

Figure 4.1: Load Voltage Waveform without UPQC

In Figure 4.2 the load current waveform shows that the magnitude

is somehow very low due to the nature of the load which causes a great

fluctuation and after 0.3 second it seems retaining steady state condition with

a harmonic level of THD 26.43% and magnitude is about 12.72p.u.

Figure 4.2. Load Current

Waveform without UPQC

Simulation results

Using UPQC

When

UPQC is inserted to the network it is clear that it can compensate both the

voltage and current related power quality issues and it can be seen that the

voltage harmonics level is reduced to 2.11% from 11.17%, which is a permissible

value according to the limit imposed by IEEE 519-1995 as shown in Figure 4.3.

Figure 4.3. Load Voltage

Waveform using UPQC

In Figure 4.4 with the insertion of UPQC to the network at normal

operating condition the load side harmonics is well compensated from a THD of

26.43% to 2.92% which is less than 5%.

Figure 4.4. Load Current

Waveform using UPQC

The value of total harmonic distortion in both cases signifies the

use of UPQC in distribution system.

1.2.Simulation

results in faulted operating conditions

4.2.1

Simulation results Without Using UPQC

At this scenario a single line to ground fault is applied in the

network near the load. The applied fault duration is is specified between

0.1-0.3 seconds. It is clear that during the fault the voltage level should be

reduced greatly and the current level is increased considerably.

After the fault is cleared the voltage and current waveforms will

retain is steady state condition.

In Figure 4.5, it is showed that for a single line to ground fault

voltage for a faulted line is approximately zero and the effect is also

propagated in the other two lines in a reduction of magnitude for the applied

fault duration.

Conversely, it also presents exaggerated current level for a

faulted phase and approximate current level to zero for the other two phases

for the applied/ chosen transition time / fault duration and after the fault is

cleared the system reaches its steady state condition.

For the above condition FFT analysis is also presented in the time

domain and frequency domain to determine the harmonic level with THD for the

fault duration and steady state condition.

Figure 4.5. Voltage &

Current level during Transition time

In Figure 4.6 the load voltage without UPQC is seen as FFT form

and it is observed that for 0.1-0.3 second the voltage level is zero and after

the fault is cleared the level is about 0.979p.u, and Figure 11b shows a

frequency domain FFT chart with a THD of .11%.

In Figures 4.7 the load current without UPQC is presented with

time domain and frequency domain FFT analysis and it is seen that for 0.1-0.3

seconds the current is increased greatly because of the fault and after the

fault is cleared it retains its steady state condition. The frequency domain

FFT analysis shows that the harmonics level of the load current is about a THD

of 0.01% , which is very minimum and uniform because of the fault.

Figure 4.6. Load Voltage

Waveform without UPQC

Figure 4.7. Load Current

Waveform without UPQC

Simulation results

Using UPQC

Figure 4.8 shows load voltage with UPQC in the network at fault condition of single line to ground

fault and it is observed that the voltage level is zero for the fault condition

of 0.1-0.3 seconds and the magnitude is about 0.979p.u after fault clearance in

the time domain analysis.

The frequency domain FFT analysis waveform shows the level of

voltage harmonics with THD of about 1.98% at 50Hz fundamental power frequency

and it is permissible by a standard limit imposed by the IEEE 519-1995.

Figure 4.9 shows the time domain FFT analysis shows a great

current level during fault duration time. The frequency domain current

harmonics level is about 1.7% which is maintained at a permissible limit.

Figure 4.8. Load Voltage

Waveform using UPQC

Figure 4.9. Load Current

Waveform using UPQC

Similarly, the waveforms for double line to ground fault can also

be observed.