The document discusses the alleviation of voltage sags and swells in distribution networks using custom power devices, specifically D-STATCOM and DVR, which are effective in improving power quality. It presents simulation results showing that both devices significantly enhance voltage stability, with DVR demonstrating superior performance in restoring voltage levels. The conclusion highlights the efficacy of these devices in addressing power quality issues without the need for additional filter components.

1. VOLTAGE SAG AND SWELL ALLEVIATION IN DISTRIBUTION NETWORK USING CUSTOM POWER DEVICES; D-STATCOM AND DVR.
Presented
By
Gaddafi Sani Shehu

2. INTRODUCTION
•Duetorapidtechnologicalinnovationsandhikeinworldpopulation, highqualityandreliableelectricalpowerdemandhassignificantlyincreasedrecentlywhichisroughlyestimatedtodoublebynextdecade.
•Thisheavyburdenonthepresenttraditionalpowersystemsleadstomanypowerqualityproblems;voltageinconstancy,poorreliability, frequencyfluctuations,causedontransmissionanddistributionlines.
•Morethan90%ofalltheproblemsinpowersystemsareconsequenttovoltagesagsandswells.

3. Toovercomethesehurdles,widerangeofpowerelectronicsdevicesemergedandmodifiedtoimprovetheirperformance.
•SecondgenerationpowerElectronicsdevicesundertheumbrellaofFlexibleAlternatingCurrentTransmissionSystem(FACTS)andCustomPower(CP)arethebestoptionwhenitcomestovoltagestability,reactivepowercompensation,powerfactorcorrectionandharmonicslevelreduction.
•Amongthesedevices,D-STATCOMandDVRhaveshownanexceptionalperformanceduetotheirfastresponseandreal-timecontrolability.

4. CUSTOM POWER DEVICES; D-STATCOM AND DVR
DistributionStaticCompensator(D-STATCOM)
DSTATCOM Schematic representation

5. D-STATCOM TEST DISTRIBUTION SYSTEM
3.5 [ohm] #1#2 dcCurDC Current 12 800.0 [uF] 3252426222 V_dcDC VoltageILRMS VoltageVpu150 [ohm] 1.35 [H] VABus 1 g4g6g2g5g3g1 VpuPWMControlVoltageControlVpuShftBus 2TimedBreakerLogicOpen@t0SWITCHBSWITCHATimedBreakerLogicOpen@t0SWITCHARLSWITCHB26.0 [ohm] VACapacitiveload20 [uF] CouplingTransformerBalanced three phase fault, forcreating voltage sag at asimluation period of 0.25sec andlasted for additional 0.25sec. D-STATC... VnInst. VoltageTimedFaultLogicABC 1.0 [ohm] 0.33 [H] Measurements andControls

6. DYNAMIC VOLTAGE RESTORER (DVR)
. DVR building components

7. DVR TEST DISTRIBUTION SYSTEM
dcCurDC CurrentdcVltgDC VoltageFAULTSCBAABC->GTimedFaultLogicRMS VoltageVpuVpuPWMControlVoltageContolVpuShftBRK2Instanteneous VoltageVn5.25 [ohm] 12 350.0 [uF] 3252426222 VA g4g6g2g5g3g1 BRK2BRK3BRK1BRK3BRK1 #1#2 TimedBreakerLogicClosed@t00.02263 [H] 0.02263 [H] 0.02263 [H] .55 [ohm] .55 [ohm] #1#2#1#2 R=0Balanced Three Phase Fault forcreating the Voltage Sag at 0.75sec which lasted for 1.00 secBy-Pass SwitchesControlsVoltage SourceConverterBy-Pass SwitchesCouplingTransformersVoltage and PWMControlsTimedBreakerLogicClosed@t0TimedBreakerLogicClosed@t0ABCR=0CBASWTCHSWTCHTimedBreakerLogicOpen@t0VA0.0052 [ohm] ABCABC11 [kV] #2#111 [kV] 100.0 [MVA] 2.50 [uF]0.0052 [ohm] 0.0052 [ohm]2.50 [uF] 2.50 [uF] 1.0 [ohm] 1.0 [ohm] 1.0 [ohm]

8. TEST SYSTEM AND SIMULATION RESULTS
(D-STATCOM SIMULATIONS AND RESULTS)
• Voltage Variation at Load Point without D-STATCOM • Voltage Variation at Load Point with D-STATCOM
System Voltage at PCC w ithout D-STATCOM
Time(s) 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 ...
...
...
0.00
0.20
0.40
0.60
0.80
1.00
1.20
Voltage (pu)
RMS Voltage w ithout D-STATCOM
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
Voltage (kV)
Instanteneous Voltage Without D-STATCOM
System voltage at PCC w ithout D-STATCOM
Time(s) 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 ...
...
...
0.00
0.20
0.40
0.60
0.80
1.00
1.20
Voltage (pu)
RMS Voltage w ithout D-STATCOM RMS Voltage w ith D-STATCOM
-10.0
-5.0
0.0
5.0
10.0
Voltage (kV)
Instanteneous Voltage w ith D-STATCOM

9. SUMMARY OF VOLTAGE SAG AND SWELL ALLEVIATION USING D-STATCOM.
Voltage
Simulation
Time (sec)
Without
DSTATCOM
With
DSTATCOM
RMS
(pu)
Normal supply
0.952
0.998
0.25 ≤ ts ≤ 0.50
0.793
0.995
0.75 ≤ ts ≤ 1.00
1.146
1.002
Instantaneous
(kV)
Normal supply
10.472
10.978
0.25 ≤ ts ≤ 0.50
8.778
10.945
0.75 ≤ ts≤ 1.00
12.606
11.022

10. DVR SIMULATIONS AND RESULTS
System voltage at PCC without D-STATCOMTime(s)0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 ... ... ... 0.00 0.20 0.40 0.60 0.80 1.00 1.20 Voltage (pu) RMS Voltage without DVRRMS Voltage-10.0 -5.0 0.0 5.0 10.0 Voltage (kV) Inst. Voltage

11. SUMMARY OF THE RESULTS
Voltage
Simulation
Time (sec)
Without DVR
With DVR
RMS
(pu)
Normal supply
0.932
0.998
0.25 ≤ ts ≤ 0.50
1.140
1.001
0.75 ≤ ts ≤ 1.00
0.778
0.996
Instantaneous
(kV)
Normal supply
10.252
10.978
0.25 ≤ ts ≤ 0.50
12.540
11.011
0.75 ≤ ts ≤ 1.00
8.558
10.956

12. CONCLUSION
•AnelectromagnetictransientmodelofembeddedDistributionStaticCompensator(D-STATCOM)andthatofDynamicVoltageRestorer(DVRs)hasbeenpresentedusingPSCAD/ETDMCsoftwaretotesttheefficacyofthesedevicesinassuagingvoltagedipsandswells.
•Thedevicespresentedhaveshowngreatperformanceinalleviatingthedisturbances.ItcanbededucedfromtheresultsobtainedthatDVRclearsthevoltageinstabilityandrestoressystemvoltagemuchbetterthanD-STATCOM.
•Additionalbenefitderivablefromtheseschemesistheabsenceoffiltercomponentasthereactanceofthecouplingtransformersservethatpurpose. .