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Objective

To develop a simplified radial load flow analysis program and perform a study on a low voltage distribution feeder and observe the impacts of varying real and reactive power flows, fluctuating loads, embedded solar PV generation and energy storage on the network’s performance.

Access to computer and suitable programming tools, e.g. MATLAB, Excel/Visual Basic, C , etc.

Analysis of complex meshed electricity networks requires the use of computer software such as load flow packages, especially as the process is non-linear.  Modern packages are very sophisticated and offer many “what-if” study capabilities, such as load variation, reactive power and capacitor studies and first level contingency analysis.  Radial feeders however can be analyzed by simpler packages.  The basic radial feeder analysis technique covered in the unit lecture notes can be used as a basis for developing such a simplified radial load flow program.

Typical low voltage (LV) radial feeders in suburban residential areas in Australia operate at 415 volts 3-phase/240 V single phase.  A typical LV feeder will be 400-500 m in length and connect about 30 homes on a rotating (A-N, B-N, C-N, A-N), etc single-phase basis.  This is done to achieve as close to balanced 3-phase loading on the feeder as possible.  Each group of 3 single-phase loads will closely approximate a single balanced 3-phase load.  For the purposes of this analysis, you can assume 10 3-phase balanced loads on the feeder, instead of 30 single-phase loads.

The traditional power system has been designed on the basis of “top-down” load flows, from a few large centralized power stations through the HV transmission network down to the local radial LV network.  LV feeder layouts have been designed to handle both peak loading in terms of feeder maximum current (in the first section) and extremity voltage drop (at the end of the feeder) and also operate within voltage constraints of +/-5% of nominal voltage under both full and light (off-peak) conditions.  In recent years, the advent of affordable solar PV panels has resulted in the widespread use of roof-top solar home generation by many residential customers.  In fact, Australia has one of the highest solar-PV penetration rates in the world.  Whilst roof-top solar is positive for customers in terms of power bill reduction, self supply and environmental impact, it does have the potential to cause problems for the distribution grid, mainly in the middle of the day, when solar PV output peaks, but the customer load is low.  This can cause “backward” (feed-in) power flow up the LV feeder potentially resulting in excessive voltage rise as well as protection issues.

In addition, storage battery technology has progressed rapidly in recent years.  The long-dreamt of promise of cheap electric energy storage may become reality in the next 5 to 10 years (refer home battery solutions being offered by “Tesla” and many others).  Storage offers the possibility of limiting grid feed-in and energy savings to customers by taking advantage of excess solar PV generation in the middle of the day and storing this energy to be used at night, reducing customers’ peak load usage (at expensive tariff rates).  Peak reduction also offers considerable benefits to the grid owners, as grid capacity is linked directly to peak loading.  A reduced peak (“peak lopping”) as a result of correctly deployed storage could defer network capital expenditure and improve energy throughput capabilities of the entire electricity grid.

Your task will be to firstly develop a balanced, 10-node radial feeder analysis program, to simulate a typical suburban distribution network in terms of loads and feeder lengths and impedances and then perform a number of studies, covering peak and off-peak loading, impact of a fluctuating load, impact of solar-PV home generation and finally, the optimum location of battery energy storage along the feeder.

Review radial load flow analysis (including the equations for voltage and current) in the unit lecture material.

The test LV distribution feeder you are to analyse is shown in figure 1.  This uses loads and impedances typical of a suburban distribution system.  It consists of the Thevenin equivalent of the local distribution transformer (MV-LV) that supplies the LV feeder, the upstream grid supply, and 10 load-solar PV-storage pairs.  The upstream supply is assumed to be regulated at 415 volts, 3-phase on the LV bus and is the swing bus (system supply).  

Image 1

Each of the 10 nodes consists of a lagging power factor load (drawing P and Q), a solar PV generator (supplying P and either drawing or supplying Q) and a possible storage unit (supplying or drawing P and Q).  The net load on each node will be the sum of these P (real) and Q (reactive) power flows.
  1. Develop a radial load flow program and set up a uniformly distributed load feeder model of 10 equal loads.  Total feeder load = 100 kVA (3-phase), at peak, operating at 0.9 power factor lagging.  Total feeder length = 500 m.  The cable impedance = 0.315 +j0.365 ohms/phase/kilometre.  The peak load refers to the residential load curve at about 5 pm (refer Addendum).

  2. Run your load flow.  Are current and voltage constraints being exceeded?  Current constraint = 200 A/phase; voltage constraint = 415 V +/- 5%.   If the supply end voltage was raised above 415 V would this solve any peak load?

  3. Now, run the load flow for light-load conditions = 30% of peak load conditions (refer to the residential load curve at about 11 am).  Are voltage constraints being exceeded?  Record all your feeder current (supply end) and voltage drops. If the supply volts is raised as in 1(b) are voltages too high in light-load conditions?

  4. The load at node #10 is a large induction motor and is a fluctuating load.  Its starting current is 5 times its normal running load (as in part 1(b)) and starting power factor is 0.4 lagging.  Re-run your load flow and determine the change in voltage drop, at both node #9 and node #10.  Is the voltage drop at node #10 > 10%?  Is the voltage drop at node #9 (the “common point of coupling”) > 4%?
  1. With the loads the same, allow for embedded solar at each node.  Use the residential load curve.  The solar sources are generators, so they will be represented by negative real power loads.  Assume they will operate at unity power factor.  Run the load flow again for 5 pm afternoon peak load conditions.  The embedded solar = 0.3 * peak load.  Record your results.  Comment on the improvement in feeder current and voltage drop.

  2. Now, run the load flow for residential midday light load conditions, when embedded solar = peak load value, but the midday load is 0.3 * peak load (i.e. embedded solar = 3 * midday load).  Record your results.  Comment on the feeder current and voltage drop.  What happens to the voltage drop?  What is the voltage spread at the end of the feeder (node #10) from midday to evening peak situations with solar present?
  1. Using the same peak residential loads as before, consider one or more storage units being turned on over the peak period, so that they can lop 30% off the daily peak load.  From the residential daily load curve in the Addendum, calculate by numerical integration the total storage unit energy capacity required to achieve a 30% peak load lop for the residential load curves for the whole LV feeder.  (iii) What is the maximum load reduction possible through the use of energy storage and the energy required?

  2. Run the load flow for the 30% peak lop case, assuming the storage is split into 10 equal storage units of same total capacity as in a).  Assume the storage units act as generators running at unity power factor.  Compare to the base peak load case in section 1 b).  Comment on improvements in feeder current and voltage drop.

  3. Now assume the storage is available in only one unit of same total capacity as above.  Perform several runs of your load flow with the storage unit at several locations, including last node (#10), first node (#1) and also at several other positions along the feeder.  What yields the best result, in terms of feeder current and voltage drop?  How does this compare with section 3 b) above?  

Make some overall concluding remarks concerning LV feeder current and voltage control, the impact of embedded solar-PV and the best deployment of battery storage units.  Remember to submit all result from your load flow runs.  

The Load flow explanation of an electrical power system offers voltages at all the buses, power flows and losses in the lines at specific levels of power generation and loads. The outcomes of load flow analysis are cast-off in load predicting, system scheduling and operation. Essentially, system engineers execute load flows on a day-to-day basis with varying system configurations, load patterns and producing settings to comprehend the performance of the system at diverse operating circumstances.

To develop a simplified radial load flow analysis program and perform a study on a low voltage distribution feeder and observe the impacts of varying real and reactive power flows, fluctuating loads, embedded solar PV generation and energy storage on the network’s performance.  .

Let the Sbase=10KVA and Vbase=240v/phase=415v/line

Image 1

BUS NUMBER

REAL POWER

REACTIVE POWER

PHASE CURRENTS

BUS VOLTAGES

1

0.9

0.436

2.3073

   415

2

0.9

0.436

2.3073

415

3

0.9

0.436

2.1041

274.1

4

0.9

0.436

1.8863

332.9

5

0.9

0.436

1.6536

493.3

6

0.9

0.436

1.4061

661.6

7

0.9

0.436

1.1447

438.86

8

0.9

0.436

0.8708

421.5

9

0.9

0.436

0.2952

439.44

10

0.9

0.436

0

411.25

BUS NO

PHASE CURRENTS

BUS VOLTAGES

1

1.7856

415

2

1.6229

322.9582

3

1.4499

341.0636

4

1.2667

431.7459

5

1.0737

541.6766

6

0.8716

646.1511

7

0.6614

735.3562

8

0.4448

804.806

9

0.2236

438.98

10

0

478.24

BUS NUMBER

Phase_currents

Bus voltage in Kv

1

4.6005

0.415

2

4.4048

0.8911

3

4.1757

1.3887

4

3.9024

1.8684

5

3.5691

2.3196

6

3.153

2.7336

7

2.6215

3.0998

8

1.9365

3.4042

9

1.1133

3.6273

10

0

3.7457

BUS NUMBER

Phase_currents

BUS VOLTAGES in KV

1

1.7747

0.415

2

1.6129

0.5044

3

1.4418

0.6333

4

1.2614

0.7679

5

1.0723

0.8936

6

0.8755

1.0035

7

0.6729

1.094

8

0.4689

1.1628

9

0.2769

1.2083

10

0

1.2295

BUS NUMBER

Phase_currents

BUS VOLTAGES

1

2.7638

0.415

2

2.5396

0.3222

3

2.2875

0.4601

4

2.0104

0.6686

5

1.7129

0.8717

6

1.4004

1.0497

7

1.0788

1.1954

8

0.7554

1.3057

9

0.45

1.3784

10

0

1.4123

From the results the voltage drop across the feeder reduces because of the low flow of current. The voltage profile across the feeder depreciates with time. This is because the supply of power from the embedded system decreases with time.

The maximum load reduction is 28.95kVA. the storage capacity of the storage system should be greater than 250 kJ.

BUS NUMBER

Phase_currents

BUS VOLTAGES

1

4.0221

0.415

2

3.8197

0.4779

3

3.5863

0.8308

4

3.3139

1.2193

5

2.9921

1.5925

6

2.6078

1.9347

7

2.1461

2.2354

8

1.5946

2.4841

9

0.9582

2.6693

10

0

2.7796

NODE 1:

BUS NUMBER

Phase_currents

BUS VOLTAGES

1

3.8065

0.415

2

3.5956

0.3739

3

3.354

0.687

4

3.0749

1.0489

5

2.7499

1.3953

6

2.3692

1.71

7

1.9235

1.9833

8

1.4078

2.2063

9

0.8328

2.3698

10

0

2.4656

NODE 2:

BUS NUMBER

Phase_currents

BUS VOLTAGES

1

3.8084

0.415

2

3.6445

0.3889

3

3.4036

0.7062

4

3.1248

1.0728

5

2.7991

1.4245

6

2.4163

1.7447

7

1.966

2.0234

8

1.4421

2.2512

9

0.8546

2.4187

10

0

2.5171

NODE 7:

BUS NUMBER

Phase_currents

BUS VOLTAGES in Kv

1

4.0747

0.415

2

3.8691

0.5018

3

3.6318

0.8642

4

3.3544

1.2587

5

3.0262

1.6369

6

2.6336

1.9833

7

2.2644

2.2873

8

1.6888

2.5492

9

1.0151

2.7454

10

0

2.8625

NODE 10:

BUS NUMBER

Phase_currents

BUS VOLTAGES in Kv

1

4.4008

0.415

2

4.2013

0.6778

3

3.9687

1.1075

4

3.6934

1.5474

5

3.3615

1.9671

6

2.9539

2.3533

7

2.4453

2.6949

8

1.8093

2.9787

9

1.0516

3.1887

10

0

3.307

From the results the best position for the storage unit is to located at node 10 since it causes the profile of the feeder network to be almost flat.

From the calculated results it can be observed that the voltage profile in a LV feeder depends on the impedance of the cables, the power drawn by the loads connected to the feeder.  Embedded solar-PV and battery storage units helps to almost maintain a flat load curve. The storage units should be placed at the extreme node of the feeder away from the source. It will make the system to appear to be in a ring hence the effects of peak loading of the feeder reduced.

References

Conference Board of Canada. (2004). Electricity restructuring: opening power markets. Ottawa, Conference Board of Canada.

Grigsby, L. L. (2012). Power system stability and control. Boca Raton, Taylor & Francis. Available from; https://www.crcnetbase.com/isbn/9781439883204. Date of Access; 8th September, 2018

Musirin, I., & Sulaiman, S. I. (2015). Recent trends in power engineering: selected, peer reviewed papers from the 2015 9th International Power Engineering and Optimization Conference (PEOCO 2015), March 18-19, 2015, Melaka, Malaysia. Pfaffikon, Trans Tech Publications. Available from; https://search.ebscohost.com/login.aspx?direct=true&scope=site&db=nlebk&db=nlabk&AN=1060570. Date of Access; 8th September, 2018

Nagsarkar, T. K., & Sukhija, M. S. (2016). Power System Analysis: Power System Analysis. New Delhi, Oxford University Press India. Available from; https://app.knovel.com/hotlink/toc/id:kpPSAE0003/power-system-analysis. Date of Access; 8th September, 2018

World Bank. (2013). Vietnam Power Sector Generation Options. DC, Washington. Available from; https://hdl.handle.net/10986/12860. Date of Access: 14th May 2018

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"Simplified Radial Load Flow Analysis Program For LV Distribution Feeder." My Assignment Help, 2021, https://myassignmenthelp.com/free-samples/300197-power-systems-planning-and-economics/radial-load-flow-analysis-program.html.

My Assignment Help (2021) Simplified Radial Load Flow Analysis Program For LV Distribution Feeder [Online]. Available from: https://myassignmenthelp.com/free-samples/300197-power-systems-planning-and-economics/radial-load-flow-analysis-program.html
[Accessed 17 July 2024].

My Assignment Help. 'Simplified Radial Load Flow Analysis Program For LV Distribution Feeder' (My Assignment Help, 2021) <https://myassignmenthelp.com/free-samples/300197-power-systems-planning-and-economics/radial-load-flow-analysis-program.html> accessed 17 July 2024.

My Assignment Help. Simplified Radial Load Flow Analysis Program For LV Distribution Feeder [Internet]. My Assignment Help. 2021 [cited 17 July 2024]. Available from: https://myassignmenthelp.com/free-samples/300197-power-systems-planning-and-economics/radial-load-flow-analysis-program.html.

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