## ENG733S2 Smart Grid Fundamentals

24 Mar
ENG733S2 Smart Grid Fundamentals
Coursework
Deadline For Submission: Thursday 29 March 2018
Submission Instructions Submit your report via Moodle unit website
Instructions for completing the
assessment:
 Details are provided in the document. Further information and clarifications can be given during the lectures, if needed.
Examiners: Professor Victor Becerra

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Part 1. Microgrid design.
This part of the coursework consists of the design of a large microgrid that can supply a DC load.
Your goal is to design a microgrid that can operate exclusively on renewable energy.
To do so you will need the following information:
Assume that all days in the year are the same, and within each day there are four time periods,
with the properties shown in Table 1.1.
Solar PV can be built for a capital cost of £2000/kW (all costs included)
Wind can be built for a capital cost of £1500/kW (all costs included)
Battery storage can be built for £400/kWh + £100/kW. For example, the capital cost to build a
10 kW storage plant that can store 20 kWh, will be:
£500 £100
20 kWh 10kW £11,000
kWh kW
   
Assume that battery storage system will have a round trip efficiency of 85%.
The allowed depth of discharge of the battery is 80%. This means that the state of charge of the
battery should not be allowed to go below 20%.
Assume that the operating costs for the resulting system are negligible, that the system will last
for 25 years, and that you can obtain a 25 year loan at 5% interest for this project.
Table 1.1: Load, wind and solar data

 Time Load (kW) Wind (kW/kW) Solar (kW/kW) 12am-6am 10 0.90 0.05 6am-12pm 20 0.30 0.40 12pm-6pm 25 0.20 0.40 6pm-12am 15 0.60 0.05

Note that in Table 1.1, kW/kW refers to generated output (in kW) per unit of installed capacity (in kW).
Given these assumptions, you are required to:
a) Give an expression for the total initial cost of the microgrid
b) Calculate a suitable value of the battery capacity and power rating considering its efficiency
and allowed depth of discharge. Use manufacturer’s data for actual lead acid batteries to
select a battery bank that can be purchased in the market and that is reasonably close to your
calculations.
c) Provide a charge/discharge schedule for the battery. Note that in order for the schedule to be
a feasible solution, the amount of energy in the battery will need to be the same at the
beginning and the end of each day (since this pattern repeats day after day).
d) Calculate a suitable power rating of the wind generator. Use manufacturer’s data for actual
DC wind generators to select a power rating that can be purchased in the market and that is

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e) Calculate a suitable power rating of the solar PV system. Use manufacturer’s data for actual
PV panels to select a power rating that can be purchased in the market and that is reasonably
close to your calculations. Specify how many panels would be required.
f) What would be the total initial cost of the microgrid? Can this cost be reduced to a minimum?
g) Calculate the annual loan repayment amount, given the total initial cost, the loan period of 20
years and the annual interest rate of 5% for the configuration that you found to give the
minimum initial cost.
h) What would be the minimum price in £/kWh at which the generated energy can be sold to the
customer to recover the annual loan repayment amount given the total annual load in kWh?
In the report, please ensure that you:
1. Clearly explain your method (including computer code, if appropriate). Explain your equations.
2. Clearly describe your solution, paying particular attention to ensure that your solution is
feasible. Use tables and, if appropriate, graphics to present your results. Show what each
resource is doing during each of the four time periods.
Part 2. Economic dispatch and optimal power flow analysis.
2.1 Power system data
Consider that in a simple power system there are four power plants. The generating plants capacity,
type and marginal costs are:
1. 1100 MW nuclear plant with marginal cost of £10/MWh, connected to bus 1.
2. 600 MW coal plant with marginal cost of £20/MWh, connected to bus 2.
3. 400 MW natural gas plant with marginal cost of £30/MWh, connected to bus 3.
4. 100 MW of diesel units marginal cost of £150/MWh, connected to bus 5.
Every day there are four 6-hour periods of demand:
12am-6am: 800 MW
6am-12pm: 1200 MW
12pm-6pm: 1920 MW
6pm-12am: 1600 MW
The system consists of a network with 5 buses. The load above is distributed evenly among the five
buses. The transmission lines (branches) have the data shown in Table 2.1.

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Table 2.1: Transmission line data

 From Bus To Bus R X Power limit (MW) 1 2 0 0.1 400 1 3 0 0.1 400 2 3 0 0.1 400 2 5 0 0.1 300 3 4 0 0.1 300 4 5 0 0.1 300

Given this information, do the following.
2.2 Economic dispatch / power flow problem
a) Solve the simple economic dispatch problem for each time period. Report the system marginal
price.
b) Solve the DC power flow problem for this system at each time period.
c) For each time period report (in a table) the flows on the transmission lines for your solution
2.3 Optimal power flow
a) Solve the optimal power flow problem for this system at each time period.
b) For each time period report (in a table) the flows on the transmission lines for your solution
c) For each time period report (in a table) the locational marginal prices (LMPs).
2.4 Discussion
a) What is the impact on this power system of having transmission line constraints?
b) How might smart grid technology impact this power system?
c) How should this system be upgraded to improve its operation?
General guidance and Information
You should produce a report addressing Parts 1 and 2, reflecting as appropriate the structure of this
coursework brief. The maximum word count for your report is 2000 words, excluding the cover page.
Your report should briefly introduce each sub-problem, describe the method(s) used, and present the
results obtained, including where appropriate details of the calculations made and computer code
used (if any), ensuring that the specific questions asked in parts 1 and 2 are answered.
If you are including computer code, please ensure that the computer code that you have written is
inserted within a numbered textbox, so that it can be referred to from within the text as if it was a figure
(for example, you may write “
see the computer code in Figure 2”)
You are free to use specialist software tools that may be available to you to solve the problems
involved in this coursework. Details of suitable tools will be given in the lectures.
You can include screenshots of the software package used and computer generated plots, if
appropriate. You are only allowed to work on your own, no team work is permissible.
The report will be marked out of 100 marks, with part 1 having a maximum of 50 marks, and part 2
having a maximum of 50 marks.
For the marking criteria, please turn over.

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Marking Scheme
80% and above (Distinction)
an outstanding depth and breadth of work carried out, showing exceptional and thorough knowledge of the
relevant field
exceptional insight, critical analysis and originality, such as might make the work of comparable quality with
published work in its field
an excellent and well-defined focus, clear structure
clearly presented and well written, with no significant errors of syntax or expression
accurate numerical results, excellent use of tables and graphics to present information
70-79% (Distinction)
an outstanding depth and breadth of work carried out, showing thorough knowledge of the relevant field
outstanding insight, critical analysis and originality, showing the potential to make a real contribution to the
field of study
an excellent and well-defined focus, clear structure
clearly presented and well written, with no significant errors of syntax or expression
accurate numerical results, very good use of graphics and tables to present information
60-69% (Merit)
a good range of work carried out, showing a good level of knowledge of the relevant field
a good level of insight and critical analysis
a well-defined focus, clear structure
clearly presented and comprehensible throughout, with very few significant errors of syntax or expression
mostly accurate numerical results, good use of graphics and tables to present information
50-59% (Pass)
a sufficient range of work carried out, showing a competent knowledge of the relevant field
some evidence of insight and critical analysis
an identifiable focus and structure
presented with sufficient clarity to be comprehensible throughout, though there may be some errors of
syntax or expression
reasonably accurate numerical results, reasonable use of tables and graphics to present information
40-49% (Fail)
evidence of relevant work carried out, but with a limited or flawed knowledge of the relevant field
little evidence of insight and critical analysis
lack of clarity of focus and structure, and an inadequate argument
presented with sufficient clarity to be generally comprehensible, though there may be errors of syntax or
expression
mostly inaccurate numerical results, insufficient, inadequate or inaccurate use of tables and graphics to
present information
0-39% (Fail)
insufficient work carried out, and a very limited or flawed knowledge of the relevant field
insufficient evidence of any insight and critical analysis
lack of focus and structure
the prose may be unclear and difficult to comprehend, and there may be serious and frequent errors of
syntax or expression
very inaccurate numerical results, inadequate, erroneous or grossly inaccurate use of tables and graphics
to present information