Questions for computer models, 1995



Computer Models - Practice Exercises ESD.126, 2002

Assigned: Monday, February 25

Due: Monday, March 18 (Late assignments marked down)

Assignment

To gain experience using the computer models available for the project, answer the following questions. Feel free to work with others, but everyone should hand in their own anwers. The objective of this assignment is to get everyone familiar with the models - the input data they require, the types of calculations they perform, and output that can be expected - and to begin understanding their limitations - what they will NOT do for you.

The three models, PowerPlan, PCCum and PowerWorld, and their manuals are available in the TPP computer room. The manuals are in a black notebook that is in the box that previously held the reading packet. The computer models themselves are on a CD in the inside cover of the notebook with the manuals. Copy the models onto any PC you’d like to use. There are also zip files for each model which you can copy onto a disc and put on your own computer. Feel free to e-mail them to yourself to use somewhere else as well. Please do not remove the CD or the manuals from the TPP computer room.

** PCCum must be in a directory named C:\Symphony ** It must always be in this directory. For any computer on which you install PC Cum, you must put it in C:\Symphony. PowerPlan and PowerWorld can be anywhere. (PC Cum and PowerPlan are a bit archaic, but they are free so they are the best and only option for us. PC Cum uses an industry standard algorithm, it’s just the user interface that is dated.)

Using PowerPlan

This model is the most interactive of the computer models to be used for the energy system design project. It can be used to quickly test the affects of any proposed changes to the energy system. Some of the output from this model, such as emissions output and reliability, overlaps with that from PCCum, allowing a comparison of these calculations. In addition, PowerPlan will be used to test projections of demand growth, and determine the LDC (load duration curve) after renewable technologies and DSM programs are added to the energy system. And finally, the input database for PowerPlan includes table of many country-specific economic variables which you will eventually need to input. The complete manual for this program is available in the TPP computer room.

Choose any of the available databases to answer the following questions. You will be building your own database for the country you choose for the project.

Assignment

1. What is the current level of emissions (SO2, CO2, NOx) from the Energy System you chose? What is the current reliability?

2. Run PowerPlan for one year into the future: Hypothesize and add a one year projection of demand growth. Choose one (or more) renewable technology or DSM (demand side management) programs to add to the Energy System, and the generating capacity needed to meet the demand growth. Add this technology/program and run PowerPlan for one year.

a. How much did emissions change? reliability?

b. How was the LDC affected? Which category of generators (baseload, intermediate, peaking) is most displaced by your addition, and how does this displacement relate to the emissions and reliability changes noted above? Note: Record 21 data points for this new LDC to be used in question 3 for PCCum.

Notes on Using PowerPlan

The ’esc’ key is the magic key that gets you out of menus. Use it liberally.

Type ’pp’ to start the program (once you are in the correct directory, which is TPP126/PPLAN)

(If you want to make major edits to the database/input file use the ppedit program. To do this type ’ppedit lebanon’ . The ’page down’ key moves you through the different pages. You do not need to do anything in ppedit for these questions if you don’t want to.)

An example of one way to begin using PowerPlan

type ’pp’

hit any key to quit the first screen

the initialize menu should be highlighted - hit the ’return’ key

use the arrow keys to ’select country’ - hit ’return’

use the arrow keys to select ’Lebanon Base’ (hit ’return’)

the program will initialize

after a couple of seconds an info window will appear at the bottom. if you want help do what it says, otherwise hit ’esc’

use the arrow keys to select the ’calculate’ menu - hit ’return’

enter ’y’ - the first year will be simulated, and PowerPlan asks if you want to simulate the next year

hit ’esc’ (note - entering ’n’ may do no good)

select the output menu - (beware: the Environment and the Dem Reduction choices have a good probability of making the computer hang, so wait until you’re more comfortable with things before you try them) Play around with the other choices.

use the ’esc’ key to get back up to the top menu bar when you are done with the output menu.

The modify var menu has an option for viewing, changing and getting the numerical values for the LDC.

The decisions menu lets you add new capacity and conservation programs. When adding new plants or conservation programs, use the (G) choice, not the (N) choice in the submenu. (G stands for graphic. It tends not to work if you use the (N) choice). Once you are into the graphical display, the top half of the screen will show your options - use the left/right arrow keys to add capacity of any of these options; use the up/down arrows to move between options. When you’ve added some capacity, hit ’return.’ The bottom half of the screen displays the capacity and demand trajectories, and the LDC. you can add capacity, see what it looks like, change your mind, try it again ... When you want to run the next year’s simulation, hit ’esc’ answer ’y’ (assuming you do want to test your changes). Answering ’y’ at this point makes your changes permanent - there is no going back unless you restart the program!

Hit ’esc’ a couple more times to get back to the top menu bar, go to the calculate menu and simulate the next year.

Now go back to the output menu, check your results. And then go add more capacity ... That’s all you need to do for now.

To quit, go to the file man menu, select ’quit’ and answer ’y’

Using PCCum

PCCum is a production -cost model for electric power systems, which determines the economic dispatch of the given power system, and reports the cost, reliability and emissions from producing the energy required to meet the given demand. The input and output parameters for this model are described in the documentation available in the TPP Computer room.

Questions:

1. What is the effect of a relative shift in fuel prices (for example oil price increases by a factor of 2)?

a. What is the overall effect on the cost of system operation brought about by this shift in fuel costs?

b. How does the shift affect the loading order (merit order, dispatch order) of individual plants? Is this important? If so, why? What effect might this shift have on future capacity planning decisions?

2. Given the existing capacity, what effect would an increase in peak and energy of 10% have? (the shape of the load duration curve remains constant but its overall magnitude shifts upward by 10 %)

a. How is the loading order affected? Why?

b. What is the affect on total system cost? Why?

c. What is the affect of this change on the reliability of the system? Why?

d. What is the affect on system emissions? Why?

3. This question addresses a shift in the shape of the load curve, from perhaps the inclusion of DSM programs, renewable energy technologies, or shifts in demand patterns. Hypothesize and sketch a new “net LDC” and input the new 21 data points into PCCum. (Alternatively, you could get the new LDC from Power Plan under the menu output>LDC. You can move the cursor around with the arrow keys, and the coordinates are reported to the left of the graph.) Run PCCum with this new LDC and compare the results to the run with the original LDC.

a. How is the loading order affected? Why?

b. What is the affect on total system cost? Why?

c. What is the affect of this change on the reliability of the system? Why?

d. What is the affect on system emissions? Why?

Qualitatively:

e. How do you think the capacity mix (technology mix) should be changed to reflect the changes in the demand pattern?

f. If the peak demand grew by 10 %, but total energy demand remained relatively constant, what impact would this have on costs? reliability? loading order? What might be the (characteristics of) the next unit purchased?

Using PowerWorld

PowerWorld is an interactive load flow program. The version available for ESD.126 is an older version (but available for free), of a existing, widely used product. This is the only model that we will be using that includes the transmission system in the analysis. In contrast to the other two models, is used to determine the transmission line flows and generator outputs for a given snap-shot view of the power system. This information lets you know if the power system changes that you propose (such as building new plants or transmission lines, or decommissioning plants or transmission lines) will adversely affect system stability.

To run PowerWorld

1. Open the program

2. Select ‘open simulation case’ from the file menu.

3. Make sure that the program is in run mode (rather than edit mode), and click ‘single solution.’

4. Record requested information (in questions below).

a. For generator information go to the ‘Case Information’ menu and select generator records. This sheet can be recorded by clicking the ‘copy’ button, in the center-top of the generator record sheet, and pasting the data into excel or other external program.

b. For line flows, put the model in ‘run mode’ and right click the line. An information box will pop up with the power flow on the line (Generator information can also be obtained by right clicking on the generator while the model is in run mode.)

c. Or – you can use the ‘Make Reports’ option from the top part of the ‘Case Information’ menu to record whatever you like (note, you must be in run mode for the ‘Make Reports’ option to show up)

5. If you want to watch the flows, you can begin the simulation when the model is in run mode.

6. Switch to edit mode to make requested changes.

7. Make changes requested in the questions below, run the model by switching to run mode and clicking ‘single solution,’ and record information requested.

Questions

1. Select any of the sample systems provided (B2, B3, B5R, B7 or Example). Run the ‘Single Solution’ option and record (be sure to let me know which sample system you are using)

a. Generator output for all generators (note that MW is the real power output, and Mvar is the reactive power)

b. Line flows for all lines

2. Change the impedance of one or more of the lines (change the reactance and or the resistance by about an order of magnitude in order to observe significant changes to the system flows). Record

a. What you did (the changes you made)

b. Generator output

c. Line flows

3. Change the line limit of one or more of the lines. Play around with value(s) you use until your changes have a noticeable impact on the system. Record

a. What you did (the changes you made)

b. Generator output

c. Line flows

4. Remove a line, generator or load from the system (assuming there is more than one) and record

a. What you did

b. Generator output

c. Line flows

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