MMME4056MM4ISA …Integrated Systems Analysis
Autumn 2019COURSEWORK. 30 of moduleSet onOctober 1st. Submission due: November 7th.
SYSTEM DESCRIPTION.
Figure 1 shows a schematic of a standalone system comprising: a diesel engine DE, a DC motorgenerator MG and a battery Batt..The DE and MG units are connected via a flexible coupling.
kT
kT
Inputs
Inputs
IMG
IMG
DE
DE
MG
MG
To the Load
To the Load
FlexibleCoupling
FlexibleCoupling
SW
SW
Batt.
Batt.
FIGURE 1.Schematic of a standalone system.
The requirement of this coursework is to understand the dynamics of this system and to simulate its behaviour using SIMULINK. Systems such as the one shown here are present in many locations acting as emergency generatorsenabling a load such as a hospital or pharmaceutical plant or datacentre to keep on going in the event of a powercut on the grid. For simplicity here, we do not include any study of the load.
Startingup this system comprises the following sequence of events:
The system begins with zero rotational speeds for DE and MG, zero currents flowing and 50 of full battery charge in place. The switch SW is open initially.
Switch SW is closed so that the engine starts up. IMG is the current coming out of the MG and this current is negative whilst the engine is starting but becomes positive or much less negative when the engine is running.
After a period of 60 seconds for starting, the value of kT is changed linearly over another 60 seconds from its original value so that IMG becomes 5000A and the battery is recharging.
The submission should be based on what is explicitly asked for in this coursework specification. The primary material being marked is a reportalthough you are asked to submit your SIMULINK models also. It must be possible to open the SIMULINK models submitted using release R2019a of MATLAB. Models presented in different releases that cannot be opened from R2019a will not be marked.
FILES PROVIDED TO YOUAND WHAT THEY DO.
CWSpec.docx:This file. It contains the coursework specification.
DEchek.m:A MATLAB script. It shows how the function fDE below can be called from the MATLAB command line and provides a good graphical description of the performanceavailable from the diesel engine. This script has no direct use in this coursework.
fDE.m:A MATLAB function. You will use this indirectly. You should not modify it.
simDE.slx:A SIMULINK model of the diesel engine only. This model is run from starthere.m. This SIMULINK model is very useful because it shows how to use an Interpreted MATLAB Function in SIMULINK.
studdata.xls:An EXCEL spreadsheet containing one row for each student.Each row contains in this orderRMG, LMG, kT initial, , kc and cc
starthere.m:A MATLAB script. This opens up a SIMULINK model of the diesel engine only,simDE.slx and then runs the model and plots both DE andDE vs. time. You might choose to copy and then modify this script so as to use it as a way to open and run yourown SIMULINK models. To get going on this CW, look inside starthere.m and run it by either clicking the big green arrowhead in the top toolbar or else by just typing starthere at the MATLAB command prompt.
WHAT TO SUBMITPLEASE READ THIS CAREFULLY!
Submit your coursework via MOODLE as a ZIP file. This ZIPfile should contain the coursework report itself as a WORD document and all files that you used in the CW. Please adopt the filenaming suggested in this coursework specification. Filenames are presented here between chevronbracketse.g. starthere.m.
IMPORTANT:Please make clear on the first page of the report which student you are by identifying which row of the spreadsheet applies to you. If, for some reason, you do not find your name in the spreadsheet containing individual data, please pick a row for which no name is assigned and use the data that one. Report THAT row number.The coursework report should comprise only the following components:
A response to Task 1: This should be just four lines of text.
A response to Task 2. Show legible views of the main model and the subsystem model.Provide plots of IMG and MG and report, accurately, the values of IMG, MG and MG at t5s in text.
A response to Task 3. A picture of the toplevel system diagram no Scopes present. Also provide plots of each one of the system statevariables over the 60s simulation time and a plot of the calculated coupling torque. Report the final value of that calculated coupling torque accurately in the text.
A response to Task 4. A picture of the revised toplevel system diagram showing how the coupling torque is fed back into both the DE and MG units. Also show a plot of the coupling torque, plots of DE and MG vs. time on the same plotting window and a plot of IMG for the 60second period. Report the final values of the coupling torque, DE , MG and IMG accurately in the text.
A response to Task 5. Show the new part of the model used to ramp the value of kT up or down and plot kTt vs. time. Also plot the coupling torque over that period and, separately, plot IMG vs. time. State, in the text, what the final value of kT must be such that IMG reaches 5000A at the end of this simulation. Show what values of kT60 were trialled and what were the associated final values of IMG60 and MG60.
TWO NOTES ABOUT SIMULINK FOR THIS COURSEWORK
In each model used here, go to SimulationModel Configuration ParametersSolver and set the value of Relative Tolerance to 1e9.This will ensure accurate results and smooth graphs.
In each model used here, go to SimulationModel Configuration ParametersDiagnostics and set both Algebraic Loop and Minimise Algebraic Loop to None. This will avoid some possible frustrations.
THE COURSEWORK REQUIREMENT5 TASKS.
Task 1. Based on the equations that are supplied later for subsystem DE and MG, identify what are the state variables and what are the inputs for each subsystem. 10 marks
Task 2.You have been supplied already with SIMULINK model simDE.slx which contains a subsystem model of the diesel engine. Constant input values are fed into that subsystem model. Create a new SIMULINK model called simMG.slx which should contain a subsystem model of the motorgenerator machine. The inputs to the subsystem model should be VMG voltage across the terminals of the machine and TMGS shaft torque acting on the machine in that order.The outputs from the subsystem model should be IMG, MG, MG in that order representing the current, rotor speed and rotor angle of the MG respectively.
Set the initial values of all state variables to 0 within that subsystem model and run the simulation for 5 seconds with inputs ofVMG 20 V,TMGS 250 Nm and kT set to the value allocated to you individually.
Note that the subsystem model for the motorgenerator may make use of an interpreted MATLAB function as simDE.slx did or it may simply use icons to construct the correct signal relationships. If an interpreted MATLAB function is used, that function should be named fMG.m.
30 marks
Task 3.Create a new SIMULINK model called simSYS1.slx. Copy the subsystem from simDE.slx into this new model and, immediately below this, copyin the subsystem from simMG.slx also. Use the following set of input values:TDES 50 Nm,TMGS 250 Nm and both kT andshould be set to the values allocated to you individually. Apply equation 7 to determine VMG based on how much current is flowing intofrom the battery. The initial values of all state variables should be zero in this simulation except DE0 100 rads and DE0 1 .
Include some elements into the model to calculate using equation 8 what the coupling torque would be if the angles DE, MG and the angular velocities DE, MG emerging from the two subsystem models were correct. Remove all Scope blocks from the model once it is working so that all information from the simulation is extracted via workspace variables.
30 marks
Task 4.Copy SIMULINK model simSYS1.slx to a new model named simSYS2.slx. Replace the constant inputs originally present for TDES and TMGSwith the value calculated as the coupling torque. Note this model now contains real feedback. The other inputs to the two subsystems in this model should be as they were for Task 3 and the initial values of all state variables should also be as per Task 3.
20 marks
Task 5.Copy SIMULINK model simSYS2.slx to a new model named simSYS3.slx.
Change the initial values of all state variables in simSYS3.slx to be identical to the final values of the same state variables in simSYS2.slx. Introduce a new part into the model so that the value of kT varies linearly between the value, kT0 supplied to you individually and a final value, kT60, according to
Determine what value kT60 should have if IMG605000A. Note that t here represents the time since the start of the simulation of simSYS3.slx and does not include the 60 seconds of startup from simSYS2.slx.
10 marks
SUBSYSTEM DESCRIPTIONS:
The Diesel Engine DE: A MATLAB function called fDE.m is provided which computes the net torque developed internally by the dieselengine. It has one input argument and this is a vector having 2 entries. The first entry in this input vector is speed in rads and the second entry is the effective throttle setting, DE not .
It is possible to test fDE.m once by typing for example
u200; 8; TDEintfDEu
In the above, u is the input vector containing 200 rads as the rotational speed, , and 8 as the effective throttle setting, DE.
The dynamic equations for the dieselengine are
1
2
3
where TDEint represents the net torque developed by the engine itself and TDESrepresents the shaft torque experienced at the engine shaft. Clearly, a positive value of TDEint tends to accelerate the engine and a positive value of TDEStends to decelerate it. The shaft power coming out of the engine is .
The inertia of the engine is fixed as25 kgm2.
Do not editfDE.m.
The MotorGenerator MG:The MG inertia is 40 kgm2.The generator accounts for no significant mechanical drag torque but it does exert a torque opposing the rotation of the rotor when power is being drawn from it. This resisting torque is . Thus one dynamic equation for the MG is
4
Shaft power going into the MG is . The MG causes an electromotive force EMF of kT to exist in its windings.This EMF is what tries to drive current. Notice that when the machine is in an equilibrium condition, and the mechanical power drawn from the generator rotor is . This is exactly the same as the power being pumped into the electrical circuit of the MG. The rate of change of the MG current is given by
5
The MG has inductance LMG and it has internal resistance, RMG. Different values for these parameters are supplied to individual students. The units are Henrys and Ohms respectively. The final dynamic equation for the MG is this trivial one relating angle to angular velocity
6
The Battery.
The battery has negligible inductance but it has a constant internal resistance, RB20106 Ohms.When the battery is connected to the motorgenerator, the terminal voltage is determined by
7
We will not model the state of charge of the battery.
The Flexible Coupling.
The flexible coupling is a mechanical connection between the diesel engine and the electrical machine. When this coupling is in place, the shaft torque acting on the diesel engine is identical to the shaft torque acting on the electrical machine and this torque is determined by
8
whererepresents the torsional stiffness of the coupling Nmrad and whererepresents its torsional damping Nsrad. Individual values for these constant values are given to each student in the spreadsheet.
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