Project 2 - Modeling of 3 phase Induction Motor Drive

Project:-

Question@1) Model 3 Phase Inverter using Simulink (model the parasitic as well) with a switching frequency of 10Khz using 3 phase Squirrel Cage Induction motor, using V/F method, open loop.

Design Parameters:

1. Power = 100 HP
2. DC Voltage = 800 V
3. Output Voltage = 460 VRMS – line to line
4. Initial Speed = 1500 RPM
5. Final Speed = 1000 RPM
6. Initial Load Torque = 10 Nm
7. Final Torque=20 Nm
8. Torque Step Time = 0.1 secs

Aim) The main aim is Design the 3 Phase Inverter using Simulink and Controlling the 3 phase Squirrel Cage Induction motor, using V/F method from 3 Phase Inverter.

ANSWER :-

   Three-phase inverter is used to change the DC voltage to three-phase AC supply. Generally, these are used in high power and variable frequency drive applications.

                            

             Generally, the three arms of this inverter will be delayed with 120 degrees angle to generate a 3 phase AC supply.
The switches used in the inverter have 50% of ratio and switching can be occurred after every 60 degrees angle. The switches like S1, S2, S3, S4, S5, and S6 will complement each other. In this, three inverters with single-phase are placed across a similar DC source. The pole voltages within the three-phase inverter are equivalent to the pole voltages within the half-bridge inverter with a single phase.

 

Simulink Model :-

 For creating the Simulink model of 3phase inverter for the V/F method controlling of 3 phase Squirrel Cage Induction motor we have to used the following blocks:-

1. DC Voltage source
2. MOSFET
3. LCfilter
4. Asynchronous Machine(SI Units)
5. Rate Limiter
6. Induction Machine ScalarController.
7. Scalr converter
8. Zero order Hold
9. Vdc Filter
10. Saturation
11. PWM Generator (Three-phase, Two-level)
12. Step
13. Terminator
14. Product
15. Bus selector
16. DMux
17. From
18. Goto
19. Gain
20. Power Gui
21. Constant
22. In1 port
23. Outport 
24. Scope

 Total Simulink Model:-

The total simulink model is as folowes:-

                       Fig-->Simulink model of Asynchronous MAchine with 3phase inverter V/Control

Procedure:-

>>For modelling the controlling of 3 phase squirrel cage Induction motor by using the V/F method with 3phase Inverter by using the following steps.

>>firstly we are created the 3 phase inverter by using the "MOSFET" as power switching device 

>>The inverter subsystem block in Simulink as followes .

                  

                                    Fig--->Three phase inverter

>>This 3phase inverter will consists a three legs with 2 numbers of Power switch (MOSFET) for each leg

>>these 6 Power switch (MOSFET) will operate both high(positive signal) and low(negative) Signal operation.

>>The gate pulses are getting from the Vif Controller Method Subsystem.

V/F controll Subsystem:-

>>The V/F subsystem will consisits the following Model for controlling signals.

                        Fig__>V?F controlling model

>>In this method we have to controll the Machine by sending the Pulse /gate signals to the Inverter .

>>for this controller we are converting the reference speed to Frequency by using the Following blcoks.

>>The reference Speed will getting from the Rate Limitor block with (500 to -1500 rpm) limits.

>>And this will be devided with the 1 over frequency followed by poles gain blocks.

>>And dc voltage reference is also feed to te PWm threephase generator.

>>and this will create the gate pulses as per the controlling of frequency method.

>>After getting the pulses from the V/F controller then the Inverter start the working .

>>the output supply (3phase ) will be connected to the Asynchronous Machine(SI Units) block with using the RC filter block.

Asynchronous Machine parameters:-

>>RC FILTER :-

>>in this model we are used the motor as 

Induction Motor model –  Squirrel Cage Preset Model – 05 , for 100HP Motor

rated voltage :-460 V

RPM:-1780 RPM

>> From this way are controlling the three phase induction motor with V/F method of 3 phase inverter.

>>the requirement outputs will be plotted by using Scope as followes.

 

OUTPUT PLOTS:-

Stator Voltage and Phase Current :-

>>from the above graph we get the Voltage and current of stator for the 3 phase induction motor.

>>the top plot will gives us the Ststor current current

>>The Bottom plot will proved the nature of Ststor Voltage.

Top plot(Ststor Current):-

>>The current flow throug the Ststor winding will plotted in above graph.

>>The Current will consists a following statistics.

>>The Maximum current flow throug the Stator is =1.24e2 Amps at 1.353 sec.

>>The Minimum current flow throug the Stator is =-1.29e2 Amps at 1.375 sec.

 

Bottom plot(Ststor Voltage):-

>>The Voltage flow throug the Ststor winding will plotted in above graph.

>>The Voltage will consists a following statistics.

 

>>The Maximum Voltage flow throug the Stator is =2.741e1 V at 1.886 sec.

>>The Minimum Voltage flow throug the Stator is =-3.314e1 V at 1.976 sec.

 

Frequency :-

>>The frquency will plotted By using the Below graphih

>>The Above graph will gives us the how we controlle the frequency method  for the 3 phase induction motor.

>>The minimum and maximum frequncy is given as by usinh the following ststistics.

>>the minimum frequency is 0 HZ

The maximum frequency controll is done upto 33.3 HZ at time of 2 sec.

 

Speed and Torque:-

>>The Speed and Torques of the Motor will be plotted and attached the graph below.

>>From the Above Graph we will get the Speed and Torque 

>>the top plot is for the Speed of the Motor.

The Bottom plot will be the Torque of the Motor.

Top Plot(Speed):-

>>The speed Of the motor will be consists a following stastistics.

>>the minimum speed od the motor is 1.01 e2 RPM at 3.619 sec

>>The Maximum spedd will be 1.885e2 RPM at 0sec

 

Bottom plot(Torque):-

>>The TorqueOf the motor will be consists a following stastistics.

>>the minimum Torques will be -5.723 Nm at 3.483 sec

>>the maximum Torue will be 7.682e1 Nm at 3.722 sec.

 

Results :- The Controlling of 3phase induction motor using the Method of V/F 3phase inverter will acheved properly and explained with relevent Models .

------------------------------------------------------------------------------------------------------------------------------

Question@2)

Use the 3 phase inductor motor theory to derive the transfer function of 3 phase Induction Motor.

 

Aim)The main aimis derive the Transfer Function  for the 3 phase indunction motor using the Thory of the  3 phase indunction motor.

ANSWER)

3 phase indunction motor:-

        A 3-phase induction motor consists of a stator and a rotor. The stator carries a 3-phase stator winding while the rotor carries a short-circuited winding called rotor winding. The stator winding is supplied from a 3-phase supply. The rotor winding drives its voltage and power from the stator winding through electromagnetic induction and hence the name.

Equivalent circuit of  Induction motor:-

                        

                                  Fig-->Equivalent circuit of  Induction motor

 

Procedure for Transfer Function of Induction Motor :-

The transfer function of Induction Motor will be determined by using the Following steps.

 For finding the Transfer function we have to used the below image for reference purpose :-

                                

                                 Fig--->Electric motor physical model

Step@1)

The equatation for the electrical part will be returened as followes :-

Applying KVl: to the circuit 

then,

Σ voltage = 0

therefore 

V-IaRa-IaLa-e = 0------------------(1)

 

Step@2)

Now the Motor Constraints and Rotational part equatations are writen as followes :-

   

 

Therfore ,

Transfer Function for Induction Motor is given as followes:-

Transfer Functuon Induction Motor:-


               Wm / e =KtS / (JS²+DS) (Ra+LaS)+KbKtS

 

Result :- The TransferFunction For the three Phase INduction Motor Is determined.

 

------------------------------------------------------------------------------------------------------------------------------

Question@3)
Model 3 phase induction motor with a 3 phase inverter using Direct Torque control using an Average Model, Implement both torque and flux control to achieve desired power.

Aim)The main aim is develop the simulink model for the 3 phase induction Motor with using the DTC(Direct Tarque Method).

ANSWER)

For creating the Simulink model of 3phase inverter for the DTC(Direct Tarque Method)  method controlling of 3 phase Squirrel Cage Induction motor we have to used the following blocks:-

1. Three-phase voltage source
2. Universal Bridge
3. Two level Converter
4. Asynchronous machine
5. Direct Torque Controller
6. Series RLC branch
7. Stair generator
8. IGBT
9. Discrete Integrator
10. abc to Alpha-Beta-Zero
11. selector
12. Fcn block
13. Triganometric Function
14. Multi poert Switch
15. Relational Operator.
16. Saturation
17. Logical Operator
18. Relay
19. Goto
20. From
21. In1
22. Out
23. Bus Creator
24. Gain
25. determiend reuired VEctor
26. Vector to Pulses generator
27. Scope
28. Power gui

 

The figure below illustrates the strategy used to determine the best voltage vector when the flux linkage is located in sector 0.

 

 

The image shows four cases:

When the flux linkage vector moves to sector 1, the selected voltage vectors become V4 for case 1, V3 for case 2, V1 for case 3, and V6 for case 4, and vectors V2 and V5 are not used. This 60 degree shift in the voltage vectors happens each time the flux linkage vector enters a new sector.

Total SImulink model :-

The total simulink model is attached below.

 

 

PROCEDURE :-

>>thre phase induction motor is controlled By using the direct Torque method is as followes .

>>firstly we take the Supply source ab=nd sentd to the DClink capacitor by using the universal bridge block works as Diode rectifier.

>>after that te supply from the Dc link is fed to the Two level converter  block.

>>from this inverter Synchronous machine .

>>the motor is working Based on the commands from the Converter Signal block.

Design parameters :-

Voltage Source Block :-                                          Universal Bridge Parameters :-

                         

 

Two level Inverter Block:-

 

Asynchronous Machine :-

>>the Inverter will works the Signals commands what we generated by using the Direct Torque method 

>>Direct torque control (DTC) is a technique that allows you to instantaneously control the motor magnetic flux and its electromagnetic torque in a decoupled way. Controlling the torque directly permits accurate static and dynamic speed regulation.

The main components of the DTC subsystem are:-

Flux and Torque Calculation:-

      The stator flux linkage is estimated by integrating the stator voltages, and torque is calculated based on the estimated flux and the motor currents.

>>this Flux and Torque calculation is desin by using he abc to Alpha-Beta-Zero block are send to the transfer fucntion block.

>> from this two abc to Alpha-Beta-Zero blocks we are created the three output signals ,Those are Phasem magnitude phase angle and torques output.

 

Speed Regulator:-

   The regulator compares the actual motor speed with the speed reference and generates the torque reference.

>>This block implements a speed regulator using an ant-windup PI controller.

>>From this Pi controllwer we are using the  logical operation block as Or gate 

>>after getting the signals we are sending these signals to relational operation block to get the Signals as per the requirements.

 

Hysteresis Control:-

     The calculated flux magnitude and torque are compared with the reference values. When the resulting flux or torque error crosses either the positive or negative hysteresis band value, a control signal is activated in order to correct the error.

 

>>this Blcok is totally implemented by using the Saturation blocks for both torque and fkux cobtrolling the at the output side from this blcok.

 

Optimal Switching:-

     Pulses to the motor inverter are produced based on the control signals generated by the hysteresis control and the stator flux linkage position.

>>Based on the space vector specified, the block generates pulses for a two-level three-phase converter.

>>Based on the order number coming from the couple(T) & flux (phi) hysteresis controls, and on the sector number (flux position), the block determines the required voltage space vector (0-7).

 

>>after Completion of this Controll blcok modeling the Gate pulses are send to the two level Converter gate terminal.

>>In this way we get the gate signal by using the Controll og DIRECT tOrque Controll Method.

 

>>the Output values are plotted by using the Scope Block.

MATLAB_CODE@)

%% Parameters file for SPS model: power_motordrive_IM_DTC_HYST.slx
%
Ts_Power=25e-6;  % SPS sample time (s)
%
%%Induction motor parameters

Pn  = 111.9e3;      % Nominal power (W)
Vn  = 460;          % Nominal rms phase-to-phase voltage (V)
fn  = 60;           % Nominal frequency (Hz)
Rs  = 30.2e-3;      % Stator resistance (Ohm)
Lls = 0.283e-3;     % Stator leakage inductance (H)
Rr  = 17.21e-3;     % Rotor resistance, referred to the stator side (Ohm)
Llr = 0.283e-3;     % Rotor leakage inductance, referred to the stator side (H)
Lm  = 10.95e-3;     % Mutual inductance (H)
J = 2;              % Inertia (kg.m^2)
Friction = 0.02154; % Friction factor (N.m.s)
p = 2;              % Number of pole pairs
Tn= Pn/(2*pi*fn/p);                    % Nominal torque (N.m);
phi_n=(Vn/sqrt(3)*sqrt(2)/(2*pi*fn));  % Nominal flux (V.s)


%%Control parameters
Ts_Control=25e-6;         % Control sample time (s)

% Speed regulator
wref_RateOfChange=1200;   % Maximum rate of change for speed reference (RPM/s)
Kp_wreg=100;              % Proportional gain          
Ki_wreg=1000;             % Integral gain
Limit_wreg=1.5*Tn;        % Regulator output(torque) limit 
T_hyst_band=10;           % Torque hysteresis band (% of nominal torque)
phi_hyst_band=4;         % Flux hysteresis band (% of nominal flux)


%%DC link
Clink = 25e-3;    % DC link capacitor (F)

% Braking chopper
Rbrake=8;              % Resistance (ohm)
Switch_on_point=710;   % Switch on point (V)
Switch_off_point=665;  % Switch off point (V)

 

 

OUTPUT PLOTS :-

PLOT@1)

VSUpply and  Isupplu and VDC:-

>>From the above graph we get the Grid Voltage (Top Plot) , grid Current (Middle Plot) and Dc voltage (Bottom plot).

Grid Voltage/ supply voltage  (Top Plot):-

>>The grid will gives us the three phase voltage source with Following Statistics.

Signal@1) Yellow phase.

>>From the graph the signal one is yeello phase with following statistics.

>>Maximum voltage is 3.77e2 V at the time interval 0.570 sec

>>Miniimum voltage is -3.77e2  V At the time interval 0.562 sec

 

Signal@2):-

>>From the graph the signal twois Blue phase with following statistics.

>>Maximum voltage is 3.78e2 VV at the time interval 0.559 sec

>>Miniimum voltage is -3.77e2 V At the time interval  of 0.567 sec

 

Signal@3):-

>>From the graph the signal Three is Red phase with following statistics.

>>Maximum voltage is 3.77e2 V at the time interval 0.565 sec

>>Miniimum voltage is -3.748e2 V At the time interval 0.556 sec

 

 

Grid Currents @ Middle Plot) :-

>>The three phase  currents are explined with following signal statistics.

 

Signal 1:-

>>From the graph the signal one is yeello phase current with following statistics.

>>Maximum Currentis 9.452e1A  at the time interval 0.570 sec

>>Miniimum voltage is -9.348e1 A  At the time interval 0.561 sec

 

Signal 2:-

>>From the graph the signal twois Blue phase with following statistics.

>>Maximum Currentis 9.348e1 A at the time interval 0.561 sec

>>Miniimum voltage is -9.452e1 A At the time interval 0.570 sec

 

Signal 3:-

>>From the graph the signal Three is Red phase with following statistics.

>>Maximum Currentis 9.425e1 A at the time interval 0.567 sec

>>Miniimum voltage is -9.446e1 A At the time interval 0.573 sec

 

VDc Voltage plot(Bottom):-

>>The source Dc voltage is having the following statistics.

>>Maximum DC voltage 6.446e2 at the time interval 0.359  sec

>>Miniimum voltage is -6.408e2 A At the time interval 0.569 sec

 

 

MOTOR PARAMETERS :-

SPEED ,Torque ,Phi value and Current for the Motor :-

>>From the above graph we can get the total motor parameters values Graphical representation.

 

Speed(TOP Plot):-

>>From This plot we get the Values of Bith Reference Speed and Motor Speed  With Following Charactaristics.

Reference Speed :-

The reference Speed Consisits following Statistics.

>>The Maximum Speed of reference Signal is 1.500 e3 RPM  at1.50 sec

>>The Minimum Speed  of reference Signal is 0 at 0 sec.

 

Motor Speed :-

The Motor Speed Consisits following Statistics.

>>The Maximum Speed of Motor  is 1.5004e3 RPM  at2.009 sec

>>The Minimum Speed  of reference Signal is 0 at 0 sec.

 

 

Angle_phi Plot( Second Plot):-

>>this plot will give the reference Angle and Motor Rotaion Angle also.

Reference Phi Plot:-

>>the reference phi having the Folowing statistics

>>The Maximum Phi value of reference is 9.993e-1 at 3.500 sec

>>The Minimum Phi value of reference is 8.967e-1 at 0 sec

 

Motor Phi Value:-

The motor Phi having  the following Statistics.

>>The Maximum Phi value of Motor is 1.029 at 3.752sec

>>The Minimum Phi value of Motor is 5.662e-22  at 0 sec

 

Torque  Plot(Third Plot):-

>>the Torque Plot will gives us the Reference, Motor and LOad Torque graphical representation.

Reference Torque:-

The reference Torque having the Following Statistics.

>>The MAximum Torque is 5.478e2 at 1.522 sec

>>the Minimum Torue is -1961e+2 at3.317 sec

 

The Motor Torue:-

The torue of motor consists a following statistcs.

>>The MAximum Torque is 5.602e2 at 1.522 sec

>>the Minimum Torue is -2.823e2 at 2.902 sec

 

The Load Torque:-

The Load Torque  consists a following statistcs.

>>The MAximum Torque is 5.00e2 at 1.500 sec

>>the Minimum Torue is 0.00 at 0.0 sec

 

Armature current(bottom Plot) :-

The armature Current of motor consisits a following statistics.

 >>The maximum current drawn by the armature is 1.370e3 Amps at 0.104 sec

>>The minimum current drawn by the armature is -9.851e23 Amps at 0.108 sec

 

Result :- The 3 phase induction motor is controoled By using the Direct Torque method is explained with relevent Simulink model.