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EE559: Control and Applications of Power Electronics Project II EE559: Control and Applications of Power Electronics PROJECT II BATTERY OPERATED INDUCTION MOTOR DRIVE Cheruvattath Sneha Tavadia Urvakhsha

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Page 1: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

EE559: Control and Applications of Power Electronics

PROJECT II

BATTERY OPERATED INDUCTION

MOTOR DRIVE

Cheruvattath Sneha

Tavadia Urvakhsha

Topic Introduction:

Page 2: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

The selected topic is Battery Operated Induction Motor Drive. The system is as given below:

It consists of a motor modelled as a RL load connected to a Diode Neutral Point Clamped Inverter. Through a

DC link implemented by a battery that can behave as a voltage source, the inverter is connected to a Quazi Z-

Source Converter made to work as a rectifier and helps control and stabilize the grid voltage.

MAIN COMPONENTS:

I. Diode neutral Point Clamped Inverter: This circuit is basically a modified three level Voltage

Source Inverter (VSI), which is bidirectional, with each leg per phase that contains two series

switches on the high-side and two on the low-side. Often IGBTs are used in this circuit. It can be

configured in two ways. Firstly, using ideal switches and secondly, using controlled voltage and

current sources. For this simulation the second configuration or model has been used as it is better

suited for real time simulations with high switching frequencies.

Fig 1: Diode Neutral Point Clamped Inverter

Page 3: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

The operating principle of this system is pretty simple. These voltage levels appear at the output of each phase

of the inverter by appropriate switching. The middle point of the two capacitors is denoted as ‘n’ which is the

neutral point. There are two complementary switch pairs (S1, S3 ) and (S2, S4 ) and two clamping diodes (D1,

D2 ) per phase present in this inverter. The outer two switches are the main switching devices (S1,S3 ) that

operate for pulse width modulation while the inner two switches are the auxiliary switching devices (S2,S3 )

that clamp the output terminal potential to the neutral point potential along with the help of the two clamping

diodes. When both the upper switches S1 and S2 turn on, the voltage across ‘a’ (the first phase) and ‘0’ (the

negative inverter terminal), also called the pole voltage, is Vdc. The lower clamping diode, D2 balances out the

voltage sharing between the two lower switches, S3 and S4 . While the switch S3 blocks the voltage acrossthe

upper capacitor C, the switch S2 ’ blocks the voltage across lower capacitor C. The voltage between ‘a’ and ‘0’

is the DC voltage whereas the voltage between ‘a’ and ‘n’ is the AC voltage. It is because the voltage appearing

with respect to the negative inverter terminal (‘0’) is the voltage across each capacitor and the voltage appearing

with respect to the neutral point of the inverter (‘n’) is the aggregate of the capacitor voltages; giving an AC

waveform.

Advantages:

1. Minimum capacitance is needed

2. DC link capacitors can be charged beforehand

3. High efficiency operation

Disadvantages:

1. More clamping diodes

2. Neutral point control should be achieved for all conditions

Applications:

1. Renewable Energy

2. Electric Vehicles

3. Motor Drives

I. Quazi Z source converter : This converter functions as a buck-boost system which uses a DC-DC

converter bridge because of its unique topology. These systems are extremely efficient and are used

mainly in electric power conversion applications. It can boost the input voltage through a switching state called the shoot-through state. The shoot-though state here is the simultaneous conduction of both switches of the same phase leg of the inverter. This operation state is forbidden for the traditional voltage source inverter (VSI) because it causes the short circuit of the dc-link capacitors. The unique feature of this QZSI is that it is bidirectional. So, we can reverse the inductor currents and reverse power delivery from ac to dc. And the ripple current is reduced due to the

Page 4: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

capacitors giving rise to better operating conditions. Finally the additional switch S7 helps eliminate discontinuous conduction.

Fig 2 : Topology of Quazi-Z source Inverter [1]

Modes of Operation:

Mode 1:

Fig 3: Mode 1 [1]

State: shoot through state

S7: open

Characteristic: Current decrease in inductors and charging of capacitors

Mode 2:

Page 5: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

Fig 4: Mode 2 [1]

State: zero state

S7: closed

Characteristic: positive inductor current and increase in capacitor voltages

Mode 3:

State: active state

S7: closed

Characteristic: same as the previous mode, capacitors still charging

Fig 5: Mode 3 [1]

Page 6: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

Mode 4:

State: active state

S7: closed

Characteristic: iL < 0, |iL | < |IPN | /2.

Fig 6: Mode 4 [1]

Mode 5:

State: active state

S7: closed

Characteristic: iL < 0, |IPN | /2 < |iL | < |IPN |

Fig 7: Mode 5 [1]

Page 7: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

Mode 6:

State: active state

S7: closed

Characteristic: iL < 0, |iL | > |IPN |

Fig 8: Mode 6 [1]

Mode 7:

State: zero state

S7: closed

Characteristic: inductor current increase and capacitor discharges

Page 8: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

Fig 9: Mode 7 [1]

Advantages:

1. Works as a buck-boost converter

2. Load can be inductive, capacitive or another Z-source network

3. Main circuit of ZSI is either CSI or VSI

4. Source can be current or voltage source

Disadvantages:

1. Since it can only operate as buck or boost, the output range is limited.

2. Sensitive to EMI and can get damaged

3. Lower reliability

4. Main switching device cannot be interchanged for CSI and VSI

Applications:

1. Renewable Energy

2. Electric Vehicles

3. Motor Drives

Page 9: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

REFERENCE SIMULATION:

Fig 10: System model from the reference paper

1. DC Side Controller Design:

The DC side closed loop system with feed forward compensation ability is mainly designed to stabilize the DC

link voltages. This is done by using a constant reference value to enable efficient operation. So here instead of

DC link voltage Vc1 voltage is given to the controller to establish the relationship as follows.

Vc1=Vin+Vdc2

So, with his logic the voltage of capacitor c1 is regulated. And in this way feed forward feature is also implemented.

2. AC Side Controller Design:

This is used mainly for the motor control which can be seen from fig 10. This strategy has to be quick to avoid oscillations. Any change in the DC side can affect or limit the performance of the DC side. To avoid such disturbances the solution is to use a higher input voltage.

Page 10: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

3. Circuit Parameters:

The parameters in the reference paper consulted were obtained using the formulas as given

Voutput=

Vin∗11−2D

∗1

√2∗(1−D)

L=

Vin∗1−Dmax1−2Dmax

∗Dmax

f∗1

ℑ∗2 rc

Where rc is the ripple and Im is magnetizing current

ℑ=2 PmaxVin

C1=C 2=

2∗Dmaxf

∗Pmax

Vin∗1

Vpn∗2 rv

Where rv is ripple voltage and Vpn is maximum voltage stress

Vpn= 11−2Dmax

∗Vin

The PWM carrier frequency used is 5kHzand switching frequency is 10kHz.

4. Simulation Results:

Page 11: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

Fig 11: Results of Controller Design

Page 12: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

Fig 12: Results for input voltage, C1 voltage, ac output current, dc input current

Fig 13: Results for reverse power flow

IMPLEMENTED SIMULATION:

The system has been implemented as given below:

1. Neutral Point Diode Clamped Inverter:

Page 13: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

Fig 13: Simulation of NPC

The NPC circuit is a pretty straight forward simulation. The voltage value used here is based on the value given

in the question 240V line to line. For the internal values for the diodes as well as the IGBTs the default values

are maintained. To give the circuit a more practical edge, a controlled voltage source is used in series with a

resistance of 1ohm. The capacitance values have been modulated via trial and error and has been finalized to

1uF. A PWM system is used to give pulses to the IGBTs. A repeating sequence along with three sine waves

with different phase differences (of 120 degrees) is used. The signal is to power the high side switches and the

signal is sent through the NOT operator to power the low side switches.

Page 14: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

2. Quazi Z Source Inverter:

Fig 14: Simulation of QZSI

The main QZSI circuit simulation is straightforward, the real logic is in implementing the control systems.

Fig 15: Simulation of AC control system

The current from the grid lines is given to a mux and demux to obtain a single signal. This signal is then

converted to dq using a abc to dq0 transformation block in sim power systems. The second input is given via the

constant ramp function whose slope is 2*pi*60. This signal is now given to a PI controller and the output is

converter back to abc using a reverse transformation block. This output along with the output from the DC

controller side is given to a bus and in turn to a pwm generator and that is used to feed the IGBTs.

Page 15: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

Fig 16: Simulation of DC controller

Here the control system from the reference paper is implemented. Using summer blocks and product blocks we

implement the formula

Vc1=Vin+Vdc2

Where Vdc=Vc1+Vc2

The values for the system components have been calculated from the aforementioned formulae and then a bit of

approximation has been done to get more accurate results. C1= C2= 70uF and L1=L2= 250uH.

3. Motor:

Fig 17: Simulation of Induction Motor Drive

A three phase source is given to the induction motor drive block. To maintain an ideal torque, the value 1 is

given to the torque input. The output of this is given to the NPC via a controlled voltage source. The values for

these have been selected keeping in mind the given values with a bit of trial and error.

Page 16: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

4. Grid:

Fig 18: Simulation of Grid

A three phase source is given to the transformer via a three phase breaker and then connected to the grid

inductances. The values for these have been selected keeping in mind the given values with a bit of trial and

error.

OUTPUT:

The output voltage was a sine wave that came upto about 450V. There were still some ripples in the output that

could not be completely eliminated.

REFERENCES:

[1] F. Guo, L. Fu, C.-H. Lin, C. Li, W. Choi, and J. Wang, "Development of an 85-kW Bidirectional Quasi-Z-

Source Inverter with DC-Link feed-forward compensation for electric vehicle applications," IEEE Transactions

on Power Electronics, vol. 28, no. 12, pp. 5477–5488, Dec. 2013.

[2] Y. Liu, B. Ge, and H. Abu-Rub, "Theoretical and experimental evaluation of four space-vector modulations

applied to quasi-z-source inverters," IET Power Electronics, vol. 6, no. 7, pp. 1257–1269, Aug. 2013.

Page 17: Battery Operated Induction Motor Drive

EE559: Control and Applications of Power Electronics Project II

[3] M. . Nguyen, Y. . Lim, and J. . Choi, "Two switched-inductor quasi-z-source inverters,"IET Power

Electronics, vol. 5, no. 7, pp. 1017–1025, Aug. 2012

[4] W. Bai and K. Lee, "Distributed generation system control strategies in Microgrid operation," IFAC

Proceedings Volumes, vol. 47, no. 3, pp. 11938–11943, 2014.

[5] W. Bai, M. R. Abedi, and K. Y. Lee, "Distributed generation system control strategies with PV and fuel cell

in microgrid operation," Control Engineering Practice, Feb. 2016.

[6] Y. Liu, B. Ge, and H. Abu-Rub, "Modelling and controller design of quasi-z-source cascaded multilevel

inverter-based three-phase grid-tie photovoltaic power system,"IET Renewable Power Generation, vol. 8, no. 8,

pp. 925–936, Nov. 2014.

[7] R. Zhu, Y. Tang, and X. Wu, "Duty cycle-based three-level space-vector pulse-width modulation with

overmodulation and neutral-point balancing capabilities for three-phase neutral-point clamped inverters," IET

Power Electronics, vol. 8, no. 10, pp. 1931–1940, Oct. 2015.

[8] D. Vinnikov and I. Roasto, "Quasi-Z-Source-Based isolated DC/DC converters for distributed power

generation," IEEE Transactions on Industrial Electronics, vol. 58, no. 1, pp. 192–201, Jan. 2011.

[9] D. Vinnikov, I. Roasto, T. Jalakas, and S. Ott, "Extended boost Quasi-Z-Source Inverters: Possibilities and

challenges," Electronics And Electrical Engineering, vol. 112, no. 6, Jun. 2011.