This document presents a hysteresis current controller for single-phase three-level voltage source inverters. Conventional hysteresis current control has variable switching frequency that depends on load parameters, which makes the system complex. The proposed method modifies the hysteresis current controller to make the switching frequency independent of load by dynamically varying the hysteresis bandwidth between switching intervals based on mathematical equations. The results show this method provides constant switching frequency, low switching losses, and simple control logic implementation while maintaining benefits of hysteresis current control.

1. A HysteresisCurrent Controllerfor Single-PhaseThree- LevelVoltageSource
Inverters
presented by
NITISHKUMAR(M160493EE)
APR 4 ,2017
NIT CALICUT
Faculty advisor : Dr. jagadanand g
1

2. CONTENTS
INTRODUCTION
OBJECTIVES
HYSTERESIS CURRENT CONTROLLER
REQUIREMENTS AND PURPOSE
MODIFIED SCHEME
FUTURE SCOPE
RESULTS AND CONCLUSION
REFERENCES
2

3. INTRODUCTION
 To get the desired output voltage in single-phase VSI , we use
Square-wave PWM
Single-pulse PWM
Sinusoidal PWM
Modified-sinusoidal PWM
But these type of converter is not having control over output current
When output of inverter have to fed to drives or machines whose
torque control is more necessary over other parameters then the
necessity of current control comes into the picture.
3

4. OBJECTIVES
To see what is hysteresis current controller
To see how the switching frequency vary with respect to load in the case
of hysteresis current controller.
 To see how to make it independent from load parameters.
4

5. Whyhysteresiscurrentcontroller
The hysteresis current control technique has proven to be the most
suitable solution for applications such as active filters, machine drives,
and high-performance converters .
The harmonic performance of a hysteresis current controller can be
substantially improved by varying the hysteresis band over each
fundamental cycle to maintain a constant switching frequency
5

6. Whatishysteresiscurrentcontroller
6

7. singlephaseinverter
withmotorload
And block diagram
of pulse generator
7

8. Basicrequirementsandpurpose
The basic requirements for the current controllers are low harmonics
to reduce losses, low torque pulsation, low noise in the motor, and fast
response in order to provide high dynamic performance.
 The purpose of a current controller is to control the load currents by
forcing them to follow the reference currents.
8

9. mathematicaldescriptionofswitchingfrequency
When switch 1and 2 conducts, 𝑉𝑑 = L ∗
𝑑𝐼
𝑑𝑡
+ 𝐸𝑐
𝑇𝑂𝑁 𝑜𝑓 𝑡ℎ𝑒 𝑠𝑤𝑖𝑡𝑐ℎ =
𝐿∗∆𝐼
𝑉 𝑑 −𝐸 𝑐
When feedback diode will conduct, -𝑉𝑑-𝐸𝑐-L*
𝑑𝐼
𝑑𝑡
=0
𝑇𝑂𝐹𝐹 of switch =
𝐿∆𝐼
𝑉 𝑑+𝐸 𝑐
Time period T=𝑇𝑂𝑁 + 𝑇𝑂𝐹𝐹
T=
𝑉 𝑑∗𝐿∆𝐼
𝑉2
𝑑−𝐸2
𝑐
Switching frequency(f)=𝑓𝑚𝑎𝑥 ∗ (1 −
𝐸 𝑐
2
𝑉 𝑑
)
9

10. Continued…..
Induce EMF in motor drive can be taken as.
𝐸𝑐 = 𝑚 ∗ sin 𝑤𝑡
f=𝑓𝑚𝑎𝑥 ∗ (1 −
𝑚2∗(sin 𝑤𝑡)2
𝑉2
𝑑𝑐
)
f=𝑓𝑚𝑎𝑥*(
1−𝑚2
𝑉2
𝑑𝑐
−
𝑚2∗cos 2𝑤𝑡
𝑉 𝑑𝑐
)
We can see that the switching frequency of switch is having a constant
and a variable component ,this is undesirable.
 Though the performance of hysteresis current is very good but the
variable switching frequency makes the system complex ,costly and
sophisticated.
10

11. MODIFICATIONSINHCC
Conventional current control has the disadvantage of dependency of
switching frequency on load parameter and has a variable switching
frequency. So we adapt a new technique for making the switching
frequency independent of load parameters like inductance , resistance
etc.
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12. Proposedhysteresiscurrentregulation
12

13. Mathematicaldescription
𝑉𝐼 − 𝐸 = 𝐿
𝑑𝐼
𝑑𝑡
+ 𝑅𝐼 For single phase 3-level inverter
𝑉∗ − 𝐸 = 𝐿
𝑑𝐼∗
𝑑𝑡
+ 𝑅𝐼∗ If ideal voltage 𝑉∗ is used for getting 𝐼∗
𝑉 − 𝑉∗
= 𝐿
𝑑𝐼 𝑒
𝑑𝑡
𝑡1,𝑁,then 𝑉∗
= 𝐿
𝐵1
𝑡1,𝑁
For 𝑡1,𝐴, 2𝑉𝑑𝑐-𝑉∗
=L
𝐵1
𝑡1,𝐴
𝑉∗ = 2𝑉𝑑𝑐
𝑡1,𝐴
𝑡1,𝑁+𝑡1,𝐴
13

14. Continued ….
If V* is assumed constant over the switching period
𝑉1
∗
= 2𝑉𝑑𝑐
𝑡1,𝐴
𝑡1,𝑁+𝑡1,𝐴
= 𝑉2
∗
= 2𝑉𝑑𝑐
𝑡2,𝐴
𝑡2,𝐴+𝑡2,𝑁
Using similar triangles, this relationship can be written as:
𝑡1,𝑁
𝑡2,𝑁
=
𝑡1,𝐴
𝑡2,𝐴
=
𝐵1
𝐵2
=
𝑇1
𝑇2
By using above equation we can write,
𝐵2 = 𝐵1
∆𝑇−𝛿𝑡2
∆𝑇+𝛿𝑡2−𝛿𝑡1
(A)
𝑡2,𝐴 = 𝑡1,𝐴
∆𝑇−𝛿𝑡2
∆𝑇+𝛿𝑡2−𝛿𝑡1
(B)
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15. 15

16.  Equation (B) defines the active switching interval required in
the next half switching period to precisely restore the inverter
operation to a constant switching frequency with centered
active pulses.
 Equation (A) defines about that hysteresis bandwidth to
achieve the same objectives.
 Together, these two equations show clearly that there is no
difference in principle in using either time or hysteresis
bandwidth as a switching control parameter and the selection
of either alternative depends only on the hardware used.
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17. DISADVANTAGE
Additional complex system is required for calculating time and
bandwidth for next switching interval in addition to hysteresis current
controller
Very fast ADC is required( sampling frequency-25 MHZ)in order to
convert the analog domain error to digital domain.
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18. FUTURE SCOPE
It is having system efficiency of 96.7 percent , so it can further
modified to increase the efficiency.
In this case it is showing stable response up to 5 kHz, so it can be
further extended for greater frequency.
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19. RESULTSANDconclusion
The proposed method has the following advantages which make it an
attractive option for hysteresis current controlled single-phase three-
level VSIs:
It has all the benefits associated with hysteresis current control
Switching frequency is constant between two adjacent switched
output voltage
Low switching losses
Simple control logic and flexible implementation
19

20. references
[1] Huifeng Mao, Xu Yang, Zenglu Chen, Zhaoan Wang , “A Hysteresis Current Controller For Single-
Phase Three level Voltage Source Inverters,” IEEE Transaction on power electronics, vol.27, no.7, July
2012
[2] Firuz Zare, Gerard Ledwich, “A Hysteresis Current Control for Single Phase Multilevel Voltage
Source Inverters: PLD Implementation,” IEEE Transaction on power electronics, vol. 17, no.5,
Sepetmber 2002
[3].G.H. Bode, D.G. Holmes “Load Independent Hysteresis Current Control of a Three Level Single
Phase Inverter with Constant Switching Frequency ,”IEEE Transaction on power electronics, 2001
[4].K.M.Rahman, M.Rezwan Khan, M.A.Choudhury, “Variable Band Hysteresis Current Controllers for
PWM Voltage-Source Inverter,” IEEE Transaction on Power Electronics,vol. 12, no.6, November 1997
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