DC link ripple analysis on five phase pwm voltage source inverter with unbalance load

DC Link Ripple Analysis On Five Phase PWM Voltage Source Inverter With Unbalance Load

Presented by:Haryo Agung Wibowo (15862703)

Email: disiniharyo@yahoo.com

STUDY MOTIVATION

•Improve five phase inverter reliability to be able withstand working under any extreme operating condition, such as during faulted load condition

WHY WE SHOULD DO THIS?• Five phase basically give better fault tolerant

level. Motor still be able to run without loosing so much power, even motor are extremely faulted.

ELECTRICAL PERSPECTIVE• But from electrical point of view, motor fault will

rapidly elevate voltage ripple and introduce harmonic current at inverter input terminal.

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ELECTRICAL PERSPECTIVE• But from electrical point of view, motor fault will

rapidly elevate voltage ripple and introduce harmonic current at inverter input terminal.

AdditionalHarmonics

Capacitor Voltage Threshold(normally+10-12% rated Vdc)

Additional loss=In x Rc2

High Voltage Stress High Thermal Stress

ULTIMATE RESEARCH GOAL• Selecting proper capacitor size which perform

well under unbalance load

• To do this, we should concern at 3 main parameter:1.DC current ripple RMS value2.DC voltage peak to peak value3.DC current ripple harmonics spectrum

All must be analyzed under unbalance circuit operation

LITERATURE REVIEW

STARTING POINT OF ANALYSIS (I)

Easier to perform because can be resolved using algebraic manipulation.

However, DC current harmonics spectrum can not be analyzed

STARTING POINT OF ANALYSIS (II)

1. To achieve spectral decomposition, Current and voltage function must be represented by Fourier series.

2. The calculation will be exhaustive unlessmathematical analysis program is

utilized.

END

Research Background

• Electrical fault (short/open circuit) is likely to occur in the motor side

3 phase sources 3 phase rectifierAC/DC

5 phase inverterDC/AC

5 phase motor

5 Phase Inverter – Unbalance Load

1 1 1

2 2 2

3 3 3

4 1 4

5 1 5

sin

2sin 5

4sin 5

6sin 5

8sin 5

i I t

i I t

i I t

i I t

i I t

1 2 3 4 5

1 2 3 4 5

Unbalance

I I I I I

i1 i2 i3 i4 i5

In turn, it forces inverter circuit working in unbalance condition (carrying unequal current in every output phase).

5 phase inverterDC/AC

5 Phase Inverter – Unbalance Load

It causes current and voltage at capacitor terminal increase to a higher level which the magnitude

is a function of i1, i2, i3, i4, i5.

5 phase inverterDC/AC

If the capacitor specs does not account this influence, when the fault comes, component is about to produce excessive thermal stress, reduce its life time, or might be eventually burnt out

Research Objective

Therefore, it is important to analyze as well as minimize input current and voltage of the inverter (blue sign) under various circuit unbalance scenario, so optimal selection of capacitor design can be made.

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This is my research area

To design capacitor size anticipating worst fault condition

Research Progress

•Literature review from past 25 year transaction•Develop research methodology:Focus how to quantify parameter that is affecting capacitor performance: Input Current Ripple Root Mean Square

(RMS) Maximum Capacitor Bus Voltage Ripple

See probability that ripple can be reduced by harmonics injection to reference signal

5 Phase Inverter – Unbalance Load

• Literature ReviewThough many paper has been published in recent 25 years, however investigating inverter input current or voltage ripple under unbalance load is getting less attention.

In addition, only few works are available concentrating on multiphase inverter

Therefore synthesizing information to develop research methodology embark from ideal three phase circuit

5 Phase Inverter – Unbalance Load

• Literature ReviewTheory developed by Cross et. al (time domain approach) and McGrath et. al (frequency domain approach) show that input ripple current can be evaluated using Fourier series.Downside: 1. To solve Fourier equation precisely, infinite number

of harmonic order must be introduced. The calculation will be exhaustive unless mathematical analysis program is utilized.

2. This method would not be able identifying which optimal switching strategy to attenuate input current or voltage ripple magnitude

5 Phase Inverter – Unbalance Load

•Literature ReviewTheory developed by Dahono et. al dictated the input ripple current can be evaluated by avoiding Fourier infinite series. The ripple equation is presented in a simple math form.

Downside: The calculation, built upon assumption that the circuit is in a perfectly balance set, whereas in practical viewpoint this is not always the case.

5 Phase Inverter – Unbalance Load

•Literature ReviewApproach proposed by Pei et. al in 2014, suggest that input ripple current under unbalance circuit condition can be analyzed through a simple math expression.Downside: 1. Ripple minimization technique is not

discussed2. The calculation only developed in three

phase circuit

Literature Review SummaryDesired Criteria

Unbalancecircuit

Avoid Fourier Series

Ripple suppressiontechnique

Five phase circuit

Cross et. al V X X X

McGrath et. al V X X X

Dahono et. al X V V V

Pie et. al V V X X

Research Objective

V V V V

THANK YOU

CONTENT

•Quick overview on Five Phase Motor Drive Train

•What is my research tell about?•Objective of my research•Literature on Five Phase Inverter•Research Plan: Research Question How do I will contribute