Research on the Reliability of Uninterruptible Power Systemconfig.peac-conf.org/ckfinder/userfiles/files/P5.pdf · GJB/Z 299C-2006 Reliability prediction handbook for electronic equipment

Research on the Reliability of

Uninterruptible Power System

Chen SixiongChief Engineer

Xiamen Kehua Hengsheng Co.,Ltd.

IEEE PEAC 2018 No Reprint Without Authorization

Contents

Background

Topics on concept of reliability

Topics on UPS reliability

Reliability test and verification of Kehua

Brief introduction to Xiamen Kehua


Background

Reliability is very important for power electronics system.

Reliability is basic requirement for system to run in long

time under various complex environment conditions.

Standards MIL-HDBK-217 Reliability Prediction of Electronic Equipment.

GB/T 2900.13-2008/ IEC 60050(191):1990 Electro-technical terminology - Dependability

and quality of service.

GJB 450A-2004 General requirement for materiel reliability program.

GJB 813-1990 Reliability modeling and prediction.

GJB/Z 299C-2006 Reliability prediction handbook for electronic equipment.

IEEE 1413-2010 Standard framework for reliability prediction of hardware.

BS IEC 60605-6-2007 Equipment reliability testing - Part 6: Tests for the validity and

estimation of the constant failure rate and constant failure intensity.


Background

Most of the opinions in

this presentation are

included in “White Papers

of the UPS Technology for

Data Center”, issued by

the Information System

Power Supply Technical

Committee of CPSS.

The “White Papers of the UPS Technology for Data Center” was drafted by

the Information System Power Supply Technical Committee of CPSS, with the

participation of Chen Sixiong, Zhang Guangming, Xie Shaojun, He Chunhua and

other well-known experts. Professor Xu Dehong, chairman of CPSS, was invited

to make the preface.IEEE PEAC 2018 No Reprint Without Authorization

Basic Terms

Reliability：

Failure rate：

MTBF：

Availability：

0( ) exp( ( ) )

t

R t x dx

0

1 ( ) ( ) ( )( ) lim

( ) ( )t

F t t F t f tt

t R t R t

V

V

V

MTBFA

MTBF MTTR

0 0

1( ) exp( )MTBF R x dx x dx


Topics on concept of reliability

Topic 1: Is reliability a constant?

Topic 2: What is the difference between 99.999% and

99.9999% for reliability?

Topic 3: Reliability or availability?

Topic 4: Maximum N for N+X system


5 8760h

100,000(5 ) e 64.5%hR years

99.999%R

100 000hMTBF ,

Topic 1: Is reliability a constant?

Reliability is a exponentially decreasing function of time.

The reliability of system, we talking about, is actually the

reliability value in the 1st hour.

Reliability after 5 year

( ) exp( )t

R tMTBF

First Hour99.999%

5 Years64.5%


Uninterruptible

Power SystemReliability Failure Rate (λ)

Annual Failure

Rate (λ)

A 99.999% 1.0×10-05 h-1 8.76%/year

B 99.9999% 1.0×10-06 h-1 0.876%/year

Topic 2: What is the difference between

99.999% and 99.9999% for reliability?

It's hard for user to distinguish the reliability between

99.999% and 99.9999%.

But, we can easily know the difference between these 2

systems by Annual Failure Rate.



RELIABILITY(1) The duration or probability of failure-free performance under stated

conditions.

(2) The probability that an item can perform its intended function for a

specified interval under stated conditions.

AVAILABILITYA measure of the degree to which an item is in an operable and

committable state at the start of a mission when the mission is called

for at an unknown (random) time.

Source: MIL-HDBK-338B - MILITARY HANDBOOK, ELECTRONIC RELIABILITY DESIGN HANDBOOK



Difference

Basic Calculation Equation

Series & Parallel model Equation

Application


Basic Calculation Equation

Affected by MTBF Affected by MTBF and MTTR

AConstant

Function of Time

( ) exp( )t

R tMTBF

MTBF

AMTBF MTTR


Series & Parallel Model Equation

Source: Cao Jinhua, Cheng Kan. Introduction to reliability mathematics [M]. Beijing: Higher Education

Press, 2006:182-224.

Series Parallel

RELIABILITY

AVAILABILITY

Unit1 Unit2 UnitnIn Out

Unit1

Unit2In Out

Unitn

…

1

n

i

i

R R

1

1 (1 )n

i

i

R R

1

1

(1 )n

i

i i

MTTRA

MTBF

1

1

11 (1 ( ) )

!

nk

k

MTTRA

k MTBF


Application

Two different applications

“Reliability” → no failure should be allowed, or as less as

possible

For some case, any system failure will cause huge accident or

economic losses for customer, therefore no failure should be allowed.

Application Example: UPS application for data center

“Availability” → failure is allowed, but failure time should be as

short as possible

In some case, the economic losses is proportional to the time of

system failure, so the occurrence of failure should be avoided and

failure duration should be minimized as possible.

Application Example: PV Inverter applicationIEEE PEAC 2018 No Reprint Without Authorization

Topic 4: Maximum N for N+X system

Assuming the UPS reliability is 99.99936% (MTBF = 156000h):

For N+1 system, N ≤ 6, RUPS_(N+X) ≥ RUPS



The reliability of N+X system

The reliability of N+X system should be greater than one single system

_( )UPS N X UPSR R

_( )

0

= (1 )X

N k N k X k

UPS N X N X

k

R C R R


Topics on UPS reliability

Topic 5: How does UPS improve the reliability of power

supply for IT equipment?

Topic 6: UPS reliability prediction base on component

counts and FIT-Rates

Topic 7: UPS reliability analysis base on market failure

rates


Topic 5：How does UPS improve the

reliability of power supply for IT equipment?

Assume:

Then:

R = Rgrid×RUPS = 0.9996455 ≤ Rgrid ?

GridUPS

（RUPS）IT Load

Rgrid R

Rgrid=0.99965 RUPS=0.9999955




IT

LoadAC/DC

(Rrec)

DC/AC

(Rinv)

Battery

(Rbat)

R'UPS

Bypass

(Rbyp)

Rgrid

RGrid

(Rgrid)

Reliability model for UPS system




Tab. Typical Reliability Value

' 1 (1 ) (1 )UPS grid rec bat invR R R R R

'1 (1 ) (1 )

99.9998998%

grid UPS bypR R R R

Reliability Value

Rgrid 99.965%

RUPS 99.999%

Rrec , Rinv 99.99955%

Rbyp 99.9999%

Rbat 99.9999287%

R = 99.9998998% > Rgrid = 99.965%, RUPS = 99.999%


Topic 6: UPS reliability prediction base on

component counts and FIT-Rates

A high power UPS example

Environment

Temperature

Load Rate

20% 60% 100%

25°CFit 1949.899 2902.369 6650.3525

MTBF 512,847 344,546 150,368

40°CFit 2368.47 3694.585 8669.485

MTBF 422,213 270,666 115,347

60°CFit 3394.46 5848.105 14460.59

MTBF 294,598 170,996 69,153


Topic 7: UPS reliability analysis base on

market failure rates

For MTBF = 100,000h, λ = 8.76% per year, can not satisfy customers'

requirements.

If you want to achieve more than 90% reliability after 5 years, the annual

failure rate should be less than 2%.

According to the current level of UPS technology and product quality, for

high-quality products, the annual failure rate can reach 1%, the MTBF can

reach 876,000 hours.

Annual

Failure RateMTBF R1hour R1year R3years R5years

8.76% 100,000h 99.99900001% 91.61272543% 76.88956611% 64.53257829%

4.38% 200,000h 99.99950000% 95.71453674% 87.68669574% 80.33217182%

2% 438,000h 99.99977169% 98.01986733% 94.17645336% 90.48374180%

1% 876,000h 99.99988584% 99.00498337% 97.04455335% 95.12294245%


Reliability modeling

Reliability prediction

Reliability test and

verification

Reliabilityimprovement


The KEHUA reliability design process



Aging test platform for MW power products Simulates various working condition (high temperature operating life,

full load, unscheduled turn on/off, cycling loading test, AC source etc.)

long-term MTBF test



Environmental reliability test platform temperature test , humidity test

for MW power test

salt spray test, vibration test, etc.



Dust proof Laboratory Test level: IP6X



Water proof Laboratory Test level: IPX1, IPX2, IPX3, IPX4



EMC Laboratory R&S company (German) test system

10m Semi anechoic chamber, for MW power test

RE test, CE test, ESD test, SURGE test, EFT test and DIPS test, etc.


A brief introduction to

Xiamen KehuaIEEE PEAC 2018 No Reprint Without Authorization

2016 Built IDC in Beijing,

Shanghai and

Guangzhou

1997Started the

international brand

strategy

2014Awarded “National

Enterprise

Technology Center”

2015Firstly developed the

nuclear power plant

UPS in domestic

brand

2017Promoted national

cloud service

business

2010Officially went public

on Shenzhen Stock

Exchange (No.:

002335)

1988The predecessor of

Kehua Technology

was established in

Zhangzhou, China

1996Awarded “National

Key High-tech

Enterprise”

01 02 03 04 05 06 07 08

About us


Our Business

IDC Service

190km2 IDC

25,000 Racks

Build In Beijing,

Shanghai, Guangzhou

Critical Power

UPS: 0.5kW~1.6MW

Smart Energy

Management

Micro-grid

Renewable Energy

PV Inverter:

1kW~3.125MW

Energy Storage

EV Charging


Technology Innovation

900+R&D engineers

760+ Patents & Copyrights

60+National and Industrial

Standards


Thank you

for your attention

Xiamen Kehua Hengsheng Co.,Ltd. www.kehua.com.cnIEEE PEAC 2018 No Reprint Without Authorization

Documents

Research on the Reliability of Uninterruptible Power Systemconfig.peac-conf.org/ckfinder/userfiles/files/P5.pdf · GJB/Z 299C-2006 Reliability prediction handbook for electronic equipment