Switch Mode Battery Chargers for Utilities:

Why? How? and Where? Haissam Nasrat

Yves Lavoie, Steven Monk

Primax Technologies Inc.

Montreal, Quebec, Canada. 1

Schedule: History DC System Review SCR Type Battery Chargers SMR Type Battery Chargers Physical and Environmental Considerations Service and Repair Considerations

2

52

52

N

50/51

87GD50/51

Protection Relay

50/51

50/51

86

27-59

27-59

AC source

Typical MV switchgear diagram

3

Common Topologies

Ferroresonant Magnetic Amplifier (Mag-Amp) Thyristor (SCR) High Frequency switching (Switchmode)

4

SCR Chargers Electrical Layout

240V-1PH60HZ-10kA

AC BREAKER DC BREAKERBLOCKING DIODE

Surgeprotection

Filter Inductor

Filter Capacitor

DC OutputEx. 136V-50A

5

SCR CHARGERS SPECIFICS: - Single conversion stage - Low frequency operation: larger

components - Need filters for Power factor and THDi

correction

6

Switchmode Chargers Electrical Layout

RECTIFIER

AC

CHOPPER RECTIFIERPFC

400VDC

240Vac-1ph OUTPUT132VDC

7

SMR SPECIFICS: High frequency -> smaller components Compact design -> cooling fans if not: larger

footprint 4 conversion stages 1ph units include PFC and THDi 3ph-3wire units: may or may not include PFC

and THDi. Complex designs 3ph-4wire units: easier to design More power -> multiple parallel units 19’’ rack design

8

5kVA transformers: SCR vs SMR 9

125VDC-30A SCR vs SMR

5U 8 ¾ in.

24 in.

21 in.

3.5 in.

10

125VDC-200A 19’’ subrack 17 ½ in.

5U 8 ¾ in.

11

BATT.

Module 2

Module 1

240V LN1ph

60Hz

CONTROLLER

N+X

DC OUT

Module X

REDUNDANT SCHEME N+X 12

Physical & environmental considerations

COMPONENTS SCR -Larger power -> larger components

SMR Smaller components -> compact design/PCB mount PCB mount -> modular designs

13

Mounting SCR: Wall mount or freestanding

enclosures

SMR: 19’’ racks or wall mount enclosures

Physical & environmental considerations 14

Service and repair: Factors to consider

SCR: One component failure: charger is down Need of skilled technician The failure becomes urgent Need of shutting down and disconnecting

the charger

15

SMR:

One system is made of multiple parallel units One unit failure: reduced power If N+1 is implemented: no impact Repair can be made by less specialized tech to swap

the unit No need to shut down the DC system Unit can be sent back to manufacturer for repair Failure of SMR -> non urgent event

Service and repair: Factors to consider 16

0 100 200 300 400 500 600 700 800 900 1000

$

Adc

SMR

SCR

Cost of single SCR vs «N» SMR 17

Cost redundant SCR vs N+1 SMR 0 100 200 300 400 500 600 700 800 900 1000

$

Adc

SMPS

SCR

18

Comments on Costs

•Low power SCR charger is slightly more expensive than SMR •High power 3 phase SCR cost become less expensive than SMR •SCR curve flattens out in larger applications •SMR curve is quite linear

19

Specifics to substation apps. 20

Ground plane impedance

Leakagecapacitance

Leakagecapacitance

LV cables

10ms2-5kV

HV busses

Generation

Power house/Substation

ChargersRelays LV loads

Specifics to substation apps.

• Chargers are installed dirctly under HV and high current busses • MV Capacitor banks & inductive loads switching • Transients as high as 5kV occur regularly • Electrical rooms are not as clean as telecom central offices: more dust and less A/C

21

SMR Present experience

- Telecom: for over 30 years they are the prevailing option - Europe and Australia, electrical utilities - over 15 years. - Some of these utilities exclusively specify SMRs - Canada: Large utilities started using SMR

22

SMR Present experience

US and the Canadian industrial markets: • New gas turbine applications

• Prefab Electrical Houses for industrial applications such as mining, petrochemical and smelting

23

What’s right for me?

No simple answer

Different applications dictate different technologies

24

What’s right for me?

Criterion SCR SMR Scalable No Yes Efficiency Good Better Power management No Yes Input power factor Relatively poor Very good Low ripple good better DC Capacitors aging Little effect Some effect Single point of failure Yes No Serviceability easy Very easy System Reliability Very good Very good Repair time Good Better Phase unbalance & neutral currents no effect some effect

25

What’s right for me?

Criterion SCR SMR Scalable No Yes Efficiency Good Better Power management No Yes Input power factor Relatively poor Very good Low ripple good better DC Capacitors aging Little effect Some effect Single point of failure Yes No

Serviceability easy Very easy System Reliability Very good Very good Repair time Good Better Phase unbalance & neutral currents no effect some effect

26

What’s right for me?

Criterion SCR SMR Dynamic regulation Good Excellent Transients Tolerant Sensitive Contribution into downstream Fault Good limited

Weight Heavy light Size Large Small Heat tolerance Good Limited Dust tolerance Good Limited Natural convection cooling Yes Limited Spare parts Individual parts modules

27

Conclusion

Can we deploy the SMR on a larger scale for substations and power generation?

Most probably yes.

But not everywhere!

28

Thank You!

29