Advantages and Circuit Configuration of a DC …microgrid-symposiums.org/wp-content/uploads/2014/12/montreal_ise.pdf · Advantages and Circuit Configuration of a DC Microgrid

Montreal 2006 – Symposium on MicrogridsJune 23, 06 CanadaRessources naturelles

CanadaNatural ResourcesCanada

Advantages and Circuit Configuration of a DC Microgrid

Toshifumi ISE（Osaka University, JAPAN）

[email protected]

PE&EESince 2002

2Montreal 2006 – Symposium on MicrogridsJune 23, 06 CanadaRessources naturelles


Problems on Microgrids

1)Synchronization of distributed generators

2)Inrush current

(transformers, Induction motors, Induction generators)

3) Three-Phase Unbalance

(single-phase loads, single-phase generators such as photovoltaic)



Recent Trends

1) Introduction of many Inverter loads(AC/DC and DC/AC conversions are included)

2) Introduction of distributed generations with DC output (photovoltaic, fuel cell, variable speed type wind turbine, micro turbine, gas engine)

3) Needs for higher quality power



DC Loop Type Configuration

PFC

DCDC PV　Cell

DCDC PV　Cell

DCAC

Load

DCDC SMES

DCAC

G Wind Turbine

MT Micro Turbine

DCDC

FC Fuel Cell

DCDC

Secondary Battery

DCAC

Load

DCAC

Load

4kV

2kV

2kV

PFC Normal QualityLoop

High QualityLoop

22kV/1.2kV

22kV/1.5kV

Bi-directional Rectifier

Diode Rectifier

22kV/1.2kV

22kV/1.5kV

SFCL + Hybrid Switch

PFC

DCDC PV　Cell

DCDC PV　Cell

DCAC

Load

DCDC SMES

DCAC

GG Wind Turbine

MTMT Micro Turbine

DCDC

FCFC Fuel Cell

DCDC

Secondary Battery

DCAC

Load

DCAC

Load

4kV

2kV

2kV

PFC Normal QualityLoop

High QualityLoop

22kV/1.2kV

22kV/1.5kV


Diode Rectifier

22kV/1.2kV

22kV/1.5kV

SFCL + Hybrid Switch



Circuits for Loss Comparison

DC Loop System

AC Radial System

2 k V

D CA C L o a d 1

1 k m

0 .5 k m

0 .5 k m

1 k m

1 k m

D CA C

D CA C L o a d 2

D CA C L o a d 3

2 k V

D CA C L o a d 1

1 k m

0 .5 k m

0 .5 k m

1 k m

1 k m

D CA C

D CA C L o a d 2

D CA C L o a d 3

1km

0.5km

0.5km

6.6kV

A C

D CA C L oad1

D CA C

D CA C L oad2

D C

D CA C L oad3

D CA C

1km

0.5km

0.5km

6.6kV

A C

D CA C L oad1

D CA C

D CA C L oad2

D C

D CA C L oad3

D CA C

A C

D CA C L oad1

D CA C

D CA C L oad2

D C

D CA C L oad3

D CA C

20MW

20MW

20MW

20MW

20MW

20MW



Reduction of Rectifier Losses

0

2

4

6

8

10

12

0.95 0.96 0.97 0.98 0.99 1

Rectifier Efficiency of DC Loop Type Distribution System

Loss　

[MW]

A C Type Distribution System DC Loop Type Distribution System



Distance of Cable and Losses

0

2

4

6

8

10

12

14

16

0.5 1 1.5 2 2.5

D istance of C able　[km ]

Loss　

[MW]

A C Type D istribution System D C Loop Type D istribution System



Loss Reduction due to Loop System

0

2

4

6

8

10

12

14

DC Loop Type DistributionSystem

DC Type Distribution System(W ithout Loop)

Loss　[MW]

Losses of Inverters and Rectifier Losses of C able



Loss Reduction by Feeding from Two AC Systems

0

2

4

6

8

10

12

0 10 20 30 40

Power of Load1　[M W ]

Loss　[MW]

O ne AC System Two AC System s



Control Method of Rectifiers Using Gain-Scheduling Method


dcV*

dcV

P

*i

Voltage Control

K

AC system

LPFP

K

Gain Scheduling

iP

V

P1K

2K

1 2K K>

K*i

dcV

*dcV +

−

Controlled Characteristics with Proportional Controller



Effect of Gain Scheduling

V

P 1K

2K

1 2K K>

Voltage regulation

Power sharing

Large Gain KSmall Gain K

Gain Scheduling

Voltage Regulation Power SharingExcellent Fair

Fair ExcellentGoodGood



Control of Multiple Rectifiers

AC system 1AC system 1

AC system 2AC system 2


1d cV*

d cV

1P

*i

Voltage Control

K

LPFP

K

1i1P

Gain Scheduling

2P

2d cV

*d cVK

2P*i2i

Communication line



10%Load 50%Load 100%LoadVoltage

Gain K0 2 4 6 8 10

0.88

0.86

0.9

0.92

0.94

0.96

0.98

1.0

Gain K

Load power

0

2

4

6

8

10

0 0.2 0.4 0.6 0.8 1.0

voltage variation 2%

voltage variation 6%

Gain K versus DC Voltage Characteristics

Gain K for Various Load Power with 2% Voltage Variation



Simulation Circuit

sL sR

22 /1.2kV kV 400kW(Max) 300kW(Max)

300kW(Max)

3dcR 1dcR

2dcR

1km

1km

1km

0.5km 0.5km

Cd

1dcV

2dcV

+-

+-

Bi-directional

rectifier

Rectifier power1

Rectifier power2

AC system1

AC system2



Simulation Results of Power Sharing

DC Voltage (kV)

+0.8+0.6+0.4+0.2+0

+1.8

+1.9+2

0.3 0.5 0.7 0.9 1.1 1.3

0.3 0.5 0.7 0.9 1.1 1.3

8％

Power Sharing (MVA)10% 50% 100

%

Load PowerLoad Power100%

Time(s)

Load Power (MW)+0.4+0.3+0.2+0.1+0

+0.5

Load Power

0.3 0.5 0.7 0.9 1.1 1.3

Constant Gain

K=2

DC Voltage (kV)

Power Sharing (MVA)

Load Power (MW)

+0.8+0.6+0.4+0.2+0

+1.8

+1.9

+2

+0.4+0.3+0.2+0.1+0

+0.5

Time(s)0.3 0.5 0.7 0.9 1.1 1.3

0.3 0.5 0.7 0.9 1.1 1.3

0.3 0.5 0.7 0.9 1.1 1.3

1％

Constant Gain

K=30

DC Voltage (kV)

Gain

Power Sharing (MW)

Common Gain

Time(s)

10% 50% 100%

Load Power (MW)

+0.8+0.6+0.4+0.2+0

+1.8

+1.9

+2

+0+10+20+30

+0.4+0.3+0.2+0.1+0

+0.5

0.3 0.5 0.7 0.9 1.1 1.3

0.3 0.5 0.7 0.9 1.1 1.3

0.3 0.5 0.7 0.9 1.1 1.3

0.3 0.5 0.7 0.9 1.1 1.3

Load Power Load PowerLoad Power

2％

Gain-schedulingsystem1 system2 Load1 Load2 Load3

Power Ratio

54:46

Power Ratio

51:49

Power Ratio

57:43



DCAC

Load2

PFC

22kV/1.5kV

Ls Rs

Cd

PFC

22kV/1.5kV

Ls Rs

Cd

LCフィルタ

Cd2

Cd1 Load1

Cd3 Load3

1km

1km

1km

0.25km

0.5km

DCDC

Ldci

DCDC

Ldci

0.25km

短絡事故短絡事故

SFCL SFCL

SFCL SFCL太陽光発電太陽光発電

二次電池1二次電池1

二次電池2二次電池2

交流システム1交流システム1

交流システム2交流システム2

負荷1負荷1

負荷2負荷2

負荷3負荷3

HS11HS12

HS21HS22

IS1S2

IS1L1

IS2L3

IL1L2

IL2L3

ハイブリッドスイッチ1




DCAC

Load2

PFC

22kV/1.5kV

Ls Rs

Cd

PFC

22kV/1.5kV

Ls Rs

Cd

LC Filter

Cd2

Cd1 Load1

Cd3 Load3

1km

1km

1km

0.25km

0.5km

DCDC

Ldci

DCDC

Ldci

0.25km

短絡事故Fault Point

SFCL SFCL

SFCL SFCL太陽光発電Solar Battery

二次電池1Battery 1

二次電池2Battery 2

交流システム1AC System 1

交流システム2AC System 2

負荷1Load1

負荷2Load2

負荷3Load3

HS11HS12

HS21HS22

IS1S2

IS1L1

IS2L3

IL1L2

IL2L3


HybridSwitch 1


HybridSwitch 2

Simulation Circuit for Protecting Operation



Current Through the Mechanical Switch

Current Through the Semiconductor Switch

Simulation of Protecting Operation

1ms 1ms



Bulk Power system

Low Voltage Type DC Microgrid

DCDC

ACDC

G

Secondary Battery

Electric Double Layer Capacitor

Co-generator

DCDC

DCDC


Photovoltaic Cell

Communication Line

AC 200 V

AC100VDC 170 VDC 170 V

3φ AC200 V

1φ AC100 V

DC 100 V

Islanding Protector

DC

DC Fuel CellCenter Building

Rectifier

1φ AC100 V

1φ AC100 V

AC100V

AC100V

Power Exchange

Power Exchange



Features of Low Voltage Type DC Microgrid

Distributed scheme of load side converters contributes to provide a super high quality power supplying. Various forms of electric power like single phase 100V, three phase 200V, DC 100V can be obtained without using transformers. If power consumption become more than a power production during a long term isolation, DC micro-grid can stop supplying power for some loads intentionally by load side converters in order to continue supplying power for more important loads.When a temporary overload occurs at one load, electric power can be shared by using additional electric power lines between load side converters.



Features of DC Microgrid

Synchronization of distributed generators are not necessary.

Fluctuation of generated power of distributed generators and load power can be compensated in the dc line by using energy storage devices.

Loads are not affected by voltage sag, voltage swell, three-phase voltage unbalance, and voltage harmonics.

Power quality is not affected by Inrush current, single-phase loads and single-phase generators.

Higher efficiency than AC microgrid is expected.

Documents

Advantages and Circuit Configuration of a DC …microgrid-symposiums.org/wp-content/uploads/2014/12/montreal_ise.pdf · Advantages and Circuit Configuration of a DC Microgrid