t-breaker, a modular solid state circuit breaker and

T-Breaker, A Modular Solid State Circuit Breaker and Energy Router for Dc Networks

Dr. Jin Wang and Dr. Baljit Riar

Yue Zhang | May 24th - 27th, 2021

C E N T E R F O R H I G H P E R F O R M A N C E P O W E R E L E C T R O N I C S

Outline

• Project objectives and progress• T-Breaker topology derivation• Operation modes and case study

– Fault current breaking– Active current limiting– Compensation operation


Project Objectives and Progress


4

Challenges in Dc Network Operation

DC distribution found in Aerospace, Shipboard, Data Centers, Charging Stations etc.

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Remaining challenges in dc networks towards wider adoption

Fast and smart fault protection

Power flow control, power quality improvement and stability enhancement


5

Compensation in Dc Distribution Systems

Custom Power Devices for ac distribution systems: Static Var Generators (SVG), D-STATCOM (Distribution Static Synchronous Compensator), APF (Active Power Filter), DVR (Dynamic Voltage Restorer)…

T-Breaker integrates fault management, power flow control, power quality and stability improvement in one easily expandable modular device for dc distribution systems.

What we need in dc distribution system:


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Project Objectives

Challenges and Innovations: Highly efficient and self-sustained bi-directional circuit building blocks Reliable operation (low nuisance trips rate) and fast fault detection Safe implementation of medium voltage high power SiC based circuits Ancillary circuit functions that enable resilient dc distribution systems

Two Planned Prototypes: 1-kV, 500-A

High current, for aircrafts and commercial building based applications 20-kV, 50-A, self-sustained

Medium voltage, for electric ship and utility scale dc microgrids


7

T-Type Modular Dc Circuit Breaker System Diagram

T-Breaker system is a fault protection and energy routing device with modular multilevel converter functions Basic building block: submodules with energy storage components Arm inductances:

Left and right arm inductance (LL and LR): line inductance or add-on reactor Vertical arm inductance (LM): add-on reactor.

Sensing feedbacks: Submodule voltages, bus voltages and arm currents

* N is the number of levels

SML1

LL LR

LM

VDC1 Load

KRSML(N-1)

VDC2

SMR(N-1) SMR1

(Self-Sustained) SM with a Single Power Module

Volt sensing

APS

Vertical arm

Horizontal arms: left and right arm

Voltage sensing

Current sensing

Residual current switch

SMM(N-1)

SMM1


8

1-kV Prototype Assembly

Horizontal arms submodule assembly

1 kV, 500 A nominal current, 5000 A absolute maximum breaking capability Estimated efficiency: 99.6%


9

Power Module Gate Drive and Protection

Master BoardMain power, I/O signal processing and voltage sensing

Slave BoardMain gate drive and protection circuits

(200 kV/µs signal CMTI)

1.6 µs total short circuit protection time

Vgs 10 V/div

Vds 100 V/div

Short circuit current1 kA/div

400 ns/div

The short circuit protection could effectively detect and turn off the power module within 1.6 µs.

300-V dc bus voltage, 5200-A submodule short circuit current.


10

Submodule Assembly and High Current Breaking

Fault Current2 kA/div

Vgs 10 V/div

Vds 100 V/div 4 µs/div

300-V submodule bus voltage, 5200-A network fault current.

Assembled horizontal arm submodule

Desat 2.5 V/div

Cable inductance and line reactance

GD overcurrent protection

Horizontal arm current sensing

Network fault current breaking


11

Preliminary System Test Results

System breaking test @ 500 V, 500 ANormal operation test @ 1 kV, 15 A


T-Breaker Topology Derivation


13

Traditional Solid State Circuit Breaker

Residual Current BreakerLine reactance

Bi-directional switch blocks

Challenges:

Bi-directional blocking switches are required (cost)

Synchronization between switching blocks (reliability)

Power source for gate driver circuits of the switches (self-sustaining capability)


14

Transforming the Solid State Circuit Breaker

Transforming the solid state breaker• Step 1: Rearrange semiconductor switches


Commercially available half bridge power modules can be utilized to achieve ultimate modularity and interoperability, e.g., the same power module can be utilized for both the propulsion inverter and the circuit breaker.


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Transforming the solid state breaker• Step 2: Solve the synchronization issue to improve reliability

By adding clamping capacitors, the Breaker becomes self-sustained by harvesting power from sub-module capacitors for gate drives and control circuits; becomes more reliable against mis-synchronization between power modules; can absorb the energy stored in line inductance;

For ancillary functions, the submodule capacitors can be made larger for more energy storage.

Residual

Current BreakerLine reactance


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Forming the T-Breaker (Patent Pending)• Step 3: Adding the vertical arm to enable sub-module voltage balance and unmatched potential for

ancillary functions.



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Flexible Submodule Topology Options

……


Flexible submodule configuration to realize different equivalent sources.


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Unmatched Potential for Ancillary Functions

Ancillary Functions

Series/Parallel compensation against voltage and power transients

Power flow regulation

Active current limiting during network fault and load transients

Network and fault impedance characterization


Operation Modes of T-Breaker


20

Fault Operation: Detection and Breaking


GD overcurrent protection

Horizontal arm current sensing

Gate drive + digital smart time-current curve


Fault energy absorption

Submodule capacitors absorb fault energy

Typical fault current profile (development + breaking)

Gate drive + digital line current monitoring


21

Fault Operation: Active Fault Current Limiting

Fault Current Limiter (FCL) is a necessary part of dc distribution system to reduce the fault energy to the load and cables, as well as limit the inrush current during system start-up and load transients.

Passive limiting: usually an inductor

Active limiting:

Active switching to insert additional voltage into the line to limit current development

Operate semiconductor devices in saturation region to clamp the fault current

Total line inductance

Adjustable resistance and injection voltage

Inrush or fault current


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Active Current Limiting through Voltage Insertion + Breaking (Cont’d)

3 5 8 10

Current Limiting (X)

0

20

40

60

80

100

I2t E

nerg

y

20 H

50 H

100 H

3 4 5 6 7 8 9 10

Current Limiting (X)

50

60

70

80

90

Max

imum

Tj (

C)

20 H

50 H

100 H

1-kV system, 100-A nominal current 500-V injected to the line during current limiting 10 X maximum breaking current

Line Current

Ilim

Break at 10Xno limiting

Limit, confirm, and break Break at 10Xno limiting

Limit, confirm, and break

LL LRCable inductance and line reactance

Reduced I2t energy and max device junction temperature.


23

Active Current Limiting through Semiconductor Saturation

LL LRCable inductance and line reactance

Operate switch in saturation region

Gate Voltage

Power Dissipation

On resistance

Junction Temperature (ºC)

Load Current

Vgs = 20 V Vgs = 8 V

660°C540°C420°C300°C180°C

60°C

Reduced power dissipation

Fault current clamped at 360 A

Reduced junction temp.

Combine active switching and active gate clamping


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T-Breaker Compensation Operation

10% source voltage sag leads to instability T-Breaker improves stability through shunt compensation

T-Breaker helps the ride through of voltage and power transients, improves power quality and system stability region, and achieves power flow regulation through series and shunt compensation.

Case study: grid instability introduced by constant power loads (CPLs)

CPLs introduce stability concerns during a voltage sag, or a sudden load power change

Shunt compensation enabled during the voltage sag

Compensation current


25

T-Breaker Compensation Operation

Region of Attraction (ROA) analysis with Lyapunov function shows improved stability region with much smaller load side dc bus capacitance

T-Breaker helps the ride through of voltage and power transients, improves power quality and system stability region, and achieves power flow regulation through series and shunt compensation.

Case study: grid instability introduced by constant power loads (CPLs)

CPLs introduce stability concerns during a voltage sag, or a sudden load power change

Shunt compensation enabled during the voltage sag

Compensation current


Conclusion and Future Work

T-Breaker could be promising all-in-one device candidate for:

Fault current limiting and breaking

Power flow control

Power quality improvement

Stability improvement

The modular multilevel structure is friendly towards system scaling

1 kV, 500 A and 20 kV, 50 A system under testing and development

1 kV, 500 A prototype


Thank you!Questions?

For further information, please contact: Mr. Yue Zhang [email protected]

Dr. Jin Wang [email protected]

t-breaker, a modular solid state circuit breaker and

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