P200D/Microgrid Protection

INTRODUCTION

Literature Review

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SYNCHRONOUS GENERATORS AND CONDENSERS

Generator Protection

unbalance

No need to explain voltage or frequency protection except to say how it has to be configured to meet IEEE1547 ride-through requirements when grid-connected.

Modeling in Commercial Software Tools

Link to page on modeling DER for protection studies

INVERTERS – SOLAR PV, WIN TURBINE GENERATORS, BATTERY ENERGY STORAGE

Introduction

Sean to provide

Grid-Following Inverters

Sean to provide

Grid-Forming Inverters

Sean to provide

Short circuit current characteristics

Link to material from Guide to modeling DER for protection studies

Modeling in Commercial Software Tools

Copy material from Guide to modeling DER for protection studies. Only the screengrabs from

MICROGRID PROTECTION STRATEGIES

Defining reliability requirements

Defining reliability needs:

1. Are there any critical loads
2. How often microgrid is operated (weekly vs maybe once every year or two)
3. Probability of fault during microgrid operation (more likely during storm?)
4. Charateristics of feeder route – short urban feeders relatively low risk vs long feeders on exposed parts of mountains higher risk
5. Ride-through capability

Short Circuit Fault Protection Strategies

Synchronous Condensers

Can provide short circuit current, but at additional capital and O&M costs. Can be designed to provide 10-20pu fault current. Much higher than the 5-7pu typical of synchronous generators. Run it “always on” and let it provide source of reactive power Run it only during microgrid. Need to incorporate it into microgrid startup sequence

Under-frequency Load Shedding

If microgrid has multiple DER and is expected to run for extended periods of time then UFLS may be beneficial.

Under-voltage Load Shedding

If there are a lack of cap banks and/or DER have insufficient reactive power capabilities under certain operating conditions (peak load etc), then UVLS might be used. The load it trips has to be large enough to stabilize the grid though, so more likely to be used for larger microgrids.

Microgrid Neutral Grounding

IEEE and IEC Standards IEEE, CIRED papers

IEEE1547.8 IEEE PSRC protection of microgrids WG

Protective action if grounding transformer disconnected (fuse blows etc)  

GRID PROTECTION WHILE TRANSITIONING BETWEEN GRID-CONNECTED AND MICROGRID OPERATING MODES

De-Synchronizing

Seamless transition to microgrid vs blackout and blackstart

Blackstarting

Hard vs soft energization. Hard = switch each feeder/load in one by one.Soft = energize everything in one go by ramping voltage from 0 to 1pu over a few seconds (inverters) or few minutes (synchronous generators)

Effective Grounding

Clo

Load Unbalance

Battery Energy Storage Inverters can support extreme unbalance in three-phase load.

• String inverters
• Three single phase inverters
• Three-phase inverter

Near 100% unbalance supported by some products

Protection

• Impact on negative and zero sequence feeder protection
• Impact on three-phase motor protection; thermal protection, unbalance protection
• Impact on synchronous generators and condensers; negative sequence protection; unbalance protection

 

 

CASE STUDIES AND WORKED EXAMPLES

Case study #1 – Residential Microgrid

EPRI member or conference/journal paper

Case study #2 – Industrial Microgrid

EPRI member or conference/journal paper

Worked Example #1 – Residential Microgrid 100 % inverter

Example of relatively small microgrid 350-500 kW in size. Primarily battery

Worked Example #2 – Industrial Microgrid 100% Synchronous Generator

Example of larger microgrid 2-5 MW in size with rotating generators

Worked Example #3 – Industrial Microgrid Mixed Synchronous Generator and Inverter-Interfaced Energy Sources

Example of larger microgrid 2-5 MW in size with battery, solar PV

 

CONCLUSIONS AND FUTURE WORK

Strategies