MiniGrid Stability and RE Integration: Technical Challenges

José A. Aguado, PhD

Professor, University of Malaga (Spain)

Grid Expert, Effergy Energía (jaguado@uma.es)

Asia Clean Energy Forum

Manila, 15-Jun-2015

effergy Energía

effergy Energía

Effergy is a Renewable Energy Consultancy company

created in 2009. Expertise lies mainly in the field of

renewables, with a wide and extensive international

experience in consultancy, research and capacity

building.

Effergy’s Minigrids Projects under ADB: Maldives, Sri

Lanka and Bangladesh

Agenda

Minigrids, Challenges, Solutions

Why

Minigrids?

RE

Integration Challenges

Available Solutions

• Ambitious RE targets have been set worldwide

• High RE penetrations results in technical challenges

for System Operators

• Minigrids are the ideal platform to start realizing

tomorrow’s energy technologies today.

Towards high RE penetration

Minigrids

effergy Energía

effergy Energía

Hybrid Minigrid Project Phases

Feasibility Study

Detailed Engineering

Installation & Comissioning

Operation & Optimization

effergy Energía

effergy Energía

effergy Energía

effergy Energía

• Each system has its own optimal RE penetration

rate. However, there is no technical limitation for

100% RE if we implement proper actions

Suppliers

effergy

Energía

Inherent volatility of renewable energy can compromise grid stability The renewable energy integration solution must address requirements traditionally fulfilled by diesel generation (base load)

• Sufficient spinning reserve • Sufficient active and reactive power supply • Peak shaving and load leveling • Load sharing between generators • Frequency and voltage control • Fault current provision

Renewable energy generation capacity should be sized to maximize ROI and fuel savings

Technical Challenges in Hybrid

Minigrids

Grid Stability Assessment effergy Energía

Variable RE (solar, wind,

etc.)

GR

ID S

TAB

ILIT

Y A

SSES

SMEN

T

Low penetration

<20%

Medium penetration

20-60%

High penetration >

60%

Low loading (aprox.30%)

Reduced efficiency

Reduced life span

Affects grid quality

Instability of grid

OK

Relatively simple control system

required

Sophisticated control system

required

Affects grid quality

Instability of grid

RE power limiting (inverters)

Installation of secondary diesel units

Short-term energy storage (flywheels, etc.)

Load shedding

Replacement of specialised low load diesel

Long-term energy storage

Load shedding

Demand-side management (smart metering, etc.)

RE power limiting (advanced inverters)

SMART MINIGRIDS

Source: NREL

effergy

Energía

Technical Challenges in Hybrid

Minigrids

Stability Region for Safe Operation

effergy

Energía

Technical Challenges in Hybrid

Minigrids

Input Data Minigrid Model Output Data

effergy

Energía

fdyn

fstat

Frequency nadir

f [Hz]t [sec]

Governor response AGC/manual frequency recovery

Technical risks:

• Secure Operation

• System Stability

• Power Quality

Technical Challenges in Hybrid

Minigrids

Primary Control: Droop control

Secondary Control: Power Plant

Controller.

Frequency Control Strategies effergy Energía

Available Technology for High RE

penetration

effergy Energía

• Energy Storage for Grid Support

• Active Control Power Balance of Variable

Resources

• More flexible Diesel GenSets

• Enhanced EMS: Improve Wind & Solar Forecasting

• Demand Response to handle RE

High Resolution Battery Cycling Simulation Tool effergy Energía

Case Study: Maldives effergy Energía

Case Study: Maldives effergy Energía

Island Data

Electricity Demand 1,230 MWh/yr

RE penetration 35%

Solar Power 300 kW

Wind Power 0 kW

Storage Power 223 kW

Diesel Power 254 kW

Case Study: Maldives effergy Energía

0.00 $/kWh

0.10 $/kWh

0.20 $/kWh

0.30 $/kWh

0.40 $/kWh

0.50 $/kWh

0.60 $/kWh

0.70 $/kWh

0 $

2,000,000 $

4,000,000 $

6,000,000 $

8,000,000 $

10,000,000 $

12,000,000 $

BASELINE NO RES NOBATTERY

NO BATTERIES(Max RES 15%)

OPTIMUM

NPC - LCOE

Total Net Present Cost

Levelized Cost Of Energy

Case Study: Maldives effergy Energía

0.0 Ton/yr

200.0 Ton/yr

400.0 Ton/yr

600.0 Ton/yr

800.0 Ton/yr

1,000.0 Ton/yr

1,200.0 Ton/yr

1,400.0 Ton/yr

1,600.0 Ton/yr

1,800.0 Ton/yr

0 kWh/yr

200,000 kWh/yr

400,000 kWh/yr

600,000 kWh/yr

800,000 kWh/yr

1,000,000 kWh/yr

1,200,000 kWh/yr

1,400,000 kWh/yr

BASELINE NO RES NOBATTERY

NOBATTERIES(Max RES

15%)

OPTIMUM

Electricity generation - CO2 Emissions

PV array

New Diesel

Diesel 2

Diesel 1

CO2 Emissions

Case Study: Maldives effergy Energía

0 L/yr

100,000 L/yr

200,000 L/yr

300,000 L/yr

400,000 L/yr

500,000 L/yr

600,000 L/yr

700,000 L/yr

BASELINE NO RES NOBATTERY

NO BATTERIES (MaxRES 15%)

OPTIMUM

Fossil fuel consumption

Battery Storage for Grid Support: Buruni effergy Energía

• Battery Performance

Example: Maldives-Buruni effergy Energía

• Battery Performance

Before After

P= 150 kW P= 150 kW

Q=112.5 kVAr Q= 112.5 kVAr

Irradiance=1000 W/m2 Irradiance=200 W/m2

Diesel 1 Switched on Diesel 1 Switched on

Diesel 2 Switched off Diesel 2 Switched off

Example: Maldives-Buruni effergy Energía

Example: Maldives-Buruni effergy Energía

Example: Maldives-Buruni effergy Energía

Final Remarks effergy Energía

High RE minigrids poses technical challenges that

have to be understood

Technology to install and operate minigrids with high

renewable energy contribution is now proven and

commercially available

Extensive simulations and experience are requiered

to optimize and engineer the systems using verified

models

José A. Aguado, PhD

effergy Energía

High RE penetration Minigrids,

Looking Ahead !

Grid Stability Assessment effergy Energía

20%

• Ok

60%

• Simple Controls

>60%

• Enhanced Controls