iVSG— A Virtual Synchronous Generator realizing
the maximum use of renewable energy

April 1, 2024
Kawasaki Heavy Industries, Ltd.

Contents(1) Introduction(2) Features and Benefits(3) Applications(4) System Integration(5) Partnership Scheme(6) Summary© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 2024

1

Introduction

BackgroundThe number of blackout cases is increasing:
The power system is destabilized due to the massive deployment of renewable energy.

2020 California

2016 Australia
In South Australia, severe storms
caused a cascade of renewable
power plant outages, leading tostatewide power outages.

In California, it is required under
the RPS law to increase the ratioof renewable energy source inelectricity sales to 60% by 2030.
However, gas power generation
couldn't keep up with the tightelectricity demand during thesummer, which caused massive
power outages.
Source： https://ieei.or.jp/2020/09/yamamotoblog200914/

Source: 2016 Reuters/David Mariuz© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 20242

Introduction

Case Study : 2016 Australia caseWhy did the blackout happen after a large-scale introduction of renewable energy?
 Synchronous generators, such as thermal power plant, possess
inertia and play an important role in stabilizing the power system.
 Since renewable energy sources, such as solar power
generators, are inertialess, power system stability is getting lower.
Unstable Power System
Power outage occurs at the thermal power plant.
SHUT
DOWN

The grid frequency drops.
Inertial
Power system inertia is insufficient.

Inertialess

The grid frequency drops further.

To promote a large-scale introduction of renewable energy,
there is a need to address the lack of inertia.
© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 20243

Features and Benefits

What is iVSG ?
VSG: Virtual Synchronous Generator
iVSG

is the trademark of Kawasaki Heavy Industries, Ltd.

 iVSG is control software for inverter with energy storage, simulating behaviorof an engine generator.
 iVSG enables maximum utilization of renewable energy, realizing flexible andeconomical operation of microgrid with energy storage and engine generator.
 KHI(Kawasaki Heavy Industries) is licensing iVSG software.
Governor

AVR

AVR

Governor

Demand(Software)

Enginegenerator set
EngineGenerator

RenewableenergyMicrogrid

Energy StorageiVSG© Kawasaki Heavy Industries, Ltd. All Rights Reserved

InverterLarge-scale grid

April 1, 2024

4

Features and Benefits

Comparison with Conventional Technologies
 iVSG✓ Grid forming✓ Droop (autonomous load sharing)✓ Inertia (stabilizing grid)✓ Parallel with a large-scale grid(*) or gensets(*) Compliant to grid code of Japan
 UPS✓ Grid forming× No droop
× No inertia
× No ability to connect to a large-scale grid norother UPS Grid following inverter× No grid forming(No ability to maintain frequency or voltage)✓ :merits

UPS
Cannot connect
UPS

Cannot connect
Grid following
inverterIf fails ....

Then trips

× :demerits© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 20245

Features and Benefits

Features of iVSG
Features(1) Grid forming(2) Droop control(3) Simulated inertia(4) Charge and discharge

Benefits(a) Minimal use of engine(b) Autonomous load sharing(c) Improving grid stability

Frequency

Frequency
Droop

Droop
Active Power
Governor

Active Power
AVR

AVR

Governor

Demand(Software)

Enginegenerator set
EngineGenerator

RenewableenergyMicrogrid

Energy StorageiVSG© Kawasaki Heavy Industries, Ltd. All Rights Reserved

InverterLarge-scale grid
April 1, 2024

6

Features and Benefits

Flexible Grid Operations
 iVSG

enables flexible microgrid operation without blackouts.
Isolated grid (Daytime)

Connected to large-scale grid

Microgrid

Microgrid

Microgrid

Microgrid

Charge / Discharge

Discharge

ChargeIsolated grid (Night)© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 2024

7

Features and Benefits

Maintaining Redundancy
 Multiple generators must be in operation to maintain redundancy.
 Partial load operation causes low efficiency.

Low efficiency
In Operation

 iVSG
 iVSG

Low efficiency
In Operation

maintains redundancy even in single generator operation.
improves efficiency by using generators at higher load.
Engine failure
PowerPower supply continues

In
Stop
Operation© Kawasaki Heavy Industries, Ltd. All Rights Reserved

Ready for
Operation

EngineBattery

Spare engine
Cold start of spare engine

April 1, 2024

8

Features and Benefits

Reduction of Fuel Consumption
 A microgrid with a grid following inverter requires the engine to run all thetime.
 At a microgrid with iVSG , the engine can be operated intermittently to avoid
low efficiency operation.
Low efficiency

Grid following
inverterMicrogridHigh efficiency

Grid following
inverter

Discharge

Microgrid

ChargeHigh efficiency

Stop

Microgrid

Discharge© Kawasaki Heavy Industries, Ltd. All Rights Reserved

Microgrid

ChargeApril 1, 2024

9

Features and Benefits

Grid Stabilization
 Evaluation of the fluctuation of power system frequency when the load has stepchange by simulation.

Synchronous
generator
Synchronouswith diesel engine
Generator
Rated power: 1MW

INV

Load

InverterInverterRated power: 1MW

0.5MW -> 1MW

Comparing(1) Grid following (constant power)(2) Droop control (no inertia)(3) iVSG© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 2024

10

Features and Benefits

Grid Stabilization
Grid following(Constant power)
Load sharing withgenerator

×

Maintain frequency
during transient loadchanges×

Frequency (Hz)61

Droop control

iVSG

Load sharing by droop

Load sharing by droop

×

Maintain Frequency
by Inertia

Reduced frequency dropby droop control

VSG (green)

60
59

Improved RoCoF
58(Rate of changeof frequency)
by inertia

Current control droop (blue)

57
0.5

1

1.5
Time (s)Constant Power(purple)2

2.5

Step change of load
© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 202411

Applications

Applications of iVSG
Remote Island / Resilience
iVSG provides inertia to micro-grid.
Power companies can increase the introduction ofrenewable energy and reduce fuel cost.

MarineiVSG backs up power supply at engine failure.
Both efficiency and redundancy can be improved
at single generator operation.
Engine failure

Power supply continues

PowerIntermitted
operation

Microgrid
Providesinertia

Fast Adjustment

EngineSpare engine

Battery

Cold start of spare engine

Improving Power Quality

If a thermal power plant cannot be shut down due to theneed for fast demand/supply adjustment despite low
demand at night, iVSG energy storage system can beused instead.

Even if the renewable energy power generationequipment itself does not have sufficient stability, iVSG
can form a stable grid.

Unstable

100MW thermal power plant has
only a few MW adjustment ability.
© Kawasaki Heavy Industries, Ltd. All Rights Reserved

Geothermal power plant
A few MW VSG storageetc.
system can be used instead.
April 1, 2024

Stable grid12

Applications(1) Remote Islands / Resilience
Application•

Remote island grid systems that are not connected to power systems on the mainland

Benefits••

Promotion of introduction of renewable energy
Improving the stability of a self-sustaining system
Inertia
Supply and demand adjustment• In remote islands and other areas, fuel costs are
expensive. There is a high need to introduce solar,
wind and other renewable power.
• On the other hand, the weak grid limits the amount of
renewable power that can be introduced.
• iVSG provides the inertia, synchronization, andsupply-and-demand adjustment capabilities lacking ina small, self-supporting system.

MicrogridDisturbance• iVSG can increase the installed amount of renewable
power, while reducing the number of operating thermal
power plant. It enables more efficient system
operation.

DisturbanceSolar power

Power
DemandWind power© Kawasaki Heavy Industries, Ltd. All Rights Reserved

Inertia
Supply and demand adjustment

Grid stabilization
Implovement of efficiency
April 1, 202413

Applications(1) Remote Islands / Resilience
Application•

Emergency power supply in case of a major power outage by public facilities used as
shelters, such as gymnasiums and community halls

Benefits••

Use of solar power during power outages
Reduction of fuel consumption by keeping the generator operation to the minimum necessary

Maintains self-substanging grid
Public facilities
self-sustainingysystem(Supply and demand adjustment)• Solar power generation can only work in a gridconnected operation and can not used in the event of
a commercial grid power outage. So, the solor power
is not available at the power outage.
• Storage batteries are becoming more popular inhouseholds. But there are restrictions such as
temporary power outages when switching between
grid connection mode and self-substaining operation
mode.

Load

• iVSG has the ability to maintain an isolated grid
to operate seamlessly according to the state of grid.

Solar power

Diesel generator(Operate only when necessary)© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 2024

14

Applications(2) Marine
Application•

Hyblid propulsion system for vessel

Benefits••

Switching operation without blackout
Minimizing the number of operating engines

Onboard power
supply system
Land
power

Operated with minimal
number of engines

Inboardload• Hybrid propulsion systems are becoming popular,
which combine multiple power supply facilities withdifferent characteristics and switch equipment
configurations depending on the situation.
• iVSG has the same characteristics as generators, so
adding iVSG to a hybrid system provides a more
flexible and efficient power configuration.
• Also, iVSG backs up power supply at engine failure.
Even at single generator operation, both efficiency andredundancy can be improved.
Engine failure
PowerElectric
propulsion

Power supply continues

EngineGenerator backup© Kawasaki Heavy Industries, Ltd. All Rights ReservedSpareengineBattery

Cold start of spare engine

April 1, 202415

Applications(3) Fast Supply/Demand Adjustment
Application•

Power supply and demand adjustment

Benefits••

Improvement of grid stability (Even if thermal power plants are shut down at night)
Use as an alternative to pumped storage power plants

Commercial
Lineage• Only thermal power plants have the capacity to adjust supply
and demand, so when the number of operating thermal power
plants decreases, the capacity to adjust load decreases.
• To maintain a certain level of supply and demand adjustment
capacity even at night when electricity demand decreases, acertain amount of thermal power plants need to be operated.

Thermal power plant(Night-time stop)

Instead of thermal power
plants, securing supply
and demand adjustment
capability© Kawasaki Heavy Industries, Ltd. All Rights Reserved• If a thermal power plant is accompanied by iVSG , grid stability
is maintained even if the thermal power plant is shut down atnight because iVSG wil adjust supply and demand. iVSG
improves efficiency to reduse surplus operation of thermal
power plants at night.
• The supply and demand adjustment capacity of thermal power
plants is a few percent of the rated capacity. For example, thesupply and demand capacity of a 100MW thermal power plant isthought to be only a few megawatts, which can be sufficiently
achieved by iVSG storage facilities.
• Additionally, it also provides an allowance for lowering power,
making it a substitude for pumped storage power plants.
April 1, 2024

16

Applications(4) Improving Power Quality
Application•

System with power generation facilities that alone are difficult to improve power quality

Benefits•

Stabilizing power quality

Binary turbine(Geothermal power
plant)Grid• This is an example of the use of iVSG in
response to a request to install binary turbinesof geothermal power plant on remote islands
with heat sources.

商用電源系統6,600V , 60Hz , 3φ

バイナリー発電設備
バイナリータービン

Improvingpower quality

発電機

発電機側
電力変換装置• We planned to add power storage with a
DC/DC converter to a binary turbine and use
iVSG as the power converter on the grid side.

Load

直流リンク部
系統側
電力変換装置
250kVA

系統負荷

DC/DC
コンバータ

AC/DC
DC/DC

• Even if the binary turbine itself does nothave sufficient stability, iVSG can form astable grid.

系統負荷
二次電池
200kWh• The system simultaneously realizes thedemand on grid side, control of the rotation
speed of the binary turbine, and control of thecharge and discharge of the storage battery.

D/G
原動機発電機（ディーゼル発電機）

150kW

Other generators

D/G*Japan Patent 6371603(joint application with Kyushu Electric Power Co., Inc.)

150kW© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 2024

17

System Integration

Implementation of Software
 KHI licenses software design document or source code of iVSG logic.
 Inverter vendors can incorporate iVSG logic to current control logic.
 Conditions for introducing iVSG : Control board needs enough performance to run iVSG control. Control cycle
time of iVSG is the same as current control.
 If an inverter vendor adapts special current control logic, the interface between
iVSG control and current control may not match.
 Signal interfaces for commands to iVSG is necessary.
KHI license
Commands
to iVSG
Speed upSpeed down
(Voltage up)(Voltge down)

Existing logic owned by inverter vendors
Id command

iVSG
control© Kawasaki Heavy Industries, Ltd. All Rights Reserved

Iq command

Current
control

PWM
generator

Line voltage andcurrent feedback

April 1, 2024

Hardware(Inverter)18

System Integration

Configuration Example
 iVSG inverter can be operated like an engine generator.
 Microgrid operator may install a power management system or operate eachequipment at machine side.
Grid operator’sPower Management System(PMS)

Synchronous
Panel
Run

Run

Stop

Stop

Speed upSpeed upSpeed down

Speed downEngine generator set© Kawasaki Heavy Industries, Ltd. All Rights Reserved

iVSG inverter andenergy storage

PV

April 1, 2024

Load

19

System Integration

Autonomous Load Sharing Load is shared between engine and iVSG autonomously.
 Charge and discharge power can be adjusted by moving droop characteristics.
Discharge
ChargeEngineBalanceFrequency

EngineFrequency

Engine
iVSG

iVSG

iVSG

Frequency

ChargeDischarge
Load© Kawasaki Heavy Industries, Ltd. All Rights Reserved

ActivePower

LoadActivePower

LoadApril 1, 2024

ActivePower
20

Partnership Scheme

Partnership Scheme to Introduce VSG Technology (1) KHI has developed “iVSG ”, a software applicable to inverters, which makes it
possible for the inverter type power sources to possess inertia by simulating acharacteristic of the synchronous generator.
 KHI is working on a project to introduce a decarbonization-promoting energy
system with iVSG to ASEAN and island countries through a partnership schemewith local companies.

© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 2024

21

Partnership Scheme

Partnership Scheme to Introduce VSG Technology (2) KHI is launching a cooperative partnership which will aim to evaluate and advancethe development of FESS(flywheel energy storage system) by Amber kinetics andiVSG inverter by IKS with iVSG (Virtual synchronous generator) solutions fortransition to more renewable energy in the Philippines.
Joint Task Force

Integrated energy system

Flywheel withhttps://amberkinetics.com/

iVSG

inverter

https://global.kawasaki.com/en/energy/index.html

StableUnstablePVs

https://iks-jp.co.jp/

Load sharing autonomously.
No communication line required

Existing Distributed generators

The latest example of joint activity with local companies (the Philippines case,2023)© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 2024

22

Summary
 iVSG is control software for inverter with energy storage, simulating thecharacteristics of an engine generator. The outstanding features of iVSG are as
follows.
(1) Grid forming(2) Droop control(3) Simulated inertia(4) Charge and discharge
 iVSG enables flexible and economical operation of microgrid with energy storageand engine generators while maximizing the use of renewable energy.
 iVSG is the key technology to integrate renewable energy and engine generators
into microgrid.

© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 2024

23

Journal / Conference Paper (1)

Y.Hirase, K.Abe, K.Sugimoto, Y.Shindo "A grid‐connected inverter with virtual synchronous generator model ofalgebraic type" Electrical Engineering in Japan vol.184 no.4 pp.10-21 (2013)

Y.Hirase, O.Noro, E.Yoshimura, H.Nakagawa, K.Sakimoto, Y.Shindo "Virtual Synchronous Generator control with
Double Decoupled Synchronous Reference Frame for single-phase inverter" 2014 International PowerElectronics Conference (IPEC-Hiroshima 2014 - ECCE ASIA) pp. 1552-1559 (2014)

Y.Hirase, O.Noro, E.Yoshimura, H.Nakagawa, K.Sakimoto, Y.Shindo "Virtual synchronous generator control withdouble decoupled synchronous reference frame for single-phase inverter" IEEJ Journal of Industry Applications
vol.4 no.3 pp.143-151 (2015)

Y.Hirase, O.Noro, K.Sugimoto, K.Sakimoto, Y.Shindo, T.Ise "Effects of suppressing frequency fluctuations byparallel operation of virtual synchronous generator in microgrids" 2015 IEEE Energy Conversion Congress andExposition (ECCE) pp. 3694-3701 (2015)

Y.Hirase, O.Noro, K.Sugimoto, K.Sakimoto, T.Ise "Effects and analysis of suppressing frequency fluctuations in
microgrids using virtual synchronous generator control" IECON 2015 - 41st Annual Conference of the IEEE
Industrial Electronics Society pp. 43-49 (2015)© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 2024

24

Journal / Conference Paper (2)

Y.Hirase, K.Abe, O.Noro, K.Sugimoto, K.Sakimoto "Stabilization effect of virtual synchronous generators inmicrogrids with highly penetrated renewable energies" 2016 IEEE 17th Workshop on Control and Modeling forPower Electronics (COMPEL) pp. 1-8 (2016)

Y.Hirase, K.Sugimoto, K.Sakimoto, T.Ise "Analysis of Resonance in Microgrids and Effects of System Frequency
Stabilization using a Virtual Synchronous Generator" IEEE Journal of Emerging and Selected Topics in PowerElectronics vol. 4, no. 4, pp. 1287-1298 (2016)

Y.Hirase, Kensho Abe, K.Sugimoto, K.Sakimoto, H.Bevrani, T.Ise "A novel control approach for virtual
synchronous generators to suppress frequency and voltage fluctuations in microgrids" Applied Energy Vol.210,
pp.699-710 (2018)

Y.Hirase, H.Nakagawa, E.Yoshimura, S.Katsura, K.Abe, O.Noro, K.Sugimoto, K.Sakimoto "Stable Power Supply
Method for Household Appliances via Virtual Synchronous Generator in Single-Phase Three-Wire Microgrid"2018 International Power Electronics Conference (IPEC-Niigata 2018 -ECCE Asia) pp. 767-774 (2018)



K.Sakimoto Y.Hirase, O.Noro, H.Nakagawa, E.Yoshimura, S.Katsura, K.Abe, K.Sugimoto "Decentralised andinterlink-less power interchange among residences in microgrids using virtual synchronous generator control"
Applied Energy Vol.228, pp.2437-2477 (2018)© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 2024

25

© Kawasaki Heavy Industries, Ltd. All Rights Reserved

April 1, 2024

26