［ Hydropower Generating Systems ］

Variable Speed Micro HydropowerSystemKeywords

Speed control, PMG, High efﬁciency

Abstract

We recently established a variable speed power generating system which
combines a permanent-magnet generator and technologies related to power
conversion and speed control.
The variable speed power generating system is composed mainly of a
Permanent Magnet Generator (PMG) and a power converter unit. It features efﬁcient operation, a simpler system conﬁguration, and excellent maintainability.
We expect that this product will contribute as a key product representing theinnovation of a power generating system going forward.

1 Preface
We established product lineups of variable
speed micro hydropower systems by combining a
Permanent Magnet Generator (PMG) and power
converters.
This paper introduces the system conﬁguration, its features, and the result of a veriﬁcation test
using a model testing system.

2 Conﬁguration and Features ofthe Variable Speed Micro Hydropower
SystemFig. 1 shows a conﬁguration diagram of thesmall variable speed micro hydropower system. For
application to micro hydropower generation, thissystem employs a PMG, Meidenʼs standard industrial AC power converter THYFREC VT240S, and aconverter unit: THYFREC 240S.
By using the speed control technology andPMG, we improved power generation efﬁciencies
while there is a change in the drop range.
Fig. 2 shows a comparison of the conﬁguration
between the ﬁxed-speed system and the variable
speed system. Compared with a conventional ﬁxed
speed system, this system offers the following features:( 1) Generator output can be improved despite ahead (drop) changing.
( 2 ) Regardless of the source frequency and the32

Hiroyuki Ogura,
Hiroaki Fujimori

MEIDEN REVIEW Series No.167 2016 No.2

Autonomousoperation mode
Initial charging
in the case of
a power outage

Start-up is possible byusing a PMG induced
voltage in the event ofa power outage.
(Blackout start)

・HC・HF
・Submersible
turbine・Reverserotation ofa pumpUnder the stop
condition, startup is possible inVoltage output the self-operation
mode.
Self-operation
mode

Converter
pump (CNV)
VT240S

CV240S
LCL

MCPMG

CB

440V
busbars

PMG drivefunction

Paralleling
functionProtective function for gridconnection

Sensor lessvector660H(600kW)・PMG sensorless drive
function comes as astandard,・Operating efficiencies
can be improved while
the drop range or theflow rate is changing.

Can apply tomicro hydropower
up to 600kW byVT parallelingfunction.

OFR UVR Islanding operation detection
UFR OVR
Passive Active

Fig. 1

By installing protective functions
per grid-connection regulationsin Japan, formerly required
islanding operation detection
became unnecessary.

Configuration Diagram of the Small Variable
Speed Micro Hydropower System

This is a high-performance hydropower system that can improve
its efﬁciencies under the changing drop range by using variable
speed technologies.

number of poles of the generator, the revolving
speed of the water turbine can be selected.
Consequently, the generator can be directly coupled with the water turbine in a gearless mode. This
construction is very helpful in saving system equipment and improving maintainability.
( 3 ) By using a converter control, the AVR circuit ofthe generator can be eliminated.

Inlet valve
M (Motor powered)

Guide vane

Motor-powered
servo

GOV

Exciting
transformer

Generator

Motor-powered
servo

Controllers

M
Speed
increasing
gear

Inlet valve
M (Motor powered)

Guide vane

AVRSG

Islandingoperationdetection

Generator

PMGGOV

Equipped with Protectivefunctions for grid-connection
CNV(a) Fixed-speed system

Fig. 2Controllers

M(b) Variable speed system

Comparison of the Configuration between the Fixed-Speed System and the Variable Speed System

A variable speed system is adopted to improve output and save system equipment.

[Increase in output by speed control (Example of a crossflow water turbine)]
Drop20m

20.00

16m

Constant
speed

5.00
0200
400
600
Revolving speed (min－1)

Generator output (kW)Head(m)Guide vane
angle

25.00

22°

20.00

16°
10°

15.00

6°

10.00

Max.
efficiency

5.00
0200
400
600
Revolving speed (min－1)

Revolving speed

800

Head 16m

Fig. 3

Condition: Water turbine speed
is increased and operation is
maintained at maximum output.

Max. output
point

Output at
a constant
speed

Max.
efficiency

10.00

0.00

Speed control

12m

15.00

0.00

When the drop range changes, the revolving speed
at the maximum output also changes.

800

Constant
speed

Constant speed

Speed control

Speed(min－1)

Output(kW)Speed(min－1)

Output(kW)

12429

14.8

429

14.8

16429

18.0

507

18.5

2.8

20429

20.0

527

22.2

11.0

25.00
20.00
15.00
10.00
5.00
0.0

15.0

11.0% up

10.0
5.0
1216Head (m)200.0Increasein %0.0

Output improved (%)

25.00

Output (kW)Generator output (kW)Guide vane 16°

Constant
speed
Speed
control
Ratio

Revolving speed at maximum output is changed by the head.
→ Optimal operation is possible by a variable speed system.
→ Operational range is extended to prevent reduction of efficiencies.

Result of Verification Test on a 20kW Crossflow Water Turbine Model

When the drop range changes, revolving speed at the maximum output also changes.

3 Veriﬁcation Test by a Model Testing
SystemFig. 3 shows the result of a veriﬁcation test byusing a model testing system performed on a 20kW
crossﬂow type water turbine. Fig. 4 shows an out-line of the model testing system. We conﬁrmed that
optimal operation is possible even though therevolving speed at the maximum output is changedby the effect of a drop range. When the drop is 20
meters, the 20kW output at a constant speed of
429min−1 can be increased to 22.2kW by increasing
MEIDEN REVIEW Series No.167 2016 No.233

the speed to 527min−1. This is equal to an 11%
increase in output. Due to the aforementioned effect,
we expanded operational range. In this manner, wewere able to conﬁrm that we could prevent thereduction of efﬁciencies on the generator output.

System in factory test bay
3φ－60Hz
440V

Head 12m

CNV

4 Product Lineups of Variable Speed
Power SystemsConverter (CNV)

20kW
CFTable 1 shows a list of product lineups. For
the selection of the PMG capacity, the drop andﬂowrate are examined to determine the water turbine. The power generating system is selected anddesigned after deﬁning the required speciﬁcation
for the generator. Fig. 5 shows the PMG capacity
range for the variable speed power generating system. Converter lineups are included within thecapacity range up to 600kW. An optimal capacity
can be chosen according to the objective microhydropower system. Fig. 6 shows the converter lineups of various speed power systems.

PMGDirectcoupling

Crossflow water turbine (CF)Fig. 4

Permanent magnet typegenerator (PMG)

Outline of Model Testing System

Testing outline is shown and it combines a combination of a
20kW PMG and a crossﬂow water turbine.

Table 1 Product Lineups of Micro Hydropower Systems
With additional variable speed power generating systems, we improved product lineups of micro hydropower systems.
No.
1-1

Water turbine
Francis, crossflow

Generator Operat ing system
SGConstant speed

System configuration
Inlet valve
Servo

Control panel Islanding
operation
GOV AVR detection

Applied products[Conventional products]

Gears

1-2IG

Inlet valve
Servo
Gears
Turbine2-1

Francis, crossflow,
PMG
pump reverse rotation

Variable speed

Submersible turbine

Servo

MEIDEN REVIEW Series No.167 2016 No.2

PMG

Inlet valve

Turbine34

IG

Inlet valve

Turbine2-2

CT panel

SGTurbine

Control panel Islanding
operation
GOV
detection
Reactors &capacitors

CT panel

Control panel
Operation
GOV
command[Speed control system]
・Control panel
・Hydropower converter
・Hydropower PMG

CNVControl panel
Operationcommand
PMG[Conventional products]

CNV[Speed control system]
・Control panel
・Hydropower converter
・Submersible turbine PMG

[Axis of the abscissas] For HF/CF (under planning)
Revolving Runaway
Model Capacity speed
speed22023 000

180
19 000

600

1500

1000
1200

PMG capacity range

K01

110

1500

2300

K02

132

1500

2300

K03

160

1500

2200

K04

200

1500

2200

K05

250

1500

1900

300

K06

300

1500

1900

K07

400

1500

1800

200

OH1600

1200

1900

500

Capacity (kW)Submersible turbine
300kW
900min－1
400 (1650min－1)(OHTAS)

100[Axis of ordinates] For submersible turbine(GORIKI)
0Fig. 5

0500

1000
1500
Revolving speed (min－1)

Model Capacity Revolving Runaway
speed
speed

2000

2500

OHT

300

900

1650

PMG Capacity Range for Variable Speed Power Generating Systems

Speciﬁcations of water turbine are selected according to the drop range and ﬂowrate. The generator system is then determined anddesigned based on the generator design required conditions.

Rated speed: 1050min
Runaway speed: 1250min－1
Rated output (shaft power): 218.2kW
218.2kW1050min－1

Bearing

PMG

MC

DBU

DBR

Converter: CV240S
Inverter: VT240S
Standard panel forabove (2-panel
configuration)

DBR Standard installation
CON
MC CB

INV

DBR
NP900

FAN
NP

2350

Inletvalve

900

Converter panel
250kW

520－1

Pump reverse
rotation waterturbine

Filter

Applicable to sensorless
typeAperture command

Revolving speed

Speed command
Unit: mm

Revolving speed (min－1)

900

Control panel

Inlet valve aperture
90°

Inlet valve aperture

Generator output
Water turbine
revolving speed

[ASR]

600

Standardoperationprogram

ASR rampstart(80% speed)480

ASR speed ismaintained up
to 10% output.

Pickup(25%speed)

150

Control source ON

12s
later

43s
later

030

6090

[Startup command]

120

50

Inverterstop

030

Max. system capacity: 600kW

150

1000-ACR300

Lineups with standard inverter panels(499V Series)

Output (kW)

PLC

660H: 600kW
400H: 400kW
200H: 200kW

Capacity can beselected according
to the product.
(Standard panelapplied)

110H: 110kW
6090[Stop command]

Initial charge completed

120
Control source OFF

System shutdown(Input MC trip)
Main control relay OFF with
operation command OFF

Inlet valve aperture

Fig. 6

Inlet valve aperture

Converter Lineups for Variable Speed Power Systems

Capacities that match the items are selected (Standard panel applied).

MEIDEN REVIEW Series No.167 2016 No.235

5 Postscript
This paper introduced our variable speed
micro power systems with improved product lineups. The variable speed power generating system
is a system that can assure highly efﬁcient operation. It can utilize the renewable energy resource tothe maximum level. Going forward, we will continue
to improve the performance of micro hydropowersystems. For this purpose, we will make efforts to36

MEIDEN REVIEW Series No.167 2016 No.2

apply new innovations in technology and gain thetechnical know-hows from practical experiences.
Lastly, in implementing the model testing on system, we express our sincere gratitude to project
members at EAML Engineering Co., Ltd. for theirkind cooperation.
・All product and company names mentioned in this paper are
the trademarks and/or service marks of their respective owners.