［ Distributed Power Supply ］

Small-Scale Hydropower System

Keywords

Hydropower, Control unit, Simpliﬁed panel, Variable speed power generation system, Inverter, Converter

Abstract

For small-scale hydropower systems, we reinforced our offerings of productline-ups to meet various needs such as cost reduction, improvement of proﬁtability by increasing annual power yield labor saving, and various operation control capability.
The control unit is the dedicated unit for small-scale hydropower systems.
We commercialized a simpliﬁed switchgear panel to realize a lower cost andsmaller footprint model. There are different models for synchronous generators
or induction generators.
We developed a small-scale variable speed hydropower system that comeswith a combination of a Permanent Magnet Generator (PMG), an inverter, and aconverter. This generator system is expected to increase the annual power yieldamount, supported by extended water turbine operation range thanks to variable
speed operation and high-efﬁciency operation at proper rotating speed.

1 Preface
While the self-sufﬁciency rate of energy supply
is very low in Japan, hydropower systems are precious energy resources because they use water
resources producing entirely domestic clean energy. Although suitable candidate sites for large-scalehydropower projects are few in our present situation, undeveloped or reusable points for small-scalehydropower (1000kW or less) are still abundant.
Due to high construction cost, however, proﬁtability
level is very challenging. Since the enforcement of
the Feed-in Tariff (FIT) System on 1 July 2012, theproﬁtability level for the hydropower project has
been improved and projects for new development orrenovation plans for existing facilities are increasing. In this connection, the Japanese market is ripe.
This paper introduces small-scale hydropower systems that we are working on.

2 Application of Small-Scale Hydropower
Compared with other renewable energy
resources like wind power and solar power, thesmall-scale hydropower system can offer a longer

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Hiroaki Fujimori

MEIDEN REVIEW Series No.169 2017 No.1

lifetime and stable good quality power can be supplied. For this reason, small-scale hydropower systems are applicable to various sites such as dams,
rivers, agricultural channels, city water and sewage
water plants, and factories.
( 1) Use of maintenance water discharge fromsmall-scale dams
This system is used to generate power basedon the use of maintenance water discharge from asmall-scale dam. The generated power is used as apower supply for the dam management ofﬁce.
( 2 ) Use of river waterRiver water is directly used for power generation without any storage facility. Since power generation is dependent on the ﬂow rate of the river water,
annual power yield always ﬂuctuates throughout theyear.
( 3 ) Use of agricultural water
Power generation is dependent on agricultural
water used for the irrigation of rice and vegetableﬁelds. The generated power is fed to agricultural
water irrigation facilities in order to reduce the maintenance cost.
( 4 ) Use of industrial water
Power is generated with the use of the residualpressure at the industrial water intake tank.

3 Small-Scale Hydropower System
3.1 Water Turbine and Generator
Fig. 1 shows a small-scale water turbine selection diagram. An applicable water turbine can bechosen based on the effective head and ﬂow rate.
The generator type can be determined from synchronous generators, induction generators, or Permanent
Magnet Generators (PMG) according to the purpose and system conﬁguration. Some examples ofsmall-scale hydropower systems are shown below.
( 1) Horizontal-shaft Francis turbine generator(Fig. 2)

Horizontal-shaft Francis turbine

Crossflow turbine

Horizontal-shaft Pelton turbine

Turgo impulse turbine

Submerged turbine

The applicable ranges of the effective head
and the ﬂow rate are 10 ～ 300m and 0.3 ～ 15.0m3/s,
respectively. The horizontal-shaft Francis turbines
are most generally adopted in small-scale hydropower plants.
( 2 ) Crossﬂow water turbine generator (Fig. 3)
The applicable ranges of the effective headand ﬂow rate are 5 ～ 80m and 0.1 ～ 8m3/s, respectively. When the guide-vane split type is adopted, it
can assure high efﬁciency down to the low ﬂow ratedomain.
( 3 ) Turgo impulse turbine generation system (Fig. 4)
The applicable ranges of the effective headand ﬂow rate are 28 ～ 400m and 0.2 ～ 0.8m3/s,
respectively. This type of turbine is adopted between
the application range of Pelton water turbines andthat of Francis turbines.

500

Effective head (m)1001010.1

11020

Flow rate (m3/s)

Fig. 1

Small-Scale Water Turbine Selection Diagram

A water turbine selection diagram applicable to small-scale hydropower is shown. A suitable water turbine can be selectedbased on the effective head and ﬂow rate.

Fig. 2

Fig. 3

Crossflow Water Turbine Generator

The crossﬂow turbine generator is applied to many dam typepower stations where changes in the head are enormous.

Horizontal-Shaft Francis Turbine Generator

This is a water turbine generator that has a wide application
range. The electrically powered servomotor is located on the left
front side.

Fig. 4

Turgo Impulse Turbine Generation SystemA series of water turbines made in foreign countries is adopted.

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3.2 Recent Technical Trends in Small-Scale
Hydropower Generation( 1) Cost reduction
Since the power output of a small-scale hydropower system is small, reduction of initial cost isalways called for. We make every effort to reduce
equipment cost by promoting standardization, simpliﬁcation of mechanical structure, and by the compact design. During design work for power plant
planning, the efforts resulted in the smaller footprintof the plant building. It also produced shorter periods for civil and construction work.
( 2 ) Labor-saving Maintenance
For water turbines, the non-water-supply typelabyrinth system or non-water-supply type selfcooled bearings are adopted. For generators, aircooled bearings are used to achieve maintenancelabor saving. Currently, equipment operation without using oil and motor-powered operation are themain currents to prevent oil ﬂow-out into rivers.
Each sliding part of the turbine is made of an oil-lessmetal to operate auxiliary devices for the water turbine, the inlet valve, and guide vane servomotor.
We motorized these units and removed the oil-hydraulic unit. In particular, the servomotor was ﬁrst
used in the world by our company for hydraulicpower plant in 1982.
( 3 ) Simpliﬁed digitization for control unit
As a control unit for hydropower plants,
we developed a general-purpose controller typeall-function-integrated control and protection unit
(MYGENEQUE Series) with enhanced price competitiveness. We have many supply records.
During such engineering resources and supplyrecords, we have developed a very compact design
simpliﬁed low-cost switchgear panel suitable forsmall-scale hydropower systems of hundreds of kW
class. The simpliﬁed switchgear panel is for a synchronous generator. It includes the performance ofsequence control, governor control, exciter control,
and all controls for general-purpose protective
relays, inlet valve main circuit, and control circuit ina single enclosure (W800 × H2350 × D600mm).
Sequence control for the main machine andgovernor control are carried out with the use of ageneral-purpose controller. A touch-panel system isadopted for monitoring and control. A digital AVR(IGBT type) of the YNEX06D Series is adopted for
exciter control. In this manner, we worked to realize
low cost and space saving. For standard functionsof secondary regulation, functions of water level

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regulation control and automatic power factor regulation control are available. The simpliﬁed switchgear panels have lineups for induction generators.
Fig. 5 shows a system conﬁguration diagram for thesimpliﬁed switchgear panel (for synchronous generators) and Fig. 6 shows an external appearance ofthe simpliﬁed switchgear panel.
( 4 ) Wider variety of control functions( a ) Maintenance ﬂow rate control (for dam typepower station)
For a hydropower system which uses the ﬂow
rate of maintenance water discharge from a dam,
the water ﬂow passing through the water turbine isTouch-panel

AVR
Contact
input/
outputAC100VUPSPOWController
CPUDODIInternal busAI
Measurement[Legend]
AVR : Automatic Voltage
Regulator
UPS : Uninterruptible PowerSystem
POW : Power block

Fig. 5

CPU : Control CPU block(Sequence control,Class Z governor unit,secondary governor control)
DI・DO : Digital Input/Output block
AI: Analog Input block

System Configuration Diagram for the Simplified
Switchgear Panel (for Synchronous Generators)

The standard system voltage for equipment is AC 100V.
According to the userʼs request, speciﬁcations for DC 24V arealso available.

Fig. 6

Simplified Switchgear Panel

There are applicable product lineups for both synchronous generators and induction generators.

Self-supporting operation
immediately regarded as the mainteStarting by PMG
mode
Self-supporting
Starting in selfinduced voltage isoperation mode supporting operationnance water discharge of the river. Inpossible at the time
Initial charge in the casemode is possibleof a power outage
of a service interruption
Voltage output
after shutdown.
this power system, it is necessary to(Black out start).
maintain a constant ﬂow rate at all
Converter panel・HC(CNV)・HF
VT240S
CV240S
times despite a variation in the water・Submerged turbine
・Pump reversing
level of a dam. For this reason, ﬂow
LCL CBMC440Vrate control is carried out always conPMG
Bus barsidering the conditions downstream.
This is to avoid adverse inﬂuence on
PMG drive function
Paralleling function
Protective function forgrid-connection
nature and ﬁshery activities by sud660H
Vector(600kW)
OFR UVR Detection of
sensor-lessden changes in the levels of water
islanding operation
UFR OVR
Passive Active
releasing into the river.
・Standard installation of PMG Applicable to smallsensor-less drive function
scale hydropower up( b ) Self-supporting mode operation
・Improvement of operation
to 600kW with VT
When a protective function is provided
efficiency is possible evenparalleling function.
according to the grid-connection rule,
For dam type hydropower genin cases of changing head
an islanding operation detector unit
and flow rate.
formerly required can be eliminated.
eration systems, there is demand for
self-supporting mode of operation ofFig. 7 Small-Scale Variable Speed Hydropower Systemwater turbine generators in order toThis is a high-function hydropower generation system that is capable of efﬁciency
secure power for the dam manageimprovements when it is applied to a head-changing point.
ment ofﬁce in the event of an extended power outage from the grid.
In the self-supporting mode operation, it isnecessary to constantly control both voltage andfrequency using the governor unit and the AVR
unit in the hydropower system. If the operation limit
is needed due to frequency changes by load ﬂuctuations, the system allows the manual operationFig. 8 PMG for Submersion Type Turbineof the self-supporting mode.
A PMG for submersion type turbine is adopted.
( c ) Establishment of a variable speed power
generation system
Our small-scale hydropower system isfor Francis turbines and crossﬂow water turbines.
designed to be a variable speed power generation
Fig. 7 shows a small-scale variable speed hydrosystem supported by a combination of a PMG, apower system and Fig. 8 shows an external apconverter unit, and an inverter unit. It offers outpearance of PMG for submersion type turbine.
standing features of high-efﬁciency operation andeasy maintenance.
4 Postscript
Even though there is a change in the head,
the small hydropower system can maintain high-efThis paper introduced our small-scale hydroﬁciency operation by making the water turbine
power systems. Even in the ﬁeld of small-scalechange its running speed to ﬁt the present head. Inhydropower systems, many technologies developed
addition, it can use an operational range that wasfor general hydropower plants, such as self-suponce considered to be the out-of-operation domain
porting mode operation, digitized control, and varias the cavitation domain of the water turbine. As aable speed operation applied conventionally toresult, we can expect an increase in total annual
large hydropower systems, are being applied.
power yield.
Going forward, we will work on to improve ourWe produced a variable speed power generengineering level to realize low-cost, highly reliable,
ation system by using submersion type turbinesand highly stabile hydropower systems. In so doing,made by EAML Engineering Co., Ltd. Three such
we would like to help the wider introductions ofsystems were supplied to Laos. For the market inrenewable energy resources.
Japan, we supplied one unit of this system using a
pump-reversing submerged turbine. Going for・All product and company names mentioned in this paper areward, we will try to expand the application range
the trademarks and/or service marks of their respective owners.

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