Field tests in the Ílhavo Municipal
Swimming-Pool on transfer between
grid connected and islanding modes
Introduction
Study case description
The increasing penetration of
microgeneration on Low Voltage
(LV) distribution grids and the
implementation of microgrids
require a detailed analysis of the
behaviour of micro-sources and
loads in grid connected and
islanding modes, as well as
during transitions between both
modes.
On the portuguese field tests,
EDP Distribuição (EDP) analysed
the behaviour of a microturbine
installed in the Ílhavo Municipal
Swimming-Pool (MSP), supplying
the local load in islanding mode
and exporting power in grid
connected mode. The interaction
between this microturbine and a
Diesel gen-set was also analysed
in islanding mode.
The field tests were developed in
the first portuguese application
of a microturbine in a MSP. It is
characterized by a micro-CHP
system for water heating and
electric power generation, with
connection to the EDP’s LV grid.
The microturbine has capacity to
generate 60kW electrical power
and 120kW thermal power.
The main loads of the MSP are
characterized by:
• Air treatment units, which
include basically 2 fans
(induction motors) each one;
• Air conditioning systems;
• Water pumps, that support the
swimming-pool hydraulic
circuits;
• Indoor and outdoor lighting.
Main objective
Ílhavo Municipal Swimming-Pool
To demonstrate the feasibility of
transferring microturbine and
MSP loads from grid connected
to islanding mode under various
operating conditions. This
includes transferring in several
load and generation regimens
and the necessary load control.
Single-line diagram of connections between LV grid, MSP load,
microturbine and Diesel gen-set during field tests
Results:
 Field tests demonstrated the
feasibility of transitions
between grid connected and
islanding modes.
 Regarding to this study case,
considering the good level of
short-circuit power and the
reduced length between the
distribution transformer and
the microturbine, the impact
of the microturbine on the
grid power quality was not
significant.
 The operation of the
microturbine in islanding
mode was possible without
significant voltage and
frequency variation for
moderate load variations.
 Parallel of the microturbine
with the Diesel gen-set and a
stable operation, for several
load and generation
regimens, were achieved with
slacken of the microturbine’s
frequency protections.
 Operation in islanding mode
requires control of microsources and loads.
 Based on these concepts, EDP,
with some partners like INESC
Porto, has been developing a
global project named
InovGrid.
Impact of the microturbine on
the LV grid
Microturbine starting and
parallel with a Diesel gen-set
Starting of the microturbine and
power decreasing/increasing (5kW
steps) in grid connected mode.
This test was performed in order
to analyse the impact of the
microturbine on the grid voltage
and to identify its simulation
parameters.
The first two attempts to parallel
the microturbine with the Diesel
gen-set failed by over frequency
tripping. The settings of the
frequency protections of the
microturbine were changed, from
50.5Hz to 51.5Hz, in order to
allow the parallel.
Microturbine output power and grid voltage
Microturbine in/output current during
attempts to parallel with Diesel gen-set
Operation of the microturbine in
islanding mode
Connection of several MSP loads,
fans and water pumps with rated
power of 4kW, 5kW and 7.5kW, to
analyse the voltage and frequency
stability of the system in islanding
mode.
Frequency variations during attempts to
parallel with Diesel gen-set
Parameters identification of the
mathematical model used to
represent the microturbine
dynamic behaviour
Active power during connection of MSP loads
• Parameters estimation based on
experimental data:
- Parameterization of the
microturbine mathematical model
and its control systems;
- Parameters identification:
- Evolutionary particle swarm
optimization;
- Mean square error criterion.
Voltage variations due to load connections
• Results:
Frequency variations due to load
connections
Nuno Melo
nuno.melo@edp.pt
António Cardoso
antoniojose.lebrecardoso@edp.pt
Flávio Cação
flavio.cacao@edp.pt
EDP Distribuição
Rua do Túnel,
Alto de S. João
3030-006 Coimbra
Portugal
www.edpdistribuicao.pt
Fernanda Resende
fresende@inescporto.pt
André Madureira
agm@inescporto.pt
INESC Porto
FEUP campus
Rua Dr. Roberto Frias, 378
4200-465 Porto
Portugal
www.inescporto.pt
Acknowledgments
The authors would like to express their
thanks to the Ílhavo Town Council (Fernando
Caçoilo and Augusto Nunes) and to António
Pintor for their support and contributions to
these field tests.