Paper accepted for presentation at 2003 IEEE Bologna Power Tech Conference, June 23th-26th, Bologna, Italy
Steam unit and gas turbine power station reliable control for network black-start-up A. Borghetti
K. Maslo
G. Migliavacca
Abstract—The aim of the paper is the analysis of the dynamic behavior of a thermoelectric power plant equipped with a steam unit and a gas turbine during the early phases of a black-start-up maneuver for the network restoration. Models of different detail level for two production units and the relevant regulators have been implemented into two simulation tools. The paper contains the description of the different models, identifies the cases in which the two simulation codes predict similar results and presents the main characteristics, as well as the fields of application of the two codes. As an example, the paper presents also an application of simulators developed for the planning and the preparation of island operation and start up field tests of a power station. Index Terms—Power system restoration, power plant models, power plant control, island operation.
I. INTRODUCTION
I
SLAND operation is a rare condition following interconnected system separation into isolated parts - so called islands. This process can be accompanied by total or partial blackout, when all loads or part of them loose power supply. Several blackouts occurred in the past, with extreme economic damages. Restoration plans have been described and analyzed in the literature (e.g., [1-12]). Specific control systems have been proposed in order to improve power plant performances in the early phases of the restoration maneuver (e.g. [13-14], for the case of steam thermoelectric units repowered with gas turbines). As most ISOs, both the Czech and Italian Grid Codes define the black start and island operation capabilities as ancillary services [15,16]. The black start capability makes it possible for a unit to start-up without support of external source. It is a voluntary ancillary service; the system operator, in agreement with the provider of such a service, selects the suitable units able to start-up, to achieve the rated voltage and to eventually operate in island mode without external supports. The island operation capability makes it possible for the unit to operate within isolated part of system. In this operation A. Borghetti, M. Paolone are with the Department of Electrical Engineering, University of Bologna, 40136 Bologna, Italy (e-mail: {alberto.borghetti, mario.paolone}@mail.ing.unibo.it). Karel Máslo is with Transmission Services Dpt., ČEPS, a.s., Elektrárenská 774/2, 101 52 Praha, Czech Republic (e-mail: maslo @ceps.cz) Gianluigi Migliavacca and Silvano Spelta are with CESI, Via Rubattino, 54, 20134 Milano, Italy (e-mail: {migliavacca, spelta}@cesi.it) Ivan Petružela is with I&C Energo, Pražská 684, 674 01 Třebíč, Czech Republic (e-mail:
[email protected])
0-7803-7967-5/03/$17.00 ©2003 IEEE
M. Paolone
I. Petružela
S. Spelta
mode the unit must cover load changes by exploiting its own autonomous control, in contrast with normal parallel operation, where the responsibility of covering load changes is a task of the entire system. Each new Czech unit connected into transmission system must have the so-called island operation control capability. These units run under such a control mode if the frequency value drops under 49.8 Hz or if the frequency value rises above 50.2 Hz. Computer simulators are efficient tools for island operation investigation; additionally they are useful for planning the required field tests. The dynamic models implemented in these simulators have to be conceived to allow the representation of the system behavior in island condition, which is characterized by large voltage and frequency deviations. The aim of this paper is to describe the dynamic behavior of a thermoelectric power plant equipped with a steam unit and a gas turbine, during the early phase of a black start-up maneuver for power system restoration. For such a purpose, models of different detail level for the two generating units and for their regulators have been implemented into two different simulators (MODES [17] and Lego [18] codes). The MODES code is an all-purpose network simulator. The Lego code is a modular code, developed at the ENEL Department of Research & Development (at present included in CESI s.p.a.), enlarged within the framework of some research projects involving some Italian universities (e.g. [19,20]). Lego has been extensively used for complex process real-time simulators development devoted to engineering analysis and plant operators training. The implementation of the simulator was accomplished by means of a set of CAD-like user-friendly tools for building and managing models [21]. In Section II, the models implemented in the two simulators are described. The different regulation modes of prime mover used for island operation in the Czech and Italian power systems are illustrated and discussed as well. In Section III a comparison of the results obtained by using the different simulators are presented. Typical maneuvers of load restoration are simulated to show the capability of gas and steam units to operate in island conditions. Section IV presents an application developed for the planning and preparation of island operation and start up field tests at a power station. II. MODELING OF THE POWER STATION AND ITS REGULATORS The dynamic behavior of a repowered thermoelectric power station depends on the specific characteristic of the steam unit
and of the gas turbine, as well as on the nature of the coordinating control system, if any. The dynamic behavior of the units is simulated by different level of detail in the two simulators. Both in the MODES and in the Lego simulator a coordinating scheduler is included. A. Models of the thermoelectric power plant included in the MODES simulator Flexible prime mover control models able to simulate both normal and island operation control modes are implemented in the MODES network simulator. Fig. 1 illustrates the model of island operation control mode of a steam unit. NR Turbine Power + Σ NT
Steam Generation NTmax
+
NTmin
NZ -
+
Σ
1 1+pTfO
NZ Steam Generation Reference 1 + + Σ sG Generator Speed Deviation
pZ
+
Reference
Σ
+ + + Σ +
kp dp
1 pTI2 Gmin
10*pTd2 1+pTd2
Pressure Correction
+ + Σ + Σ +-
Π
pT
+
-
ε
Σ
1
1 pTI
+ +
Σ
1
pT Admission pressure
HP Bypass Valve vPS
1
1 TPS
+ Σ + -
1 p
HP bypass steam flow rate M VPS Π
0
-vPS MVS0
0 RK Boiler Controller Output
Gmax
Gmin
Σ
pTDPS
1
1 1+pTEH
+
pTCB
PIDP Regulator kP
k PD
Drum pressure Boiler dynamics
Water wall lag
Feel delivery Reference pressure p Admission Z Pressure -
Σ
kDPSpTDPS
NTmin
Kp2 Gmax
+
Σ
Regulator Fuel dynamics Heat transfer output + e - pT D 1 RK 1+pTFUEL 1+pT W
0
Speed Control
Reference Speed Σ wZ + Inlet Steam Pressure pT
-
1 pTIO
+
Steam flow rate MT
dMP kpO
NTmax Σ
Filtering
HP Bypass M VPS
Fig. 2. Boiler and HP bypassing control models
The flexible structure of the MODES prime mover model makes it possible to simulate also the so-called start-up control mode used for steam units equipped with once-through boilers, shown in Fig. 3.
RT
Turbine Controller Output
Pressure
Fig. 1. Model of the steam unit regulators for island operation control mode.
The proportional - integrating boiler regulator controls the steam generation to reference value NZ. This value corresponds to the turbine output (determined by the turbine control governor) increased by reserve power NR. This additional steam generation flows through the bypass valves and, therefore, the boiler is able to increase its power as soon as the bypass valves are closed. A speed controller with a pressure correction accomplishes turbine control. Speed control can be of proportionalintegration type or simply proportional regulators. Pressure correction is used only for positive pressure deviation; and the high-pressure (HP) steam bypass is used for pressure control. When the pressure is lower than the reference value, the turbine control valves are closed. The boiler model, shown in Fig. 2, corresponds to the scheme described in [22], with the adjunct of a bypass valve. The very high-pressure bypass valves (which lead the steam back to the reheater) and low-pressure bypass valves (which lead the steam directly to the condenser) were modeled by one equivalent bypass valve. An improved boiler model with separation of superheater and drum dynamic, proposed in [23], is being implemented in the next version of the MODES code.
kVS
kN
GeneratorPG Active Power
dSp
Generator sG Speed Deviation
1+pTN
kSp
Speed control 'STRC/ISLN' or overun
Gmax
-
1 1+pTEH + Σ NZ RT Σ Σ Gmax Σ stepN Turbine NS + Gmin + NTmin + Controller 1 COR T Output pTIT External regulator correction 1 Gmin RK kFOR fZ 0 NFmax + dFR Boiler k COR f -Σ NZ Turbine Output Demand Controller NFmin Frequency Output NS Turbine Output Request NTmax
kT
vN
+
Fig. 3. Model of the steam unit regulators for start-up control mode.
The turbine regulator consists of a PI power controller (with frequency correction) and a parallel proportional speed governor. The boiler controller is modeled with some simplification: i.e., fuel demand is proportional of turbine output request demand. The MODES simulator contains also additional common models of so-called automatics and external regulators. Automatics make it possible to model different types of relay. They measure specific variables and if some predefined conditions are satisfied, a predefined action is carried out. The scheme of an external regulator is shown in Fig. 4. Measuring element Set value k1 ZADR 1+pT1 X
+
1
Inputs
X2
Σ k2 1+pT2
+
+
-
Σ
NEC
Nonlinear dead band
PI controller Yi=KRTR for Kod=3
KP
EPSR
Rmax 1 pTI Rmin
+ Σ
+
REGR Rmax Rmin
Yi=KORB for Kod=1 Yi=KORT for Kod=2
K1 K2 K3
Y1 Y2 Y3
Kn
Yn Outputs
Fig. 4. Block scheme of a common external regulator model
The two inputs, shown in Fig. 4, are two variables of the system. There can be several outputs, connected to the models of the various system components, e.g., to load tap-changers, exciters and voltage regulators, or to prime mover models, as
the correction signal COR of Fig. 3. The gas turbine model implemented in the MODES simulator is described in [24,25]. B. Models of the thermoelectric power plant included in the LEGO simulator A detailed description of the models of a repowered thermoelectric power plant implemented in the Lego simulator is reported in [14], where the results of some simulations are also compared with measurements obtained during restoration field tests at some power stations. The simulator refers to a 320 MW steam unit group (SPP) with once-through universalpressure boilers burning fuel oil, and a 120 MW gas turbine unit (GT). The dynamic mathematical models developed for the simulator represent the gas turbine, the boiler, the steam turbine with their relevant regulations, the generators, the power station auxiliaries and part of the transmission network connected to the station. The model of the 120 MW gas turbine reproduces essentially speed and load regulation, fuel feeding combustor and air compression dynamics [24]. The control system includes speed control, acceleration control and a local frequency integrator (LFI) correcting the GT load demand in order to reduce the frequency error to 0.1 Hz. This integrator intervenes when the frequency error exceeds 0.3 Hz or when the turbine power output changes too rapidly. When the LFI is not operating, the set point of the speed governor is modified by the gas turbine load demand, through a load programmer. Acceleration control is used to limit the rotor acceleration, thus also limiting the thermal stress during start-up. The output of the speed governor, adjusted by the output of the acceleration governor, is the input of the fuel valve positioner. This has two different actuation speeds, a slower one for opening (100% in 15 s) and a faster one for closing (100% in 2 s). The lowest valve position (15%) corresponds to the minimum gas flow rate able to guarantee a correct combustor operation. During the black start-up maneuver, the most important phenomena involving boiler dynamics are those concerning frequency variations. In the start-up phase, frequency regulation mainly concerns high-pressure turbine steam admission valves (hereafter simply called HP valves), while the intercept valve is kept completely open. The simplified models of the 320 MW steam section take into account the mass and momentum conservation equations, as well as pressure regulation dynamics. Temperature regulation effects, instead, have been neglected, as they involve time constants much greater than those relevant to pressure dynamics, as shown by the results obtained by using a more detailed simulator developed at the ENEL research laboratory and described in [26]. The scheme of the normal and start-up steam flow circuit of the steam power plant is shown in Fig. 5. All the start-up circuit valves have been considered: valves 207, 270, 240 and 200. Valve 240 controls at 60 bar the steam pressure Pft inside the flash tank, by discharging the steam in excess to the condenser. Valve 270 assures the control of the
steam temperature at the reheater outlet during start-up. Valve 207 controls the boiler pressure at 170 bar or at a lower value if the flash tank pressure drop exceeds 14 bar. During the start up phase valve 200 is kept closed and is opened when the load is above 110 MW, at the same time valve 207 is closed. Valve 205 is a noreturn valve.
Fig. 5. Scheme of the start-up steam flow circuit of a once through Universal Pressure boiler
Three different power plant control modes have been implemented: - a start-up control mode, operating during the start-up maneuver until the load becomes greater than 110 MW; - a turbine-follows-boiler control mode, - a unit-coordinator control mode. The description of the start-up and the relevant scheme has been given in [14]. In Fig. 6 we give also the scheme of the turbine-follows-boiler control mode. The load required is input to the steam generator control system as fuel demand (from 0.2 to 1.2 p.u.). The load demand to the turbine control system is adjusted by the feedback PI regulator that controls the main steam pressure, as well as by the proportional primary rotor velocity regulator. The main pressure set point of the PI regulator is a function of the turbine mechanical power; such a function is linear with a minimum of 81 bar at 110 MW and a maximum of 170 bar at 240 MW. The main pressure regulator allows also the turbine pressurization at constant load. main steam pressure
turbine pressurization
pressure set-point adjustment
SPP load demand
steam pressure regulator -
fuel request
+
+
1+sTc sTc
frequency set-point
+
steam turbine load + reference Kg speed droop
-
frequency
Fig. 6 Turbine-follows-boiler control mode scheme
Frequency control is one of the most critical problems during power system restorations. It is necessary to avoid that load energisation transients cause significant frequency degradation such as to involve generators protections intervention (below 47.5 Hz for 4 s, below 46 Hz for 1 s). In case the GT and SPP perform contemporarily the restoration maneuver, the two relevant frequency regulators must be suitably coordinated. The load scheduler shown in Fig. 7 has
been implemented in the simulator [13]. It accomplishes load energisation by increasing first the power request to the GT section and by allowing the SPP section to be loaded only subsequently, when the boiler conditions are adequate. The basic function of the load scheduler is to maintain the GT load as low as possible, in order to make it sustaining the whole frequency transient caused by ballast loads energisation. Only after the end of the frequency transient and if the boiler pressure is high enough, the load scheduler increases progressively the load request to the SPP section, contemporarily unloading the GT. SPP active power minimum TG load
GT active power + +
-
low frequency logic enable
GT and SPP
steam HP turbine pressure
LOAD SCHEDULER
GT and SPP synchronisation logic
GT load decreasing network freq.
nominal freq. -
+
Fig. 1). Time evolutions are stable and smooth. The transient frequency deviation is attenuated by the fast gas turbine response. The steady state frequency deviation is compensated by the steam turbine PI speed control, which makes it possible to unload the gas turbine in order to make it ready for another load pick-up. Pressure is controlled by the HP bypassing. The steam turbine has a 10% steam reserve bypassed into the condenser. When the inlet pressure goes down due to the control valves opening, the bypass valves are closed and the steam goes to the turbine. When the boiler control increases the fuel supply and the boiler pressure is restored, the bypass is opened again. Control strategy with the load scheduler was implemented as well. The simulation results relevant to the same load energizations of Figs. 8 and 9 are shown in Fig. 10. 50.1
frequency [Hz]
Mechanical Power [MW]
M
GT local request from the operator + + +
+
+
70
SPP local request from the operator
49.6
60 50
GTG -gas unit
f enable
80
SPP load increasing
Frequency local integrator (FLI)
GT load programmer
49.1
SPP load
40 30
G1 -steam unit
programmer
48.6
20
SPP load request GT load request low freq. logic
K
48.1
f +
+
GT turbine load request
K +
f
+
0
1
A. Results obtained by using the MODES code The following two figures show the time evolution of different quantities during two subsequent loads pick-up. The gas turbine governor is of proportional type and the steam turbine is in island operation mode (according the scheme of
4
5
6
7
8
9
10 11 12 13 14 15
0
Valve opening
Turbine Inlet S team P ressure
Fig. 7. Scheme of the load scheduler for the black-startup maneuver.
A part of the transmission grid (at 130 kV, 220 kV, 380 kV voltage levels) in the vicinity of a power station with one 320 MW steam unit and a 120 MW gas unit is considered as a case study. In the MODES code the loads are modeled as a constant admittance whereas asynchronous motor simulate a mix of static load and aggregation of motors. In the Lego simulator a specific load model has been implemented that reproduces the typical dynamic behavior of load request when the load is reenergized after a black out.
3
[pu]
0.4
III. CASE STUDY AND SIMULATION RESULTS
2
Fig. 8 Frequency and mechanical power of gas and steam units during to subsequent load pick-up.
SPP turbine load request
Another important role of the load scheduler is to advise the operator when the plant reaches the good conditions for additional loads connection, i.e. when the GT power output is sufficiently low (less than 70% of the rated value), the FLI device is not active and the HP steam pressure of SPP is high enough (more than 80% of the rated value).
10
t [min]
0.3
0.2 Mechanical power 0.1
0
HP Bypass S team Flow R ate t [min] 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Fig. 9. Variables of the steam units, relevant to the same load energizations of Fig. 8. 50.1
frequency [Hz]
Mechanical P ower [MW]
70
-0.3
60
49.6 GTG -gas unit
50 40
49.1 G1 -steam unit
30 20
48.6
48.1
80
t [min]
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15
10 0
Fig. 10. Frequency and mechanical power of gas and steam units, with load scheduler, for the same load energizations of Figs. 8 and 9.
The gas turbine is controlled by frequency local integrator, which is activated when the frequency falls down under 49.7 Hz. Steam turbine is in start-up control mode (according to the scheme of Fig. 3). Gas and steam demand power is redispatched by load scheduler, which is modeled, in the MODES simulator, as an external regulator. If we compare the Fig. 8 and Fig. 10, we can see similar results: stable frequency restoration and gas turbine unloading, which make it possible to be ready to take over future load increasing. B. Results obtained by using the LEGO code Fig. 11 presents the simulation results of the pick-up of two loads (30 MW rated power) at two different 220 kV busses when the steam unit in the turbine-follows-boiler regulation mode (according to the scheme of Fig. 6). After each load pick-up, the steam section participates to the frequency regulation, together with the gas turbine, only during the first seconds. In the subsequent minutes the frequency local integrator controller increases the fuel request of the gas turbine, satisfying in this way the total load demand. For this reason, the steam turbine does not increase its power, saving steam production in the boiler. When the pressure attains 80% of its nominal value and the frequency error is less than 0.1 Hz, the load scheduler progressively discharges the gas turbine load and increases the load request of the steam turbine. 50.5
240
Frequency frequenza 50
200
Power potenza [MW] [MW]
49 120
potenza meccanica TV power Steam unit mechanical
48.5
Turbo gas unitmeccanica mechanical power potenza TG
80
40
47.5
0 0
200
400
600
800
1000
1200
47 1400
Time tempo[s] [sec]
a) 190
100% 90%
pressione ammissione Pressure
170
80%
160
70%
150
60%
140
50%
130
40%
apertura valvola posizione Fuel valve opening position
120
Fuel valve opening [%] apertura valvola ammissione
Pressure pressione[bar] [bar]
180
30%
110
b)
48
Frequency frequenza[Hz] [Hz] Frequecy [s]
49.5
160
0
200
400
600
800
Titempo[ [sec] ]
1000
1200
20% 1400
Fig. 11 Energization of two 30 MW loads with gas and steam units synchronized, steam unit in turbine-follows-boiler regulation mode: a) steam unit outputs and gas turbine outputs; b) steam unit flash tank pressure and HP valve opening.
IV. USING OF SIMULATORS FOR FIELD TEST PREPARATION Several field tests of black start-up are regularly carried out by various power systems operators. For example, in the Czech power system, black start tests have been recently carried out both at the transmission level (e.g., the start-up of the Dukovany nuclear power plant from a 113 MW Francis hydro turbine, in 1994 [3]; the start-up the Chvaletice thermal power plant from a 320 MW Francis hydro turbine, in 1996 [8]) and at the distribution one (e.g., the start-up of the Hodonin thermal power plant from a 6 MW Kaplan hydro turbine, in 2003). These field tests should be carefully prepared, because they are risky and difficult from the organizational point of view and usually they cannot be repeated. That is the main reason for the use of network simulators during the preparation phases to avoid failures and stability problems during the execution of the field tests. In the near future, a field test is planned to assess the capability of the nuclear Czech power plant Temelin (ETE) unit to successfully manage the transition to island operation, and to control the power variations in such an island operation mode, as well as to prove its capability to be back synchronized to the grid [27]. During the field test, it is planned that an island will be created within the Czech Republic national grid, which will include the ETE power station, its main transformer and house consumption, and part of the 400 kV network, including the Kočín, Dasný and Slavětice substations and a unit of the Dalešice pump storage hydro plant, which will be operated in pumping mode (see the schemes of Figs. 12 and 13). For the preparations of this field test, the Czech system operator ČEPS carried out a study, by means of the developed computer simulator, in order to verify that there will be neither voltage nor frequency collapse problems during the island developing phase and during its operation. In the following, some of the results relevant to the simulation of the island operation of the Temelin nuclear power plant, in the conditions required in the planned field test, are shown. The results refer to two phases: namely, the asynchronous starting of a 113 MW unit at the Dalešice hydro power plant, and its transition to pumping operation. The hydro unit in pumped operation will be used as main load, during the planned field test.
subst. Kocín
subst. Dasný
subst. Slavetice
subst. Kocín
400 kV
V433
V473
3 km
subst. Dasný
36 km
143 km
2 km
36 km
1111 MVA 0.2
-0.1
T11
T12
6 kV BBD1BBC1 BBB1 BBA1
68 MW
121 MVA Dalešice
ETE1
M
1111 MVA
P [MW]
20
0
10
20
30
40
E T E 1 s p e ed d e viatio n [% ]
-0.2 -0.3
-0.6
0
-20 GE N2 Active P ower [MW]
-0.4 -0.5
13.8 kV T11
G
GEN2
sG [% ]
0
2 km
23.6 kV
0.1 0
143 km
13.2 kV
G ETE1
V433
V473
3 km
23.6 kV T12
subst. Slavetice
400 kV
-40 t [s]
0
Fig. 12. Speed deviation of unit ETE1, during the asynchronous start-up of unit GEN2.
Fig. 12 shows the scheme of the islanded power system and the speed deviation behavior of generator ETE1 at the Temelin nuclear power plant, during the asynchronous starting of the unit generator GEN2 at the Dalešice hydro power station. As shown in the scheme, during the asynchronous starting, the excitation winding of the hydro unit generator is short circuited through a resistance and an additional series reactor is connected. During this phase, the synchronous machine operates as an asynchronous motor. The unit ETE1 delivers the active power required for the hydro group acceleration. The maximum speed deviation is about 0.55% (275 mHz), and the transient behavior of the system is stable. When the hydro group speed is near the nominal value, the excitation resistance and the series reactor are rejected and the machine of the hydro unit is excited. During this phase, the synchronous machine operates as a synchronous motor. Then the gate is opened and the group starts to pump water to the upper reservoir. Fig. 13 shows the scheme and ETE1 speed deviation during the transition to pumping operation of hydro unit GEN2.
BBD1BBC1 BBB1 BBA1
84 MW
10
GEN2
121 MVA
M Dalešice
20
30
t 40 [s]
0
-0.1
-10
-0.2
-20
-0.3
-30
-0.4
-40
-0.5
-50
-0.6
-60
-0.7 -0.8 -0.9
-60
6 kV
-1
E TE 1 speed deviation [% ] GE N2 Active P ower [MW ]
-70 -80 -90 -100 -110 P [MW ]
-1.1 sG [% ]
Fig. 13. ETE1 speed deviation during the transition to pumping operation of unit GEN2
As shown in Fig. 13, a steady state speed deviation of about 0.8% occurs, which corresponds to an 8% permanent speed droop of the governor of the ETE1 unit, which operates in proportional speed control mode. V. CONCLUSIONS The paper has presented the models of a thermoelectric plant equipped with a steam unit and a gas turbine, implemented in two simulation tools with the aim of assessing its black start capability. The study confirms that the proposed load scheduler and traditional control system modifications can provide an effective help to plant operators. The first simulator (MODES) is more suitable for power system planning (e.g., for creation of network restoration plans) and the second one (LEGO) for power plant design and operators training. The first one is particularly suitable for batch simulation (but a version in form of a dynamic linking library, usable in the energy management system, is prepared as well); the second one exhibits real time capabilities and offer the possibility, for training purposes, of operator interactions and real time observation of the start-up procedure (synchronization, voltage set point control to avoid instability, etc). In the course of the preparations of a field island operation test, the Czech system operator ČEPS prepared a study (based on the MODES simulator) in order to verify the absence of voltage or frequency collapse problems during the island-
developing phase and during its operation. VI. ACKNOWLEDGMENT The authors gratefully acknowledge the contributions of Prof. C. A. Nucci for its helpful suggestions during the preparation of the paper and its useful comments to the manuscript. VII. REFERENCES [1] [2]
[3] [4] [5]
[6]
[7] [8] [9] [10]
[11]
[12] [13]
[14] [15] [16] [17] [18]
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VIII. BIOGRAPHIES Alberto Borghetti was born in Cesena, Italy, in 1967. Graduated with honors in Electrical engineering at the University of Bologna, Italy, in 1992. Since then he has been working with the power system group at the same University. His main research interests are power system simulation, with reference to voltage collapse, system restoration, electro-magnetic transients due to lightning and generation scheduling. He is author or coauthor of more than 40 scientific papers presented at international conferences or published on reviewed journals. Karel Maslo was born in Jihlava, Czech Republic, on July 1956. He received his E.E. diploma from Czech Technical University, Prague, in 1980 in electrical engineering. In 1985, he received his Ph.D. on stability of synchronous machine. As a university teacher and research worker he dealt with power plant and power system protection and reliability, electromagnetic and electromechanical transients and dynamic simulation. He is involved in primary and load frequency control cooperation in frame of the Study for the Connection of the Czechoslovak Network to the UCPTE. He joined Czech main power producer company – CEZ in 1992, where was responsible for the creation of dynamic models and dynamic calculation. From 1999 he worked for Czech TSO – CEPS. He is author of the network simulator MODES and deals with problems of Czech Grid Code, system and ancillary services as well. He has taken part in several CIGRE and UNIPEDE working groups. Gianluigi Migliavacca received his degree in Electronic Engineering from the Politechnic University of Milan in 1991. In 1994 he was engaged in the Automation Research Center of ENEL where he has been responsible of research activities in the field of mathematical modeling and numerical methods for the dynamic simulation of thermal power plants. During the year 2000 he joined CESI in Milan where he works, now, on mathematical methods and modeling for the energy market.
Mario Paolone was born in Campobasso, Italy, in 1973. Graduated with honors in Electrical engineering in 1998 at the university of Bologna, PhD from the same University in 2002. He is currently working within the Power Systems Group of the University of Bologna. His research interests are power system transients, with particular reference to NEMP and LEMP interaction with electrical networks, power systems dynamics and electric vehicle batteries. He is author or coauthor of about 30 scientific papers presented at international conferences or published on reviewed journals. Ivan Petružela was born in Hranice, Czech Republic, on May 1962. He received his E.E. diploma from Czech Technical University, Prague, in 1985 in electrical engineering. In 1989, he received his Ph.D. on dynamic behavior of nuclear power plant. As a research worker he dealt with power plant and power system operation. He is involved in early detection of power system disturbances as a condition for safe operation of NPP Dukovany. From 1997 he worked for I&C Energo, where was head of several tests of NPP Temelín control system during the power ascension testing stage. He is responsible for the creation of operator support system. Silvano Spelta obtained his diploma in electronics in1966 in Milan and entered in 1967 in the R&D Department of ENEL. He developed some numerical programs for power system transient analysis. In 1978 he started developing the general/modular simulation code LEGO. From 1982 to 1984 he has been detached at EDF/SEPTEN working on PWR power plant dynamic analysis, and up to 1987 he developed nuclear plant simulators for the automation design support. After the Italian nuclear plan stop, he has been involved in new power plants (repowering and combined cycles) automation design aid developing real time engineering simulators. Project leader from 1993 to 1995 for the HRSG automation design and testing of Montalto di Castro repowered units. He is now working in CESI mainly in transient analysis for distributed power generation.
