FR2628857A1 - Simulation of stand-alone hydro-electric network - uses coupling supply network with computed regulator control signals to determine behaviour under load change - Google Patents

Abstract

The simulation operates by connecting the turbo-alternator to a supply network (15) at a stable frequency, and proceeds by constantly measuring electric power delivered to the general network by the turbo-alternator (1,3) while injecting a computed measuring signal to the regulation system (6) of the turbine, in substitution for the normal control. The signal is determined by the computer (21) from the frequency vs power characteristic of the simulated stand-alone network. The proportional, derivative, and integral components of the regulation are adjusted systematically by the computer so as to search out the limits of frequency stability of the system. USE/ADVANTAGE - Simulates the response to major load m changes of stand-alone hydro-electric supply system, in which individual loads are major proportion of capacity, giving accurate results through modelling on actual plant rather than by mathematical or digital computation models.

Description

) FRENCH REPUBLIC - Publication no .: 2 628 857 (use only

  for NATIONAL INSTITUTE reproduction orders)

OF OWNERSHIP; INDUSTRIAL TE

  INDUSTRIAL PROPERTY NO national registration: 88 03555 PARIS

  (Int Cl4: G 05 B.17 / 02, 11/36, 15/02.

  A1 PATENT APPLICATION

  ) Date of filing March 18, 1988. t Applicant (s): ELECTRICITE DE FRANCE, Service na-

tional. - FR.

Q Priority

  (Inventor (s) Daniel Simonnot; Jean-Marie Maujean.

  ) Date of public availability of the

  application: BOPI "Patents" n 38 of September 22, 1989.

  (References to other national documents appearing

rented: (r Holder (s)

  a Agent (s): Cabinet Plasseraud.

  _ Simulation method and device applied to an isolated electrical network.

  Method and device for simulating the response to a change in the electrical power consumed by a

  isolated electrical network 2 powered by a turbo-generator 1, 3.

  hydraulic system by which said turbo-generator is connected to a general network 15 at a stable frequency, the electric power supplied to the generator is continuously measured

  general network by the turbo-generator 1, 3 and the 2 is injected.

  measurement signal obtained in a computer 21 programmed r-i '1

  to present the frequency response of the isolated electrical network 25 24 F-r.

  compared to the power supplied and apply to the organs of L. x: 2, regulation 6 of the turbine a signal representative of said 23i ..... 2 22 ... \ 23 I frequency calculated by the computer 21 for the network isolated

  simulated, replacing the normal command.

  Ln N V0 VO EL D Sale of booklets t rlMPRiMERIE NATIONALE. 27. rue de la Convention --75732 PARIS CEDEX 15 i- 'Simulation method and device applied to an isolated electrical network The present invention relates to a method and a device for simulating the frequency response to a change in the electrical power consumed

  by an isolated electrical network powered by a turbo-

  hydraulic alternator and therefore, which comes to the same thing, of the electrical power supplied to this same electrical network isolated by the turbo alternator, since the power supplied to the network and the power consumed

by the network are equal.

  By isolated electrical network means an electrical network which, when powered by the hydraulic turbo-alternator alone or coupled with other groups, consumes a significant nominal electrical power compared to the power

  electric generated by said hydrau- turbo-alternator

  lique, that is to say at least greater than around

20% of this power.

  It finds a particularly important, although not exclusive, application in the field of simulating the responses of an electrical network of consumers whose nominal electrical power likely to be called is between 50 and 80%

  of that of the turbo-generator caused to charge incidentally

  so much on this network of consumers in a fashion

"isolated network" operating system.

  In known manner, a hydraulic turbine cons-

  titue a system with three input parameters: a net drop height, an opening of the water supply or intake valve, generally controlled by a regulator, and a turbine rotation speed in number of revolutions per unit of time, and two output parameters: the turbine flow and the

  power obtained on the turbine shaft.

  The flow rate of the turbine determines the net drop height in tonction of the existing water supply system. The power on the shaft determines the speed of the turbine according to the energy dissipated by the supplied network (alternator included). Everything happens in fact as if the turbine was driving a braking drum with inertia instead of supplying the network, the braking torque of said drum depending on the speed of the turbine and providing a representation of the self-adjusting coefficient. of the network thus simulated, that is to say of the variation of the power dissipated in the network as a function of the frequency generated by

the turbine.

  In the case of a turbine supplying an electrical network which one wishes to maintain at a stable frequency, it is necessary to provide a regulator controlling

  opening the water supply from the vi-

  tesse of the turbine and the evolution of this speed; In the general case, the electrical network supplied by

  the turbine has other generators than the turbo-

  alternator concerned and therefore has a coefficient of auto-

  important adjustment. In other words, when the power of the turbine varies, even significantly, each passive part of the network is little affected. On the other hand, it is no longer the same if a passive part of the network is brought to operate in an "isolated" network on a hydraulic turbine. In this case, it is, more than ever, the proper functioning of the regulator that depends on the stability of the passive network because it is this regulator which makes it possible to minimize the frequency variations caused by variations in the load drawn by said network. It is a rare scheme since we manage in practice so that all the parts of the general network do not function precisely as an isolated network. However, this cannot be avoided in the event of an incident following load shedding. We must therefore be certain that the regulatory system will react

  correctly and does not cause the feed to collapse

  mention of said network which has become "isolated network".

  Known methods for adjusting and

  check the correct operation of a tur-

  bine connected to an isolated network are not satisfied

  doing. In fact, we only know two

  methods which each have several drawbacks.

  The first method is to perform live tests. It requires a long preparation of the network, poses security problems and presents the risk of a failure of the supply of the "guinea pig" network during the tests, to the detriment of consumers. The second method, allowing to test the regulation chain, the turbine and the associated isolated network, consists in making a simulation by numerical model. A digital model can simulate very complex installations where the evolution of the phenomena is calculated step by step with a time step that can be very reduced, for example of the order of 50 ms. Such a simulation is possible since the physical relationships which translate

  the functioning of each organ are well known.

  However, it is necessary to make simplifications

  which partially distort the representativeness of the results by numerical model. For example, we will consider the alternator as transparent vis-à-vis the power of the turbine supplied to the network in a control loop in normal running order. The model

  digital will not be able to simulate the oscil-

  pendulum lations of the rotor and its possible consequences on stability. In particular, an interference between the voltage regulation and the speed regulation, a factor which can seriously disrupt the adjustment, will not be able to be detected and taken into account. In summary, the risk represented by real tests and the imperfections inherent in a simulation * by numerical model do not make it possible to simulate or appreciate satisfactorily the responses to a modification of the electric power consumed by a

  isolated electrical network powered by a turbo-alterna-

hydraulic head.

  The invention aims to provide a method and a simulation device which respond better than those previously known to the requirements of practice,

  especially in that they avoid errors and simplify

  fications of a simulation by numerical modeling and

  the risks encountered during real tests.

  The stability limits and the optimal parameters allowing the proper functioning of a network coupled to a turbo-generator when it will eventually be required to operate in an isolated network on this turbine, can thus be determined reliably and safely. The method and the device of the invention are very simple to implement and allow a simulation the results of which can be seen immediately, in situ, without the need for particularly qualified personnel, and which can be stopped at any time if the simulation shows a fault. Thanks to the present invention, it is therefore easy to perform group maintenance by periodically checking and validating the reactions of the group regulations.

  likely to operate incidentally in an isolated network.

  Thanks to the device of the invention, it is not necessary to simulate the regulator, the turbine, or the water supplies since they are used in real life, which is particularly advantageous in the case where the precise characteristics of these

last.

  We can also verify with a part of the real organs the results obtained using a complete numerical simulation model, which allows

  for example to validate said model.

  To this end, the invention proposes in particular a method for simulating the frequency response to a modification of the electric power consumed by a

  isolated electrical network powered by a turbo-alterna-

  hydraulic tor, characterized in that said turbo alternator is connected to a general network at stable frequency, the power is continuously measured

  supplied to the general network by the turbo-

  alternator and the measurement signal obtained is injected into a programmed computer to present the frequency response of the isolated electrical network with respect to the power supplied and apply to the regulating bodies

  from the turbine a signal representative of said frequency

  quence calculated by the computer for the isolated network

  simulated, replacing the normal command.

  In other words, the fictitious frequency is calculated.

  which would result from the application of the measured power to a fictitious isolated network with the same characteristics as the

  simulated real network and we apply this frequency fic-

  tive to regulatory bodies, in place of

  normal order. The frequency response to a change

  cation of the electric power consumed by the

  isolated electrical network powered by turbo-alterna-

  tor, in other words supplied to said network isolated by said

  turbo-alternator, is thus simulated.

  Maintaining the connection of the turbo-generator to the general network at stable frequency allows

  simple to drain the power supplied by the group.

  The invention also provides a device for

  simlation of the response to a change in power

  electrical power consumed by an isolated electrical network supplied by a hydraulic turbo-alternator, characterized in that it comprises an electrical power sensor connected to a computer programmed to present at output a frequency response of the isolated electrical network with respect to the measured power and means for generating in the regulating members of the turbine a signal representative of the value obtained at said output, said means being connected to the computer on one side and to the regulating members on the other. The invention will be better understood on reading

  the following description of a particular mode of

  embodiment, given by way of nonlimiting example. The

  description refers to the accompanying drawings

  in which: - the. ' Figure 1 is a block diagram showing

  a classic loop constituted by a hydro turbine

  lique, its control chain and a user network, - Figure 2 shows a simulation device according to the invention connected to a hydraulic turbine and

its adjustment chain.

  Figure 1 schematically shows a loop comprising a hydraulic turbine 1 actuating a shaft

  2 rotating a rotor 3 coupled to a network 4 furnace-

  ning in 5 a speed information to the chain of

  control 6 controlling the opening of the feed valve

  tion in turbine water 1. The set values of the regulating or regulating chain are entered at 7. The turbine comprises a supply network 8 and constitutes a system with three inputs: the net falling height or input 9 developed by the supply, the opening of the valve for supplying water to the turbine or inlet 10 controlled by the regulation chain 6 and the speed or inlet 11 determined by the network. The turbine also has two outlets, the flow rate of the turbine or outlet 12 which conditions the net drop height via the supply 8 and the power supplied to the shaft 2 or outlet 13 of the turbine. By neglecting the losses due to the alternator, the network 4 (rotor inertia included) develops the speed 11 from the power 13 which is injected into it. A network is generally characterized by two parameters: - its own flywheel effect, that is to say its launch time T, the order of magnitude of which, for example, can be ten seconds for a network "isolated", is quite independent of the size of the network and close to that of the machines. The network is in fact assimilated to a rotating machine. The launch time is given by the formula: X = I x W with n angular speed of the equivalent machine, I: network inertia and W: motive power - its self-adjusting coefficient R representing the relative variation of the power driving compared to the relative variation of the frequency of the current of the network: R = dW df Figure 2 shows, in dotted lines, 'an advantageous embodiment of the device 14 of simulation of the invention, applied to a turbo-generator 1 , 3 provided with its regulation chain 6, and connected to a general network 15. This device comprises an electrical power sensor or transducer 20 connected to a computer 21 programmed to present at output 22 a frequency response from an isolated electrical network simulated by the program as a function of a signal representative of the power supplied delivered by the sensor 20 to the input 23 of the computer. The device 14 further comprises means 24 for generating in the regulating members 6 of the turbine 1 a signal representative of the value obtained at the output 22. The means 24 are connected to the computer 21 on "one side and to the regulator on the other, for example by means of a switching device 25 making it possible to easily switch back to the normal sensor of the general network at any time during and after the tests In an advantageous embodiment of the invention , the device further comprises means 26 for correcting the power supplied by the turbo-alternator as a function of the frequency obtained for the isolated network.

  eliminate distortion due to stabilization

  tion of the turbine speed by the general network on which the turbo-generator 1, 3 is maintained

  connected throughout the duration of the test in order to

  cue the power supplied by the group. These means 26 can be reduced to a simple series of instructions included in the algorithm of the simulation program of the

  isolated network contained by the computer.

  Furthermore, the coupling of the alternator to the general network gives rise, during sudden transients, to pendular oscillations of the rotor in the stator field supplied by the network, a phenomenon which does not exist in the case of an alternator supplying alone a passive network. The resulting damped oscillations in electrical power can disturb the operation of the control chain. It is therefore also advantageous to plan to correct the electrical power injected into the computer by the following term (involving the inertia of the system): MD2 dn 4 dt: angular speed of the machine measured directly, for example by means of the angle

internal of the turbine.

  D: diameter of the rotor M: mass of the rotor Means 27 allowing this correction are then provided, for example in the form of instructions

  in the computer program 21.

  We will now describe below the method of

simulation of the invention.

  The method of simulating the response to a change in the electrical power consumed by a predetermined isolated electrical network, defined by its

  self-tuning and launch time parameters, power supply

  ted by a hydraulic turbo-alternator, is characterized in that the turbo-alternator 1, 3 is kept connected to a general network 15 at a stable frequency, for example Hz in France, the electrical power Wturbo supplied at 13 is permanently measured to the general network 15 by the turbo-generator and this by means of a sensor 20 known per se and the measurement signal obtained at 23 is injected, into a computer 21 programmed to present the frequency response of the isolated electrical network with respect at the power supplied. A signal representative of the frequency calculated by the computer for the simulated isolated network is then applied to the regulating members 6 of the turbine and via interface members 24. We see that the turbo-generator group 1, 3 flows on the general network at constant frequency, which allows to dissipate the power which, measured and injected into the programmed computer from the two fundamental parameters (auto-tuning coefficient and time to launch) of the isolated network makes it possible to calculate the evolution of the speed of the turbine, which one supposes

debit on said isolated network.

  The regulator requested by the frequency of the fictitious network acts on the admission or opening member via the means 24 transforming the speed

  calculated as a signal readable by the adjustment chain.

  This therefore results in a variation in image power of the calculated frequency variation. By continuously measuring the electrical power supplied to the general network, we can thus see the evolution of the system and in particular this allows us to observe directly and among other things: - The area of stability of the fictitious isolated network and turbo-alternator couple when viewed regulation parameters displayed by modifying the setting of actions

PID of the regulator.

  - The response of this couple for predetermined values of the network parameters (programmed

  in the computer) or the setpoint. The non-linear

  observed rites (for example increase in gain of the control chain with amplitude, followed by saturation) directly illustrate the influence of

  parameters and their modification.

  - The functions for transferring the elements of the adjustment chain in the case where the computer programming injects a variable network into the system,

  for example according to a harmonic regime.

  The method of the invention thus makes it possible to experimentally search for the limits of stability of the isolated system / couple / turbo-alternator network and its regulation chain, to determine the parameters

  optimal functioning and check the behavior

  general system for other characteristics

  isolated network ticks. We can then adjust the proportional integral and derivative actions (PID) of the turbine regulation members so as to prepare the network / turbo-generator couple to react correctly in the event of an incident, i.e. within the limits of stability ensuring sufficient security

to users.

  The calculator, programmed to present the frequency response with respect to the power supplied to the isolated electrical network, uses the following formula giving the evolution of the speed of the machine: dN - t0b - Wr 1 + R () / / \ Wturb r [+ (.. / dtri No 1 with N: speed of the turbo generator group calculated for the isolated network (fictitious) No: nominal speed of the group Wr: nominal power consumed by the isolated network, at 50 Hz R: self-tuning coefficient of the isolated network I: total moment of inertia = I + Ir isolated network group o group = MD2 / 4) 2 Network = T Wr 2fINo rr Tr time to launch the isolated network Wturb: turbine power As a first approximation Wturb is taken equal to the Walt power delivered by the alternator on the general network, generally measured by analog sensor (providing an output signal in 4-20 mA

for example).

  However, provision should be made for the possibility of making two corrections to this power: - An A1 correction due to the pendulum oscillations of the rotor, initiated by a rapid variation in load. An internal angle measurer Y (in radian) allows to work out this 352rid correction

1 = 60 Group No = t-

  - A correction A2 due to the sensitivity of the power of the turbine to variations in the speed of rotation. In a real test, the speed has a (weak) influence on the power of the turbine. This influence is masked in the isolated network test

  fictitious since the machine is coupled to the general network.

  A2 = (W) (N-No) aN Finally, the formula: w - "turb Walt. - + A2 is advantageously used in the fictitious network calculation program. The calculated speed N (t) is then transformed into a periodic signal of frequency proportional to speed f = 50 (N-) and of power compatible with No

  speedometer inputs of the regulator 6.

  In summary, the role of the fictitious network (function of

  power / frequency transfer) is played by the calculation

  trnfr teur 21, 26, 27 working in real time from digital information developed by the

power 20.

  As is obvious and as it follows from the above, the invention is not limited to the devices more specifically envisaged but covers all the variants falling within the framework of equivalences.

Claims (6)

  1. Method for simulating the response to a modification of the electrical power consumed by an isolated electrical network (2) supplied by a hydraulic turbo-alternator (1, 3), characterized in that said turbo-alternator is connected to a general network (15) at stable frequency, the electrical power supplied to the general network by the turbo alternator (1, 3) is continuously measured and the measurement signal obtained is injected into a computer (21) programmed to present the response frequency of the isolated electrical network with respect to the power supplied and apply to the regulating members (6) of the turbine a signal representative of said frequency calculated by the computer (21) for the simulated isolated network, in   substitution for normal command.   2. Method according to claim 1, characterized in that the frequency of the simulated isolated electrical network is calculated in response to a power supplied to said network from the nominal power Wr of the isolated network at 50 Hz, of the auto coefficient -setting R and the time to launch T of said isolated network, and the time r   of inertia Igroupe of the turbo alternator.   3. Method according to any claimed dice   previous cations, characterized in that the adjustment of the proportional, integral and derivative actions of the regulating members (6) of the turbine (1) is modified so as to seek the limits of frequency stability of the simulated isolated electrical network.   4. Method according to any one of the claims.   previous cations, characterized in that the power supplied by the turbo-generator (1, 3) is corrected as a function of the frequency obtained for the isolated network, so that the distortion due to the stabilization of the speed is eliminated. the turbine through the network general (15).   5. Method according to any one of   previous claims, characterized in that   corrects the electrical power supplied to the isolated network taking into account the angular speed n of the turbine. (1, .3).   6. Device for simulating the frequency response to a modification of the electrical power supplied to an isolated electrical network supplied by a hydraulic turbo alternator (1, 3), characterized in that it comprises an electrical power sensor (20 ) connected to a computer (21) programmed to present at output a frequency response from the isolated electrical network with respect to the measured power and generation means (24) in the regulating members (6) of the turbine (1) of a signal representative of the value obtained at said output, said means (24) being connected to the computer (21) on one side and to the regulation (6) of the other.   7. Simulation device according to the claim   tion 6, characterized in that it further comprises means (27) for measuring the angular speed of the turbine and for generating a signal representative of this speed for the computer. 1/1 FIG. 1. 5. Io 1t1 t 3 FIG. 2. 8 6 14 26 ,,,. t --- 1 -J '___' / - I 2/1