╨╧рб▒с>■  ЛН■   ЙК                                                                                                                                                                                                                                                                                                                                                                                                                                            ье┴G ┐cbjbjО┘О┘ рь│ь│_      ]───────DDDDD PTD7Ў╕╕╕╕╕╕╕╕№■■■■■■$-Ї!╓"─╕╕╕╕╕"╕──╕╕╕╕╕╕╕─╕─╕№╪66────╕№╕D╕№──№╕д@╧Ир│З╜DD╕№ SIMULATION OF VESSEL 'S ELECTRIC SYSTEM - NET Maja Krcum Maritime Faculty Split, Zrinskofrankopanska 38, HR - 21000 Split, Croatia Phone: (021)341-382 Fax: (021) 341-382 E-mail:mkrcuma split.pfdu.hr Abstract: It is not always possible to note the effects of a interdependence between the current, voltage and damage on a part of the vessel's electric system-net in magnetic flow. The equations have been given in the co- normal work conditions. Certain damages are rare so ordinate system d and q, the axis of the rotor (vertical and their effects are rarely noted. That is the reason of horizontal axis respectively): simulating certain damage effects by computers. The vessel's electric system-net is computed by dynamic d uk =rk Ik +-k elements presented by dynamically simulated continuo's dt model. Material and data sequences are possible to be traced by this method. Some parts of the vessel's electric (I) k =xk! It +xk Ik net (generator, consumer, generator driver, etc...) are t=i presented by a mathematical model (first and second where the index k =1,2, ... m. label equations). Certain options have been simulated. In synchronised generators with damping circuit the This methodology has enabled the students and teachers difference in values of induced resistance of mutual to analyse the dynamics of the vessel's electric system- inductance on the axis can be ignored, i.e. the difference net and its parts without jeopardising the analysed between the position of the core and the induction flow is system. In this way we have achieved two aims: the not taken into account. Equations of the stator contour teacher's research work and the education of students. are included into the generator equation system: d I. INTRODUCTION ud =-r i, + t `F'd - w The electrical power network requires a quick and d effective operation in the initial stage of its design, both u =-r i9 +-' +d w (2) by the designers and the people operating it. The dt complexity of the shipboard electric power system can be d =-(xQd+xs)id+xadlJ+xal viewed through the ship's power plant, ship's switchboard power, consumers, the logic of control, as well as remote  =-(xp9+xs)i9+xaqiq surveillance and control, signalization and measuring. This is why it is simpler to observe the dynamics of some ud and u9 - voltage in contour of stator by C and q characteristic components, as for example the generator, turbines, asynchronies motor, etc. and the corresponding axis models which have been expressed by first and second Drive part is determined by: label differential equations. By means of the system's d dynamics various conditions within the system have been uJ =rf i J +-`t'f d t (3) simulated. This simulation method enables us to research, as well as to optimise various conditions and parameter `I'j = (xod +xJ)if +xpd Id -xad Id without unnecessarily exposing the system to damages or disturbing its balance. In this way it is possible to The damping circuit is determined by: examine and check the stability and functional value of the shipboard electric power system. d dt _ d II. THE STEAM TURBINE-GENERATOR SET DYNAMICS Y'qllq + dt A. Synchronised generator Id (xad + xld)Ild + xadlf xadld A generator which derives mechanical energy from the (xQq + xq )iq - xQ9i9 steam engine (turbine) is often used as a source of electric power by the shipboard electric power network. If a self excitation based on the principle of phase Transitional phenomena in alternative current compounding with generator voltage declination control synchronised generators can be expressed by equation should be chosen in this case, then the equations systems [ I ) which describe the functional determining the driving voltage are as follows: 1 i9  -( - 9 ) rj + rk u . = (1+k kn id )-rk i J (5) xd x where k can assume the following values: `Ild and `P - magnetic flux in stator contour by d and q axis 1 k -k k 1 nmax nmln (u-1) umax umin lJ J d) xJ if is umin  u  umax , k =k i J and u J - drive current and voltage u umax if is u < u 1 min , 11d (ld  d ) k =k . nmin if is u ? umax╖ (6) xpd - armature reactance by the vertical axis If it is u =ud +uz the parameter k assume : 1 9 Ily (ly  y ) ( .r n ) ( s n )Z x19 r +r r +r k = + xd + xn - 1 +  (7) xp9 - armature reactance by the horizontal axis xN + xn (xq + xn)  d xad ( ld lJ Ild ) The alternative parameter marked with kn determmes the id and i9 - current of damping circuit by the vertical drive of the generator relative to voltage and varies and horizontal axis between knm do knmin wlth the change in voltage from `Iс9 =xn9 (-i9 + iq) udmin t0 udmax' In self excitation system without `Id and `9 - magnetic flux of damper circuit by vertical rectifier the voltage is u =1 (constant), and the k = I as a and horizontal axis ( 11 ) result. The electromagnetic moment of the generator expressed If equation is replaced by any of the equations (1) - (10), by means of current components and magnetic flows in then the following sequence in obtained: the co-ordinate system has the form as illustrated by the following equations: d `Id r r Yd+`Iqw+ `Fd+ud d t xs xs M =d lN - Ld r - resistance in stator circuit The saturation of magnetic circuit by the horizontal axis d ' of the generator can be illustrated by a nonlinear r r 9 s `F -`I'd w + s ' + u function: dt x q x xs - leakage impedance by stator circuit xnd =f, ( d ) d `I'J rJ rJ `F'J + `Iсd + uJ dt xJ xJ The analysis can be simplified if the overall magnetic r and xr - active and reactive resistance of drive flux can be used as a mutual connection of processing in the electromagnetic field. If the overall magnetic flux by circuit only one axis is counted with respect to the equivalent inductive resistance, mutual inductance is as expressed d N rN riN by: `1' + `I с dt x N x i9 IN k xa l I +xk lk - +xk lkf ri, and riN - active resistance of damper circuit by the (k =1,2,...m) vertical axis 1 diYd r,d rd ik =-(`k -`F ) (k =1,2,...m) id + d d t xd xid xk m rk - resistance of compounding circuit `F =xn i, (10) 1 1 1 ri The equation for current in some parts of the x., x xid generator by d and q axis by using these equation: 1 1 1 x xiNd ld (d d) xd rf +rk (rf +rk)k; u f = + kud -  id and iy - current in stator contour by d and qaxis xk xpd xs xf J Jw (rt +rk)k k _ _ n Y + ku + - ad тM SM тMd ' T' SMd xadxч xf e + 2 + __1 _ тW sw тw - (dq  d) Jw x T , = " are time constants. M M - moment e P2 n where are:  P 1 1 1 1 1 --+-+-+- and xi x"d xs xJ xd C. SYSTEM DYNAMICS 1 1 1 1 The system is used for observation of the turbine- --+-+- (13) generator set. System dynamics is a relatively new x, xaq xs xd discipline [2] which possess an effective methodology of dynamics research, modelling and optimisation of B. THE STEAM TURBINE complex natural, as well as organisational and technical The steam turbine is an engine which converts the systems. It offers an optimum combination of system thermal energy of steam into kinetic energy of steam flow parameters. All dynamic transitional phenomena which is further converted into mechanical work. occurring in continuity are there by observed, which is Shipboard systems usually employ turbines to drive most suitable in the field of dynamics of models designed electric motors, for lighting, communications and other for the electric power system. The dynamics of analogous services required aboard a ship. The steam turbine complex dynamic system which have a nuxnber of "feed dynamics can be shown by the following differential back circuits", being either of negative (-) or positive equations [1]: character, is thus researched. In this case discreet simulation on continuous models determined by d LY c condition equations is applied. dt R + (14) A turbine-generator set is illustrated in Fig.1. The signal is added to the one received by the converter and the where is: outgoing angle speed of the turbine is measured. The result is the error difference between the real and the set 0 P, speed. The error is thereupon amplified and conducted to `I  = relative pressure of steam in steam volume the PID regulator. Generator whose outlet is turbine .. 0 Po `Io = relative steam of pressure in front of Pn manoeuvring valve 0 mo ,u = relative change in the manoeuvring valve m n Fig.1. An illustration of urbine-generator set position driven the turbine propelling steam inlet and outlet valves v (P/P)Pn v (P l P)P are opened and closed. The turbine attains the o R = appropriate angle speed and moment driven by the (S Gkr /  P" )P"" ( kl ) n G /тm m generator. Inside the generator itself a regulation circuit v s /s which, based on the generator outlet voltage regulates the are steam volume variable resistance k, is closed, by which the regulation p ( P P)P..  =( G` /  p )-( Gk l P of outlet voltage (u) is carried out. the constant. The simulation plan of turbine-generator set is performed as shown in Fig. 2. The second differential equations is: The process of turbine starting begins at TIME =10 s. The steam inlet valve, amounting to 0.05, is opened. _ _W Due to an even heating the turbine starts rotating, (15) attaining 5% of the nominal speed value. The process of dt T Tw2 the pre-heating takes 50 s. At TIME = 50 s the steam where: inlet valve is open 100% of the nominal opening and the Ow nominal number of revolutions FI = 1 = 100% is soon rp=- turbine angle speed relative pressure achieved. W n Until the point of TIME=100 s the turbine is gradually 0 P and evenly heated to the nominal temperature and = steam relative pressure in main Pzn nominal number of revolutions, being &ee of load in the process. At the TIME=100 s the process of loading by condenser means of turboelectric moment of the synchronised Fig. 2. Simulation plane of turbine-generator set generator begins, which means that self excation of the III. CONCLUSION synchronised generator has started. It is soon brought to A realistic, or approximately realistic picture of an end, due to an opening of the compounding self qualitative and logical connection and interdependence excitation proportional regulator. between basic parameter of the unit observed, The simulation results displayed in Fig. 3. [2] clearly technological connection, limitation system and show that the initial drive of the turbine has taken place appropriate efficiency criteria have been shown by means at two levels, as follows: of non-linear differential equations used to describe the -10 - 50 s (the relative number of revolutions being 5%), turbine-generator set. - 50 - 100 s (100% of number of revolutions has been Each component has a value varying within limits of its attained). physical capacities [3] and technically feasible conditions This is due to the turbine components being evenly and designs, again within limits of technically permitted heated. At the time of 100 s onwards the synchronised initial and working conditions of materials used for generator has been excited under load which shows a equipment components (e.g.. steam pressure, constants of relatively rapid slow-down and decrease of the number a particular machine, etc.). By including a regulator in of revolutions, as the value of the generator outlet the synchronised generator circuit it is possible to voltage. This is achieved primarily due to the properties influence any transitional phenomena, and by doing so, of the compounding self excited regulator acting as a the quality of power delivered to the network. The proportional regulator as well as to the effectiveness of response characteristics are significantly altered by an optimum PID ( proportional, integral and simulated changes of certain parameters. This points to derivational regulator) of the steam turbine. the fact that it is not suff cient to merely acknowledge and determine the mathematical complexity of the OHE(8.,1.1 " ' " UfB.,2.1 problem: it is essential to obtain results dependent on the 1.   pSllt8.,2.)  UffB. 4.I data available and acceptable for practical application. . Tf0 P1 .. . nin  By using the simulation method it is possible to explore and explain the behaviour of a complex system at several levels (and from different viewpoints). Even most extreme exploration and research of propulsion conditions are thus made possible since this method presents no danger to the ship's system or people operating it. IV. REFERENCE [1] M. KrCum : Simulacijski model brodskog elektroenergetskog sustava , magistrate work, Faculty of electrotehnical and computing , Zagreb,1996. [2) A. Munitiє: Kompjuterska simulacija uz pomoc sistemske dinamike, Brodosplit, Split,1990. [3] A. F. Stronch, J.R. Smith: "Development of a simulation model of turbocharger diesel engine prime-movers for power B, 8. 28. 48.881 78.88f I88. 128. t98. 168, 188. system studies" , Department of Engineering, Kings College, 8. ?IHE UniversityofAberdeen, 1988. Fig. 3. 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