Αναλυση δυναμικης συμπεριφορας συνδυασμενου κύκλου

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<p> . </p> <p> : . ...</p> <p>, 2005</p> <p> . </p> <p> : . ... 4 2005............................. . ... ............................ . . ...</p> <p>............................. ...</p> <p>, 2005</p> <p>................................... . ...</p> <p>Copyright . . All rights reserved. , , , . , , , . . .</p> <p>3</p> <p> . Simulink Matlab. , , . , , , . , , . . , . . . . , . ( , ) . . , . , ( ) . (100% ) , , . , 10% ( ).</p> <p>4</p> <p>AbstractThe subject of this diploma thesis is the development of a dynamic model for a single-shaft combined cycle plant and the analysis of its response to electrical load and frequency transients. In particular the stability of the frequency control is investigated. The model is developed in the Simulink environment of Matlab. During the last decades there has been continuous development of combined cycle power plants due to their increased efficiency and their low emissions. The dynamic response of such power plants to load and frequency transients is rather problematic, since the compressor, as well as the fuel supply system, is both attached to the shaft of the unit. Thus rotor speed and frequency has a direct effect on air and fuel supply, which introduces a negative effect on system stability. Two control loops are introduced so that the unit functions properly. The first loop is the speed/load control, which detects frequency deviation from the nominal value and determines the fuel demand signal. The second loop is the gas temperature control and consists of two branches. The normal temperature control branch acts through the air supply control. For instance, when the temperature of the exhaust gases exceeds its reference value, this controller acts on the air valves to increase the airflow, so as to decrease exhaust gas temperature. In certain situations, however, this normal temperature control is not enough to maintain safe temperatures. Thus, in cases of a severe overheat the fuel control signal is reduced through a low-value-select function that determines the actual fuel flow into the combustion chamber. Inputs to the low-value-select are the fuel demand as determined from speed-frequency control and a temperature control variable that is initially high, but decreases while the exhaust temperature exceeds its reference value. Using the above model various types of disturbances were simulated (step variation of electrical load and frequency, as well as ramp variations of electrical load). The obtained responses, as well as the calculation of system eigenvalues, demonstrated the significance of the low value select function in order to maintain stability. In particular, when the low-valueselect deactivates the speed control, the system becomes temporarily unstable. Thus, a necessary condition for the system to achieve a steady state after a disturbance, is that the low-value-select reactivates the speed/load control soon enough. In this respect, air control is a crucial factor for temperature control, and thus of stability, because its function allows the increase of power output without overheat, thus helping restore frequency control. There are also presented cases of unstable behavior of the system due to limited capacity of the airflow control valves, as well as cases determining the maximum allowable rate of load increase, or load reduction.</p> <p>5</p> <p> . . , , . , . </p> <p>6</p> <p> 1 ........................................................................................91.1 ............................................................... 9 1.2 ............................................................... 10 1.3 ...... 11 1.4 ....................................................................................................... 12 1.5 ............................................................................. 14 1.6 .............................................................. 15</p> <p> 2 .....................................172.1 ............................................................................ 17 2.1.1 ..................................................................................... 17 2.1.2 ........................................................................................................................... 18 2.1.3 ...................................................... 19 2.1.4 - .............................................................. 19 2.1.5 ........................................................... 21 2.1.6 ........................................................................................ 22 2.1.7 ......................................................................................... 23 2.1.8 ..................................................................... 26 2.2 .................................................................................................... 29 2.2.1 .................................................. 30 2.2.2 ........................................................................... 30 2.2.3 .............................................................. 32 2.2.4 ........................................... 33 2.2.5 ......................................................................... 36 2.3 ..................................................................................................... 39 2.3.1 ..................................................................................................................... 39 2.3.2 ........................................................................................ 40 2.3.3. ........................ 42 2.4 ................................................................................... 46 2.4.1 ..................................................................................................................... 46 2.4.2 ................................................. 47 2.4.3 ........................................................................... 48 2.4.4 ......................................................... 49 2.4.5 .................................... 50 2.4.6 ................... 51 2.5: .................................................................... 52 2.5.1 ..................................................................................................................... 52 2.5.2 ............................................................................................... 53 2.5.3 ...................................................... 54 2.5.4 .............................................................................................................. 55 2.5.5 .......................................................................................... 56</p> <p>7</p> <p> 3 ..........................................................................583.1 ................................... 58 3.1.1 ....................................................................... 60 3.1.2 ........................................................................................ 63 3.1.3 .............................................................. 63 3.1.4 .......................................... 64 3.1.5 ......................................................................................... 66 3.1.6 () ............................................................. 67 3.1.7 ...................................................... 67 3.1.8 ............................................................. 69 3.2 ....................................................................... 71</p> <p> 4 ..............................................................................................................724.1 SIMULINK.......................... 72 4.1.1 simulink ................................................................. 72 4.1.2 ................................................................................................................ 75 4.1.3 ......................................................................................................... 77 4.2 ..................................................................... 80 4.2.1 .......................... 80 4.2.2 ............................... 82 4.3 ............................. 85 4.3.1 ........................................................................................... 85 4.3.2 ............................................ 85 4.3.3 .................................... 88 4.3.4 4.3.2-4.3.3 ..... 91 4.3.5 ........................................... 96 4.3.6 ........................................................................................... 98 4.3.7 . ..................................................................................................... 100 4.3.8 0.1 .. ...................................................... 101 4.3.9 0.2 ......................................................... 103 4.3.10 .......................................................................... 105 4.3.11 ........................................................................... 108</p> <p> 5 .........................................1105.1 ................................................................................................... 110 5.2 ............................................................................. 112</p> <p> .....................................................................................................114 .........................................................................................................116</p> <p>8</p> <p> 1 1.1 , , . , . 19 1950 16.100 TWh, 1970 65.600 Wh [22]. . , . , (...)[16]. . . , . ... , . , , . ... . , , . , , , , . ... , , . . , ... . , . (. 4 ) .</p> <p>9</p> <p>1.2 , . , . . . . . , . . 6000 K 288 . , . 0.5m ( ) 10.3m () [21]. CO2, H2O, CH4, N2O . . . , . 1960 1990 1.1 [21].</p> <p>10</p> <p> 1.1 CO2 , , . , . , . . 1997 , . , . , (, , ), , . , .</p> <p>1.3 . 6% 2020 [14]. 1.1 [22]. . </p> <p>11</p> <p>. , . . 1.1: , . KWh CO2 (gr) 830 380 CO (mg) 75 34 SO2 (mg) 600 0 2 (mg) 600 350 (gr) 34 0</p> <p>1.4 ... ..., . , , , . , , . . </p> <p>[ x] = [ f ( x, u )]</p> <p>(1.1)</p> <p> x , nx1 u , nx1 f nx1 , , , . , . . : [x] [x0]. . [x0] .</p> <p>12</p> <p> : () ( ). , . . f [x0]. f Taylor :</p> <p>1 f ( x) = f ( x0 ) + ( x x0 ) f '( x) x = x + ( x x0 ) 2 f ''( x) + ... x = x0 0 2</p> <p>(1.2)</p> <p> [x] [x0] , [18]. :</p> <p>f = f '( x) x = x x0</p> <p>(1.3)</p> <p>f = f ( x) f ( x0 ) x = x x0 (1.1) :</p> <p>(1.4) (1.5)</p> <p>x = f ( x, u ) (1.3) </p> <p>(1.7)</p> <p>f ( x, u ) =</p> <p>df ( x, u ) df ( x, u ) x + u dx x = x0 du x = x0</p> <p>(1.8)</p> <p> (1.7)-(1.8) </p> <p>x =</p> <p>df ( x, u ) df ( x, u ) x + u dx x = x0 du x = x0 [x] = [ A][x] + [ B][u ]</p> <p>(1.8)</p> <p>(1.9)</p> <p>a ij =</p> <p>f i x j</p> <p>(1.10)x = xo</p> <p>13</p> <p>bij =</p> <p>fi z j</p> <p>(1.11)x = x0</p> <p> (1.1) (1.9). (1.1) (1.9). , i, [] . , . Im(i)=0 Im(i)0 . </p> <p>det [ i I n A] = 0</p> <p>(1.12)</p> <p> [] , , . [u]: [v]:</p> <p>[ A][u ] = [u ]</p> <p>(1.13) (1.14)</p> <p>[ A] [v ] = [v ]</p> <p> i () , (participation factor) xi . pik = uik vik (1.15) (pik) , . . , . . .</p> <p>1.5 , . [1]-[6]. [1] , </p> <p>14</p> <p> [2] . [10], [11], [19] . , , . ( 3 ) [12]-[15] . [16]-[17] ... , -. [7]-[9]. , , . [18], [20] , . [22] [21] [23] . , .</p> <p>1.6 , , , . . . , . , . , . , ...</p> <p>15</p> <p> . , [2] [1] . , . , . , Simulink Matlab. , . , . , , , , , . . , . .</p> <p>16</p> <p> 2 2.1 , . ( ) , .</p> <p> 2.1: 2.1 ( ). ( , , , , ) .</p> <p>2.1.1 . (2.1) [11].</p> <p>dU = dQ - dW</p> <p>(2.1)</p> <p> U : [10] Q W </p> <p>17</p> <p> , , dQ dW, dU (2.1) [11]. . , , . () . .</p> <p>2.1.2 . , . F , 2.2 .</p> <p>ds</p> <p> 2.2: (ds) </p> <p>dW= F ds A , p :</p> <p>(2.2)</p> <p>p= (2.2) </p> <p>F F = pA A</p> <p>dW = Fds = pAds Ads . 18</p> <p>:</p> <p>dW= pdV</p> <p>(2.3)</p> <p> ( )...</p>

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