The goal of the simulator scaling is to make the models r epresent, as close as possible, the behavior of the real system.
In addition to the following EE settings, see EE.3850 GMJMPR in Generator, exciter, and regulator parameters listed in Chapter 4 (General Configuration) in the section Configuration and Scaling Example, will be used for scaling discussions in the simulator section.
SMVDCL0 EE.1558 simulates the dc link voltage of the regulator. It is set to represent the actual running voltage of the dc link. For the example system this is 137 V dc. For EE.1558, set equal to 137/360 * 20000 = 7611 counts.
SMHST0 EE.1559 is the simulated heat sink temperature of the PWM IGBT heatsink. This value can be used to test the overtemperature alarm and trip levels in the regulator controls. One count equals 1 °C. Normally set to maximum expected
temperature during operation, 60°C.
GMVBAT EE.3851 represents simulator flashing voltage. Since flashing is not required on the regulators, set EE.3851 = 0.
GMRBAT EE.3852 represents simulator battery resistance for field flashing. This is also not required in the regulator and EE.3852 is also set to a 0.
GMVTHY EE.3853 is the simulator thyrite voltage. This models an overvoltage protection thyrite connected across the exciter field input. The example system has a
125 V exciter field. Set EE.3853 = (Exciter field class*7.2*1797)/(DC link volts) = (125*7.2*1797)/137 = 11805.
GMRDIS EE.3854 simulates the dynamic discharge resistance. Set EE.3854 = (AFNLex*2*RDD*30664) / DC link volts = (3.52*2*17*30664)/137 = 26787. GM_RFE EE.3855 is the simulator exciter field resistance. This is set equal to (VFNLex/DC link volts) * 31108 where VFNLex = AFNLex * Rfe@25C. From the example data Rfe@25c = 4.871 ohms. VFNLex = 4.871 * 3.52 = 17.15 V dc. Set EE.3855 = (17.15/137)*31108 = 3838.
GEH-6375A User's Guide Chapter 6 Simulator Scaling and Operation • •• • 6-3
GMILFE EE.3856 represents the inverse of exciter field inductance. EE.3856 is set equal to (DC link volts * 156) / (VFNLex * T’doex). T'doex is the open circuit field time constant which is 0.35 seconds in the example system. Set EE.3856 =
(137*156) / (17.15 * 0.35) = 3561.
GM_RFG EE.3857 simulates generator field r esistance. This parameter is normally set to 7115 * frequency/60. The constant scaling is the result of expected
normalizations. Exciter AFNL is expected to produce VFNL on the generator field, which in turn produces AFNL on the generator field. Set EE.3857 = 7115 for the example, which is a 60 Hz system.
GMILFG EE.3858 is the simulated inverse of generator field inductance. Set equal to (60/ frequency) * 670 / T'dogen, where T'do is the main generator field time constant. Set EE.3858 = 670/5.615 = 119 for the example system.
GMVFES EE.3859 is the simulator exciter voltage scale down divider. This scales the exciter voltage from the model to produce EXSIMFE VAR.1177 (simulated exciter field voltage). Set EE.3859 = 5888 * maximum dc link volts / dc link volts = 5888 * 360/137 = 15472.
GMIFES EE.3860 is the simulator exciter current scale down divider. This
parameter scales the exciter current from the model to make EXSIMIFE VAR.1176 (simulated exciter field current). Set EE.3860 = (AFFLex/AFNLex)*3146 =
(3.52/9.54)*3146 = 8526.
GMVFGS EE.3861 is the simulator generator field voltage scale down divider. This parameter scales generator field voltage from the model to make EXSIMVFG VAR.1163. Set GMVFGS to 27329280/ (AFNLgen * RFG@100 C* 20000 /
Maximum DC link volts). In the example system, and simplifying the formula, this is 1367 * 360 / (313*0.256) = 6139.
GMIFGS EE.3862 is the simulator generator field current scale down divider. This parameter scales generator field current from the model to make EXSIMIFG
VAR.1161 (simulated generator field current). When used in conjunction with standard scaling, such as AFFL = 5000 counts, set GMIFGS = (AFFLgen / AFNLgen ) * 3146. In the example system, this would be 846/313*3146 = 8503. GMIFLS EE.3863 represents the simulator flashing current scale down divider. This parameter is not used in the regulator. Set GMVIFLS = 0.
GMDAMP EE.3864 is the simulator generator model damping factor where 1 count = 0.11 pu watts/pu speed(60 Hz). Normally EE.3864 is set equal to 400. If
oscillations occur while operating in simulator mode, try changing GMDAMP. GM_IXS EE.3865 represents the generator model inverse of s ynchronous reactance. This parameter models the generator synchronous reactance in simulator mode. GM_IXS = 4096/Xs(pu).
To most accurately model the generator, it is n ecessary to approximate the generator synchronous reactance from no load to full load. In a real system, machine
reactances vary with saturation and saliency. Therefore it is n ecessary to make simplifying assumptions that produce a value of Xs that provides reasonable behavior over the range VFNL to VFFL. Assume a round rotor machine with no
saturation, no saliency, and resistance is negligible. This makes the direct and quadrature reactances equal. If this level of accuracy in the model is not of concern then Xd (the direct axis saturated synchronous reactance) can be used.
If optimum model accuracy is of con cern then the following method, based on a simplified synchronous machine model, can be used. The range of field amps from no load to full load = AFFL/AFNL=9.54/3.52 = 2.71.
6-4 •• • • Chapter 6 Simulator Scaling and Operation EX2000, PWM Digital Regulator GEH-6375A
If a phasor diagram showing the machine operating at rated load and power factor connected to an infinite bus a t rated terminal volts is drawn then a quadratic equation with the synchronous impedance as the unknown quantity can be generated and solved for Xs. It is then used in the above equation for GM_IXS.
The rated power factor for the sample machine is 0.85. With the machine operating at rated k VA = 1 pu k VA then rated real power = 0.85*1 pu and rated reactive power output = 0.53*1 pu Generator voltage = 1 pu
As per unit values are being used it is not necessary to use the actual generator MW and MVAR values involved.
From the phasor diagram, the following quadratic equation results where the generator internal voltage range required is represented by the ratio of AFFL to AFNL = 2.71
(2.71)**2 = (1 + 0.53*Xs)**2 + (0.85*Xs)**2 Solving for Xs gives a synchronous reactance of 2.04 pu
Set EE.3865 equal to 4096/Xs = 4096/2.04 = 2007.
GMXEXS EE.3866 models the effect of external r eactance for the simulator
generator model. This can be set for a strongly or weakly conn ected system. EE.3866 is set equal to 65536*Xe/(Xs + Xe) where Xe represents the amount of impedance in per unit connecting the generator to the system. For the example, set for a strong
system (small amount of impedance between generator and system), with Xe = 0.1 pu, then EE.3866 = 65536*(0.1)/(2.04 + 0.1) = 3062.
GM_IM EE.3867 models the effect of gen erator inertia for the simulator. Typically, the default value of zero (which is equivalent to M = 3.98 pu) is used. For more accurate simulator modeling, EE.3867 can be set to (frequency/60)*16302/M where M =2H, the generator inertia constant.
Operation
To put the control core into simulator mode set EE.570.0 = 1. The shaft speed of the generator increases to rated (synchronous) speed at a rate determined by the
simulator inertia constant and the level of sha ft torque preset in register EE.84. The value of torque preset to give rated speed at no load is 153 * (frequency/60). Rated speed is indicated on the core programmer display as 100%. The shaft torque can be altered on-line or off-line by changing the value stored in EE.84. Offline, changing shaft torque increases the speed and h ence the frequency of the generator. Changing the torque on-line increases or decreases the r eal power output of the model
generator.
To start the simulator, it is generally necessary to wait until the simulated generator speed is above 95%. It is also necessary to have the 86G input to the r egulator closed. Failure to do so will result in a fault 29 when attempting a start. Starts in auto or manual regulator are permissible. The simulator can be started from the operator's station or by pressing the RUN button on the LDCC keypad. After starting, exciter field current and voltage and g enerator terminal voltage will build up to the preset levels of the regulator being used.
Once the simulator is on-line, the 94EX contact output can be operated inadvertently. This may cause unintentional operation of protective devices outside the regulator. Lifting of the 94EX output contacts is recommended during simulator operation.
GEH-6375A User's Guide Chapter 6 Simulator Scaling and Operation • •• • 6-5
To put the simulator online, a contact closure simulating 52G aux contact feedback must be input to core LTB input IN1. Some oscillations are generally observed when closing the 52G contact since there is no synchroscope to confirm closing while the simulated generator and line voltages are in phase. When offline, changing the exciter AVR or MVR setting adjusts generator terminal voltage. When online, raise or lower signals change the generator VARs. The result of these control changes can be observed.
Testing of UEL settings, V/Hz regulator, over current protections, and so on, can also be observed. Feedback and control signals from the operator's station and 4-20 ma outputs (if supplied) can also be observed.
When stopping the simulator, the reference value in EE.84 should be returned to the original level for 100% speed off-line. Failure to do so will result in unusual offline operation.
6-6 •• • • Chapter 6 Simulator Scaling and Operation EX2000, PWM Digital Regulator GEH-6375A
GEH-6375A User's Guide Glossary of Terms•• • • 1