GovCT1 : Documentation diagram
Created: |
30/03/2012 09:30:24 |
Modified: |
18/05/2014 21:57:31 |
Project: |
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Author: |
pcha006 |
Version: |
1.0 |
Advanced: |
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ID: |
{60B40F19-5A47-43ea-A012-81B1DD2003D6} |
<font color="#0f0f0f"><b>Parameter Notes:</b></font><br/><ol>
<li>Per unit parameters are on base of <b>MWbase</b>, which is normally the MW capability of the turbine. </li><li>The range of fuel valve travel and of fuel flow is unity. Thus the largest possible value of <b>Vmax</b> is 1.0 and the smallest possible value of <b>Vmin</b> is zero. <b>Vmax</b> may, however, be reduced below unity to represent a loading limit that may be imposed by the operator or a supervisory control system. For gas turbines <b>Vmin</b> should normally be greater than zero and less than <b>Wfnl</b> to represent a minimum firing limit. The value of the fuel flow at maximum output must be less than, or equal to unity, depending on the value of <b>Kturb</b>. </li><li>The load limiter module may be used to impose a maximum output limit such as an exhaust temperature limit. To do this the time constant <b>Tfload</b> should be set to represent the time constant in the measurement of temperature (or other signal), and the gains of the limiter, <b>Kpload</b>, <b>Kiload</b>, should be set to give prompt stable control when on limit. The load limit can be deactivated by setting the parameter <b>Ldref</b> to a high value. </li><li>This model includes a simple representation of a supervisory load controller. This controller is active if the parameter <b>Kimw</b> is non-zero. The load controller is a slow acting reset loop that adjusts the speed/load reference of the turbine governor to hold the electrical power output of the unit at its initial condition value. This value is stored in the parameter <b>Pmwset</b> (which equals Pe, initial generated power) when the model is initialized, and can be changed thereafter. The load controller must be adjusted to respond gently relative to the speed governor. </li><li>The parameters <b>Aset</b>, <b>Ka</b>, and <b>Ta</b> describe an acceleration limiter. <b>Ta</b> must be non-zero, but the acceleration limiter can be disabled by setting <b>Aset</b> to a large value, such as 1. </li><li>The parameters <b>Tsa </b>and <b>Tsb</b>, are provided to augment the exhaust gas temperature measurement subsystem in gas turbines. For example, they may be set to values such as 4., 5., to represent the ‘radiation shield’ element of large gas turbines. </li><li>The parameters <b>Rup</b> and <b>Rdown</b> specify the maximum rate of increase and decrease of the output of the load limit controller (<b>Kpload</b>/<b>Kiload</b>). These parameters should normally be set, or defaulted to 99/-99, but may be given particular values to represent the temperature limit controls of some GE heavy-duty engine controls. </li><li>The fuel flow command <b>fsr</b> is determined by whichever is lowest of <b>fsrt</b>, <b>fsra</b>, and <b>fsrn</b>. Although not explicitly shown in the GovCT1 diagram, the signals that are not in control track <b>fsr</b> so that they do not “windup” beyond that value. This represents GE gas turbine control practice but may not be true for other controller designs. </li><li>As shown in the GovCT1 diagram, when <b>Kpgov</b> is non-zero, the governor PI control is implemented to “track” <b>fsr</b> to prevent windup when <b>fsr</b> is limited by another signal (<b>fsrt</b>, <b>fsra</b>) or <b>Vmax</b>/<b>Vmin</b>. If <b>Kpgov</b> is zero, the integral path is implemented directly. The same applies to the load limiter PI control with regard to <b>Kpload</b>. </li></ol><p/>