DGC Brushless Excitation - Emerson Process Management
DGC Brushless Excitation - Emerson Process Management
DGC Brushless Excitation - Emerson Process Management
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<strong>DGC</strong> <strong>Brushless</strong> <strong>Excitation</strong><br />
System Description<br />
4.3.a Voltage Control<br />
The Control and Protection Software implements the voltage control function of the <strong>DGC</strong>. Many of<br />
the characteristics of the controller are tunable by the user. Tuning constants are entered and<br />
modified using the <strong>DGC</strong> Configuration software. The block diagram below will aid in understanding<br />
the operation of the voltage regulator controller software.<br />
4.3.b Setpoint<br />
The voltage Setpoint is expressed as a fractional percent, ranging from 0.9 to 1.1. The value is<br />
raised or lowered using the Voltage Adjuster control switch. The rate of change is typically set for 1<br />
minute from minimum to maximum.<br />
fld_i_pct<br />
gen_mvars_actual<br />
gen_mw_actual<br />
tgr_value<br />
in_va_up<br />
in_va_down<br />
in_vapre(n)<br />
vhz_actual<br />
tgr_value<br />
line_w_actual<br />
line_vars_actual<br />
Maximum<br />
<strong>Excitation</strong><br />
Limiting<br />
Minimum<br />
<strong>Excitation</strong><br />
Limiting<br />
Voltage<br />
Set Point<br />
Volts Per<br />
Hertz<br />
Limiting<br />
Line<br />
Compensation<br />
mel_out<br />
va_volts_value Σ auto_error<br />
vhl_out<br />
mxl_out<br />
+ -<br />
+<br />
-<br />
-<br />
fb_comp<br />
Π<br />
pss_output<br />
-<br />
tgr_value<br />
Figure 4: Controller Block Diagram<br />
4.3.c Voltage Feedback Signal<br />
The Voltage Feedback Signal is a simple ratio of measured voltage to rated voltage. The Voltage<br />
Feedback Signal is passed through a dead band filter and modified by the compensators. The<br />
damping signal, the limiter outputs, and the power system stabilizer output (if installed) are summed<br />
with the f Voltage Feedback Signal and the setpoint to produce an error output. Each of the<br />
compensators and limiters are discussed in more detail in the following paragraphs.<br />
4.3.d Load Compensation<br />
Load Compensation is normally used when multiple generators of different types are operated in<br />
parallel on a common bus. The compensation is used to balance the reactive droop characteristics<br />
of the various machines to ensure that they share reactive load equally. The effect of the<br />
compensation is to make the apparent terminal voltage rise as the reactive loading of the machine<br />
increases in the over-excited direction. This causes the <strong>DGC</strong> to reduce the terminal voltage,<br />
transferring reactive load to the other machines. This function may also be used to compensate for<br />
a high impedance main transformer.<br />
Power<br />
System<br />
Stabilizer<br />
Proportional<br />
Action<br />
-10<br />
+10<br />
Integral<br />
Action<br />
Transient<br />
Gain Reduction<br />
gen_freq_actual<br />
Load<br />
gen_vars_actual<br />
Compensation<br />
Π gen_v_db Deadband Filter<br />
gen_v_pct<br />
i_output<br />
fld_i_pct<br />
p_output<br />
+<br />
+<br />
Σ<br />
-10<br />
+10<br />
Output<br />
ctlr_out<br />
Limits<br />
regulator_out<br />
© <strong>Emerson</strong> <strong>Process</strong> <strong>Management</strong> Power & Water Solutions. - 18 -<br />
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