Paralleling a Synchronous Machine with the Grid

⦁ Procedure, Measurements, and Calculations
⦁ Make the connections and wirings between components of the raw file as shown in Figure ‎3.1.
⦁ Make sure the breaker’s command switch (sliding switch in Figure ‎3.5 is in the off position)
⦁ Set the stop time of the simulation to 500 seconds.
⦁ Set the wref signal in Figure ‎3.2 to 1 (pu).
⦁ Set the slider in Figure ‎3.2 to 0 (MW). This will turn the constant-source block on the left side of the gain block (1/200) to zero, which will set the Pref setting of the plant to 0 before paralleling it with the grid.
⦁ Run the simulation and watch the Display Blocks (‎2.1.6) as well as the Scopes ‎2.1.7).
⦁ Before synchronization:
⦁ The f-plant plot goes below 60-Hz and settles at a smaller frequency (around 59.96 Hz).
⦁ Notice the difference between average RMS values of the voltages on the two sides of the breaker before paralleling. You may need to zoom into the second plot (V_plant vs. V_grid) to note the difference.
⦁ Note the variations of the third plot (Angle Difference Index) between 0 and 2.
⦁ The fourth plot (P plant) will settle to 5 MW, since the plant must feed its 5-MW local load (before paralleling, the plant is the only source that can feed the local load). However, since before paralleling, the Pref setting in the plant is 0, and the load of the plant is 5-MW, the frequency of the plant settles to less than 60-Hz, since the generator becomes overloaded.
⦁ As an operator, you may command closing of the breaker at around 40 sec, when you see the frequency of plant settles close (but not equal to) 60-Hz.
⦁ During synchronization:
⦁ The synchronization logic monitors the difference between the voltages on the sides of the breaker based on the logic explained in ‎2.1.8. As soon as the difference becomes smaller than the 0.001 pu threshold, the signal y in Figure ‎3.10 turns to 1, therefore setting the “Close Breaker” command to 1.
⦁ After synchronization:
⦁ The frequency of the plant will settle to 60-Hz.
⦁ The V_plant and V_grid signal will be equal.
⦁ The third plot (Angle Difference Index) will be settled to zero.
⦁ The fourth plot (P plant) will start reducing to zero (since Pref of the plant is at 0). Start increasing the slider in Figure ‎3.2 from 0 (MW) to 5 (MW) in 3-4 steps and watch increasing the delivered power by the plant. This means that the operator wants the local load to be supplied by the local plant, while the plant has already been synchronized with the grid.