System description
UM1016
16/19
Doc ID 18125 Rev 1
Figure 21.
Control state “Grid Insertion”
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After a few seconds the bus undervoltage protection triggers and the relay switches
again to disconnect the system from the grid.
If the steps in this procedure are correctly performed, with the inverter generating a clean
sinusoidal voltage waveform, the system is ready to be actually connected to the grid and
current injected at 230 V and 50 Hz.
Current injection can be started by following the procedure below:
Closed loop with coupling inductor
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Disconnect all the cables previously connected to the grid
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Connect the coupling inductor to J9 on the relay board
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Connect the power supply board to the grid
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Reset the microcontroller
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Connect the power cable to the grid and switch on the circuit breaker
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Run the calibration function, navigating the display. When the calibration function is
executed the display shows a grid current offset of about 2.5 V and a grid voltage offset
of about 1.8 V. Do not start the closed loop operation if the offset values are not close to
the values specified above.
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Navigate the display to the closed loop string
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Set the DC input voltage to 170 V (disabled) and connect it to J7 (power board)
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Enable the DC source
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Press start
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The DC-DC section starts switching, slowly charging (burst mode) the DC intermediate
bus up to 380-420 V (it is suggested to monitor the DC bus voltage with a multimeter)
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Then the inverter section starts switching
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If the grid voltage is in the proper range (190-265 Vac) then the grid relay is closed
automatically. At this point the system is grid connected.
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The system injects a few tens of Watts into the grid
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To increase the current injected into the grid you can either:
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Increase the DC source voltage
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Increase the phase shift value on the DC-DC converter control menu.
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