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It is recommended that the input voltage of the DC battery of two PCS units sharing
a transformer in the MV system be controlled within 100V, and excessive voltage
difference will affect the performance of the parallel system.
It is recommended that the power dispatching mode of two PCS units sharing a
transforme in the MV system should be consistent, the charge and discharge
modes should be consistent, and the active mode or reactive mode should be con-
sistent. Mixing of charging and discharging, active and reactive power is
prohibited.
VSG Mode
VSG (Virtual Synchronous Generator) control combines the PCS control and synchronous
generator control. It borrows the control methods of ordinary pcs and conventional synchro-
nous generator in terms of control policy. From the perspective of external input and output,
the PCS is equivalent to a synchronous generator. Essentially, VSG frequency droop control
is controlling active power output based on a specific droop slope according to frequency
changes. Running parameters that can be set in the VSG mode include output voltage set
value, output frequency set value, active power setting, reactive power setting, frequency
droop factor, and voltage droop factor.
The VSG mode can be set via the PC interface or WEB. The VSG mode has two operation
states: on-grid state and off-grid state.
In the on-grid state, the PCS automatically detects grid voltage signals, and performs opera-
tions synchronous with the grid. The on-grid active power and reactive power can be ad-
justed via active power setting and reactive setting respectively.
In the off-grid state, the PCS exports AC voltage and create a voltage source within a specif-
ic frequency range, so as to supply power for the load. In the off-grid state, the amplitude
and frequency of the output voltage with no load can be set by setting the output voltage set
value and output frequency set value.
10 PCS Functions System Manual
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