Easun IGrid SS 3KW Plus, Service Manual, Page: 9 / 29

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3. Functional Block
As a hybrid photovoltaic inverter, the product utilizes several power sources. Comprising
functional blocks as shown in Figure 3.1
BOOST PV
BAT
Load
+
-
+
-
L
N
L
N
INV/REC
BUS
PV EMI INV EMI
AC EMI
INV Relay Safety Relay
O/P Relay
DSP MCU
RS232/USB
LCD
Parallel connection
SPS
PV
BAT
GRID
Figure 3.1 Function block Diagram
The CNTL block provides control signals to control the action of the inverter. It also
provides the communication interface for receiving and executing commands from users
via the panel or other communication protocol. When the inverter becomes abnormal, in
most case, the CNTL board can provide basic information indicating the status of the
inverter, and the information will be displayed on the LCD. The MCU and the DSP will
double check the frequency and voltage of grid, the inverter output DC current, the GFCI
signal and disconnect the inverter from the grid if any abnormal signal is generated by
turning off the safety relay.
The Input and Output EMI section provides EMI filter function. The input and output EMI
filters can prevent the PV Inverter from being interference by external electronic/magnetic
noise which is generated by other electronic system and prevent other systems from the
noise generated inside the inverter system.
The BOOSTER blocks are the PV input stage of the inverter. The block converts DC input
power generated by the Solar panels into DC power stored in the BUS capacitor. In the
meantime, BOOSTER will track maximum power point of solar modules by calculating the
input power through changing the input voltage.
The INV/REC block is the output stage of the PV Inverter and this block is a bidirectional
power flow block. It can convert DC power from the BUS capacitor to AC power to the load
or to the grid. It can also convert the AC power from the utility to DC power at the DC BUS
and arrive at PFC at the same time. When the maximum power point of PV input is above
370Vdc, the boost will turn off and the PV input current will be sent to the BUS directly.
That means the input PV voltage is same as the BUS voltage. At the same time, the
INV/REC block controls the BUS voltage and will track maximum power point of solar
modules.