Modular Solar Grid Tie Inverter - Grid Polarity Switcher Module

This is a grid-tie polarity switcher module meant for use in a modular solar grid-tie/on-grid inverter main board.

Eg. 1000W Main Board

Its a fully passive polarity switcher/unfolding stage/4Q rectifier. That means that it connects to the AC power grid, and automatically switches the polarity to keep its input section positive aka carry the absolute value of the voltage in the power grid.

Module is designed for 230/240 V nominal power grid and 50 Hz (for 120 V 60 Hz grid etc a lower voltage mosfets may be used and different timing component values must be selected)

This module enables DC-DC topologies to behave like DC-AC topologies and deliver power directly into the AC power grid.

Values of resistors R15 and R16, and zener diodes D7 and D8 set the gate drive timing to minimize current spikes when the power grid crosses zero and polarity switches. Given values are optimized for typical behaviour of IPD70R360P7S mosfets, for different types of mosfets a different set of values might be needed. For optimizing those values, the following simulation waveforms with capacitive load on the output may be useful: (zener BV is the breakdown of the zener diodes at roughly 200 uA of current, Rdis is the value of discharge resistors R15 and R16)

With the selected components this module is capable of delivering continuous current of 2.5Arms into the power grid. This module alone can support up to 4 Buck-Boost topology power conversion modules.

Module requires a M1.4 2mm long self tapping screw with M2 spring lock washer and M1.6x4x0.3 flat washer to create an electric connection to the aluminum substrate via X1.

It is recommended to use a non resettable 110 °C thermal fuse wedged into the heatsink to disconnect grid if module overheats.

The used heatsink is usually found as "heatsink black 40x40x11mm" on aliexpress etc.

3D printed box should be made from ABS of other high temperature resistant material.