Modular Solar Grid Tie Inverter - Inverter Control Module

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

Eg. 1000W Main Board

It contains grid protections, including peak and mean overvoltage protection and grid frequency deviation protection. Designed for 230 V 50 Hz nominal grid, peak voltage protection is set to roughly 383 Vp and mean voltage protection is set to roughly 255 Vrms. Frequency protection checks if the frequency is within +-4% of the nominal value. Different voltage thresholds can be set by changing the value of R1. 60 Hz nominal can be set by using 82nF C0G capacitors C2 and C4 instead of 100nF C0G ones. Trimmer TR1 fine tunes the nominal frequency setting.

Activation of any protection resets the FB signal to maximum voltage = minimal/zero output power.

Additionally it contains power control current sink CC signal, which is reversly propotional to the voltage on FB signal. It also contains 150 uA current pullup for the FB signal with input low voltage limit set to rougly 120 VDC. R17 and R27 set the minimal FB signal level, which sets the minimal output power with fully lit panels for the MPPT function to kick in.

FB signal requires external integration capacitor network connected to 5V for proper operation.

LED1 glows red when any of the protections get triggered. LED2 glows yellow when CC signal saturates, aka the inverter is power limited (maximum CV reached on all modules).

Module creates stable 5V power and reference voltage for inverter control circuitry. It uses Vaux supplied from power conversion modules, which is roughly 7.5V.