# What is the role of the Op-Amp integrator in this circuit?

Helo dier community! I got a 400 Hz broken Power Inverter and reverse-engineered the circuit just for the simplicity of repairing it. Then I got deeper in and started to understand the engineering principle of the circuit. But I em stuck on this Op-Amp integrator build in and his role in this circuit. It would be nice if you could help me to understand his role. If you need some Voltage references I can provide it. The circuit is a simulation in Multisim and fully running.