There may be issues for 150A inverter output. As I understand it 'sketchy' has:
600A main service
possible 600A meter
Distribution buss
200A meter for apartment
200A OCPD
connection for panel
This is likely a meter stack (modular metering), and if such it is not listed for any internal connections.
The possible issues are:
-- The ratings of the distribution buss to the 200A meter and 200 OCPD and the 120% rule[690.64/705.12(D)(2)];
-- Rating of the connection for the distribution panel an application of the 120% rule to that.
Only obvious place to connect is the 200A OCPD. Required ampacity of the connection is (200+150)/120% = 291.7A. Depending on other factors, that is 300mcm or larger that the OCPD must accept. If you have smaller wire, sized only for 200A, you have to replace it.
Then check the ampacity of the line side buss going to the 200A meter. If not sized for 291.7A, you have an issue. Internal buss is seldom specified and may have to be calculated or consult the factory. The question becomes 'At what point does the 200A service start?'.
I had this issue to deal with for 120A inverter connected to 200A OCPD (serving loads) on a no main device service entrance and had to apply the 120% rule to all cables from the 200A SES OCPD to the AC combiner panel. AHJ did not question the internal buss rating.