Copper carbonate, as shown here, is not very soluble in water so with high copper concentrations adding soda ash (sodium carbonate) could precipitate copper carbonate.

If you want to raise the pH without this effect, you can use 20 Mule Team Borax instead, but keep in mind that with high copper levels a higher pH can cause copper oxide or copper hydroxide staining.

It would be better for you to keep the pH low and add the metal sequestrant before trying to raise the pH.

Richard