How to sustain power charges on bosses as Invoker

I use storm wave for my main damage source. It's backed by herald of thunder with the electrocution support that builds electrocute which generates frenzy charges that are then converted to power charges using the resolute atlas node. Then I use charged staff for additional dps while mapping.

This works well except on bosses because I can't generate power charges since there are no minions spawning to trigger herald of thunder.

I tried swapping the electrocution support onto tempest flurry to electrocute bosses and then swapping it back, but it is very cumbersome and I'd like to avoid it.

Is there a more reliable way of generating power charges? Preferably without dipping into cold damage.

Edit: Forgot to mention that I am SSF BTW.