Off-grid inverter RCD nonlinear load limit, parallel issues and NEC RSD requirem

Hi everyone,

  I’m testing hybrid energy storage inverters for off-grid and US market projects. I found a common phenomenon: the inverter can run full power with pure resistive R load, but it will hit protection, high THD or voltage distortion much earlier under RCD nonlinear loads (switching power supplies, adapters, electronics).

I know RCD load has sharp current spikes, which is harder for the control loop than resistive or inductive loads. I want to ask:

• What is your practical test standard for off-grid RCD load limit? What THD threshold do you use as pass criteria?
• When multiple inverters are paralleled in off-grid mode, sometimes we get circulation or unstable voltage. Is the DIP switch address setting and terminal resistor matching the key point?
• For US NEC 690.12 projects, Tigo RSD is mandatory. Have you met any compatibility issues between RSD modules and hybrid inverters?
• About PE ground connection: in off-grid mode, neutral-ground relay control logic is critical, wrong setting will cause GFCI fault. Any debug tips?
  

  Also, many customers add diesel generator as backup. The dry contact signal between generator and inverter, pulse signal vs battery level signal, which one is more reliable?

Thanks for sharing your site experience.