I'm not sure what you mean by PD (PV? photovoltaic?). The fact that you're quoting a power rate (30W) rather than a power capacity (ampere-hours, or milli-ampere hours) makes me think that this might be photovoltaic power generation equipment (solar cells). Photovoltaic cells by themselves are often temperamental when it comes to charging electronics - in the case of connecting my iPhone to a solar power cell I have found that it often won't work unless the solar cell is in strong sunlight, exposed at just the right angle, and not interrupted by shadow, or the iPhone will reject it; the iPhone not only judges the voltage level and current availability, but also the stability of the source (no drop-outs).
Do the power banks charge other non-Apple equipment, like Samsung phones or Bluetooth speakers? If so, it might also be incompatible with Apple equipment. Different manufacturers like Apple or Samsung use different hardware coding involving the resistive pull-ups and pull-downs on the data lines of the USB interface to signal compatibility, and perhaps your iPad reads the coding from the power bank and says "Nope, not Apple equipment, not gonna charge with this." If that is the case, there really aren't any settings for you to change on the iPad, it just won't work.