I discussed with a DC-block BESS company about pairing their product with a 480VAC-1500VDC Power Conversion System (inverter).
They have a requirement for an AC-side, ungrounded isolation transformer. The DC-side also operates ungrounded which is expected. They said it was because of common mode voltage that they require the isolation transformer.
I would like to take the PCS and directly interconnect at 480V to facility grounded distribution similar to how it is commonly done with PV, without a dedicated 480V to 480V ungrounded secondary isolation transformer.
As I see it, the ungrounding of the secondary changes the distribution served by the inverter to capacitively-grounded. It would cut down on common-mode current a bit but I don’t see how it significantly affects anything when the DC-side is ungrounded to start with very short conductors connecting to the inverter (very low capacitance +\- to ground on the DC-side).
Am I missing something with what the isolation transformer is doing? And, how is this application different from VFDs, PV inverters, and AC-block BESS which do not require it? Is the DC-block BESS manufacturer being overly cautious?
They have a requirement for an AC-side, ungrounded isolation transformer. The DC-side also operates ungrounded which is expected. They said it was because of common mode voltage that they require the isolation transformer.
I would like to take the PCS and directly interconnect at 480V to facility grounded distribution similar to how it is commonly done with PV, without a dedicated 480V to 480V ungrounded secondary isolation transformer.
As I see it, the ungrounding of the secondary changes the distribution served by the inverter to capacitively-grounded. It would cut down on common-mode current a bit but I don’t see how it significantly affects anything when the DC-side is ungrounded to start with very short conductors connecting to the inverter (very low capacitance +\- to ground on the DC-side).
Am I missing something with what the isolation transformer is doing? And, how is this application different from VFDs, PV inverters, and AC-block BESS which do not require it? Is the DC-block BESS manufacturer being overly cautious?
