[Moderator note: This is a follow-up to a post by Coulomb in the PIP-4048MS and PIP-5048MS inverters topic
Here is the power flow topology for the PIP-4048, from "Axpert MKS-4000/KS-5000 Service manual"
, which I found on the web:
As actually implmented:
The battery is at the left, at the terminals marked P1. The AC loads appear at the right, at the terminals marked L and N (Line and Neutral). Note that one of the "switches" is actualy a diode, and the buck switch is actually in the bus negative rail, rather than the positive rail.
The two full bridge converters at the left convert the ~50 V of the battery to ~400 V. This flows through inductor 15 and S12 (S10 is off when inverting) to Vbus. The "output capacitor" I mentioned in my previous post is marked Vbus. The full bridge on the right converts this ~400 VDC to 230 VAC. The full bridge appears to be a generic diagram, not intended to represent specifics of the PIP inverter (which uses IGBTs not MOSFETs, and one not two large inductors L1/L2).
So the question remains: what happens if a grid interactive inverter is connected across the PIP's loads, and generates more power than the loads absorb. Again, Vbus will rise in voltage, but now there is a power flow path from Vbus to the battery. I don't know what will happen. My guess is that the PIP will prevent power flow, even unintended power flow, from Vbus to the battery (in battery mode). If it did allow this power flow, then all of the excess power from the grid interactive inverter (and there could be many kilowatts of this at times) will flow to the battery, with no way of regulating the power flow or the battery voltage.
So my answer remains much the same: I can't see a way of making this work unless there is a good system for ensuring zero power is "exported" to the PIP inverter. Even then, I'd be dubious that it could be made to work, but there may be a way I haven't thought of.
[ Edit March 2021: see also this post on another forum
for a more high-level, more complete block diagram. ]
[ Edit: Inductors 13 and 15 seem to be combined into a single inductor L1 in place of 15. Switch S10 does not exist, and S12 is a paralleled pair of either MOSFETs or IGBTs (Q31/Q32) in the negative side of the power supply, not the positive side as shown. Inductors L1 and L2 of the diagram are combined into a single inductor L4 on the actual hardware. ]
[ Edit: The large (470 μF 500 V) electrolytic capacitors (C40, C41) are on the high voltage side of the DC/DC converter, in parallel with two 0.47 μF film capacitors (C32, C34) near the associated IGBTs. The 230 V inverter IGBTs have two film capacitors, 0.68 μF and 0.47 μF, across their DC bus, which is separated from the actual DC bus by the buck transistor(s). The large film capacitor C33 (20 uF) is part of the 230 VAC line LC filter, along with L4. ]
[ Edit: Added second diagram for comparison. Removed the "suspect buck converter is back to front"comment. ]
MG ZS EV 2021 April 2021.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
Patching PIP-4048/5048 inverter-chargers.