The voltage at the top most node of this circuit should be the average of the input voltages.
Vtop*CT = C1*V1 +C2*V2 +C3*V3 where CT = C1+C2+C3
I get 0V instead.
CT = (20uF+10uF+10uF) = 40uF
4Vtot = 15V*2 +3V + 4V
Vtot=9.25V as seen in the graph
Here's what i was trying to simulate: http://sci-hub.tw/https://www.sciencedirect.com/science/article/pii/S1434841116308524