I am working through a paper that discusses the design of a multi-level inverter to connect photovoltaic arrays to the grid. It uses 4 PV modules (only two are shown in the design image below, but it is expandable) along with an H-bridge to produce 31 voltage levels. These are used to produce a modified sine wave with low THD:
The scheme for switching Q1 - Q4 uses a reference voltage: V_ref(t) = V_max*sin(wt + delta_ref)
The authors given equations for calculating the switch signals, which include "mod 2":
I am aware of the usual meaning of "m mod n" as "the remainder left over when m is divided by n". This doesn't seem to work here at all!
Can anybody tell me how the given equations are able to generate the switching signals?: