====== Droop mode precautions ======
<WRAP center round warning 60%>
Warning

Droop control mode is still an experimental functionality, the performance depends.
</WRAP>



===== Scope =====
  * Since firmware D141, droop mode has been added to PWS2-30K/M, to provide a non-communication off-grid parallel operation solution.
  * Single phase firmware can supports three sets of inverters droop mode yet.
===== To enable droop mode =====
  * To write register 750(0x02EE) and 756(0x02F4), authorization must be granted first, by writing 2007 to register 4007(0x0FA7) and 2016 to register 4008(0x0FA8).
  * The PWS2-30K must be set to 3P3W, 750(0x02EE)= 1; and** NO neutral line connected**
  * To enable droop mode, set register 756(0x02F4) to 1
  * After enabling droop mode, <del>a hard reboot is required.</del>, write 1 to register 657(0x0291) to reboot the software. make sure the inverter is not running at this moment.

===== Requirements =====
  * A delta-wye transformer is required if 277V or 220V single phase load is required.
  * When multiple PWS2-30K/M are used for off-grid droop parallel operation, there must be one PWS2-30K establishing AC voltage first, and then the others can be started.
  * The maximum quantity of PWS2-30K/M verified to be working for off-grid droop parallel operation in one microgrid is 9 units (because we can only obtain 9 units in the lab)
  * When droop parallel operation implemented, the length of the cables from the PWS2-30K/M should be as same as possible.

===== Side effects =====
  * The droop mode will bring voltage and frequency fluctuation (90%~110%)
  * The droop mode will bring some circulating current between each PWS2-30K/M, if the load is low in off-grid microgrid, the currents of each DC side of the PWS2-30K will be fluctuating not more than of ±5%