Smart and on/off-grid power inverters

Abstract

A method and apparatus is disclosed that can intelligently invert DC power from single or multiple DC sources to single-phase, split-phase, or three-phase AC power, supply the AC power to the electric power grid when the grid is on, or supply AC power to electric devices or loads when the grid is down. A Smart and Grid-Flexible Power Inverter, or On/Off-Grid Power Inverter, is disclosed that can work in either the on-grid or off-grid mode, and switch back and forth between the two modes manually or automatically depending on the power grid conditions. The system provides a simple and cost-effective solution for areas where the power grid has frequent outages or long downtimes.

1 . A scalable DC to AC power inversion system for providing AC power to the electric grid or to an off-grid AC circuit respectively from a plurality of individual DC power sources each having a DC output port, comprising:
 a) at lease one on-grid power inverter, each having at least one DC input port, an on-grid AC input port, and an on-grid AC output port;   b) at least one on/off-grid power inverter, each having at least one DC input port, an on-grid AC output port, and an off-grid AC output port;   c) the on-grid AC output port of each inverter being connected in a daisy chain to the on-grid AC input port of the next inverter, except for the on-grid AC output port of the first inverter being connected to the grid;   d) said on-grid AC output port of the first inverter being arranged to supply AC power produced by all inverters to the grid when the grid is on;   e) the off-grid AC output port of each on/off-grid power inverter being connected to an off-grid AC circuit and arranged to supply AC power to AC loads in the off-grid circuit when grid is down; and   f) whereby said system is incrementally scalable by adding or subtracting DC power sources and daisy-chained inverters.   
     
     
         2 . The system of  claim 1 , further comprising:
 a) a first DC power source connected to one of said DC power input ports of one of said power inverters; and   b) a second DC power source, different in kind from said first DC power source, connected to another of said DC power input ports of said one power inverter.   
     
     
         3 . The system of  claim 1 , wherein the output of each said on-grid power inverter and the on-grid output of each said on/off-grid power inverter is single-phase AC or three-phase AC. 
     
     
         4 . A method of making a grid-flexible power generation system incrementally scalable, comprising:
 a) connecting a DC power source to each DC input port of a plurality of on/off-grid power inverters, each of the inverters also having an on-grid AC output port and an off-grid AC output port;   b) combining said on-grid AC output port of all said inverters together so the total produced AC power is the summation of the AC power supplied by each inverter; and   c) providing AC power to the electric grid through the combined on-grid AC output ports when the grid is on or providing AC power to one or multiple AC loads, individually, through said off-grid AC output port of each inverter when the grid is down.   
     
     
         5 . The method of  claim 4 , further comprising:
 a) each of said inverters having an on-grid AC input port;   b) combining said on-grid AC output port of all inverters together by daisy-chaining the inverters, said on-grid AC output port of each inverter being connected in a daisy chain to the on-grid AC input port of the next inverter, except for the on-grid AC output port of the first inverter being connected to the electric grid, and the on-grid AC input port of the last inverter being left open; and   c) providing AC power to the electric grid through the on-grid AC output port of the first inverter when the grid is on.   
     
     
         6 . The method of  claim 4 , further comprising:
 a) connecting a first DC power source to one of said DC power input ports of one of said power inverters; and   b) connecting a second DC power source, different in kind from said first DC power source, to another of said DC power input ports of said one power inverter.   
     
     
         7 . The method of  claim 4 , in which the on-grid output of each said power inverter is single-phase 220V-240V 50 Hz/60 Hz AC and the off-grid output of each said power inverter is single-phase 100V-120V 50 Hz/60 Hz AC. 
     
     
         8 . The method of  claim 4 , in which the on-grid output of each said power inverter is single-phase 220V-240V 50 Hz/60 Hz AC and the off-grid output of each said power inverter is single-phase 220V-240V 50 Hz/60 Hz AC. 
     
     
         9 . The method of  claim 4 , in which the on-grid output of each said power inverter is three-phase AC and the off-grid output of each said power inverter is single-phase AC. 
     
     
         10 . The method of  claim 4 , in which the on-grid output of each said power inverter is three-phase AC and the off-grid output of each said power inverter is three-phase AC.