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Smart and scalable off-grid mini-inverters

  • US 8,994,218 B2
  • Filed: 06/11/2012
  • Issued: 03/31/2015
  • Est. Priority Date: 06/10/2011
  • Status: Active Grant
First Claim
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1. A system for providing AC power to an AC load from a plurality of individual DC power sources each having a DC power output port, comprising:

  • a) a plurality of power inverters, each of said power inverters having one DC power input port, an AC power input port, and an AC power output port;

    b) said AC power output port of each inverter being connected in a daisy chain to the AC power input port of the next inverter, except for the AC power input port of the first inverter being left open, and the AC power output port of the last inverter being connected to the AC load;

    c) each of the power inverters including;

    i) a DC-DC boost converter arranged to convert the voltage of a DC power source to a higher DC voltage suitable for inversion;

    ii) a DC-AC inverter connected to said DC-DC boost converter and arranged to invert the DC power to AC power;

    iii) an internal AC powerline that allows the generated AC power to be sent to the AC load through an external AC powerline;

    iv) a load interface circuit connected to said DC-AC inverter and to said internal AC powerline, said load interface circuit being arranged to filter high-frequency components out of the said DC-AC inverter'"'"'s AC output;

    v) a digital microcontroller connected to said DC-DC boost converter, DC-AC inverter, and load interface circuit, said microcontroller arranged to monitor the DC boost voltage, control the DC-DC boost converter, perform maximum power point tracking (MDPT), perform DC-AC inversion, monitor AC current and voltage for generated power amount and status, perform powerline communications, and perform logic controls such as AC powerline switching and isolation; and

    vi) a powerline modem connected to said microcontroller and said internal AC powerline through an interface circuitry arranged to establish a 2-way digital signal communication between the digital microcontroller and the outside world through the external AC powerline;

    d) one of the power inverters further including;

    i) a load detector connected to said internal AC powerline and external AC powerline, and arranged to detect the impedance of the connected AC load;

    ii) said digital microcontroller further connected to the load detector and arranged to check the impedance of the AC load to determine if it is within predetermined specifications, initially energize the internal and external AC powerline, continually deliver AC power to the internal and external AC powerline to allow the other power inverters also connected on the same external AC powerline to synchronize the AC power being produced, continually check and determine whether the AC load is too large or too small for the power generation system to handle, and turn the power off and trigger an error signal if the load is too large or too small; and

    iii) a line sensing circuit connected to said internal AC powerline and said microcontroller, and arranged to detect if there is AC power on the internal AC powerline prior to the startup of the inverter, and to monitor the internal AC powerline for over voltage, under voltage, over current, or under current conditions;

    e) each of the other power inverters further including;

    i) said digital microcontroller arranged to perform AC power synchronization;

    ii) a line sensing circuit connected to said internal AC powerline and said microcontroller for detecting the phase and zero-crossing point of the incoming AC power from the external AC powerline; and

    iii) a solid state switch connected to said internal AC powerline and external AC powerline, and arranged to disconnect said internal AC powerline from the external AC powerline during the non-generation time.

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