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Electric power storage system using capacitors and control method thereof including serial-parallel switching means for each circuit block of batteries based on descending order of block voltages

  • US 7,898,223 B2
  • Filed: 10/19/2005
  • Issued: 03/01/2011
  • Est. Priority Date: 10/19/2005
  • Status: Expired due to Fees
First Claim
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1. An electric power storage system using capacitors, the system comprising:

  • power storage means having a circuit configuration in which n circuit blocks are connected in series, where n is a natural number equal to or larger than two, each of the n circuit blocks including a plurality of capacitors;

    DC-AC conversion means that converts a DC output voltage from the power storage means into an AC output voltage and supplies the AC voltage to a load;

    serial-parallel switching means that switches, between parallel and series, a connection of the plurality of capacitors in each circuit block of the power storage means;

    a plurality of overcharge prevention means, each of which connected in parallel to each of the plurality of capacitors in the power storage means, and has the corresponding capacitor forcibly discharge when a terminal voltage of the capacitor reaches a withstand voltage value;

    inter-terminal voltage detection means which detects an inter-terminal voltage between the plurality of capacitors of each circuit block of the power storage means;

    block voltage determination means that determines a block voltage, for each circuit block, based on the inter-terminal voltage of each capacitor detected by the inter-terminal voltage detection means, the block voltage being a voltage of the circuit block; and

    control means that detects the output voltage of the power storage means and controls the serial-parallel switching means according to a value of the detected voltage, whereinwhen the power storage means is being charged, the control means performs;

    a first process of controlling the serial-parallel switching means so that the plurality of capacitors of each circuit block of the power storage means are connected in series at the beginning of charging the power storage means;

    a second process of controlling the serial-parallel switching means, when the output voltage of the power storage means reaches a maximum input voltage of the DC-AC conversion means, so that the connection of the plurality of capacitors of each of j circuit blocks in the descending order of block voltages determined by the block voltage determination means are switched to the parallel connection, where j is a natural number up to n indicating the number of times that an input voltage reaches the maximum input voltage during one charging process; and

    a third process of controlling the serial-parallel switching means, where j<

    n, after the connection of the plurality of capacitors of each of j circuit blocks are switched to the parallel connection in the second process until the output voltage of the power storage means reaches the maximum input voltage of the DC-AC conversion means again, so that the connection of the plurality of capacitors of each of j circuit blocks selected anew in the descending order of the block voltages determined anew by the block voltage determination means are switched to the parallel connection, and that the plurality of capacitors of j circuit blocks rather than the j circuit blocks selected anew among the j circuit blocks before selected anew, andwhen the power storage means is being discharged, the control means performs;

    a fourth process of controlling the serial-parallel switching means so that the plurality of capacitors of each circuit block of the power storage means are connected in parallel at the beginning of discharging the power storage means;

    a fifth process of controlling the serial-parallel switching means, when the output voltage of the power storage means reaches a minimum input voltage of the DC-AC conversion means, so that the connection of the plurality of capacitors of each of k circuit blocks in the descending order of block voltages determined by the block voltage determination means are switched to the serial connection, where k is a natural number up to n indicating the number of times that an input voltage reaches the minimum input voltage during one discharging process; and

    a sixth process of controlling the serial-parallel switching means, where k<

    n, after the connection of the plurality of capacitors of each of k circuit blocks are switched to the serial connection in the fifth process until the output voltage of the power storage means reaches the minimum input voltage of the DC-AC conversion means again, so that the connection of the plurality of capacitors of each of k circuit blocks in the descending order of the block voltages determined anew by the block voltage determination means are switched to the serial connection, and that the plurality of capacitors of k circuit blocks rather than the k circuit blocks selected anew among the j circuit blocks before selected anew;

    wherein j is incremented during the second process but remains constant during the third process, and wherein k is incremented during the fifth process but remains constant during the sixth process.

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