Electric power system

• US 6,380,715 B1
• Filed: 02/26/2001
• Issued: 04/30/2002
• Est. Priority Date: 12/27/2000
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kubo, Kenji
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/791,727
• Time in Patent Office: 428 Days
• Field of Search: 320/104, 320/125, 320/127, 320/128, 320/135, 320/137, 320/162, 320/163, 320/164
• US Class Current: 320/128
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus circuits for charging H02J7/00
• CPC Class Codes: H02J 3/32 using batteries with converting means
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

An electric power system including a power source, a load, a battery discharging power to the load and accumulating power from the power source, a power detector detecting power supplied from the power source, a power converter converting power charged to and discharged from the battery, and a power controller controlling power converted by the power controller. When power supplied to the load from the power source exceeds an upper limit, the power converter is controlled by a current command calculated from deviation between the supplied power and the upper limit to discharge power to the load from the battery. When the power is below a charge threshold of the battery, the power converter is controlled by a charge command to supply a power to the battery from the power source.

Claims

1. An electric power system comprising:

a power source;

a load supplied with power from said power source;

a battery for discharging the power to said load, and for accumulating the power from said power source;

a power detector for detecting the supply power of said power source;

a power converter for power converting the power charged to and discharged from said battery; and

a power controller for controlling the power which is power converted by said power converter,

wherein, when a detection value of the power supplied to said load from said power source exceeds a predetermined power upper limit value, the power discharged to said load from said battery is controlled on the basis of a deviation between the detection value of said power and said power upper limit value.

2. An electric power system according to claim 1,

wherein, when the detection value of the power supplied to said load from said power source is equal to or lower than a predetermined threshold value, the charge power is supplied to said battery from said power source.

3. An electric power system according to claim 1,

wherein, said power converter includes two smoothing capacitors with one of said two smoothing capacitors being connected to said battery, and said power converter further includes a power converting circuit for detecting a voltage of each of said two smoothing capacitors, and for balancing a voltage unbalance of said two smoothing capacitors caused by the charge and discharge of said battery.

4. An electric power system according to claim 2,

wherein, said power converter includes two smoothing capacitors with one of said two smoothing capacitors being connected to said battery, and said power converter further includes a power converting circuit for detecting a voltage of each of said two smoothing capacitors, and for balancing a voltage unbalance of said two smoothing capacitors caused by the charge and discharge of said battery.

5. An electric power system according to claim 1,

wherein, a power failure detector of said power source is provided, and when a power failure occurs in said power source, the power is supplied to said load from said battery.

6. An electric power system according to claim 2,

wherein, a power failure detector of said power source is provided, and when a power failure occurs in said power source, the power is supplied to said load from said battery.

13. An electric power system according to claim 1,

wherein, said power upper limit value is set by obtaining a mean value in each short time of the power of said power source and a mean value in each long time, and by adjusting so that a difference between both the mean values becomes small.

7. An electric power system comprising:

a power source;

a load supplied with power from said power source;

a battery for discharging the power to said load, and for accumulating the power from said power source;

a power detector for detecting the supply power of said power source;

a direct current power converter for controlling the charge and discharge of said battery;

a further power converter for controlling the output voltage of said direct current power converter at constant independently of the charge and discharge of said battery; and

a power controller for controlling the power which is charged to and discharged from said battery,

wherein, when a detection value of the power supplied to said load from said power source exceeds a predetermined power upper limit value, the power discharged to said load from said battery is controlled on the basis of a deviation between the detection value of said power and said power upper limit value.

8. An electric power system according to claim 7,

wherein, when the detection value of the power supplied to said load from said power source is equal to or lower than a predetermined threshold value, the power is charged to said battery from said further power converter through said direct current power converter.

9. An electric power system according to claim 7,

wherein, a specific load is connected through a change-over device in parallel with said load connected to said power source, and an alternating current output unit is connected between said specific load and said direct current power converter, and a power failure detector of said power source is provided, and wherein, when a power failure occurs in said power source, said change-over device is changed over to said alternating current output unit, and the direct current power of said battery is converted into an alternating current voltage through said alternating current output unit, and is supplied to said specific load.

10. An electric power system according to claim 8,

wherein, a specific load is connected through a change-over device in parallel with said load connected to said power source, and an alternating current output unit is connected between said specific load and said direct current power converter, and a power failure detector of said power source is provided, and wherein, when a power failure occurs in said power source, said change-over device is changed over to said alternating current output unit, and the direct current power of said battery is converted into an alternating current voltage through said alternating current output unit, and is supplied to said specific load.

11. An electric power system according to claim 7,

further comprising:

a specific load;

an alternating current output unit connected between said specific load and a connection point between said direct current power converter and said further power converter; and

a power failure detector of said power source, and

wherein, when said power source is normal, the output voltage of said further power converter is converted into an alternating current voltage, and on the other hand, when the power failure occurs in said power source, the direct current power of said battery is converted into the alternating current voltage, and the power is supplied to said specific load.

12. An electric power system according to claim 8,

further comprising:

a specific load;

an alternating current output unit connected between said specific load and a connection point between said direct current power converter and said further power converter; and

a power failure detector of said power source, and

wherein, when said power source is normal, the output voltage of said further power converter is converted into an alternating current voltage, and on the other hand, when the power failure occurs in said power source, the direct current power of said battery is converted into the alternating current voltage, and the power is supplied to said specific load.

14. An electric power system according to claim 7,

wherein, said power upper limit value is set by obtaining a mean value in each short time of the power of said power source and a mean value in each long time, and by adjusting so that a difference between both the mean values becomes small.