Solar cell power system with a solar array bus lockup cancelling mechanism

• US 5,025,202 A
• Filed: 09/07/1990
• Issued: 06/18/1991
• Est. Priority Date: 09/08/1989
• Status: Expired due to Term

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Ishii, Akihiko, Matsui, Toshio, Honda, Yukihiro
• Primary Examiner(s): Wong, Peter S.
• Application Number:
  US07/579,073
• Time in Patent Office: 284 Days
• Field of Search: 323/299, 323/906, 320/2, 320/13, 320/14, 320/32, 320/39, 307/44, 307/46
• US Class Current: 320/101
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y10S 136/293 Circuits
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

A solar cell power system includes a device which determines the occurrence of solar array bus lockup by detecting the voltage of the power bus, the discharge current of the storage battery, and the solar array current (or the load current) and performing a calculation using these items of data in addition to the regulated bus voltage to emit a lockup signal, by which the magnitude of the load is reduced, thereby cancelling the lockup state. Alternatively, a solar cell system may include a lockup cancelling drive device, which accumulates in a coil cancelling-drive, energy supplied from the storage battery and then discharges this energy to the power bus, thereby cancelling the lockup stage without reducing the magnitude of the load.

Claims

1. A solar cell power system with a solar array bus lockup cancelling mechanism, comprising:

a common return line;

a solar cell means having an output terminal and a terminal connected to said return line;

a shunt device connected in parallel between the output terminal of said solar cell means and said return line;

a power bus;

a first unilateral current transmission means which has an input terminal connected to the output terminal of said solar cell means and an output terminal connected to said power bus and which allows a current to flow only from the output terminal of said solar cell means toward said power bus;

a storage battery means having an output terminal and a terminal connected to said return line;

a charging means connected to said power bus and the output terminal of said storage battery means in series with said storage battery means;

a second unilateral current transmission means which has an input terminal connected to the output terminal of said storage battery means and an output terminal connected to said power bus and which allows a current to flow only from the output terminal of said storage battery means toward said power bus;

a charge storage means connected between said power bus and said return line;

a load which has a first terminal connected to said power bus, a second terminal connected to said return line, and a control terminal, said load reducing its own magnitude when a load power reducing signal is supplied to said control terminal;

a charge/discharge current monitor means which has an output terminal and which is connected to said storage battery means to monitor the charge/discharge current that charges said storage battery means or that is discharged therefrom, emitting through said output terminal a signal representing the charge/discharge current thus monitored;

a bus voltage monitor means which has an output terminal and which is inserted between said power bus and said return line to monitor the bus voltage in said power bus, emitting through said output terminal a signal representing the bus voltage thus monitored;

a solar array current monitor means which has an output terminal and which is connected to said first unilateral current transmission means to monitor the solar array current flowing from said first unilateral current transmission means to said power bus, emitting through said output terminal a signal representing the solar array current thus monitored, or a load current monitor means which has an output terminal and which is connected to said load to monitor the load current, emitting through said output terminal a signal representing the load current thus monitored; and

a solar array bus lockup determining means which has three input terminals and an output terminal, two of said three input terminals being respectively connected to the output terminal of said charge/discharge current monitor means and the output terminal of said bus voltage monitor means, the remaining one input terminal being connected to either said solar array current monitor means or said load current monitor means, said output terminal being connected to said control terminal of said load, said solar array bus lockup determining means including a reference voltage generating means for generating a reference voltage representing the regulated bus voltage when the solar cell power system is not in the solar array bus lockup state with the bus voltage being regulated by said shunt device, said solar array bus lockup determining further calculating the effective generated power of said solar cell means and the load power consumed by said load on the basis of the regulated bus voltage, the monitored bus voltage, the monitored discharge current, and either of the monitored solar array current or the monitored load current to generate a load power reducing signal at said output terminal when said effective generated power is greater than said load power;

whereby the state is detected in which, during a period of sunlight, the bus voltage is fixed to the output voltage of said storage battery means and in which discharge from said storage battery means continues even though said solar cell means can manage to supply all the necessary load current so that the magnitude of said load is temporarily reduced to restore the state in which the bus voltage is regulated by said shunt device.

2. A solar cell power system with a solar array bus lockup cancelling mechanism according to claim 1, wherein said solar array bus lockup determining means includes:

a first subtracting means which has two input terminals and an output terminal, said two input terminals being respectively connected to the output terminal of said load current monitor means and the output terminal of said charge/discharge current monitor means, said first subtracting means calculating the differential current between the load current and the discharge current from said storage battery means to emit through said output terminal a signal representing said differential current;

a first multiplying means which has two input terminals and an output terminal, said two input terminals being respectively connected to the output terminal of said subtracting means and said reference voltage generating means, said first multiplying means emitting through said output terminal a signal representing the product of said regulated bus voltage and said differential current;

a second multiplying means which has two input terminals and an output terminal, said two input terminals being respectively connected to the output terminal of said bus voltage monitor means and the output terminal of said load current monitor means, said second multiplying means emitting through said output terminal a signal representing the product of the bus voltage and the load current; and

a first comparing means which has two input terminals and an output terminal, said two input terminals being respectively connected to the output terminals of said first and second multiplying means, said output terminal being connected to the control terminal of said load, said first comparing means comparing the product of said regulated bus voltage and said differential current with the product of said bus voltage and the load current to generate a load power reducing signal when the product of said regulated bus voltage and said differential current is greater than the product of said bus voltage and the load current.

3. A solar cell power system with a solar array bus lockup cancelling mechanism according to claim 1, wherein said solar array bus lockup determining means includes:

a second subtracting means which has two input terminals and an output terminal, said two input terminals being respectively connected to the output terminal of said load current monitor means and the output terminal of said charge/discharge current monitor means, said second subtracting means calculating the differential current between the load current and the discharge current from said storage battery means to emit through said output terminal a signal representing said differential current;

a third subtracting means which has two input terminals and an output terminal, said two input terminals being respectively connected to said reference voltage generating means and the output terminal of said bus voltage monitor means, said third subtracting means calculating the differential voltage between said regulated bus voltage and the monitored bus voltage to emit through said output terminal a signal representing said differential voltage;

a third multiplying means which has two input terminals and an output terminal, said two input terminals being respectively connected to the output terminals of said second and third subtracting means, said third multiplying means emitting through said output terminal a signal representing the product of said differential voltage and said differential current;

a fourth multiplying means which has two input terminals and an output terminal, said two input terminals being respectively connected to the output terminal of said bus voltage monitor means and the output terminal of said charge/discharge current monitor means, said fourth multiplying means emitting through said output terminal a signal representing the product of the bus voltage and the discharge current from said storage battery means; and

a second comparing means which has two input terminals and an output terminal, said two input terminals being respectively connected to the output terminals of said third and fourth multiplying means, said output terminal being connected to the control terminal of said load, said second comparing means comparing the product of said differential voltage and said differential current with the product of said bus voltage and said discharge current to generate a load power reducing signal when the product of said differential voltage and said differential current is greater than the product of said bus voltage and said discharge current.

4. A solar cell power system with a solar array bus lockup cancelling mechanism according to claim 1, wherein said solar array bus lockup determining means includes:

a fifth multiplying means which has two input terminals and an output terminal, said input terminals being respectively connected to said reference voltage generating means and the output terminal of said solar array current monitor means, said fifth multiplying means calculating the product of said regulated bus voltage and said solar array current to emit through said output terminal a signal representing said product;

an adding means which has two input terminals and an output terminal, said two input terminals being respectively connected to the output terminal of said solar array current monitor means and the output terminal of said charge/discharge current monitor means, said adding means calculating the sum current of the solar array current and the charge/discharge current to emit through said output terminal a signal representing said sum current;

a sixth multiplying means which has two input terminals and an output terminal, said two input terminals being respectively connected to the output terminal of said bus voltage monitor means and the output terminal of said adding means, said sixth multiplying means emitting through said output terminal a signal representing the product of the bus voltage and said sum current; and

a third comparing means which has two input terminals and an output terminal, said two input terminals being respectively connected to the output terminals of said fifth and sixth multiplying means, said output terminal being connected to the control terminal of said load, said third comparing means comparing the product of said regulated bus voltage and said solar array current with the product of said bus voltage and said sum current to generate a load power reducing signal when the product of said regulated bus voltage and said solar array current is greater than the product of said bus voltage and said sum current.

5. A solar cell power system with a solar array bus lockup cancelling mechanism according to claim 1, wherein said solar array bus lockup determining means includes:

a fourth subtracting means which has two input terminals and an output terminal, said two input terminals being respectively connected to said reference voltage generating means and the output terminal of said bus voltage monitor means, said fourth subtracting means calculating the differential voltage between said regulated bus voltage and the monitored bus voltage to emit through said output terminal a signal representing said differential voltage;

a seventh multiplying means which has two input terminals and an output terminal, said two input terminals being respectively connected to the output terminal of said fourth subtracting means and the output terminal of said solar array current monitor means, said seventh multiplying means emitting through said output terminal a signal representing the product of said differential voltage and the solar array current;

an eighth multiplying means which has two input terminals and an output terminal, said two input terminals being respectively connected to the output terminal of said bus voltage monitor means and the output terminal of said charge/discharge current monitor means, said eighth multiplying means emitting through said output terminal a signal representing the product of the bus voltage and the discharge current; and

a fourth comparing means which has two input terminals and an output terminal, said two input terminals being respectively connected to the output terminals of said seventh and eighth multiplying means, said output terminal being connected to the control terminal of said load, said fourth comparing means comparing the product of said differential voltage and the solar array current with the product of said bus voltage and the discharge current to generate a load current reducing signal when the product of said differential voltage and said solar array current is greater than the product of said bus voltage and said discharge current.

6. A solar cell power system with a solar array bus lockup cancelling mechanism according to claim 1, wherein said first and second unilateral current transmission means consist of diodes and wherein said charge storage means consists of a capacitor.

7. A solar cell power system with a solar array bus lockup cancelling mechanism, comprising:

a common return line;

a solar cell means having an output terminal and a terminal connected to said return line;

a shunt device connected in parallel between the output terminal of said solar cell means and said return line;

a power bus;

a first unilateral current transmission means which has an input terminal connected to the output terminal of said solar cell means and an output terminal connected to said power bus and which allows a current to flow only from the output terminal of said solar cell means toward said power bus;

a storage battery means which has an output terminal and a terminal which is connected to said return line;

a charging means which is connected to said power bus and the output terminal of said storage battery means in series with said storage battery means;

a second unilateral current transmission means which has an input terminal connected to the output terminal of said storage battery means and an output terminal connected to said power bus and which allows a current to flow only from the output terminal of said power storage means toward said power bus;

a charge storage means connected between said power bus and said return line;

a load which has a first terminal connected to said power bus, and a second terminal connected to said return line;

a charge/discharge current monitor means which has an output terminal and which is connected to said storage battery means to monitor the charge/discharge current that charges said storage battery means or that is discharged therefrom, emitting through said output terminal a signal representing the charge/discharge current thus monitored;

a bus voltage monitor means which has an output terminal and which is inserted between said power bus and said return line to monitor the bus voltage in said power bus, emitting through said output terminal a signal representing the bus voltage thus monitored;

a solar array current monitor means which has an output terminal and which is connected to said first unilateral current transmission means to monitor the solar array current flowing from said first unilateral current transmission means to said power bus, emitting through said output terminal a signal representing the solar array current thus monitored, or a load current monitor means which has an output terminal and which is connected to said load to monitor the load current, emitting through said output terminal a signal representing the load current thus monitored;

a solar array bus lockup determining means which has three input terminals and an output terminal, two of said three input terminals being respectively connected to the output terminal of said charge/discharge current monitor means and the output terminal of said bus voltage monitor means, the remaining one input terminal being connected to either the output terminal of said solar array current monitor means or the output terminal of said load current monitor means, said solar array bus lockup determining means including a reference voltage generating means for generating a reference voltage representing the regulated bus voltage when the system is not in the solar array bus lockup state with the bus voltage being regulated by said shunt device, and calculating the effective generated power of said solar cell means and the load power consumed by said load on the basis of said regulated bus voltage, the monitored bus voltage, the monitored discharge current, and either of the monitored solar array current or the monitored load current to generate a solar array bus lockup signal at said output terminal when said effective generated power is greater than said load power; and

a solar array bus lockup cancelling drive means which has an input terminal connected to the output terminal of said storage battery means, an output terminal connected to said power bus, and a control terminal connected to the output terminal of said solar array bus lockup determining means, said solar array bus lockup cancelling drive means responding to said solar array bus lockup signal to accumulate for a predetermined time solar array bus lockup cancelling drive energy supplied from said storage battery means and to discharge said solar array bus lockup cancelling drive energy to said power bus after said predetermined time has elapsed;

whereby the solar cell power system is released from the state in which, during a period of sunlight, the bus voltage is fixed to the output voltage of said storage battery means andfin which discharge from said storage battery means continues even though said solar cell means can manage to supply all the necessary load current, and is restored, without temporarily reducing the magnitude of said load, to the state in which the bus voltage is regulated by said shunt device.

8. A solar cell power system with a solar array bus lockup cancelling mechanism according to claim 7, wherein said solar array bus lockup cancelling drive means includes:

a diode which has a cathode and an anode, said cathode being connected to said power bus;

a coil connected between the anode of said diode and the output terminal of said storage battery means;

a transistor connected between the anode of said diode and said return line; and

a drive which is connected between said transistor and the output terminal of said solar array bus lockup determining means, said drive responding to said solar array bus lockup signal to drive said transistor for a predetermined time.

9. A solar cell power system with a solar array bus lockup cancelling mechanism according to claim 7, wherein said first and second unilateral current transmission means consist of diodes and wherein said charge storage means consists of a capacitor. PG,36

10. A solar cell power system having a solar cell which provides power to a power bus, a shunt device that stablizes the power bus voltage, a storage battery which provides power to said power bus during eclipse time and which is charged by a charging means during sunlight, said system comprising:

a charge/discharge current monitor means which emits a signal representing the charge/discharge current that charges said storage battery means or that is discharged therefrom;

a bus voltage monitor means which emits a signal representing the bus voltage in said power bus;

a solar array current monitor means which emits a signal representing the solar array current flowing from said solar cell to said power bus; and

a solar array bus lock-up determining means which generates a signal if solar array bus lock-up occurs, on the basis of signals from said bus voltage monitor means, said solar array current monitor means and said charge/discharge current monitor means.

11. A solar cell power system as set forth in claim 10 wherein said solar array bus lock-up determining means includes:

a reference voltage generating means which generates a reference voltage equal to the regulated bus voltage when the solar cell power system is not in the solar array bus lock-up state;

a first multiplying means which calculates a first product of said reference voltage and said solar array current and emits a signal representing said first product;

an adding means which calculates the sum current of said solar array current and said charge/discharge current and emits a signal representing said sum current;

a second multiplying means which calculates a second product of said bus voltage and said sum current and emits a signal representing said second product; and

the comparing means which compares said first product with said second product and generates a signal to indicate whether solar array bus lock-up has occurred.

12. A solar cell power system as set forth in claim 10 wherein said solar array bus lock-up determining means includes:

a reference voltage generating means which generates a reference voltage equal to the regulated bus voltage when the solar cell power system is not in the solar array bus lock-up state;

a subtracting means which calculates the differential voltage between said reference voltage and said bus voltage and emits a signal representing said differential voltage;

a first multiplying means which calculates a first product of said differential voltage and said solar array current and emits a signal representing said first product;

a second multiplying means which calculates a second product of said bus voltage and said charge/discharge current and emits a signal representing said second product; and

a comparing means which compares said first product with said second product and generates a signal to indicate whether solar array bus lock-up has occurred.

13. A solar cell power system as set forth in claim 10 further comprising:

a load means connected to said power bus.

14. A solar cell power system as set forth in claim 13 wherein said load means provides control means whereby said load can be reduced.

15. A solar cell power system as set forth in claim 14 wherein said load is reduced by said control means on the basis of said signal generated by said solar bus lock-up determining means.

16. A solar cell power system as set forth in claim 10 which includes a solar array bus lock-up cancelling drive means which is connected to said power bus which responds to said signal generated by said solar array bus lock-up determining means and accumulates energy supplied from said storage battery for a pre-determined time and discharges said energy to said power bus after said pre-determined time has elapsed.

17. A solar cell power system as set forth in claim 16 wherein said solar array bus lock-up cancelling drive means includes:

a diode which has a cathode and anode said cathode being connected to said power bus;

a coil connected between the anode of said diode and the output terminal of said storage battery;

a transistor connected to said diode; and

a drive means which is connected between said transistor and said solar array bus lock-up determining means.

25. A solar cell power system as set forth in any one of claims 11, 12, 19 and 20 further comprising a load means connected to said power bus.

26. A solar cell power system as set forth in claim 25 wherein said load means includes control means whereby said load means can be reduced on the basis of the signal generated by said solar bus lock-up determining means.

18. A solar cell power system having a solar cell which provides power to a power bus while a shunt device that stablizes the power bus voltage, and a storage battery which provides power to said power bus during eclipse time and which is charged by a charging means during sunlight, said system further comprising:

a charge/discharge current monitor means which emits a signal representing the charge/discharge current that charges said storage battery or that is discharged therefrom;

a bus voltage monitor means which emits a signal representing the bus voltage in said power bus;

a means for connecting a load means to said power bus;

a load current monitor means which emits a signal representing the load current flowing from said power bus to said load; and

a solar array bus lock-up determining means which generates a signal if solar array bus lock-up occurs, on the basis of signals from said charge/discharge current monitor means, said bus voltage monitor means and said load current monitor means.

19. A solar cell power system as set forth in claim 18, wherein said solar array bus lock-up determining means includes:

a reference voltage generating means which generates a reference voltage equal to the regulated bus voltage when the solar cell power system is not in the solar array bus lock-up state;

a subtracting means which calculates the differential current between said load current and said charge/discharge current and emits a signal representing said differential current;

a first multiplying means which calculates a first product of said reference voltage and said differential current and emits a signal which represents said first product;

a second multiplying means which calculates a second product of said bus voltage and said load current and emits a signal representing said second product;

a comparing means which compares said first product with said second product and generates a signal to indicate whether solar array bus lock-up has occurred.

20. A solar cell power system as set forth in claim 18 wherein said solar array bus lock-up determining means includes:

reference voltage generating means which generates a reference voltage equal to the regulated bus voltage when the solar cell power system is not in the solar array bus lock-up state;

a first subtracting means which calculates the differential current between said load current and said charge/discharge current and emits a signal representing the said differential current;

a second subtracting means which calculates the differential voltage between said reference voltage and said monitored bus voltage and emits a signal representing said differential voltage;

a first multiplying means which calculates a first product of said differential voltage and said differential current and emits a signal representing said first product;

a second multiplying means which calculates a second product of said bus voltage and said charge/discharge current and emits a signal representing said second product; and

a comparing means which compares said first product with said second product and generates a signal to indicate whether solar array bus lock-up has occured.

21. A solar cell power system as set forth in claim 18, wherein said load means provides control means whereby said load can be reduced.

22. A solar cell power system as set forth in claim 21 wherein said load is reduced by said control means on the basis of said signal generated by said solar array bus lock-up determining means.

23. A solar cell power system as set forth in claim 18 which includes a solar array bus lock-up cancelling drive means which is connected to said power bus which responds to said signal generated by said solar array bus lock-up determining means and accumulates energy supplies from said storage battery for a pre-determined time and discharges said energy to said power bus after said pre-determined time has elapsed.

24. A solar cell power system as set forth in claim 23 which wherein said solar array bus lock-up cancelling drive means includes:

a diode which has a cathode and anode said cathode being connected to said power bus;

a coil connected between the anode of said diode and the output terminal of said storage battery;

a transistor connected to said diode; and

a drive means which is connected between said transistor and said solar array bus lock-up determining means.