Photovoltaic system with selective MPP mismatch

• US 9,270,141 B2
• Filed: 04/19/2011
• Issued: 02/23/2016
• Est. Priority Date: 05/04/2010
• Status: Active Grant

• Current Assignee: Adensis Gmbh
• Original Assignee: Adensis Gmbh
• Inventors: Beck, Bernhard
• Primary Examiner(s): SHECHTMAN, SEAN P
• Application Number:
  US13/089,916
• Publication Number:
  US 20110276188A1
• Time in Patent Office: 1,771 Days
• Field of Search: 700/297
• US Class Current: 1/1
• CPC Class Codes: H02J 2300/10 The dispersed energy generation being of fossil origin, e.g. diesel generators
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources maximum power point systems in particular G05F1/67
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: H02J 9/00 Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
• CPC Class Codes: H02J 9/06 with automatic change-over , e.g. UPS systems
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A method for operating a photovoltaic system provides, with the turning off of the otherwise adjusted regulation to the maximum power point MPP, to make a selective mismatching at the inverter, in order to cause a battery current, which is added to the system current. As a result, an additional energy source to maintain a minimum feed power is achieved during a rapidly changing cloud pattern.

Claims

1. A method for operating a photovoltaic system having an inverter at whose input terminals a DC output voltage of a photovoltaic generator is applied and whose output is connected to a supply network, and having a battery bank connected by a switch in parallel to the input terminals, the method comprising:

adjusting a maximum power point of the photovoltaic generator via a regulating element of the inverter; and

operating selectively the photovoltaic generator by setting a voltage value at the input terminals of the inverter, the voltage value and its associated current value are mismatched with respect to the maximum power point of the photovoltaic generator in order to provoke a discharge current from the battery bank to the input terminals of the inverter if a predefinable minimum power of the photovoltaic generator is not achieved,

wherein the output of the inverter is continuously connected to the supply network such that an uninterrupted supply of alternating current is provided from the photovoltaic system to the supply network at or above the predefinable minimum power,

wherein a voltage measuring sensor is provided in parallel to the battery bank to measure the battery voltage in case of the switch being either open or closed, and

wherein the battery, the photovoltaic generator and a DC side of the inverter are simultaneously at a same operating voltage in both a charging state and discharging state.

2. The method according to claim 1, wherein the nominal voltage of the battery bank corresponds to the operating voltage of the photovoltaic generator.

3. The method according to claim 1, wherein the mismatching is started:

by first adjusting the voltage point on the typical U/I characteristic of the inverter that corresponds substantially to the actual voltage across the battery bank,

by then closing a disconnect switch arranged in the current path of the connecting line of the battery bank to the inverter, and

by setting the operating point of the regulating element of the inverter to a voltage value smaller than the actual voltage of the battery bank.

4. The method according to claim 1, wherein the current generated by the photovoltaic system is measured by a first current measuring sensor and the mismatching is ended when the current measured by the first current measuring sensor exceeds a limit which is predefined depending on the minimum power.

5. The method according to claim 4, wherein after the mismatching ends, the disconnect switch remains closed for recharging the battery bank until a predefinable charge state of the battery bank is determined.

11. The method according to claim 1, wherein the uninterrupted supply of alternating current is provided from the photovoltaic system by the photovoltaic generator, the battery bank, and/or a generator.

12. The method according to claim 1, wherein the uninterrupted supply of alternating current is provided in a first operating state by the photovoltaic generator and is provided in a second operating state by both the photovoltaic generator and the battery bank.

6. A method for operating a photovoltaic system having an inverter at whose input terminals a DC output voltage of a photovoltaic generator is applied and whose output is connectable to a supply network, and having a battery bank connected switch in parallel to the input terminals, the method comprising:

adjusting a maximum power point of the photovoltaic generator via a regulating element of the inverter and

operating selectively the photovoltaic generator by setting a voltage value at the input terminals of the inverter, the voltage value and its associated current value are mismatched with respect to the maximum power point of the photovoltaic generator in order to provoke a discharge current from the battery bank to the input terminals of the inverter if a predefinable minimum power of the photovoltaic generator is not achieved,

wherein the output of the inverter is continuously connected to the supply network such that an uninterrupted supply of alternating current is provided from the photovoltaic system to the supply network at or above the predefinable minimum power,

wherein a voltage measuring sensor is provided in parallel to the battery bank to measure the battery voltage in case of the switch being either open or closed, and

wherein a second current measuring sensor is provided in a line between the battery bank and the inverter, and wherein, with a shortfall in a predefined charge state of the battery bank, the connection of a replacement power plant to the supply network is initiated.

7. A device for operating a photovoltaic generator, the device comprising:

an inverter, at whose input terminals a DC output voltage of the photovoltaic generator is applied and whose output is connectable to a supply network;

a battery bank connectable by a switch in parallel to the input terminals;

a regulating element of the inverter configured to adjust a maximum power point of the photovoltaic generator;

a disconnect switch through which the battery bank is connected to the inverter; and

a control/regulating device that sets the operating point of the photovoltaic generator by the regulating element of the inverter to a predefinable voltage value and that closes the disconnect switch during a shortfall of a predefined minimum power of the photovoltaic system,

wherein the output of the inverter is continuously connected to the supply network such that an uninterrupted supply of alternating current is provided from the photovoltaic system to the supply network,

wherein the predefinable voltage value and its associated current value are mismatched with respect to the maximum power point of the photovoltaic generator,

wherein a voltage measuring sensor is provided in parallel to the battery bank to measure the battery voltage in case of the switch being either open or closed, and

wherein the battery, the photovoltaic generator and a DC side of the inverter are simultaneously at a same operating voltage in both a charging, state and discharging state.

8. The device according to claim 7, wherein a first current measuring sensor is arranged in a current path of the battery bank to the inverter.

9. The device according to claim 7, wherein a second current measuring sensor or a diode is arranged in a current path between the inverter and the photovoltaic generator.

10. The device according to claim 7, wherein the control/regulating device in conjunction with the regulating element of the inverter adjusts the DC voltage at the input terminals such that a predefined current flows out of or to the battery bank.

13. The device according to claim 7, wherein the uninterrupted supply of alternating current is provided from the photovoltaic system by the photovoltaic generator, the battery bank, and/or a generator.

14. The device according to claim 7, wherein the uninterrupted supply of alternating current is provided in a first operating state by the photovoltaic generator and is provided in a second operating state by both the photovoltaic generator and the battery bank.

15. The device according to claim 7, wherein the voltage established by the control/regulating device is lower than a voltage at the maximum power point.

16. The device according to claim 7, wherein the operating point of the photovoltaic generator is set to a voltage smaller than a voltage of the battery bank.