APPARATUS AND METHOD FOR VOLTAGE AND CURRENT BALANCING IN GENERATION OF OUTPUT POWER IN POWER GENERATION SYSTEMS

• US 20150035371A1
• Filed: 07/29/2014
• Published: 02/05/2015
• Est. Priority Date: 07/31/2013
• Status: Active Grant

• Current Assignee: Qatar Foundation For Education, Science And Community Development, Spiretronic, LLC
• Original Assignee: Shehab Ahmed
• Inventors: AHMED, SHEHAB, MASSOUD, AHMED, MORSY, AHMED SALAH
• Granted Patent: US 9,236,743 B2
• Time in Patent Office: Days
• US Class Current: 307/78
• CPC Class Codes: H02J 2300/20 The dispersed energy generation being of renewable origin
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/466 Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand

Abstract

An apparatus for voltage balancing parallel arranged direct current (DC) voltage source strings in a power generation system includes a string voltage balancing circuit having reverse blocking switches to control a current flow and an output voltage of the DC voltage source strings. Capacitors are connected to a corresponding reverse blocking switch and in series with a corresponding one of the plurality of DC voltage source strings to construct a voltage difference for a corresponding one of the plurality DC voltage source strings. The string voltage balancing circuit adjusts an output voltage of the DC voltage source strings by controlling a current flowing in the plurality of DC voltage source strings to adjust a voltage constructed across corresponding ones of the capacitors to balance the output voltage for the DC voltage source strings to be substantially the same output voltage. Current balancing using differential power processing is also provided.

Claims

1. An apparatus for voltage balancing a plurality of parallel arranged direct current (DC) voltage source strings in a power generation system, comprising:

at least one string voltage balancing circuit, each string voltage balancing circuit comprising;

at least two reverse blocking switches each adapted to control a current flowing in and an output voltage of one or more corresponding DC voltage source strings; and

at least two capacitors each communicatively connected to a corresponding at least one reverse blocking switch and communicatively connected in series with a corresponding one of the plurality of DC voltage source strings, each capacitor being adapted to construct a voltage difference for a corresponding one of the plurality DC voltage source strings,

wherein the at least one string voltage balancing circuit selectively adjusts an output voltage of each of the DC voltage source strings by selectively controlling a current flowing in corresponding ones of the plurality of DC voltage source strings to selectively adjust a voltage constructed across corresponding ones of the at least two capacitors to balance the output voltage for each of the DC voltage source strings to be substantially the same output voltage.

2. The apparatus for voltage balancing a plurality of parallel arranged DC voltage source strings according to claim 1, wherein the at least one string voltage balancing circuit further comprises:

at least one inductor communicatively connected to least two reverse blocking switches adapted to minimize a ripple current flowing to the two reverse blocking switches, the current flowing in the inductor being divided by the at least two reverse blocking switches to flow the divided current into corresponding ones of the plurality of DC voltage source strings.

3. The apparatus for voltage balancing a plurality of parallel arranged DC voltage source strings according to claim 2, wherein the at least two reverse blocking switches comprise a switch selected from the group consisting of a transistor, a metal-oxide semiconductor field effect transistor (MOSFET) and an insulated-gate bipolar transistor (IGBT).

4. The apparatus for voltage balancing a plurality of parallel arranged DC voltage source strings according to claim 1, wherein the at least two reverse blocking switches comprise a switch selected from the group consisting of a transistor, a metal-oxide semiconductor field effect transistor (MOSFET) and an insulated-gate bipolar transistor (IGBT).

5. The apparatus for voltage balancing a plurality of parallel arranged DC voltage source strings according to claim 1, wherein duty ratios of the at least two reverse blocking switches are controlled to construct the voltage difference for corresponding ones of the plurality DC voltage source strings to balance the output voltage for each of the DC voltage source strings to be substantially the same output voltage.

6. The apparatus for voltage balancing a plurality of parallel arranged DC voltage source strings according to claim 5, wherein a sum of the duty ratios of the at two reverse blocking switches is substantially equal to one (1).

7. The apparatus for voltage balancing a plurality of parallel arranged DC voltage source strings according to claim 1, wherein the at least one string voltage balancing circuit further comprises:

at least two diodes respectively arranged in series with corresponding ones of the at least two reverse blocking switches adapted to control a direction of current flow.

8. The apparatus for voltage balancing a plurality of parallel arranged DC voltage source strings according to claim 1, wherein

the at least one string voltage balancing circuit comprises a closed loop voltage balancing configuration, and

the closed loop configuration comprises:

at least six reverse blocking switches adapted to control a current flowing in and an output voltage of at least three corresponding DC voltage source strings, and

at least three capacitors each communicatively connected to at least a corresponding pair of reverse blocking switches and to a corresponding one of the DC voltage source strings.

9. The apparatus for voltage balancing a plurality of parallel arranged DC voltage source strings according to claim 1, wherein

the at least one string voltage balancing circuit comprises a complimentary string voltage balancing configuration, and

the complimentary string voltage balancing configuration comprises:

at least a pair of said string voltage balancing circuits, each pair of said string voltage balancing circuits being arranged in opposing relation at opposite ends of a corresponding group of three DC voltage source strings adapted to control a current flowing in and an output voltage of the group of the three corresponding DC voltage source strings,

wherein a capacitor from each of said pair of said string voltage balancing circuits is communicatively connected to a same corresponding one of the DC voltage source strings of the group of three DC voltage source strings, the capacitors connected to the same corresponding DC voltage source string being adapted to construct a voltage difference for the said same DC voltage source string.

10. The apparatus for voltage balancing a plurality of parallel arranged DC voltage source strings according to claim 1, wherein

the at least one string voltage balancing circuit comprises a single star string voltage balancing configuration, and

the single star string voltage balancing configuration comprises:

at least three reverse blocking switches each associated with a respective one of a corresponding plurality of DC voltage source strings adapted to control a current flowing in and an output voltage of the respective one of the DC voltage source strings, and

at least three capacitors each communicatively connected to a respective one of the DC voltage source strings to which the corresponding respective reverse blocking switch is communicatively connected.

11. The apparatus for voltage balancing a plurality of parallel arranged DC voltage source strings according to claim 10, wherein the single star voltage balancing configuration further comprises:

an inductor communicatively connected to each of the plurality of reverse blocking switches adapted to minimize a ripple current flowing to the reverse blocking switches, the current flowing in the inductor being divided by the reverse blocking switches to flow the divided current into corresponding ones of the plurality of DC voltage source strings.

12. The apparatus for voltage balancing a plurality of parallel arranged DC voltage source strings according to claim 1, wherein

the at least one string voltage balancing circuit comprises a double star string voltage balancing configuration, and

the double star string voltage balancing configuration comprises:

a first group and a second group each of at least three reverse blocking switches, a reverse blocking switch from each of the first and the second group being respectively associated with a respective one of a corresponding plurality of DC voltage source strings adapted to control a current flowing in and an output voltage of the respective one of the DC voltage source strings, and

at least three capacitors each communicatively connected to a respective one of the DC voltage source strings to which the corresponding respective reverse blocking switch from the first group and the respective reverse blocking switch from the second group is communicatively connected.

13. The apparatus for voltage balancing a plurality of parallel arranged DC voltage source strings according to claim 12, wherein the double star voltage balancing configuration further comprises:

a pair of inductors, one of said pair of inductors being communicatively connected to the first group of reverse blocking switches and the other of the pair of inductors being communicatively connected to the second group of reverse blocking switches, the pair of inductors adapted to minimize a ripple current flowing to the reverse blocking switches, the current flowing in the inductor communicatively connected to the first group of reverse blocking switches being divided by the reverse blocking switches of the first group to flow the divided current into corresponding ones of the plurality of DC voltage source strings, and the current flowing in the inductor communicatively connected to the second group of reverse blocking switches being divided by the reverse blocking switches of the second group to flow the divided current into corresponding ones of the plurality of DC voltage source strings.

14. The apparatus for voltage balancing a plurality of parallel arranged DC voltage source strings according to claim 1, further comprising:

a controller including a processor to control operation of the at least one voltage balancing circuit to selectively adjust the output voltage of each of the DC voltage source strings by selectively controlling a current flowing in corresponding ones of the plurality of DC voltage source strings to selectively adjust a voltage constructed across corresponding ones of the at least two capacitors to balance the output voltage for each of the DC voltage source strings to be substantially the same output voltage.

15. A method for voltage balancing a plurality of parallel arranged direct current (DC) voltage source strings in a power generation system, comprising the steps of:

controlling by a controller including a processor an operation of at least one string voltage balancing circuit to selectively adjust an output voltage of each of a plurality of DC voltage source strings by selectively controlling a current flowing in corresponding ones of the plurality of DC voltage source strings;

selectively controlling by the controller a current flowing in each of the plurality of DC voltage source strings by controlling operation of at least two reverse blocking switches associated with a corresponding at least one voltage balancing circuit, each reverse blocking switch associated with a corresponding one of the plurality of DC voltage source strings; and

selectively adjusting by the controller a voltage difference for at least two capacitors associated with a corresponding at least one voltage balancing circuit to selectively adjust a voltage constructed across corresponding ones of the at least two capacitors to balance the output voltage for each of the DC voltage source strings to be substantially the same output voltage.

16. The method for voltage balancing a plurality of parallel arranged direct current (DC) voltage source strings in a power generation system according to claim 15, further comprising the step of:

controlling by the controller including a processor an operation of differential power processing (DPP) to adjust respective currents flowing through each of a plurality of series connected DC voltage source modules respectively forming corresponding ones of the plurality of DC voltage source strings by a plurality of reverse blocking switches communicatively connected to the corresponding ones of the series connected DC voltage source modules to balance the current between corresponding ones of the series connected DC voltage source modules.

17. The method for voltage balancing a plurality of parallel arranged direct current (DC) voltage source strings in a power generation system according to claim 16, wherein

the controller controls the operation of differential power processing (DPP) to adjust the respective currents flowing through each of the plurality of series connected DC voltage source modules such that each DC voltage source module can substantially carry a current at a maximum power (I_mpp) different from another DC voltage source module in the corresponding ones of the plurality of DC voltage source strings, and

a voltage generated by each DC voltage source module based on the adjusted current corresponds to a voltage at a maximum power (V_mpp).

18. An apparatus for current balancing a plurality of parallel arranged direct current (DC) voltage source strings in a power generation system, comprising:

at least one differential power processing (DPP) current balancing circuit, each DPP current balancing circuit comprising;

a plurality of reverse blocking switches communicatively connected to a plurality of series connected DC voltage source modules respectively forming corresponding ones of the plurality of DC voltage source strings to control currents respectively flowing through each of the communicatively connected series connected DC voltage source modules; and

a plurality of inductors communicatively connected to the series connected DC voltage source modules and to the plurality of reverse blocking switches to induce a corresponding voltage based on the flow of the respective controlled currents to balance a current between corresponding ones of the series connected DC voltage source modules to adjust the respective currents flowing through each of the plurality of series connected DC voltage source modules.

19. The apparatus for current balancing a plurality of parallel arranged direct current (DC) voltage source strings in a power generation system according to claim 18, further comprising:

a controller including a processor to control operation of the plurality of reverse blocking switches for the differential power processing (DPP) operation to control adjusting the respective controlled currents flowing through each of the plurality of inductors to the series connected DC voltage source modules respectively forming corresponding ones of the plurality of DC voltage source strings to balance the current between the corresponding series connected DC voltage source modules.

20. The apparatus for current balancing a plurality of parallel arranged direct current (DC) voltage source strings in a power generation system according to claim 19, wherein

the controller controls the operation of differential power processing (DPP) to adjust the respective currents flowing through each of the plurality of series connected DC voltage source modules such that each DC voltage source module can substantially carry a current at a maximum power (L_mpp) different from another DC voltage source module in the corresponding ones of the plurality of DC voltage source strings, and

a voltage generated by each DC voltage source module based on the adjusted current corresponds to a voltage at a maximum power (V_mpp).