Apparatus and method for charging and discharging photovoltaic PCS integrated battery

• US 8,493,020 B2
• Filed: 10/07/2010
• Issued: 07/23/2013
• Est. Priority Date: 05/06/2010
• Status: Expired due to Fees

• Current Assignee: Samsung Electro-Mechanics Co., Ltd. (Samsung Group), Sungkyunkwan University Foundation For Corporate Collaboration (SungKyunKwan University (SKKU))
• Original Assignee: Samsung Electro-Mechanics Co., Ltd. (Samsung Group), Sungkyunkwan University Foundation For Corporate Collaboration (SungKyunKwan University (SKKU))
• Inventors: Lee, Tae Won, Oh, Dong Seong, Kim, Jin Wook, Moon, Hee Sung, Kim, Jong Soo, Won, Chung Yuen, Lee, Byoung Kuk, Choe, Gyu Yeong, Ko, Jeong Min
• Primary Examiner(s): Berhanu, Samuel
• Application Number:
  US12/899,938
• Publication Number:
  US 20110273130A1
• Time in Patent Office: 1,020 Days
• Field of Search: 320/101
• US Class Current: 320/101
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/465 with solar battery as charging system
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/44 with means for ensuring correct phase sequence
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: H02J 9/06 with automatic change-over , e.g. UPS systems
• CPC Class Codes: H02S 40/32 comprising DC/AC inverter means associated with the PV module itself, e.g. AC modules
• CPC Class Codes: Y02B 10/70 Hybrid systems, e.g. uninterruptible or back-up power supplies integrating renewable energies
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

There are provided an apparatus and method for charging and discharging a photovoltaic PCS integrated battery applied to a system that includes a first DC/DC converter 110 connected to a solar cell 10, a DC/AC inverter 120, a DC link unit 130 connected in common to output terminals of the first DC/DC converter 110 and the DC/AC inverter 120, and a second DC/DC converter 140 having a bidirectional DC/DC conversion function connected between the DC rink unit 130 and the battery 30. The present invention calculates the amount of photovoltaic power produced by the solar cell 10 based on voltage and current detected in the voltage/current detector 200, determines one of predetermined control modes according to the amount of photovoltaic power and the connection or not of the battery, and controls the first DC/DC converter 110, the second DC/DC converter, and the DC/AC inverter according to the determined control mode.

Claims

1. An apparatus for charging and discharging a photovoltaic (PV) power conditioning system (PCS) integrated battery, the apparatus comprising:

a first direct-current-to-direct-current (DC/DC) converter converting a PV voltage from a solar cell into a predetermined DC voltage according to a first DC/DC control;

a direct-current-to-alternate-current (DC/AC) inverter connected to a system and performing a system voltage to DC voltage conversion or DC voltage to system voltage conversion according to a second DC/DC control;

a DC link unit connected in common to an output terminal of the first DC/DC converter and an output terminal of the DC/AC inverter to stablize a DC voltage from the first DC/DC converter and a DC voltage from the DC/AC inverter;

a second DC/DC converter connected between the DC link unit a battery to convert voltage bidirectionally according to the second DC/DC control;

a voltage and current detector detecting PV voltage and current from the solar cell, battery voltage and current from the battery, system voltage and current from the system, and DC link voltage and current from the DC link unit; and

a charging control unit determining one of a plurality of predetermined control modes based on the voltage and current detected in the voltage and current detector and controls the first DC/DC converter, the second DC/DC converter, and the DC/AC inverter according to the determined control mode.

2. The apparatus of claim 1, wherein the charging control unit calculates an amount of photovoltaic power produced by the solar cell based on the voltage and current detected in the voltage and current detector and determines one of first to fourth control modes according to the amount of photovoltaic power and whether or not the battery is connected.

3. The apparatus of claim 2, wherein the charging control unit includes:

a state determining unit determining any of the predetermined first to fourth operating modes based on the amount of photovoltaic power and whether or not the battery is connected, by using the PV voltage and current and the battery voltage and current detected in the voltage and current detector;

a first converter controller controlling the first DC/DC converter according to the operating mode determined in the state determining unit;

an inverter controller controlling the DC/AC inverter according to the operating mode determined in the state determining unit; and

a second converter controller controlling the second DC/DC converter according to the operating mode determined in the state determining unit.

4. The apparatus of claim 3, wherein the charging control unit controls the first DC/DC converter, the DC/AC inverter, and the second DC/DC converter to charge the battery by using the photovoltaic energy from the solar cell in the first operating mode.

5. The apparatus of claim 4, wherein the charging control unit controls the first DC/DC converter, the DC/AC inverter, and the second DC/DC converter to charge the battery by using the photovoltaic energy from the solar cell and the system voltage in the second operating mode.

6. The apparatus of claim 5, wherein the charging control unit controls the first DC/DC converter, the DC/AC inverter, and the second DC/DC converter to charge the battery by using the system voltage in the third operating mode.

7. The apparatus of claim 6, wherein the charging control unit controls the first DC/DC converter, the DC/AC inverter, and the second DC/DC converter to transfer the photovoltaic energy from the solar cell to the system in the fourth operating mode.

8. The apparatus of claim 7, wherein the first converter controller includes:

a maximum power point tracking (MPPT) unit tracking a predetermined maximum power point by using the PV output voltage and the PV current to generate a PV output voltage command value;

a first voltage control unit compensating for a predetermined PV output voltage control value by using error voltage between the PV output voltage command value from the MPPT unit and the PV detecting voltage Vpv; and

a first converter pulse-width-modulation (PWM) generator generating a first converter PWM signal based on the PV output voltage control value compensated in the first voltage control unit.

9. The apparatus of claim 7, wherein the inverter controller includes:

a system phase detector detecting the phase of the system voltage and generates the phase signal having the detected phase;

a DC link voltage control unit compensating for a predetermined DC link voltage control value by using error voltage between the DC link voltage and the predetermined DC link voltage command value;

a signal converter generating the AC command value by multiplying the DC link voltage control value compensated in the DC link voltage control unit by the phase signal of the system phase detector;

a first current control unit compensating for the predetermined AC control value by using the error current between the AC command value from the signal converter and the detected AC;

a current feed-forward compensator generating the phase signal based on a value generated by dividing the PV power determined by the PV voltage and current by the system voltage;

a current compensator compensating for the AC control value from the first current control unit in synchronization with the phase signal from the current feed-forward compensator; and

an inverter pulse-width-modulation (PWM) generator generating the inverter PWM signal based on the AC control value compensated in the current compensator.

10. The apparatus of claim 7, wherein the second converter controller includes:

a voltage control unit compensating for a predetermined battery current command value by using the error voltage between the battery voltage and the predetermined battery voltage command value;

a current control unit compensating for a predetermined battery current control value by using the error current between the battery current command value compensated in the voltage control unit and the detected battery current; and

a second converter pulse-width-modulation (PWM) generator generating a second converter PWM signal by using the battery current control value compensated in the current control unit.

11. A method of charging and discharging a photovoltaic (PV) power conditioning system (PCS) integrated battery applied to a system that includes a first direct-current-to-direct-current (DC/DC) converter connected to a solar cell, a direct-current-to-alternate-current (DC/AC) inverter connected to a system, a DC link unit connected in common to an output terminal of the first DC/DC converter and an output terminal of the DC/AC inverter, and a second DC/DC converter having a bidirectional DC/DC conversion function connected between the DC link unit and the battery, the method comprising:

a detecting step of detecting PV voltage and current detected in a predetermined node, battery voltage and current, system voltage and current, and DC link voltage;

a state determining step of determining any of predetermined first to fourth operating modes based on an amount of photovoltaic power and whether or not the battery is connected, by using the PV voltage and current and the battery voltage and current;

a first control step of controlling the charging of the battery by using the photovoltaic energy of the solar cell in the first operating mode;

a second control step of controlling the first DC/DC converter, the DC/AC inverter, and the second DC/DC converter to charge the battery by using the photovoltaic energy of the solar cell and the voltage of the system in the second operating mode; and

a third control step of controlling the first DC/DC converter, the DC/AC inverter, and the second DC/DC converter to charge the battery by using the voltage of the system in a third operating mode.

12. The method of claim 11, further comprising a fourth control step of controlling the first DC/DC converter, the DC/AC inverter, and the second DC/DC converter in order to transfer the photovoltaic energy of the solar cell to the system in the fourth operating mode.

13. The method of claim 12, wherein the state determining step includes

determining a first control mode when the power from the solar cell is higher than the charge amount needed in the battery in a state in which the battery is connected, based on the amount of photovoltaic power and whether or not the battery is connected, by using the PV voltage and current and the battery voltage and current,

determining a second control mode when the power from the solar cell is not higher than the charge amount needed in the battery in the state in which the battery is connected,

determining a third control mode when there is no power from the solar cell in the state in which the battery is connected, and

determining a fourth operating mode in the state in which the battery is not connected.

14. The method of claim 13, wherein the first control step includes using the DC/DC converter and the DC/AC inverter to control maximum power point tracking (MPPT), DC link voltage and system link and control the current charging through the second DC/DC converter.

15. The method of claim 14, wherein the second control step includes using the DC/DC converter and the DC/AC inverter to control MPPT, the DC link voltage, and a pulse-width-modulation (PWM) generator and control the current charging through the second DC/DC converter.

16. The method of claim 15, wherein the third control step includes stopping the operation of the DC/DC converter and controlling the current charging and the current discharging by using the DC/AC inverter and the second DC/DC converter.

17. The method of claim 16, wherein the fourth control step includes using the DC/DC converter and the DC/AC inverter to control MPPT, the DC link voltage and the system link and control the operation stop of the second DC/DC converter.

18. The method of claim 17, wherein the controlling the first DC/DC converter of the first to fourth control steps includes:

an MPPT step of performing the predetermined MPPT by using the PV output voltage and the PV current to generate the PV output voltage command value;

a first voltage control step of compensating for the predetermined PV output voltage command value by using the error voltage between the PV output voltage command value from the MPPT step and the PV detecting voltage; and

a first converter PWM generating step of generating a first converter PWM signal based on the PV output voltage control value compensated in the first voltage control step.

19. The method of claim 17, wherein the controlling the DC/AC inverter of the first to fourth control steps includes:

a system phase detecting step of detecting the phase of the system voltage and generates the phase signal having the detected phase;

a DC link voltage control step of compensating for a predetermined DC link voltage control value by using error voltage between the DC link voltage and the predetermined DC link voltage command value;

a signal converting step of generating the AC command value by multiplying the DC link voltage control value compensated in the DC link voltage control step by the phase signal of the system phase detector;

a first current control step of compensating for the predetermined AC control value by using the error current between the AC command value from the signal converting step and the detected AC;

a current feed-forward compensating step of generating the phase signal based on a value generated by dividing the PV power determined by the PV voltage and current by the system voltage;

a current compensating step of compensating for the AC control value from the first current control step in synchronization with the phase signal from the current feed-forward compensating step, and

an inverter PWM generating step of generating an inverter PWM signal based on the AC control value compensated in the current compensating step.

20. The method of claim 17, wherein the controlling the second DC/DC converter of the first to fourth control steps includes:

a voltage control step of compensating for a predetermined battery current command value by using the error voltage between the battery voltage and the predetermined battery voltage command value;

a current control step of compensating for a predetermined battery current control value by using the error current between the battery current command value compensated in the voltage control step and the detected battery current; and

a second converter PWM generating step of generating a second converter PWM signal by using the battery current control value compensated in the current control step.