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KR-20260062319-A - BI-DIRECTIONAL ENERGY SAVING FDC SYSTEM WITH RELAYS FOR DOWNSIZING FUEL CELL SYSTEM AND SWITCHING METHOD BETWEEN BUCK MODE AND BOOST MODE USING THE SAME

KR20260062319AKR 20260062319 AKR20260062319 AKR 20260062319AKR-20260062319-A

Abstract

The present invention relates to a bidirectional isolated FDC system applying a contact-type relay for miniaturization of a fuel cell system, and a method for switching operating modes between buck mode and boost mode using the same. The system comprises an input stage (①) which is an input terminal where power generated from a fuel cell is supplied to the FDC; an input decoupling capacitor (②) which is a capacitor placed at the input terminal of the FDC; an inductor coil (③) which is a coil contributing to voltage reduction in buck mode and voltage increase in boost mode; a low-side switching FET (④) which acts as a rectifier diode in buck mode and as a switch in boost mode; a high-side switching FET (⑤) which acts as a switch in buck mode and as a rectifier diode in boost mode; a DC link capacitor (⑥); a full-bridge LLC FET series (⑦); an LLC transformer (⑧); a full-bridge LLC diode series (⑨); a changeover relay boost positive (⑩); and a changeover relay It is characterized by being configured to include a boost negative (⑪), a changeover relay buck positive (⑫), a changeover relay buck negative (⑬), an output decoupling capacitor (⑭), and an output stage (⑮) which is an output terminal where power is boosted through the FDC and supplied to the battery.

Inventors

  • 조강희

Assignees

  • 영화테크(주)

Dates

Publication Date
20260507
Application Date
20241029

Claims (8)

  1. In a bidirectional isolated FDC (Fuel Cell DC-DC Converter) system that applies a contact-type relay for the miniaturization of a fuel cell system that does not require starting power supplied from a high-voltage battery once the starting of a fuel cell system that receives starting power from a high-voltage battery in advance for self-generation starting is completed, As a connection part between the fuel cell stack and the FDC, an input stage (①) which is an input terminal where power generated from the fuel cell is supplied to the FDC; An input decoupling capacitor (②), which is a capacitor placed at the input terminal of the FDC to remove harmonic components of the power supplied from the above fuel cell stack; An inductor coil (③) that utilizes electrical characteristics to contribute to voltage reduction in buck mode and voltage increase in boost mode; A low-side switching FET (④) that acts as a rectifier diode in buck mode and a switch in boost mode, as a switching element that controls the duty ratio through ON/OFF operation; A high-side switching FET (⑤) which acts as a switching element that controls the duty ratio through ON/OFF operation, acting as a switch in Buck Mode and a rectifier diode in Boost Mode; A DC link capacitor (⑥) which is a capacitor that charges with the voltage supplied from the battery in buck mode and the voltage boosted by the coil in boost mode, cancels out the potential difference occurring between the front and rear ends and maintains a uniform link voltage; A full-bridge LLC FET series (⑦), which is a switching FET series located at the front end of the isolation circuit configured as a full-bridge circuit; LLC transformer (⑧), which is a transformer that electrically separates the front and rear ends of the circuit to protect the circuit from electrical damage; A full-bridge LLC diode series (⑨), which is a series of rectifier diodes located at the rear end of the isolation circuit composed of a full-bridge circuit; A changeover relay boost positive (⑩), which is a C-contact relay located on the positive (+) line of the insulation section that changes the circuit structure to buck mode or boost mode depending on the driving conditions; A changeover relay boost negative (⑪), which is a C-contact relay located on the insulating front negative (-) line that changes the circuit structure to buck mode and boost mode depending on the driving conditions; A changeover relay buck positive (⑫), which is a C-contact relay located on the positive (+) line at the rear end of the insulation section that changes the circuit structure to buck mode or boost mode depending on the driving conditions; A changeover relay buck negative (⑬), which is a C-contact relay located on the negative (-) line at the rear end of the insulation section that changes the circuit structure to buck mode or boost mode depending on the driving conditions; An output decoupling capacitor (⑭) which is a capacitor placed at the output terminal of the FDC to remove harmonic components, which are AC components that are not perfectly rectified from the full-bridge LLC diode series (⑨); and A bidirectional isolated FDC system using a contact-type relay, characterized by being configured to include an output stage (⑮) which is an output terminal where power generated through hydrogen power generation is boosted through the FDC and supplied to the battery as a connection between the FDC and the high-voltage battery.
  2. In Article 1, When buck mode (t 1 to t 2 ) is turned OFF, changeover relays ⑩, ⑪), ⑫, and ⑬ An output stage (⑮) which is the output terminal in a normally closed state; an output decoupling capacitor (⑭), which is a capacitor placed at the output terminal of the FDC to remove AC components; a full-bridge LLC FET series (⑦), which is a switching FET series located at the front end of the isolation circuit composed of a full-bridge circuit; an LLC transformer (⑧), which is a transformer that protects the circuit from electrical damage by electrically isolating the front and rear ends of the circuit; a full-bridge LLC diode series (⑨), which is a rectifier diode series located at the rear end of the isolation circuit composed of a full-bridge circuit; a DC link capacitor (⑥), which is a capacitor that charges with the voltage supplied from the battery in buck mode and the voltage boosted by the coil in boost mode, cancels out the potential difference occurring between the front and rear ends, and maintains a uniform link voltage; and a high-side switching element that controls the duty ratio through ON/OFF operation, acting as a switch in buck mode and a rectifier diode in boost mode. A bidirectional isolated FDC system with a contact-type relay applied, characterized by receiving power by changing to a buck mode, comprising: an FET (⑤); a low-side switching FET (④) which acts as a rectifier diode in buck mode and a switch in boost mode as a switching element that controls the duty ratio through ON/OFF operation; an inductor coil (③) which is a coil that contributes to voltage reduction in buck mode and voltage increase in boost mode by utilizing electrical characteristics; an input decoupling capacitor (②) which is a capacitor placed at the input terminal of the FDC to remove harmonic components of the power supplied from the fuel cell stack; and an input stage (①) which is an input terminal where power generated from the fuel cell is supplied to the FDC as a connection part between the fuel cell stack and the FDC. (Here, t1 is the buck mode start time and t2 is the buck mode end time).
  3. In Article 1, When starting the fuel cell stack, changeover relays ⑫ and ⑬ are turned ON and changeover relays ⑩ and ⑪ are turned OFF; in cases where there are no insulation requirements or where non-insulation is permissible for a short period (t 1 ~ t 2 ), An output stage (⑮) which is an output terminal; an output decoupling capacitor (⑭) which is a capacitor placed at the output terminal of the FDC to remove AC components; a DC link capacitor (⑥) which is a capacitor that charges with voltage supplied from the battery in buck mode and voltage boosted by the coil in boost mode, cancels out the potential difference occurring between the front and rear terminals, and maintains a uniform link voltage; a high-side switching FET (⑤) which acts as a switch in buck mode and a rectifier diode in boost mode as a switching element that controls the duty ratio through ON/OFF operation; a low-side switching FET (④) which acts as a rectifier diode in buck mode and a switch in boost mode as a switching element that controls the duty ratio through ON/OFF operation; an inductor coil (③) which is a coil that contributes to voltage reduction in buck mode and voltage increase in boost mode by utilizing electrical characteristics; and a capacitor placed at the input terminal of the FDC to remove harmonic components of the power supplied from the fuel cell stack. A bidirectional isolation type FDC system using a contact-type relay, characterized by operating and maintaining isolation by switching to a buck mode, which is composed of an input decoupling capacitor (②) which is a capacitor and an input stage (①) which is a connection part between the fuel cell stack and the FDC and is an input terminal where power generated from the fuel cell is supplied to the FDC. (Here, t1 is the buck mode start time and t2 is the buck mode end time).
  4. In Article 1, In buck mode with changeover relays 10 and 11 turned ON and changeover relays 12 and 13 turned OFF, from t 3 , As a connection part between the fuel cell stack and the FDC, there is an input stage (①) which is an input terminal where power generated from the fuel cell is supplied to the FDC; an input decoupling capacitor (②) which is a capacitor placed at the input terminal of the FDC to remove harmonic components of the power supplied from the fuel cell stack; an inductor coil (③) which is a coil that contributes to voltage reduction in buck mode and voltage increase in boost mode by utilizing electrical characteristics; a low-side switching FET (④) which acts as a rectifier diode in buck mode and a switch in boost mode as a switching element that controls the duty ratio through ON/OFF operation; a high-side switching FET (⑤) which acts as a switch in buck mode and a rectifier diode in boost mode as a switching element that controls the duty ratio through ON/OFF operation; and a capacitor in which the voltage supplied from the battery in buck mode and the voltage increased by the coil in boost mode are charged, canceling out the potential difference occurring between the front and rear terminals and maintaining a uniform link voltage. A bidirectional isolation type FDC system with a contact-type relay applied, characterized by maintaining operation and isolation by changing to a boost mode composed of a DC link capacitor (⑥), a full-bridge LLC FET series (⑦) which is a switching FET series located at the front end of the isolation circuit composed of a full-bridge circuit, an LLC transformer (⑧) which is a transformer that electrically separates the front and rear ends of the circuit to protect the circuit from electrical damage, a full-bridge LLC diode series (⑨) which is a rectifier diode series located at the rear end of the isolation circuit composed of a full-bridge circuit, an output decoupling capacitor (⑭) which is a capacitor placed at the output end of the FDC to remove AC components that are not perfectly rectified from the full-bridge LLC diode series (⑨), and an output stage (⑮) which is an output end that serves as a connection between the FDC and the high-voltage battery, where power generated through hydrogen power generation is boosted through the FDC and supplied to the battery. (Here, t3 is the boost mode start time).
  5. In Article 4, When the operation of the above fuel cell stack is terminated, A bidirectional isolated FDC system using contact-type relays, characterized in that the controller turns off changeover relays 10 and 11 after terminating boost mode control.
  6. A method for switching from Buck Mode to Boost Mode using a bidirectional isolated FDC system with a contact-type relay for miniaturization of a fuel cell system that does not require starting power supplied from a high-voltage battery when the starting of a fuel cell system that receives starting power from a high-voltage battery in advance for self-generation starting is completed, A step (S11) of inputting and storing a command value in a controller that controls a bidirectional isolated FDC system using a contact-type relay; A step (S12) in which the controller controls the supply of power from the battery to a bidirectional isolated FDC system using a contact-type relay, and switches the bidirectional isolated FDC system using the contact-type relay to buck mode; A step (S13) in which the controller receives supply voltage, current, and time information from a voltage sensor, a current sensor, and a timer configured in the battery in buck mode of a bidirectional isolated FDC system using a contact-type relay; The controller stores the battery supply voltage, current, and time information in the received buck mode as a data log in memory (S14); A step (S15) in which the controller turns ON the changeover relays ⑫ and ⑬ of the bidirectional isolated FDC system using contact-type relays and maintains the buck mode; A step (S16) in which the controller determines whether the self-generation voltage of the power generation system has reached a sufficient voltage, which is a command value for self-generation; When sufficient voltage is reached, the controller turns OFF changeover relays ⑫ and ⑬ of the bidirectional isolated FDC system using contact-type relays and turns ON changeover relays ⑩ and ⑪ to switch the buck mode to a boost mode (S17); A step (S18) in which the controller determines whether the current of the power generated through self-generation has reached the maximum value of a stored command value; When the maximum value of the above command value is reached, the controller receives voltage, current, and driving time information from the voltage sensor, current sensor, and timer of the output terminal during boost mode, and stores the received voltage, current, and driving time of the output terminal in memory as a data log (S19); Step (S20) in which the controller exits boost mode, turns OFF LLC, and turns OFF changeover relays ⑩ and ⑪; and A method for switching between operating modes between buck mode and boost mode using a bidirectional isolated FDC system with a contact-type relay, characterized in that the controller includes the step (S21) of storing boost mode exit information, LLC OFF information, and relay OFF information in memory and terminating.
  7. In Article 6, A method for switching between buck mode and boost mode using a bidirectional isolated FDC system with a contact-type relay, characterized in that the boost start hold time (t c ) after buck completion is 1 to 1.2 seconds.
  8. In Article 6, A method for switching between operating modes between buck mode and boost mode using a bidirectional isolated FDC system with a contact-type relay, characterized by being able to track a user-specified command value by sensing voltage, current, and time information in real time.

Description

Bidirectional isolated FDC system with contact relays for miniaturization of fuel cell system and method for switching operating modes between buck mode and boost mode using the same The present invention relates to a bidirectional isolated FDC (Fuel Cell DC-DC Converter) system with a contact-type relay for miniaturizing a fuel cell system, and a method for switching between a Buck Mode and a Boost Mode using the same. More specifically, by miniaturizing and simplifying the configuration of an FDC converter, which has a complex structure and many failure elements, the invention simplifies the system design and enables the design of the entire grid to be enhanced. Prior art related to the present invention is disclosed in Korean Registered Patent No. 10-1619572 (published May 18, 2016). FIG. 1 is a configuration diagram of a conventional method for generating injection current for a fuel cell stack and a device for executing the same, comprising a fuel cell stack (110), a first DC-DC converter (120), a second DC-DC converter (130), and a control unit (140). And in some cases, it further includes a DC-AC converter (150) and a decoupling capacitor (160). The above fuel cell stack (110) is configured such that a plurality of unit cells are arranged in a continuous sequence to generate direct current, and alternating current is applied through a decoupling capacitor (160). The alternating current applied from the fuel cell stack (110) refers to the injection current (161). The first DC-DC converter (120) steps up a DC current of a voltage corresponding to a vehicle battery to a DC current of a specific voltage. The first DC-DC converter (120) steps up a DC current with a voltage corresponding to a vehicle battery to a voltage corresponding to a DC-Link. For example, the second DC-DC converter (130) can be a step-up DC-DC converter that steps up to 100V using a 12V vehicle battery, and this DC-DC converter can be an isolation DC-DC converter for isolation from the high-voltage section (i.e., the voltage of the fuel cell stack (110) (200V to 500V)). This first DC-DC converter (120) provides a DC current of a boosted voltage to either the second DC-DC converter (130) or the DC-AC converter (150) under the control of the control unit (140). Additionally, the second DC-DC converter (130) reduces the DC current of the voltage generated by regenerative braking in the high voltage section to a DC current of a specific voltage under the control of the control unit (140) and provides it to the DC-AC converter (150). In addition, the second DC-DC converter (130) steps down the DC current of the voltage generated by regenerative braking in the high-voltage section to a voltage corresponding to the DC-Link of Fig. 1. Additionally, the second DC-DC converter (130) receives a DC current of voltage boosted by the first DC-DC converter (120) under the control of the control unit (140), boosts the DC current to a DC current of a specific voltage, and provides it to the high voltage unit. In addition, the second DC-DC converter (130) steps up the DC current of the voltage stepped up by the first DC-DC converter (120) to a voltage corresponding to the high voltage section. That is, the second DC-DC converter (130) can be a bidirectional DC-DC converter that steps down the DC current of the voltage generated by regenerative braking in the high voltage section or steps up the DC current received from the first DC-DC converter (120) according to the control of the control unit (140). The process of charging the high-voltage section's power is explained below. When braking control is executed by the brake pedal while the vehicle is driving, the motor assisting the engine's output torque enters regenerative braking to recover the deceleration energy wasted due to the braking control and supply it to the high-voltage unit. Accordingly, the power of the high-voltage section is charged, and the second DC-DC converter (130) steps down the DC current of the voltage corresponding to the high-voltage section to a DC current of a specific voltage and provides it to the DC-AC converter (150). Additionally, the control unit (140) controls the operation of either the first DC-DC converter (120) or the second DC-DC converter (130) according to the power state of the high voltage unit. In one embodiment, the control unit (140) can control the voltage of the DC current boosted by the first DC-DC converter (120) to be supplied to the second DC-DC converter (130) when the power of the high-voltage unit is below a specific power. At this time, the control unit (140) can control the second DC-DC converter (130) to increase the DC current of the voltage boosted by the first DC-DC converter (120) to a voltage corresponding to the high voltage section and provide it to the high voltage section. In another embodiment, the control unit (140) can control the output of the vehicle battery so that the first DC-DC converter (120) does not operate if the power of