KR20100051509A - Sequence control method for cold start of fuel cell-super capacitor hybrid electric vehicle - Google Patents

Abstract

PURPOSE: A sequence control method for cold start of a fuel cell-super capacitor hybrid electric vehicle is provided to enable a drive to smoothly start the vehicle even in a cold start condition using a sequence control process such as a BOP valve heater operation and a blower operation. CONSTITUTION: A sequence control method for cold start of a fuel cell-super capacitor hybrid electric vehicle comprises: a step(S1) deciding the cold start condition which is at below a set temperature on the basis of a value of a temperature sensor; a step(S2) which supplied hydrogen by operating a valve after supplying a sub battery power source to a valve heater in a cold start condition and eliminating inc of the valve; a step(S6) operating an air blower using the power source of the sub battery or the power source of a super cap and increasing a stack temperature by operating a heater when a stack voltage is arrived to a set voltage reference value; a step connecting a fuel battery main relay and charging the super cap through stack output; and a step entering to a hybrid mode using the stack output and a super cap output by connecting a super cap main relay.

Description

Sequence control method for cold start of fuel cell-super capacitor hybrid electric vehicle}

The present invention relates to a sequence control method for starting a fuel cell vehicle. More specifically, the stack can be normally output in a cold start condition of a fuel cell hybrid vehicle having a fuel cell as a main power source and a supercap as a secondary power source. It relates to a cold start sequence control method of a fuel cell hybrid vehicle that can be started by using the energy of the supercap and the auxiliary battery.

A fuel cell is a kind of power generation device that converts chemical energy of fuel into electric energy by electrochemical reaction in the fuel cell stack without converting it into heat by combustion. It can also be applied to the power supply of electrical / electronic products, especially portable devices.

As an example of such a fuel cell, a polymer electrolyte membrane fuel cell (PEMFC), which is most frequently researched as a power supply for driving a vehicle, has a membrane centered around an electrolyte membrane through which hydrogen ions move. Membrane Electrode Assembly (MEA) with a catalytic electrode layer on both sides, a gas diffusion layer (GDL) that distributes the reactants evenly and delivers the generated electrical energy. And a gasket and fastening mechanism for maintaining the airtightness and proper fastening pressure of the reactor bodies and cooling water, and a bipolar plate for moving the reactor bodies and cooling water.

Currently, as a vehicle equipped with a polymer electrolyte membrane fuel cell as described above, a high-voltage battery or a supercapacitor as a separate power source for providing power required for driving a motor in addition to a fuel cell as a main power source in a large vehicle such as a bus as well as a small vehicle ( Fuel cell-battery and fuel cell-supercap hybrid vehicles equipped with power storage means such as supercap are being developed.

In particular, fuel cell-supercap direct hybrid vehicles that do not use a power converter are being studied. Fuel cell-supercap direct hybrid vehicles have excellent fuel economy (large regenerative braking, high efficiency of the supercap itself, no power converter), It has advantages such as increased fuel cell durability and excellent control reliability (automatic power assist and auto regenerative braking).

As described above, in a hybrid vehicle directly connected to a fuel cell and a super cap, the fuel cell continuously outputs a constant electric power, and the driving is performed. If the power remains, the super cap is charged with surplus power. Mode is applied to supplement the output from the SuperCap.

On the other hand, in vehicles that use fuel cells as a main power source such as fuel cell-supercap hybrid vehicles, an auxiliary battery (eg, 12V auxiliary battery) is mounted to supply power of fuel cell accessories or electric loads.

Hereinafter, the power net configuration of the fuel cell-supercap hybrid vehicle will be described in order to help the present invention.

1 is a power net diagram of a fuel cell-supercap hybrid vehicle. The power net configuration includes a fuel cell 10 used as a main power source, a super cap 20 used as an auxiliary power source, and a driving motor 41. A motor controller connected to the output side of the fuel cell 10 and the super cap 20 as a power module for rotating and receiving a DC current therefrom to generate a three-phase PWM (Pulse Width Modulation) and to control motor driving and regenerative braking. (MCU: Motor Control Unit) (including an inverter) 40.

In such a power net configuration, a fuel cell 10 that supplies hydrogen from the hydrogen tank 9 and air from an air blower to generate electricity by an electrochemical reaction between hydrogen and oxygen in the air is used as the main power source. In addition, the driving motor 41 and the MCU 40 are directly connected to the fuel cell 10 through the main bus stage 30, and the supercap 20 is charged and charged for power assistance (power assist) and regenerative braking. It is connected to the main bus stage 30 through a device that enables direct connection, that is, Supercap Pre-Charger (SPC) 21.

In addition, the main bus terminal 30 is an auxiliary for driving the LDC (Low Voltage DCDC Converter) 50 and the BOP (Balance of Plant) driving component 52 for output conversion between high voltage and low voltage. A battery (eg, a 12V secondary battery) 51 is connected, and a fuel cell BOP (for example, an air blower, a water pump, a radiator fan, and a hydrogen recirculation) for driving the fuel cell 10 is connected. Blowers, etc.) 60 are connected to the main bus terminal 30 through a high voltage junction box 31 to facilitate starting of the fuel cell. In addition, a blocking diode 32 for preventing reverse current from flowing into the fuel cell is installed at the main bus terminal 30, and a heater 70 is connected to the output terminal of the fuel cell 10. The heater 70 serves to increase the stack temperature by heating the cooling water circulating in the stack.

The LDC 50 boosts the voltage of the auxiliary battery 51 to supply the high voltage accessory, or step-down the high voltage output of the main bus stage 30 to a low voltage to be used for charging the auxiliary battery and supplying power to the component. In addition, the high voltage junction box 31 is a device for distributing the output of the main bus terminal 30 to a motor and various accessory parts, and various relays 33 are installed to facilitate power cutoff and connection.

On the other hand, for the fuel cell-supercap hybrid vehicle as described above, the normal starting and emergency starting sequence control technology is known, but the control technology in the cold start condition is not known, it is possible to control smooth start even in bad conditions such as cold start control The method is essential.

Accordingly, an object of the present invention is to provide a control method that enables a smooth start of a fuel cell-supercap hybrid vehicle even under adverse conditions such as cold start.

In order to achieve the above object, the present invention comprises the steps of: a) determining the cold start condition below the set temperature based on the value of the temperature sensor mounted in the fuel cell system; b) supplying auxiliary battery power to the valve heater attached to the hydrogen supply measurement BOP valve in the cold start condition to remove ice in the valve, and then operating the valve to supply hydrogen; c) operating an air blower using the power supply of the auxiliary battery or the power supply of both the auxiliary battery and the supercap, and operating the heater to raise the stack temperature when the stack voltage reaches the set voltage reference value; d) disconnecting the supercap main relay when the stack temperature reaches the set temperature reference value, connecting the fuel cell main relay, and charging the supercap with the stack output; e) providing a method for controlling a cold start sequence of a fuel cell hybrid vehicle, which comprises entering a hybrid mode using a stack output and a supercap output by connecting a supercap main relay when the supercap charging is completed.

In a preferred embodiment, the step b) is characterized in that the final operation of the valve by detecting the flow of hydrogen through a flow meter on the hydrogen line after the valve operation.

Also, in the step c), when the supercap voltage is less than the set voltage reference value, the low voltage DCDC converter (LDC) is operated in boost mode to boost and supply the auxiliary battery power to drive the air blower, and the supercap voltage is higher than the set voltage reference value. The rear side is connected to the supercap main relay to drive the air blower using the power supply of both the secondary battery and the supercap.

In the step d), when the fuel cell main relay is connected, the low voltage DCDC converter connected to the auxiliary battery is operated in the buck mode to charge the auxiliary battery with the stack voltage, and the valve heating and heater operation is terminated.

Accordingly, according to the method for controlling a cold start sequence of a fuel cell hybrid vehicle according to the present invention, a BOP valve heater operation for smooth hydrogen supply, an air blower operation, a heater operation for increasing the stack temperature, fuel cell main relay connection and supercap charging, The sequence control process, such as the connection of the supercap main relay, enables the vehicle to start smoothly even in cold start conditions.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

The present invention relates to a sequence control method for cold start of a fuel cell-supercap hybrid vehicle, and a secondary battery (eg, a 12V auxiliary battery) to enable a normal output of a stack for cold start of a fuel cell-supercap hybrid vehicle. Or sequence control that can be started using the energy of the supercap is required.

To this end, two sequence controls, namely, cold start sequence control using only an auxiliary battery, can be used to raise the fuel cell of a fuel cell-supercap hybrid vehicle stored at sub-zero temperatures to an optimum operating temperature at which the vehicle can be driven. After determining whether the current voltage of the supercap together with the auxiliary battery power is sufficient to drive the air blower, a sequence control is started to connect the supercap power in parallel to enable cold start.

In the following description, various controls such as LDC operation (buck / boost), accessory drive including air blower, heater drive, valve and valve heater drive, relay drive, and the like are provided with an upper controller (eg PCU) and lower parts provided for each unit. It is performed under cooperative control between controllers (eg LDC controllers).

2 and 3 are flowcharts illustrating a process for controlling a cold start sequence according to the present invention, and FIGS. 4A to 4D are views for explaining a cold start sequence control using only an auxiliary battery as an embodiment of the present invention. 5A to 5D are diagrams for explaining cold start sequence control using an auxiliary battery and a supercap.

First, the cold start sequence control process will be described in detail for each step with reference to FIGS. 2 and 3.

1) As a first step, it is a step of determining whether to cold start (S1). Based on the value of the temperature sensor installed in the stack, if the stack temperature is cold start condition below 0 ℃, control the cold start sequence. At this time, the value of the temperature sensor for each part mounted in the fuel cell system may be comprehensively used. If it is determined that the cold start condition is below the set temperature based on the value of each temperature sensor, the cold start sequence control is performed. Of course, if it is not the cold start condition, the sequence control of normal startup is performed (S1 ').

2) As a next step, when it is determined as a cold start condition, the power of the auxiliary battery (12V auxiliary battery) is supplied to the valve heater attached to the BOP valve of the hydrogen supply measurement to remove ice inside the valve (S2).

3) Next, check the operation of the valve after operating the valve (S3). That is, as described above, power is supplied to the valve heater as well as the valve itself, and when the valve is opened, the valve operation is checked on the condition that the flow of hydrogen is detected from the flow meter on the hydrogen line.

4) According to the supercap voltage, it is determined whether to use the supercap power at the same time as the LDC (low voltage DCDC converter) boost power for starting the fuel cell. At this time, it is determined whether the supercap voltage is sufficient to drive the air blower. The supercap voltage is compared with a voltage reference value for determining that the pre-set voltage reference value, that is, the level at which the air blower can be driven (S4), is higher than the voltage reference value. In this case, it is determined that the super cap power can be used at the same time.

5) In the previous step, if the supercap voltage is lower than the voltage reference value, start using only the auxiliary battery.When cold start using only the auxiliary battery, the LDC boosts the voltage of the auxiliary battery (LDC boost operation) to operate the air blower. (S5, S6). At this time, the host controller transmits the LDC boost voltage command value to the LDC controller at a fixed value, and the LDC controller controls the boost operation of the LDC based on the command value. When the air blower operates as described above, the air is supplied to the stack to which the hydrogen is supplied, thereby driving the fuel cell.

On the other hand, if the supercap voltage is higher than the voltage reference value, the supercap power is started at the same time. In order to use the supercap power, the LDC boost voltage is matched with the supercap voltage. At this time, the LDC boost voltage command value should be transmitted to a value less than the supercap voltage for the supercap parallel connection (LDC V_ref ≤ V_Sc, where LDC V_ref is the high voltage terminal voltage command value of the LDC). When the LDC boost voltage reaches the supercap voltage, the supercap and the LDC are connected in parallel by connecting the main relay (supercap main relay) inside the supercap initial charging device (SPC) (see FIG. 4A). . In other words, the air blower is operated by supplying the output voltage of the LDC boosting the voltage of the auxiliary battery and the output voltage of the supercap in parallel, thereby operating the fuel cell (S5 ', S5 ", S6'). ).

6) Next, it is determined whether the stack voltage reaches a preset voltage reference value, that is, a voltage reference value for determining that the stack is outputting a predetermined level (S7, S7 '). Here, when the stack voltage reaches the voltage reference value, the heater is operated using the power of the stack (S8, S8 '), thereby increasing the internal temperature of the stack to a preset temperature reference value, that is, a temperature reference value at which the fuel cell rated output is possible. . The heater receives the power of the stack to generate heat to increase the stack temperature by supplying the cooling water circulating through the stack to the heating and the stack.

7) When the internal temperature of the stack reaches the temperature reference value, it is determined that the vehicle has reached the proper temperature for driving the vehicle, and then connects the fuel cell main relay (33 in FIG. 4A). If the supercap power is used together, the main relay (supercap main relay) of the supercap initial charging device 21 is first disconnected, and then the fuel cell main relay 33 is connected (S9, S9 '). S9 ", S10). That is, disconnect the supercap connected in parallel before connecting the fuel cell main relay.

8) After connecting the fuel cell main relay as described above, switch the LDC from the boost mode to the buck mode, and the LDC step-downs the stack voltage to a low voltage (12V) and then supplies it to the auxiliary battery (12V auxiliary battery). To be charged or supplied to various components (12V components) (S11).

9) Next, the power of the heater and the BOP valve heater which are connected to increase the stack temperature are cut off (S12), and supercap charging is performed using the stack power to determine whether the supercap voltage approaches the stack voltage (S13). S14).

10) When the supercap charging is completed, a main relay (supercap relay) in the supercap initial charging device 21 is connected (S15) to enter a hybrid mode (HEV mode) using a stack output and a supercap output.

The cold start sequence control process according to the present invention has been described above with reference to FIGS. 2 and 3, and will be described with reference to FIGS. 4A through 4D and FIGS. 5A through 5D.

First, as shown in FIG. 4A, power is supplied to a heater of a valve (hydrogen supply system valve) that requires operation during cold start using the auxiliary battery 51 to remove ice components. do. Next, when it is necessary to start using only the auxiliary battery 51 power source according to the supercap 20 voltage, as shown in FIG. 4B, the high voltage power source is generated by the LDC 50 and then the air blower (BOP) 60 is applied. Supply to operate the air blower, thereby supplying air to the stack. Subsequently, when the stack voltage is increased, as shown in FIG. 4C, the heater 70 is connected to increase the stack internal temperature through the output of the fuel cell 10. After that, when the stack temperature reaches an appropriate level, as shown in FIG. 4D, the fuel cell main relay 33 is connected, the heater 70 is disconnected, and the fuel cell 10 supplies the vehicle accessory power. . Subsequently, when charging of the super cap 20 is completed, a hybrid operation mode is entered.

In the following description, a case in which the auxiliary battery 51 and the supercap 20 are started using power according to the voltage of the super cap 20 will be described. First, as shown in FIG. (BOP Components) 52 removes the ice components by supplying power to the heater of the valve (hydrogen supply system valve) which must be operated during cold start. Next, as shown in FIG. 5B, the high-capacity power source is generated by the LDC 50, and then the supercaps 20 are connected in parallel. Then, the air blower uses the high-voltage power source and the supercap 20 power supply of the LDC 50. By operating 60, air is supplied to the stack. Thereafter, when the stack voltage is increased, as shown in FIG. 5C, the heater 70 is connected to increase the stack internal temperature through the output of the fuel cell 10. Subsequently, when the stack temperature reaches an appropriate level, the supercap 20 is cut off. Then, as shown in FIG. 4D, after the fuel cell main relay 33 is connected and the heater 70 is disconnected, the vehicle accessory power is supplied to the fuel cell. (10) to supply. Subsequently, when charging of the super cap 20 is completed, a hybrid operation mode is entered.

As such, according to the cold start sequence control process according to the present invention, normal hydrogen supply is performed after heating the BOP valve in the cold start condition, and then only the auxiliary battery power according to the supercap voltage as a power source for operating the air blower. After deciding whether to use the auxiliary battery power and the supercap power at the same time, operate the air blower to increase the stack voltage.If the stack voltage is increased to a certain level, the heater is connected to the fuel cell output. After the stack temperature is raised, the fuel cell main relay is connected to the supercap, and the supercap main relay is connected and the hybrid mode is entered. Thus, the fuel cell-supercap vehicle can be started smoothly even in a cold start condition.

1 is a power net diagram of a fuel cell-supercap hybrid vehicle;

2 and 3 is a flow chart showing a cold start sequence control process according to the present invention,

4A to 4D are views illustrating a cold start sequence control state using only an auxiliary battery as an embodiment of the present invention;

5a to 5d are views illustrating a cold start sequence control state using an auxiliary battery and a supercap as an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

10: fuel cell 20: super cap

21: Supercap initial charging device (SPC) 30: Main bus stage

31: high voltage junction box 40: motor controller

41: drive motor 50: LDC (low voltage DCDC converter)

51: auxiliary battery 52: BOP drive parts (BOP valve heater)

60: fuel cell accessory (air blower) 70: heater

Claims (4)

a) determining a cold start condition below a set temperature based on a value of a temperature sensor mounted in the fuel cell system; b) supplying auxiliary battery power to the valve heater attached to the hydrogen supply measurement BOP valve in the cold start condition to remove ice in the valve, and then operating the valve to supply hydrogen; c) operating an air blower using the power supply of the auxiliary battery or the power supply of both the auxiliary battery and the supercap, and operating the heater to raise the stack temperature when the stack voltage reaches the set voltage reference value; d) disconnecting the supercap main relay when the stack temperature reaches the set temperature reference value, connecting the fuel cell main relay, and charging the supercap with the stack output; e) entering the hybrid mode using the stack output and the supercap output by connecting the supercap main relay when the supercap charging is completed; Cold start sequence control method of a fuel cell hybrid vehicle comprising a. The method according to claim 1, In the step b), after the valve operation by detecting the flow of hydrogen through a flow meter on the hydrogen line, the final check operation of the fuel cell hybrid vehicle, characterized in that the valve operation. The method according to claim 1, In the step c), if the supercap voltage is less than the set voltage reference value, the low voltage DCDC converter (LDC) operates in boost mode to boost and supply the auxiliary battery power to drive the air blower. A method for controlling a cold start sequence of a fuel cell hybrid vehicle comprising connecting a supercap main relay to drive an air blower by using a secondary battery and a power supply of both supercaps. The method according to claim 1, In step d), when the fuel cell main relay is connected, the low voltage DCDC converter connected to the auxiliary battery is operated in the buck mode to charge the auxiliary battery with the stack voltage, and terminates the valve heating and heater operation. Method for controlling cold start sequence of vehicle.

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